Apache Camel - open maven repository

Apache Camel
USER GUIDE
Version 2.6.0-fuse-01-15
Copyright 2007-2011, Apache Software Foundation
Table of Contents
Table of Contents ....................................................ii
Chapter 1
Introduction........................................................... 1
Chapter 2
Quickstart.............................................................. 1
Chapter 3
Getting Started ...................................................... 7
Chapter 4
Architecture.......................................................... 18
Chapter 5
Enterprise Integration Patterns .............................33
Chapter 6
Cook Book............................................................. 38
Chapter 7
Tutorials ............................................................. 104
Chapter 8
Language Appendix............................................. 216
Chapter 9
DataFormat Appendix.......................................... 274
Chapter 10
Pattern Appendix ................................................ 344
Chapter 11
Component Appendix .......................................... 489
Index ..................................................................... 0
ii
APA CH E C AM E L
CHAPTER
1
°°°°
Introduction
Apache Camel is a powerful open source integration framework based on
known Enterprise Integration Patterns with powerful Bean Integration.
Camel lets you create the Enterprise Integration Patterns to implement
routing and mediation rules in either a Java based Domain Specific Language
(or Fluent API), via Spring based Xml Configuration files or via the Scala DSL.
This means you get smart completion of routing rules in your IDE whether in
your Java, Scala or XML editor.
Apache Camel uses URIs so that it can easily work directly with any kind of
Transport or messaging model such as HTTP, ActiveMQ, JMS, JBI, SCA, MINA
or CXF Bus API together with working with pluggable Data Format options.
Apache Camel is a small library which has minimal dependencies for easy
embedding in any Java application. Apache Camel lets you work with the
same API regardless which kind of Transport used, so learn the API once and
you will be able to interact with all the Components that is provided out-ofthe-box.
Apache Camel has powerful Bean Binding and integrated seamless with
popular frameworks such as Spring and Guice.
Apache Camel has extensive Testing support allowing you to easily unit
test your routes.
Apache Camel can be used as a routing and mediation engine for the
following projects:
• Apache ServiceMix which is the most popular and powerful
distributed open source ESB and JBI container
• Apache ActiveMQ which is the most popular and powerful open
source message broker
• Apache CXF which is a smart web services suite (JAX-WS)
• Apache MINA a networking framework
So don't get the hump, try Camel today!
C HA P TE R 1 - IN TR O D U C TIO N
1
CHAPTER
2
°°°°
Quickstart
To start using Apache Camel quickly, you can read through some simple
examples in this chapter. For readers who would like a more thorough
introduction, please skip ahead to Chapter 3.
WALK THROUGH AN EXAMPLE CODE
This mini-guide takes you through the source code of a simple example.
Camel can be configured either by using Spring or directly in Java - which
this example does.
We start with creating a CamelContext - which is a container for
Components, Routes etc:
CamelContext context = new DefaultCamelContext();
There is more than one way of adding a Component to the CamelContext.
You can add components implicitly - when we set up the routing - as we do
here for the FileComponent:
context.addRoutes(new RouteBuilder() {
public void configure() {
from("test-jms:queue:test.queue").to("file://test");
// set up a listener on the file component
from("file://test").process(new Processor() {
public void process(Exchange e) {
System.out.println("Received exchange: " + e.getIn());
}
});
}
});
or explicitly - as we do here when we add the JMS Component:
1
CH AP T E R 2 - Q U I C K S TA RT
ConnectionFactory connectionFactory = new
ActiveMQConnectionFactory("vm://localhost?broker.persistent=false");
// Note we can explicity name the component
context.addComponent("test-jms",
JmsComponent.jmsComponentAutoAcknowledge(connectionFactory));
The above works with any JMS provider. If we know we are using ActiveMQ
we can use an even simpler form using the activeMQComponent() method
while specifying the brokerURL used to connect to ActiveMQ
camelContext.addComponent("activemq",
activeMQComponent("vm://localhost?broker.persistent=false"));
In normal use, an external system would be firing messages or events
directly into Camel through one if its Components but we are going to use
the ProducerTemplate which is a really easy way for testing your
configuration:
ProducerTemplate template = context.createProducerTemplate();
Next you must start the camel context. If you are using Spring to configure
the camel context this is automatically done for you; though if you are using
a pure Java approach then you just need to call the start() method
camelContext.start();
This will start all of the configured routing rules.
So after starting the CamelContext, we can fire some objects into camel:
for (int i = 0; i < 10; i++) {
template.sendBody("test-jms:queue:test.queue", "Test Message: " + i);
}
WHAT HAPPENS?
From the ProducerTemplate - we send objects (in this case text) into the
CamelContext to the Component test-jms:queue:test.queue. These text
objects will be converted automatically into JMS Messages and posted to a
JMS Queue named test.queue. When we set up the Route, we configured the
FileComponent to listen of the test.queue.
C HA P TE R 2 - Q U IC K S TA RT
2
The File FileComponent will take messages off the Queue, and save them
to a directory named test. Every message will be saved in a file that
corresponds to its destination and message id.
Finally, we configured our own listener in the Route - to take notifications
from the FileComponent and print them out as text.
That's it!
If you have the time then use 5 more minutes to Walk through another
example that demonstrates the Spring DSL (XML based) routing.
WALK THROUGH ANOTHER EXAMPLE
Introduction
We continue the walk from Walk through an Example. This time we take a
closer look at the routing and explains a few pointers so you wont walk into a
bear trap, but can enjoy a walk after hours to the local pub for a large beer
First we take a moment to look at the Enterprise Integration Patterns that
is the base pattern catalog for integrations. In particular we focus on the
Pipes and Filters EIP pattern, that is a central pattern. This is used for: route
through a sequence of processing steps, each performing a specific function much like the Java Servlet Filters.
Pipes and filters
In this sample we want to process a message in a sequence of steps where
each steps can perform their specific function. In our example we have a JMS
queue for receiving new orders. When an order is received we need to
process it in several steps:
▪ validate
▪ register
▪ send confirm email
This can be created in a route like this:
<route>
<from uri="jms:queue:order"/>
<pipeline>
<bean ref="validateOrder"/>
<bean ref="registerOrder"/>
<bean ref="sendConfirmEmail"/>
</pipeline>
</route>
3
CH AP T E R 2 - Q U I C K S TA RT
Camel 1.4.0 change
In Camel 1.4.0, CamelTemplate has been marked as @deprecated.
ProducerTemplate should be used instead and its created from the
CamelContext itself.
ProducerTemplate template = context.createProducerTemplate();
Where as the bean ref is a reference for a spring bean id, so we define our
beans using regular Spring XML as:
<bean id="validateOrder" class="com.mycompany.MyOrderValidator"/>
Our validator bean is a plain POJO that has no dependencies to Camel what
so ever. So you can implement this POJO as you like. Camel uses rather
intelligent Bean Binding to invoke your POJO with the payload of the received
message. In this example we will not dig into this how this happens. You
should return to this topic later when you got some hands on experience with
Camel how it can easily bind routing using your existing POJO beans.
So what happens in the route above. Well when an order is received from
the JMS queue the message is routed like Pipes and Filters:
1. payload from the JMS is sent as input to the validateOrder bean
2. the output from validateOrder bean is sent as input to the registerOrder
bean
3. the output from registerOrder bean is sent as input to the
sendConfirmEmail bean
Using Camel Components
In the route lets imagine that the registration of the order has to be done by
sending data to a TCP socket that could be a big mainframe. As Camel has
many Components we will use the camel-mina component that supports TCP
connectivity. So we change the route to:
<route>
<from uri="jms:queue:order"/>
<bean ref="validateOrder"/>
<to uri="mina:tcp://mainframeip:4444?textline=true"/>
<bean ref="sendConfirmEmail"/>
</route>
C HA P TE R 2 - Q U IC K S TA RT
4
Pipeline is default
In the route above we specify pipeline but it can be omitted as its
default, so you can write the route as:
<route>
<from
<bean
<bean
<bean
</route>
uri="jms:queue:order"/>
ref="validateOrder"/>
ref="registerOrder"/>
ref="sendConfirmEmail"/>
This is commonly used not to state the pipeline.
An example where the pipeline needs to be used, is when using a
multicast and "one" of the endpoints to send to (as a logical group) is a
pipeline of other endpoints. For example.
<route>
<from uri="jms:queue:order"/>
<multicast>
<to uri="log:org.company.log.Category"/>
<pipeline>
<bean ref="validateOrder"/>
<bean ref="registerOrder"/>
<bean ref="sendConfirmEmail"/>
</pipeline>
</multicast>
</route>
The above sends the order (from jms:queue:order) to two locations at the
same time, our log component, and to the "pipeline" of beans which goes
one to the other. If you consider the opposite, sans the <pipeline>
<route>
<from uri="jms:queue:order"/>
<multicast>
<to uri="log:org.company.log.Category"/>
<bean ref="validateOrder"/>
<bean ref="registerOrder"/>
<bean ref="sendConfirmEmail"/>
</multicast>
</route>
you would see that multicast would not "flow" the message from one bean
to the next, but rather send the order to all 4 endpoints (1x log, 3x bean) in
5
CH AP T E R 2 - Q U I C K S TA RT
parallel, which is not (for this example) what we want. We need the
message to flow to the validateOrder, then to the registerOrder, then the
sendConfirmEmail so adding the pipeline, provides this facility.
What we now have in the route is a to type that can be used as a direct
replacement for the bean type. The steps is now:
1. payload from the JMS is sent as input to the validateOrder bean
2. the output from validateOrder bean is sent as text to the mainframe using
TCP
3. the output from mainframe is sent back as input to the sendConfirmEmai
bean
What to notice here is that the to is not the end of the route (the world
) in this example it's used in the middle of the Pipes and Filters. In fact we
can change the bean types to to as well:
<route>
<from uri="jms:queue:order"/>
<to uri="bean:validateOrder"/>
<to uri="mina:tcp://mainframeip:4444?textline=true"/>
<to uri="bean:sendConfirmEmail"/>
</route>
As the to is a generic type we must state in the uri scheme which component
it is. So we must write bean: for the Bean component that we are using.
Conclusion
This example was provided to demonstrate the Spring DSL (XML based) as
opposed to the pure Java DSL from the first example. And as well to point
about that the to doesn't have to be the last node in a route graph.
This example is also based on the in-only message exchange pattern.
What you must understand as well is the in-out message exchange pattern,
where the caller expects a response. We will look into this in another
example.
See also
▪ Examples
▪ Tutorials
▪ User Guide
C HA P TE R 2 - Q U IC K S TA RT
6
CHAPTER
3
°°°°
Getting Started with Apache
Camel
THE ENTERPRISE INTEGRATION PATTERNS (EIP) BOOK
The purpose of a "patterns" book is not to advocate new techniques that the
authors have invented, but rather to document existing best practices within
a particular field. By doing this, the authors of a patterns book hope to
spread knowledge of best practices and promote a vocabulary for discussing
architectural designs.
One of the most famous patterns books is Design Patterns: Elements of
Reusable Object-oriented Software by Erich Gamma, Richard Helm, Ralph
Johnson and John Vlissides, commonly known as the "Gang of Four" (GoF)
book. Since the publication of Design Patterns, many other pattern books, of
varying quality, have been written. One famous patterns book is called
Enterprise Integration Patterns: Designing, Building, and Deploying
Messaging Solutions by Gregor Hohpe and Bobby Woolf. It is common for
people to refer to this book by its initials EIP. As the subtitle of EIP suggests,
the book focuses on design patterns for asynchronous messaging systems.
The book discusses 65 patterns. Each pattern is given a textual name and
most are also given a graphical symbol, intended to be used in architectural
diagrams.
THE CAMEL PROJECT
Camel (http://activemq.apache.org/camel/) is an open-source, Java-based
project that helps the user implement many of the design patterns in the EIP
book. Because Camel implements many of the design patterns in the EIP
book, it would be a good idea for people who work with Camel to have the
EIP book as a reference.
7
CH AP T E R 3 - G E T T I N G S TA RT E D W I TH A PA C HE C A M E L
ONLINE DOCUMENTATION FOR CAMEL
The documentation is all under the Documentation category on the right-side
menu of the Camel website (also available in PDF form. Camel-related books
are also available, in particular the Camel in Action book, presently serving
as the Camel bible--it has a free Chapter One (pdf), which is highly
recommended to read to get more familiar with Camel.
A useful tip for navigating the online documentation
The breadcrumbs at the top of the online Camel documentation can help you
navigate between parent and child subsections.
For example, If you are on the "Languages" documentation page then the
left-hand side of the reddish bar contains the following links.
Apache Camel > Documentation > Architecture > Languages
As you might expect, clicking on "Apache Camel" takes you back to the home
page of the Apache Camel project, and clicking on "Documentation" takes
you to the main documentation page. You can interpret the "Architecture"
and "Languages" buttons as indicating you are in the "Languages" section of
the "Architecture" chapter. Adding browser bookmarks to pages that you
frequently reference can also save time.
ONLINE JAVADOC DOCUMENTATION
The Apache Camel website provides Javadoc documentation. It is important
to note that the Javadoc documentation is spread over several independent
Javadoc hierarchies rather than being all contained in a single Javadoc
hierarchy. In particular, there is one Javadoc hierarchy for the core APIs of
Camel, and a separate Javadoc hierarchy for each component technology
supported by Camel. For example, if you will be using Camel with ActiveMQ
and FTP then you need to look at the Javadoc hierarchies for the core API and
Spring API.
CONCEPTS AND TERMINOLOGY FUNDAMENTAL TO CAMEL
In this section some of the concepts and terminology that are fundamental to
Camel are explained. This section is not meant as a complete Camel tutorial,
but as a first step in that direction.
C H A P T E R 3 - G E T T I N G S TA RTE D WITH A PA C HE C A M E L
8
Endpoint
The term endpoint is often used when talking about inter-process
communication. For example, in client-server communication, the client is
one endpoint and the server is the other endpoint. Depending on the
context, an endpoint might refer to an address, such as a host:port pair for
TCP-based communication, or it might refer to a software entity that is
contactable at that address. For example, if somebody uses
"www.example.com:80" as an example of an endpoint, they might be
referring to the actual port at that host name (that is, an address), or they
might be referring to the web server (that is, software contactable at that
address). Often, the distinction between the address and software
contactable at that address is not an important one.
Some middleware technologies make it possible for several software entities
to be contactable at the same physical address. For example, CORBA is an
object-oriented, remote-procedure-call (RPC) middleware standard. If a
CORBA server process contains several objects then a client can
communicate with any of these objects at the same physical address
(host:port), but a client communicates with a particular object via that
object's logical address (called an IOR in CORBA terminology), which consists
of the physical address (host:port) plus an id that uniquely identifies the
object within its server process. (An IOR contains some additional information
that is not relevant to this present discussion.) When talking about CORBA,
some people may use the term "endpoint" to refer to a CORBA server's
physical address, while other people may use the term to refer to the logical
address of a single CORBA object, and other people still might use the term
to refer to any of the following:
• The physical address (host:port) of the CORBA server process
• The logical address (host:port plus id) of a CORBA object.
• The CORBA server process (a relatively heavyweight software entity)
• A CORBA object (a lightweight software entity)
Because of this, you can see that the term endpoint is ambiguous in
at least two ways. First, it is ambiguous because it might refer to an
address or to a software entity contactable at that address. Second,
it is ambiguous in the granularity of what it refers to: a heavyweight
versus lightweight software entity, or physical address versus logical
address. It is useful to understand that different people use the term
endpoint in slightly different (and hence ambiguous) ways because
Camel's usage of this term might be different to whatever meaning
you had previously associated with the term.
Camel provides out-of-the-box support for endpoints implemented
with many different communication technologies. Here are some
examples of the Camel-supported endpoint technologies.
• A JMS queue.
9
CH AP T E R 3 - G E T T I N G S TA RT E D W I TH A PA C HE C A M E L
• A web service.
• A file. A file may sound like an unlikely type of endpoint, until you
realize that in some systems one application might write information
to a file and, later, another application might read that file.
• An FTP server.
• An email address. A client can send a message to an email address,
and a server can read an incoming message from a mail server.
• A POJO (plain old Java object).
In a Camel-based application, you create (Camel wrappers around)
some endpoints and connect these endpoints with routes, which I will
discuss later in Section 4.8 ("Routes, RouteBuilders and Java DSL").
Camel defines a Java interface called Endpoint. Each Camelsupported endpoint has a class that implements this Endpoint
interface. As I discussed in Section 3.3 ("Online Javadoc
documentation"), Camel provides a separate Javadoc hierarchy for
each communications technology supported by Camel. Because of
this, you will find documentation on, say, the JmsEndpoint class in
the JMS Javadoc hierarchy, while documentation for, say, the
FtpEndpoint class is in the FTP Javadoc hierarchy.
CamelContext
A CamelContext object represents the Camel runtime system. You typically
have one CamelContext object in an application. A typical application
executes the following steps.
1. Create a CamelContext object.
2. Add endpoints – and possibly Components, which are discussed in
Section 4.5 ("Components") – to the CamelContext object.
3. Add routes to the CamelContext object to connect the endpoints.
4. Invoke the start() operation on the CamelContext object. This
starts Camel-internal threads that are used to process the sending,
receiving and processing of messages in the endpoints.
5. Eventually invoke the stop() operation on the CamelContext object.
Doing this gracefully stops all the endpoints and Camel-internal
threads.
Note that the CamelContext.start() operation does not block
indefinitely. Rather, it starts threads internal to each Component and
Endpoint and then start() returns. Conversely,
CamelContext.stop() waits for all the threads internal to each
Endpoint and Component to terminate and then stop() returns.
If you neglect to call CamelContext.start() in your application then
messages will not be processed because internal threads will not
have been created.
C H A P T E R 3 - G E T T I N G S TA RTE D WITH A PA C HE C A M E L
10
If you neglect to call CamelContext.stop() before terminating your
application then the application may terminate in an inconsistent
state. If you neglect to call CamelContext.stop() in a JUnit test then
the test may fail due to messages not having had a chance to be
fully processed.
CamelTemplate
Camel used to have a class called CamelClient, but this was renamed to be
CamelTemplate to be similar to a naming convention used in some other
open-source projects, such as the TransactionTemplate and JmsTemplate
classes in Spring.
The CamelTemplate class is a thin wrapper around the CamelContext class. It
has methods that send a Message or Exchange – both discussed in Section
4.6 ("Message and Exchange")) – to an Endpoint – discussed in Section
4.1 ("Endpoint"). This provides a way to enter messages into source
endpoints, so that the messages will move along routes – discussed in
Section 4.8 ("Routes, RouteBuilders and Java DSL") – to destination
endpoints.
The Meaning of URL, URI, URN and IRI
Some Camel methods take a parameter that is a URI string. Many people
know that a URI is "something like a URL" but do not properly understand the
relationship between URI and URL, or indeed its relationship with other
acronyms such as IRI and URN.
Most people are familiar with URLs (uniform resource locators), such as
"http://...", "ftp://...", "mailto:...". Put simply, a URL specifies the location of a
resource.
A URI (uniform resource identifier) is a URL or a URN. So, to fully understand
what URI means, you need to first understand what is a URN.
URN is an acronym for uniform resource name. There are may "unique
identifier" schemes in the world, for example, ISBNs (globally unique for
books), social security numbers (unique within a country), customer numbers
(unique within a company's customers database) and telephone numbers.
Each "unique identifier" scheme has its own notation. A URN is a wrapper for
different "unique identifier" schemes. The syntax of a URN is "urn:<schemename>:<unique-identifier>". A URN uniquely identifies a resource, such as a
book, person or piece of equipment. By itself, a URN does not specify the
location of the resource. Instead, it is assumed that a registry provides a
mapping from a resource's URN to its location. The URN specification does
not state what form a registry takes, but it might be a database, a server
application, a wall chart or anything else that is convenient. Some
11
CH AP T E R 3 - G E T T I N G S TA RT E D W I TH A PA C HE C A M E L
hypothetical examples of URNs are "urn:employee:08765245",
"urn:customer:uk:3458:hul8" and "urn:foo:0000-0000-9E59-0000-5E-2". The
<scheme-name> ("employee", "customer" and "foo" in these examples) part
of a URN implicitly defines how to parse and interpret the <uniqueidentifier> that follows it. An arbitrary URN is meaningless unless: (1) you
know the semantics implied by the <scheme-name>, and (2) you have
access to the registry appropriate for the <scheme-name>. A registry does
not have to be public or globally accessible. For example,
"urn:employee:08765245" might be meaningful only within a specific
company.
To date, URNs are not (yet) as popular as URLs. For this reason, URI is widely
misused as a synonym for URL.
IRI is an acronym for internationalized resource identifier. An IRI is simply an
internationalized version of a URI. In particular, a URI can contain letters and
digits in the US-ASCII character set, while a IRI can contain those same
letters and digits, and also European accented characters, Greek letters,
Chinese ideograms and so on.
Components
Component is confusing terminology; EndpointFactory would have been
more appropriate because a Component is a factory for creating Endpoint
instances. For example, if a Camel-based application uses several JMS
queues then the application will create one instance of the JmsComponent
class (which implements the Component interface), and then the application
invokes the createEndpoint() operation on this JmsComponent object
several times. Each invocation of JmsComponent.createEndpoint() creates
an instance of the JmsEndpoint class (which implements the Endpoint
interface). Actually, application-level code does not invoke
Component.createEndpoint() directly. Instead, application-level code
normally invokes CamelContext.getEndpoint(); internally, the
CamelContext object finds the desired Component object (as I will discuss
shortly) and then invokes createEndpoint() on it.
Consider the following code.
myCamelContext.getEndpoint("pop3://john.smith@mailserv.example.com?password=myPassword");
The parameter to getEndpoint() is a URI. The URI prefix (that is, the part
before ":") specifies the name of a component. Internally, the CamelContext
object maintains a mapping from names of components to Component
objects. For the URI given in the above example, the CamelContext object
would probably map the pop3 prefix to an instance of the MailComponent
class. Then the CamelContext object invokes
C H A P T E R 3 - G E T T I N G S TA RTE D WITH A PA C HE C A M E L
12
createEndpoint("pop3://john.smith@mailserv.example.com?password=myPassword"
on that MailComponent object. The createEndpoint() operation splits the
URI into its component parts and uses these parts to create and configure an
Endpoint object.
In the previous paragraph, I mentioned that a CamelContext object
maintains a mapping from component names to Component objects. This
raises the question of how this map is populated with named Component
objects. There are two ways of populating the map. The first way is for
application-level code to invoke CamelContext.addComponent(String
componentName, Component component). The example below shows a
single MailComponent object being registered in the map under 3 different
names.
Component mailComponent = new org.apache.camel.component.mail.MailComponent();
myCamelContext.addComponent("pop3", mailComponent);
myCamelContext.addComponent("imap", mailComponent);
myCamelContext.addComponent("smtp", mailComponent);
The second (and preferred) way to populate the map of named Component
objects in the CamelContext object is to let the CamelContext object perform
lazy initialization. This approach relies on developers following a convention
when they write a class that implements the Component interface. I illustrate
the convention by an example. Let's assume you write a class called
com.example.myproject.FooComponent and you want Camel to
automatically recognize this by the name "foo". To do this, you have to write
a properties file called "META-INF/services/org/apache/camel/component/foo"
(without a ".properties" file extension) that has a single entry in it called
class, the value of which is the fully-scoped name of your class. This is
shown below.
Listing 1. META-INF/services/org/apache/camel/component/foo
class=com.example.myproject.FooComponent
If you want Camel to also recognize the class by the name "bar" then you
write another properties file in the same directory called "bar" that has the
same contents. Once you have written the properties file(s), you create a jar
file that contains the com.example.myproject.FooComponent class and the
properties file(s), and you add this jar file to your CLASSPATH. Then, when
application-level code invokes createEndpoint("foo:...") on a
CamelContext object, Camel will find the "foo"" properties file on the
CLASSPATH, get the value of the class property from that properties file, and
use reflection APIs to create an instance of the specified class.
As I said in Section 4.1 ("Endpoint"), Camel provides out-of-the-box support
for numerous communication technologies. The out-of-the-box support
13
CH AP T E R 3 - G E T T I N G S TA RT E D W I TH A PA C HE C A M E L
consists of classes that implement the Component interface plus properties
files that enable a CamelContext object to populate its map of named
Component objects.
Earlier in this section I gave the following example of calling
CamelContext.getEndpoint().
myCamelContext.getEndpoint("pop3://john.smith@mailserv.example.com?password=myPassword");
When I originally gave that example, I said that the parameter to
getEndpoint() was a URI. I said that because the online Camel
documentation and the Camel source code both claim the parameter is a
URI. In reality, the parameter is restricted to being a URL. This is because
when Camel extracts the component name from the parameter, it looks for
the first ":", which is a simplistic algorithm. To understand why, recall from
Section 4.4 ("The Meaning of URL, URI, URN and IRI") that a URI can be a URL
or a URN. Now consider the following calls to getEndpoint.
myCamelContext.getEndpoint("pop3:...");
myCamelContext.getEndpoint("jms:...");
myCamelContext.getEndpoint("urn:foo:...");
myCamelContext.getEndpoint("urn:bar:...");
Camel identifies the components in the above example as "pop3", "jms",
"urn" and "urn". It would be more useful if the latter components were
identified as "urn:foo" and "urn:bar" or, alternatively, as "foo" and "bar" (that
is, by skipping over the "urn:" prefix). So, in practice you must identify an
endpoint with a URL (a string of the form "<scheme>:...") rather than with a
URN (a string of the form "urn:<scheme>:..."). This lack of proper support for
URNs means the you should consider the parameter to getEndpoint() as
being a URL rather than (as claimed) a URI.
Message and Exchange
The Message interface provides an abstraction for a single message, such as
a request, reply or exception message.
There are concrete classes that implement the Message interface for each
Camel-supported communications technology. For example, the JmsMessage
class provides a JMS-specific implementation of the Message interface. The
public API of the Message interface provides get- and set-style methods to
access the message id, body and individual header fields of a messge.
The Exchange interface provides an abstraction for an exchange of
messages, that is, a request message and its corresponding reply or
exception message. In Camel terminology, the request, reply and exception
messages are called in, out and fault messages.
C H A P T E R 3 - G E T T I N G S TA RTE D WITH A PA C HE C A M E L
14
There are concrete classes that implement the Exchange interface for each
Camel-supported communications technology. For example, the JmsExchange
class provides a JMS-specific implementation of the Exchange interface. The
public API of the Exchange interface is quite limited. This is intentional, and it
is expected that each class that implements this interface will provide its
own technology-specific operations.
Application-level programmers rarely access the Exchange interface (or
classes that implement it) directly. However, many classes in Camel are
generic types that are instantiated on (a class that implements) Exchange.
Because of this, the Exchange interface appears a lot in the generic
signatures of classes and methods.
Processor
The Processor interface represents a class that processes a message. The
signature of this interface is shown below.
Listing 2. Processor
package org.apache.camel;
public interface Processor {
void process(Exchange exchange) throws Exception;
}
Notice that the parameter to the process() method is an Exchange rather
than a Message. This provides flexibility. For example, an implementation of
this method initially might call exchange.getIn() to get the input message
and process it. If an error occurs during processing then the method can call
exchange.setException().
An application-level developer might implement the Processor interface
with a class that executes some business logic. However, there are many
classes in the Camel library that implement the Processor interface in a way
that provides support for a design pattern in the EIP book. For example,
ChoiceProcessor implements the message router pattern, that is, it uses a
cascading if-then-else statement to route a message from an input queue to
one of several output queues. Another example is the FilterProcessor
class which discards messages that do not satisfy a stated predicate (that is,
condition).
Routes, RouteBuilders and Java DSL
A route is the step-by-step movement of a Message from an input queue,
through arbitrary types of decision making (such as filters and routers) to a
destination queue (if any). Camel provides two ways for an application
developer to specify routes. One way is to specify route information in an
15
CH AP T E R 3 - G E T T I N G S TA RT E D W I TH A PA C HE C A M E L
XML file. A discussion of that approach is outside the scope of this document.
The other way is through what Camel calls a Java DSL (domain-specific
language).
Introduction to Java DSL
For many people, the term "domain-specific language" implies a compiler or
interpreter that can process an input file containing keywords and syntax
specific to a particular domain. This is not the approach taken by Camel.
Camel documentation consistently uses the term "Java DSL" instead of
"DSL", but this does not entirely avoid potential confusion. The Camel "Java
DSL" is a class library that can be used in a way that looks almost like a DSL,
except that it has a bit of Java syntactic baggage. You can see this in the
example below. Comments afterwards explain some of the constructs used in
the example.
Listing 3. Example of Camel's "Java DSL"
RouteBuilder builder = new RouteBuilder() {
public void configure() {
from("queue:a").filter(header("foo").isEqualTo("bar")).to("queue:b");
from("queue:c").choice()
.when(header("foo").isEqualTo("bar")).to("queue:d")
.when(header("foo").isEqualTo("cheese")).to("queue:e")
.otherwise().to("queue:f");
}
};
CamelContext myCamelContext = new DefaultCamelContext();
myCamelContext.addRoutes(builder);
The first line in the above example creates an object which is an instance of
an anonymous subclass of RouteBuilder with the specified configure()
method.
The CamelContext.addRoutes(RouterBuilder builder) method invokes
builder.setContext(this) – so the RouteBuilder object knows which
CamelContext object it is associated with – and then invokes
builder.configure(). The body of configure() invokes methods such as
from(), filter(), choice(), when(), isEqualTo(), otherwise() and to().
The RouteBuilder.from(String uri) method invokes getEndpoint(uri)
on the CamelContext associated with the RouteBuilder object to get the
specified Endpoint and then puts a FromBuilder "wrapper" around this
Endpoint. The FromBuilder.filter(Predicate predicate) method
creates a FilterProcessor object for the Predicate (that is, condition)
object built from the header("foo").isEqualTo("bar") expression. In this
way, these operations incrementally build up a Route object (with a
C H A P T E R 3 - G E T T I N G S TA RTE D WITH A PA C HE C A M E L
16
RouteBuilder wrapper around it) and add it to the CamelContext object
associated with the RouteBuilder.
Critique of Java DSL
The online Camel documentation compares Java DSL favourably against the
alternative of configuring routes and endpoints in a XML-based Spring
configuration file. In particular, Java DSL is less verbose than its XML
counterpart. In addition, many integrated development environments (IDEs)
provide an auto-completion feature in their editors. This auto-completion
feature works with Java DSL, thereby making it easier for developers to write
Java DSL.
However, there is another option that the Camel documentation neglects to
consider: that of writing a parser that can process DSL stored in, say, an
external file. Currently, Camel does not provide such a DSL parser, and I do
not know if it is on the "to do" list of the Camel maintainers. I think that a
DSL parser would offer a significant benefit over the current Java DSL. In
particular, the DSL would have a syntactic definition that could be expressed
in a relatively short BNF form. The effort required by a Camel user to learn
how to use DSL by reading this BNF would almost certainly be significantly
less than the effort currently required to study the API of the RouterBuilder
classes.
Continue Learning about Camel
Return to the main Getting Started page for additional introductory reference
information.
17
CH AP T E R 3 - G E T T I N G S TA RT E D W I TH A PA C HE C A M E L
CHAPTER
4
°°°°
Architecture
Camel uses a Java based Routing Domain Specific Language (DSL) or an Xml
Configuration to configure routing and mediation rules which are added to a
CamelContext to implement the various Enterprise Integration Patterns.
At a high level Camel consists of a CamelContext which contains a
collection of Component instances. A Component is essentially a factory of
Endpoint instances. You can explicitly configure Component instances in Java
code or an IoC container like Spring or Guice, or they can be auto-discovered
using URIs.
An Endpoint acts rather like a URI or URL in a web application or a
Destination in a JMS system; you can communicate with an endpoint; either
sending messages to it or consuming messages from it. You can then create
a Producer or Consumer on an Endpoint to exchange messages with it.
The DSL makes heavy use of pluggable Languages to create an Expression
or Predicate to make a truly powerful DSL which is extensible to the most
suitable language depending on your needs. The following languages are
supported
• Bean Language for using Java for expressions
• Constant
• the unified EL from JSP and JSF
• Header
• JXPath
• Mvel
• OGNL
• Property
• Scala DSL
• Scripting Languages such as
◦ BeanShell
◦ JavaScript
◦ Groovy
◦ Python
◦ PHP
◦ Ruby
• Simple
◦ File Language
C HA P TE R 4 - A R C HITE C T U R E
18
• Spring Expression Language
• SQL
• XPath
• XQuery
Most of these languages is also supported used as Annotation Based
Expression Language.
For a full details of the individual languages see the Language Appendix
URIS
Camel makes extensive use of URIs to allow you to refer to endpoints which
are lazily created by a Component if you refer to them within Routes
Current Supported URIs
Component / ArtifactId / URI
Description
ActiveMQ / activemq-camel
activemq:[topic:]destinationName
ActiveMQ Journal / activemq-core
activemq.journal:directory-on-filesystem
For JMS Messaging with
Apache ActiveMQ
Uses ActiveMQ's fast disk
journaling implementation
to store message bodies in a
rolling log file
AMQP / camel-amqp
amqp:[topic:]destinationName
Atom / camel-atom
atom:uri
AWS-SNS / camel-aws
aws-sns://topicname[?options]
19
CH AP T E R 4 - A R C H I T E C T U R E
For Messaging with AMQP
protocol
Working with Apache
Abdera for atom integration,
such as consuming an atom
feed.
For Messaging with
Amazon's Simple
Notification Service (SNS).
AWS-SQS / camel-aws
aws-sqs://queuename[?options]
For Messaging with
Amazon's Simple Queue
Service (SQS).
AWS-S3 / camel-aws
aws-s3://bucketname[?options]
Bean / camel-core
bean:beanName[?method=someMethod]
Bean Validation / camel-bean-validator
bean-validator:something
Browse / camel-core
browse:someName
Cache / camel-cache
cache://cachename[?options]
Class / camel-core
class:className[?method=someMethod]
For working with Amazon's
Simple Storage Service (S3).
Uses the Bean Binding to
bind message exchanges to
beans in the Registry. Is also
used for exposing and
invoking POJO (Plain Old
Java Objects).
Validates the payload of a
message using the Java
Validation API (JSR 303 and
JAXP Validation) and its
reference implementation
Hibernate Validator
Provides a simple
BrowsableEndpoint which
can be useful for testing,
visualisation tools or
debugging. The exchanges
sent to the endpoint are all
available to be browsed.
The cache component
facilitates creation of
caching endpoints and
processors using EHCache
as the cache
implementation.
Uses the Bean Binding to
bind message exchanges to
beans in the Registry. Is also
used for exposing and
invoking POJO (Plain Old
Java Objects).
C HA P TE R 4 - A R C HITE C T U R E
20
Cometd / camel-cometd
cometd://host:port/channelname
Context / camel-context
context:camelContextId:localEndpointName
Crypto (Digital Signatures) / camel-crypto
crypto:sign:name[?options]
crypto:verify:name[?options]
Used to deliver messages
using the jetty cometd
implementation of the
bayeux protocol
Used to refer to endpoints
within a separate
CamelContext to provide a
simple black box
composition approach so
that routes can be combined
into a CamelContext and
then used as a black box
component inside other
routes in other
CamelContexts
Used to sign and verify
exchanges using the
Signature Service of the
Java Cryptographic
Extension.
CXF / camel-cxf
cxf:address[?serviceClass=...]
CXF Bean / camel-cxf
cxf:bean name
CXFRS / camel-cxf
cxfrs:address[?resourcesClasses=...]
21
CH AP T E R 4 - A R C H I T E C T U R E
Working with Apache CXF
for web services integration
Proceess the exchange
using a JAX WS or JAX RS
annotated bean from the
registry. Requires less
configuration than the
above CXF Component
Working with Apache CXF
for REST services
integration
DataSet / camel-core
dataset:name
Db4o / camel-db4o in camel-extra
db4o://className
For load & soak testing the
DataSet provides a way to
create huge numbers of
messages for sending to
Components or asserting
that they are consumed
correctly
For using a db4o datastore
as a queue via the db4o
library
Direct / camel-core
direct:name
DNS / camel-dns
dns:operation
EJB / camel-ejb
ejb:ejbName[?method=someMethod]
Esper / camel-esper in camel-extra
esper:name
Synchronous call to another
endpoint
To lookup domain
information and run DNS
queries using DNSJava
Uses the Bean Binding to
bind message exchanges to
EJBs. It works like the Bean
component but just for
accessing EJBs. Supports EJB
3.0 onwards.
Working with the Esper
Library for Event Stream
Processing
Event / camel-spring
event://default
spring-event://default
Working with Spring
ApplicationEvents
EventAdmin / camel-eventadmin
eventadmin:topic
Receiving OSGi EventAdmin
events
C HA P TE R 4 - A R C HITE C T U R E
22
Exec / camel-exec
exec://executable[?options]
File / camel-core
file://nameOfFileOrDirectory
Flatpack / camel-flatpack
flatpack:[fixed|delim]:configFile
For executing system
commands
Sending messages to a file
or polling a file or directory.
Camel 1.x use this link
File.
Processing fixed width or
delimited files or messages
using the FlatPack library
FreeMarker / camel-freemarker
freemarker:someTemplateResource
FTP / camel-ftp
ftp://host[:port]/fileName
FTPS / camel-ftp
ftps://host[:port]/fileName
GAuth / camel-gae
gauth://name[?options]
GHttp / camel-gae
ghttp://hostname[:port][/path][?options]
ghttp:///path[?options]
23
CH AP T E R 4 - A R C H I T E C T U R E
Generates a response using
a FreeMarker template
Sending and receiving files
over FTP. Camel 1.x use
this link FTP.
Sending and receiving files
over FTP Secure (TLS and
SSL).
Used by web applications to
implement an OAuth
consumer. See also Camel
Components for Google App
Engine.
Provides connectivity to the
URL fetch service of Google
App Engine but can also be
used to receive messages
from servlets. See also
Camel Components for
Google App Engine.
GLogin / camel-gae
glogin://hostname[:port][?options]
GTask / camel-gae
gtask://queue-name
GMail / camel-gae
gmail://user@gmail.com[?options]
gmail://user@googlemail.com[?options]
Hazelcast / camel-hazelcast
hazelcast://[type]:cachename[?options]
Used by Camel applications
outside Google App Engine
(GAE) for programmatic
login to GAE applications.
See also Camel Components
for Google App Engine.
Supports asynchronous
message processing on
Google App Engine by using
the task queueing service as
message queue. See also
Camel Components for
Google App Engine.
Supports sending of emails
via the mail service of
Google App Engine. See also
Camel Components for
Google App Engine.
Hazelcast is a data grid
entirely implemented in Java
(single jar). This component
supports map, multimap,
seda, queue, set, atomic
number and simple cluster
support.
HDFS / camel-hdfs in camel-hdfs
hdfs://path[?options]
Hibernate / camel-hibernate in camel-extra
hibernate://entityName
HL7 / camel-hl7
mina:tcp://hostname[:port]
For reading/writing from/to
an HDFS filesystem
For using a database as a
queue via the Hibernate
library
For working with the HL7
MLLP protocol and the HL7
model using the HAPI library
C HA P TE R 4 - A R C HITE C T U R E
24
HTTP / camel-http
http://hostname[:port]
HTTP4 / camel-http4
http4://hostname[:port]
iBATIS / camel-ibatis
ibatis://statementName
For calling out to external
HTTP servers using Apache
HTTP Client 3.x
For calling out to external
HTTP servers using Apache
HTTP Client 4.x
Performs a query, poll,
insert, update or delete in a
relational database using
Apache iBATIS
IMap / camel-mail
imap://hostname[:port]
Receiving email using IMap
IRC / camel-irc
irc:host[:port]/#room
JavaSpace / camel-javaspace
javaspace:jini://host?spaceName=mySpace?...
JBI / servicemix-camel
jbi:serviceName
JCR / camel-jcr
jcr://user:password@repository/path/to/node
For IRC communication
Sending and receiving
messages through
JavaSpace
For JBI integration such as
working with Apache
ServiceMix
Storing a message in a JCR
(JSR-170) compliant
repository like Apache
Jackrabbit
JDBC / camel-jdbc
jdbc:dataSourceName?options
25
CH AP T E R 4 - A R C H I T E C T U R E
For performing JDBC queries
and operations
Jetty / camel-jetty
jetty:url
For exposing services over
HTTP
JMS / camel-jms
jms:[topic:]destinationName
Working with JMS providers
JMX / camel-jmx
jmx://platform?options
JPA / camel-jpa
jpa://entityName
JT/400 / camel-jt400
jt400://user:pwd@system/<path_to_dtaq>
Kestrel / camel-kestrel
kestrel://[addresslist/]queuename[?options]
For working with JMX
notification listeners
For using a database as a
queue via the JPA
specification for working
with OpenJPA, Hibernate or
TopLink
For integrating with data
queues on an AS/400 (aka
System i, IBM i, i5, ...)
system
For producing to or
consuming from Kestrel
queues
Language / camel-core
language://languageName[:script][?options]
LDAP / camel-ldap
ldap:host[:port]?base=...[&scope=<scope>]
Log / camel-core
log:loggingCategory[?level=ERROR]
Executes Languages scripts
Performing searches on
LDAP servers (<scope>
must be one of
object|onelevel|subtree)
Uses Jakarta Commons
Logging to log the message
exchange to some
underlying logging system
like log4j
C HA P TE R 4 - A R C HITE C T U R E
26
Lucene / camel-lucene
lucene:searcherName:insert[?analyzer=<analyzer>]
lucene:searcherName:query[?analyzer=<analyzer>]
Uses Apache Lucene to
perform Java-based indexing
and full text based searches
using advanced analysis/
tokenization capabilities
Mail / camel-mail
mail://user-info@host:port
Sending and receiving email
MINA / camel-mina
[tcp|udp|vm]:host[:port]
Working with Apache MINA
Mock / camel-core
mock:name
MSV / camel-msv
msv:someLocalOrRemoteResource
MyBatis / camel-mybatis
mybatis://statementName
For testing routes and
mediation rules using mocks
Validates the payload of a
message using the MSV
Library
Performs a query, poll,
insert, update or delete in a
relational database using
MyBatis
Nagios / camel-nagios
nagios://host[:port]?options
Netty / camel-netty
netty:tcp//host[:port]?options
netty:udp//host[:port]?options
NMR / servicemix-nmr
nmr://serviceName
27
CH AP T E R 4 - A R C H I T E C T U R E
Sending passive checks to
Nagios using JSendNSCA
Working with TCP and UDP
protocols using Java NIO
based capabilities offered by
the JBoss Netty community
project
Integration with the
Normalized Message Router
BUS in ServiceMix 4.x
Pax-Logging / camel-paxlogging
paxlogging:appender
Receiving Pax-Logging
events in OSGi
POP / camel-mail
pop3://user-info@host:port
Printer / camel-printer
lpr://host:port/path/to/printer[?options]
Properties / camel-core
properties://key[?options]
Quartz / camel-quartz
quartz://groupName/timerName
Quickfix / camel-quickfix
quickfix-server:config file
quickfix-client:config-file
Ref / camel-core
ref:name
Restlet / camel-restlet
restlet:restletUrl[?options]
Receiving email using POP3
and JavaMail
The printer component
facilitates creation of printer
endpoints to local, remote
and wireless printers. The
endpoints provide the ability
to print camel directed
payloads when utilized on
camel routes.
The properties component
facilitates using property
placeholders directly in
endpoint uri definitions.
Provides a scheduled
delivery of messages using
the Quartz scheduler
Implementation of the
QuickFix for Java engine
which allow to send/receive
FIX messages
Component for lookup of
existing endpoints bound in
the Registry.
Component for consuming
and producing Restful
resources using Restlet
C HA P TE R 4 - A R C HITE C T U R E
28
RMI / camel-rmi
rmi://host[:port]
RNC / camel-jing
rnc:/relativeOrAbsoluteUri
Working with RMI
Validates the payload of a
message using RelaxNG
Compact Syntax
RNG / camel-jing
rng:/relativeOrAbsoluteUri
Routebox / camel-routebox
routebox:routeboxName[?options]
RSS / camel-rss
rss:uri
Scalate / scalate-camel
scalate:templateName
SEDA / camel-core
seda:name
SERVLET / camel-servlet
servlet:uri
29
CH AP T E R 4 - A R C H I T E C T U R E
Validates the payload of a
message using RelaxNG
Facilitates the creation of
specialized endpoints that
offer encapsulation and a
strategy/map based
indirection service to a
collection of camel routes
hosted in an automatically
created or user injected
camel context
Working with ROME for RSS
integration, such as
consuming an RSS feed.
Uses the given Scalate
template to transform the
message
Asynchronous call to
another endpoint in the
same Camel Context
For exposing services over
HTTP through the servlet
which is deployed into the
Web container.
SFTP / camel-ftp
sftp://host[:port]/fileName
Sip / camel-sip
sip://user@host[:port]?[options]
sips://user@host[:port]?[options]
Smooks / camel-smooks in camel-extra.
unmarshal(edi)
Sending and receiving files
over SFTP (FTP over SSH).
Camel 1.x use this link
FTP.
Publish/Subscribe
communication capability
using the Telecom SIP
protocol. RFC3903 - Session
Initiation Protocol (SIP)
Extension for Event
For working with EDI parsing
using the Smooks library.
This component is
deprecated as Smooks
now provides Camel
integration out of the box.
SMTP / camel-mail
smtp://user-info@host[:port]
SMPP / camel-smpp
smpp://user-info@host[:port]?options
SNMP / camel-snmp
snmp://host[:port]?options
SpringIntegration / camel-spring-integration
spring-integration:defaultChannelName
Spring Web Services / camel-spring-ws
spring-ws:[mapping-type:]address[?options]
Sending email using SMTP
and JavaMail
To send and receive SMS
using Short Messaging
Service Center using the
JSMPP library
Polling OID values and
receiving traps using SNMP
via SNMP4J library
The bridge component of
Camel and Spring
Integration
Client-side support for
accessing web services, and
server-side support for
creating your own contractfirst web services using
Spring Web Services
C HA P TE R 4 - A R C HITE C T U R E
30
SQL / camel-sql
sql:select * from table where id=#
Stream / camel-stream
stream:[in|out|err|file]
Performing SQL queries
using JDBC
Read or write to an input/
output/error/file stream
rather like unix pipes
StringTemplate / camel-stringtemplate
string-template:someTemplateResource
Generates a response using
a String Template
TCP / camel-mina
mina:tcp://host:port
Test / camel-spring
test:expectedMessagesEndpointUri
Working with TCP protocols
using Apache MINA
Creates a Mock endpoint
which expects to receive all
the message bodies that
could be polled from the
given underlying endpoint
Timer / camel-core
timer://name
A timer endpoint
UDP / camel-mina
mina:udp://host:port
Validation / camel-spring
validation:someLocalOrRemoteResource
Working with UDP protocols
using Apache MINA
Validates the payload of a
message using XML Schema
and JAXP Validation
Velocity / camel-velocity
velocity:someTemplateResource
31
CH AP T E R 4 - A R C H I T E C T U R E
Generates a response using
an Apache Velocity template
VM / camel-core
vm:name
Asynchronous call to
another endpoint in the
same JVM
XMPP / camel-xmpp
xmpp://host:port/room
Working with XMPP and
Jabber
XQuery / camel-saxon
xquery:someXQueryResource
Generates a response using
an XQuery template
XSLT / camel-spring
xslt:someTemplateResource
Generates a response using
an XSLT template
For a full details of the individual components see the Component Appendix
C HA P TE R 4 - A R C HITE C T U R E
32
CHAPTER
5
°°°°
Enterprise Integration
Patterns
Camel supports most of the Enterprise Integration Patterns from the
excellent book of the same name by Gregor Hohpe and Bobby Woolf. Its a
highly recommended book, particularly for users of Camel.
PATTERN INDEX
There now follows a list of the Enterprise Integration Patterns from the book
along with examples of the various patterns using Apache Camel
Messaging Systems
33
Message
Channel
How does one application communicate with
another using messaging?
Message
How can two applications connected by a message
channel exchange a piece of information?
Pipes and
Filters
How can we perform complex processing on a
message while maintaining independence and
flexibility?
Message
Router
How can you decouple individual processing steps
so that messages can be passed to different filters
depending on a set of conditions?
Message
Translator
How can systems using different data formats
communicate with each other using messaging?
Message
Endpoint
How does an application connect to a messaging
channel to send and receive messages?
CH AP T E R 5 - E N T E R P R I S E I N T E G R ATIO N PAT TE R N S
Messaging Channels
Point to
Point
Channel
How can the caller be sure that exactly one
receiver will receive the document or perform the
call?
Publish
Subscribe
Channel
How can the sender broadcast an event to all
interested receivers?
Dead Letter
Channel
What will the messaging system do with a
message it cannot deliver?
Guaranteed
Delivery
How can the sender make sure that a message
will be delivered, even if the messaging system
fails?
Message
Bus
What is an architecture that enables separate
applications to work together, but in a de-coupled
fashion such that applications can be easily added
or removed without affecting the others?
Message Construction
Event
Message
How can messaging be used to transmit events
from one application to another?
Request
Reply
When an application sends a message, how can it
get a response from the receiver?
Correlation
Identifier
How does a requestor that has received a reply
know which request this is the reply for?
Return
Address
How does a replier know where to send the reply?
Message Routing
Content
Based
Router
How do we handle a situation where the
implementation of a single logical function (e.g.,
inventory check) is spread across multiple
physical systems?
Message
Filter
How can a component avoid receiving
uninteresting messages?
C HA P T E R 5 - E N T E R PR ISE IN TE GR ATIO N PAT TE R N S
34
35
Dynamic
Router
How can you avoid the dependency of the
router on all possible destinations while
maintaining its efficiency?
Recipient
List
How do we route a message to a list of (static or
dynamically) specified recipients?
Splitter
How can we process a message if it contains
multiple elements, each of which may have to
be processed in a different way?
Aggregator
How do we combine the results of individual,
but related messages so that they can be
processed as a whole?
Resequencer
How can we get a stream of related but out-ofsequence messages back into the correct order?
Composed
Message
Processor
How can you maintain the overall message flow
when processing a message consisting of
multiple elements, each of which may require
different processing?
ScatterGather
How do you maintain the overall message flow
when a message needs to be sent to multiple
recipients, each of which may send a reply?
Routing Slip
How do we route a message consecutively
through a series of processing steps when the
sequence of steps is not known at design-time
and may vary for each message?
Throttler
How can I throttle messages to ensure that a
specific endpoint does not get overloaded, or
we don't exceed an agreed SLA with some
external service?
Sampling
How can I sample one message out of many in a
given period to avoid downstream route does
not get overloaded?
Delayer
How can I delay the sending of a message?
Load
Balancer
How can I balance load across a number of
endpoints?
Multicast
How can I route a message to a number of
endpoints at the same time?
CH AP T E R 5 - E N T E R P R I S E I N T E G R ATIO N PAT TE R N S
How can I repeat processing a message in a
loop?
Loop
Message Transformation
Content
Enricher
How do we communicate with another system if
the message originator does not have all the
required data items available?
Content
Filter
How do you simplify dealing with a large message,
when you are interested only in a few data items?
Claim
Check
How can we reduce the data volume of message
sent across the system without sacrificing
information content?
Normalizer
How do you process messages that are
semantically equivalent, but arrive in a different
format?
Sort
How can I sort the body of a message?
Validate
How can I validate a message?
Messaging Endpoints
Messaging
Mapper
How do you move data between domain objects
and the messaging infrastructure while keeping
the two independent of each other?
Event Driven
Consumer
How can an application automatically consume
messages as they become available?
Polling
Consumer
How can an application consume a message
when the application is ready?
Competing
Consumers
How can a messaging client process multiple
messages concurrently?
Message
Dispatcher
How can multiple consumers on a single channel
coordinate their message processing?
Selective
Consumer
How can a message consumer select which
messages it wishes to receive?
Durable
Subscriber
How can a subscriber avoid missing messages
while it's not listening for them?
C HA P T E R 5 - E N T E R PR ISE IN TE GR ATIO N PAT TE R N S
36
Idempotent
Consumer
How can a message receiver deal with duplicate
messages?
Transactional
Client
How can a client control its transactions with the
messaging system?
Messaging
Gateway
How do you encapsulate access to the
messaging system from the rest of the
application?
Service
Activator
How can an application design a service to be
invoked both via various messaging technologies
and via non-messaging techniques?
System Management
Detour
How can you route a message through intermediate
steps to perform validation, testing or debugging
functions?
Wire
Tap
How do you inspect messages that travel on a point-topoint channel?
Log
How can I log processing a message?
For a full breakdown of each pattern see the Book Pattern Appendix
37
CH AP T E R 5 - E N T E R P R I S E I N T E G R ATIO N PAT TE R N S
CookBook
This document describes various recipes for working with Camel
• Bean Integration describes how to work with beans and Camel in a
loosely coupled way so that your beans do not have to depend on
any Camel APIs
◦ Annotation Based Expression Language binds expressions to
method parameters
◦ Bean Binding defines which methods are invoked and how
the Message is converted into the parameters of the method
when it is invoked
◦ Bean Injection for injecting Camel related resources into your
POJOs
◦ Parameter Binding Annotations for extracting various
headers, properties or payloads from a Message
◦ POJO Consuming for consuming and possibly routing
messages from Camel
◦ POJO Producing for producing camel messages from your
POJOs
◦ RecipientList Annotation for creating a Recipient List from a
POJO method
◦ Using Exchange Pattern Annotations describes how pattern
annotations can be used to change the behaviour of method
invocations
• Hiding Middleware describes how to avoid your business logic being
coupled to any particular middleware APIs allowing you to easily
switch from in JVM SEDA to JMS, ActiveMQ, Hibernate, JPA, JDBC,
iBATIS or JavaSpace etc.
• Visualisation describes how to visualise your Enterprise Integration
Patterns to help you understand your routing rules
• Business Activity Monitoring (BAM) for monitoring business processes
across systems
• Extract Transform Load (ETL) to load data into systems or databases
• Testing for testing distributed and asynchronous systems using a
messaging approach
◦ Camel Test for creating test cases using a single Java class
for all your configuration and routing
◦ Spring Testing uses Spring Test together with either XML or
Java Config to dependency inject your test classes
◦ Guice uses Guice to dependency inject your test classes
C O O KB O O K
38
• Templating is a great way to create service stubs to be able to test
your system without some back end system.
• Database for working with databases
• Parallel Processing and Ordering on how using parallel processing
and SEDA or JMS based load balancing can be achieved.
• Asynchronous Processing in Camel Routes.
• Implementing Virtual Topics on other JMS providers shows how to get
the effect of Virtual Topics and avoid issues with JMS durable topics
• Camel Transport for CXF describes how to put the Camel context into
the CXF transport layer.
• Fine Grained Control Over a Channel describes how to deliver a
sequence of messages over a single channel and then stopping any
more messages being sent over that channel. Typically used for
sending data over a socket and then closing the socket.
• EventNotifier to log details about all sent Exchanges shows how to let
Camels EventNotifier log all sent to endpoint events and how long
time it took.
• Loading routes from XML files into an existing CamelContext.
• Using MDC logging with Camel
BEAN INTEGRATION
Camel supports the integration of beans and POJOs in a number of ways
Bean Binding
Whenever Camel invokes a bean method, either via the Bean component,
Spring Remoting or POJO Consuming then the Bean Binding mechanism is
used to figure out what method to use (if it is not explicit) and how to bind
the Message to the parameters possibly using the Parameter Binding
Annotations
Annotations
If a bean is defined in Spring XML or scanned using the Spring 2.5 component
scanning mechanism and a <camelContext> is used or a
CamelBeanPostProcessor then we process a number of Camel annotations to
do various things such as injecting resources or producing, consuming or
routing messages.
• POJO Consuming to consume and possibly route messages from
Camel
• POJO Producing to make it easy to produce camel messages from
your POJOs
39
COOKBOOK
• RecipientList Annotation for creating a Recipient List from a POJO
method
• RoutingSlip Annotation for creating a Routing Slip for a POJO method
• Bean Injection to inject Camel related resources into your POJOs
• Using Exchange Pattern Annotations describes how the pattern
annotations can be used to change the behaviour of method
invocations with Spring Remoting or POJO Producing
Spring Remoting
We support a Spring Remoting provider which uses Camel as the underlying
transport mechanism. The nice thing about this approach is we can use any
of the Camel transport Components to communicate between beans. It also
means we can use Content Based Router and the other Enterprise Integration
Patterns in between the beans; in particular we can use Message Translator
to be able to convert what the on-the-wire messages look like in addition to
adding various headers and so forth.
Bean Component
The Bean component supports the creation of a proxy via ProxyHelper to a
Java interface; which the implementation just sends a message containing a
BeanInvocation to some Camel endpoint.
Then there is a server side implementation which consumes a message
and uses the Bean Binding to bind the message to invoke a method passing
in its parameters.
Annotation Based Expression Language
You can also use any of the Languages supported in Camel to bind
expressions to method parameters when using Bean Integration. For
example you can use any of these annotations:
Annotation
Description
@Bean
Inject a Bean expression
@BeanShell
Inject a BeanShell expression
@Constant
Inject a Constant expression
@EL
Inject an EL expression
@Groovy
Inject a Groovy expression
@Header
Inject a Header expression
C O O KB O O K
40
@JavaScript
Inject a JavaScript expression
@MVEL
Inject a Mvel expression
@OGNL
Inject an OGNL expression
@PHP
Inject a PHP expression
@Python
Inject a Python expression
@Ruby
Inject a Ruby expression
@Simple
Inject an Simple expression
@XPath
Inject an XPath expression
@XQuery
Inject an XQuery expression
Example:
public class Foo {
@MessageDriven(uri = "activemq:my.queue")
public void doSomething(@XPath("/foo/bar/text()") String correlationID, @Body
String body) {
// process the inbound message here
}
}
Advanced example using @Bean
And an example of using the the @Bean binding annotation, where you can
use a Pojo where you can do whatever java code you like:
public class Foo {
@MessageDriven(uri = "activemq:my.queue")
public void doSomething(@Bean("myCorrelationIdGenerator") String correlationID,
@Body String body) {
// process the inbound message here
}
}
And then we can have a spring bean with the id
myCorrelationIdGenerator where we can compute the id.
41
COOKBOOK
public class MyIdGenerator {
private UserManager userManager;
public String generate(@Header(name = "user") String user, @Body String payload)
throws Exception {
User user = userManager.lookupUser(user);
String userId = user.getPrimaryId();
String id = userId + generateHashCodeForPayload(payload);
return id;
}
}
The Pojo MyIdGenerator has one public method that accepts two parameters.
However we have also annotated this one with the @Header and @Body
annotation to help Camel know what to bind here from the Message from the
Exchange being processed.
Of course this could be simplified a lot if you for instance just have a
simple id generator. But we wanted to demonstrate that you can use the
Bean Binding annotations anywhere.
public class MySimpleIdGenerator {
public static int generate()
// generate a unique id
return 123;
{
}
}
And finally we just need to remember to have our bean registered in the
Spring Registry:
<bean id="myCorrelationIdGenerator" class="com.mycompany.MySimpleIdGenerator"/>
Example using Groovy
In this example we have an Exchange that has a User object stored in the in
header. This User object has methods to get some user information. We want
to use Groovy to inject an expression that extracts and concats the fullname
of the user into the fullName parameter.
public void doSomething(@Groovy("$request.header['user'].firstName
$request.header['user'].familyName) String fullName, @Body String body) {
// process the inbound message here
}
C O O KB O O K
42
Groovy supports GStrings that is like a template where we can insert $
placeholders that will be evaluated by Groovy.
Bean Binding
The Bean Binding in Camel defines both which methods are invoked and also
how the Message is converted into the parameters of the method when it is
invoked.
Choosing the method to invoke
The binding of a Camel Message to a bean method call can occur in different
ways, order if importance:
• if the message contains the header CamelBeanMethodName
(org.apache.camel.MethodName in Camel 1.x) then that method
is invoked, converting the body to whatever the argument is to the
method. From Camel 2.8 onwards you can qualify parameter types
to exact pin-point which method to use when using overloaded
methods with the same name.
• the method name can be specified explicitly in the DSL or when
using POJO Consuming
• Camel 2.0: if the bean has a method that is marked with @Handler
annotation then that method is selected
• if the bean can be converted to a Processor using the Type Converter
mechanism then this is used to process the message. This
mechanism is used by the ActiveMQ component to allow any JMS
MessageListener to be invoked directly by Camel without having to
write any integration glue code. You can use the same mechanism to
integrate Camel into any other messaging/remoting frameworks.
• if the body of the message can be converted to a BeanInvocation
(the default payload used by the ProxyHelper) - then that its used to
invoke the method and pass the arguments
• otherwise the type of the method body is used to try find a method
which matches; an error is thrown if a single method cannot be
chosen unambiguously.
• you can also use Exchange as the parameter itself, but then the
return type must be void.
In case where Camel will not be able to choose a method to invoke an
AmbiguousMethodCallException is thrown.
By default the return value is set on the outbound message body.
43
COOKBOOK
Using type qualifier to pin-point method to use when having
overloaded methods
Available as of Camel 2.8
If you have a Bean which has overloaded methods you can now specify
the parameter types in the method name, so Camel can match the method
you intend to use.
Given the following bean:
Listing 4. MyBean
public static final class MyBean {
public String hello(String name) {
return "Hello " + name;
}
public String hello(String name, @Header("country") String country) {
return "Hello " + name + " you are from " + country;
}
public String times(String name, @Header("times") int times) {
StringBuilder sb = new StringBuilder();
for (int i = 0; i < times; i++) {
sb.append(name);
}
return sb.toString();
}
public String times(byte[] data, @Header("times") int times) {
String s = new String(data);
StringBuilder sb = new StringBuilder();
for (int i = 0; i < times; i++) {
sb.append(s);
if (i < times - 1) {
sb.append(",");
}
}
return sb.toString();
}
public String times(String name, int times, char separator) {
StringBuilder sb = new StringBuilder();
for (int i = 0; i < times; i++) {
sb.append(name);
if (i < times - 1) {
sb.append(separator);
}
}
return sb.toString();
}
}
C O O KB O O K
44
Then the MyBean has 2 overloaded methods with the names hello and
times. So if we want to use the method which has 2 parameters we can do
as follows in the Camel route:
Listing 5. Invoke 2 parameter method
from("direct:start")
.bean(MyBean.class, "hello(String,String)")
.to("mock:result");
We can also use a * as wildcard so we can just say we want to execute the
method with 2 parameters we do
Listing 6. Invoke 2 parameter method using wildcard
from("direct:start")
.bean(MyBean.class, "hello(*,*)")
.to("mock:result");
By default Camel will match the type name using the simple name, eg any
leading package name will be disregarded. However if you want to match
using the FQN then specify the FQN type and Camel will leverage that. So if
you have a com.foo.MyOrder and you want to match against the FQN, and
not the simple name "MyOrder" then do as follows:
.bean(OrderService.class, "doSomething(com.foo.MyOrder)")
Parameter binding
When a method have been chosen to be invoked Camel will bind to the
parameters of the method.
The following Camel specific types is automatic binded:
▪ org.apache.camel.Exchange
▪ org.apache.camel.Message
▪ Camel 2.0: org.apache.camel.CamelContext
▪ org.apache.camel.TypeConverter
▪ Camel 2.0: org.apache.camel.spi.Registry
▪ java.lang.Exception
So if you declare any of the given type above they will be provided by Camel.
A note on the Exception is that it will bind to the caught exception of the
Exchange. So its often usable if you use a Pojo to handle a given using using
eg an onException route.
What is most interresting is that Camel will also try to bind the body of the
Exchange to the first parameter of the method signature (albeit not of any of
the types above). So if we for instance declare e parameter as: String body
45
COOKBOOK
The current implementation for choosing method using type
qualifiers only compares the type names. It does not check any
instanceof checks or the likes. The type name must match
exactly, as its using a string equals comparison.
then Camel will bind the IN body to this type. Camel will also automatic type
convert to the given type declared.
Okay lets show some examples.
Below is just a simple method with a body binding. Camel will bind the IN
body to the body parameter and convert it to a String type.
public String doSomething(String body)
And in this sample we got one of the automatic binded type as well, for
instance the Registry that we can use to lookup beans.
public String doSomething(String body, Registry registry)
And we can also use Exchange as well:
public String doSomething(String body, Exchange exchange)
You can have multiple types as well
public String doSomething(String body, Exchange exchange, TypeConverter converter)
And imagine you use a Pojo to handle a given custom exception
InvalidOrderException then we can bind that as well:
Notice we can bind to it even if we use a sub type of java.lang.Exception
as Camel still knows its an exception and thus can bind the caused exception
(if any exists).
public String badOrder(String body, InvalidOrderException invalid)
So what about headers and other stuff? Well now it gets a bit tricky so we
can use annotations to help us. See next section for details.
C O O KB O O K
46
Binding Annotations
You can use the Parameter Binding Annotations to customize how parameter
values are created from the Message
Examples
For example a Bean such as:
public class Bar {
public String doSomething(String body) {
// process the in body and return whatever you want
return "Bye World";
}
Or the Exchange example. Notice that the return type must be void when
there is only a single parameter:
public class Bar {
public void doSomething(Exchange exchange) {
// process the exchange
exchange.getIn().setBody("Bye World");
}
@Handler
Available as of Camel 2.0
You can mark a method in your bean with the @Handler annotation to
indicate that this method should be used for Bean Binding.
This has the advantage as you do not have to specify the method name in
the Camel route. And thus you do not run into problems when you rename
the method name using an IDE that don't find all references.
public class Bar {
@Handler
public String doSomething(String body) {
// process the in body and return whatever you want
return "Bye World";
}
47
COOKBOOK
POJO consuming
For example you could use POJO Consuming to write a bean like this
public class Foo {
@Consume(uri = "activemq:my.queue")
public void doSomething(String body) {
// process the inbound message here
}
}
Here Camel with subscribe to an ActiveMQ queue, then convert the message
payload to a String (so dealing with TextMessage, ObjectMessage and
BytesMessage in JMS), then process this method.
Bean Injection
We support the injection of various resources using @EndpointInject. This can
be used to inject
• Endpoint instances which can be used for testing when used with
Mock endpoints; see the Spring Testing for an example.
• ProducerTemplate instances for POJO Producing
• client side proxies for POJO Producing which is a simple approach to
Spring Remoting
Parameter Binding Annotations
Annotations can be used to define an Expression or to extract various
headers, properties or payloads from a Message when invoking a bean
method (see Bean Integration for more detail of how to invoke bean
methods) together with being useful to help disambiguate which method to
invoke.
If no annotations are used then Camel assumes that a single parameter is
the body of the message. Camel will then use the Type Converter mechanism
to convert from the expression value to the actual type of the parameter.
The core annotations are as follows
Annotation
Meaning
Parameter
@Body
To bind to an inbound message body
Â
@ExchangeException
To bind to an Exception set on the
exchange (Camel 2.0)
Â
C O O KB O O K
48
@Consume requires camel-spring
Using the @Consume annotations requires camel-spring that uses
the org.apache.camel.spring.CamelBeanPostProcessor to
perform the setup for this consumer and the needed bean bindings.
@MessageDriven is @deprecated
The @MessageDriven has been replaced with @Consume in Camel
1.5.0 or newer. Its now marked as @deprecated and will be
removed in Camel 2.0.
camel-core
The annotations below are all part of camel-core and thus does
not require camel-spring or Spring. These annotations can be
used with the Bean component or when invoking beans in the DSL
49
@Header
To bind to an inbound message
header
String
name of
the header
@Headers
To bind to the Map of the inbound
message headers
Â
@OutHeaders
To bind to the Map of the outbound
message headers
Â
@Property
To bind to a named property on the
exchange
String
name of
the
property
@Properties
To bind to the property map on the
exchange
Â
@Handler
Camel 2.0: Not part as a type
parameter but stated in this table
anyway to spread the good word
that we have this annotation in
Camel now. See more at Bean
Binding.
Â
COOKBOOK
The follow annotations @Headers, @OutHeaders and @Properties binds to
the backing java.util.Map so you can alter the content of these maps
directly, for instance using the put method to add a new entry. See the
OrderService class at Exception Clause for such an example.
Example
In this example below we have a @Consume consumer (like message driven)
that consumes JMS messages from the activemq queue. We use the @Header
and @Body parameter binding annotations to bind from the JMSMessage to
the method parameters.
public class Foo {
@Consume(uri = "activemq:my.queue")
public void doSomething(@Header(name = "JMSCorrelationID") String correlationID,
@Body String body) {
// process the inbound message here
}
}
In the above Camel will extract the value of Message.getJMSCorrelationID(),
then using the Type Converter to adapt the value to the type of the
parameter if required - it will inject the parameter value for the
correlationID parameter. Then the payload of the message will be
converted to a String and injected into the body parameter.
You don't need to use the @Consume annotation; as you could use the
Camel DSL to route to the beans method
Using the DSL to invoke the bean method
Here is another example which does not use POJO Consuming annotations
but instead uses the DSL to route messages to the bean method
public class Foo {
public void doSomething(@Header(name = "JMSCorrelationID") String correlationID,
@Body String body) {
// process the inbound message here
}
}
The routing DSL then looks like this
C O O KB O O K
50
from("activemq:someQueue").
to("bean:myBean");
Here myBean would be looked up in the Registry (such as JNDI or the Spring
ApplicationContext), then the body of the message would be used to try
figure out what method to call.
If you want to be explicit you can use
from("activemq:someQueue").
to("bean:myBean?methodName=doSomething");
And here we have a nifty example for you to show some great power in
Camel. You can mix and match the annotations with the normal parameters,
so we can have this example with annotations and the Exchange also:
public void doSomething(@Header(name = "user") String user, @Body String body,
Exchange exchange) {
exchange.getIn().setBody(body + "MyBean");
}
Annotation Based Expression Language
You can also use any of the Languages supported in Camel to bind
expressions to method parameters when using Bean Integration. For
example you can use any of these annotations:
51
Annotation
Description
@Bean
Inject a Bean expression
@BeanShell
Inject a BeanShell expression
@Constant
Inject a Constant expression
@EL
Inject an EL expression
@Groovy
Inject a Groovy expression
@Header
Inject a Header expression
@JavaScript
Inject a JavaScript expression
@MVEL
Inject a Mvel expression
@OGNL
Inject an OGNL expression
@PHP
Inject a PHP expression
@Python
Inject a Python expression
COOKBOOK
@Ruby
Inject a Ruby expression
@Simple
Inject an Simple expression
@XPath
Inject an XPath expression
@XQuery
Inject an XQuery expression
Example:
public class Foo {
@MessageDriven(uri = "activemq:my.queue")
public void doSomething(@XPath("/foo/bar/text()") String correlationID, @Body
String body) {
// process the inbound message here
}
}
Advanced example using @Bean
And an example of using the the @Bean binding annotation, where you can
use a Pojo where you can do whatever java code you like:
public class Foo {
@MessageDriven(uri = "activemq:my.queue")
public void doSomething(@Bean("myCorrelationIdGenerator") String correlationID,
@Body String body) {
// process the inbound message here
}
}
And then we can have a spring bean with the id
myCorrelationIdGenerator where we can compute the id.
public class MyIdGenerator {
private UserManager userManager;
public String generate(@Header(name = "user") String user, @Body String payload)
throws Exception {
User user = userManager.lookupUser(user);
String userId = user.getPrimaryId();
String id = userId + generateHashCodeForPayload(payload);
return id;
C O O KB O O K
52
}
}
The Pojo MyIdGenerator has one public method that accepts two parameters.
However we have also annotated this one with the @Header and @Body
annotation to help Camel know what to bind here from the Message from the
Exchange being processed.
Of course this could be simplified a lot if you for instance just have a
simple id generator. But we wanted to demonstrate that you can use the
Bean Binding annotations anywhere.
public class MySimpleIdGenerator {
public static int generate()
// generate a unique id
return 123;
{
}
}
And finally we just need to remember to have our bean registered in the
Spring Registry:
<bean id="myCorrelationIdGenerator" class="com.mycompany.MySimpleIdGenerator"/>
Example using Groovy
In this example we have an Exchange that has a User object stored in the in
header. This User object has methods to get some user information. We want
to use Groovy to inject an expression that extracts and concats the fullname
of the user into the fullName parameter.
public void doSomething(@Groovy("$request.header['user'].firstName
$request.header['user'].familyName) String fullName, @Body String body) {
// process the inbound message here
}
Groovy supports GStrings that is like a template where we can insert $
placeholders that will be evaluated by Groovy.
@MessageDriven or @Consume
53
COOKBOOK
@MessageDriven is @deprecated
@MessageDriven is deprecated in Camel 1.x. You should use
@Consume instead. Its removed in Camel 2.0.
To consume a message you use either the @MessageDriven annotation or
from 1.5.0 the @Consume annotation to mark a particular method of a bean
as being a consumer method. The uri of the annotation defines the Camel
Endpoint to consume from.
e.g. lets invoke the onCheese() method with the String body of the
inbound JMS message from ActiveMQ on the cheese queue; this will use the
Type Converter to convert the JMS ObjectMessage or BytesMessage to a
String - or just use a TextMessage from JMS
public class Foo {
@Consume(uri="activemq:cheese")
public void onCheese(String name) {
...
}
}
The Bean Binding is then used to convert the inbound Message to the
parameter list used to invoke the method .
What this does is basically create a route that looks kinda like this
from(uri).bean(theBean, "methodName");
Using context option to apply only a certain CamelContext
Available as of Camel 2.0
See the warning above.
You can use the context option to specify which CamelContext the
consumer should only apply for. For example:
@Consume(uri="activemq:cheese", context="camel-1")
public void onCheese(String name) {
The consumer above will only be created for the CamelContext that have the
context id = camel-1. You set this id in the XML tag:
C O O KB O O K
54
When using more than one CamelContext
When you use more than 1 CamelContext you might end up with
each of them creating a POJO Consuming.
In Camel 2.0 there is a new option on @Consume that allows you
to specify which CamelContext id/name you want it to apply for.
<camelContext id="camel-1" ...>
Using an explicit route
If you want to invoke a bean method from many different endpoints or within
different complex routes in different circumstances you can just use the
normal routing DSL or the Spring XML configuration file.
For example
from(uri).beanRef("myBean", "methodName");
which will then look up in the Registry and find the bean and invoke the
given bean name. (You can omit the method name and have Camel figure
out the right method based on the method annotations and body type).
Use the Bean endpoint
You can always use the bean endpoint
from(uri).to("bean:myBean?method=methodName");
Which approach to use?
Using the @MessageDriven/@Consume annotations are simpler when you
are creating a simple route with a single well defined input URI.
However if you require more complex routes or the same bean method
needs to be invoked from many places then please use the routing DSL as
shown above.
There are two different ways to send messages to any Camel Endpoint
from a POJO
55
COOKBOOK
@EndpointInject
To allow sending of messages from POJOs you can use @EndpointInject()
annotation. This will inject either a ProducerTemplate or CamelTemplate so
that the bean can send message exchanges.
e.g. lets send a message to the foo.bar queue in ActiveMQ at some point
public class Foo {
@EndpointInject(uri="activemq:foo.bar")
ProducerTemplate producer;
public void doSomething() {
if (whatever) {
producer.sendBody("<hello>world!</hello>");
}
}
}
The downside of this is that your code is now dependent on a Camel API, the
ProducerTemplate. The next section describes how to remove this
Hiding the Camel APIs from your code using @Produce
We recommend Hiding Middleware APIs from your application code so the
next option might be more suitable.
You can add the @Produce annotation to an injection point (a field or
property setter) using a ProducerTemplate or using some interface you use in
your business logic. e.g.
public interface MyListener {
String sayHello(String name);
}
public class MyBean {
@Produce(uri = "activemq:foo")
protected MyListener producer;
public void doSomething() {
// lets send a message
String response = producer.sayHello("James");
}
}
Here Camel will automatically inject a smart client side proxy at the
@Produce annotation - an instance of the MyListener instance. When we
invoke methods on this interface the method call is turned into an object and
using the Camel Spring Remoting mechanism it is sent to the endpoint - in
C O O KB O O K
56
this case the ActiveMQ endpoint to queue foo; then the caller blocks for a
response.
If you want to make asynchronous message sends then use an @InOnly
annotation on the injection point.
@RECIPIENTLIST ANNOTATION
As of 1.5.0 we now support the use of @RecipientList on a bean method to
easily create a dynamic Recipient List using a Java method.
Simple Example using @Consume
package com.acme.foo;
public class RouterBean {
@Consume(uri = "activemq:foo")
@RecipientList
public String[] route(String body) {
return new String[]{"activemq:bar", "activemq:whatnot"};
}
}
For example if the above bean is configured in Spring when using a
<camelContext> element as follows
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/
schema/beans/spring-beans-2.5.xsd
http://activemq.apache.org/camel/schema/spring http://activemq.apache.org/
camel/schema/spring/camel-spring.xsd
">
<camelContext xmlns="http://activemq.apache.org/camel/schema/spring"/>
<bean id="myRecipientList" class="com.acme.foo.RouterBean"/>
</beans>
then a route will be created consuming from the foo queue on the ActiveMQ
component which when a message is received the message will be
forwarded to the endpoints defined by the result of this method call - namely
the bar and whatnot queues.
57
COOKBOOK
How it works
The return value of the @RecipientList method is converted to either a
java.util.Collection / java.util.Iterator or array of objects where each element
is converted to an Endpoint or a String, or if you are only going to route to a
single endpoint then just return either an Endpoint object or an object that
can be converted to a String. So the following methods are all valid
@RecipientList
public String[] route(String body) { ... }
@RecipientList
public List<String> route(String body) { ... }
@RecipientList
public Endpoint route(String body) { ... }
@RecipientList
public Endpoint[] route(String body) { ... }
@RecipientList
public Collection<Endpoint> route(String body) { ... }
@RecipientList
public URI route(String body) { ... }
@RecipientList
public URI[] route(String body) { ... }
Then for each endpoint or URI the message is forwarded a separate copy to
that endpoint.
You can then use whatever Java code you wish to figure out what
endpoints to route to; for example you can use the Bean Binding annotations
to inject parts of the message body or headers or use Expression values on
the message.
More Complex Example Using DSL
In this example we will use more complex Bean Binding, plus we will use a
separate route to invoke the Recipient List
public class RouterBean2 {
@RecipientList
public String route(@Header("customerID") String custID String body) {
if (custID == null) return null;
return "activemq:Customers.Orders." + custID;
}
}
C O O KB O O K
58
public class MyRouteBuilder extends RouteBuilder {
protected void configure() {
from("activemq:Orders.Incoming").recipientList(bean("myRouterBean", "route"));
}
}
Notice how we are injecting some headers or expressions and using them to
determine the recipients using Recipient List EIP.
See the Bean Integration for more details.
USING EXCHANGE PATTERN ANNOTATIONS
When working with POJO Producing or Spring Remoting you invoke methods
which typically by default are InOut for Request Reply. That is there is an In
message and an Out for the result. Typically invoking this operation will be
synchronous, the caller will block until the server returns a result.
Camel has flexible Exchange Pattern support - so you can also support the
Event Message pattern to use InOnly for asynchronous or one way
operations. These are often called 'fire and forget' like sending a JMS
message but not waiting for any response.
From 1.5 onwards Camel supports annotations for specifying the message
exchange pattern on regular Java methods, classes or interfaces.
Specifying InOnly methods
Typically the default InOut is what most folks want but you can customize to
use InOnly using an annotation.
public interface Foo {
Object someInOutMethod(String input);
String anotherInOutMethod(Cheese input);
@InOnly
void someInOnlyMethod(Document input);
}
The above code shows three methods on an interface; the first two use the
default InOut mechanism but the someInOnlyMethod uses the InOnly
annotation to specify it as being a oneway method call.
59
COOKBOOK
Class level annotations
You can also use class level annotations to default all methods in an interface
to some pattern such as
@InOnly
public interface Foo {
void someInOnlyMethod(Document input);
void anotherInOnlyMethod(String input);
}
Annotations will also be detected on base classes or interfaces. So for
example if you created a client side proxy for
public class MyFoo implements Foo {
...
}
Then the methods inherited from Foo would be InOnly.
Overloading a class level annotation
You can overload a class level annotation on specific methods. A common
use case for this is if you have a class or interface with many InOnly methods
but you want to just annote one or two methods as InOut
@InOnly
public interface Foo {
void someInOnlyMethod(Document input);
void anotherInOnlyMethod(String input);
@InOut
String someInOutMethod(String input);
}
In the above Foo interface the someInOutMethod will be InOut
Using your own annotations
You might want to create your own annotations to represent a group of
different bits of metadata; such as combining synchrony, concurrency and
transaction behaviour.
So you could annotate your annotation with the @Pattern annotation to
default the exchange pattern you wish to use.
For example lets say we want to create our own annotation called
@MyAsyncService
C O O KB O O K
60
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE, ElementType.METHOD})
// lets add the message exchange pattern to it
@Pattern(ExchangePattern.InOnly)
// lets add some other annotations - maybe transaction behaviour?
public @interface MyAsyncService {
}
Now we can use this annotation and Camel will figure out the correct
exchange pattern...
public interface Foo {
void someInOnlyMethod(Document input);
void anotherInOnlyMethod(String input);
@MyAsyncService
String someInOutMethod(String input);
}
When writing software these days, its important to try and decouple as much
middleware code from your business logic as possible.
This provides a number of benefits...
• you can choose the right middleware solution for your deployment
and switch at any time
• you don't have to spend a large amount of time learning the specifics
of any particular technology, whether its JMS or JavaSpace or
Hibernate or JPA or iBATIS whatever
For example if you want to implement some kind of message passing,
remoting, reliable load balancing or asynchronous processing in your
application we recommend you use Camel annotations to bind your services
and business logic to Camel Components which means you can then easily
switch between things like
• in JVM messaging with SEDA
• using JMS via ActiveMQ or other JMS providers for reliable load
balancing, grid or publish and subscribe
• for low volume, but easier administration since you're probably
already using a database you could use
◦ Hibernate or JPA to use an entity bean / table as a queue
◦ iBATIS to work with SQL
◦ JDBC for raw SQL access
• use JavaSpace
61
COOKBOOK
How to decouple from middleware APIs
The best approach when using remoting is to use Spring Remoting which can
then use any messaging or remoting technology under the covers. When
using Camel's implementation you can then use any of the Camel
Components along with any of the Enterprise Integration Patterns.
Another approach is to bind Java beans to Camel endpoints via the Bean
Integration. For example using POJO Consuming and POJO Producing you can
avoid using any Camel APIs to decouple your code both from middleware
APIs and Camel APIs!
VISUALISATION
Camel supports the visualisation of your Enterprise Integration Patterns using
the GraphViz DOT files which can either be rendered directly via a suitable
GraphViz tool or turned into HTML, PNG or SVG files via the Camel Maven
Plugin.
Here is a typical example of the kind of thing we can generate
If you click on the actual generated htmlyou will see that you can navigate
from an EIP node to its pattern page, along with getting hover-over tool tips
ec.
C O O KB O O K
62
How to generate
See Camel Dot Maven Goal or the other maven goals Camel Maven Plugin
For OS X users
If you are using OS X then you can open the DOT file using graphviz which
will then automatically re-render if it changes, so you end up with a real time
graphical representation of the topic and queue hierarchies!
Also if you want to edit the layout a little before adding it to a wiki to
distribute to your team, open the DOT file with OmniGraffle then just edit
away
BUSINESS ACTIVITY MONITORING
The Camel BAM module provides a Business Activity Monitoring (BAM)
framework for testing business processes across multiple message
exchanges on different Endpoint instances.
For example if you have a simple system which you submit Purchase
Orders into system A and then receive Invoices from system B, you might
want to test that for a specific Purchase Order you receive a matching
Invoice from system B within a specific time period.
How Camel BAM Works
What Camel BAM does is use a Correlation Identifier on an input message to
determine which Process Instance a message belongs to. The process
instance is an entity bean which can maintain state for each Activity (where
an activity typically maps to a single endpoint, such as the receipt of
Purchase orders, or the receipt of Invoices).
You can then add rules which are fired when a message is received on any
activity such as to set time expectations, or to perform real time
reconciliation of values across activities etc.
Simple Example
The following example shows how to perform some time based rules on a
simple business process of 2 activities A and B (which maps to the Purchase
Order and Invoice example above). If you want to experiment with this
scenario you could edit the Test Case which defines the activities and rules,
then tests that they work.
63
COOKBOOK
return new ProcessBuilder(jpaTemplate, transactionTemplate) {
public void configure() throws Exception {
// lets define some activities, correlating on an XPath on the message bodies
ActivityBuilder a = activity("seda:a").name("a")
.correlate(xpath("/hello/@id"));
ActivityBuilder b = activity("seda:b").name("b")
.correlate(xpath("/hello/@id"));
// now lets add some rules
b.starts().after(a.completes())
.expectWithin(seconds(1))
.errorIfOver(seconds(errorTimeout)).to("mock:overdue");
}
};
As you can see in the above example, we define two activities first, then we
define rules on when we expect the activities on an individual process
instance to complete by along with the time at which we should assume
there is an error. The ProcessBuilder is-a RouteBuilder and can be added to
any CamelContext
Complete Example
For a complete example please see the BAM Example which is part of the
standard Camel Examples
Use Cases
In the world of finance a common requirement is tracking financial trades.
Often a trader will submit a Front Office Trade which then flows through the
Middle Office and Back Office through various systems to settle the trade so
that money is exchanged. You may wish to add tests that front and back
office trades match up within a time period; if they don't match or a back
office trade does not arrive within a required amount of time, you might want
to fire off an alarm.
EXTRACT TRANSFORM LOAD (ETL)
The ETL (Extract, Transform, Load) is a mechanism for loading data into
systems or databases using some kind of Data Format from a variety of
sources; often files then using Pipes and Filters, Message Translator and
possible other Enterprise Integration Patterns.
C O O KB O O K
64
So you could query data from various Camel Components such as File,
HTTP or JPA, perform multiple patterns such as Splitter or Message Translator
then send the messages to some other Component.
To show how this all fits together, try the ETL Example
MOCK COMPONENT
Testing of distributed and asynchronous processing is notoriously difficult.
The Mock, Test and DataSet endpoints work great with the Camel Testing
Framework to simplify your unit and integration testing using Enterprise
Integration Patterns and Camel's large range of Components together with
the powerful Bean Integration.
The Mock component provides a powerful declarative testing mechanism,
which is similar to jMock in that it allows declarative expectations to be
created on any Mock endpoint before a test begins. Then the test is run,
which typically fires messages to one or more endpoints, and finally the
expectations can be asserted in a test case to ensure the system worked as
expected.
This allows you to test various things like:
• The correct number of messages are received on each endpoint,
• The correct payloads are received, in the right order,
• Messages arrive on an endpoint in order, using some Expression to
create an order testing function,
• Messages arrive match some kind of Predicate such as that specific
headers have certain values, or that parts of the messages match
some predicate, such as by evaluating an XPath or XQuery
Expression.
Note that there is also the Test endpoint which is a Mock endpoint, but which
uses a second endpoint to provide the list of expected message bodies and
automatically sets up the Mock endpoint assertions. In other words, it's a
Mock endpoint that automatically sets up its assertions from some sample
messages in a File or database, for example.
URI format
mock:someName[?options]
Where someName can be any string that uniquely identifies the endpoint.
You can append query options to the URI in the following format,
?option=value&option=value&...
65
COOKBOOK
Options
Option
Default
Description
reportGroup
null
A size to use a throughput logger for reporting
Simple Example
Here's a simple example of Mock endpoint in use. First, the endpoint is
resolved on the context. Then we set an expectation, and then, after the test
has run, we assert that our expectations have been met.
MockEndpoint resultEndpoint = context.resolveEndpoint("mock:foo", MockEndpoint.class);
resultEndpoint.expectedMessageCount(2);
// send some messages
...
// now lets assert that the mock:foo endpoint received 2 messages
resultEndpoint.assertIsSatisfied();
You typically always call the assertIsSatisfied() method to test that the
expectations were met after running a test.
Camel will by default wait 10 seconds when the assertIsSatisfied() is
invoked. This can be configured by setting the setResultWaitTime(millis)
method.
When the assertion is satisfied then Camel will stop waiting and continue
from the assertIsSatisfied method. That means if a new message arrives
on the mock endpoint, just a bit later, that arrival will not affect the outcome
of the assertion. Suppose you do want to test that no new messages arrives
after a period thereafter, then you can do that by setting the
setAssertPeriod method.
Using assertPeriod
Available as of Camel 2.7
When the assertion is satisfied then Camel will stop waiting and continue
from the assertIsSatisfied method. That means if a new message arrives
on the mock endpoint, just a bit later, that arrival will not affect the outcome
of the assertion. Suppose you do want to test that no new messages arrives
after a period thereafter, then you can do that by setting the
setAssertPeriod method, for example:
C O O KB O O K
66
MockEndpoint resultEndpoint = context.resolveEndpoint("mock:foo", MockEndpoint.class);
resultEndpoint.setAssertPeriod(5000);
resultEndpoint.expectedMessageCount(2);
// send some messages
...
// now lets assert that the mock:foo endpoint received 2 messages
resultEndpoint.assertIsSatisfied();
Setting expectations
You can see from the javadoc of MockEndpoint the various helper methods
you can use to set expectations. The main methods are as follows:
Method
Description
expectedMessageCount(int)
To define the expected message count on the endpoint.
expectedMinimumMessageCount(int)
To define the minimum number of expected messages on the endpoint.
expectedBodiesReceived(...)
To define the expected bodies that should be received (in order).
expectedHeaderReceived(...)
To define the expected header that should be received
expectsAscending(Expression)
To add an expectation that messages are received in order, using the given Expression to compare
messages.
expectsDescending(Expression)
To add an expectation that messages are received in order, using the given Expression to compare
messages.
expectsNoDuplicates(Expression)
To add an expectation that no duplicate messages are received; using an Expression to calculate a
unique identifier for each message. This could be something like the JMSMessageID if using JMS, or some
unique reference number within the message.
Here's another example:
resultEndpoint.expectedBodiesReceived("firstMessageBody", "secondMessageBody",
"thirdMessageBody");
Adding expectations to specific messages
In addition, you can use the message(int messageIndex) method to add
assertions about a specific message that is received.
For example, to add expectations of the headers or body of the first
message (using zero-based indexing like java.util.List), you can use the
following code:
resultEndpoint.message(0).header("foo").isEqualTo("bar");
There are some examples of the Mock endpoint in use in the camel-core
processor tests.
67
COOKBOOK
Mocking existing endpoints
Available as of Camel 2.7
Camel now allows you to automatic mock existing endpoints in your Camel
routes.
Suppose you have the given route below:
Listing 7. Route
@Override
protected RouteBuilder createRouteBuilder() throws Exception {
return new RouteBuilder() {
@Override
public void configure() throws Exception {
from("direct:start").to("direct:foo").to("log:foo").to("mock:result");
from("direct:foo").transform(constant("Bye World"));
}
};
}
You can then use the adviceWith feature in Camel to mock all the endpoints
in a given route from your unit test, as shown below:
Listing 8. adviceWith mocking all endpoints
public void testAdvisedMockEndpoints() throws Exception {
// advice the first route using the inlined AdviceWith route builder
// which has extended capabilities than the regular route builder
context.getRouteDefinitions().get(0).adviceWith(context, new
AdviceWithRouteBuilder() {
@Override
public void configure() throws Exception {
// mock all endpoints
mockEndpoints();
}
});
getMockEndpoint("mock:direct:start").expectedBodiesReceived("Hello World");
getMockEndpoint("mock:direct:foo").expectedBodiesReceived("Hello World");
getMockEndpoint("mock:log:foo").expectedBodiesReceived("Bye World");
getMockEndpoint("mock:result").expectedBodiesReceived("Bye World");
template.sendBody("direct:start", "Hello World");
assertMockEndpointsSatisfied();
// additional test to ensure correct endpoints in registry
assertNotNull(context.hasEndpoint("direct:start"));
assertNotNull(context.hasEndpoint("direct:foo"));
assertNotNull(context.hasEndpoint("log:foo"));
assertNotNull(context.hasEndpoint("mock:result"));
// all the endpoints was mocked
assertNotNull(context.hasEndpoint("mock:direct:start"));
C O O KB O O K
68
How it works
Important: The endpoints are still in action, what happens is that a
Mock endpoint is injected and receives the message first, it then
delegate the message to the target endpoint. You can view this as a
kind of intercept and delegate or endpoint listener.
assertNotNull(context.hasEndpoint("mock:direct:foo"));
assertNotNull(context.hasEndpoint("mock:log:foo"));
}
Notice that the mock endpoints is given the uri mock:<endpoint>, for
example mock:direct:foo. Camel logs at INFO level the endpoints being
mocked:
INFO
Adviced endpoint [direct://foo] with mock endpoint [mock:direct:foo]
Its also possible to only mock certain endpoints using a pattern. For example
to mock all log endpoints you do as shown:
Listing 9. adviceWith mocking only log endpoints using a pattern
public void testAdvisedMockEndpointsWithPattern() throws Exception {
// advice the first route using the inlined AdviceWith route builder
// which has extended capabilities than the regular route builder
context.getRouteDefinitions().get(0).adviceWith(context, new
AdviceWithRouteBuilder() {
@Override
public void configure() throws Exception {
// mock only log endpoints
mockEndpoints("log*");
}
});
// now we can refer to log:foo as a mock and set our expectations
getMockEndpoint("mock:log:foo").expectedBodiesReceived("Bye World");
getMockEndpoint("mock:result").expectedBodiesReceived("Bye World");
template.sendBody("direct:start", "Hello World");
assertMockEndpointsSatisfied();
// additional test to ensure correct endpoints in registry
assertNotNull(context.hasEndpoint("direct:start"));
assertNotNull(context.hasEndpoint("direct:foo"));
assertNotNull(context.hasEndpoint("log:foo"));
assertNotNull(context.hasEndpoint("mock:result"));
69
COOKBOOK
Mocked endpoints are without parameters
Endpoints which are mocked will have their parameters stripped off.
For example the endpoint "log:foo?showAll=true" will be mocked to
the following endpoint "mock:log:foo". Notice the parameters has
been removed.
// only the log:foo endpoint was mocked
assertNotNull(context.hasEndpoint("mock:log:foo"));
assertNull(context.hasEndpoint("mock:direct:start"));
assertNull(context.hasEndpoint("mock:direct:foo"));
}
The pattern supported can be a wildcard or a regular expression. See more
details about this at Intercept as its the same matching function used by
Camel.
Mocking existing endpoints using the camel-test
component
Instead of using the adviceWith to instruct Camel to mock endpoints, you
can easily enable this behavior when using the camel-test Test Kit.
The same route can be tested as follows. Notice that we return "*" from the
isMockEndpoints method, which tells Camel to mock all endpoints.
If you only want to mock all log endpoints you can return "log*" instead.
Listing 10. isMockEndpoints using camel-test kit
public class IsMockEndpointsJUnit4Test extends CamelTestSupport {
@Override
public String isMockEndpoints() {
// override this method and return the pattern for which endpoints to mock.
// use * to indicate all
return "*";
}
@Test
public void testMockAllEndpoints() throws Exception {
// notice we have automatic mocked all endpoints and the name of the
endpoints is "mock:uri"
getMockEndpoint("mock:direct:start").expectedBodiesReceived("Hello World");
getMockEndpoint("mock:direct:foo").expectedBodiesReceived("Hello World");
getMockEndpoint("mock:log:foo").expectedBodiesReceived("Bye World");
getMockEndpoint("mock:result").expectedBodiesReceived("Bye World");
C O O KB O O K
70
Mind that mocking endpoints causes the messages to be copied
when they arrive on the mock.
That means Camel will use more memory. This may not be suitable
when you send in a lot of messages.
template.sendBody("direct:start", "Hello World");
assertMockEndpointsSatisfied();
// additional test to ensure correct endpoints in registry
assertNotNull(context.hasEndpoint("direct:start"));
assertNotNull(context.hasEndpoint("direct:foo"));
assertNotNull(context.hasEndpoint("log:foo"));
assertNotNull(context.hasEndpoint("mock:result"));
// all the endpoints was mocked
assertNotNull(context.hasEndpoint("mock:direct:start"));
assertNotNull(context.hasEndpoint("mock:direct:foo"));
assertNotNull(context.hasEndpoint("mock:log:foo"));
}
@Override
protected RouteBuilder createRouteBuilder() throws Exception {
return new RouteBuilder() {
@Override
public void configure() throws Exception {
from("direct:start").to("direct:foo").to("log:foo").to("mock:result");
from("direct:foo").transform(constant("Bye World"));
}
};
}
}
Mocking existing endpoints with XML DSL
If you do not use the camel-test component for unit testing (as shown
above) you can use a different approach when using XML files for routes.
The solution is to create a new XML file used by the unit test and then
include the intended XML file which has the route you want to test.
Suppose we have the route in the camel-route.xml file:
Listing 11. camel-route.xml
<!-- this camel route is in the camel-route.xml file -->
<camelContext xmlns="http://camel.apache.org/schema/spring">
71
COOKBOOK
<route>
<from uri="direct:start"/>
<to uri="direct:foo"/>
<to uri="log:foo"/>
<to uri="mock:result"/>
</route>
<route>
<from uri="direct:foo"/>
<transform>
<constant>Bye World</constant>
</transform>
</route>
</camelContext>
Then we create a new XML file as follows, where we include the camelroute.xml file and define a spring bean with the class
org.apache.camel.impl.InterceptSendToMockEndpointStrategy which
tells Camel to mock all endpoints:
Listing 12. test-camel-route.xml
<!-- the Camel route is defined in another XML file -->
<import resource="camel-route.xml"/>
<!-- bean which enables mocking all endpoints -->
<bean id="mockAllEndpoints"
class="org.apache.camel.impl.InterceptSendToMockEndpointStrategy"/>
Then in your unit test you load the new XML file (test-camel-route.xml)
instead of camel-route.xml.
To only mock all Log endpoints you can define the pattern in the
constructor for the bean:
<bean id="mockAllEndpoints"
class="org.apache.camel.impl.InterceptSendToMockEndpointStrategy">
<constructor-arg index="0" value="log*"/>
</bean>
Testing with arrival times
Available as of Camel 2.7
The Mock endpoint stores the arrival time of the message as a property on
the Exchange.
Date time = exchange.getProperty(Exchange.RECEIVED_TIMESTAMP, Date.class);
C O O KB O O K
72
You can use this information to know when the message arrived on the mock.
But it also provides foundation to know the time interval between the
previous and next message arrived on the mock. You can use this to set
expectations using the arrives DSL on the Mock endpoint.
For example to say that the first message should arrive between 0-2
seconds before the next you can do:
mock.message(0).arrives().noLaterThan(2).seconds().beforeNext();
You can also define this as that 2nd message (0 index based) should arrive
no later than 0-2 seconds after the previous:
mock.message(1).arrives().noLaterThan(2).seconds().afterPrevious();
You can also use between to set a lower bound. For example suppose that it
should be between 1-4 seconds:
mock.message(1).arrives().between(1, 4).seconds().afterPrevious();
You can also set the expectation on all messages, for example to say that the
gap between them should be at most 1 second:
mock.allMessages().arrives().noLaterThan(1).seconds().beforeNext();
See Also
•
•
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
Spring Testing
Testing
TESTING
Testing is a crucial activity in any piece of software development or
integration. Typically Camel Riders use various different technologies wired
together in a variety of patterns with different expression languages together
with different forms of Bean Integration and Dependency Injection so its very
easy for things to go wrong!
. Testing is the crucial weapon to ensure that
things work as you would expect.
73
COOKBOOK
time units
In the example above we use seconds as the time unit, but Camel
offers milliseconds, and minutes as well.
Camel is a Java library so you can easily wire up tests in whatever unit
testing framework you use (JUnit 3.x, 4.x or TestNG). However the Camel
project has tried to make the testing of Camel as easy and powerful as
possible so we have introduced the following features.
Testing mechanisms
The following mechanisms are supported
Name
Description
Camel
Test
is a library letting you easily create Camel test cases using a
single Java class for all your configuration and routing without
using Spring or Guice for Dependency Injection which does not
require an in depth knowledge of Spring+SpringTest or Guice
Spring
Testing
uses Spring Test together with either XML or Java Config to
dependency inject your test classes
Guice
uses Guice to dependency inject your test classes
In all approaches the test classes look pretty much the same in that they all
reuse the Camel binding and injection annotations.
Camel Test Example
Here is the Camel Test example.
public class FilterTest extends CamelTestSupport {
@EndpointInject(uri = "mock:result")
protected MockEndpoint resultEndpoint;
@Produce(uri = "direct:start")
protected ProducerTemplate template;
public void testSendMatchingMessage() throws Exception {
String expectedBody = "<matched/>";
resultEndpoint.expectedBodiesReceived(expectedBody);
template.sendBodyAndHeader(expectedBody, "foo", "bar");
C O O KB O O K
74
resultEndpoint.assertIsSatisfied();
}
public void testSendNotMatchingMessage() throws Exception {
resultEndpoint.expectedMessageCount(0);
template.sendBodyAndHeader("<notMatched/>", "foo", "notMatchedHeaderValue");
resultEndpoint.assertIsSatisfied();
}
@Override
protected RouteBuilder createRouteBuilder() {
return new RouteBuilder() {
public void configure() {
from("direct:start").filter(header("foo").isEqualTo("bar")).to("mock:result");
}
};
}
}
Notice how it derives from the Camel helper class CamelTestSupport but
has no Spring or Guice dependency injection configuration but instead
overrides the createRouteBuilder() method.
Spring Test with XML Config Example
Here is the Spring Testing example using XML Config.
@ContextConfiguration
public class FilterTest extends AbstractJUnit38SpringContextTests {
@EndpointInject(uri = "mock:result")
protected MockEndpoint resultEndpoint;
@Produce(uri = "direct:start")
protected ProducerTemplate template;
@DirtiesContext
public void testSendMatchingMessage() throws Exception {
String expectedBody = "<matched/>";
resultEndpoint.expectedBodiesReceived(expectedBody);
template.sendBodyAndHeader(expectedBody, "foo", "bar");
resultEndpoint.assertIsSatisfied();
}
75
COOKBOOK
@DirtiesContext
public void testSendNotMatchingMessage() throws Exception {
resultEndpoint.expectedMessageCount(0);
template.sendBodyAndHeader("<notMatched/>", "foo", "notMatchedHeaderValue");
resultEndpoint.assertIsSatisfied();
}
}
Notice that we use @DirtiesContext on the test methods to force Spring
Testing to automatically reload the CamelContext after each test method this ensures that the tests don't clash with each other (e.g. one test method
sending to an endpoint that is then reused in another test method).
Also notice the use of @ContextConfiguration to indicate that by default
we should look for the FilterTest-context.xml on the classpath to configure
the test case which looks like this
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/
schema/beans/spring-beans.xsd
http://camel.apache.org/schema/spring http://camel.apache.org/schema/spring/
camel-spring.xsd
">
<camelContext xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="direct:start"/>
<filter>
<xpath>$foo = 'bar'</xpath>
<to uri="mock:result"/>
</filter>
</route>
</camelContext>
</beans>
Spring Test with Java Config Example
Here is the Spring Testing example using Java Config. For more information
see Spring Java Config.
C O O KB O O K
76
@ContextConfiguration(
locations =
"org.apache.camel.spring.javaconfig.patterns.FilterTest$ContextConfig",
loader = JavaConfigContextLoader.class)
public class FilterTest extends AbstractJUnit4SpringContextTests {
@EndpointInject(uri = "mock:result")
protected MockEndpoint resultEndpoint;
@Produce(uri = "direct:start")
protected ProducerTemplate template;
@DirtiesContext
@Test
public void testSendMatchingMessage() throws Exception {
String expectedBody = "<matched/>";
resultEndpoint.expectedBodiesReceived(expectedBody);
template.sendBodyAndHeader(expectedBody, "foo", "bar");
resultEndpoint.assertIsSatisfied();
}
@DirtiesContext
@Test
public void testSendNotMatchingMessage() throws Exception {
resultEndpoint.expectedMessageCount(0);
template.sendBodyAndHeader("<notMatched/>", "foo", "notMatchedHeaderValue");
resultEndpoint.assertIsSatisfied();
}
@Configuration
public static class ContextConfig extends SingleRouteCamelConfiguration {
@Bean
public RouteBuilder route() {
return new RouteBuilder() {
public void configure() {
from("direct:start").filter(header("foo").isEqualTo("bar")).to("mock:result");
}
};
}
}
}
This is similar to the XML Config example above except that there is no XML
file and instead the nested ContextConfig class does all of the
configuration; so your entire test case is contained in a single Java class. We
currently have to reference by class name this class in the
77
COOKBOOK
@ContextConfiguration which is a bit ugly. Please vote for SJC-238 to
address this and make Spring Test work more cleanly with Spring JavaConfig.
Its totally optional but for the ContextConfig implementation we derive
from SingleRouteCamelConfiguration which is a helper Spring Java Config
class which will configure the CamelContext for us and then register the
RouteBuilder we create.
Testing endpoints
Camel provides a number of endpoints which can make testing easier.
Name
Description
DataSet
For load & soak testing this endpoint provides a way to create
huge numbers of messages for sending to Components and
asserting that they are consumed correctly
Mock
For testing routes and mediation rules using mocks and allowing
assertions to be added to an endpoint
Test
Creates a Mock endpoint which expects to receive all the
message bodies that could be polled from the given underlying
endpoint
The main endpoint is the Mock endpoint which allows expectations to be
added to different endpoints; you can then run your tests and assert that
your expectations are met at the end.
Stubbing out physical transport technologies
If you wish to test out a route but want to avoid actually using a real physical
transport (for example to unit test a transformation route rather than
performing a full integration test) then the following endpoints can be useful.
Name
Description
Direct
Direct invocation of the consumer from the producer so that
single threaded (non-SEDA) in VM invocation is performed which
can be useful to mock out physical transports
SEDA
Delivers messages asynchonously to consumers via a
java.util.concurrent.BlockingQueue which is good for testing
asynchronous transports
Testing existing routes
Camel provides some features to aid during testing of existing routes where
you cannot or will not use Mock etc. For example you may have a production
C O O KB O O K
78
ready route which you want to test with some 3rd party API which sends
messages into this route.
Name
Description
NotifyBuilder
Allows you to be notified when a certain condition has
occurred. For example when the route has completed 5
messages. You can build complex expressions to match
your criteria when to be notified.
AdviceWith
Allows you to advice or enhance an existing route using a
RouteBuilder style. For example you can add interceptors
to intercept sending outgoing messages to assert those
messages are as expected.
CAMEL TEST
As a simple alternative to using Spring Testing or Guice the camel-test
module was introduced into the Camel 2.0 trunk so you can perform powerful
Testing of your Enterprise Integration Patterns easily.
Adding to your pom.xml
To get started using Camel Test you will need to add an entry to your
pom.xml
JUnit
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-test</artifactId>
<version>${camel-version}</version>
<scope>test</scope>
</dependency>
TestNG
Available as of Camel 2.8
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-testng</artifactId>
79
COOKBOOK
The camel-test JAR is using JUnit. There is an alternative cameltestng JAR (Camel 2.8 onwards) using the TestNG test framework.
<version>${camel-version}</version>
<scope>test</scope>
</dependency>
You might also want to add slf4j and log4j to ensure nice logging messages
(and maybe adding a log4j.properties file into your src/test/resources
directory).
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-log4j12</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<scope>test</scope>
</dependency>
Writing your test
You firstly need to derive from the class CamelTestSupport and typically
you will need to override the createRouteBuilder() method to create routes
to be tested.
Here is an example.
public class FilterTest extends CamelTestSupport {
@EndpointInject(uri = "mock:result")
protected MockEndpoint resultEndpoint;
@Produce(uri = "direct:start")
protected ProducerTemplate template;
public void testSendMatchingMessage() throws Exception {
String expectedBody = "<matched/>";
resultEndpoint.expectedBodiesReceived(expectedBody);
template.sendBodyAndHeader(expectedBody, "foo", "bar");
C O O KB O O K
80
resultEndpoint.assertIsSatisfied();
}
public void testSendNotMatchingMessage() throws Exception {
resultEndpoint.expectedMessageCount(0);
template.sendBodyAndHeader("<notMatched/>", "foo", "notMatchedHeaderValue");
resultEndpoint.assertIsSatisfied();
}
@Override
protected RouteBuilder createRouteBuilder() {
return new RouteBuilder() {
public void configure() {
from("direct:start").filter(header("foo").isEqualTo("bar")).to("mock:result");
}
};
}
}
Notice how you can use the various Camel binding and injection annotations
to inject individual Endpoint objects - particularly the Mock endpoints which
are very useful for Testing. Also you can inject producer objects such as
ProducerTemplate or some application code interface for sending messages
or invoking services.
JNDI
Camel uses a Registry to allow you to configure Component or Endpoint
instances or Beans used in your routes. If you are not using Spring or OSGi
then JNDI is used as the default registry implementation.
So you will also need to create a jndi.properties file in your src/test/
resources directory so that there is a default registry available to initialise
the CamelContext.
Here is an example jndi.properties file
java.naming.factory.initial = org.apache.camel.util.jndi.CamelInitialContextFactory
Dynamically assigning ports
Available as of Camel 2.7
Tests that use port numbers will fail if that port is already on use.
AvailablePortFinder provides methods for finding unused port numbers at
runtime.
81
COOKBOOK
// Get the next available port number starting from the default starting port of 1024
int port1 = AvailablePortFinder.getNextAvailable();
/*
* Get another port. Note that just getting a port number does not reserve it so
* we look starting one past the last port number we got.
*/
int port2 = AvailablePortFinder.getNextAvailable(port1 + 1);
See Also
• Testing
• Mock
SPRING TESTING
Testing is a crucial part of any development or integration work. The Spring
Framework offers a number of features that makes it easy to test while using
Spring for Inversion of Control which works with JUnit 3.x, JUnit 4.x or TestNG.
We can reuse Spring for IoC and the Camel Mock and Test endpoints to
create sophisticated integration tests that are easy to run and debug inside
your IDE.
For example here is a simple unit test
import
import
import
import
import
org.apache.camel.CamelContext;
org.apache.camel.component.mock.MockEndpoint;
org.springframework.beans.factory.annotation.Autowired;
org.springframework.test.context.ContextConfiguration;
org.springframework.test.context.junit38.AbstractJUnit38SpringContextTests;
@ContextConfiguration
public class MyCamelTest extends AbstractJUnit38SpringContextTests {
@Autowired
protected CamelContext camelContext;
public void testMocksAreValid() throws Exception {
MockEndpoint.assertIsSatisfied(camelContext);
}
}
This test will load a Spring XML configuration file called MyCamelTestcontext.xml from the classpath in the same package structure as the
MyCamelTest class and initialize it along with any Camel routes we define
inside it, then inject the CamelContext instance into our test case.
C O O KB O O K
82
For instance, like this maven folder layout:
src/main/java/com/mycompany/MyCamelTest.class
src/main/resources/com/mycompany/MyCamelTest-context.xml
You can overload the method createApplicationContext to provide the
Spring ApplicationContext that isn't following the above default. For instance:
protected AbstractXmlApplicationContext createApplicationContext() {
return new ClassPathXmlApplicationContext("/config/MySpringConfig.xml");
}
Then the test method will then run which invokes the
MockEndpoint.assertIsSatisfied(camelContext) method which asserts that all
of the Mock and Test endpoints have their expectations met.
xml}
Spring Test with Java Config Example
You can completely avoid using an XML configuration file by using Spring
Java Config.
Here is an example using Java Config.
@ContextConfiguration(
locations =
"org.apache.camel.spring.javaconfig.patterns.FilterTest$ContextConfig",
loader = JavaConfigContextLoader.class)
public class FilterTest extends AbstractJUnit4SpringContextTests {
@EndpointInject(uri = "mock:result")
protected MockEndpoint resultEndpoint;
@Produce(uri = "direct:start")
protected ProducerTemplate template;
@DirtiesContext
@Test
public void testSendMatchingMessage() throws Exception {
String expectedBody = "<matched/>";
resultEndpoint.expectedBodiesReceived(expectedBody);
template.sendBodyAndHeader(expectedBody, "foo", "bar");
resultEndpoint.assertIsSatisfied();
}
@DirtiesContext
83
COOKBOOK
@Test
public void testSendNotMatchingMessage() throws Exception {
resultEndpoint.expectedMessageCount(0);
template.sendBodyAndHeader("<notMatched/>", "foo", "notMatchedHeaderValue");
resultEndpoint.assertIsSatisfied();
}
@Configuration
public static class ContextConfig extends SingleRouteCamelConfiguration {
@Bean
public RouteBuilder route() {
return new RouteBuilder() {
public void configure() {
from("direct:start").filter(header("foo").isEqualTo("bar")).to("mock:result");
}
};
}
}
}
This is similar to the XML Config example above except that there is no XML
file and instead the nested ContextConfig class does all of the
configuration; so your entire test case is contained in a single Java class. We
currently have to reference by class name this class in the
@ContextConfiguration which is a bit ugly. Please vote for SJC-238 to
address this and make Spring Test work more cleanly with Spring JavaConfig.
Adding more Mock expectations
If you wish to programmatically add any new assertions to your test you can
easily do so with the following. Notice how we use @EndpointInject to inject a
Camel endpoint into our code then the Mock API to add an expectation on a
specific message.
@ContextConfiguration
public class MyCamelTest extends AbstractJUnit38SpringContextTests {
@Autowired
protected CamelContext camelContext;
@EndpointInject(uri = "mock:foo")
protected MockEndpoint foo;
public void testMocksAreValid() throws Exception {
// lets add more expectations
foo.message(0).header("bar").isEqualTo("ABC");
C O O KB O O K
84
MockEndpoint.assertIsSatisfied(camelContext);
}
}
Further processing the received messages
Sometimes once a Mock endpoint has received some messages you want to
then process them further to add further assertions that your test case
worked as you expect.
So you can then process the received message exchanges if you like...
@ContextConfiguration
public class MyCamelTest extends AbstractJUnit38SpringContextTests {
@Autowired
protected CamelContext camelContext;
@EndpointInject(uri = "mock:foo")
protected MockEndpoint foo;
public void testMocksAreValid() throws Exception {
// lets add more expectations...
MockEndpoint.assertIsSatisfied(camelContext);
// now lets do some further assertions
List<Exchange> list = foo.getReceivedExchanges();
for (Exchange exchange : list) {
Message in = exchange.getIn();
...
}
}
}
Sending and receiving messages
It might be that the Enterprise Integration Patterns you have defined in either
Spring XML or using the Java DSL do all of the sending and receiving and you
might just work with the Mock endpoints as described above. However
sometimes in a test case its useful to explicitly send or receive messages
directly.
To send or receive messages you should use the Bean Integration
mechanism. For example to send messages inject a ProducerTemplate using
the @EndpointInject annotation then call the various send methods on this
object to send a message to an endpoint. To consume messages use the
85
COOKBOOK
@MessageDriven annotation on a method to have the method invoked when
a message is received.
public class Foo {
@EndpointInject(uri="activemq:foo.bar")
ProducerTemplate producer;
public void doSomething() {
// lets send a message!
producer.sendBody("<hello>world!</hello>");
}
// lets consume messages from the 'cheese' queue
@MessageDriven(uri="activemq:cheese")
public void onCheese(String name) {
...
}
}
See Also
• a real example test case using Mock and Spring along with its Spring
XML
• Bean Integration
• Mock endpoint
• Test endpoint
CAMEL GUICE
As of 1.5 we now have support for Google Guice as a dependency injection
framework. To use it just be dependent on camel-guice.jar which also
depends on the following jars.
Dependency Injecting Camel with Guice
The GuiceCamelContext is designed to work nicely inside Guice. You then
need to bind it using some Guice Module.
The camel-guice library comes with a number of reusable Guice Modules
you can use if you wish - or you can bind the GuiceCamelContext yourself in
your own module.
• CamelModule is the base module which binds the
GuiceCamelContext but leaves it up you to bind the RouteBuilder
instances
C O O KB O O K
86
• CamelModuleWithRouteTypes extends CamelModule so that in the
constructor of the module you specify the RouteBuilder classes or
instances to use
• CamelModuleWithMatchingRoutes extends CamelModule so that all
bound RouteBuilder instances will be injected into the CamelContext
or you can supply an optional Matcher to find RouteBuilder instances
matching some kind of predicate.
So you can specify the exact RouteBuilder instances you want
Injector injector = Guice.createInjector(new
CamelModuleWithRouteTypes(MyRouteBuilder.class, AnotherRouteBuilder.class));
// if required you can lookup the CamelContext
CamelContext camelContext = injector.getInstance(CamelContext.class);
Or inject them all
Injector injector = Guice.createInjector(new CamelModuleWithRouteTypes());
// if required you can lookup the CamelContext
CamelContext camelContext = injector.getInstance(CamelContext.class);
You can then use Guice in the usual way to inject the route instances or any
other dependent objects.
Bootstrapping with JNDI
A common pattern used in J2EE is to bootstrap your application or root
objects by looking them up in JNDI. This has long been the approach when
working with JMS for example - looking up the JMS ConnectionFactory in JNDI
for example.
You can follow a similar pattern with Guice using the GuiceyFruit JNDI
Provider which lets you bootstrap Guice from a jndi.properties file which
can include the Guice Modules to create along with environment specific
properties you can inject into your modules and objects.
If the jndi.properties is conflict with other component, you can specify
the jndi properties file name in the Guice Main with option -j or -jndiProperties
with the properties file location to let Guice Main to load right jndi properties
file.
Configuring Component, Endpoint or RouteBuilder instances
You can use Guice to dependency inject whatever objects you need to create,
be it an Endpoint, Component, RouteBuilder or arbitrary bean used within a
route.
87
COOKBOOK
The easiest way to do this is to create your own Guice Module class which
extends one of the above module classes and add a provider method for
each object you wish to create. A provider method is annotated with
@Provides as follows
public class MyModule extends CamelModuleWithMatchingRoutes {
@Provides
@JndiBind("jms")
JmsComponent jms(@Named("activemq.brokerURL") String brokerUrl) {
return JmsComponent.jmsComponent(new ActiveMQConnectionFactory(brokerUrl));
}
}
You can optionally annotate the method with @JndiBind to bind the object to
JNDI at some name if the object is a component, endpoint or bean you wish
to refer to by name in your routes.
You can inject any environment specific properties (such as URLs, machine
names, usernames/passwords and so forth) from the jndi.properties file
easily using the @Named annotation as shown above. This allows most of
your configuration to be in Java code which is typesafe and easily
refactorable - then leaving some properties to be environment specific (the
jndi.properties file) which you can then change based on development,
testing, production etc.
Creating multiple RouteBuilder instances per type
It is sometimes useful to create multiple instances of a particular
RouteBuilder with different configurations.
To do this just create multiple provider methods for each configuration; or
create a single provider method that returns a collection of RouteBuilder
instances.
For example
import org.apache.camel.guice.CamelModuleWithMatchingRoutes;
import com.google.common.collect.Lists;
public class MyModule extends CamelModuleWithMatchingRoutes {
@Provides
@JndiBind("foo")
Collection<RouteBuilder> foo(@Named("fooUrl") String fooUrl) {
return Lists.newArrayList(new MyRouteBuilder(fooUrl), new
MyRouteBuilder("activemq:CheeseQueue"));
}
}
C O O KB O O K
88
See Also
• there are a number of Examples you can look at to see Guice and
Camel being used such as Guice JMS Example
• Guice Maven Plugin for running your Guice based routes via Maven
TEMPLATING
When you are testing distributed systems its a very common requirement to
have to stub out certain external systems with some stub so that you can
test other parts of the system until a specific system is available or written
etc.
A great way to do this is using some kind of Template system to generate
responses to requests generating a dynamic message using a mostly-static
body.
There are a number of templating components you could use
• FreeMarker
• Scalate
• StringTemplate
• Velocity
• XQuery
• XSLT
Example
Here's a simple example showing how we can respond to InOut requests on
the My.Queue queue on ActiveMQ with a template generated response. The
reply would be sent back to the JMSReplyTo Destination.
from("activemq:My.Queue").
to("velocity:com/acme/MyResponse.vm");
If you want to use InOnly and consume the message and send it to another
destination you could use
from("activemq:My.Queue").
to("velocity:com/acme/MyResponse.vm").
to("activemq:Another.Queue");
See Also
• Mock for details of mock endpoint testing (as opposed to template
based stubs).
89
COOKBOOK
DATABASE
Camel can work with databases in a number of different ways. This
document tries to outline the most common approaches.
Database endpoints
Camel provides a number of different endpoints for working with databases
• JPA for working with hibernate, openjpa or toplink. When consuming
from the endpoints entity beans are read (and deleted/updated to
mark as processed) then when producing to the endpoints they are
written to the database (via insert/update).
• iBATIS similar to the above but using Apache iBATIS
• JDBC similar though using explicit SQL
Database pattern implementations
Various
•
•
•
patterns can work with databases as follows
Idempotent Consumer
Aggregator
BAM for business activity monitoring
PARALLEL PROCESSING AND ORDERING
It is a common requirement to want to use parallel processing of messages
for throughput and load balancing, while at the same time process certain
kinds of messages in order.
How to achieve parallel processing
You can send messages to a number of Camel Components to achieve
parallel processing and load balancing such as
• SEDA for in-JVM load balancing across a thread pool
• ActiveMQ or JMS for distributed load balancing and parallel
processing
• JPA for using the database as a poor mans message broker
When processing messages concurrently, you should consider ordering and
concurrency issues. These are described below
Concurrency issues
Note that there is no concurrency or locking issue when using ActiveMQ, JMS
or SEDA by design; they are designed for highly concurrent use. However
C O O KB O O K
90
there are possible concurrency issues in the Processor of the messages i.e.
what the processor does with the message?
For example if a processor of a message transfers money from one
account to another account; you probably want to use a database with
pessimistic locking to ensure that operation takes place atomically.
Ordering issues
As soon as you send multiple messages to different threads or processes you
will end up with an unknown ordering across the entire message stream as
each thread is going to process messages concurrently.
For many use cases the order of messages is not too important. However
for some applications this can be crucial. e.g. if a customer submits a
purchase order version 1, then amends it and sends version 2; you don't
want to process the first version last (so that you loose the update). Your
Processor might be clever enough to ignore old messages. If not you need to
preserve order.
Recommendations
This topic is large and diverse with lots of different requirements; but from a
high level here are our recommendations on parallel processing, ordering
and concurrency
• for distributed locking, use a database by default, they are very good
at it
• to preserve ordering across a JMS queue consider using Exclusive
Consumers in the ActiveMQ component
• even better are Message Groups which allows you to preserve
ordering across messages while still offering parallelisation via the
JMSXGrouopID header to determine what can be parallelized
• if you receive messages out of order you could use the Resequencer
to put them back together again
A good rule of thumb to help reduce ordering problems is to make sure each
single can be processed as an atomic unit in parallel (either without
concurrency issues or using say, database locking); or if it can't, use a
Message Group to relate the messages together which need to be processed
in order by a single thread.
Using Message Groups with Camel
To use a Message Group with Camel you just need to add a header to the
output JMS message based on some kind of Correlation Identifier to correlate
91
COOKBOOK
messages which should be processed in order by a single thread - so that
things which don't correlate together can be processed concurrently.
For example the following code shows how to create a message group
using an XPath expression taking an invoice's product code as the Correlation
Identifier
from("activemq:a").setHeader("JMSXGroupID", xpath("/invoice/
productCode")).to("activemq:b");
You can of course use the Xml Configuration if you prefer
ASYNCHRONOUS PROCESSING
Overview
Camel supports a more complex asynchronous processing model. The
asynchronous processors implement the AsyncProcessor interface which is
derived from the more synchronous Processor interface. There are
advantages and disadvantages when using asynchronous processing when
compared to using the standard synchronous processing model.
Advantages:
• Processing routes that are composed fully of asynchronous
processors do not use up threads waiting for processors to complete
on blocking calls. This can increase the scalability of your system by
reducing the number of threads needed to process the same
workload.
• Processing routes can be broken up into SEDA processing stages
where different thread pools can process the different stages. This
means that your routes can be processed concurrently.
Disadvantages:
• Implementing asynchronous processors is more complex than
implementing the synchronous versions.
When to Use
We recommend that processors and components be implemented the more
simple synchronous APIs unless you identify a performance of scalability
requirement that dictates otherwise. A Processor whose process() method
blocks for a long time would be good candidates for being converted into an
asynchronous processor.
C O O KB O O K
92
Supported versions
The information on this page applies for the Camel 1.x and Camel
2.4 onwards. In Camel 1.x the asynchronous processing is only
implemented for JBI where as in Camel 2.4 onwards we have
implemented it in many other areas. See more at Asynchronous
Routing Engine.
Interface Details
public interface AsyncProcessor extends Processor {
boolean process(Exchange exchange, AsyncCallback callback);
}
The AsyncProcessor defines a single process() method which is very similar
to it's synchronous Processor.process() brethren. Here are the differences:
• A non-null AsyncCallback MUST be supplied which will be notified
when the exchange processing is completed.
• It MUST not throw any exceptions that occurred while processing the
exchange. Any such exceptions must be stored on the exchange's
Exception property.
• It MUST know if it will complete the processing synchronously or
asynchronously. The method will return true if it does complete
synchronously, otherwise it returns false.
• When the processor has completed processing the exchange, it must
call the callback.done(boolean sync) method. The sync
parameter MUST match the value returned by the process()
method.
Implementing Processors that Use the AsyncProcessor API
All processors, even synchronous processors that do not implement the
AsyncProcessor interface, can be coerced to implement the AsyncProcessor
interface. This is usually done when you are implementing a Camel
component consumer that supports asynchronous completion of the
exchanges that it is pushing through the Camel routes. Consumers are
provided a Processor object when created. All Processor object can be
coerced to a AsyncProcessor using the following API:
Processor processor = ...
AsyncProcessor asyncProcessor = AsyncProcessorTypeConverter.convert(processor);
93
COOKBOOK
For a route to be fully asynchronous and reap the benefits to lower Thread
usage, it must start with the consumer implementation making use of the
asynchronous processing API. If it called the synchronous process() method
instead, the consumer's thread would be forced to be blocked and in use for
the duration that it takes to process the exchange.
It is important to take note that just because you call the asynchronous
API, it does not mean that the processing will take place asynchronously. It
only allows the possibility that it can be done without tying up the caller's
thread. If the processing happens asynchronously is dependent on the
configuration of the Camel route.
Normally, the the process call is passed in an inline inner AsyncCallback
class instance which can reference the exchange object that was declared
final. This allows it to finish up any post processing that is needed when the
called processor is done processing the exchange. See below for an example.
final Exchange exchange = ...
AsyncProcessor asyncProcessor = ...
asyncProcessor.process(exchange, new AsyncCallback() {
public void done(boolean sync) {
if (exchange.isFailed()) {
... // do failure processing.. perhaps rollback etc.
} else {
... // processing completed successfully, finish up
// perhaps commit etc.
}
}
});
Asynchronous Route Sequence Scenarios
Now that we have understood the interface contract of the AsyncProcessor,
and have seen how to make use of it when calling processors, lets looks a
what the thread model/sequence scenarios will look like for some sample
routes.
The Jetty component's consumers support async processing by using
continuations. Suffice to say it can take a http request and pass it to a camel
route for async processing. If the processing is indeed async, it uses Jetty
continuation so that the http request is 'parked' and the thread is released.
Once the camel route finishes processing the request, the jetty component
uses the AsyncCallback to tell Jetty to 'un-park' the request. Jetty un-parks
the request, the http response returned using the result of the exchange
processing.
C O O KB O O K
94
Notice that the jetty continuations feature is only used "If the processing is
indeed async". This is why AsyncProcessor.process() implementations MUST
accurately report if request is completed synchronously or not.
The jhc component's producer allows you to make HTTP requests and
implement the AsyncProcessor interface. A route that uses both the jetty
asynchronous consumer and the jhc asynchronous producer will be a fully
asynchronous route and has some nice attributes that can be seen if we take
a look at a sequence diagram of the processing route. For the route:
from("jetty:http://localhost:8080/service").to("jhc:http://localhost/service-impl");
The sequence diagram would look something like this:
The diagram simplifies things by making it looks like processors implement
the AsyncCallback interface when in reality the AsyncCallback interfaces are
inline inner classes, but it illustrates the processing flow and shows how 2
separate threads are used to complete the processing of the original http
request. The first thread is synchronous up until processing hits the jhc
producer which issues the http request. It then reports that the exchange
processing will complete async since it will use a NIO to complete getting the
response back. Once the jhc component has received a full response it uses
AsyncCallback.done() method to notify the caller. These callback
notifications continue up until it reaches the original jetty consumer which
then un-parks the http request and completes it by providing the response.
95
COOKBOOK
Mixing Synchronous and Asynchronous Processors
It is totally possible and reasonable to mix the use of synchronous and
asynchronous processors/components. The pipeline processor is the
backbone of a Camel processing route. It glues all the processing steps
together. It is implemented as an AsyncProcessor and supports interleaving
synchronous and asynchronous processors as the processing steps in the
pipeline.
Lets say we have 2 custom processors, MyValidator and MyTransformation,
both of which are synchronous processors. Lets say we want to load file from
the data/in directory validate them with the MyValidator() processor,
Transform them into JPA java objects using MyTransformation and then insert
them into the database using the JPA component. Lets say that the
transformation process takes quite a bit of time and we want to allocate 20
threads to do parallel transformations of the input files. The solution is to
make use of the thread processor. The thread is AsyncProcessor that forces
subsequent processing in asynchronous thread from a thread pool.
The route might look like:
from("file:data/in").process(new MyValidator()).thread(20).process(new
MyTransformation()).to("jpa:PurchaseOrder");
The sequence diagram would look something like this:
You would actually have multiple threads executing the 2nd part of the
thread sequence.
C O O KB O O K
96
Staying synchronous in an AsyncProcessor
Generally speaking you get better throughput processing when you process
things synchronously. This is due to the fact that starting up an asynchronous
thread and doing a context switch to it adds a little bit of of overhead. So it is
generally encouraged that AsyncProcessors do as much work as they can
synchronously. When they get to a step that would block for a long time, at
that point they should return from the process call and let the caller know
that it will be completing the call asynchronously.
IMPLEMENTING VIRTUAL TOPICS ON OTHER JMS
PROVIDERS
ActiveMQ supports Virtual Topics since durable topic subscriptions kinda suck
(see this page for more detail) mostly since they don't support Competing
Consumers.
Most folks want Queue semantics when consuming messages; so that you
can support Competing Consumers for load balancing along with things like
Message Groups and Exclusive Consumers to preserve ordering or partition
the queue across consumers.
However if you are using another JMS provider you can implement Virtual
Topics by switching to ActiveMQ
or you can use the following Camel
pattern.
First here's the ActiveMQ approach.
• send to activemq:topic:VirtualTopic.Orders
• for consumer A consume from
activemq:Consumer.A.VirtualTopic.Orders
When using another message broker use the following pattern
• send to jms:Orders
• add this route with a to() for each logical durable topic subscriber
from("jms:Orders").to("jms:Consumer.A", "jms:Consumer.B", ...);
• for consumer A consume from jms:Consumer.A
WHAT'S THE CAMEL TRANSPORT FOR CXF
In CXF you offer or consume a webservice by defining it´s address. The first
part of the address specifies the protocol to use. For example
address="http://localhost:90000" in an endpoint configuration means your
service will be offered using the http protocol on port 9000 of localhost.
When you integrate Camel Tranport into CXF you get a new transport
97
COOKBOOK
"camel". So you can specify address="camel://direct:MyEndpointName" to
bind the CXF service address to a camel direct endpoint.
Technically speaking Camel transport for CXF is a component which
implements the CXF transport API with the Camel core library. This allows you
to use camel´s routing engine and integration patterns support smoothly
together with your CXF services.
INTEGRATE CAMEL INTO CXF TRANSPORT LAYER
To include the Camel Tranport into your CXF bus you use the
CamelTransportFactory. You can do this in Java as well as in Spring.
Setting up the Camel Transport in Spring
You can use the following snippet in your applicationcontext if you want to
configure anything special. If you only want to activate the camel transport
you do not have to do anything in your application context. As soon as you
include the camel-cxf jar in your app cxf will scan the jar and load a
CamelTransportFactory for you.
<bean class="org.apache.camel.component.cxf.transport.CamelTransportFactory">
<property name="bus" ref="cxf" />
<property name="camelContext" ref="camelContext" />
<!-- checkException new added in Camel 2.1 and Camel 1.6.2 -->
<!-- If checkException is true , CamelDestination will check the outMessage's
exception and set it into camel exchange. You can also override this value
in CamelDestination's configuration. The default value is false.
This option should be set true when you want to leverage the camel's error
handler to deal with fault message -->
<property name="checkException" value="true" />
<property name="transportIds">
<list>
<value>http://cxf.apache.org/transports/camel</value>
</list>
</property>
</bean>
Integrating the Camel Transport in a programmatic way
Camel transport provides a setContext method that you could use to set the
Camel context into the transport factory. If you want this factory take effect,
you need to register the factory into the CXF bus. Here is a full example for
you.
C O O KB O O K
98
import
import
import
import
...
org.apache.cxf.Bus;
org.apache.cxf.BusFactory;
org.apache.cxf.transport.ConduitInitiatorManager;
org.apache.cxf.transport.DestinationFactoryManager;
BusFactory bf = BusFactory.newInstance();
Bus bus = bf.createBus();
CamelTransportFactory camelTransportFactory = new CamelTransportFactory();
camelTransportFactory.setCamelContext(context)
// register the conduit initiator
ConduitInitiatorManager cim = bus.getExtension(ConduitInitiatorManager.class);
cim.registerConduitInitiator(CamelTransportFactory.TRANSPORT_ID,
camelTransportFactory);
// register the destination factory
DestinationFactoryManager dfm = bus.getExtension(DestinationFactoryManager.class);
dfm.registerDestinationFactory(CamelTransportFactory.TRANSPORT_ID,
camelTransportFactory);
// set or bus as the default bus for cxf
BusFactory.setDefaultBus(bus);
CONFIGURE THE DESTINATION AND CONDUIT
Namespace
The elements used to configure an Camel transport endpoint are defined in
the namespace http://cxf.apache.org/transports/camel. It is commonly
referred to using the prefix camel. In order to use the Camel transport
configuration elements you will need to add the lines shown below to the
beans element of your endpoint's configuration file. In addition, you will need
to add the configuration elements' namespace to the xsi:schemaLocation
attribute.
Listing 13. Adding the Configuration Namespace
<beans ...
xmlns:camel="http://cxf.apache.org/transports/camel
...
xsi:schemaLocation="...
http://cxf.apache.org/transports/camel
http://cxf.apache.org/transports/camel.xsd
...>
The destination element
You configure an Camel transport server endpoint using the
camel:destination element and its children. The camel:destination
99
COOKBOOK
element takes a single attribute, name, the specifies the WSDL port element
that corresponds to the endpoint. The value for the name attribute takes the
form portQName.camel-destination. The example below shows the
camel:destination element that would be used to add configuration for an
endpoint that was specified by the WSDL fragment <port
binding="widgetSOAPBinding" name="widgetSOAPPort> if the endpoint's
target namespace was http://widgets.widgetvendor.net.
Listing 14. camel:destination Element
...
<camel:destination name="{http://widgets/
widgetvendor.net}widgetSOAPPort.http-destination>
<camelContext id="context" xmlns="http://activemq.apache.org/camel/schema/spring">
<route>
<from uri="direct:EndpointC" />
<to uri="direct:EndpointD" />
</route>
</camelContext>
</camel:destination>
...
The camel:destination element has a number of child elements that
specify configuration information. They are described below.
Element
Description
camelspring:camelContext
You can specify the camel context in the camel
destination
camel:camelContextRef
The camel context id which you want inject
into the camel destination
The conduit element
You configure an Camel transport client using the camel:conduit element
and its children. The camel:conduit element takes a single attribute, name,
that specifies the WSDL port element that corresponds to the endpoint. The
value for the name attribute takes the form portQName.camel-conduit. For
example, the code below shows the camel:conduit element that would be
used to add configuration for an endpoint that was specified by the WSDL
fragment <port binding="widgetSOAPBinding" name="widgetSOAPPort> if
the endpoint's target namespace was http://widgets.widgetvendor.net.
Listing 15. http-conf:conduit Element
...
<camelContext id="conduit_context" xmlns="http://activemq.apache.org/camel/schema/
C O O KB O O K
100
spring">
<route>
<from uri="direct:EndpointA" />
<to uri="direct:EndpointB" />
</route>
</camelContext>
<camel:conduit name="{http://widgets/widgetvendor.net}widgetSOAPPort.camel-conduit">
<camel:camelContextRef>conduit_context</camel:camelContextRef>
</camel:conduit>
<camel:conduit name="*.camel-conduit">
<!-- you can also using the wild card to specify the camel-conduit that you want to
configure -->
...
</camel:conduit>
...
The camel:conduit element has a number of child elements that specify
configuration information. They are described below.
Element
Description
camelspring:camelContext
You can specify the camel context in the camel
conduit
camel:camelContextRef
The camel context id which you want inject
into the camel conduit
EXAMPLE USING CAMEL AS A LOAD BALANCER FOR CXF
This example show how to use the camel load balance feature in CXF, and
you need load the configuration file in CXF and publish the endpoints on the
address "camel://direct:EndpointA" and "camel://direct:EndpointB"
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:camel="http://cxf.apache.org/transports/camel"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://cxf.apache.org/transports/camel http://cxf.apache.org/transports/
camel.xsd
http://camel.apache.org/schema/cxf http://camel.apache.org/schema/cxf/
cxfEndpoint.xsd
http://camel.apache.org/schema/spring http://camel.apache.org/schema/spring/
camel-spring.xsd
">
101
COOKBOOK
<bean id = "roundRobinRef"
class="org.apache.camel.processor.loadbalancer.RoundRobinLoadBalancer" />
<camelContext id="dest_context" xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="jetty:http://localhost:9091/GreeterContext/GreeterPort"/>
<loadBalance ref="roundRobinRef">
<to uri="direct:EndpointA"/>
<to uri="direct:EndpointB"/>
</loadBalance>
</route>
</camelContext>
<!-- Inject the camel context to the Camel transport's destination -->
<camel:destination name="{http://apache.org/
hello_world_soap_http}CamelPort.camel-destination">
<camel:camelContextRef>dest_context</camel:camelContextRef>
</camel:destination>
</beans>
COMPLETE HOWTO AND EXAMPLE FOR ATTACHING
CAMEL TO CXF
Introduction
Better JMS Transport for CXF Webservice using Apache CamelÂ
When sending an Exchange to an Endpoint you can either use a Route or a
ProducerTemplate. This works fine in many scenarios. However you may
need to guarantee that an exchange is delivered to the same endpoint that
you delivered a previous exchange on. For example in the case of delivering
a batch of exchanges to a MINA socket you may need to ensure that they are
all delivered through the same socket connection. Furthermore once the
batch of exchanges have been delivered the protocol requirements may be
such that you are responsible for closing the socket.
Using a Producer
To achieve fine grained control over sending exchanges you will need to
program directly to a Producer. Your code will look similar to:
IN TR O D U C TIO N
102
CamelContext camelContext = ...
// Obtain an endpoint and create the producer we will be using.
Endpoint endpoint = camelContext.getEndpoint("someuri:etc");
Producer producer = endpoint.createProducer();
producer.start();
try {
// For each message to send...
Object requestMessage = ...
Exchange exchangeToSend = producer.createExchange();
exchangeToSend().setBody(requestMessage);
producer.process(exchangeToSend);
...
} finally {
// Tidy the producer up.
producer.stop();
}
In the case of using Apache MINA the producer.stop() invocation will cause
the socket to be closed.
103
U SIN G A P R O D U C E R
Tutorials
There now follows the documentation on camel tutorials
• OAuth Tutorial
This tutorial demonstrates how to implement OAuth for a web
application with Camel's gauth component. The sample application of
this tutorial is also online at http://gauthcloud.appspot.com/
• Tutorial for Camel on Google App Engine
This tutorial demonstrates the usage of the Camel Components for
Google App Engine. The sample application of this tutorial is also
online at http://camelcloud.appspot.com/
• Tutorial on Spring Remoting with JMS
This tutorial is focused on different techniques with Camel for ClientServer communication.
• Report Incident - This tutorial introduces Camel steadily and is based
on a real life integration problem
This is a very long tutorial beginning from the start; its for entry level
to Camel. Its based on a real life integration, showing how Camel can
be introduced in an existing solution. We do this in baby steps. The
tutorial is currently work in progress, so check it out from time to
time. The tutorial explains some of the inner building blocks Camel
uses under the covers. This is good knowledge to have when you
start using Camel on a higher abstract level where it can do wonders
in a few lines of routing DSL.
• Using Camel with ServiceMix a tutorial on using Camel inside Apache
ServiceMix.
• Better JMS Transport for CXF Webservice using Apache Camel
Describes how to use the Camel Transport for CXF to attach a CXF
Webservice to a JMS Queue
• Tutorial how to use good old Axis 1.4 with Camel
This tutorial shows that Camel does work with the good old
frameworks such as AXIS that is/was widely used for WebService.
• Tutorial on using Camel in a Web Application
This tutorial gives an overview of how to use Camel inside Tomcat,
Jetty or any other servlet engine
• Tutorial on Camel 1.4 for Integration
Another real-life scenario. The company sells widgets, with a
somewhat unique business process (their customers periodically
report what they've purchased in order to get billed). However every
customer uses a different data format and protocol. This tutorial goes
T U T O R IA L S
104
•
•
•
•
through the process of integrating (and testing!) several customers
and their electronic reporting of the widgets they've bought, along
with the company's response.
Tutorial how to build a Service Oriented Architecture using Camel
with OSGI - Updated 20/11/2009
The tutorial has been designed in two parts. The first part introduces
basic concept to create a simple SOA solution using Camel and OSGI
and deploy it in a OSGI Server like Apache Felix Karaf and Spring DM
Server while the second extends the ReportIncident tutorial part 4 to
show How we can separate the different layers (domain, service, ...)
of an application and deploy them in separate bundles. The Web
Application has also be modified in order to communicate to the OSGI
bundles.
Fuse IDE for Camel - (currently beta) includes a number of easy to
follow tutorials.
FuseSource Webinars
There are a number of tutorials available for streaming from the
FuseSource site.
Examples
While not actual tutorials you might find working through the source
of the various Examples useful
TUTORIAL ON SPRING REMOTING WITH JMS
Â
PREFACE
This tutorial aims to guide the reader through the stages of creating a project
which uses Camel to facilitate the routing of messages from a JMS queue to a
Spring service. The route works in a synchronous fashion returning a
response to the client.
• Tutorial on Spring Remoting with JMS
• Preface
• Prerequisites
• Distribution
• About
• Create the Camel Project
• Update the POM with Dependencies
• Writing the Server
• Create the Spring Service
• Define the Camel Routes
105
T U T O R IAL S
Thanks
This tutorial was kindly donated to Apache Camel by Martin Gilday.
•
•
•
•
•
•
•
•
•
•
•
Configure Spring
AOP Enabled Server
Run the Server
Writing The Clients
Client Using The ProducerTemplate
Client Using Spring Remoting
Client Using Message Endpoint EIP Pattern
Run the Clients
Using the Camel Maven Plugin
Using Camel JMX
See Also
PREREQUISITES
This tutorial uses Maven to setup the Camel project and for dependencies for
artifacts.
DISTRIBUTION
This sample is distributed with the Camel distribution as examples/camelexample-spring-jms.
ABOUT
This tutorial is a simple example that demonstrates more the fact how well
Camel is seamless integrated with Spring to leverage the best of both worlds.
This sample is client server solution using JMS messaging as the transport.
The sample has two flavors of servers and also for clients demonstrating
different techniques for easy communication.
The Server is a JMS message broker that routes incoming messages to a
business service that does computations on the received message and
returns a response.
The EIP patterns used in this sample are:
Pattern
Description
T U T O R IA L S
106
Message
Channel
We need a channel so the Clients can communicate with the
server.
Message
The information is exchanged using the Camel Message
interface.
Message
Translator
This is where Camel shines as the message exchange
between the Server and the Clients are text based strings with
numbers. However our business service uses int for numbers.
So Camel can do the message translation automatically.
Message
Endpoint
It should be easy to send messages to the Server from the the
clients. This is archived with Camels powerful Endpoint
pattern that even can be more powerful combined with Spring
remoting. The tutorial have clients using each kind of
technique for this.
Point to
Point
Channel
We using JMS queues so there are only one receive of the
message exchange
Event
Driven
Consumer
Yes the JMS broker is of course event driven and only reacts
when the client sends a message to the server.
We use the following Camel components:
Component
Description
ActiveMQ
We use Apache ActiveMQ as the JMS broker on the Server
side
Bean
We use the bean binding to easily route the messages to
our business service. This is a very powerful component in
Camel.
File
In the AOP enabled Server we store audit trails as files.
JMS
Used for the JMS messaging
CREATE THE CAMEL PROJECT
mvn archetype:create -DgroupId=org.example -DartifactId=CamelWithJmsAndSpring
107
T U T O R IAL S
For the purposes of the tutorial a single Maven project will be used
for both the client and server. Ideally you would break your
application down into the appropriate components.
Update the POM with Dependencies
First we need to have dependencies for the core Camel jars, its spring, jms
components and finally ActiveMQ as the message broker.
<!-- required by both client and server -->
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-core</artifactId>
</dependency>
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-jms</artifactId>
</dependency>
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-spring</artifactId>
</dependency>
<dependency>
<groupId>org.apache.activemq</groupId>
<artifactId>activemq-camel</artifactId>
</dependency>
As we use spring xml configuration for the ActiveMQ JMS broker we need this
dependency:
<!-- xbean is required for ActiveMQ broker configuration in the spring xml file -->
<dependency>
<groupId>org.apache.xbean</groupId>
<artifactId>xbean-spring</artifactId>
</dependency>
And dependencies for the AOP enable server example. These dependencies
are of course only needed if you need full blown AOP stuff using AspejctJ with
bytecode instrumentation.
<!-- required jars for aspectj AOP support -->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-aop</artifactId>
<version>${spring-version}</version>
</dependency>
<dependency>
T U T O R IA L S
108
<groupId>org.aspectj</groupId>
<artifactId>aspectjrt</artifactId>
<version>1.6.2</version>
</dependency>
<dependency>
<groupId>org.aspectj</groupId>
<artifactId>aspectjweaver</artifactId>
<version>1.6.2</version>
</dependency>
<dependency>
<groupId>cglib</groupId>
<artifactId>cglib-nodep</artifactId>
<version>2.1_3</version>
</dependency>
WRITING THE SERVER
Create the Spring Service
For this example the Spring service (= our business service) on the server
will be a simple multiplier which trebles in the received value.
public interface Multiplier {
/**
* Multiplies the given number by a pre-defined constant.
*
* @param originalNumber The number to be multiplied
* @return The result of the multiplication
*/
int multiply(int originalNumber);
}
And the implementation of this service is:
@Service(value = "multiplier")
public class Treble implements Multiplier {
public int multiply(final int originalNumber) {
return originalNumber * 3;
}
}
109
T U T O R IAL S
Notice that this class has been annotated with the @Service spring
annotation. This ensures that this class is registered as a bean in the registry
with the given name multiplier.
Define the Camel Routes
public class ServerRoutes extends RouteBuilder {
@Override
public void configure() throws Exception {
// route from the numbers queue to our business that is a spring bean
registered with the id=multiplier
// Camel will introspect the multiplier bean and find the best candidate of
the method to invoke.
// You can add annotations etc to help Camel find the method to invoke.
// As our multiplier bean only have one method its easy for Camel to find the
method to use.
from("jms:queue:numbers").to("multiplier");
// Camel has several ways to configure the same routing, we have defined some
of them here below
// as above but with the bean: prefix
//from("jms:queue:numbers").to("bean:multiplier");
// beanRef is using explicity bean bindings to lookup the multiplier bean and
invoke the multiply method
//from("jms:queue:numbers").beanRef("multiplier", "multiply");
// the same as above but expressed as a URI configuration
//from("activemq:queue:numbers").to("bean:multiplier?methodName=multiply");
}
}
This defines a Camel route from the JMS queue named numbers to the
Spring bean named multiplier. Camel will create a consumer to the JMS
queue which forwards all received messages onto the the Spring bean, using
the method named multiply.
Configure Spring
The Spring config file is placed under META-INF/spring as this is the default
location used by the Camel Maven Plugin, which we will later use to run our
server.
First we need to do the standard scheme declarations in the top. In the
camel-server.xml we are using spring beans as the default bean: namespace
and springs context:. For configuring ActiveMQ we use broker: and for
Camel we of course have camel:. Notice that we don't use version numbers
T U T O R IA L S
110
for the camel-spring schema. At runtime the schema is resolved in the Camel
bundle. If we use a specific version number such as 1.4 then its IDE friendly
as it would be able to import it and provide smart completion etc. See Xml
Reference for further details.
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:camel="http://camel.apache.org/schema/spring"
xmlns:broker="http://activemq.apache.org/schema/core"
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/
schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context http://www.springframework.org/
schema/context/spring-context.xsd
http://camel.apache.org/schema/spring http://camel.apache.org/schema/spring/
camel-spring.xsd
http://activemq.apache.org/schema/core http://activemq.apache.org/schema/core/
activemq-core-5.5.0.xsd">
We use Spring annotations for doing IoC dependencies and its componentscan features comes to the rescue as it scans for spring annotations in the
given package name:
<!-- let Spring do its IoC stuff in this package -->
<context:component-scan base-package="org.apache.camel.example.server"/>
Camel will of course not be less than Spring in this regard so it supports a
similar feature for scanning of Routes. This is configured as shown below.
Notice that we also have enabled the JMXAgent so we will be able to
introspect the Camel Server with a JMX Console.
<!-- declare a camel context that scans for classes that is RouteBuilder
in the package org.apache.camel.example.server -->
<camel:camelContext id="camel-server">
<camel:package>org.apache.camel.example.server</camel:package>
<!-- enable JMX connector so we can connect to the server and browse mbeans -->
<!-- Camel will log at INFO level the service URI to use for connecting with
jconsole -->
<camel:jmxAgent id="agent" createConnector="true"/>
</camel:camelContext>
The ActiveMQ JMS broker is also configured in this xml file. We set it up to
listen on TCP port 61610.
<!-- lets configure the ActiveMQ JMS broker server to listen on TCP 61610 -->
<broker:broker useJmx="false" persistent="false" brokerName="localhost">
<broker:transportConnectors>
111
T U T O R IAL S
<broker:transportConnector name="tcp" uri="tcp://localhost:61610"/>
</broker:transportConnectors>
</broker:broker>
As this examples uses JMS then Camel needs a JMS component that is
connected with the ActiveMQ broker. This is configured as shown below:
<!-- lets configure the Camel ActiveMQ to use the ActiveMQ broker declared above -->
<bean id="jms" class="org.apache.activemq.camel.component.ActiveMQComponent">
<property name="brokerURL" value="tcp://localhost:61610"/>
</bean>
Notice: The JMS component is configured in standard Spring beans, but the
gem is that the bean id can be referenced from Camel routes - meaning we
can do routing using the JMS Component by just using jms: prefix in the
route URI. What happens is that Camel will find in the Spring Registry for a
bean with the id="jms". Since the bean id can have arbitrary name you could
have named it id="jmsbroker" and then referenced to it in the routing as
from="jmsbroker:queue:numbers).to("multiplier");
We use the vm protocol to connect to the ActiveMQ server as its embedded
in this application.
componentscan
Defines the package to be scanned for Spring stereotype
annotations, in this case, to load the "multiplier" bean
camelcontext
Defines the package to be scanned for Camel routes. Will
find the ServerRoutes class and create the routes
contained within it
jms bean
Creates the Camel JMS component
AOP Enabled Server
The example has an enhanced Server example that uses fullblown AspejctJ
AOP for doing a audit tracking of invocations of the business service.
We leverage Spring AOP support in the {{camel-server-aop.xml}
configuration file. First we must declare the correct XML schema's to use:
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:aop="http://www.springframework.org/schema/aop"
xmlns:camel="http://camel.apache.org/schema/spring"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:broker="http://activemq.apache.org/schema/core"
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/
T U T O R IA L S
112
schema/beans/spring-beans.xsd
http://www.springframework.org/schema/aop http://www.springframework.org/
schema/aop/spring-aop.xsd
http://www.springframework.org/schema/context http://www.springframework.org/
schema/context/spring-context.xsd
http://camel.apache.org/schema/spring http://camel.apache.org/schema/spring/
camel-spring.xsd
http://activemq.apache.org/schema/core http://activemq.apache.org/schema/core/
activemq-core-5.5.0.xsd">
Then we include all the existing configuration from the normal server
example:
<!-- let Spring do its IoC stuff in this package -->
<context:component-scan base-package="org.apache.camel.example.server"/>
<!-- lets configure the ActiveMQ JMS broker server to listen on TCP 61610 -->
<broker:broker useJmx="false" persistent="false" brokerName="localhost">
<broker:transportConnectors>
<broker:transportConnector name="tcp" uri="tcp://localhost:61610"/>
</broker:transportConnectors>
</broker:broker>
<!-- lets configure the Camel JMS consumer to use the ActiveMQ broker declared above
-->
<bean id="jms" class="org.apache.camel.component.jms.JmsComponent">
<property name="connectionFactory">
<bean class="org.apache.activemq.ActiveMQConnectionFactory">
<property name="brokerURL" value="tcp://localhost:61610"/>
</bean>
</property>
</bean>
Then we enable the AspejctJ AOP auto proxy feature of Spring that will scan
for classes annotated with the @Aspect annotation:
<!-- turn on AspejctJ AOP to weave all @Aspects beans declared in this spring xml
file -->
<aop:aspectj-autoproxy/>
Then we define our Audit tracker bean that does the actual audit logging. It's
also the class that is annotated with the @Aspect so Spring will pick this up,
as the aspect.
<!-- Aspect that tracks all the invocations of the business service -->
<bean id="AuditTracker" class="org.apache.camel.example.server.AuditTracker">
<!-- define what store to use for audit backup -->
<property name="store" ref="AuditStore"/>
</bean>
113
T U T O R IAL S
And the gem is that we inject the AuditTracker aspect bean with a Camel
endpoint that defines where the audit should be stored. Noticed how easy it
is to setup as we have just defined an endpoint URI that is file based,
meaning that we stored the audit tracks as files. We can change this tore to
any Camel components as we wish. To store it on a JMS queue simply change
the URI to jms:queue:audit.
<!-- declare a camel context that scans for classes that is RouteBuilder
in the package org.apache.camel.example.server -->
<camel:camelContext id="camel-server-aop">
<camel:package>org.apache.camel.example.server</camel:package>
<!-- enable JMX connector so we can connect to the server and browse mbeans -->
<!-- Camel will log at INFO level the service URI to use for connecting with
jconsole -->
<camel:jmxAgent id="agent" createConnector="true"/>
<!-- the audit store endpoint is configued as file based.
In Camel 2.0 the endpoint should be defined in camel context -->
<camel:endpoint id="AuditStore" uri="file://target/store"/>
</camel:camelContext>
And the full blown Aspejct for the audit tracker java code:
/**
* For audit tracking of all incoming invocations of our business (Multiplier)
*/
@Aspect
public class AuditTracker {
// endpoint we use for backup store of audit tracks
private Endpoint store;
@Required
public void setStore(Endpoint store) {
this.store = store;
}
@Before("execution(int org.apache.camel.example.server.Multiplier.multiply(int))
&& args(originalNumber)")
public void audit(int originalNumber) throws Exception {
String msg = "Someone called us with this number " + originalNumber;
System.out.println(msg);
// now send the message to the backup store using the Camel Message Endpoint
pattern
Exchange exchange = store.createExchange();
exchange.getIn().setBody(msg);
store.createProducer().process(exchange);
}
}
T U T O R IA L S
114
Run the Server
The Server is started using the org.apache.camel.spring.Main class that
can start camel-spring application out-of-the-box. The Server can be started
in several flavors:
▪ as a standard java main application - just start the
org.apache.camel.spring.Main class
▪ using maven jave:exec
▪ using camel:run
In this sample as there are two servers (with and without AOP) we have
prepared some profiles in maven to start the Server of your choice.
The server is started with:
mvn compile exec:java -PCamelServer
Or for the AOP enabled Server example:
mvn compile exec:java -PCamelServerAOP
WRITING THE CLIENTS
This sample has three clients demonstrating different Camel techniques for
communication
▪ CamelClient using the ProducerTemplate for Spring template style
coding
▪ CamelRemoting using Spring Remoting
▪ CamelEndpoint using the Message Endpoint EIP pattern using a
neutral Camel API
Client Using The ProducerTemplate
We will initially create a client by directly using ProducerTemplate. We will
later create a client which uses Spring remoting to hide the fact that
messaging is being used.
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:camel="http://camel.apache.org/schema/spring"
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/
schema/beans/spring-beans.xsd
http://camel.apache.org/schema/spring http://camel.apache.org/schema/spring/
camel-spring.xsd">
<camel:camelContext id="camel-client">
<camel:template id="camelTemplate"/>
</camel:camelContext>
115
T U T O R IAL S
<!-- Camel JMSProducer to be able to send messages to a remote Active MQ server -->
<bean id="jms" class="org.apache.activemq.camel.component.ActiveMQComponent">
<property name="brokerURL" value="tcp://localhost:61610"/>
</bean>
The client will not use the Camel Maven Plugin so the Spring XML has been
placed in src/main/resources to not conflict with the server configs.
camelContext
The Camel context is defined but does not contain any
routes
template
The ProducerTemplate is used to place messages onto
the JMS queue
jms bean
This initialises the Camel JMS component, allowing us to
place messages onto the queue
And the CamelClient source code:
public static void main(final String[] args) throws Exception {
System.out.println("Notice this client requires that the CamelServer is already
running!");
ApplicationContext context = new
ClassPathXmlApplicationContext("camel-client.xml");
// get the camel template for Spring template style sending of messages (=
producer)
ProducerTemplate camelTemplate = (ProducerTemplate)
context.getBean("camelTemplate");
System.out.println("Invoking the multiply with 22");
// as opposed to the CamelClientRemoting example we need to define the service
URI in this java code
int response = (Integer)camelTemplate.sendBody("jms:queue:numbers",
ExchangePattern.InOut, 22);
System.out.println("... the result is: " + response);
System.exit(0);
}
The ProducerTemplate is retrieved from a Spring ApplicationContext and
used to manually place a message on the "numbers" JMS queue. The
exchange pattern (ExchangePattern.InOut) states that the call should be
synchronous, and that we will receive a response.
Before running the client be sure that both the ActiveMQ broker and the
CamelServer are running.
T U T O R IA L S
116
Client Using Spring Remoting
Spring Remoting "eases the development of remote-enabled services". It
does this by allowing you to invoke remote services through your regular
Java interface, masking that a remote service is being called.
<!-- Camel proxy for a given service, in this case the JMS queue
In Camel 2.0 , the proxy should be defined in camelContext. -->
<camel:proxy
id="multiplierProxy"
serviceInterface="org.apache.camel.example.server.Multiplier"
serviceUrl="jms:queue:numbers"/>
The snippet above only illustrates the different and how Camel easily can
setup and use Spring Remoting in one line configurations.
The proxy will create a proxy service bean for you to use to make the
remote invocations. The serviceInterface property details which Java
interface is to be implemented by the proxy. serviceUrl defines where
messages sent to this proxy bean will be directed. Here we define the JMS
endpoint with the "numbers" queue we used when working with Camel
template directly. The value of the id property is the name that will be the
given to the bean when it is exposed through the Spring
ApplicationContext. We will use this name to retrieve the service in our
client. I have named the bean multiplierProxy simply to highlight that it is not
the same multiplier bean as is being used by CamelServer. They are in
completely independent contexts and have no knowledge of each other. As
you are trying to mask the fact that remoting is being used in a real
application you would generally not include proxy in the name.
And the Java client source code:
public static void main(final String[] args) {
System.out.println("Notice this client requires that the CamelServer is already
running!");
ApplicationContext context = new
ClassPathXmlApplicationContext("camel-client-remoting.xml");
// just get the proxy to the service and we as the client can use the "proxy" as
it was
// a local object we are invoking. Camel will under the covers do the remote
communication
// to the remote ActiveMQ server and fetch the response.
Multiplier multiplier = (Multiplier)context.getBean("multiplierProxy");
System.out.println("Invoking the multiply with 33");
int response = multiplier.multiply(33);
System.out.println("... the result is: " + response);
117
T U T O R IAL S
System.exit(0);
}
Again, the client is similar to the original client, but with some important
differences.
1. The Spring context is created with the new camel-client-remoting.xml
2. We retrieve the proxy bean instead of a ProducerTemplate. In a nontrivial example you would have the bean injected as in the standard
Spring manner.
3. The multiply method is then called directly. In the client we are now
working to an interface. There is no mention of Camel or JMS inside
our Java code.
Client Using Message Endpoint EIP Pattern
This client uses the Message Endpoint EIP pattern to hide the complexity to
communicate to the Server. The Client uses the same simple API to get hold
of the endpoint, create an exchange that holds the message, set the payload
and create a producer that does the send and receive. All done using the
same neutral Camel API for all the components in Camel. So if the
communication was socket TCP based you just get hold of a different
endpoint and all the java code stays the same. That is really powerful.
Okay enough talk, show me the code!
public static void main(final String[] args) throws Exception {
System.out.println("Notice this client requires that the CamelServer is already
running!");
ApplicationContext context = new
ClassPathXmlApplicationContext("camel-client.xml");
CamelContext camel = (CamelContext) context.getBean("camel-client");
// get the endpoint from the camel context
Endpoint endpoint = camel.getEndpoint("jms:queue:numbers");
// create the exchange used for the communication
// we use the in out pattern for a synchronized exchange where we expect a
response
Exchange exchange = endpoint.createExchange(ExchangePattern.InOut);
// set the input on the in body
// must you correct type to match the expected type of an Integer object
exchange.getIn().setBody(11);
// to send the exchange we need an producer to do it for us
Producer producer = endpoint.createProducer();
// start the producer so it can operate
producer.start();
T U T O R IA L S
118
// let the producer process the exchange where it does all the work in this
oneline of code
System.out.println("Invoking the multiply with 11");
producer.process(exchange);
// get the response from the out body and cast it to an integer
int response = exchange.getOut().getBody(Integer.class);
System.out.println("... the result is: " + response);
// stop and exit the client
producer.stop();
System.exit(0);
}
Switching to a different component is just a matter of using the correct
endpoint. So if we had defined a TCP endpoint as:
"mina:tcp://localhost:61610" then its just a matter of getting hold of this
endpoint instead of the JMS and all the rest of the java code is exactly the
same.
Run the Clients
The Clients is started using their main class respectively.
▪ as a standard java main application - just start their main class
▪ using maven jave:exec
In this sample we start the clients using maven:
mvn compile exec:java -PCamelClient
mvn compile exec:java -PCamelClientRemoting
mvn compile exec:java -PCamelClientEndpoint
Also see the Maven pom.xml file how the profiles for the clients is defined.
USING THE CAMEL MAVEN PLUGIN
The Camel Maven Plugin allows you to run your Camel routes directly from
Maven. This negates the need to create a host application, as we did with
Camel server, simply to start up the container. This can be very useful during
development to get Camel routes running quickly.
Listing 16. pom.xml
<build>
<plugins>
<plugin>
<groupId>org.apache.camel</groupId>
<artifactId>camel-maven-plugin</artifactId>
119
T U T O R IAL S
</plugin>
</plugins>
</build>
All that is required is a new plugin definition in your Maven POM. As we have
already placed our Camel config in the default location (camel-server.xml has
been placed in META-INF/spring/) we do not need to tell the plugin where the
route definitions are located. Simply run mvn camel:run.
USING CAMEL JMX
Camel has extensive support for JMX and allows us to inspect the Camel
Server at runtime. As we have enabled the JMXAgent in our tutorial we can
fire up the jconsole and connect to the following service URI:
service:jmx:rmi:///jndi/rmi://localhost:1099/jmxrmi/camel. Notice
that Camel will log at INFO level the JMX Connector URI:
...
DefaultInstrumentationAgent
INFO JMX connector thread started on
service:jmx:rmi:///jndi/rmi://claus-acer:1099/jmxrmi/camel
...
In the screenshot below we can see the route and its performance metrics:
SEE ALSO
• Spring Remoting with JMS Example on Amin Abbaspour's Weblog
T U T O R IA L S
120
TUTORIAL - CAMEL-EXAMPLE-REPORTINCIDENT
INTRODUCTION
Creating this tutorial was inspired by a real life use-case I discussed over the
phone with a colleague. He was working at a client whom uses a heavyweight integration platform from a very large vendor. He was in talks with
developer shops to implement a new integration on this platform. His trouble
was the shop tripled the price when they realized the platform of choice. So I
was wondering how we could do this integration with Camel. Can it be done,
without tripling the cost
.
This tutorial is written during the development of the integration. I have
decided to start off with a sample that isn't Camel's but standard Java and
then plugin Camel as we goes. Just as when people needed to learn Spring
you could consume it piece by piece, the same goes with Camel.
The target reader is person whom hasn't experience or just started using
Camel.
MOTIVATION FOR THIS TUTORIAL
I wrote this tutorial motivated as Camel lacked an example application that
was based on the web application deployment model. The entire world hasn't
moved to pure OSGi deployments yet.
THE USE-CASE
The goal is to allow staff to report incidents into a central administration. For
that they use client software where they report the incident and submit it to
the central administration. As this is an integration in a transition phase the
administration should get these incidents by email whereas they are
manually added to the database. The client software should gather the
incident and submit the information to the integration platform that in term
will transform the report into an email and send it to the central
administrator for manual processing.
The figure below illustrates this process. The end users reports the
incidents using the client applications. The incident is sent to the central
integration platform as webservice. The integration platform will process the
incident and send an OK acknowledgment back to the client. Then the
integration will transform the message to an email and send it to the
administration mail server. The users in the administration will receive the
emails and take it from there.
121
T U T O R IAL S
In EIP patterns
We distill the use case as EIP patterns:
PARTS
This tutorial is divided into sections and parts:
Section A: Existing Solution, how to slowly use Camel
Part 1 - This first part explain how to setup the project and get a
webservice exposed using Apache CXF. In fact we don't touch Camel yet.
Part 2 - Now we are ready to introduce Camel piece by piece (without
using Spring or any XML configuration file) and create the full feature
integration. This part will introduce different Camel's concepts and How we
can build our solution using them like :
▪ CamelContext
▪ Endpoint, Exchange & Producer
▪ Components : Log, File
Part 3 - Continued from part 2 where we implement that last part of the
solution with the event driven consumer and how to send the email through
the Mail component.
Section B: The Camel Solution
Part 4 - We now turn into the path of Camel where it excels - the routing.
Part 5 - Is about how embed Camel with Spring and using CXF endpoints
directly in Camel
T U T O R IA L S
122
Using Axis 2
See this blog entry by Sagara demonstrating how to use Apache
Axis 2 instead of Apache CXF as the web service framework.
LINKS
▪
▪
▪
▪
▪
▪
Introduction
Part 1
Part 2
Part 3
Part 4
Part 5
PART 1
PREREQUISITES
This tutorial uses the following frameworks:
• Maven 2.0.9
• Apache Camel 1.4.0
• Apache CXF 2.1.1
• Spring 2.5.5
Note: The sample project can be downloaded, see the resources section.
INITIAL PROJECT SETUP
We want the integration to be a standard .war application that can be
deployed in any web container such as Tomcat, Jetty or even heavy weight
application servers such as WebLogic or WebSphere. There fore we start off
with the standard Maven webapp project that is created with the following
long archetype command:
mvn archetype:create -DgroupId=org.apache.camel
-DartifactId=camel-example-reportincident -DarchetypeArtifactId=maven-archetype-webapp
Notice that the groupId etc. doens't have to be org.apache.camel it can be
com.mycompany.whatever. But I have used these package names as the
example is an official part of the Camel distribution.
123
T U T O R IAL S
Then we have the basic maven folder layout. We start out with the
webservice part where we want to use Apache CXF for the webservice stuff.
So we add this to the pom.xml
<properties>
<cxf-version>2.1.1</cxf-version>
</properties>
<dependency>
<groupId>org.apache.cxf</groupId>
<artifactId>cxf-rt-core</artifactId>
<version>${cxf-version}</version>
</dependency>
<dependency>
<groupId>org.apache.cxf</groupId>
<artifactId>cxf-rt-frontend-jaxws</artifactId>
<version>${cxf-version}</version>
</dependency>
<dependency>
<groupId>org.apache.cxf</groupId>
<artifactId>cxf-rt-transports-http</artifactId>
<version>${cxf-version}</version>
</dependency>
DEVELOPING THE WEBSERVICE
As we want to develop webservice with the contract first approach we create
our .wsdl file. As this is a example we have simplified the model of the
incident to only include 8 fields. In real life the model would be a bit more
complex, but not to much.
We put the wsdl file in the folder src/main/webapp/WEB-INF/wsdl and
name the file report_incident.wsdl.
<?xml version="1.0" encoding="ISO-8859-1"?>
<wsdl:definitions xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/"
xmlns:tns="http://reportincident.example.camel.apache.org"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:http="http://schemas.xmlsoap.org/wsdl/http/"
xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/"
targetNamespace="http://reportincident.example.camel.apache.org">
<!-- Type definitions for input- and output parameters for webservice -->
<wsdl:types>
<xs:schema targetNamespace="http://reportincident.example.camel.apache.org">
<xs:element name="inputReportIncident">
<xs:complexType>
<xs:sequence>
<xs:element type="xs:string"
T U T O R IA L S
124
name="incidentId"/>
<xs:element type="xs:string"
name="incidentDate"/>
<xs:element type="xs:string"
name="givenName"/>
<xs:element type="xs:string"
name="familyName"/>
<xs:element type="xs:string"
name="summary"/>
<xs:element type="xs:string"
name="details"/>
<xs:element type="xs:string"
name="email"/>
<xs:element type="xs:string"
name="phone"/>
</xs:sequence>
</xs:complexType>
</xs:element>
<xs:element name="outputReportIncident">
<xs:complexType>
<xs:sequence>
<xs:element type="xs:string"
name="code"/>
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:schema>
</wsdl:types>
<!-- Message definitions for input and output -->
<wsdl:message name="inputReportIncident">
<wsdl:part name="parameters" element="tns:inputReportIncident"/>
</wsdl:message>
<wsdl:message name="outputReportIncident">
<wsdl:part name="parameters" element="tns:outputReportIncident"/>
</wsdl:message>
<!-- Port (interface) definitions -->
<wsdl:portType name="ReportIncidentEndpoint">
<wsdl:operation name="ReportIncident">
<wsdl:input message="tns:inputReportIncident"/>
<wsdl:output message="tns:outputReportIncident"/>
</wsdl:operation>
</wsdl:portType>
<!-- Port bindings to transports and encoding - HTTP, document literal
encoding is used -->
<wsdl:binding name="ReportIncidentBinding" type="tns:ReportIncidentEndpoint">
<soap:binding transport="http://schemas.xmlsoap.org/soap/http"/>
<wsdl:operation name="ReportIncident">
<soap:operation
soapAction="http://reportincident.example.camel.apache.org/ReportIncident"
style="document"/>
125
T U T O R IAL S
<wsdl:input>
<soap:body parts="parameters" use="literal"/>
</wsdl:input>
<wsdl:output>
<soap:body parts="parameters" use="literal"/>
</wsdl:output>
</wsdl:operation>
</wsdl:binding>
<!-- Service definition -->
<wsdl:service name="ReportIncidentService">
<wsdl:port name="ReportIncidentPort"
binding="tns:ReportIncidentBinding">
<soap:address
location="http://reportincident.example.camel.apache.org"/>
</wsdl:port>
</wsdl:service>
</wsdl:definitions>
CXF wsdl2java
Then we integration the CXF wsdl2java generator in the pom.xml so we have
CXF generate the needed POJO classes for our webservice contract.
However at first we must configure maven to live in the modern world of Java
1.5 so we must add this to the pom.xml
<!-- to compile with 1.5 -->
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<source>1.5</source>
<target>1.5</target>
</configuration>
</plugin>
And then we can add the CXF wsdl2java code generator that will hook into
the compile goal so its automatic run all the time:
<!-- CXF wsdl2java generator, will plugin to the compile goal
-->
<plugin>
<groupId>org.apache.cxf</groupId>
<artifactId>cxf-codegen-plugin</artifactId>
<version>${cxf-version}</version>
<executions>
<execution>
<id>generate-sources</id>
T U T O R IA L S
126
<phase>generate-sources</phase>
<configuration>
<sourceRoot>${basedir}/target/
generated/src/main/java</sourceRoot>
<wsdlOptions>
<wsdlOption>
<wsdl>${basedir}/src/main/webapp/WEB-INF/wsdl/report_incident.wsdl</wsdl>
</wsdlOption>
</wsdlOptions>
</configuration>
<goals>
<goal>wsdl2java</goal>
</goals>
</execution>
</executions>
</plugin>
You are now setup and should be able to compile the project. So running the
mvn compile should run the CXF wsdl2java and generate the source code in
the folder &{basedir}/target/generated/src/main/java that we specified
in the pom.xml above. Since its in the target/generated/src/main/java
maven will pick it up and include it in the build process.
Configuration of the web.xml
Next up is to configure the web.xml to be ready to use CXF so we can expose
the webservice.
As Spring is the center of the universe, or at least is a very important
framework in today's Java land we start with the listener that kick-starts
Spring. This is the usual piece of code:
<!-- the listener that kick-starts Spring -->
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
And then we have the CXF part where we define the CXF servlet and its URI
mappings to which we have chosen that all our webservices should be in the
path /webservices/
<!-- CXF servlet -->
<servlet>
<servlet-name>CXFServlet</servlet-name>
<servlet-class>org.apache.cxf.transport.servlet.CXFServlet</servlet-class>
127
T U T O R IAL S
<load-on-startup>1</load-on-startup>
</servlet>
<!-- all our webservices are mapped under this URI pattern -->
<servlet-mapping>
<servlet-name>CXFServlet</servlet-name>
<url-pattern>/webservices/*</url-pattern>
</servlet-mapping>
Then the last piece of the puzzle is to configure CXF, this is done in a spring
XML that we link to fron the web.xml by the standard Spring
contextConfigLocation property in the web.xml
<!-- location of spring xml files -->
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:cxf-config.xml</param-value>
</context-param>
We have named our CXF configuration file cxf-config.xml and its located in
the root of the classpath. In Maven land that is we can have the cxfconfig.xml file in the src/main/resources folder. We could also have the
file located in the WEB-INF folder for instance <param-value>/WEB-INF/cxfconfig.xml</param-value>.
Getting rid of the old jsp world
The maven archetype that created the basic folder structure also created a
sample .jsp file index.jsp. This file src/main/webapp/index.jsp should be
deleted.
Configuration of CXF
The cxf-config.xml is as follows:
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:jaxws="http://cxf.apache.org/jaxws"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-2.0.xsd
http://cxf.apache.org/jaxws http://cxf.apache.org/schemas/jaxws.xsd">
<import resource="classpath:META-INF/cxf/cxf.xml"/>
<import resource="classpath:META-INF/cxf/cxf-extension-soap.xml"/>
<import resource="classpath:META-INF/cxf/cxf-servlet.xml"/>
T U T O R IA L S
128
<!-- implementation of the webservice -->
<bean id="reportIncidentEndpoint"
class="org.apache.camel.example.reportincident.ReportIncidentEndpointImpl"/>
<!-- export the webservice using jaxws -->
<jaxws:endpoint id="reportIncident"
implementor="#reportIncidentEndpoint"
address="/incident"
wsdlLocation="/WEB-INF/wsdl/report_incident.wsdl"
endpointName="s:ReportIncidentPort"
serviceName="s:ReportIncidentService"
xmlns:s="http://reportincident.example.camel.apache.org"/>
</beans>
The configuration is standard CXF and is documented at the Apache CXF
website.
The 3 import elements is needed by CXF and they must be in the file.
Noticed that we have a spring bean reportIncidentEndpoint that is the
implementation of the webservice endpoint we let CXF expose.
Its linked from the jaxws element with the implementator attribute as we use
the # mark to identify its a reference to a spring bean. We could have stated
the classname directly as
implementor="org.apache.camel.example.reportincident.ReportIncidentEndpoint
but then we lose the ability to let the ReportIncidentEndpoint be configured
by spring.
The address attribute defines the relative part of the URL of the exposed
webservice. wsdlLocation is an optional parameter but for persons like me
that likes contract-first we want to expose our own .wsdl contracts and not
the auto generated by the frameworks, so with this attribute we can link to
the real .wsdl file. The last stuff is needed by CXF as you could have several
services so it needs to know which this one is. Configuring these is quite easy
as all the information is in the wsdl already.
Implementing the ReportIncidentEndpoint
Phew after all these meta files its time for some java code so we should code
the implementor of the webservice. So we fire up mvn compile to let CXF
generate the POJO classes for our webservice and we are ready to fire up a
Java editor.
You can use mvn idea:idea or mvn eclipse:eclipse to create project
files for these editors so you can load the project. However IDEA has been
smarter lately and can load a pom.xml directly.
As we want to quickly see our webservice we implement just a quick and
dirty as it can get. At first beware that since its jaxws and Java 1.5 we get
129
T U T O R IAL S
annotations for the money, but they reside on the interface so we can
remove them from our implementations so its a nice plain POJO again:
package org.apache.camel.example.reportincident;
/**
* The webservice we have implemented.
*/
public class ReportIncidentEndpointImpl implements ReportIncidentEndpoint {
public OutputReportIncident reportIncident(InputReportIncident parameters) {
System.out.println("Hello ReportIncidentEndpointImpl is called from " +
parameters.getGivenName());
OutputReportIncident out = new OutputReportIncident();
out.setCode("OK");
return out;
}
}
We just output the person that invokes this webservice and returns a OK
response. This class should be in the maven source root folder src/main/
java under the package name
org.apache.camel.example.reportincident. Beware that the maven
archetype tool didn't create the src/main/java folder, so you should
create it manually.
To test if we are home free we run mvn clean compile.
Running our webservice
Now that the code compiles we would like to run it in a web container, so we
add jetty to our pom.xml so we can run mvn jetty:run:
<properties>
...
<jetty-version>6.1.1</jetty-version>
</properties>
<build>
<plugins>
...
<!-- so we can run mvn jetty:run -->
<plugin>
<groupId>org.mortbay.jetty</groupId>
<artifactId>maven-jetty-plugin</artifactId>
<version>${jetty-version}</version>
</plugin>
T U T O R IA L S
130
Notice: We use Jetty v6.1.1 as never versions has troubles on my laptop.
Feel free to try a newer version on your system, but v6.1.1 works flawless.
So to see if everything is in order we fire up jetty with mvn jetty:run and
if everything is okay you should be able to access http://localhost:8080.
Jetty is smart that it will list the correct URI on the page to our web
application, so just click on the link. This is smart as you don't have to
remember the exact web context URI for your application - just fire up the
default page and Jetty will help you.
So where is the damn webservice then? Well as we did configure the
web.xml to instruct the CXF servlet to accept the pattern /webservices/*
we should hit this URL to get the attention of CXF: http://localhost:8080/
camel-example-reportincident/webservices.
Â
Hitting the webservice
Now we have the webservice running in a standard .war application in a
standard web container such as Jetty we would like to invoke the webservice
and see if we get our code executed. Unfortunately this isn't the easiest task
in the world - its not so easy as a REST URL, so we need tools for this. So we
fire up our trusty webservice tool SoapUI and let it be the one to fire the
webservice request and see the response.
Using SoapUI we sent a request to our webservice and we got the
expected OK response and the console outputs the System.out so we are
ready to code.
131
T U T O R IAL S
Â
Remote Debugging
Okay a little sidestep but wouldn't it be cool to be able to debug your code
when its fired up under Jetty? As Jetty is started from maven, we need to
instruct maven to use debug mode.
Se we set the MAVEN_OPTS environment to start in debug mode and listen on
port 5005.
MAVEN_OPTS=-Xmx512m -XX:MaxPermSize=128m -Xdebug
-Xrunjdwp:transport=dt_socket,server=y,suspend=n,address=5005
Then you need to restart Jetty so its stopped with ctrl + c. Remember to
start a new shell to pickup the new environment settings. And start jetty
again.
Then we can from our IDE attach a remote debugger and debug as we
want.
First we configure IDEA to attach to a remote debugger on port 5005:
T U T O R IA L S
132
Â
Then we set a breakpoint in our code ReportIncidentEndpoint and hit
the SoapUI once again and we are breaked at the breakpoint where we can
inspect the parameters:
133
T U T O R IAL S
Â
Adding a unit test
Oh so much hard work just to hit a webservice, why can't we just use an unit
test to invoke our webservice? Yes of course we can do this, and that's the
next step.
First we create the folder structure src/test/java and src/test/
resources. We then create the unit test in the src/test/java folder.
package org.apache.camel.example.reportincident;
import junit.framework.TestCase;
/**
* Plain JUnit test of our webservice.
*/
public class ReportIncidentEndpointTest extends TestCase {
}
T U T O R IA L S
134
Here we have a plain old JUnit class. As we want to test webservices we need
to start and expose our webservice in the unit test before we can test it. And
JAXWS has pretty decent methods to help us here, the code is simple as:
import javax.xml.ws.Endpoint;
...
private static String ADDRESS = "http://localhost:9090/unittest";
protected void startServer() throws Exception {
// We need to start a server that exposes or webservice during the unit
testing
// We use jaxws to do this pretty simple
ReportIncidentEndpointImpl server = new ReportIncidentEndpointImpl();
Endpoint.publish(ADDRESS, server);
}
The Endpoint class is the javax.xml.ws.Endpoint that under the covers
looks for a provider and in our case its CXF - so its CXF that does the heavy
lifting of exposing out webservice on the given URL address. Since our class
ReportIncidentEndpointImpl implements the interface
ReportIncidentEndpoint that is decorated with all the jaxws annotations it
got all the information it need to expose the webservice. Below is the CXF
wsdl2java generated interface:
/*
*
*/
package org.apache.camel.example.reportincident;
import
import
import
import
import
import
import
javax.jws.WebMethod;
javax.jws.WebParam;
javax.jws.WebResult;
javax.jws.WebService;
javax.jws.soap.SOAPBinding;
javax.jws.soap.SOAPBinding.ParameterStyle;
javax.xml.bind.annotation.XmlSeeAlso;
/**
* This class was generated by Apache CXF 2.1.1
* Wed Jul 16 12:40:31 CEST 2008
* Generated source version: 2.1.1
*
*/
/*
*
*/
135
T U T O R IAL S
@WebService(targetNamespace = "http://reportincident.example.camel.apache.org", name
= "ReportIncidentEndpoint")
@XmlSeeAlso({ObjectFactory.class})
@SOAPBinding(parameterStyle = SOAPBinding.ParameterStyle.BARE)
public interface ReportIncidentEndpoint {
/*
*
*/
@SOAPBinding(parameterStyle = SOAPBinding.ParameterStyle.BARE)
@WebResult(name = "outputReportIncident", targetNamespace =
"http://reportincident.example.camel.apache.org", partName = "parameters")
@WebMethod(operationName = "ReportIncident", action =
"http://reportincident.example.camel.apache.org/ReportIncident")
public OutputReportIncident reportIncident(
@WebParam(partName = "parameters", name = "inputReportIncident",
targetNamespace = "http://reportincident.example.camel.apache.org")
InputReportIncident parameters
);
}
Next up is to create a webservice client so we can invoke our webservice. For
this we actually use the CXF framework directly as its a bit more easier to
create a client using this framework than using the JAXWS style. We could
have done the same for the server part, and you should do this if you need
more power and access more advanced features.
import org.apache.cxf.jaxws.JaxWsProxyFactoryBean;
...
protected ReportIncidentEndpoint createCXFClient() {
// we use CXF to create a client for us as its easier than JAXWS and works
JaxWsProxyFactoryBean factory = new JaxWsProxyFactoryBean();
factory.setServiceClass(ReportIncidentEndpoint.class);
factory.setAddress(ADDRESS);
return (ReportIncidentEndpoint) factory.create();
}
So now we are ready for creating a unit test. We have the server and the
client. So we just create a plain simple unit test method as the usual junit
style:
public void testRendportIncident() throws Exception {
startServer();
ReportIncidentEndpoint client = createCXFClient();
T U T O R IA L S
136
InputReportIncident input = new InputReportIncident();
input.setIncidentId("123");
input.setIncidentDate("2008-07-16");
input.setGivenName("Claus");
input.setFamilyName("Ibsen");
input.setSummary("bla bla");
input.setDetails("more bla bla");
input.setEmail("davsclaus@apache.org");
input.setPhone("+45 2962 7576");
OutputReportIncident out = client.reportIncident(input);
assertEquals("Response code is wrong", "OK", out.getCode());
}
Now we are nearly there. But if you run the unit test with mvn test then it
will fail. Why!!! Well its because that CXF needs is missing some
dependencies during unit testing. In fact it needs the web container, so we
need to add this to our pom.xml.
<!-- cxf web container for unit testing -->
<dependency>
<groupId>org.apache.cxf</groupId>
<artifactId>cxf-rt-transports-http-jetty</artifactId>
<version>${cxf-version}</version>
<scope>test</scope>
</dependency>
Well what is that, CXF also uses Jetty for unit test - well its just shows how
agile, embedable and popular Jetty is.
So lets run our junit test with, and it reports:
mvn test
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0
[INFO] BUILD SUCCESSFUL
Yep thats it for now. We have a basic project setup.
END OF PART 1
Thanks for being patient and reading all this more or less standard Maven,
Spring, JAXWS and Apache CXF stuff. Its stuff that is well covered on the net,
but I wanted a full fledged tutorial on a maven project setup that is web
service ready with Apache CXF. We will use this as a base for the next part
where we demonstrate how Camel can be digested slowly and piece by piece
137
T U T O R IAL S
just as it was back in the times when was introduced and was learning the
Spring framework that we take for granted today.
RESOURCES
• Apache CXF user guide
•
Name
Size
Creator
Creation
Date
Comment
ZIP Archive
tutorial_reportincident_partone.zi...
14
kB
Claus
Ibsen
Jul 17,
2008
23:34
Â
Â
◦ P
◦ R
LINKS
▪
▪
▪
▪
▪
▪
Introduction
Part 1
Part 2
Part 3
Part 4
Part 5
PART 2
ADDING CAMEL
In this part we will introduce Camel so we start by adding Camel to our
pom.xml:
<properties>
...
<camel-version>1.4.0</camel-version>
</properties>
<!-- camel -->
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-core</artifactId>
<version>${camel-version}</version>
</dependency>
That's it, only one dependency for now.
T U T O R IA L S
138
Synchronize IDE
If you continue from part 1, remember to update your editor project
settings since we have introduce new .jar files. For instance IDEA
has a feature to synchronize with Maven projects.
Now we turn towards our webservice endpoint implementation where we
want to let Camel have a go at the input we receive. As Camel is very non
invasive its basically a .jar file then we can just grap Camel but creating a
new instance of DefaultCamelContext that is the hearth of Camel its
context.
CamelContext camel = new DefaultCamelContext();
In fact we create a constructor in our webservice and add this code:
private CamelContext camel;
public ReportIncidentEndpointImpl() throws Exception {
// create the camel context that is the "heart" of Camel
camel = new DefaultCamelContext();
// add the log component
camel.addComponent("log", new LogComponent());
// start Camel
camel.start();
}
LOGGING THE "HELLO WORLD"
Here at first we want Camel to log the givenName and familyName
parameters we receive, so we add the LogComponent with the key log. And
we must start Camel before its ready to act.
Then we change the code in the method that is invoked by Apache CXF when
a webservice request arrives. We get the name and let Camel have a go at it
in the new method we create sendToCamel:
public OutputReportIncident reportIncident(InputReportIncident parameters) {
String name = parameters.getGivenName() + " " + parameters.getFamilyName();
// let Camel do something with the name
sendToCamelLog(name);
139
T U T O R IAL S
Component Documentation
The Log and File components is documented as well, just click on
the links. Just return to this documentation later when you must use
these components for real.
OutputReportIncident out = new OutputReportIncident();
out.setCode("OK");
return out;
}
Next is the Camel code. At first it looks like there are many code lines to do a
simple task of logging the name - yes it is. But later you will in fact realize
this is one of Camels true power. Its concise API. Hint: The same code can be
used for any component in Camel.
private void sendToCamelLog(String name) {
try {
// get the log component
Component component = camel.getComponent("log");
// create an endpoint and configure it.
// Notice the URI parameters this is a common pratice in Camel to
configure
// endpoints based on URI.
// com.mycompany.part2 = the log category used. Will log at INFO level as
default
Endpoint endpoint = component.createEndpoint("log:com.mycompany.part2");
// create an Exchange that we want to send to the endpoint
Exchange exchange = endpoint.createExchange();
// set the in message payload (=body) with the name parameter
exchange.getIn().setBody(name);
// now we want to send the exchange to this endpoint and we then need a
producer
// for this, so we create and start the producer.
Producer producer = endpoint.createProducer();
producer.start();
// process the exchange will send the exchange to the log component, that
will process
// the exchange and yes log the payload
producer.process(exchange);
// stop the producer, we want to be nice and cleanup
producer.stop();
T U T O R IA L S
140
} catch (Exception e) {
// we ignore any exceptions and just rethrow as runtime
throw new RuntimeException(e);
}
}
Okay there are code comments in the code block above that should explain
what is happening. We run the code by invoking our unit test with maven mvn
test, and we should get this log line:
INFO: Exchange[BodyType:String, Body:Claus Ibsen]
WRITE TO FILE - EASY WITH THE SAME CODE STYLE
Okay that isn't to impressive, Camel can log
Well I promised that the
above code style can be used for any component, so let's store the payload
in a file. We do this by adding the file component to the Camel context
// add the file component
camel.addComponent("file", new FileComponent());
And then we let camel write the payload to the file after we have logged, by
creating a new method sendToCamelFile. We want to store the payload in
filename with the incident id so we need this parameter also:
// let Camel do something with the name
sendToCamelLog(name);
sendToCamelFile(parameters.getIncidentId(), name);
And then the code that is 99% identical. We have change the URI
configuration when we create the endpoint as we pass in configuration
parameters to the file component.
And then we need to set the output filename and this is done by adding a
special header to the exchange. That's the only difference:
private void sendToCamelFile(String incidentId, String name) {
try {
// get the file component
Component component = camel.getComponent("file");
141
T U T O R IAL S
// create an endpoint and configure it.
// Notice the URI parameters this is a common pratice in Camel to
configure
// endpoints based on URI.
// file://target instructs the base folder to output the files. We put in
the target folder
// then its actumatically cleaned by mvn clean
Endpoint endpoint = component.createEndpoint("file://target");
// create an Exchange that we want to send to the endpoint
Exchange exchange = endpoint.createExchange();
// set the in message payload (=body) with the name parameter
exchange.getIn().setBody(name);
// now a special header is set to instruct the file component what the
output filename
// should be
exchange.getIn().setHeader(FileComponent.HEADER_FILE_NAME, "incident-" +
incidentId + ".txt");
// now we want to send the exchange to this endpoint and we then need a
producer
// for this, so we create and start the producer.
Producer producer = endpoint.createProducer();
producer.start();
// process the exchange will send the exchange to the file component,
that will process
// the exchange and yes write the payload to the given filename
producer.process(exchange);
// stop the producer, we want to be nice and cleanup
producer.stop();
} catch (Exception e) {
// we ignore any exceptions and just rethrow as runtime
throw new RuntimeException(e);
}
}
After running our unit test again with mvn test we have a output file in the
target folder:
D:\demo\part-two>type target\incident-123.txt
Claus Ibsen
FULLY JAVA BASED CONFIGURATION OF ENDPOINTS
In the file example above the configuration was URI based. What if you want
100% java setter based style, well this is of course also possible. We just
T U T O R IA L S
142
need to cast to the component specific endpoint and then we have all the
setters available:
// create the file endpoint, we cast to FileEndpoint because then we can
do
// 100% java settter based configuration instead of the URI sting based
// must pass in an empty string, or part of the URI configuration if
wanted
FileEndpoint endpoint = (FileEndpoint)component.createEndpoint("");
endpoint.setFile(new File("target/subfolder"));
endpoint.setAutoCreate(true);
That's it. Now we have used the setters to configure the FileEndpoint that it
should store the file in the folder target/subfolder. Of course Camel now
stores the file in the subfolder.
D:\demo\part-two>type target\subfolder\incident-123.txt
Claus Ibsen
LESSONS LEARNED
Okay I wanted to demonstrate how you can be in 100% control of the
configuration and usage of Camel based on plain Java code with no hidden
magic or special XML or other configuration files. Just add the camel-core.jar
and you are ready to go.
You must have noticed that the code for sending a message to a given
endpoint is the same for both the log and file, in fact any Camel endpoint.
You as the client shouldn't bother with component specific code such as file
stuff for file components, jms stuff for JMS messaging etc. This is what the
Message Endpoint EIP pattern is all about and Camel solves this very very
nice - a key pattern in Camel.
REDUCING CODE LINES
Now that you have been introduced to Camel and one of its masterpiece
patterns solved elegantly with the Message Endpoint its time to give
productive and show a solution in fewer code lines, in fact we can get it down
to 5, 4, 3, 2 .. yes only 1 line of code.
The key is the ProducerTemplate that is a Spring'ish xxxTemplate based
producer. Meaning that it has methods to send messages to any Camel
endpoints. First of all we need to get hold of such a template and this is done
from the CamelContext
143
T U T O R IAL S
private ProducerTemplate template;
public ReportIncidentEndpointImpl() throws Exception {
...
// get the ProducerTemplate thst is a Spring'ish xxxTemplate based producer
for very
// easy sending exchanges to Camel.
template = camel.createProducerTemplate();
// start Camel
camel.start();
}
Now we can use template for sending payloads to any endpoint in Camel.
So all the logging gabble can be reduced to:
template.sendBody("log:com.mycompany.part2.easy", name);
And the same goes for the file, but we must also send the header to instruct
what the output filename should be:
String filename = "easy-incident-" + incidentId + ".txt";
template.sendBodyAndHeader("file://target/subfolder", name,
FileComponent.HEADER_FILE_NAME, filename);
REDUCING EVEN MORE CODE LINES
Well we got the Camel code down to 1-2 lines for sending the message to the
component that does all the heavy work of wring the message to a file etc.
But we still got 5 lines to initialize Camel.
camel = new DefaultCamelContext();
camel.addComponent("log", new LogComponent());
camel.addComponent("file", new FileComponent());
template = camel.createProducerTemplate();
camel.start();
This can also be reduced. All the standard components in Camel is auto
discovered on-the-fly so we can remove these code lines and we are down to
3 lines.
Okay back to the 3 code lines:
T U T O R IA L S
144
Component auto discovery
When an endpoint is requested with a scheme that Camel hasn't
seen before it will try to look for it in the classpath. It will do so by
looking for special Camel component marker files that reside in the
folder META-INF/services/org/apache/camel/component. If there
are files in this folder it will read them as the filename is the
scheme part of the URL. For instance the log component is defined
in this file META-INF/services/org/apache/component/log and its
content is:
class=org.apache.camel.component.log.LogComponent
The class property defines the component implementation.
Tip: End-users can create their 3rd party components using the same
technique and have them been auto discovered on-the-fly.
camel = new DefaultCamelContext();
template = camel.createProducerTemplate();
camel.start();
Later will we see how we can reduce this to ... in fact 0 java code lines. But
the 3 lines will do for now.
MESSAGE TRANSLATION
Okay lets head back to the over goal of the integration. Looking at the EIP
diagrams at the introduction page we need to be able to translate the
incoming webservice to an email. Doing so we need to create the email body.
When doing the message translation we could put up our sleeves and do it
manually in pure java with a StringBuilder such as:
private String createMailBody(InputReportIncident parameters) {
StringBuilder sb = new StringBuilder();
sb.append("Incident ").append(parameters.getIncidentId());
sb.append(" has been reported on the ").append(parameters.getIncidentDate());
sb.append(" by ").append(parameters.getGivenName());
sb.append(" ").append(parameters.getFamilyName());
// and the rest of the mail body with more appends to the string builder
145
T U T O R IAL S
return sb.toString();
}
But as always it is a hardcoded template for the mail body and the code gets
kinda ugly if the mail message has to be a bit more advanced. But of course
it just works out-of-the-box with just classes already in the JDK.
Lets use a template language instead such as Apache Velocity. As Camel
have a component for Velocity integration we will use this component.
Looking at the Component List overview we can see that camel-velocity
component uses the artifactId camel-velocity so therefore we need to add
this to the pom.xml
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-velocity</artifactId>
<version>${camel-version}</version>
</dependency>
And now we have a Spring conflict as Apache CXF is dependent on Spring
2.0.8 and camel-velocity is dependent on Spring 2.5.5. To remedy this we
could wrestle with the pom.xml with excludes settings in the dependencies
or just bring in another dependency camel-spring:
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-spring</artifactId>
<version>${camel-version}</version>
</dependency>
In fact camel-spring is such a vital part of Camel that you will end up using it
in nearly all situations - we will look into how well Camel is seamless
integration with Spring in part 3. For now its just another dependency.
We create the mail body with the Velocity template and create the file
src/main/resources/MailBody.vm. The content in the MailBody.vm file is:
Incident $body.incidentId has been reported on the $body.incidentDate by
$body.givenName $body.familyName.
The person can be contact by:
- email: $body.email
- phone: $body.phone
Summary: $body.summary
Details:
T U T O R IA L S
146
$body.details
This is an auto generated email. You can not reply.
Letting Camel creating the mail body and storing it as a file is as easy as the
following 3 code lines:
private void generateEmailBodyAndStoreAsFile(InputReportIncident parameters) {
// generate the mail body using velocity template
// notice that we just pass in our POJO (= InputReportIncident) that we
// got from Apache CXF to Velocity.
Object response = template.sendBody("velocity:MailBody.vm", parameters);
// Note: the response is a String and can be cast to String if needed
// store the mail in a file
String filename = "mail-incident-" + parameters.getIncidentId() + ".txt";
template.sendBodyAndHeader("file://target/subfolder", response,
FileComponent.HEADER_FILE_NAME, filename);
}
What is impressive is that we can just pass in our POJO object we got from
Apache CXF to Velocity and it will be able to generate the mail body with this
object in its context. Thus we don't need to prepare anything before we let
Velocity loose and generate our mail body. Notice that the template method
returns a object with out response. This object contains the mail body as a
String object. We can cast to String if needed.
If we run our unit test with mvn test we can in fact see that Camel has
produced the file and we can type its content:
D:\demo\part-two>type target\subfolder\mail-incident-123.txt
Incident 123 has been reported on the 2008-07-16 by Claus Ibsen.
The person can be contact by:
- email: davsclaus@apache.org
- phone: +45 2962 7576
Summary: bla bla
Details:
more bla bla
This is an auto generated email. You can not reply.
147
T U T O R IAL S
FIRST PART OF THE SOLUTION
What we have seen here is actually what it takes to build the first part of the
integration flow. Receiving a request from a webservice, transform it to a
mail body and store it to a file, and return an OK response to the webservice.
All possible within 10 lines of code. So lets wrap it up here is what it takes:
/**
* The webservice we have implemented.
*/
public class ReportIncidentEndpointImpl implements ReportIncidentEndpoint {
private CamelContext camel;
private ProducerTemplate template;
public ReportIncidentEndpointImpl() throws Exception {
// create the camel context that is the "heart" of Camel
camel = new DefaultCamelContext();
// get the ProducerTemplate thst is a Spring'ish xxxTemplate based producer
for very
// easy sending exchanges to Camel.
template = camel.createProducerTemplate();
// start Camel
camel.start();
}
public OutputReportIncident reportIncident(InputReportIncident parameters) {
// transform the request into a mail body
Object mailBody = template.sendBody("velocity:MailBody.vm", parameters);
// store the mail body in a file
String filename = "mail-incident-" + parameters.getIncidentId() + ".txt";
template.sendBodyAndHeader("file://target/subfolder", mailBody,
FileComponent.HEADER_FILE_NAME, filename);
// return an OK reply
OutputReportIncident out = new OutputReportIncident();
out.setCode("OK");
return out;
}
}
Okay I missed by one, its in fact only 9 lines of java code and 2 fields.
END OF PART 2
I know this is a bit different introduction to Camel to how you can start using
it in your projects just as a plain java .jar framework that isn't invasive at all. I
T U T O R IA L S
148
took you through the coding parts that requires 6 - 10 lines to send a
message to an endpoint, buts it's important to show the Message Endpoint
EIP pattern in action and how its implemented in Camel. Yes of course Camel
also has to one liners that you can use, and will use in your projects for
sending messages to endpoints. This part has been about good old plain
java, nothing fancy with Spring, XML files, auto discovery, OGSi or other new
technologies. I wanted to demonstrate the basic building blocks in Camel and
how its setup in pure god old fashioned Java. There are plenty of eye catcher
examples with one liners that does more than you can imagine - we will
come there in the later parts.
Okay part 3 is about building the last pieces of the solution and now it gets
interesting since we have to wrestle with the event driven consumer.
Brew a cup of coffee, tug the kids and kiss the wife, for now we will have us
some fun with the Camel. See you in part 3.
RESOURCES
•
Name
Size
Creator
Creation
Date
Comment
ZIP
Archive
parttwo.zip
17
kB
Claus
Ibsen
Jul 19,
2008
00:52
Â
LINKS
▪
▪
▪
▪
▪
▪
Introduction
Part 1
Part 2
Part 3
Part 4
Part 5
PART 3
RECAP
Lets just recap on the solution we have now:
149
T U T O R IAL S
Â
◦ Properties
◦ Remove
public class ReportIncidentEndpointImpl implements ReportIncidentEndpoint {
private CamelContext camel;
private ProducerTemplate template;
public ReportIncidentEndpointImpl() throws Exception {
// create the camel context that is the "heart" of Camel
camel = new DefaultCamelContext();
// get the ProducerTemplate thst is a Spring'ish xxxTemplate based producer
for very
// easy sending exchanges to Camel.
template = camel.createProducerTemplate();
// start Camel
camel.start();
}
/**
* This is the last solution displayed that is the most simple
*/
public OutputReportIncident reportIncident(InputReportIncident parameters) {
// transform the request into a mail body
Object mailBody = template.sendBody("velocity:MailBody.vm", parameters);
// store the mail body in a file
String filename = "mail-incident-" + parameters.getIncidentId() + ".txt";
template.sendBodyAndHeader("file://target/subfolder", mailBody,
FileComponent.HEADER_FILE_NAME, filename);
// return an OK reply
OutputReportIncident out = new OutputReportIncident();
out.setCode("OK");
return out;
}
}
This completes the first part of the solution: receiving the message using
webservice, transform it to a mail body and store it as a text file.
What is missing is the last part that polls the text files and send them as
emails. Here is where some fun starts, as this requires usage of the Event
Driven Consumer EIP pattern to react when new files arrives. So lets see how
we can do this in Camel. There is a saying: Many roads lead to Rome, and
that is also true for Camel - there are many ways to do it in Camel.
ADDING THE EVENT DRIVEN CONSUMER
We want to add the consumer to our integration that listen for new files, we
do this by creating a private method where the consumer code lives. We
T U T O R IA L S
150
must register our consumer in Camel before its started so we need to add,
and there fore we call the method addMailSenderConsumer in the
constructor below:
public ReportIncidentEndpointImpl() throws Exception {
// create the camel context that is the "heart" of Camel
camel = new DefaultCamelContext();
// get the ProducerTemplate thst is a Spring'ish xxxTemplate based producer
for very
// easy sending exchanges to Camel.
template = camel.createProducerTemplate();
// add the event driven consumer that will listen for mail files and process
them
addMailSendConsumer();
// start Camel
camel.start();
}
The consumer needs to be consuming from an endpoint so we grab the
endpoint from Camel we want to consume. It's file://target/subfolder.
Don't be fooled this endpoint doesn't have to 100% identical to the producer,
i.e. the endpoint we used in the previous part to create and store the files.
We could change the URL to include some options, and to make it more clear
that it's possible we setup a delay value to 10 seconds, and the first poll
starts after 2 seconds. This is done by adding
?consumer.delay=10000&consumer.initialDelay=2000 to the URL.
When we have the endpoint we can create the consumer (just as in part 1
where we created a producer}. Creating the consumer requires a Processor
where we implement the java code what should happen when a message
arrives. To get the mail body as a String object we can use the getBody
method where we can provide the type we want in return.
Sending the email is still left to be implemented, we will do this later. And
finally we must remember to start the consumer otherwise its not active and
won't listen for new files.
private void addMailSendConsumer() throws Exception {
// Grab the endpoint where we should consume. Option - the first poll starts
after 2 seconds
Endpoint endpint = camel.getEndpoint("file://target/
subfolder?consumer.initialDelay=2000");
// create the event
// the Processor is
// (think it as the
Consumer consumer =
151
T U T O R IAL S
driven consumer
the code what should happen when there is an event
onMessage method)
endpint.createConsumer(new Processor() {
URL Configuration
The URL configuration in Camel endpoints is just like regular URL
we know from the Internet. You use ? and & to set the options.
Camel Type Converter
Why don't we just cast it as we always do in Java? Well the biggest
advantage when you provide the type as a parameter you tell
Camel what type you want and Camel can automatically convert it
for you, using its flexible Type Converter mechanism. This is a great
advantage, and you should try to use this instead of regular type
casting.
public void process(Exchange exchange) throws Exception {
// get the mail body as a String
String mailBody = exchange.getIn().getBody(String.class);
// okay now we are read to send it as an email
System.out.println("Sending email..." + mailBody);
}
});
// star the consumer, it will listen for files
consumer.start();
}
Before we test it we need to be aware that our unit test is only catering for
the first part of the solution, receiving the message with webservice,
transforming it using Velocity and then storing it as a file - it doesn't test the
Event Driven Consumer we just added. As we are eager to see it in action, we
just do a common trick adding some sleep in our unit test, that gives our
Event Driven Consumer time to react and print to System.out. We will later
refine the test:
public void testRendportIncident() throws Exception {
...
OutputReportIncident out = client.reportIncident(input);
assertEquals("Response code is wrong", "OK", out.getCode());
// give the event driven consumer time to react
Thread.sleep(10 * 1000);
}
T U T O R IA L S
152
We run the test with mvn clean test and have eyes fixed on the console
output.
During all the output in the console, we see that our consumer has been
triggered, as we want.
2008-07-19 12:09:24,140 [mponent@1f12c4e] DEBUG FileProcessStrategySupport - Locking
the file: target\subfolder\mail-incident-123.txt ...
Sending email...Incident 123 has been reported on the 2008-07-16 by Claus Ibsen.
The person can be contact by:
- email: davsclaus@apache.org
- phone: +45 2962 7576
Summary: bla bla
Details:
more bla bla
This is an auto generated email. You can not reply.
2008-07-19 12:09:24,156 [mponent@1f12c4e] DEBUG FileConsumer - Done processing file:
target\subfolder\mail-incident-123.txt. Status is: OK
SENDING THE EMAIL
Sending the email requires access to a SMTP mail server, but the
implementation code is very simple:
private void sendEmail(String body) {
// send the email to your mail server
String url =
"smtp://someone@localhost?password=secret&to=incident@mycompany.com";
template.sendBodyAndHeader(url, body, "subject", "New incident reported");
}
And just invoke the method from our consumer:
// okay now we are read to send it as an email
System.out.println("Sending email...");
sendEmail(mailBody);
System.out.println("Email sent");
UNIT TESTING MAIL
For unit testing the consumer part we will use a mock mail framework, so we
add this to our pom.xml:
153
T U T O R IAL S
<!-- unit testing mail using mock -->
<dependency>
<groupId>org.jvnet.mock-javamail</groupId>
<artifactId>mock-javamail</artifactId>
<version>1.7</version>
<scope>test</scope>
</dependency>
Then we prepare our integration to run with or without the consumer
enabled. We do this to separate the route into the two parts:
▪ receive the webservice, transform and save mail file and return OK
as repose
▪ the consumer that listen for mail files and send them as emails
So we change the constructor code a bit:
public ReportIncidentEndpointImpl() throws Exception {
init(true);
}
public ReportIncidentEndpointImpl(boolean enableConsumer) throws Exception {
init(enableConsumer);
}
private void init(boolean enableConsumer) throws Exception {
// create the camel context that is the "heart" of Camel
camel = new DefaultCamelContext();
// get the ProducerTemplate thst is a Spring'ish xxxTemplate based producer
for very
// easy sending exchanges to Camel.
template = camel.createProducerTemplate();
// add the event driven consumer that will listen for mail files and process
them
if (enableConsumer) {
addMailSendConsumer();
}
// start Camel
camel.start();
}
Then remember to change the ReportIncidentEndpointTest to pass in
false in the ReportIncidentEndpointImpl constructor.
And as always run mvn clean test to be sure that the latest code changes
works.
T U T O R IA L S
154
ADDING NEW UNIT TEST
We are now ready to add a new unit test that tests the consumer part so we
create a new test class that has the following code structure:
/**
* Plain JUnit test of our consumer.
*/
public class ReportIncidentConsumerTest extends TestCase {
private ReportIncidentEndpointImpl endpoint;
public void testConsumer() throws Exception {
// we run this unit test with the consumer, hence the true parameter
endpoint = new ReportIncidentEndpointImpl(true);
}
}
As we want to test the consumer that it can listen for files, read the file
content and send it as an email to our mailbox we will test it by asserting
that we receive 1 mail in our mailbox and that the mail is the one we expect.
To do so we need to grab the mailbox with the mockmail API. This is done as
simple as:
public void testConsumer() throws Exception {
// we run this unit test with the consumer, hence the true parameter
endpoint = new ReportIncidentEndpointImpl(true);
// get the mailbox
Mailbox box = Mailbox.get("incident@mycompany.com");
assertEquals("Should not have mails", 0, box.size());
How do we trigger the consumer? Well by creating a file in the folder it listen
for. So we could use plain java.io.File API to create the file, but wait isn't there
an smarter solution? ... yes Camel of course. Camel can do amazing stuff in
one liner codes with its ProducerTemplate, so we need to get a hold of this
baby. We expose this template in our ReportIncidentEndpointImpl but adding
this getter:
protected ProducerTemplate getTemplate() {
return template;
}
Then we can use the template to create the file in one code line:
155
T U T O R IAL S
// drop a file in the folder that the consumer listen
// here is a trick to reuse Camel! so we get the producer template and just
// fire a message that will create the file for us
endpoint.getTemplate().sendBodyAndHeader("file://target/
subfolder?append=false", "Hello World",
FileComponent.HEADER_FILE_NAME, "mail-incident-test.txt");
Then we just need to wait a little for the consumer to kick in and do its work
and then we should assert that we got the new mail. Easy as just:
// let the consumer have time to run
Thread.sleep(3 * 1000);
// get the mock mailbox and check if we got mail ;)
assertEquals("Should have got 1 mail", 1, box.size());
assertEquals("Subject wrong", "New incident reported",
box.get(0).getSubject());
assertEquals("Mail body wrong", "Hello World", box.get(0).getContent());
}
The final class for the unit test is:
/**
* Plain JUnit test of our consumer.
*/
public class ReportIncidentConsumerTest extends TestCase {
private ReportIncidentEndpointImpl endpoint;
public void testConsumer() throws Exception {
// we run this unit test with the consumer, hence the true parameter
endpoint = new ReportIncidentEndpointImpl(true);
// get the mailbox
Mailbox box = Mailbox.get("incident@mycompany.com");
assertEquals("Should not have mails", 0, box.size());
// drop a file in the folder that the consumer listen
// here is a trick to reuse Camel! so we get the producer template and just
// fire a message that will create the file for us
endpoint.getTemplate().sendBodyAndHeader("file://target/
subfolder?append=false", "Hello World",
FileComponent.HEADER_FILE_NAME, "mail-incident-test.txt");
// let the consumer have time to run
Thread.sleep(3 * 1000);
// get the mock mailbox and check if we got mail ;)
assertEquals("Should have got 1 mail", 1, box.size());
assertEquals("Subject wrong", "New incident reported",
box.get(0).getSubject());
T U T O R IA L S
156
assertEquals("Mail body wrong", "Hello World", box.get(0).getContent());
}
}
END OF PART 3
Okay we have reached the end of part 3. For now we have only scratched the
surface of what Camel is and what it can do. We have introduced Camel into
our integration piece by piece and slowly added more and more along the
way. And the most important is: you as the developer never lost control.
We hit a sweet spot in the webservice implementation where we could write
our java code. Adding Camel to the mix is just to use it as a regular java
code, nothing magic. We were in control of the flow, we decided when it was
time to translate the input to a mail body, we decided when the content
should be written to a file. This is very important to not lose control, that the
bigger and heavier frameworks tend to do. No names mentioned, but boy do
developers from time to time dislike these elephants. And Camel is no
elephant.
I suggest you download the samples from part 1 to 3 and try them out. It
is great basic knowledge to have in mind when we look at some of the
features where Camel really excel - the routing domain language.
From part 1 to 3 we touched concepts such as::
▪ Endpoint
▪ URI configuration
▪ Consumer
▪ Producer
▪ Event Driven Consumer
▪ Component
▪ CamelContext
▪ ProducerTemplate
▪ Processor
▪ Type Converter
RESOURCES
•
157
Name
T U T O R IAL S
Size
Creator
Creation
Date
Comment
Â
ZIP
Archive
partthree.zip
18
kB
Claus
Ibsen
Jul 20,
2008
03:34
Â
◦ Properties
◦ Remove
LINKS
▪
▪
▪
▪
▪
▪
Introduction
Part 1
Part 2
Part 3
Part 4
Part 5
PART 4
INTRODUCTION
This section is about regular Camel. The examples presented here in this
section is much more in common of all the examples we have in the Camel
documentation.
ROUTING
Camel is particular strong as a light-weight and agile routing and
mediation framework. In this part we will introduce the routing concept
and how we can introduce this into our solution.
Looking back at the figure from the Introduction page we want to implement
this routing. Camel has support for expressing this routing logic using Java as
a DSL (Domain Specific Language). In fact Camel also has DSL for XML and
Scala. In this part we use the Java DSL as its the most powerful and all
developers know Java. Later we will introduce the XML version that is very
well integrated with Spring.
Before we jump into it, we want to state that this tutorial is about
Developers not loosing control. In my humble experience one of the key
fears of developers is that they are forced into a tool/framework where they
loose control and/or power, and the possible is now impossible. So in this
part we stay clear with this vision and our starting point is as follows:
▪ We have generated the webservice source code using the CXF
wsdl2java generator and we have our
T U T O R IA L S
158
If you have been reading the previous 3 parts then, this quote
applies:
you must unlearn what you have learned
Master Yoda, Star Wars IV
So we start all over again!
ReportIncidentEndpointImpl.java file where we as a Developer feels
home and have the power.
So the starting point is:
/**
* The webservice we have implemented.
*/
public class ReportIncidentEndpointImpl implements ReportIncidentEndpoint {
/**
* This is the last solution displayed that is the most simple
*/
public OutputReportIncident reportIncident(InputReportIncident parameters) {
// WE ARE HERE !!!
return null;
}
}
Yes we have a simple plain Java class where we have the implementation of
the webservice. The cursor is blinking at the WE ARE HERE block and this is
where we feel home. More or less any Java Developers have implemented
webservices using a stack such as: Apache AXIS, Apache CXF or some other
quite popular framework. They all allow the developer to be in control and
implement the code logic as plain Java code. Camel of course doesn't enforce
this to be any different. Okay the boss told us to implement the solution from
the figure in the Introduction page and we are now ready to code.
RouteBuilder
RouteBuilder is the hearth in Camel of the Java DSL routing. This class does
all the heavy lifting of supporting EIP verbs for end-users to express the
routing. It does take a little while to get settled and used to, but when you
have worked with it for a while you will enjoy its power and realize it is in fact
a little language inside Java itself. Camel is the only integration framework
we are aware of that has Java DSL, all the others are usually only XML based.
159
T U T O R IAL S
As an end-user you usually use the RouteBuilder as of follows:
▪ create your own Route class that extends RouteBuilder
▪ implement your routing DSL in the configure method
So we create a new class ReportIncidentRoutes and implement the first part
of the routing:
import org.apache.camel.builder.RouteBuilder;
public class ReportIncidentRoutes extends RouteBuilder {
public void configure() throws Exception {
// direct:start is a internal queue to kick-start the routing in our example
// we use this as the starting point where you can send messages to
direct:start
from("direct:start")
// to is the destination we send the message to our velocity endpoint
// where we transform the mail body
.to("velocity:MailBody.vm");
}
}
What to notice here is the configure method. Here is where all the action is.
Here we have the Java DSL langauge, that is expressed using the fluent
builder syntax that is also known from Hibernate when you build the
dynamic queries etc. What you do is that you can stack methods separating
with the dot.
In the example above we have a very common routing, that can be
distilled from pseudo verbs to actual code with:
▪ from A to B
▪ From Endpoint A To Endpoint B
▪ from("endpointA").to("endpointB")
▪ from("direct:start").to("velocity:MailBody.vm");
from("direct:start") is the consumer that is kick-starting our routing flow. It
will wait for messages to arrive on the direct queue and then dispatch the
message.
to("velocity:MailBody.vm") is the producer that will receive a message
and let Velocity generate the mail body response.
So what we have implemented so far with our ReportIncidentRoutes
RouteBuilder is this part of the picture:
T U T O R IA L S
160
Adding the RouteBuilder
Now we have our RouteBuilder we need to add/connect it to our
CamelContext that is the hearth of Camel. So turning back to our webservice
implementation class ReportIncidentEndpointImpl we add this constructor to
the code, to create the CamelContext and add the routes from our route
builder and finally to start it.
private CamelContext context;
public ReportIncidentEndpointImpl() throws Exception {
// create the context
context = new DefaultCamelContext();
// append the routes to the context
context.addRoutes(new ReportIncidentRoutes());
// at the end start the camel context
context.start();
}
Okay how do you use the routes then? Well its just as before we use a
ProducerTemplate to send messages to Endpoints, so we just send to the
direct:start endpoint and it will take it from there.
So we implement the logic in our webservice operation:
/**
* This is the last solution displayed that is the most simple
*/
public OutputReportIncident reportIncident(InputReportIncident parameters) {
Object mailBody = context.createProducerTemplate().sendBody("direct:start",
parameters);
System.out.println("Body:" + mailBody);
// return an OK reply
OutputReportIncident out = new OutputReportIncident();
out.setCode("OK");
return out;
}
Notice that we get the producer template using the
createProducerTemplate method on the CamelContext. Then we send the
input parameters to the direct:start endpoint and it will route it to the
velocity endpoint that will generate the mail body. Since we use direct as
the consumer endpoint (=from) and its a synchronous exchange we will get
the response back from the route. And the response is of course the output
from the velocity endpoint.
161
T U T O R IAL S
About creating ProducerTemplate
In the example above we create a new ProducerTemplate when
the reportIncident method is invoked. However in reality you
should only create the template once and re-use it. See this FAQ
entry.
We have now completed this part of the picture:
UNIT TESTING
Now is the time we would like to unit test what we got now. So we call for
camel and its great test kit. For this to work we need to add it to the pom.xml
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-core</artifactId>
<version>1.4.0</version>
<scope>test</scope>
<type>test-jar</type>
</dependency>
After adding it to the pom.xml you should refresh your Java Editor so it
pickups the new jar. Then we are ready to create out unit test class.
We create this unit test skeleton, where we extend this class
ContextTestSupport
package org.apache.camel.example.reportincident;
import org.apache.camel.ContextTestSupport;
import org.apache.camel.builder.RouteBuilder;
/**
* Unit test of our routes
*/
public class ReportIncidentRoutesTest extends ContextTestSupport {
T U T O R IA L S
162
}
ContextTestSupport is a supporting unit test class for much easier unit
testing with Apache Camel. The class is extending JUnit TestCase itself so you
get all its glory. What we need to do now is to somehow tell this unit test
class that it should use our route builder as this is the one we gonna test. So
we do this by implementing the createRouteBuilder method.
@Override
protected RouteBuilder createRouteBuilder() throws Exception {
return new ReportIncidentRoutes();
}
That is easy just return an instance of our route builder and this unit test will
use our routes.
We then code our unit test method that sends a message to the route and
assert that its transformed to the mail body using the Velocity template.
public void testTransformMailBody() throws Exception {
// create a dummy input with some input data
InputReportIncident parameters = createInput();
// send the message (using the sendBody method that takes a parameters as the
input body)
// to "direct:start" that kick-starts the route
// the response is returned as the out object, and its also the body of the
response
Object out = context.createProducerTemplate().sendBody("direct:start",
parameters);
// convert the response to a string using camel converters. However we could
also have casted it to
// a string directly but using the type converters ensure that Camel can
convert it if it wasn't a string
// in the first place. The type converters in Camel is really powerful and
you will later learn to
// appreciate them and wonder why its not build in Java out-of-the-box
String body = context.getTypeConverter().convertTo(String.class, out);
// do some simple assertions of the mail body
assertTrue(body.startsWith("Incident 123 has been reported on the 2008-07-16
by Claus Ibsen."));
}
/**
* Creates a dummy request to be used for input
*/
protected InputReportIncident createInput() {
163
T U T O R IAL S
It is quite common in Camel itself to unit test using routes defined
as an anonymous inner class, such as illustrated below:
protected RouteBuilder createRouteBuilder() throws Exception {
return new RouteBuilder() {
public void configure() throws Exception {
// TODO: Add your routes here, such as:
from("jms:queue:inbox").to("file://target/out");
}
};
}
The same technique is of course also possible for end-users of Camel to
create parts of your routes and test them separately in many test classes.
However in this tutorial we test the real route that is to be used for
production, so we just return an instance of the real one.
InputReportIncident input = new InputReportIncident();
input.setIncidentId("123");
input.setIncidentDate("2008-07-16");
input.setGivenName("Claus");
input.setFamilyName("Ibsen");
input.setSummary("bla bla");
input.setDetails("more bla bla");
input.setEmail("davsclaus@apache.org");
input.setPhone("+45 2962 7576");
return input;
}
ADDING THE FILE BACKUP
The next piece of puzzle that is missing is to store the mail body as a backup
file. So we turn back to our route and the EIP patterns. We use the Pipes and
Filters pattern here to chain the routing as:
public void configure() throws Exception {
from("direct:start")
.to("velocity:MailBody.vm")
// using pipes-and-filters we send the output from the previous to the
next
.to("file://target/subfolder");
}
T U T O R IA L S
164
Notice that we just add a 2nd .to on the newline. Camel will default use the
Pipes and Filters pattern here when there are multi endpoints chained liked
this. We could have used the pipeline verb to let out stand out that its the
Pipes and Filters pattern such as:
from("direct:start")
// using pipes-and-filters we send the output from the previous to the
next
.pipeline("velocity:MailBody.vm", "file://target/subfolder");
But most people are using the multi .to style instead.
We re-run out unit test and verifies that it still passes:
Running org.apache.camel.example.reportincident.ReportIncidentRoutesTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 1.157 sec
But hey we have added the file producer endpoint and thus a file should also
be created as the backup file. If we look in the target/subfolder we can
see that something happened.
On my humble laptop it created this folder: target\subfolder\ID-clausacer. So the file producer create a sub folder named ID-claus-acer what is
this? Well Camel auto generates an unique filename based on the unique
message id if not given instructions to use a fixed filename. In fact it creates
another sub folder and name the file as: target\subfolder\ID-clausacer\3750-1219148558921\1-0 where 1-0 is the file with the mail body. What
we want is to use our own filename instead of this auto generated filename.
This is archived by adding a header to the message with the filename to use.
So we need to add this to our route and compute the filename based on the
message content.
Setting the filename
For starters we show the simple solution and build from there. We start by
setting a constant filename, just to verify that we are on the right path, to
instruct the file producer what filename to use. The file producer uses a
special header FileComponent.HEADER_FILE_NAME to set the filename.
What we do is to send the header when we "kick-start" the routing as the
header will be propagated from the direct queue to the file producer. What
we need to do is to use the ProducerTemplate.sendBodyAndHeader method
that takes both a body and a header. So we change out webservice code to
include the filename also:
165
T U T O R IAL S
public OutputReportIncident reportIncident(InputReportIncident parameters) {
// create the producer template to use for sending messages
ProducerTemplate producer = context.createProducerTemplate();
// send the body and the filename defined with the special header key
Object mailBody = producer.sendBodyAndHeader("direct:start", parameters,
FileComponent.HEADER_FILE_NAME, "incident.txt");
System.out.println("Body:" + mailBody);
// return an OK reply
OutputReportIncident out = new OutputReportIncident();
out.setCode("OK");
return out;
}
However we could also have used the route builder itself to configure the
constant filename as shown below:
public void configure() throws Exception {
from("direct:start")
.to("velocity:MailBody.vm")
// set the filename to a constant before the file producer receives the
message
.setHeader(FileComponent.HEADER_FILE_NAME, constant("incident.txt"))
.to("file://target/subfolder");
}
But Camel can be smarter and we want to dynamic set the filename based
on some of the input parameters, how can we do this?
Well the obvious solution is to compute and set the filename from the
webservice implementation, but then the webservice implementation has
such logic and we want this decoupled, so we could create our own POJO
bean that has a method to compute the filename. We could then instruct the
routing to invoke this method to get the computed filename. This is a string
feature in Camel, its Bean binding. So lets show how this can be done:
Using Bean Language to compute the filename
First we create our plain java class that computes the filename, and it has
100% no dependencies to Camel what so ever.
/**
* Plain java class to be used for filename generation based on the reported incident
*/
public class FilenameGenerator {
public String generateFilename(InputReportIncident input) {
// compute the filename
T U T O R IA L S
166
return "incident-" + input.getIncidentId() + ".txt";
}
}
The class is very simple and we could easily create unit tests for it to verify
that it works as expected. So what we want now is to let Camel invoke this
class and its generateFilename with the input parameters and use the output
as the filename. Pheeeww is this really possible out-of-the-box in Camel? Yes
it is. So lets get on with the show. We have the code that computes the
filename, we just need to call it from our route using the Bean Language:
public void configure() throws Exception {
from("direct:start")
// set the filename using the bean language and call the
FilenameGenerator class.
// the 2nd null parameter is optional methodname, to be used to avoid
ambiguity.
// if not provided Camel will try to figure out the best method to
invoke, as we
// only have one method this is very simple
.setHeader(FileComponent.HEADER_FILE_NAME,
BeanLanguage.bean(FilenameGenerator.class, null))
.to("velocity:MailBody.vm")
.to("file://target/subfolder");
}
Notice that we use the bean language where we supply the class with our
bean to invoke. Camel will instantiate an instance of the class and invoke the
suited method. For completeness and ease of code readability we add the
method name as the 2nd parameter
.setHeader(FileComponent.HEADER_FILE_NAME,
BeanLanguage.bean(FilenameGenerator.class, "generateFilename"))
Then other developers can understand what the parameter is, instead of
null.
Now we have a nice solution, but as a sidetrack I want to demonstrate the
Camel has other languages out-of-the-box, and that scripting language is a
first class citizen in Camel where it etc. can be used in content based routing.
However we want it to be used for the filename generation.
167
T U T O R IAL S
Using a script language to set the filename
We could do as in the previous parts where we send the computed
filename as a message header when we "kick-start" the route. But we want
to learn new stuff so we look for a different solution using some of Camels
many Languages. As OGNL is a favorite language of mine (used by
WebWork) so we pick this baby for a Camel ride. For starters we must add
it to our pom.xml:
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-ognl</artifactId>
<version>${camel-version}</version>
</dependency>
And remember to refresh your editor so you got the new .jars.
We want to construct the filename based on this syntax: mail-incident#ID#.txt where #ID# is the incident id from the input parameters. As
OGNL is a language that can invoke methods on bean we can invoke the
getIncidentId() on the message body and then concat it with the fixed
pre and postfix strings.
In OGNL glory this is done as:
"'mail-incident-' + request.body.incidentId + '.txt'"
where request.body.incidentId computes to:
▪ request is the IN message. See the OGNL for other
predefined objects available
▪ body is the body of the in message
▪ incidentId will invoke the getIncidentId() method on the
body.
The rest is just more or less regular plain code where we
can concat strings.
Now we got the expression to dynamic compute the filename on the fly we
need to set it on our route so we turn back to our route, where we can add
the OGNL expression:
T U T O R IA L S
168
public void configure() throws Exception {
from("direct:start")
// we need to set the filename and uses OGNL for this
.setHeader(FileComponent.HEADER_FILE_NAME,
OgnlExpression.ognl("'mail-incident-' + request.body.incidentId + '.txt'"))
// using pipes-and-filters we send the output from the previous
to the next
.pipeline("velocity:MailBody.vm", "file://target/subfolder");
}
And since we are on Java 1.5 we can use the static import of ognl so we
have:
import static org.apache.camel.language.ognl.OgnlExpression.ognl;
...
.setHeader(FileComponent.HEADER_FILE_NAME, ognl("'mail-incident-' +
request.body.incidentId + '.txt'"))
Notice the import static also applies for all the other languages, such as the
Bean Language we used previously.
Whatever worked for you we have now implemented the backup of the data
files:
SENDING THE EMAIL
What we need to do before the solution is completed is to actually send the
email with the mail body we generated and stored as a file. In the previous
part we did this with a File consumer, that we manually added to the
CamelContext. We can do this quite easily with the routing.
import org.apache.camel.builder.RouteBuilder;
169
T U T O R IAL S
public class ReportIncidentRoutes extends RouteBuilder {
public void configure() throws Exception {
// first part from the webservice -> file backup
from("direct:start")
.setHeader(FileComponent.HEADER_FILE_NAME, bean(FilenameGenerator.class,
"generateFilename"))
.to("velocity:MailBody.vm")
.to("file://target/subfolder");
// second part from the file backup -> send email
from("file://target/subfolder")
// set the subject of the email
.setHeader("subject", constant("new incident reported"))
// send the email
.to("smtp://someone@localhost?password=secret&to=incident@mycompany.com");
}
}
The last 3 lines of code does all this. It adds a file consumer
from("file://target/subfolder"), sets the mail subject, and finally send it as
an email.
The DSL is really powerful where you can express your routing integration
logic.
So we completed the last piece in the picture puzzle with just 3 lines of code.
We have now completed the integration:
CONCLUSION
We have just briefly touched the routing in Camel and shown how to
implement them using the fluent builder syntax in Java. There is much
more to the routing in Camel than shown here, but we are learning step by
step. We continue in part 5. See you there.
RESOURCES
•
T U T O R IA L S
170
Name
Size
Creator
Creation
Date
Comment
ZIP
Archive
partfour.zip
11
kB
Claus
Ibsen
Aug 25,
2008
07:24
Â
Â
◦ Properties
◦ Remove
LINKS
▪
▪
▪
▪
▪
▪
Introduction
Part 1
Part 2
Part 3
Part 4
Part 5
BETTER JMS TRANSPORT FOR CXF WEBSERVICE USING
APACHE CAMEL
Configuring JMS in Apache CXF before Version 2.1.3 is possible but not really
easy or nice. This article shows how to use Apache Camel to provide a better
JMS Transport for CXF.
Update: Since CXF 2.1.3 there is a new way of configuring JMS (Using the
JMSConfigFeature). It makes JMS config for CXF as easy as with Camel. Using
Camel for JMS is still a good idea if you want to use the rich feature of Camel
for routing and other Integration Scenarios that CXF does not support.
You can find the original announcement for this Tutorial and some
additional info on Christian Schneider´s Blog
So how to connect Apache Camel and CXF
The best way to connect Camel and CXF is using the Camel transport for
CXF. This is a camel module that registers with cxf as a new transport. It is
quite easy to configure.
<bean class="org.apache.camel.component.cxf.transport.CamelTransportFactory">
<property name="bus" ref="cxf" />
<property name="camelContext" ref="camelContext" />
<property name="transportIds">
<list>
<value>http://cxf.apache.org/transports/camel</value>
171
T U T O R IAL S
</list>
</property>
</bean>
This bean registers with CXF and provides a new transport prefix camel://
that can be used in CXF address configurations. The bean references a bean
cxf which will be already present in your config. The other refrenceis a camel
context. We will later define this bean to provide the routing config.
How is JMS configured in Camel
In camel you need two things to configure JMS. A ConnectionFactory and a
JMSComponent. As ConnectionFactory you can simply set up the normal
Factory your JMS provider offers or bind a JNDI ConnectionFactory. In this
example we use the ConnectionFactory provided by ActiveMQ.
<bean id="jmsConnectionFactory" class="org.apache.activemq.ActiveMQConnectionFactory">
<property name="brokerURL" value="tcp://localhost:61616" />
</bean>
Then we set up the JMSComponent. It offers a new transport prefix to camel
that we simply call jms. If we need several JMSComponents we can
differentiate them by their name.
<bean id="jms" class="org.apache.camel.component.jms.JmsComponent">
<property name="connectionFactory" ref="jmsConnectionFactory" />
<property name="useMessageIDAsCorrelationID" value="true" />
</bean>
You can find more details about the JMSComponent at the Camel Wiki. For
example you find the complete configuration options and a JNDI sample
there.
Setting up the CXF client
We will configure a simple CXF webservice client. It will use stub code
generated from a wsdl. The webservice client will be configured to use JMS
directly. You can also use a direct: Endpoint and do the routing to JMS in the
Camel Context.
<client id="CustomerService" xmlns="http://cxf.apache.org/jaxws"
xmlns:customer="http://customerservice.example.com/"
serviceName="customer:CustomerServiceService"
endpointName="customer:CustomerServiceEndpoint"
T U T O R IA L S
172
address="camel:jms:queue:CustomerService"
serviceClass="com.example.customerservice.CustomerService">
</client>
We explicitly configure serviceName and endpointName so they are not read
from the wsdl. The names we use are arbitrary and have no further function
but we set them to look nice. The serviceclass points to the service interface
that was generated from the wsdl. Now the important thing is address. Here
we tell cxf to use the camel transport, use the JmsComponent who registered
the prefix "jms" and use the queue "CustomerService".
Setting up the CamelContext
As we do not need additional routing an empty CamelContext bean will
suffice.
<camelContext id="camelContext" xmlns="http://activemq.apache.org/camel/schema/
spring">
</camelContext>
Running the Example
• Download the example project here
• Follow the readme.txt
Conclusion
As you have seen in this example you can use Camel to connect services to
JMS easily while being able to also use the rich integration features of Apache
Camel.
TUTORIAL USING AXIS 1.4 WITH APACHE CAMEL
•
•
•
•
•
•
•
•
•
173
Tutorial using Axis 1.4 with Apache Camel
Prerequisites
Distribution
Introduction
Setting up the project to run Axis
Maven 2
wsdl
Configuring Axis
Running the Example
T U T O R IAL S
•
•
•
•
•
•
•
•
•
•
•
•
Integrating Spring
Using Spring
Integrating Camel
CamelContext
Store a file backup
Running the example
Unit Testing
Smarter Unit Testing with Spring
Unit Test calling WebService
Annotations
The End
See Also
Prerequisites
This tutorial uses Maven 2 to setup the Camel project and for dependencies
for artifacts.
Distribution
This sample is distributed with the Camel 1.5 distribution as examples/
camel-example-axis.
Introduction
Apache Axis is/was widely used as a webservice framework. So in line with
some of the other tutorials to demonstrate how Camel is not an invasive
framework but is flexible and integrates well with existing solution.
We have an existing solution that exposes a webservice using Axis 1.4
deployed as web applications. This is a common solution. We use contract
first so we have Axis generated source code from an existing wsdl file. Then
we show how we introduce Spring and Camel to integrate with Axis.
This tutorial uses the following frameworks:
• Maven 2.0.9
• Apache Camel 1.5.0
• Apache Axis 1.4
• Spring 2.5.5
Setting up the project to run Axis
This first part is about getting the project up to speed with Axis. We are not
touching Camel or Spring at this time.
T U T O R IA L S
174
Maven 2
Axis dependencies is available for maven 2 so we configure our pom.xml as:
<dependency>
<groupId>org.apache.axis</groupId>
<artifactId>axis</artifactId>
<version>1.4</version>
</dependency>
<dependency>
<groupId>org.apache.axis</groupId>
<artifactId>axis-jaxrpc</artifactId>
<version>1.4</version>
</dependency>
<dependency>
<groupId>org.apache.axis</groupId>
<artifactId>axis-saaj</artifactId>
<version>1.4</version>
</dependency>
<dependency>
<groupId>axis</groupId>
<artifactId>axis-wsdl4j</artifactId>
<version>1.5.1</version>
</dependency>
<dependency>
<groupId>commons-discovery</groupId>
<artifactId>commons-discovery</artifactId>
<version>0.4</version>
</dependency>
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.14</version>
</dependency>
Then we need to configure maven to use Java 1.5 and the Axis maven plugin
that generates the source code based on the wsdl file:
<!-- to compile with 1.5 -->
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<source>1.5</source>
<target>1.5</target>
</configuration>
</plugin>
175
T U T O R IAL S
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>axistools-maven-plugin</artifactId>
<configuration>
<sourceDirectory>src/main/resources/</sourceDirectory>
<packageSpace>com.mycompany.myschema</packageSpace>
<testCases>false</testCases>
<serverSide>true</serverSide>
<subPackageByFileName>false</subPackageByFileName>
</configuration>
<executions>
<execution>
<goals>
<goal>wsdl2java</goal>
</goals>
</execution>
</executions>
</plugin>
wsdl
We use the same .wsdl file as the Tutorial-Example-ReportIncident and copy
it to src/main/webapp/WEB-INF/wsdl
<?xml version="1.0" encoding="ISO-8859-1"?>
<wsdl:definitions xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/"
xmlns:tns="http://reportincident.example.camel.apache.org"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:http="http://schemas.xmlsoap.org/wsdl/http/"
xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/"
targetNamespace="http://reportincident.example.camel.apache.org">
<!-- Type definitions for input- and output parameters for webservice -->
<wsdl:types>
<xs:schema targetNamespace="http://reportincident.example.camel.apache.org">
<xs:element name="inputReportIncident">
<xs:complexType>
<xs:sequence>
<xs:element type="xs:string"
name="incidentId"/>
<xs:element type="xs:string"
name="incidentDate"/>
<xs:element type="xs:string"
name="givenName"/>
<xs:element type="xs:string"
name="familyName"/>
<xs:element type="xs:string"
name="summary"/>
<xs:element type="xs:string"
T U T O R IA L S
176
name="details"/>
<xs:element type="xs:string"
name="email"/>
<xs:element type="xs:string"
name="phone"/>
</xs:sequence>
</xs:complexType>
</xs:element>
<xs:element name="outputReportIncident">
<xs:complexType>
<xs:sequence>
<xs:element type="xs:string"
name="code"/>
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:schema>
</wsdl:types>
<!-- Message definitions for input and output -->
<wsdl:message name="inputReportIncident">
<wsdl:part name="parameters" element="tns:inputReportIncident"/>
</wsdl:message>
<wsdl:message name="outputReportIncident">
<wsdl:part name="parameters" element="tns:outputReportIncident"/>
</wsdl:message>
<!-- Port (interface) definitions -->
<wsdl:portType name="ReportIncidentEndpoint">
<wsdl:operation name="ReportIncident">
<wsdl:input message="tns:inputReportIncident"/>
<wsdl:output message="tns:outputReportIncident"/>
</wsdl:operation>
</wsdl:portType>
<!-- Port bindings to transports and encoding - HTTP, document literal
encoding is used -->
<wsdl:binding name="ReportIncidentBinding" type="tns:ReportIncidentEndpoint">
<soap:binding transport="http://schemas.xmlsoap.org/soap/http"/>
<wsdl:operation name="ReportIncident">
<soap:operation
soapAction="http://reportincident.example.camel.apache.org/ReportIncident"
style="document"/>
<wsdl:input>
<soap:body parts="parameters" use="literal"/>
</wsdl:input>
<wsdl:output>
<soap:body parts="parameters" use="literal"/>
</wsdl:output>
</wsdl:operation>
</wsdl:binding>
<!-- Service definition -->
177
T U T O R IAL S
<wsdl:service name="ReportIncidentService">
<wsdl:port name="ReportIncidentPort"
binding="tns:ReportIncidentBinding">
<soap:address
location="http://reportincident.example.camel.apache.org"/>
</wsdl:port>
</wsdl:service>
</wsdl:definitions>
Configuring Axis
Okay we are now setup for the contract first development and can generate
the source file. For now we are still only using standard Axis and not Spring
nor Camel. We still need to setup Axis as a web application so we configure
the web.xml in src/main/webapp/WEB-INF/web.xml as:
<servlet>
<servlet-name>axis</servlet-name>
<servlet-class>org.apache.axis.transport.http.AxisServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>axis</servlet-name>
<url-pattern>/services/*</url-pattern>
</servlet-mapping>
The web.xml just registers Axis servlet that is handling the incoming web
requests to its servlet mapping. We still need to configure Axis itself and this
is done using its special configuration file server-config.wsdd. We nearly
get this file for free if we let Axis generate the source code so we run the
maven goal:
mvn axistools:wsdl2java
The tool will generate the source code based on the wsdl and save the files
to the following folder:
.\target\generated-sources\axistools\wsdl2java\org\apache\camel\example\reportincident
deploy.wsdd
InputReportIncident.java
OutputReportIncident.java
ReportIncidentBindingImpl.java
ReportIncidentBindingStub.java
ReportIncidentService_PortType.java
T U T O R IA L S
178
ReportIncidentService_Service.java
ReportIncidentService_ServiceLocator.java
undeploy.wsdd
This is standard Axis and so far no Camel or Spring has been touched. To
implement our webservice we will add our code, so we create a new class
AxisReportIncidentService that implements the port type interface where
we can implement our code logic what happens when the webservice is
invoked.
package org.apache.camel.example.axis;
import org.apache.camel.example.reportincident.InputReportIncident;
import org.apache.camel.example.reportincident.OutputReportIncident;
import org.apache.camel.example.reportincident.ReportIncidentService_PortType;
import java.rmi.RemoteException;
/**
* Axis webservice
*/
public class AxisReportIncidentService implements ReportIncidentService_PortType {
public OutputReportIncident reportIncident(InputReportIncident parameters) throws
RemoteException {
System.out.println("Hello AxisReportIncidentService is called from " +
parameters.getGivenName());
OutputReportIncident out = new OutputReportIncident();
out.setCode("OK");
return out;
}
}
Now we need to configure Axis itself and this is done using its serverconfig.wsdd file. We nearly get this for for free from the auto generated
code, we copy the stuff from deploy.wsdd and made a few modifications:
<?xml version="1.0" encoding="UTF-8"?>
<deployment xmlns="http://xml.apache.org/axis/wsdd/"
xmlns:java="http://xml.apache.org/axis/wsdd/providers/java">
<!-- global configuration -->
<globalConfiguration>
<parameter name="sendXsiTypes" value="true"/>
<parameter name="sendMultiRefs" value="true"/>
<parameter name="sendXMLDeclaration" value="true"/>
<parameter name="axis.sendMinimizedElements" value="true"/>
</globalConfiguration>
179
T U T O R IAL S
<handler name="URLMapper"
type="java:org.apache.axis.handlers.http.URLMapper"/>
<!-- this service is from deploy.wsdd -->
<service name="ReportIncidentPort" provider="java:RPC" style="document"
use="literal">
<parameter name="wsdlTargetNamespace"
value="http://reportincident.example.camel.apache.org"/>
<parameter name="wsdlServiceElement" value="ReportIncidentService"/>
<parameter name="schemaUnqualified"
value="http://reportincident.example.camel.apache.org"/>
<parameter name="wsdlServicePort" value="ReportIncidentPort"/>
<parameter name="className"
value="org.apache.camel.example.reportincident.ReportIncidentBindingImpl"/>
<parameter name="wsdlPortType" value="ReportIncidentService"/>
<parameter name="typeMappingVersion" value="1.2"/>
<operation name="reportIncident" qname="ReportIncident"
returnQName="retNS:outputReportIncident"
xmlns:retNS="http://reportincident.example.camel.apache.org"
returnType="rtns:>outputReportIncident"
xmlns:rtns="http://reportincident.example.camel.apache.org"
soapAction="http://reportincident.example.camel.apache.org/
ReportIncident" >
<parameter qname="pns:inputReportIncident"
xmlns:pns="http://reportincident.example.camel.apache.org"
type="tns:>inputReportIncident"
xmlns:tns="http://reportincident.example.camel.apache.org"/>
</operation>
<parameter name="allowedMethods" value="reportIncident"/>
<typeMapping
xmlns:ns="http://reportincident.example.camel.apache.org"
qname="ns:>outputReportIncident"
type="java:org.apache.camel.example.reportincident.OutputReportIncident"
serializer="org.apache.axis.encoding.ser.BeanSerializerFactory"
deserializer="org.apache.axis.encoding.ser.BeanDeserializerFactory"
encodingStyle=""
/>
<typeMapping
xmlns:ns="http://reportincident.example.camel.apache.org"
qname="ns:>inputReportIncident"
type="java:org.apache.camel.example.reportincident.InputReportIncident"
serializer="org.apache.axis.encoding.ser.BeanSerializerFactory"
deserializer="org.apache.axis.encoding.ser.BeanDeserializerFactory"
encodingStyle=""
/>
</service>
<!-- part of Axis configuration -->
<transport name="http">
<requestFlow>
<handler type="URLMapper"/>
<handler
type="java:org.apache.axis.handlers.http.HTTPAuthHandler"/>
T U T O R IA L S
180
</requestFlow>
</transport>
</deployment>
The globalConfiguration and transport is not in the deploy.wsdd file so
you gotta write that yourself. The service is a 100% copy from deploy.wsdd.
Axis has more configuration to it than shown here, but then you should check
the Axis documentation.
What we need to do now is important, as we need to modify the above
configuration to use our webservice class than the default one, so we change
the classname parameter to our class AxisReportIncidentService:
<parameter name="className"
value="org.apache.camel.example.axis.AxisReportIncidentService"/>
Running the Example
Now we are ready to run our example for the first time, so we use Jetty as
the quick web container using its maven command:
mvn jetty:run
Then we can hit the web browser and enter this URL:
http://localhost:8080/camel-example-axis/services and you should
see the famous Axis start page with the text And now... Some Services.
Clicking on the .wsdl link shows the wsdl file, but what. It's an auto
generated one and not our original .wsdl file. So we need to fix this ASAP and
this is done by configuring Axis in the server-config.wsdd file:
<service name="ReportIncidentPort" provider="java:RPC" style="document"
use="literal">
<wsdlFile>/WEB-INF/wsdl/report_incident.wsdl</wsdlFile>
...
We do this by adding the wsdlFile tag in the service element where we can
point to the real .wsdl file.
Integrating Spring
First we need to add its dependencies to the pom.xml.
181
T U T O R IAL S
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-web</artifactId>
<version>2.5.5</version>
</dependency>
Spring is integrated just as it would like to, we add its listener to the web.xml
and a context parameter to be able to configure precisely what spring xml
files to use:
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>
classpath:axis-example-context.xml
</param-value>
</context-param>
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
Next is to add a plain spring XML file named axis-example-context.xml in
the src/main/resources folder.
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/
schema/beans/spring-beans-2.5.xsd">
</beans>
The spring XML file is currently empty. We hit jetty again with mvn jetty:run
just to make sure Spring was setup correctly.
Using Spring
We would like to be able to get hold of the Spring ApplicationContext from
our webservice so we can get access to the glory spring, but how do we do
this? And our webservice class AxisReportIncidentService is created and
managed by Axis we want to let Spring do this. So we have two problems.
We solve these problems by creating a delegate class that Axis creates,
and this delegate class gets hold on Spring and then gets our real webservice
as a spring bean and invoke the service.
T U T O R IA L S
182
First we create a new class that is 100% independent from Axis and just a
plain POJO. This is our real service.
package org.apache.camel.example.axis;
import org.apache.camel.example.reportincident.InputReportIncident;
import org.apache.camel.example.reportincident.OutputReportIncident;
/**
* Our real service that is not tied to Axis
*/
public class ReportIncidentService {
public OutputReportIncident reportIncident(InputReportIncident parameters) {
System.out.println("Hello ReportIncidentService is called from " +
parameters.getGivenName());
OutputReportIncident out = new OutputReportIncident();
out.setCode("OK");
return out;
}
}
So now we need to get from AxisReportIncidentService to this one
ReportIncidentService using Spring. Well first of all we add our real service to
spring XML configuration file so Spring can handle its lifecycle:
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/
schema/beans/spring-beans-2.5.xsd">
<bean id="incidentservice"
class="org.apache.camel.example.axis.ReportIncidentService"/>
</beans>
And then we need to modify AxisReportIncidentService to use Spring to
lookup the spring bean id="incidentservice" and delegate the call. We do
this by extending the spring class
org.springframework.remoting.jaxrpc.ServletEndpointSupport so the
refactored code is:
package org.apache.camel.example.axis;
import org.apache.camel.example.reportincident.InputReportIncident;
import org.apache.camel.example.reportincident.OutputReportIncident;
183
T U T O R IAL S
import org.apache.camel.example.reportincident.ReportIncidentService_PortType;
import org.springframework.remoting.jaxrpc.ServletEndpointSupport;
import java.rmi.RemoteException;
/**
* Axis webservice
*/
public class AxisReportIncidentService extends ServletEndpointSupport implements
ReportIncidentService_PortType {
public OutputReportIncident reportIncident(InputReportIncident parameters) throws
RemoteException {
// get hold of the spring bean from the application context
ReportIncidentService service = (ReportIncidentService)
getApplicationContext().getBean("incidentservice");
// delegate to the real service
return service.reportIncident(parameters);
}
}
To see if everything is okay we run mvn jetty:run.
In the code above we get hold of our service at each request by looking up
in the application context. However Spring also supports an init method
where we can do this once. So we change the code to:
public class AxisReportIncidentService extends ServletEndpointSupport implements
ReportIncidentService_PortType {
private ReportIncidentService service;
@Override
protected void onInit() throws ServiceException {
// get hold of the spring bean from the application context
service = (ReportIncidentService)
getApplicationContext().getBean("incidentservice");
}
public OutputReportIncident reportIncident(InputReportIncident parameters) throws
RemoteException {
// delegate to the real service
return service.reportIncident(parameters);
}
}
So now we have integrated Axis with Spring and we are ready for Camel.
T U T O R IA L S
184
Integrating Camel
Again the first step is to add the dependencies to the maven pom.xml file:
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-core</artifactId>
<version>1.5.0</version>
</dependency>
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-spring</artifactId>
<version>1.5.0</version>
</dependency>
Now that we have integrated with Spring then we easily integrate with Camel
as Camel works well with Spring.
We choose to integrate Camel in the Spring XML file so we add the camel
namespace and the schema location:
xmlns:camel="http://activemq.apache.org/camel/schema/spring"
http://activemq.apache.org/camel/schema/spring http://activemq.apache.org/camel/
schema/spring/camel-spring.xsd"
CamelContext
CamelContext is the heart of Camel its where all the routes, endpoints,
components, etc. is registered. So we setup a CamelContext and the spring
XML files looks like:
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:camel="http://activemq.apache.org/camel/schema/spring"
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/
schema/beans/spring-beans-2.5.xsd
http://activemq.apache.org/camel/schema/spring http://activemq.apache.org/
camel/schema/spring/camel-spring.xsd">
<bean id="incidentservice"
class="org.apache.camel.example.axis.ReportIncidentService"/>
<camel:camelContext id="camel">
<!-- TODO: Here we can add Camel stuff -->
</camel:camelContext>
185
T U T O R IAL S
Camel does not require Spring
Camel does not require Spring, we could easily have used Camel
without Spring, but most users prefer to use Spring also.
</beans>
Store a file backup
We want to store the web service request as a file before we return a
response. To do this we want to send the file content as a message to an
endpoint that produces the file. So we need to do two steps:
▪ configure the file backup endpoint
▪ send the message to the endpoint
The endpoint is configured in spring XML so we just add it as:
<camel:camelContext id="camelContext">
<!-- endpoint named backup that is configued as a file component -->
<camel:endpoint id="backup" uri="file://target?append=false"/>
</camel:camelContext>
In the CamelContext we have defined our endpoint with the id backup and
configured it use the URL notation that we know from the internet. Its a file
scheme that accepts a context and some options. The contest is target and
its the folder to store the file. The option is just as the internet with ? and &
for subsequent options. We configure it to not append, meaning than any
existing file will be overwritten. See the File component for options and how
to use the camel file endpoint.
Next up is to be able to send a message to this endpoint. The easiest way
is to use a ProducerTemplate. A ProducerTemplate is inspired by Spring
template pattern with for instance JmsTemplate or JdbcTemplate in mind. The
template that all the grunt work and exposes a simple interface to the enduser where he/she can set the payload to send. Then the template will do
proper resource handling and all related issues in that regard. But how do we
get hold of such a template? Well the CamelContext is able to provide one.
This is done by configuring the template on the camel context in the spring
XML as:
T U T O R IA L S
186
<camel:camelContext id="camelContext">
<!-- producer template exposed with this id -->
<camel:template id="camelTemplate"/>
<!-- endpoint named backup that is configued as a file component -->
<camel:endpoint id="backup" uri="file://target?append=false"/>
</camel:camelContext>
Then we can expose a ProducerTemplate property on our service with a
setter in the Java code as:
public class ReportIncidentService {
private ProducerTemplate template;
public void setTemplate(ProducerTemplate template) {
this.template = template;
}
And then let Spring handle the dependency inject as below:
<bean id="incidentservice"
class="org.apache.camel.example.axis.ReportIncidentService">
<!-- set the producer template to use from the camel context below -->
<property name="template" ref="camelTemplate"/>
</bean>
Now we are ready to use the producer template in our service to send the
payload to the endpoint. The template has many sendXXX methods for this
purpose. But before we send the payload to the file endpoint we must also
specify what filename to store the file as. This is done by sending meta data
with the payload. In Camel metadata is sent as headers. Headers is just a
plain Map<String, Object>. So if we needed to send several metadata then
we could construct an ordinary HashMap and put the values in there. But as
we just need to send one header with the filename Camel has a convenient
send method sendBodyAndHeader so we choose this one.
public OutputReportIncident reportIncident(InputReportIncident parameters) {
System.out.println("Hello ReportIncidentService is called from " +
parameters.getGivenName());
String data = parameters.getDetails();
// store the data as a file
String filename = parameters.getIncidentId() + ".txt";
// send the data to the endpoint and the header contains what filename it
should be stored as
187
T U T O R IAL S
template.sendBodyAndHeader("backup", data, "org.apache.camel.file.name",
filename);
OutputReportIncident out = new OutputReportIncident();
out.setCode("OK");
return out;
}
The template in the code above uses 4 parameters:
▪ the endpoint name, in this case the id referring to the endpoint
defined in Spring XML in the camelContext element.
▪ the payload, can be any kind of object
▪ the key for the header, in this case a Camel keyword to set the
filename
▪ and the value for the header
Running the example
We start our integration with maven using mvn jetty:run. Then we open a
browser and hit http://localhost:8080. Jetty is so smart that it display a
frontpage with links to the deployed application so just hit the link and you
get our application. Now we hit append /services to the URL to access the
Axis frontpage. The URL should be http://localhost:8080/camelexample-axis/services.
You can then test it using a web service test tools such as SoapUI.
Hitting the service will output to the console
2008-09-06 15:01:41.718::INFO: Started SelectChannelConnector @ 0.0.0.0:8080
[INFO] Started Jetty Server
Hello ReportIncidentService is called from Ibsen
And there should be a file in the target subfolder.
dir target /b
123.txt
Unit Testing
We would like to be able to unit test our ReportIncidentService class. So
we add junit to the maven dependency:
<dependency>
<groupId>junit</groupId>
T U T O R IA L S
188
<artifactId>junit</artifactId>
<version>3.8.2</version>
<scope>test</scope>
</dependency>
And then we create a plain junit testcase for our service class.
package org.apache.camel.example.axis;
import junit.framework.TestCase;
import org.apache.camel.example.reportincident.InputReportIncident;
import org.apache.camel.example.reportincident.OutputReportIncident;
/**
* Unit test of service
*/
public class ReportIncidentServiceTest extends TestCase {
public void testIncident() {
ReportIncidentService service = new ReportIncidentService();
InputReportIncident input = createDummyIncident();
OutputReportIncident output = service.reportIncident(input);
assertEquals("OK", output.getCode());
}
protected InputReportIncident createDummyIncident() {
InputReportIncident input = new InputReportIncident();
input.setEmail("davsclaus@apache.org");
input.setIncidentId("12345678");
input.setIncidentDate("2008-07-13");
input.setPhone("+45 2962 7576");
input.setSummary("Failed operation");
input.setDetails("The wrong foot was operated.");
input.setFamilyName("Ibsen");
input.setGivenName("Claus");
return input;
}
}
Then we can run the test with maven using: mvn test. But we will get a
failure:
Running org.apache.camel.example.axis.ReportIncidentServiceTest
Hello ReportIncidentService is called from Claus
Tests run: 1, Failures: 0, Errors: 1, Skipped: 0, Time elapsed: 0.235 sec <<< FAILURE!
Results :
Tests in error:
189
T U T O R IAL S
testIncident(org.apache.camel.example.axis.ReportIncidentServiceTest)
Tests run: 1, Failures: 0, Errors: 1, Skipped: 0
What is the problem? Well our service uses a CamelProducer (the template)
to send a message to the file endpoint so the message will be stored in a file.
What we need is to get hold of such a producer and inject it on our service,
by calling the setter.
Since Camel is very light weight and embedable we are able to create a
CamelContext and add the endpoint in our unit test code directly. We do this
to show how this is possible:
private CamelContext context;
@Override
protected void setUp() throws Exception {
super.setUp();
// CamelContext is just created like this
context = new DefaultCamelContext();
// then we can create our endpoint and set the options
FileEndpoint endpoint = new FileEndpoint();
// the endpoint must have the camel context set also
endpoint.setCamelContext(context);
// our output folder
endpoint.setFile(new File("target"));
// and the option not to append
endpoint.setAppend(false);
// then we add the endpoint just in java code just as the spring XML, we
register it with the "backup" id.
context.addSingletonEndpoint("backup", endpoint);
// finally we need to start the context so Camel is ready to rock
context.start();
}
@Override
protected void tearDown() throws Exception {
super.tearDown();
// and we are nice boys so we stop it to allow resources to clean up
context.stop();
}
So now we are ready to set the ProducerTemplate on our service, and we get
a hold of that baby from the CamelContext as:
public void testIncident() {
ReportIncidentService service = new ReportIncidentService();
T U T O R IA L S
190
// get a producer template from the camel context
ProducerTemplate template = context.createProducerTemplate();
// inject it on our service using the setter
service.setTemplate(template);
InputReportIncident input = createDummyIncident();
OutputReportIncident output = service.reportIncident(input);
assertEquals("OK", output.getCode());
}
And this time when we run the unit test its a success:
Results :
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0
We would like to test that the file exists so we add these two lines to our test
method:
// should generate a file also
File file = new File("target/" + input.getIncidentId() + ".txt");
assertTrue("File should exists", file.exists());
Smarter Unit Testing with Spring
The unit test above requires us to assemble the Camel pieces manually in
java code. What if we would like our unit test to use our spring configuration
file axis-example-context.xml where we already have setup the endpoint.
And of course we would like to test using this configuration file as this is the
real file we will use. Well hey presto the xml file is a spring
ApplicationContext file and spring is able to load it, so we go the spring path
for unit testing. First we add the spring-test jar to our maven dependency:
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-test</artifactId>
<scope>test</scope>
</dependency>
And then we refactor our unit test to be a standard spring unit class. What
we need to do is to extend AbstractJUnit38SpringContextTests instead of
TestCase in our unit test. Since Spring 2.5 embraces annotations we will use
one as well to instruct what our xml configuration file is located:
191
T U T O R IAL S
@ContextConfiguration(locations = "classpath:axis-example-context.xml")
public class ReportIncidentServiceTest extends AbstractJUnit38SpringContextTests {
What we must remember to add is the classpath: prefix as our xml file is
located in src/main/resources. If we omit the prefix then Spring will by
default try to locate the xml file in the current package and that is
org.apache.camel.example.axis. If the xml file is located outside the
classpath you can use file: prefix instead. So with these two modifications we
can get rid of all the setup and teardown code we had before and now we will
test our real configuration.
The last change is to get hold of the producer template and now we can
just refer to the bean id it has in the spring xml file:
<!-- producer template exposed with this id -->
<camel:template id="camelTemplate"/>
So we get hold of it by just getting it from the spring ApplicationContext as
all spring users is used to do:
// get a producer template from the the spring context
ProducerTemplate template = (ProducerTemplate)
applicationContext.getBean("camelTemplate");
// inject it on our service using the setter
service.setTemplate(template);
Now our unit test is much better, and a real power of Camel is that is fits
nicely with Spring and you can use standard Spring'ish unit test to test your
Camel applications as well.
Unit Test calling WebService
What if you would like to execute a unit test where you send a webservice
request to the AxisReportIncidentService how do we unit test this one?
Well first of all the code is merely just a delegate to our real service that we
have just tested, but nevertheless its a good question and we would like to
know how. Well the answer is that we can exploit that fact that Jetty is also a
slim web container that can be embedded anywhere just as Camel can. So
we add this to our pom.xml:
<dependency>
<groupId>org.mortbay.jetty</groupId>
<artifactId>jetty</artifactId>
<version>${jetty-version}</version>
T U T O R IA L S
192
<scope>test</scope>
</dependency>
Then we can create a new class AxisReportIncidentServiceTest to unit
test with Jetty. The code to setup Jetty is shown below with code comments:
public class AxisReportIncidentServiceTest extends TestCase {
private Server server;
private void startJetty() throws Exception {
// create an embedded Jetty server
server = new Server();
// add a listener on port 8080 on localhost (127.0.0.1)
Connector connector = new SelectChannelConnector();
connector.setPort(8080);
connector.setHost("127.0.0.1");
server.addConnector(connector);
// add our web context path
WebAppContext wac = new WebAppContext();
wac.setContextPath("/unittest");
// set the location of the exploded webapp where WEB-INF is located
// this is a nice feature of Jetty where we can point to src/main/webapp
wac.setWar("./src/main/webapp");
server.setHandler(wac);
// then start Jetty
server.setStopAtShutdown(true);
server.start();
}
@Override
protected void setUp() throws Exception {
super.setUp();
startJetty();
}
@Override
protected void tearDown() throws Exception {
super.tearDown();
server.stop();
}
}
Now we just need to send the incident as a webservice request using Axis. So
we add the following code:
193
T U T O R IAL S
public void testReportIncidentWithAxis() throws Exception {
// the url to the axis webservice exposed by jetty
URL url = new URL("http://localhost:8080/unittest/services/
ReportIncidentPort");
// Axis stuff to get the port where we can send the webservice request
ReportIncidentService_ServiceLocator locator = new
ReportIncidentService_ServiceLocator();
ReportIncidentService_PortType port = locator.getReportIncidentPort(url);
// create input to send
InputReportIncident input = createDummyIncident();
// send the webservice and get the response
OutputReportIncident output = port.reportIncident(input);
assertEquals("OK", output.getCode());
// should generate a file also
File file = new File("target/" + input.getIncidentId() + ".txt");
assertTrue("File should exists", file.exists());
}
protected InputReportIncident createDummyIncident() {
InputReportIncident input = new InputReportIncident();
input.setEmail("davsclaus@apache.org");
input.setIncidentId("12345678");
input.setIncidentDate("2008-07-13");
input.setPhone("+45 2962 7576");
input.setSummary("Failed operation");
input.setDetails("The wrong foot was operated.");
input.setFamilyName("Ibsen");
input.setGivenName("Claus");
return input;
}
And now we have an unittest that sends a webservice request using good old
Axis.
Annotations
Both Camel and Spring has annotations that can be used to configure and
wire trivial settings more elegantly. Camel has the endpoint annotation
@EndpointInjected that is just what we need. With this annotation we can
inject the endpoint into our service. The annotation takes either a name or
uri parameter. The name is the bean id in the Registry. The uri is the URI
configuration for the endpoint. Using this you can actually inject an endpoint
that you have not defined in the camel context. As we have defined our
endpoint with the id backup we use the name parameter.
T U T O R IA L S
194
@EndpointInject(name = "backup")
private ProducerTemplate template;
Camel is smart as @EndpointInjected supports different kinds of object
types. We like the ProducerTemplate so we just keep it as it is.
Since we use annotations on the field directly we do not need to set the
property in the spring xml file so we change our service bean:
<bean id="incidentservice"
class="org.apache.camel.example.axis.ReportIncidentService"/>
Running the unit test with mvn test reveals that it works nicely.
And since we use the @EndpointInjected that refers to the endpoint with
the id backup directly we can loose the template tag in the xml, so its
shorter:
<bean id="incidentservice"
class="org.apache.camel.example.axis.ReportIncidentService"/>
<camel:camelContext id="camelContext">
<!-- producer template exposed with this id -->
<camel:template id="camelTemplate"/>
<!-- endpoint named backup that is configued as a file component -->
<camel:endpoint id="backup" uri="file://target?append=false"/>
</camel:camelContext>
And the final touch we can do is that since the endpoint is injected with
concrete endpoint to use we can remove the "backup" name parameter
when we send the message. So we change from:
// send the data to the endpoint and the header contains what filename it
should be stored as
template.sendBodyAndHeader("backup", data, "org.apache.camel.file.name",
filename);
To without the name:
// send the data to the endpoint and the header contains what filename it
should be stored as
template.sendBodyAndHeader(data, "org.apache.camel.file.name", filename);
Then we avoid to duplicate the name and if we rename the endpoint name
then we don't forget to change it in the code also.
195
T U T O R IAL S
The End
This tutorial hasn't really touched the one of the key concept of Camel as a
powerful routing and mediation framework. But we wanted to demonstrate
its flexibility and that it integrates well with even older frameworks such as
Apache Axis 1.4.
Check out the other tutorials on Camel and the other examples.
Note that the code shown here also applies to Camel 1.4 so actually you
can get started right away with the released version of Camel. As this time of
writing Camel 1.5 is work in progress.
See Also
▪ Tutorials
▪ Examples
TUTORIAL ON USING CAMEL IN A WEB APPLICATION
Camel has been designed to work great with the Spring framework; so if you
are already a Spring user you can think of Camel as just a framework for
adding to your Spring XML files.
So you can follow the usual Spring approach to working with web
applications; namely to add the standard Spring hook to load a /WEB-INF/
applicationContext.xml file. In that file you can include your usual Camel
XML configuration.
Step1: Edit your web.xml
To enable spring add a context loader listener to your /WEB-INF/web.xml
file
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/
xml/ns/javaee/web-app_2_5.xsd"
version="2.5">
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
</web-app>
T U T O R IA L S
196
This will cause Spring to boot up and look for the /WEB-INF/
applicationContext.xml file.
Step 2: Create a /WEB-INF/applicationContext.xml file
Now you just need to create your Spring XML file and add your camel routes
or configuration.
For example
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-2.5.xsd
http://camel.apache.org/schema/spring
http://camel.apache.org/schema/spring/camel-spring.xsd">
<camelContext xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="seda:foo"/>
<to uri="mock:results"/>
</route>
</camelContext>
</beans>
Then boot up your web application and you're good to go!
Hints and Tips
If you use Maven to build your application your directory tree will look like
this...
src/main/webapp/WEB-INF
web.xml
applicationContext.xml
To enable more rapid development we hightly recommend the jetty:run
maven plugin.
Please refer to the help for more information on using jetty:run - but briefly
if you add the following to your pom.xml
197
T U T O R IAL S
<build>
<plugins>
<plugin>
<groupId>org.mortbay.jetty</groupId>
<artifactId>maven-jetty-plugin</artifactId>
<configuration>
<webAppConfig>
<contextPath>/</contextPath>
</webAppConfig>
<scanIntervalSeconds>10</scanIntervalSeconds>
</configuration>
</plugin>
</plugins>
</build>
Then you can run your web application as follows
mvn jetty:run
Then Jetty will also monitor your target/classes directory and your src/main/
webapp directory so that if you modify your spring XML, your web.xml or
your java code the web application will be restarted, re-creating your Camel
routes.
If your unit tests take a while to run, you could miss them out when
running your web application via
mvn -Dtest=false jetty:run
TUTORIAL BUSINESS PARTNERS
BACKGROUND AND INTRODUCTION
Business Background
So there's a company, which we'll call Acme. Acme sells widgets, in a fairly
unusual way. Their customers are responsible for telling Acme what they
purchased. The customer enters into their own systems (ERP or whatever)
which widgets they bought from Acme. Then at some point, their systems
emit a record of the sale which needs to go to Acme so Acme can bill them
for it. Obviously, everyone wants this to be as automated as possible, so
there needs to be integration between the customer's system and Acme.
T U T O R IA L S
198
Under Construction
This tutorial is a work in progress.
Sadly, Acme's sales people are, technically speaking, doormats. They tell
all their prospects, "you can send us the data in whatever format, using
whatever protocols, whatever. You just can't change once it's up and
running."
The result is pretty much what you'd expect. Taking a random sample of 3
customers:
• Customer 1: XML over FTP
• Customer 2: CSV over HTTP
• Customer 3: Excel via e-mail
Now on the Acme side, all this has to be converted to a canonical XML format
and submitted to the Acme accounting system via JMS. Then the Acme
accounting system does its stuff and sends an XML reply via JMS, with a
summary of what it processed (e.g. 3 line items accepted, line item #2 in
error, total invoice $123.45). Finally, that data needs to be formatted into an
e-mail, and sent to a contact at the customer in question ("Dear Joyce, we
received an invoice on 1/2/08. We accepted 3 line items totaling $123.45,
though there was an error with line items #2 [invalid quantity ordered].
Thank you for your business. Love, Acme.").
So it turns out Camel can handle all this:
• Listen for HTTP, e-mail, and FTP files
• Grab attachments from the e-mail messages
• Convert XML, XLS, and CSV files to a canonical XML format
• read and write JMS messages
• route based on company ID
• format e-mails using Velocity templates
• send outgoing e-mail messages
Tutorial Background
This tutorial will cover all that, plus setting up tests along the way.
Before starting, you should be familiar with:
• Camel concepts including the CamelContext, Routes, Components
and Endpoints, and Enterprise Integration Patterns
• Configuring Camel with the XML or Java DSL
You'll learn:
• How to set up a Maven build for a Camel project
• How to transform XML, CSV, and Excel data into a standard XML
format with Camel
199
T U T O R IAL S
◦ How to write POJOs (Plain Old Java Objects), Velocity
templates, and XSLT stylesheets that are invoked by Camel
routes for message transformation
• How to configure simple and complex Routes in Camel, using either
the XML or the Java DSL format
• How to set up unit tests that load a Camel configuration and test
Camel routes
• How to use Camel's Data Formats to automatically convert data
between Java objects and XML, CSV files, etc.
• How to send and receive e-mail from Camel
• How to send and receive JMS messages from Camel
• How to use Enterprise Integration Patterns including Message Router
and Pipes and Filters
◦ How to use various languages to express content-based
routing rules in Camel
• How to deal with Camel messages, headers, and attachments
You may choose to treat this as a hands-on tutorial, and work through
building the code and configuration files yourself. Each of the sections gives
detailed descriptions of the steps that need to be taken to get the
components and routes working in Camel, and takes you through tests to
make sure they are working as expected.
But each section also links to working copies of the source and
configuration files, so if you don't want the hands-on approach, you can
simply review and/or download the finished files.
High-Level Diagram
Here's more or less what the integration process looks like.
First, the input from the customers to Acme:
And then, the output from Acme to the customers:
T U T O R IA L S
200
Tutorial Tasks
To get through this scenario, we're going to break it down into smaller pieces,
implement and test those, and then try to assemble the big scenario and test
that.
Here's what we'll try to accomplish:
1. Create a Maven build for the project
2. Get sample files for the customer Excel, CSV, and XML input
3. Get a sample file for the canonical XML format that Acme's
accounting system uses
4. Create an XSD for the canonical XML format
5. Create JAXB POJOs corresponding to the canonical XSD
6. Create an XSLT stylesheet to convert the Customer 1 (XML over FTP)
messages to the canonical format
7. Create a unit test to ensure that a simple Camel route invoking the
XSLT stylesheet works
8. Create a POJO that converts a List<List<String>> to the above
JAXB POJOs
◦ Note that Camel can automatically convert CSV input to a
List of Lists of Strings representing the rows and columns of
the CSV, so we'll use this POJO to handle Customer 2 (CSV
over HTTP)
9. Create a unit test to ensure that a simple Camel route invoking the
CSV processing works
10. Create a POJO that converts a Customer 3 Excel file to the above
JAXB POJOs (using POI to read Excel)
11. Create a unit test to ensure that a simple Camel route invoking the
Excel processing works
12. Create a POJO that reads an input message, takes an attachment off
the message, and replaces the body of the message with the
attachment
201
T U T O R IAL S
◦ This is assuming for Customer 3 (Excel over e-mail) that the
e-mail contains a single Excel file as an attachment, and the
actual e-mail body is throwaway
13. Build a set of Camel routes to handle the entire input (Customer ->
Acme) side of the scenario.
14. Build unit tests for the Camel input.
15. TODO: Tasks for the output (Acme -> Customer) side of the scenario
LET'S GET STARTED!
Step 1: Initial Maven build
We'll use Maven for this project as there will eventually be quite a few
dependencies and it's nice to have Maven handle them for us. You should
have a current version of Maven (e.g. 2.0.9) installed.
You can start with a pretty empty project directory and a Maven POM file,
or use a simple JAR archetype to create one.
Here's a sample POM. We've added a dependency on camel-core, and set
the compile version to 1.5 (so we can use annotations):
Listing 17. pom.xml
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0">
<modelVersion>4.0.0</modelVersion>
<groupId>org.apache.camel.tutorial</groupId>
<artifactId>business-partners</artifactId>
<version>1.0-SNAPSHOT</version>
<name>Camel Business Partners Tutorial</name>
<dependencies>
<dependency>
<artifactId>camel-core</artifactId>
<groupId>org.apache.camel</groupId>
<version>1.4.0</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<source>1.5</source>
<target>1.5</target>
</configuration>
</plugin>
</plugins>
T U T O R IA L S
202
</build>
</project>
Step 2: Get Sample Files
You can make up your own if you like, but here are the "off the shelf" ones.
You can save yourself some time by downloading these to src/test/
resources in your Maven project.
• Customer 1 (XML): input-customer1.xml
• Customer 2 (CSV): input-customer2.csv
• Customer 3 (Excel): input-customer3.xls
• Canonical Acme XML Request: canonical-acme-request.xml
• Canonical Acme XML Response: TODO
If you look at these files, you'll see that the different input formats use
different field names and/or ordering, because of course the sales guys were
totally OK with that. Sigh.
Step 3: XSD and JAXB Beans for the Canonical XML Format
Here's the sample of the canonical XML file:
<?xml version="1.0" encoding="UTF-8"?>
<invoice xmlns="http://activemq.apache.org/camel/tutorial/partners/invoice">
<partner-id>2</partner-id>
<date-received>9/12/2008</date-received>
<line-item>
<product-id>134</product-id>
<description>A widget</description>
<quantity>3</quantity>
<item-price>10.45</item-price>
<order-date>6/5/2008</order-date>
</line-item>
<!-- // more line-item elements here -->
<order-total>218.82</order-total>
</invoice>
If you're ambitions, you can write your own XSD (XML Schema) for files that
look like this, and save it to src/main/xsd.
Solution: If not, you can download mine, and save that to save it to src/
main/xsd.
203
T U T O R IAL S
Generating JAXB Beans
Down the road we'll want to deal with the XML as Java POJOs. We'll take a
moment now to set up those XML binding POJOs. So we'll update the Maven
POM to generate JAXB beans from the XSD file.
We need a dependency:
<dependency>
<artifactId>camel-jaxb</artifactId>
<groupId>org.apache.camel</groupId>
<version>1.4.0</version>
</dependency>
And a plugin configured:
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>jaxb2-maven-plugin</artifactId>
<executions>
<execution>
<goals>
<goal>xjc</goal>
</goals>
</execution>
</executions>
</plugin>
That should do it (it automatically looks for XML Schemas in src/main/xsd to
generate beans for). Run mvn install and it should emit the beans into
target/generated-sources/jaxb. Your IDE should see them there, though
you may need to update the project to reflect the new settings in the Maven
POM.
Step 4: Initial Work on Customer 1 Input (XML over FTP)
To get a start on Customer 1, we'll create an XSLT template to convert the
Customer 1 sample file into the canonical XML format, write a small Camel
route to test it, and build that into a unit test. If we get through this, we can
be pretty sure that the XSLT template is valid and can be run safely in Camel.
Create an XSLT template
Start with the Customer 1 sample input. You want to create an XSLT template
to generate XML like the canonical XML sample above – an invoice
element with line-item elements (one per item in the original XML
T U T O R IA L S
204
document). If you're especially clever, you can populate the current date and
order total elements too.
Solution: My sample XSLT template isn't that smart, but it'll get you going
if you don't want to write one of your own.
Create a unit test
Here's where we get to some meaty Camel work. We need to:
• Set up a unit test
• That loads a Camel configuration
• That has a route invoking our XSLT
• Where the test sends a message to the route
• And ensures that some XML comes out the end of the route
The easiest way to do this is to set up a Spring context that defines the
Camel stuff, and then use a base unit test class from Spring that knows how
to load a Spring context to run tests against. So, the procedure is:
Set Up a Skeletal Camel/Spring Unit Test
1. Add dependencies on Camel-Spring, and the Spring test JAR (which
will automatically bring in JUnit 3.8.x) to your POM:
<dependency>
<artifactId>camel-spring</artifactId>
<groupId>org.apache.camel</groupId>
<version>1.4.0</version>
</dependency>
<dependency>
<artifactId>spring-test</artifactId>
<groupId>org.springframework</groupId>
<version>2.5.5</version>
<scope>test</scope>
</dependency>
2. Create a new unit test class in src/test/java/your-package-here,
perhaps called XMLInputTest.java
3. Make the test extend Spring's AbstractJUnit38SpringContextTests
class, so it can load a Spring context for the test
4. Create a Spring context configuration file in src/test/resources,
perhaps called XMLInputTest-context.xml
5. In the unit test class, use the class-level @ContextConfiguration
annotation to indicate that a Spring context should be loaded
◦ By default, this looks for a Context configuration file called
TestClassName-context.xml in a subdirectory
corresponding to the package of the test class. For instance,
205
T U T O R IAL S
if your test class was
org.apache.camel.tutorial.XMLInputTest, it would look
for org/apache/camel/tutorial/XMLInputTestcontext.xml
◦ To override this default, use the locations attribute on the
@ContextConfiguration annotation to provide specific context
file locations (starting each path with a / if you don't want it
to be relative to the package directory). My solution does this
so I can put the context file directly in src/test/resources
instead of in a package directory under there.
6. Add a CamelContext instance variable to the test class, with the
@Autowired annotation. That way Spring will automatically pull the
CamelContext out of the Spring context and inject it into our test
class.
7. Add a ProducerTemplate instance variable and a setUp method that
instantiates it from the CamelContext. We'll use the
ProducerTemplate later to send messages to the route.
protected ProducerTemplate<Exchange> template;
protected void setUp() throws Exception {
super.setUp();
template = camelContext.createProducerTemplate();
}
8. Put in an empty test method just for the moment (so when we run
this we can see that "1 test succeeded")
9. Add the Spring <beans> element (including the Camel Namespace)
with an empty <camelContext> element to the Spring context, like
this:
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/
spring-beans-2.5.xsd
http://activemq.apache.org/camel/schema/spring
http://activemq.apache.org/camel/schema/
spring/camel-spring-1.4.0.xsd">
<camelContext id="camel" xmlns="http://activemq.apache.org/camel/schema/
spring">
</camelContext>
</beans>
T U T O R IA L S
206
Test it by running mvn install and make sure there are no build errors. So far
it doesn't test much; just that your project and test and source files are all
organized correctly, and the one empty test method completes successfully.
Solution: Your test class might look something like this:
• src/test/java/org/apache/camel/tutorial/XMLInputTest.java
• src/test/resources/XMLInputTest-context.xml (same as just above)
Flesh Out the Unit Test
So now
sample
out:
1.
2.
we're going to write a Camel route that applies the XSLT to the
Customer 1 input file, and makes sure that some XML output comes
Save the input-customer1.xml file to src/test/resources
Save your XSLT file (created in the previous step) to src/main/
resources
3. Write a Camel Route, either right in the Spring XML, or using the Java
DSL (in another class under src/test/java somewhere). This route
should use the Pipes and Filters integration pattern to:
1. Start from the endpoint direct:start (which lets the test
conveniently pass messages into the route)
2. Call the endpoint xslt:YourXSLTFile.xsl (to transform the
message with the specified XSLT template)
3. Send the result to the endpoint mock:finish (which lets the
test verify the route output)
4. Add a test method to the unit test class that:
1. Get a reference to the Mock endpoint mock:finish using
code like this:
MockEndpoint finish = MockEndpoint.resolve(camelContext,
"mock:finish");
2. Set the expectedMessageCount on that endpoint to 1
3. Get a reference to the Customer 1 input file, using code like
this:
InputStream in =
XMLInputTest.class.getResourceAsStream("/input-partner1.xml");
assertNotNull(in);
4. Send that InputStream as a message to the direct:start
endpoint, using code like this:
template.sendBody("direct:start", in);
207
T U T O R IAL S
Note that we can send the sample file body in several
formats (File, InputStream, String, etc.) but in this case an
InputStream is pretty convenient.
5. Ensure that the message made it through the route to the
final endpoint, by testing all configured Mock endpoints like
this:
MockEndpoint.assertIsSatisfied(camelContext);
6. If you like, inspect the final message body using some code
like finish.getExchanges().get(0).getIn().getBody().
▪ If you do this, you'll need to know what format that
body is – String, byte array, InputStream, etc.
5. Run your test with mvn install and make sure the build completes
successfully.
Solution: Your finished test might look something like this:
• src/test/java/org/apache/camel/tutorial/XMLInputTest.java
• For XML Configuration:
◦ src/test/resources/XMLInputTest-context.xml
• Or, for Java DSL Configuration:
◦ src/test/resources/XMLInputTest-dsl-context.xml
◦ src/test/java/org/apache/camel/tutorial/
routes/XMLInputTestRoute.java
Step 5: Initial Work on Customer 2 Input (CSV over HTTP)
To get a start on Customer 2, we'll create a POJO to convert the Customer 2
sample CSV data into the JAXB POJOs representing the canonical XML format,
write a small Camel route to test it, and build that into a unit test. If we get
through this, we can be pretty sure that the CSV conversion and JAXB
handling is valid and can be run safely in Camel.
Create a CSV-handling POJO
To begin with, CSV is a known data format in Camel. Camel can convert a
CSV file to a List (representing rows in the CSV) of Lists (representing cells in
the row) of Strings (the data for each cell). That means our POJO can just
assume the data coming in is of type List<List<String>>, and we can
declare a method with that as the argument.
Looking at the JAXB code in target/generated-sources/jaxb, it looks
like an Invoice object represents the whole document, with a nested list of
LineItemType objects for the line items. Therefore our POJO method will
return an Invoice (a document in the canonical XML format).
T U T O R IA L S
208
Test Base Class
Once your test class is working, you might want to extract things
like the @Autowired CamelContext, the ProducerTemplate, and the
setUp method to a custom base class that you extend with your
other tests.
So to implement the CSV-to-JAXB POJO, we need to do something like this:
1. Create a new class under src/main/java, perhaps called
CSVConverterBean.
2. Add a method, with one argument of type List<List<String>> and
the return type Invoice
◦ You may annotate the argument with @Body to specifically
designate it as the body of the incoming message
3. In the method, the logic should look roughly like this:
1. Create a new Invoice, using the method on the generated
ObjectFactory class
2. Loop through all the rows in the incoming CSV (the outer
List)
3. Skip the first row, which contains headers (column names)
4. For the other rows:
1. Create a new LineItemType (using the
ObjectFactory again)
2. Pick out all the cell values (the Strings in the inner
List) and put them into the correct fields of the
LineItemType
▪ Not all of the values will actually go into the
line item in this example
▪ You may hardcode the column ordering based
on the sample data file, or else try to read it
dynamically from the headers in the first line
▪ Note that you'll need to use a JAXB
DatatypeFactory to create the
XMLGregorianCalendar values that JAXB
uses for the date fields in the XML – which
probably means using a SimpleDateFormat
to parse the date and setting that date on a
GregorianCalendar
3. Add the line item to the invoice
5. Populate the partner ID, date of receipt, and order total on
the Invoice
209
T U T O R IAL S
6. Throw any exceptions out of the method, so Camel knows
something went wrong
7. Return the finished Invoice
Solution: Here's an example of what the CSVConverterBean might look like.
Create a unit test
Start with a simple test class and test Spring context like last time, perhaps
based on the name CSVInputTest:
Listing 18. CSVInputTest.java
/**
* A test class the ensure we can convert Partner 2 CSV input files to the
* canonical XML output format, using JAXB POJOs.
*/
@ContextConfiguration(locations = "/CSVInputTest-context.xml")
public class CSVInputTest extends AbstractJUnit38SpringContextTests {
@Autowired
protected CamelContext camelContext;
protected ProducerTemplate<Exchange> template;
protected void setUp() throws Exception {
super.setUp();
template = camelContext.createProducerTemplate();
}
public void testCSVConversion() {
// TODO
}
}
Listing 19. CSVInputTest-context.xml
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/
spring-beans-2.5.xsd
http://activemq.apache.org/camel/schema/spring
http://activemq.apache.org/camel/schema/spring/
camel-spring-1.4.0.xsd">
<camelContext id="camel" xmlns="http://activemq.apache.org/camel/schema/spring">
<!-- TODO -->
</camelContext>
</beans>
Now the meaty part is to flesh out the test class and write the Camel routes.
1. Update the Maven POM to include CSV Data Format support:
T U T O R IA L S
210
<dependency>
<artifactId>camel-csv</artifactId>
<groupId>org.apache.camel</groupId>
<version>1.4.0</version>
</dependency>
2. Write the routes (right in the Spring XML context, or using the Java
DSL) for the CSV conversion process, again using the Pipes and
Filters pattern:
1. Start from the endpoint direct:CSVstart (which lets the test
conveniently pass messages into the route). We'll name this
differently than the starting point for the previous test, in
case you use the Java DSL and put all your routes in the
same package (which would mean that each test would load
the DSL routes for several tests.)
2. This time, there's a little preparation to be done. Camel
doesn't know that the initial input is a CSV, so it won't be
able to convert it to the expected List<List<String>>
without a little hint. For that, we need an unmarshal
transformation in the route. The unmarshal method (in the
DSL) or element (in the XML) takes a child indicating the
format to unmarshal; in this case that should be csv.
3. Next invoke the POJO to transform the message with a
bean:CSVConverter endpoint
4. As before, send the result to the endpoint mock:finish (which
lets the test verify the route output)
5. Finally, we need a Spring <bean> element in the Spring
context XML file (but outside the <camelContext> element)
to define the Spring bean that our route invokes. This Spring
bean should have a name attribute that matches the name
used in the bean endpoint (CSVConverter in the example
above), and a class attribute that points to the CSV-to-JAXB
POJO class you wrote above (such as,
org.apache.camel.tutorial.CSVConverterBean). When
Spring is in the picture, any bean endpoints look up Spring
beans with the specified name.
3. Write a test method in the test class, which should look very similar
to the previous test class:
1. Get the MockEndpoint for the final endpoint, and tell it to
expect one message
2. Load the Partner 2 sample CSV file from the ClassPath, and
send it as the body of a message to the starting endpoint
211
T U T O R IAL S
3. Verify that the final MockEndpoint is satisfied (that is, it
received one message) and examine the message body if
you like
▪ Note that we didn't marshal the JAXB POJOs to XML in
this test, so the final message should contain an
Invoice as the body. You could write a simple line of
code to get the Exchange (and Message) from the
MockEndpoint to confirm that.
4. Run this new test with mvn install and make sure it passes and the
build completes successfully.
Solution: Your finished test might look something like this:
• src/test/java/org/apache/camel/tutorial/CSVInputTest.java
• For XML Configuration:
◦ src/test/resources/CSVInputTest-context.xml
• Or, for Java DSL Configuration:
◦ src/test/resources/CSVInputTest-dsl-context.xml
◦ src/test/java/org/apache/camel/tutorial/
routes/CSVInputTestRoute.java
Step 6: Initial Work on Customer 3 Input (Excel over e-mail)
To get a start on Customer 3, we'll create a POJO to convert the Customer 3
sample Excel data into the JAXB POJOs representing the canonical XML
format, write a small Camel route to test it, and build that into a unit test. If
we get through this, we can be pretty sure that the Excel conversion and
JAXB handling is valid and can be run safely in Camel.
Create an Excel-handling POJO
Camel does not have a data format handler for Excel by default. We have two
options – create an Excel DataFormat (so Camel can convert Excel
spreadsheets to something like the CSV List<List<String>> automatically),
or create a POJO that can translate Excel data manually. For now, the second
approach is easier (if we go the DataFormat route, we need code to both
read and write Excel files, whereas otherwise read-only will do).
So, we need a POJO with a method that takes something like an
InputStream or byte[] as an argument, and returns in Invoice as before.
The process should look something like this:
1. Update the Maven POM to include POI support:
<dependency>
<artifactId>poi</artifactId>
T U T O R IA L S
212
<groupId>org.apache.poi</groupId>
<version>3.1-FINAL</version>
</dependency>
2. Create a new class under src/main/java, perhaps called
ExcelConverterBean.
3. Add a method, with one argument of type InputStream and the
return type Invoice
◦ You may annotate the argument with @Body to specifically
designate it as the body of the incoming message
4. In the method, the logic should look roughly like this:
1. Create a new Invoice, using the method on the generated
ObjectFactory class
2. Create a new HSSFWorkbook from the InputStream, and get
the first sheet from it
3. Loop through all the rows in the sheet
4. Skip the first row, which contains headers (column names)
5. For the other rows:
1. Create a new LineItemType (using the
ObjectFactory again)
2. Pick out all the cell values and put them into the
correct fields of the LineItemType (you'll need some
data type conversion logic)
▪ Not all of the values will actually go into the
line item in this example
▪ You may hardcode the column ordering based
on the sample data file, or else try to read it
dynamically from the headers in the first line
▪ Note that you'll need to use a JAXB
DatatypeFactory to create the
XMLGregorianCalendar values that JAXB
uses for the date fields in the XML – which
probably means setting the date from a date
cell on a GregorianCalendar
3. Add the line item to the invoice
6. Populate the partner ID, date of receipt, and order total on
the Invoice
7. Throw any exceptions out of the method, so Camel knows
something went wrong
8. Return the finished Invoice
Solution: Here's an example of what the ExcelConverterBean might look
like.
213
T U T O R IAL S
Create a unit test
The unit tests should be pretty familiar now. The test class and context for
the Excel bean should be quite similar to the CSV bean.
1. Create the basic test class and corresponding Spring Context XML
configuration file
2. The XML config should look a lot like the CSV test, except:
◦ Remember to use a different start endpoint name if you're
using the Java DSL and not use separate packages per test
◦ You don't need the unmarshal step since the Excel POJO
takes the raw InputStream from the source endpoint
◦ You'll declare a <bean> and endpoint for the Excel bean
prepared above instead of the CSV bean
3. The test class should look a lot like the CSV test, except use the right
input file name and start endpoint name.
Solution: Your finished test might look something like this:
• src/test/java/org/apache/camel/tutorial/ExcelInputTest.java
• For XML Configuration:
◦ src/test/resources/ExcelInputTest-context.xml
• Or, for Java DSL Configuration:
◦ src/test/resources/ExcelInputTest-dsl-context.xml
◦ src/test/java/org/apache/camel/tutorial/
routes/ExcelInputTestRoute.java
Step 7: Put this all together into Camel routes for the Customer
Input
With all the data type conversions working, the next step is to write the real
routes that listen for HTTP, FTP, or e-mail input, and write the final XML
output to an ActiveMQ queue. Along the way these routes will use the data
conversions we've developed above.
So we'll create 3 routes to start with, as shown in the diagram back at the
beginning:
1. Accept XML orders over FTP from Customer 1 (we'll assume the FTP
server dumps files in a local directory on the Camel machine)
2. Accept CSV orders over HTTP from Customer 2
3. Accept Excel orders via e-mail from Customer 3 (we'll assume the
messages are sent to an account we can access via IMAP)
...
Step 8: Create a unit test for the Customer Input Routes
T U T O R IA L S
214
Logging
You may notice that your tests emit a lot less output all of a sudden.
The dependency on POI brought in Log4J and configured commonslogging to use it, so now we need a log4j.properties file to configure
log output. You can use the attached one (snarfed from ActiveMQ)
or write your own; either way save it to src/main/resources to
ensure you continue to see log output.
215
T U T O R IAL S
Languages Supported
Appendix
To support flexible and powerful Enterprise Integration Patterns Camel
supports various Languages to create an Expression or Predicate within
either the Routing Domain Specific Language or the Xml Configuration. The
following languages are supported
BEAN LANGUAGE
The purpose of the Bean Language is to be able to implement an Expression
or Predicate using a simple method on a bean.
So the idea is you specify a bean name which will then be resolved in the
Registry such as the Spring ApplicationContext then a method is invoked to
evaluate the Expression or Predicate.
If no method name is provided then one is attempted to be chosen using
the rules for Bean Binding; using the type of the message body and using
any annotations on the bean methods.
The Bean Binding rules are used to bind the Message Exchange to the
method parameters; so you can annotate the bean to extract headers or
other expressions such as XPath or XQuery from the message.
Using Bean Expressions from the Java DSL
from("activemq:topic:OrdersTopic").
filter().method("myBean", "isGoldCustomer").
to("activemq:BigSpendersQueue");
Using Bean Expressions from XML
<route>
<from uri="activemq:topic:OrdersTopic"/>
<filter>
<method bean="myBean" method="isGoldCustomer"/>
<to uri="activemq:BigSpendersQueue"/>
</filter>
</route>
L AN G UA GE S S U PP O RTE D A PPE NDIX
216
Writing the expression bean
The bean in the above examples is just any old Java Bean with a method
called isGoldCustomer() that returns some object that is easily converted to a
boolean value in this case, as its used as a predicate.
So we could implement it like this...
public class MyBean {
public boolean isGoldCustomer(Exchange exchange) {
...
}
}
We can also use the Bean Integration annotations. For example you could
do...
public boolean isGoldCustomer(String body) {...}
or
public boolean isGoldCustomer(@Header(name = "foo") Integer fooHeader) {...}
So you can bind parameters of the method to the Exchange, the Message or
individual headers, properties, the body or other expressions.
Non registry beans
As of Camel 1.5 the Bean Language also supports invoking beans that isn't
registered in the Registry. This is usable for quickly to invoke a bean from
Java DSL where you don't need to register the bean in the Registry such as
the Spring ApplicationContext.
Camel can instantiate the bean and invoke the method if given a class or
invoke an already existing instance. This is illustrated from the example
below:
NOTE This bean DSL is supported since Camel 2.0-M2
from("activemq:topic:OrdersTopic").
filter().expression(BeanLanguage(MyBean.class, "isGoldCustomer")).
to("activemq:BigSpendersQueue");
The 2nd parameter isGoldCustomer is an optional parameter to explicit set
the method name to invoke. If not provided Camel will try to invoke the best
suited method. If case of ambiguity Camel will thrown an Exception. In these
situations the 2nd parameter can solve this problem. Also the code is more
217
L A N G UA G E S S U P P ORT E D A P P E N D I X
readable if the method name is provided. The 1st parameter can also be an
existing instance of a Bean such as:
private MyBean my;
from("activemq:topic:OrdersTopic").
filter().expression(BeanLanguage.bean(my, "isGoldCustomer")).
to("activemq:BigSpendersQueue");
In Camel 2.2 onwards you can avoid the BeanLanguage and have it just as:
private MyBean my;
from("activemq:topic:OrdersTopic").
filter().expression(bean(my, "isGoldCustomer")).
to("activemq:BigSpendersQueue");
Which also can be done in a bit shorter and nice way:
private MyBean my;
from("activemq:topic:OrdersTopic").
filter().method(my, "isGoldCustomer").
to("activemq:BigSpendersQueue");
Other examples
We have some test cases you can look at if it'll help
• MethodFilterTest is a JUnit test case showing the Java DSL use of the
bean expression being used in a filter
• aggregator.xml is a Spring XML test case for the Aggregator which
uses a bean method call to test for the completion of the
aggregation.
Dependencies
The Bean language is part of camel-core.
CONSTANT EXPRESSION LANGUAGE
The Constant Expression Language is really just a way to specify constant
strings as a type of expression.
Available as of Camel 1.5
L AN G UA GE S S U PP O RTE D A PPE NDIX
218
Example usage
The setHeader element of the Spring DSL can utilize a constant expression
like:
<route>
<from uri="seda:a"/>
<setHeader headerName="theHeader">
<constant>the value</constant>
</setHeader>
<to uri="mock:b"/>
</route>
in this case, the Message coming from the seda:a Endpoint will have
'theHeader' header set to the constant value 'the value'.
And the same example using Java DSL:
from("seda:a").setHeader("theHeader", constant("the value")).to("mock:b");
Dependencies
The Constant language is part of camel-core.
EL
Camel supports the unified JSP and JSF Expression Language via the JUEL to
allow an Expression or Predicate to be used in the DSL or Xml Configuration.
For example you could use EL inside a Message Filter in XML
<route>
<from uri="seda:foo"/>
<filter>
<el>${in.headers.foo == 'bar'}</el>
<to uri="seda:bar"/>
</filter>
</route>
You could also use slightly different syntax, e.g. if the header name is not a
valid identifier:
<route>
<from uri="seda:foo"/>
<filter>
<el>${in.headers['My Header'] == 'bar'}</el>
<to uri="seda:bar"/>
219
L A N G UA G E S S U P P ORT E D A P P E N D I X
</filter>
</route>
You could use EL to create an Predicate in a Message Filter or as an
Expression for a Recipient List
Variables
Variable
Type
Description
exchange
Exchange
the Exchange object
in
Message
the exchange.in message
out
Message
the exchange.out message
Samples
You can use EL dot notation to invoke operations. If you for instance have a
body that contains a POJO that has a getFamiliyName method then you can
construct the syntax as follows:
"$in.body.familyName"
Dependencies
To use EL in your camel routes you need to add the a dependency on cameljuel which implements the EL language.
If you use maven you could just add the following to your pom.xml,
substituting the version number for the latest & greatest release (see the
download page for the latest versions).
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-juel</artifactId>
<version>1.6.1</version>
</dependency>
Otherwise you'll also need to include JUEL.
L AN G UA GE S S U PP O RTE D A PPE NDIX
220
HEADER EXPRESSION LANGUAGE
The Header Expression Language allows you to extract values of named
headers.
Available as of Camel 1.5
Example usage
The recipientList element of the Spring DSL can utilize a header expression
like:
<route>
<from uri="direct:a" />
<!-- use comma as a delimiter for String based values -->
<recipientList delimiter=",">
<header>myHeader</header>
</recipientList>
</route>
In this case, the list of recipients are contained in the header 'myHeader'.
And the same example in Java DSL:
from("direct:a").recipientList(header("myHeader"));
And with a slightly different syntax where you use the builder to the fullest
(i.e. avoid using parameters but using stacked operations, notice that header
is not a parameter but a stacked method call)
from("direct:a").recipientList().header("myHeader");
Dependencies
The Header language is part of camel-core.
JXPATH
Camel supports JXPath to allow XPath expressions to be used on beans in an
Expression or Predicate to be used in the DSL or Xml Configuration. For
example you could use JXPath to create an Predicate in a Message Filter or as
an Expression for a Recipient List.
From 1.3 of Camel onwards you can use XPath expressions directly using
smart completion in your IDE as follows
221
L A N G UA G E S S U P P ORT E D A P P E N D I X
from("queue:foo").filter().
jxpath("/in/body/foo").
to("queue:bar")
Variables
Variable
Type
Description
this
Exchange
the Exchange object
in
Message
the exchange.in message
out
Message
the exchange.out message
Using XML configuration
If you prefer to configure your routes in your Spring XML file then you can
use JXPath expressions as follows
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/
schema/beans/spring-beans-2.0.xsd
http://camel.apache.org/schema/spring http://camel.apache.org/schema/spring/
camel-spring.xsd">
<camelContext id="camel" xmlns="http://activemq.apache.org/camel/schema/spring">
<route>
<from uri="activemq:MyQueue"/>
<filter>
<jxpath>in/body/name = 'James'</xpath>
<to uri="mqseries:SomeOtherQueue"/>
</filter>
</route>
</camelContext>
</beans>
Examples
Here is a simple example using a JXPath expression as a predicate in a
Message Filter
from("direct:start").
filter().jxpath("in/body/name='James'").
to("mock:result");
L AN G UA GE S S U PP O RTE D A PPE NDIX
222
JXPATH INJECTION
You can use Bean Integration to invoke a method on a bean and use various
languages such as JXPath to extract a value from the message and bind it to
a method parameter.
For example
public class Foo {
@MessageDriven(uri = "activemq:my.queue")
public void doSomething(@JXPath("in/body/foo") String correlationID, @Body String
body) {
// process the inbound message here
}
}
Dependencies
To use JXpath in your camel routes you need to add the a dependency on
camel-jxpath which implements the JXpath language.
If you use maven you could just add the following to your pom.xml,
substituting the version number for the latest & greatest release (see the
download page for the latest versions).
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-jxpath</artifactId>
<version>1.4.0</version>
</dependency>
Otherwise, you'll also need Commons JXPath.
MVEL
Avialable in Camel 2.0
Camel allows Mvel to be used as an Expression or Predicate the DSL or
Xml Configuration.
You could use Mvel to create an Predicate in a Message Filter or as an
Expression for a Recipient List
You can use Mvel dot notation to invoke operations. If you for instance
have a body that contains a POJO that has a getFamiliyName method then
you can construct the syntax as follows:
223
L A N G UA G E S S U P P ORT E D A P P E N D I X
"request.body.familyName"
// or
"getRequest().getBody().getFamilyName()"
Variables
Variable
Type
Description
this
Exchange
the Exchange is the root object
exchange
Exchange
the Exchange object
exception
Throwable
the Exchange exception (if any)
exchangeId
String
the exchange id
fault
Message
the Fault message (if any)
request
Message
the exchange.in message
response
Message
the exchange.out message (if any)
properties
Map
the exchange properties
property(name)
Object
the property by the given name
property(name,
type)
Type
the property by the given name as the
given type
Samples
For example you could use Mvel inside a Message Filter in XML
<route>
<from uri="seda:foo"/>
<filter>
<mvel>request.headers.foo == 'bar'</mvel>
<to uri="seda:bar"/>
</filter>
</route>
And the sample using Java DSL:
from("seda:foo").filter().mvel("request.headers.foo == 'bar'").to("seda:bar");
L AN G UA GE S S U PP O RTE D A PPE NDIX
224
Dependencies
To use Mvel in your camel routes you need to add the a dependency on
camel-mvel which implements the Mvel language.
If you use maven you could just add the following to your pom.xml,
substituting the version number for the latest & greatest release (see the
download page for the latest versions).
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-mvel</artifactId>
<version>2.0.0</version>
</dependency>
Otherwise, you'll also need MVEL
OGNL
Camel allows OGNL to be used as an Expression or Predicate the DSL or Xml
Configuration.
You could use OGNL to create an Predicate in a Message Filter or as an
Expression for a Recipient List
You can use OGNL dot notation to invoke operations. If you for instance
have a body that contains a POJO that has a getFamiliyName method then
you can construct the syntax as follows:
"request.body.familyName"
// or
"getRequest().getBody().getFamilyName()"
Variables
225
Variable
Type
Description
this
Exchange
the Exchange is the root object
exchange
Exchange
the Exchange object
exception
Throwable
the Exchange exception (if any)
exchangeId
String
the exchange id
fault
Message
the Fault message (if any)
request
Message
the exchange.in message
L A N G UA G E S S U P P ORT E D A P P E N D I X
response
Message
the exchange.out message (if any)
properties
Map
the exchange properties
property(name)
Object
the property by the given name
property(name,
type)
Type
the property by the given name as the
given type
Samples
For example you could use OGNL inside a Message Filter in XML
<route>
<from uri="seda:foo"/>
<filter>
<ognl>request.headers.foo == 'bar'</ognl>
<to uri="seda:bar"/>
</filter>
</route>
And the sample using Java DSL:
from("seda:foo").filter().ognl("request.headers.foo == 'bar'").to("seda:bar");
Dependencies
To use OGNL in your camel routes you need to add the a dependency on
camel-ognl which implements the OGNL language.
If you use maven you could just add the following to your pom.xml,
substituting the version number for the latest & greatest release (see the
download page for the latest versions).
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-ognl</artifactId>
<version>1.4.0</version>
</dependency>
Otherwise, you'll also need OGNL
PROPERTY EXPRESSION LANGUAGE
The Property Expression Language allows you to extract values of named
exchange properties.
L AN G UA GE S S U PP O RTE D A PPE NDIX
226
Available as of Camel 2.0
Example usage
The recipientList element of the Spring DSL can utilize a property expression
like:
<route>
<from uri="direct:a" />
<recipientList>
<property>myProperty</property>
</recipientList>
</route>
In this case, the list of recipients are contained in the property 'myProperty'.
And the same example in Java DSL:
from("direct:a").recipientList(property("myProperty"));
And with a slightly different syntax where you use the builder to the fullest
(i.e. avoid using parameters but using stacked operations, notice that
property is not a parameter but a stacked method call)
from("direct:a").recipientList().property("myProperty");
Dependencies
The Property language is part of camel-core.
SCRIPTING LANGUAGES
Camel supports a number of scripting languages which can be used to create
an Expression or Predicate via the standard JSR 223 which is a standard part
of Java 6.
The following scripting languages are integrated into the DSL:
227
Language
DSL keyword
EL
el
Groovy
groovy
JavaScript
javaScript
JoSQL
sql
L A N G UA G E S S U P P ORT E D A P P E N D I X
JXPath
jxpath
MVEL
mvel
OGNL
ognl
PHP
php
Python
python
Ruby
ruby
XPath
xpath
XQuery
xquery
However any JSR 223 scripting language can be used using the generic DSL
methods.
ScriptContext
The JSR-223 scripting languages ScriptContext is pre configured with the
following attributes all set at ENGINE_SCOPE:
Attribute
Type
Value
context
org.apache.camel.CamelContext
The Camel Context
exchange
org.apache.camel.Exchange
The current Exchange
request
org.apache.camel.Message
The IN message
response
org.apache.camel.Message
The OUT message
Attributes
You can add your own attributes with the attribute(name, value) DSL
method, such as:
In the sample below we add an attribute user that is an object we already
have instantiated as myUser. This object has a getFirstName() method that
we want to set as header on the message. We use the groovy language to
concat the first and last name into a single string that is returned.
from("direct:in").setHeader("name").groovy("'$user.firstName
$user.lastName'").attribute("user", myUser).to("seda:users");
L AN G UA GE S S U PP O RTE D A PPE NDIX
228
Any scripting language
Camel can run any JSR-223 scripting languages using the script DSL
method such as:
from("direct:in").setHeader("firstName").script("jaskel",
"user.firstName").attribute("user", myUser).to("seda:users");
This is a bit different using the Spring DSL where you use the expression
element that doesn't support setting attributes (yet):
<from uri="direct:in"/>
<setHeader headerName="firstName">
<expression language="jaskel">user.firstName</expression>
</setHeader>
<to uri="seda:users"/>
You can also use predicates e.g. in a Filter:
<filter>
<language
language="beanshell">request.getHeaders().get("Foo").equals("Bar")</language>
<to uri="direct:next" />
</filter>
See Scripting Languages for the list of languages with explicit DSL support.
Some languages without specific DSL support but known to work with
these generic methods include:
Language
Implementation
language="..." value
BeanShell
BeanShell 2.0b5
beanshell or bsh
Dependencies
To use scripting languages in your camel routes you need to add the a
dependency on camel-script which integrates the JSR-223 scripting engine.
If you use maven you could just add the following to your pom.xml,
substituting the version number for the latest & greatest release (see the
download page for the latest versions).
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-script</artifactId>
<version>1.4.0</version>
</dependency>
229
L A N G UA G E S S U P P ORT E D A P P E N D I X
SEE ALSO
• Languages
• DSL
• Xml Configuration
BEANSHELL
Camel supports BeanShell among other Scripting Languages to allow an
Expression or Predicate to be used in the DSL or Xml Configuration.
To use a BeanShell expression use the following Java code:
...choice()
.when(script("beanshell", "request.getHeaders().get(\"foo\").equals(\"bar\")"))
.to("...")
Or the something like this in your Spring XML:
<filter>
<language language="beanshell">request.getHeaders().get("Foo") == null</language>
...
You could follow the examples above to create an Predicate in a Message
Filter or as an Expression for a Recipient List
ScriptContext
The JSR-223 scripting languages ScriptContext is pre configured with the
following attributes all set at ENGINE_SCOPE:
Attribute
Type
Value
context
org.apache.camel.CamelContext
The Camel Context
exchange
org.apache.camel.Exchange
The current Exchange
request
org.apache.camel.Message
The IN message
response
org.apache.camel.Message
The OUT message
Attributes
You can add your own attributes with the attribute(name, value) DSL
method, such as:
In the sample below we add an attribute user that is an object we already
have instantiated as myUser. This object has a getFirstName() method that
L AN G UA GE S S U PP O RTE D A PPE NDIX
230
BeanShell Issues
You must use BeanShell 2.0b5 or greater. Note that as of 2.0b5
BeanShell cannot compile scripts, which causes Camel releases
before 2.6 to fail when configured with BeanShell expressions.
we want to set as header on the message. We use the groovy language to
concat the first and last name into a single string that is returned.
from("direct:in").setHeader("name").groovy("'$user.firstName
$user.lastName'").attribute("user", myUser).to("seda:users");
Any scripting language
Camel can run any JSR-223 scripting languages using the script DSL
method such as:
from("direct:in").setHeader("firstName").script("jaskel",
"user.firstName").attribute("user", myUser).to("seda:users");
This is a bit different using the Spring DSL where you use the expression
element that doesn't support setting attributes (yet):
<from uri="direct:in"/>
<setHeader headerName="firstName">
<expression language="jaskel">user.firstName</expression>
</setHeader>
<to uri="seda:users"/>
You can also use predicates e.g. in a Filter:
<filter>
<language
language="beanshell">request.getHeaders().get("Foo").equals("Bar")</language>
<to uri="direct:next" />
</filter>
See Scripting Languages for the list of languages with explicit DSL support.
Some languages without specific DSL support but known to work with
these generic methods include:
231
Language
Implementation
language="..." value
BeanShell
BeanShell 2.0b5
beanshell or bsh
L A N G UA G E S S U P P ORT E D A P P E N D I X
Dependencies
To use scripting languages in your camel routes you need to add the a
dependency on camel-script which integrates the JSR-223 scripting engine.
If you use maven you could just add the following to your pom.xml,
substituting the version number for the latest & greatest release (see the
download page for the latest versions).
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-script</artifactId>
<version>1.4.0</version>
</dependency>
JAVASCRIPT
Camel supports JavaScript/ECMAScript among other Scripting Languages to
allow an Expression or Predicate to be used in the DSL or Xml Configuration.
To use a JavaScript expression use the following Java code
... javaScript("someJavaScriptExpression") ...
For example you could use the javaScript function to create an Predicate in
a Message Filter or as an Expression for a Recipient List
Example
In the sample below we use JavaScript to create a Predicate use in the route
path, to route exchanges from admin users to a special queue.
from("direct:start")
.choice()
.when().javaScript("request.headers.get('user') ==
'admin'").to("seda:adminQueue")
.otherwise()
.to("seda:regularQueue");
And a Spring DSL sample as well:
<route>
<from uri="direct:start"/>
<choice>
<when>
<javaScript>request.headers.get('user') == 'admin'</javaScript>
L AN G UA GE S S U PP O RTE D A PPE NDIX
232
<to uri="seda:adminQueue"/>
</when>
<otherwise>
<to uri="seda:regularQueue"/>
</otherwise>
</choice>
</route>
ScriptContext
The JSR-223 scripting languages ScriptContext is pre configured with the
following attributes all set at ENGINE_SCOPE:
Attribute
Type
Value
context
org.apache.camel.CamelContext
The Camel Context
exchange
org.apache.camel.Exchange
The current Exchange
request
org.apache.camel.Message
The IN message
response
org.apache.camel.Message
The OUT message
Attributes
You can add your own attributes with the attribute(name, value) DSL
method, such as:
In the sample below we add an attribute user that is an object we already
have instantiated as myUser. This object has a getFirstName() method that
we want to set as header on the message. We use the groovy language to
concat the first and last name into a single string that is returned.
from("direct:in").setHeader("name").groovy("'$user.firstName
$user.lastName'").attribute("user", myUser).to("seda:users");
Any scripting language
Camel can run any JSR-223 scripting languages using the script DSL
method such as:
from("direct:in").setHeader("firstName").script("jaskel",
"user.firstName").attribute("user", myUser).to("seda:users");
This is a bit different using the Spring DSL where you use the expression
element that doesn't support setting attributes (yet):
233
L A N G UA G E S S U P P ORT E D A P P E N D I X
<from uri="direct:in"/>
<setHeader headerName="firstName">
<expression language="jaskel">user.firstName</expression>
</setHeader>
<to uri="seda:users"/>
You can also use predicates e.g. in a Filter:
<filter>
<language
language="beanshell">request.getHeaders().get("Foo").equals("Bar")</language>
<to uri="direct:next" />
</filter>
See Scripting Languages for the list of languages with explicit DSL support.
Some languages without specific DSL support but known to work with
these generic methods include:
Language
Implementation
language="..." value
BeanShell
BeanShell 2.0b5
beanshell or bsh
Dependencies
To use scripting languages in your camel routes you need to add the a
dependency on camel-script which integrates the JSR-223 scripting engine.
If you use maven you could just add the following to your pom.xml,
substituting the version number for the latest & greatest release (see the
download page for the latest versions).
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-script</artifactId>
<version>1.4.0</version>
</dependency>
GROOVY
Camel supports Groovy among other Scripting Languages to allow an
Expression or Predicate to be used in the DSL or Xml Configuration.
To use a Groovy expression use the following Java code
... groovy("someGroovyExpression") ...
L AN G UA GE S S U PP O RTE D A PPE NDIX
234
For example you could use the groovy function to create an Predicate in a
Message Filter or as an Expression for a Recipient List
Example
// lets route if a line item is over $100
from("queue:foo").filter(groovy("request.lineItems.any { i -> i.value > 100
}")).to("queue:bar")
And the Spring DSL:
<route>
<from uri="queue:foo"/>
<filter>
<groovy>request.lineItems.any { i -> i.value > 100 }</groovy>
<to uri="queue:bar"/>
</filter>
</route>
ScriptContext
The JSR-223 scripting languages ScriptContext is pre configured with the
following attributes all set at ENGINE_SCOPE:
Attribute
Type
Value
context
org.apache.camel.CamelContext
The Camel Context
exchange
org.apache.camel.Exchange
The current Exchange
request
org.apache.camel.Message
The IN message
response
org.apache.camel.Message
The OUT message
Attributes
You can add your own attributes with the attribute(name, value) DSL
method, such as:
In the sample below we add an attribute user that is an object we already
have instantiated as myUser. This object has a getFirstName() method that
we want to set as header on the message. We use the groovy language to
concat the first and last name into a single string that is returned.
from("direct:in").setHeader("name").groovy("'$user.firstName
$user.lastName'").attribute("user", myUser).to("seda:users");
235
L A N G UA G E S S U P P ORT E D A P P E N D I X
Any scripting language
Camel can run any JSR-223 scripting languages using the script DSL
method such as:
from("direct:in").setHeader("firstName").script("jaskel",
"user.firstName").attribute("user", myUser).to("seda:users");
This is a bit different using the Spring DSL where you use the expression
element that doesn't support setting attributes (yet):
<from uri="direct:in"/>
<setHeader headerName="firstName">
<expression language="jaskel">user.firstName</expression>
</setHeader>
<to uri="seda:users"/>
You can also use predicates e.g. in a Filter:
<filter>
<language
language="beanshell">request.getHeaders().get("Foo").equals("Bar")</language>
<to uri="direct:next" />
</filter>
See Scripting Languages for the list of languages with explicit DSL support.
Some languages without specific DSL support but known to work with
these generic methods include:
Language
Implementation
language="..." value
BeanShell
BeanShell 2.0b5
beanshell or bsh
Dependencies
To use scripting languages in your camel routes you need to add the a
dependency on camel-script which integrates the JSR-223 scripting engine.
If you use maven you could just add the following to your pom.xml,
substituting the version number for the latest & greatest release (see the
download page for the latest versions).
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-script</artifactId>
<version>1.4.0</version>
</dependency>
L AN G UA GE S S U PP O RTE D A PPE NDIX
236
PYTHON
Camel supports Python among other Scripting Languages to allow an
Expression or Predicate to be used in the DSL or Xml Configuration.
To use a Python expression use the following Java code
... python("somePythonExpression") ...
For example you could use the python function to create an Predicate in a
Message Filter or as an Expression for a Recipient List
Example
In the sample below we use Python to create a Predicate use in the route
path, to route exchanges from admin users to a special queue.
from("direct:start")
.choice()
.when().python("request.headers['user'] == 'admin'").to("seda:adminQueue")
.otherwise()
.to("seda:regularQueue");
And a Spring DSL sample as well:
<route>
<from uri="direct:start"/>
<choice>
<when>
<python>request.headers['user'] == 'admin'</python>
<to uri="seda:adminQueue"/>
</when>
<otherwise>
<to uri="seda:regularQueue"/>
</otherwise>
</choice>
</route>
ScriptContext
The JSR-223 scripting languages ScriptContext is pre configured with the
following attributes all set at ENGINE_SCOPE:
237
Attribute
Type
Value
context
org.apache.camel.CamelContext
The Camel Context
exchange
org.apache.camel.Exchange
The current Exchange
L A N G UA G E S S U P P ORT E D A P P E N D I X
request
org.apache.camel.Message
The IN message
response
org.apache.camel.Message
The OUT message
Attributes
You can add your own attributes with the attribute(name, value) DSL
method, such as:
In the sample below we add an attribute user that is an object we already
have instantiated as myUser. This object has a getFirstName() method that
we want to set as header on the message. We use the groovy language to
concat the first and last name into a single string that is returned.
from("direct:in").setHeader("name").groovy("'$user.firstName
$user.lastName'").attribute("user", myUser).to("seda:users");
Any scripting language
Camel can run any JSR-223 scripting languages using the script DSL
method such as:
from("direct:in").setHeader("firstName").script("jaskel",
"user.firstName").attribute("user", myUser).to("seda:users");
This is a bit different using the Spring DSL where you use the expression
element that doesn't support setting attributes (yet):
<from uri="direct:in"/>
<setHeader headerName="firstName">
<expression language="jaskel">user.firstName</expression>
</setHeader>
<to uri="seda:users"/>
You can also use predicates e.g. in a Filter:
<filter>
<language
language="beanshell">request.getHeaders().get("Foo").equals("Bar")</language>
<to uri="direct:next" />
</filter>
See Scripting Languages for the list of languages with explicit DSL support.
Some languages without specific DSL support but known to work with
these generic methods include:
L AN G UA GE S S U PP O RTE D A PPE NDIX
238
Language
Implementation
language="..." value
BeanShell
BeanShell 2.0b5
beanshell or bsh
Dependencies
To use scripting languages in your camel routes you need to add the a
dependency on camel-script which integrates the JSR-223 scripting engine.
If you use maven you could just add the following to your pom.xml,
substituting the version number for the latest & greatest release (see the
download page for the latest versions).
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-script</artifactId>
<version>1.4.0</version>
</dependency>
PHP
Camel supports PHP among other Scripting Languages to allow an Expression
or Predicate to be used in the DSL or Xml Configuration.
To use a PHP expression use the following Java code
... php("somePHPExpression") ...
For example you could use the php function to create an Predicate in a
Message Filter or as an Expression for a Recipient List
ScriptContext
The JSR-223 scripting languages ScriptContext is pre configured with the
following attributes all set at ENGINE_SCOPE:
239
Attribute
Type
Value
context
org.apache.camel.CamelContext
The Camel Context
exchange
org.apache.camel.Exchange
The current Exchange
request
org.apache.camel.Message
The IN message
response
org.apache.camel.Message
The OUT message
L A N G UA G E S S U P P ORT E D A P P E N D I X
Attributes
You can add your own attributes with the attribute(name, value) DSL
method, such as:
In the sample below we add an attribute user that is an object we already
have instantiated as myUser. This object has a getFirstName() method that
we want to set as header on the message. We use the groovy language to
concat the first and last name into a single string that is returned.
from("direct:in").setHeader("name").groovy("'$user.firstName
$user.lastName'").attribute("user", myUser).to("seda:users");
Any scripting language
Camel can run any JSR-223 scripting languages using the script DSL
method such as:
from("direct:in").setHeader("firstName").script("jaskel",
"user.firstName").attribute("user", myUser).to("seda:users");
This is a bit different using the Spring DSL where you use the expression
element that doesn't support setting attributes (yet):
<from uri="direct:in"/>
<setHeader headerName="firstName">
<expression language="jaskel">user.firstName</expression>
</setHeader>
<to uri="seda:users"/>
You can also use predicates e.g. in a Filter:
<filter>
<language
language="beanshell">request.getHeaders().get("Foo").equals("Bar")</language>
<to uri="direct:next" />
</filter>
See Scripting Languages for the list of languages with explicit DSL support.
Some languages without specific DSL support but known to work with
these generic methods include:
Language
Implementation
language="..." value
BeanShell
BeanShell 2.0b5
beanshell or bsh
L AN G UA GE S S U PP O RTE D A PPE NDIX
240
Dependencies
To use scripting languages in your camel routes you need to add the a
dependency on camel-script which integrates the JSR-223 scripting engine.
If you use maven you could just add the following to your pom.xml,
substituting the version number for the latest & greatest release (see the
download page for the latest versions).
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-script</artifactId>
<version>1.4.0</version>
</dependency>
RUBY
Camel supports Ruby among other Scripting Languages to allow an
Expression or Predicate to be used in the DSL or Xml Configuration.
To use a Ruby expression use the following Java code
... ruby("someRubyExpression") ...
For example you could use the ruby function to create an Predicate in a
Message Filter or as an Expression for a Recipient List
Example
In the sample below we use Ruby to create a Predicate use in the route path,
to route exchanges from admin users to a special queue.
from("direct:start")
.choice()
.when().ruby("$request.headers['user'] == 'admin'").to("seda:adminQueue")
.otherwise()
.to("seda:regularQueue");
And a Spring DSL sample as well:
<route>
<from uri="direct:start"/>
<choice>
<when>
<ruby>$request.headers['user'] == 'admin'</ruby>
<to uri="seda:adminQueue"/>
241
L A N G UA G E S S U P P ORT E D A P P E N D I X
</when>
<otherwise>
<to uri="seda:regularQueue"/>
</otherwise>
</choice>
</route>
ScriptContext
The JSR-223 scripting languages ScriptContext is pre configured with the
following attributes all set at ENGINE_SCOPE:
Attribute
Type
Value
context
org.apache.camel.CamelContext
The Camel Context
exchange
org.apache.camel.Exchange
The current Exchange
request
org.apache.camel.Message
The IN message
response
org.apache.camel.Message
The OUT message
Attributes
You can add your own attributes with the attribute(name, value) DSL
method, such as:
In the sample below we add an attribute user that is an object we already
have instantiated as myUser. This object has a getFirstName() method that
we want to set as header on the message. We use the groovy language to
concat the first and last name into a single string that is returned.
from("direct:in").setHeader("name").groovy("'$user.firstName
$user.lastName'").attribute("user", myUser).to("seda:users");
Any scripting language
Camel can run any JSR-223 scripting languages using the script DSL
method such as:
from("direct:in").setHeader("firstName").script("jaskel",
"user.firstName").attribute("user", myUser).to("seda:users");
This is a bit different using the Spring DSL where you use the expression
element that doesn't support setting attributes (yet):
L AN G UA GE S S U PP O RTE D A PPE NDIX
242
<from uri="direct:in"/>
<setHeader headerName="firstName">
<expression language="jaskel">user.firstName</expression>
</setHeader>
<to uri="seda:users"/>
You can also use predicates e.g. in a Filter:
<filter>
<language
language="beanshell">request.getHeaders().get("Foo").equals("Bar")</language>
<to uri="direct:next" />
</filter>
See Scripting Languages for the list of languages with explicit DSL support.
Some languages without specific DSL support but known to work with
these generic methods include:
Language
Implementation
language="..." value
BeanShell
BeanShell 2.0b5
beanshell or bsh
Dependencies
To use scripting languages in your camel routes you need to add the a
dependency on camel-script which integrates the JSR-223 scripting engine.
If you use maven you could just add the following to your pom.xml,
substituting the version number for the latest & greatest release (see the
download page for the latest versions).
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-script</artifactId>
<version>1.4.0</version>
</dependency>
SIMPLE EXPRESSION LANGUAGE
The Simple Expression Language was a really simple language you can use,
but has since grown more powerful. Its primarily intended for being a really
small and simple language for evaluating Expression and Predicate without
requiring any new dependencies or knowledge of XPath; so its ideal for
testing in camel-core. Its ideal to cover 95% of the common use cases when
you need a little bit of expression based script in your Camel routes.
243
L A N G UA G E S S U P P ORT E D A P P E N D I X
However for much more complex use cases you are generally
recommended to choose a more expressive and powerful language such as:
• JavaScript
• EL
• OGNL
• Mvel
• Groovy
• one of the supported Scripting Languages
The simple language uses ${body} placeholders for complex expressions
where the expression contains constant literals. The ${ } placeholders can
be omitted if the expression is only the token itself.
To get the body of the in message: "body", or "in.body" or "${body}".
A complex expression must use ${ } placeholders, such as: "Hello
${in.header.name} how are you?".
You can have multiple tokens in the same expression: "Hello
${in.header.name} this is ${in.header.me} speaking".
However you can not nest tokens (i.e. having another ${ } placeholder in an
existing, is not allowed).
Variables
Variable
Type
Description
exchangeId
String
Camel 2.3: the exchange id
id
String
the input message id
body
Object
the input body
in.body
Object
the input body
body.OGNL
Object
Camel 2.3: the input body invoked
using a Camel OGNL expression.
in.body.OGNL
Object
Camel 2.3: the input body invoked
using a Camel OGNL expression.
Type
Camel 2.3: Converts the body to the
given type determined by its
classname. The converted body can be
null.
Type
Camel 2.5: Converts the body to the
given type determined by its
classname, and expects the body to be
not null.
bodyAs(type)
mandatoryBodyAs(type)
L AN G UA GE S S U PP O RTE D A PPE NDIX
244
Alternative syntax
From Camel 2.5 onwards you can also use the alternative syntax
which uses $simple{ } as placeholders.
This can be used in situations to avoid clashes when using for
example Spring property placeholder together with Camel.
File language is now merged with Simple language
From Camel 2.2 onwards, the File Language is now merged with
Simple language which means you can use all the file syntax
directly within the simple language.
245
out.body
Object
the output body
header.foo
Object
refer to the input foo header
headers.foo
Object
refer to the input foo header
in.header.foo
Object
refer to the input foo header
in.headers.foo
Object
refer to the input foo header
header.foo[bar]
Object
Camel 2.3: regard input foo header as
a map and perform lookup on the map
with bar as key
in.header.foo[bar]
Object
Camel 2.3: regard input foo header as
a map and perform lookup on the map
with bar as key
in.headers.foo[bar]
Object
Camel 2.3: regard input foo header as
a map and perform lookup on the map
with bar as key
header.foo.OGNL
Object
Camel 2.3: refer to the input foo
header and invoke its value using a
Camel OGNL expression.
in.header.foo.OGNL
Object
Camel 2.3: refer to the input foo
header and invoke its value using a
Camel OGNL expression.
in.headers.foo.OGNL
Object
Camel 2.3: refer to the input foo
header and invoke its value using a
Camel OGNL expression.
L A N G UA G E S S U P P ORT E D A P P E N D I X
out.header.foo
Object
refer to the out header foo
out.headers.foo
Object
refer to the out header foo
headerAs(key,type)
Type
Camel 2.5: Converts the header to the
given type determined by its
classname
property.foo
Object
refer to the foo property on the
exchange
property.foo.OGNL
Object
Camel 2.8: refer to the foo property
on the exchange and invoke its value
using a Camel OGNL expression.
sys.foo
String
refer to the system property
sysenv.foo
String
Camel 2.3: refer to the system
environment
exception
Object
Camel 2.4: Refer to the exception
object on the exchange, is null if no
exception set on exchange. Will
fallback and grab caught exceptions
(Exchange.EXCEPTION_CAUGHT) if the
Exchange has any.
exception.OGNL
Object
Camel 2.4: Refer to the exchange
exception invoked using a Camel OGNL
expression object
String
Camel 2.0. Refer to the
exception.message on the exchange, is
null if no exception set on exchange.
Will fallback and grab caught
exceptions
(Exchange.EXCEPTION_CAUGHT) if the
Exchange has any.
String
Camel 2.6. Refer to the
exception.stracktrace on the exchange,
is null if no exception set on exchange.
Will fallback and grab caught
exceptions
(Exchange.EXCEPTION_CAUGHT) if the
Exchange has any.
exception.message
exception.stacktrace
L AN G UA GE S S U PP O RTE D A PPE NDIX
246
String
Camel 1.5. Date formatting using the
java.text.SimpleDataFormat
patterns. Supported commands are:
now for current timestamp,
in.header.xxx or header.xxx to use
the Date object in the IN header with
the key xxx. out.header.xxx to use
the Date object in the OUT header with
the key xxx.
Object
Camel 1.5. Invoking a bean
expression using the Bean language.
Specifying a method name you must
use dot as separator. In Camel 2.0 we
also support the
?method=methodname syntax that is
used by the Bean component.
properties:locations:key
String
Camel 2.3: Lookup a property with the
given key. The locations option is
optional. See more at Using
PropertyPlaceholder.
threadName
String
Camel 2.3: Returns the name of the
current thread. Can be used for logging
purpose.
ref:xxx
Object
Camel 2.6: To lookup a bean from the
Registry with the given id.
date:command:pattern
bean:bean expression
OGNL expression support
Available as of Camel 2.3
The Simple and Bean language now supports a Camel OGNL notation for
invoking beans in a chain like fashion.
Suppose the Message IN body contains a POJO which has a getAddress()
method.
Then you can use Camel OGNL notation to access the address object:
simple("${body.address}")
simple("${body.address.street}")
simple("${body.address.zip}")
Camel understands the shorthand names for getters, but you can invoke any
method or use the real name such as:
247
L A N G UA G E S S U P P ORT E D A P P E N D I X
simple("${body.address}")
simple("${body.getAddress.getStreet}")
simple("${body.address.getZip}")
simple("${body.doSomething}")
You can also use the null safe operator (?.) to avoid NPE if for example the
body does NOT have an address
simple("${body?.address?.street}")
Its also possible to index in Map or List types, so you can do:
simple("${body[foo].name}")
To assume the body is Map based and lookup the value with foo as key, and
invoke the getName method on that value.
You can access the Map or List objects directly using their key name (with
or without dots) :
simple("${body[foo]}")
simple("${body[this.is.foo]}")
Suppose there was no value with the key foo then you can use the null safe
operator to avoid the NPE as shown:
simple("${body[foo]?.name}")
You can also access List types, for example to get lines from the address
you can do:
simple("${body.address.lines[0]}")
simple("${body.address.lines[1]}")
simple("${body.address.lines[2]}")
There is a special last keyword which can be used to get the last value from
a list.
simple("${body.address.lines[last]}")
And to get the 2nd last you can subtract a number, so we can use last-1 to
indicate this:
L AN G UA GE S S U PP O RTE D A PPE NDIX
248
simple("${body.address.lines[last-1]}")
And the 3rd last is of course:
simple("${body.address.lines[last-2]}")
And yes you can combine this with the operator support as shown below:
simple("${body.address.zip} > 1000")
Operator support
Available as of Camel 2.0
We added a basic set of operators supported in the simple language in Camel
2.0. The parser is limited to only support a single operator.
To enable it the left value must be enclosed in ${ }. The syntax is:
${leftValue} OP rightValue
Where the rightValue can be a String literal enclosed in ' ', null, a
constant value or another expression enclosed in ${ }.
Camel will automatically type convert the rightValue type to the leftValue
type, so its able to eg. convert a string into a numeric so you can use >
comparison for numeric values.
The following operators is supported:
249
Operator
Description
==
equals
>
greater than
>=
greater than or equals
<
less than
<=
less than or equals
!=
not equals
contains
For testing if contains in a string based value
not
contains
For testing if not contains in a string based value
L A N G UA G E S S U P P ORT E D A P P E N D I X
regex
For matching against a given regular expression pattern
defined as a String value
not regex
For not matching against a given regular expression pattern
defined as a String value
in
For matching if in a set of values, each element must be
separated by comma.
not in
For matching if not in a set of values, each element must be
separated by comma.
is
For matching if the left hand side type is an instanceof the
value.
not is
For matching if the left hand side type is not an instanceof the
value.
range
For matching if the left hand side is within a range of values
defined as numbers: from..to
not range
For matching if the left hand side is not within a range of
values defined as numbers: from..to
And the following operators can be used to group expressions:
Operator
Description
and
and is used to group two expressions
or
or is used to group two expressions
The syntax for AND is:
${leftValue} OP rightValue and ${leftValue} OP rightValue
And the syntax for OR is:
${leftValue} OP rightValue or ${leftValue} OP rightValue
Some examples:
simple("${in.header.foo} == 'foo'")
// ' ' can be omitted
simple("${in.header.foo} == foo")
// here Camel will type convert '100' into the type of in.header.bar and if its an
Integer '100' will also be converter to an Integer
simple("${in.header.bar} == '100'")
L AN G UA GE S S U PP O RTE D A PPE NDIX
250
Using and,or operators
In Camel 2.4 or older the and or or can only be used once in a
simple language expression. From Camel 2.5 onwards you can use
these operators multiple times.
simple("${in.header.bar} == 100")
// 100 will be converter to the type of in.header.bar so we can do > comparison
simple("${in.header.bar} > 100")
// testing for null
simple("${in.header.baz} == null")
// testing for not null
simple("${in.header.baz} != null")
And a bit more advanced example where the right value is another
expression
simple("${in.header.date} == ${date:now:yyyyMMdd}")
simple("${in.header.type} == ${bean:orderService?method=getOrderType}")
And an example with contains, testing if the title contains the word Camel
simple("${in.header.title} contains 'Camel'")
And an example with regex, testing if the number header is a 4 digit value:
simple("${in.header.number} regex '\d{4}'")
And finally an example if the header equals any of the values in the list. Each
element must be separated by comma, and no space around.
This also works for numbers etc, as Camel will convert each element into the
type of the left hand side.
simple("${in.header.type} in 'gold,silver'")
And for all the last 3 we also support the negate test using not:
251
L A N G UA G E S S U P P ORT E D A P P E N D I X
Comparing with different types
When you compare with different types such as String and int, then
you have to take a bit care. Camel will use the type from the left
hand side as 1st priority. And fallback to the right hand side type if
both values couldn't be compared based on that type.
This means you can flip the values to enforce a specific type.
Suppose the bar value above is a String. Then you can flip the
equation:
simple("100 < ${in.header.bar}")
which then ensures the int type is used as 1st priority.
This may change in the future if the Camel team improves and let the
binary comparision operations be smarter and prefer numeric types over
String based. It's most often the String type which causes problem when
comparing with numbers.
simple("${in.header.type} not in 'gold,silver'")
And you can test for if the type is a certain instance, eg for instance a String
simple("${in.header.type} is 'java.lang.String'")
We have added a shorthand for all java.lang types so you can write it as:
simple("${in.header.type} is String")
Ranges is also supported. The range interval requires numbers and both from
and end is inclusive. For instance to test whether a value is between 100 and
199:
simple("${in.header.number} range 100..199")
Notice we use .. in the range without spaces. Its based on the same syntax
as Groovy.
L AN G UA GE S S U PP O RTE D A PPE NDIX
252
Can be used in Spring XML
As the Spring XML does not have all the power as the Java DSL with
all its various builder methods, you had to resort to use some other
languages
for testing with simple operators. Now you can do this with the
simple language. In the sample below we want to test if the header
is a widget order:
<from uri="seda:orders">
<filter>
<simple>${in.header.type} == 'widget'</simple>
<to uri="bean:orderService?method=handleWidget"/>
</filter>
</from>
Using and / or
If you have two expressions you can combine them with the and or or
operator.
For instance:
simple("${in.header.title} contains 'Camel' and ${in.header.type'} == 'gold'")
And of course the or is also supported. The sample example would be:
simple("${in.header.title} contains 'Camel' or ${in.header.type'} == 'gold'")
Notice: Currently and or or can only be used once in a simple language
expression. This might change in the future.
So you cannot do:
simple("${in.header.title} contains 'Camel' and ${in.header.type'} == 'gold' and
${in.header.number} range 100..200")
Samples
In the Spring XML sample below we filter based on a header value:
<from uri="seda:orders">
<filter>
253
L A N G UA G E S S U P P ORT E D A P P E N D I X
<simple>in.header.foo</simple>
<to uri="mock:fooOrders"/>
</filter>
</from>
The Simple language can be used for the predicate test above in the
Message Filter pattern, where we test if the in message has a foo header (a
header with the key foo exists). If the expression evaluates to true then the
message is routed to the mock:foo endpoint, otherwise its lost in the deep
blue sea
.
The same example in Java DSL:
from("seda:orders")
.filter().simple("in.header.foo").to("seda:fooOrders");
You can also use the simple language for simple text concatenations such as:
from("direct:hello").transform().simple("Hello ${in.header.user} how are
you?").to("mock:reply");
Notice that we must use ${ } placeholders in the expression now to let
Camel be able to parse it correctly.
And this sample uses the date command to output current date.
from("direct:hello").transform().simple("The today is ${date:now:yyyyMMdd} and its
a great day.").to("mock:reply");
And in the sample below we invoke the bean language to invoke a method on
a bean to be included in the returned string:
from("direct:order").transform().simple("OrderId:
${bean:orderIdGenerator}").to("mock:reply");
Where orderIdGenerator is the id of the bean registered in the Registry. If
using Spring then its the Spring bean id.
If we want to declare which method to invoke on the order id generator
bean we must prepend .method name such as below where we invoke the
generateId method.
from("direct:order").transform().simple("OrderId:
${bean:orderIdGenerator.generateId}").to("mock:reply");
L AN G UA GE S S U PP O RTE D A PPE NDIX
254
And in Camel 2.0 we can use the ?method=methodname option that we are
familiar with the Bean component itself:
from("direct:order").transform().simple("OrderId:
${bean:orderIdGenerator?method=generateId}").to("mock:reply");
And from Camel 2.3 onwards you can also convert the body to a given type,
for example to ensure its a String you can do:
<transform>
<simple>Hello ${bodyAs(String)} how are you?</simple>
</transform>
There is a few types which have a shorthand notation, hence why we can use
String instead of java.lang.String. These are: byte[], String,
Integer, Long. All other types must use their FQN name, e.g.
org.w3c.dom.Document.
Its also possible to lookup a value from a header Map in Camel 2.3
onwards:
<transform>
<simple>The gold value is ${header.type[gold]}</simple>
</transform>
In the code above we lookup the header with name type and regard it as a
java.util.Map and we then lookup with the key gold and return the value.
If the header is not convertible to Map an exception is thrown. If the header
with name type does not exists null is returned.
Dependencies
The Simple language is part of camel-core.
FILE EXPRESSION LANGUAGE
Available as of Camel 1.5
The File Expression Language is an extension to the Simple language, adding
file related capabilities. These capabilities is related to common use cases
working with file path and names. The goal is to allow expression to be used
with the File and FTP components for setting dynamic file patterns for both
consumer and producer.
255
L A N G UA G E S S U P P ORT E D A P P E N D I X
File language is now merged with Simple language
From Camel 2.2 onwards, the file language is now merged with
Simple language which means you can use all the file syntax
directly within the simple language.
Syntax
This language is an extension to the Simple language so the Simple syntax
applies also. So the table below only lists the additional.
As opposed to Simple language File Language also supports Constant
expressions so you can enter a fixed filename.
All the file tokens uses the same expression name as the method on the
java.io.File object, for instance file:absolute refers to the
java.io.File.getAbsolute() method. Notice that not all expressions is
supported by the current Exchange. For instance the FTP component
supports some of the options, where as the File component support all of
them.
Expression
Type
File
Consumer
File
Producer
FTP
Consumer
FTP
Producer
Description
file:name
String
yes
no
yes
no
refers to the file name (is
relative to the starting
directory, see note below)
file:name.ext
String
yes
no
yes
no
Camel 2.3: refers to the file
extension only
file:name.noext
String
yes
no
yes
no
refers to the file name with no
extension (is relative to the
starting directory, see note
below)
file:onlyname
String
yes
no
yes
no
Camel 2.0: refers to the file
name only with no leading
paths.
file:onlyname.noext
String
yes
no
yes
no
Camel 2.0: refers to the file
name only with no extension
and with no leading paths.
file:ext
String
yes
no
yes
no
Camel 1.6.1/Camel 2.0: refers
to the file extension only
file:parent
String
yes
no
yes
no
refers to the file parent
file:path
String
yes
no
yes
no
refers to the file path
file:absolute
Boolean
yes
no
no
no
Camel 2.0: refers to whether
the file is regarded as absolute
or relative
file:absolute.path
String
yes
no
no
no
refers to the absolute file path
file:length
Long
yes
no
yes
no
refers to the file length returned
as a Long type
file:size
Long
yes
no
yes
no
Camel 2.5: refers to the file
length returned as a Long type
file:modified
Date
yes
no
yes
no
Camel 2.0: refers to the file
last modified returned as a Date
type
L AN G UA GE S S U PP O RTE D A PPE NDIX
256
date:command:pattern
String
yes
yes
yes
yes
for date formatting using the
java.text.SimepleDataFormat
patterns. Is an extension to
the Simple language. Additional
command is: file (consumers
only) for the last modified
timestamp of the file. Notice: all
the commands from the Simple
language can also be used.
File token example
Relative paths
We have a java.io.File handle for the file hello.txt in the following
relative directory: .\filelanguage\test. And we configure out endpoint to
use this starting directory .\filelanguage. The the file tokens will return as:
Expression
Returns
file:name
test\hello.txt
file:name.ext
txt
file:name.noext
test\hello
file:onlyname
hello.txt
file:onlyname.noext
hello
file:ext
txt
file:parent
filelanguage\test
file:path
filelanguage\test\hello.txt
file:absolute
false
file:absolute.path
\workspace\camel\camelcore\target\filelanguage\test\hello.txt
Absolute paths
We have a java.io.File handle for the file hello.txt in the following
absolute directory: \workspace\camel\camelcore\target\filelanguage\test. And we configure out endpoint to use the
absolute starting directory \workspace\camel\camelcore\target\filelanguage. The the file tokens will return as:
257
Expression
Returns
file:name
test\hello.txt
L A N G UA G E S S U P P ORT E D A P P E N D I X
file:name.ext
txt
file:name.noext
test\hello
file:onlyname
hello.txt
file:onlyname.noext
hello
file:ext
txt
file:parent
\workspace\camel\camelcore\target\filelanguage\test
file:path
\workspace\camel\camelcore\target\filelanguage\test\hello.txt
file:absolute
true
file:absolute.path
\workspace\camel\camelcore\target\filelanguage\test\hello.txt
Samples
You can enter a fixed Constant expression such as myfile.txt:
fileName="myfile.txt"
Lets assume we use the file consumer to read files and want to move the
read files to backup folder with the current date as a sub folder. This can be
archived using an expression like:
fileName="backup/${date:now:yyyyMMdd}/${file:name.noext}.bak"
relative folder names is also supported so suppose the backup folder should
be a sibling folder then you can append .. as:
fileName="../backup/${date:now:yyyyMMdd}/${file:name.noext}.bak"
As this is an extension to the Simple language we have access to all the
goodies from this language also, so in this use case we want to use the
in.header.type as a parameter in the dynamic expression:
fileName="../backup/${date:now:yyyyMMdd}/type-${in.header.type}/
backup-of-${file:name.noext}.bak"
If you have a custom Date you want to use in the expression then Camel
supports retrieving dates from the message header.
L AN G UA GE S S U PP O RTE D A PPE NDIX
258
fileName="orders/
order-${in.header.customerId}-${date:in.header.orderDate:yyyyMMdd}.xml"
And finally we can also use a bean expression to invoke a POJO class that
generates some String output (or convertible to String) to be used:
fileName="uniquefile-${bean:myguidgenerator.generateid}.txt"
And of course all this can be combined in one expression where you can use
the File Language, Simple and the Bean language in one combined
expression. This is pretty powerful for those common file path patterns.
Using Spring PropertyPlaceholderConfigurer together with the File
component
In Camel you can use the File Language directly from the Simple language
which makes a Content Based Router more easy to do in Spring XML, where
we can route based on file extensions as shown below:
<from uri="file://input/orders"/>
<choice>
<when>
<simple>${file:ext} == 'txt'</simple>
<to uri="bean:orderService?method=handleTextFiles"/>
</when>
<when>
<simple>${file:ext} == 'xml'</simple>
<to uri="bean:orderService?method=handleXmlFiles"/>
</when>
<otherwise>
<to uri="bean:orderService?method=handleOtherFiles"/>
</otherwise>
</choice>
If you use the fileName option on the File endpoint to set a dynamic
filename using the File Language then make sure you
use the alternative syntax (available from Camel 2.5 onwards) to avoid clash
with Springs PropertyPlaceholderConfigurer.
Listing 20. bundle-context.xml
<bean id="propertyPlaceholder"
class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="location" value="classpath:bundle-context.cfg" />
</bean>
<bean id="sampleRoute" class="SampleRoute">
259
L A N G UA G E S S U P P ORT E D A P P E N D I X
<property name="fromEndpoint" value="${fromEndpoint}" />
<property name="toEndpoint" value="${toEndpoint}" />
</bean>
Listing 21. bundle-context.cfg
fromEndpoint=activemq:queue:test
toEndpoint=file://fileRoute/out?fileName=test-$simple{date:now:yyyyMMdd}.txt
Notice how we use the $simple{ } syntax in the toEndpoint above.
If you don't do this, there is a class and Spring will thrown an exception like
org.springframework.beans.factory.BeanDefinitionStoreException:
Invalid bean definition with name 'sampleRoute' defined in class path resource
[bundle-context.xml]:
Could not resolve placeholder 'date:now:yyyyMMdd'
Dependencies
The File language is part of camel-core.
SQL
The SQL support is added by JoSQL and is primarily used for performing SQL
queries on in-memory objects. If you prefer to perform actual database
queries then check out the JPA component.
To use SQL in your camel routes you need to add the a dependency on
camel-josql which implements the SQL language.
If you use maven you could just add the following to your pom.xml,
substituting the version number for the latest & greatest release (see the
download page for the latest versions).
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-josql</artifactId>
<version>2.5.0</version>
</dependency>
Camel supports SQL to allow an Expression or Predicate to be used in the
DSL or Xml Configuration. For example you could use SQL to create an
Predicate in a Message Filter or as an Expression for a Recipient List.
from("queue:foo").setBody().sql("select * from MyType").to("queue:bar")
L AN G UA GE S S U PP O RTE D A PPE NDIX
260
And the spring DSL:
<from uri="queue:foo"/>
<setBody>
<sql>select * from MyType</sql>
</setBody>
<to uri="queue:bar"/>
Variables
Variable
Type
Description
exchange
Exchange
the Exchange object
in
Message
the exchange.in message
out
Message
the exchange.out message
the
property
key
Object
the Exchange properties
the header
key
Object
the exchange.in headers
the variable
key
Object
if any additional variables is added using
setVariables method
XPATH
Camel supports XPath to allow an Expression or Predicate to be used in the
DSL or Xml Configuration. For example you could use XPath to create an
Predicate in a Message Filter or as an Expression for a Recipient List.
from("queue:foo").
filter().xpath("//foo")).
to("queue:bar")
from("queue:foo").
choice().xpath("//foo")).to("queue:bar").
otherwise().to("queue:others");
261
L A N G UA G E S S U P P ORT E D A P P E N D I X
Namespaces
In 1.3 onwards you can easily use namespaces with XPath expressions using
the Namespaces helper class.
Namespaces ns = new Namespaces("c", "http://acme.com/cheese");
from("direct:start").filter().
xpath("/c:person[@name='James']", ns).
to("mock:result");
Variables
Variables in XPath is defined in different namespaces. The default namespace
is http://camel.apache.org/schema/spring.
Namespace URI
Local
part
Type
Description
http://camel.apache.org/xml/in/
in
Message
the exchange.in
message
http://camel.apache.org/xml/out/
out
Message
the
exchange.out
message
http://camel.apache.org/xml/
functions/
functions
Object
Camel 2.5:
Additional
functions
http://camel.apache.org/xml/
variables/environment-variables
env
Object
OS environment
variables
http://camel.apache.org/xml/
variables/system-properties
system
Object
Java System
properties
http://camel.apache.org/xml/
variables/exchange-property
Â
Object
the exchange
property
Camel will resolve variables according to either:
▪ namespace given
▪ no namespace given
Namespace given
If the namespace is given then Camel is instructed exactly what to return.
However when resolving either in or out Camel will try to resolve a header
L AN G UA GE S S U PP O RTE D A PPE NDIX
262
with the given local part first, and return it. If the local part has the value
body then the body is returned instead.
No namespace given
If there is no namespace given then Camel resolves only based on the local
part. Camel will try to resolve a variable in the following steps:
▪ from variables that has been set using the variable(name,
value) fluent builder
▪ from message.in.header if there is a header with the given key
▪ from exchange.properties if there is a property with the given key
Functions
Camel adds the following XPath functions that can be used to access the
exchange:
Function
Argument
Type
Description
in:body
none
Object
Will return the in message
body.
in:header
the header
name
Object
Will return the in message
header.
out:body
none
Object
Will return the out message
body.
out:header
the header
name
Object
Will return the out message
header.
function:properties
key for
property
String
Camel 2.5: To lookup a
property using the Properties
component (property
placeholders).
function:simple
simple
expression
Object
Camel 2.5: To evaluate a
Simple expression.
Here's an example showing some of these functions in use.
from("direct:start").choice()
.when().xpath("in:header('foo') = 'bar'").to("mock:x")
.when().xpath("in:body() = '<two/>'").to("mock:y")
.otherwise().to("mock:z");
And the new functions introduced in Camel 2.5:
263
L A N G UA G E S S U P P ORT E D A P P E N D I X
// setup properties component
PropertiesComponent properties = new PropertiesComponent();
properties.setLocation("classpath:org/apache/camel/builder/xml/myprop.properties");
context.addComponent("properties", properties);
// myprop.properties contains the following properties
// foo=Camel
// bar=Kong
from("direct:in").choice()
// $type is a variable for the header with key type
// here we use the properties function to lookup foo from the properties files
// which at runtime will be evaluted to 'Camel'
.when().xpath("$type = function:properties('foo')")
.to("mock:camel")
// here we use the simple language to evaluate the expression
// which at runtime will be evaluated to 'Donkey Kong'
.when().xpath("//name = function:simple('Donkey ${properties:bar}')")
.to("mock:donkey")
.otherwise()
.to("mock:other")
.end();
Using XML configuration
If you prefer to configure your routes in your Spring XML file then you can
use XPath expressions as follows
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/
schema/beans/spring-beans-2.0.xsd
http://camel.apache.org/schema/spring http://camel.apache.org/schema/spring/
camel-spring.xsd">
<camelContext id="camel" xmlns="http://activemq.apache.org/camel/schema/spring"
xmlns:foo="http://example.com/person">
<route>
<from uri="activemq:MyQueue"/>
<filter>
<xpath>/foo:person[@name='James']</xpath>
<to uri="mqseries:SomeOtherQueue"/>
</filter>
</route>
</camelContext>
</beans>
Notice how we can reuse the namespace prefixes, foo in this case, in the
XPath expression for easier namespace based XPath expressions!
L AN G UA GE S S U PP O RTE D A PPE NDIX
264
See also this discussion on the mailinglist about using your own
namespaces with xpath
Setting result type
The XPath expression will return a result type using native XML objects such
as org.w3c.dom.NodeList. But many times you want a result type to be a
String. To do this you have to instruct the XPath which result type to use.
In Java DSL:
xpath("/foo:person/@id", String.class)
In Spring DSL you use the resultType attribute to provide a fully qualified
classname:
<xpath resultType="java.lang.String">/foo:person/@id</xpath>
In @XPath:
Available as of Camel 2.1
@XPath(value = "concat('foo-',//order/name/)", resultType = String.class) String name)
Where we use the xpath function concat to prefix the order name with foo-.
In this case we have to specify that we want a String as result type so the
concat function works.
Examples
Here is a simple example using an XPath expression as a predicate in a
Message Filter
from("direct:start").
filter().xpath("/person[@name='James']").
to("mock:result");
If you have a standard set of namespaces you wish to work with and wish to
share them across many different XPath expressions you can use the
NamespaceBuilder as shown in this example
// lets define the namespaces we'll need in our filters
Namespaces ns = new Namespaces("c", "http://acme.com/cheese")
.add("xsd", "http://www.w3.org/2001/XMLSchema");
265
L A N G UA G E S S U P P ORT E D A P P E N D I X
// now lets create an xpath based Message Filter
from("direct:start").
filter(ns.xpath("/c:person[@name='James']")).
to("mock:result");
In this sample we have a choice construct. The first choice evaulates if the
message has a header key type that has the value Camel.
The 2nd choice evaluates if the message body has a name tag <name>
which values is Kong.
If neither is true the message is routed in the otherwise block:
from("direct:in").choice()
// using $headerName is special notation in Camel to get the header key
.when().xpath("$type = 'Camel'")
.to("mock:camel")
// here we test for the body name tag
.when().xpath("//name = 'Kong'")
.to("mock:donkey")
.otherwise()
.to("mock:other")
.end();
And the spring XML equivalent of the route:
<camelContext xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="direct:in"/>
<choice>
<when>
<xpath>$type = 'Camel'</xpath>
<to uri="mock:camel"/>
</when>
<when>
<xpath>//name = 'Kong'</xpath>
<to uri="mock:donkey"/>
</when>
<otherwise>
<to uri="mock:other"/>
</otherwise>
</choice>
</route>
</camelContext>
XPATH INJECTION
You can use Bean Integration to invoke a method on a bean and use various
languages such as XPath to extract a value from the message and bind it to a
method parameter.
L AN G UA GE S S U PP O RTE D A PPE NDIX
266
The default XPath annotation has SOAP and XML namespaces available. If
you want to use your own namespace URIs in an XPath expression you can
use your own copy of the XPath annotation to create whatever namespace
prefixes you want to use.
import
import
import
import
java.lang.annotation.ElementType;
java.lang.annotation.Retention;
java.lang.annotation.RetentionPolicy;
java.lang.annotation.Target;
import org.w3c.dom.NodeList;
import org.apache.camel.component.bean.XPathAnnotationExpressionFactory;
import org.apache.camel.language.LanguageAnnotation;
import org.apache.camel.language.NamespacePrefix;
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.FIELD, ElementType.METHOD, ElementType.PARAMETER})
@LanguageAnnotation(language = "xpath", factory =
XPathAnnotationExpressionFactory.class)
public @interface MyXPath {
String value();
// You can add the namespaces as the default value of the annotation
NamespacePrefix[] namespaces() default {
@NamespacePrefix(prefix = "n1", uri = "http://example.org/ns1"),
@NamespacePrefix(prefix = "n2", uri = "http://example.org/ns2")};
Class<?> resultType() default NodeList.class;
}
i.e. cut and paste upper code to your own project in a different package and/
or annotation name then add whatever namespace prefix/uris you want in
scope when you use your annotation on a method parameter. Then when you
use your annotation on a method parameter all the namespaces you want
will be available for use in your XPath expression.
NOTE this feature is supported from Camel 1.6.1.
For example
public class Foo {
@MessageDriven(uri = "activemq:my.queue")
public void doSomething(@Path("/ns1:foo/ns2:bar/text()") String correlationID,
@Body String body) {
// process the inbound message here
}
}
267
L A N G UA G E S S U P P ORT E D A P P E N D I X
Using XPathBuilder without an Exchange
Available as of Camel 2.3
You can now use the org.apache.camel.builder.XPathBuilder without
the need for an Exchange. This comes handy if you want to use it as a helper
to do custom xpath evaluations.
It requires that you pass in a CamelContext since a lot of the moving parts
inside the XPathBuilder requires access to the Camel Type Converter and
hence why CamelContext is needed.
For example you can do something like this:
boolean matches = XPathBuilder.xpath("/foo/bar/@xyz").matches(context, "<foo><bar
xyz='cheese'/></foo>"));
This will match the given predicate.
You can also evaluate for example as shown in the following three
examples:
String name = XPathBuilder.xpath("foo/bar").evaluate(context,
"<foo><bar>cheese</bar></foo>", String.class);
Integer number = XPathBuilder.xpath("foo/bar").evaluate(context,
"<foo><bar>123</bar></foo>", Integer.class);
Boolean bool = XPathBuilder.xpath("foo/bar").evaluate(context,
"<foo><bar>true</bar></foo>", Boolean.class);
Evaluating with a String result is a common requirement and thus you can do
it a bit simpler:
String name = XPathBuilder.xpath("foo/bar").evaluate(context,
"<foo><bar>cheese</bar></foo>");
Using Saxon with XPathBuilder
Available as of Camel 2.3
You need to add camel-saxon as dependency to your project.
Its now easier to use Saxon with the XPathBuilder which can be done in
several ways as shown below.
Where as the latter ones are the easiest ones.
Using a factory
// create a Saxon factory
XPathFactory fac = new net.sf.saxon.xpath.XPathFactoryImpl();
L AN G UA GE S S U PP O RTE D A PPE NDIX
268
// create a builder to evaluate the xpath using the saxon factory
XPathBuilder builder = XPathBuilder.xpath("tokenize(/foo/bar, '_')[2]").factory(fac);
// evaluate as a String result
String result = builder.evaluate(context, "<foo><bar>abc_def_ghi</bar></foo>");
assertEquals("def", result);
Using ObjectModel
// create a builder to evaluate the xpath using saxon based on its object model uri
XPathBuilder builder = XPathBuilder.xpath("tokenize(/foo/bar,
'_')[2]").objectModel("http://saxon.sf.net/jaxp/xpath/om");
// evaluate as a String result
String result = builder.evaluate(context, "<foo><bar>abc_def_ghi</bar></foo>");
assertEquals("def", result);
The easy one
// create a builder to evaluate the xpath using saxon
XPathBuilder builder = XPathBuilder.xpath("tokenize(/foo/bar, '_')[2]").saxon();
// evaluate as a String result
String result = builder.evaluate(context, "<foo><bar>abc_def_ghi</bar></foo>");
assertEquals("def", result);
Setting a custom XPathFactory using System Property
Available as of Camel 2.3
Camel now supports reading the JVM system property
javax.xml.xpath.XPathFactory that can be used to set a custom
XPathFactory to use.
This unit test shows how this can be done to use Saxon instead:
// set system property with the XPath factory to use which is Saxon
System.setProperty(XPathFactory.DEFAULT_PROPERTY_NAME + ":" + "http://saxon.sf.net/
jaxp/xpath/om", "net.sf.saxon.xpath.XPathFactoryImpl");
// create a builder to evaluate the xpath using saxon
XPathBuilder builder = XPathBuilder.xpath("tokenize(/foo/bar, '_')[2]");
// evaluate as a String result
String result = builder.evaluate(context, "<foo><bar>abc_def_ghi</bar></foo>");
assertEquals("def", result);
Camel will log at INFO level if it uses a non default XPathFactory such as:
269
L A N G UA G E S S U P P ORT E D A P P E N D I X
XPathBuilder INFO Using system property
javax.xml.xpath.XPathFactory:http://saxon.sf.net/jaxp/xpath/om with value:
net.sf.saxon.xpath.XPathFactoryImpl when creating XPathFactory
Dependencies
The XPath language is part of camel-core.
XQUERY
Camel supports XQuery to allow an Expression or Predicate to be used in the
DSL or Xml Configuration. For example you could use XQuery to create an
Predicate in a Message Filter or as an Expression for a Recipient List.
from("queue:foo").filter().
xquery("//foo").
to("queue:bar")
You can also use functions inside your query, in which case you need an
explicit type conversion (or you will get a org.w3c.dom.DOMException:
HIERARCHY_REQUEST_ERR) by passing the Class as a second argument to
the xquery() method.
from("direct:start").
recipientList().xquery("concat('mock:foo.', /person/@city)", String.class);
Variables
The IN message body will be set as the contextItem. Besides this these
Variables is also added as parameters:
Variable
Type
Description
Support
version
exchange
Exchange
The current Exchange
Â
in.body
Object
The In message's body
>=
1.6.1
out.body
Object
The OUT message's body (if any)
>=
1.6.1
L AN G UA GE S S U PP O RTE D A PPE NDIX
270
in.headers.*
out.headers.*
key name
Object
You can access the value of
exchange.in.headers with key foo
by using the variable which name is
in.headers.foo
>=1.6.1
Object
You can access the value of
exchange.out.headers with key foo
by using the variable which name is
out.headers.foo variable
>=1.6.1
Object
Any exchange.properties and
exchange.in.headers
(exchange.in.headers support was
removed since camel 1.6.1) and
any additional parameters set
using setParameters(Map). These
parameters is added with they own
key name, for instance if there is an
IN header with the key name foo
then its added as foo.
Â
Using XML configuration
If you prefer to configure your routes in your Spring XML file then you can
use XPath expressions as follows
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:foo="http://example.com/person"
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/
schema/beans/spring-beans-2.0.xsd
http://camel.apache.org/schema/spring http://camel.apache.org/schema/spring/
camel-spring.xsd">
<camelContext id="camel" xmlns="http://activemq.apache.org/camel/schema/spring">
<route>
<from uri="activemq:MyQueue"/>
<filter>
<xquery>/foo:person[@name='James']</xquery>
<to uri="mqseries:SomeOtherQueue"/>
</filter>
</route>
</camelContext>
</beans>
Notice how we can reuse the namespace prefixes, foo in this case, in the
XPath expression for easier namespace based XQuery expressions!
271
L A N G UA G E S S U P P ORT E D A P P E N D I X
When you use functions in your XQuery expression you need an explicit
type conversion which is done in the xml configuration via the @type
attribute:
<xquery type="java.lang.String">concat('mock:foo.', /person/@city)</xquery>
Using XQuery as an endpoint
Sometimes an XQuery expression can be quite large; it can essentally be
used for Templating. So you may want to use an XQuery Endpoint so you can
route using XQuery templates.
The following example shows how to take a message of an ActiveMQ
queue (MyQueue) and transform it using XQuery and send it to MQSeries.
<camelContext id="camel" xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="activemq:MyQueue"/>
<to uri="xquery:com/acme/someTransform.xquery"/>
<to uri="mqseries:SomeOtherQueue"/>
</route>
</camelContext>
Examples
Here is a simple example using an XQuery expression as a predicate in a
Message Filter
from("direct:start").filter().xquery("/person[@name='James']").to("mock:result");
This example uses XQuery with namespaces as a predicate in a Message
Filter
Namespaces ns = new Namespaces("c", "http://acme.com/cheese");
from("direct:start").
filter().xquery("/c:person[@name='James']", ns).
to("mock:result");
Learning XQuery
XQuery is a very powerful language for querying, searching, sorting and
returning XML. For help learning XQuery try these tutorials
• Mike Kay's XQuery Primer
L AN G UA GE S S U PP O RTE D A PPE NDIX
272
• the W3Schools XQuery Tutorial
You might also find the XQuery function reference useful
Dependencies
To use XQuery in your camel routes you need to add the a dependency on
camel-saxon which implements the XQuery language.
If you use maven you could just add the following to your pom.xml,
substituting the version number for the latest & greatest release (see the
download page for the latest versions).
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-saxon</artifactId>
<version>1.4.0</version>
</dependency>
273
L A N G UA G E S S U P P ORT E D A P P E N D I X
Data Format Appendix
DATA FORMAT
Camel supports a pluggable DataFormat to allow messages to be marshalled
to and from binary or text formats to support a kind of Message Translator.
The following data formats are currently supported:
• Standard JVM object marshalling
◦ Serialization
◦ String
• Object marshalling
◦ JSON
◦ Protobuf
• Object/XML marshalling
◦ Castor
◦ JAXB
◦ XmlBeans
◦ XStream
◦ JiBX
• Object/XML/Webservice marshalling
◦ SOAP
• Flat data structure marshalling
◦ Artix Data Services
◦ Bindy
◦ CSV
◦ EDI
◦ Flatpack DataFormat
• Domain specific marshalling
◦ HL7 DataFormat
• Compression
◦ GZip data format
◦ Zip DataFormat
• Security
◦ Crypto
◦ XMLSecurity DataFormat
• Misc.
◦ TidyMarkup
◦ Syslog
And related is the following Type Converters:
▪ Dozer Type Conversion
D ATA F O R M AT A PPE NDIX
274
Unmarshalling
If you receive a message from one of the Camel Components such as File,
HTTP or JMS you often want to unmarshal the payload into some bean so that
you can process it using some Bean Integration or perform Predicate
evaluation and so forth. To do this use the unmarshal word in the DSL in
Java or the Xml Configuration.
For example
DataFormat jaxb = new JaxbDataFormat("com.acme.model");
from("activemq:My.Queue").
unmarshal(jaxb).
to("mqseries:Another.Queue");
The above uses a named DataFormat of jaxb which is configured with a
number of Java package names. You can if you prefer use a named reference
to a data format which can then be defined in your Registry such as via your
Spring XML file.
You can also use the DSL itself to define the data format as you use it. For
example the following uses Java serialization to unmarshal a binary file then
send it as an ObjectMessage to ActiveMQ
from("file://foo/bar").
unmarshal().serialization().
to("activemq:Some.Queue");
Marshalling
Marshalling is the opposite of unmarshalling, where a bean is marshalled into
some binary or textual format for transmission over some transport via a
Camel Component. Marshalling is used in the same way as unmarshalling
above; in the DSL you can use a DataFormat instance, you can configure the
DataFormat dynamically using the DSL or you can refer to a named instance
of the format in the Registry.
The following example unmarshals via serialization then marshals using a
named JAXB data format to perform a kind of Message Translator
from("file://foo/bar").
unmarshal().serialization().
marshal("jaxb").
to("activemq:Some.Queue");
275
D ATA F O R MAT A P P E N D I X
Using Spring XML
This example shows how to configure the data type just once and reuse it on
multiple routes
<camelContext id="camel" xmlns="http://camel.apache.org/schema/spring">
<dataFormats>
<jaxb id="myJaxb" prettyPrint="true" contextPath="org.apache.camel.example"/>
</dataFormats>
<route>
<from uri="direct:start"/>
<marshal ref="myJaxb"/>
<to uri="direct:marshalled"/>
</route>
<route>
<from uri="direct:marshalled"/>
<unmarshal ref="myJaxb"/>
<to uri="mock:result"/>
</route>
</camelContext>
You can also define reusable data formats as Spring beans
<bean id="myJaxb" class="org.apache.camel.model.dataformat.JaxbDataFormat">
<property name="prettyPrint" value="true"/>
<property name="contextPath" value="org.apache.camel.example"/>
</bean>
ARTIX DATA SERVICES
Deprecated, will be removed in Apache Camel 2.1
The Artix DS Data Format supports the Artix Data Services (ADS) product
which provides a framework for reading and writing a huge number of
vertical message payloads like SWIFT, SEPA, FpML, TWIST, ISO 20022, CREST
and FIX. In addition ADS provides tooling and a framework for reading and
writing any legacy binary or text file using any kind of encoding like fixed
width, delimited, XML, CSV and so forth.
ADS also provides a transformation framework making it very easy to
implement the Message Translator pattern using the ADS tooling to design
the transformation.
D ATA F O R M AT A PPE NDIX
276
Unmarhalling
The first step to using ADS is usually to unmarshal some message from one
of the Camel Components like File, HTTP or JMS etc.
from("activemq:InputQueue").
unmarshal().artixDS(DocumentElement.class).
to("mqseries:OutputQueue");
The above unmarshals using the Artix DS Data Format for the element
DocumentElement which is generated by the Artix DS tooling;
DocumentElement is the root element of the message structure.
The above will use the default formatting for the data type. However with
Artix DS you can switch from the default format to other formats easily. So
you could add a specific format if you wish...
from("activemq:InputQueue").
unmarshal().artixDS(DocumentElement.class, ArtixDSContentType.Xml).
to("mqseries:OutputQueue");
If you use static imports this can be even more readable...
unmarshal().artixDS(DocumentElement.class, Xml).
Unmarshalling SWIFT messages
If you are working with SWIFT messages then as of camel-artixds version
1.3.6.0 or later there is a handy SwiftFormat helper class which avoids you
having to know which Element class you want to use.
So you can unmarshal SWIFT messages using this code
from("activemq:InputQueue").
unmarshal(new SwiftFormat()).
to("mqseries:OutputQueue");
Marshalling
Marshalling is the reverse of unmarshalling suprise suprise
.
Here's an example which unmarshals using one format (XML) and then
marshals using a different format (in this case tagged value pairs).
277
D ATA F O R MAT A P P E N D I X
from("activemq:XmlInput").
unmarshal().artixDS(DocumentElement.class, ArtixDSContentType.Xml).
marshal().artixDS(ArtixDSContentType.TagValuePair).
to("mqseries:TagOutput");
Type conversions
An alternative to explicit unmarshalling in the DSL you can just use the
common convertBodyTo(Class) method in the DSL to convert using the
default content type to a particular ComplexDataObject from Artix DS. This
mechanism uses the inbuilt Camel Type Converter mechanism ot
automatically marshal and unmarshal using the default content type for a
model.
For example the following...
from("activemq:InputQueue").
convertBodyTo(DocumentElement.class).
to("mqseries:OutputQueue");
Is equivalent to this
from("activemq:InputQueue").
unmarshal().artixDS(DocumentElement.class).
to("mqseries:OutputQueue");
Using Transformations
To use the Message Translator pattern with ADS its a simple matter of using
the ADS tooling to create your transformation, then just using the generated
transformation class in the Bean Integration in Camel.
For example image you define a transformation in the ADS IDE to translate
SWIFT to FIX format. You will then have a generated SwiftToFix Java class. You
can then use the transformation in your Camel DSL via Java or the Xml
Configuration as follows
from("activemq:SwiftQueue").
bean(SwiftToFix.class).
to("mqseries:FixQueue");
D ATA F O R M AT A PPE NDIX
278
Configuring via Spring XML
The following example shows how to use Artix DS using Spring XML; in this
case it unmarshals the content of a JMS queue as XML using the Artix DS
data model; then marshals it using a tag/value pair.
<camelContext id="camel" xmlns="http://activemq.apache.org/camel/schema/spring">
<route>
<from uri="activemq:MyInputQueue"/>
<unmarshal>
<artixDS contentType="Xml"
elementTypeName="iso.std.iso.x20022.tech.xsd.pacs.x008.x001.x01.DocumentElement"/>
</unmarshal>
<marshal>
<artixDS contentType="TagValuePair"/>
</marshal>
<to uri="mqseries:MyOutputQueue"/>
</route>
</camelContext>
Content Types and auto discovery
You may have spotted in the above that we use the ArtixDSContentType
which is an enum in Java and the Xml Configuration to describe the kind of
XML format to use such as binary, XML, Text etc.
If no content type is specified we always use the default content type of
the Artix DS model in question. This is equivalent to the Default content
type.
If you wish to be flexible in what you accept or emit, we also support the
Auto content type which will look for the Content-Type header on the input
message and use that to try determine which of the content types to use; if
none can be found then Default is used.
e.g. you could support content posted with a MIME type of application/
xml to indicate XML or application/x-java-serialized-object for
serialization or text/plain for text etc.
Using camel-artixds
To use this module you need to use the FUSE Mediation Router distribution.
Or you could just add the following to your pom.xml, substituting the version
number for the latest & greatest release.
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-artixds</artifactId>
279
D ATA F O R MAT A P P E N D I X
<version>1.5.3.0-fuse</version>
</dependency>
And ensure you are pointing at the maven repo
<repository>
<id>open.iona.m2</id>
<name>FUSESource Open Source Community Release Repository</name>
<url>http://repo.fusesource.com/maven2/</url>
<snapshots>
<enabled>false</enabled>
</snapshots>
<releases>
<enabled>true</enabled>
</releases>
</repository>
SERIALIZATION
Serialization is a Data Format which uses the standard Java Serialization
mechanism to unmarshal a binary payload into Java objects or to marshal
Java objects into a binary blob.
For example the following uses Java serialization to unmarshal a binary file
then send it as an ObjectMessage to ActiveMQ
from("file://foo/bar").
unmarshal().serialization().
to("activemq:Some.Queue");
Dependencies
This data format is provided in camel-core so no additional dependencies is
needed.
JAXB
JAXB is a Data Format which uses the JAXB2 XML marshalling standard which
is included in Java 6 to unmarshal an XML payload into Java objects or to
marshal Java objects into an XML payload.
D ATA F O R M AT A PPE NDIX
280
Using the Java DSL
For example the following uses a named DataFormat of jaxb which is
configured with a number of Java package names to initialize the
JAXBContext.
DataFormat jaxb = new JaxbDataFormat("com.acme.model");
from("activemq:My.Queue").
unmarshal(jaxb).
to("mqseries:Another.Queue");
You can if you prefer use a named reference to a data format which can then
be defined in your Registry such as via your Spring XML file. e.g.
from("activemq:My.Queue").
unmarshal("myJaxbDataType").
to("mqseries:Another.Queue");
Using Spring XML
The following example shows how to use JAXB to unmarshal using Spring
configuring the jaxb data type
<camelContext id="camel" xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="direct:start"/>
<unmarshal>
<jaxb prettyPrint="true" contextPath="org.apache.camel.example"/>
</unmarshal>
<to uri="mock:result"/>
</route>
</camelContext>
This example shows how to configure the data type just once and reuse it on
multiple routes. For Camel versions below 1.5.0 you have to set the <jaxb>
element directly in <camelContext>.
<camelContext id="camel" xmlns="http://camel.apache.org/schema/spring">
<dataFormats>
<jaxb id="myJaxb" prettyPrint="true" contextPath="org.apache.camel.example"/>
</dataFormats>
<route>
<from uri="direct:start"/>
<marshal ref="myJaxb"/>
<to uri="direct:marshalled"/>
281
D ATA F O R MAT A P P E N D I X
</route>
<route>
<from uri="direct:marshalled"/>
<unmarshal ref="myJaxb"/>
<to uri="mock:result"/>
</route>
</camelContext>
Partial marshalling/unmarshalling
This feature is new to Camel 2.2.0.
JAXB 2 supports marshalling and unmarshalling XML tree fragments. By
default JAXB looks for @XmlRootElement annotation on given class to operate
on whole XML tree. This is useful but not always - sometimes generated code
does not have @XmlRootElement annotation, sometimes you need
unmarshall only part of tree.
In that case you can use partial unmarshalling. To enable this behaviours you
need set property partClass. Camel will pass this class to JAXB's
unmarshaler.
<camelContext id="camel" xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="direct:marshal"/>
<marshal>
<jaxb prettyPrint="false" contextPath="org.apache.camel.example"
partClass="org.apache.camel.example.PurchaseOrder"
partNamespace="{http://example.camel.org/apache}po" />
</marshal>
<to uri="mock:marshal"/>
</route>
<route>
<from uri="direct:unmarshal"/>
<unmarshal>
<jaxb prettyPrint="false" contextPath="org.apache.camel.example"
partClass="org.apache.camel.example.Partial" />
</unmarshal>
<to uri="mock:unmarshal"/>
</route>
</camelContext>
For marshalling you have to add partNamespace attribute with QName of
destination namespace. Example of Spring DSL you can find above.
D ATA F O R M AT A PPE NDIX
282
Multiple context paths
It is possible to use this data format with more than one context
path. You can specify context path using : as separator, for
example com.mycompany:com.mycompany2. Note that this is
handled by JAXB implementation and might change if you use
different vendor than RI.
Ignoring the NonXML Character
This feature is new to Camel 2.2.0.
JaxbDataFromat supports to ignore the NonXML Character, you just need to
set the filterNonXmlChars property to be true, JaxbDataFromat will replace
the NonXML character with " " when it is marshaling or unmarshaling the
message. You can also do it by setting the Exchange property
Exchange.FILTER_NON_XML_CHARS.
Â
JDK 1.5
JDK 1.6+
Filtering in use
StAX API and implementation
No
Filtering not in use
StAX API only
No
This feature has been tested with Woodstox 3.2.9 and Sun JDK 1.6 StAX
implementation.
Working with the ObjectFactory
If you use XJC to create the java class from the schema, you will get an
ObjectFactory for you JAXB context. Since the ObjectFactory uses
JAXBElement to hold the reference of the schema and element instance
value, from Camel 1.5.1 jaxbDataformat will ignore the JAXBElement by
default and you will get the element instance value instead of the
JAXBElement object form the unmarshaled message body.
If you want to get the JAXBElement object form the unmarshaled message
body, you need to set the JaxbDataFormat object's ignoreJAXBElement
property to be false.
Setting encoding
In Camel 1.6.1 and newer you can set the encoding option to use when
marshalling. Its the Marshaller.JAXB_ENCODING encoding property on the
JAXB Marshaller.
You can setup which encoding to use when you declare the JAXB data format.
You can also provide the encoding in the Exchange property
283
D ATA F O R MAT A P P E N D I X
Exchange.CHARSET_NAME. This property will overrule the encoding set on the
JAXB data format.
In this Spring DSL we have defined to use iso-8859-1 as the encoding:
<camelContext id="camel" xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="direct:start"/>
<marshal>
<jaxb prettyPrint="false" encoding="iso-8859-1"
contextPath="org.apache.camel.example"/>
</marshal>
<to uri="mock:result"/>
</route>
</camelContext>
Dependencies
To use JAXB in your camel routes you need to add the a dependency on
camel-jaxb which implements this data format.
If you use maven you could just add the following to your pom.xml,
substituting the version number for the latest & greatest release (see the
download page for the latest versions).
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-jaxb</artifactId>
<version>1.6.0</version>
</dependency>
XMLBEANS
XmlBeans is a Data Format which uses the XmlBeans library to unmarshal an
XML payload into Java objects or to marshal Java objects into an XML
payload.
from("activemq:My.Queue").
unmarshal().xmlBeans().
to("mqseries:Another.Queue");
Dependencies
To use XmlBeans in your camel routes you need to add the a dependency on
camel-xmlbeans which implements this data format.
D ATA F O R M AT A PPE NDIX
284
If you use maven you could just add the following to your pom.xml,
substituting the version number for the latest & greatest release (see the
download page for the latest versions).
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-xmlbeans</artifactId>
<version>1.5.0</version>
</dependency>
XSTREAM
XStream is a Data Format which uses the XStream library to marshal and
unmarshal Java objects to and from XML.
// lets turn Object messages into XML then send to MQSeries
from("activemq:My.Queue").
marshal().xstream().
to("mqseries:Another.Queue");
XMLInputFactory and XMLOutputFactory
The XStream library uses the javax.xml.stream.XMLInputFactory and
javax.xml.stream.XMLOutputFactory, you can control which
implementation of this factory should be used.
The Factory is discovered using this algorithm:
1. Use the javax.xml.stream.XMLInputFactory ,
javax.xml.stream.XMLOutputFactory system property.
2. Use the lib/xml.stream.properties file in the JRE_HOME directory.
3. Use the Services API, if available, to determine the classname by looking in
the META-INF/services/javax.xml.stream.XMLInputFactory, META-INF/
services/javax.xml.stream.XMLOutputFactory files in jars available to
the JRE.
4. Use the platform default XMLInputFactory,XMLOutputFactory instance.
How to set the XML encoding in Xstream DataFormat?
From Camel 1.6.3 or Camel 2.2.0, you can set the encoding of XML in
Xstream DataFormat by setting the Exchange's property with the key
Exchange.CHARSET_NAME, or setting the encoding property on Xstream from
DSL or Spring config.
285
D ATA F O R MAT A P P E N D I X
from("activemq:My.Queue").
marshal().xstream("UTF-8").
to("mqseries:Another.Queue");
<camelContext id="camel" xmlns="http://camel.apache.org/schema/spring">
<!-- we define the json xstream data formats to be used (xstream is default) -->
<dataFormats>
<xstream id="xstream-utf8" encoding="UTF-8"/>
<xstream id="xstream-default"/>
</dataFormats>
<route>
<from uri="direct:in"/>
<marshal ref="xstream-default"/>
<to uri="mock:result"/>
</route>
<route>
<from uri="direct:in-UTF-8"/>
<marshal ref="xstream-utf8"/>
<to uri="mock:result"/>
</route>
</camelContext>
Dependencies
To use XStream in your camel routes you need to add the a dependency on
camel-xstream which implements this data format.
If you use maven you could just add the following to your pom.xml,
substituting the version number for the latest & greatest release (see the
download page for the latest versions).
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-xstream</artifactId>
<version>1.5.0</version>
</dependency>
CSV
The CSV Data Format uses Apache Commons CSV to handle CSV payloads
(Comma Separated Values) such as those exported/imported by Excel.
D ATA F O R M AT A PPE NDIX
286
Options
Option
Type
Description
config
CSVConfig
Can be used to set a custom CSVConfig
object.
strategy
CSVStrategy
Camel uses by default
CSVStrategy.DEFAULT_STRATEGY.
autogenColumn
boolean
Camel 1.6.1/2.0: Is default true. By
default, columns are autogenerated in
the resulting CSV. Subsequent messages
use the previously created columns with
new fields being added at the end of the
line.
delimiter
String
Camel 2.4: Is default ,. Can be used to
configure the delimiter, if it's not the
comma.
Marshalling a Map to CSV
The component allows you to marshal a Java Map (or any other message
type that can be converted in a Map) into a CSV payload.
An example: if you send a message with this map...
Map<String, Object> body = new HashMap<String, Object>();
body.put("foo", "abc");
body.put("bar", 123);
... through this route ...
from("direct:start").
marshal().csv().
to("mock:result");
... you will end up with a String containing this CSV message
abc,123
Sending the Map below through this route will result in a CSV message that
looks like foo,bar
287
D ATA F O R MAT A P P E N D I X
Unmarshalling a CSV message into a Java List
Unmarshalling will transform a CSV messsage into a Java List with CSV file
lines (containing another List with all the field values).
An example: we have a CSV file with names of persons, their IQ and their
current activity.
Jack Dalton, 115, mad at Averell
Joe Dalton, 105, calming Joe
William Dalton, 105, keeping Joe from killing Averell
Averell Dalton, 80, playing with Rantanplan
Lucky Luke, 120, capturing the Daltons
We can now use the CSV component to unmarshal this file:
from("file:src/test/resources/?fileName=daltons.csv&noop=true").
unmarshal().csv().
to("mock:daltons");
The resulting message will contain a List<List<String>> like...
List<List<String>> data = (List<List<String>>) exchange.getIn().getBody();
for (List<String> line : data) {
LOG.debug(String.format("%s has an IQ of %s and is currently %s",
line.get(0), line.get(1), line.get(2)));
}
Marshalling a List<Map> to CSV
Available as of Camel 2.1
If you have multiple rows of data you want to be marshalled into CSV
format you can now store the message payload as a List<Map<String,
Object>> object where the list contains a Map for each row.
File Poller of CSV, then unmarshaling
Given a bean which can handle the incoming data...
Listing 22. MyCsvHandler.java
// Some comments here
public void doHandleCsvData(List<List<String>> csvData)
{
// do magic here
}
... your route then looks as follows
D ATA F O R M AT A PPE NDIX
288
<route>
<!-- poll every 10 seconds -->
<from uri="file:///some/path/to/pickup/
csvfiles?delete=true&amp;consumer.delay=10000" />
<unmarshal><csv /></unmarshal>
<to uri="bean:myCsvHandler?method=doHandleCsvData" />
</route>
Marshaling with a pipe as delimiter
Using the Spring/XML DSL:
<route>
<from uri="direct:start" />
<marshal>
<csv delimiter="|" />
</marshal>
<to uri="bean:myCsvHandler?method=doHandleCsv" />
</route>
Or the Java DSL:
CsvDataFormat csv = new CsvDataFormat();
CSVConfig config = new CSVConfig();
config.setDelimiter('|');
csv.setConfig(config);
from("direct:start")
.marshal(csv)
.convertBodyTo(String.class)
.to("bean:myCsvHandler?method=doHandleCsv");
CsvDataFormat csv = new CsvDataFormat();
csv.setDelimiter("|");
from("direct:start")
.marshal(csv)
.convertBodyTo(String.class)
.to("bean:myCsvHandler?method=doHandleCsv");
Unmarshaling with a pipe as delimiter
Using the Spring/XML DSL:
289
D ATA F O R MAT A P P E N D I X
<route>
<from uri="direct:start" />
<unmarshal>
<csv delimiter="|" />
</unmarshal>
<to uri="bean:myCsvHandler?method=doHandleCsv" />
</route>
Or the Java DSL:
CsvDataFormat csv = new CsvDataFormat();
CSVStrategy strategy = CSVStrategy.DEFAULT_STRATEGY;
strategy.setDelimiter('|');
csv.setStrategy(strategy);
from("direct:start")
.unmarshal(csv)
.to("bean:myCsvHandler?method=doHandleCsv");
CsvDataFormat csv = new CsvDataFormat();
csv.setDelimiter("|");
from("direct:start")
.unmarshal(csv)
.to("bean:myCsvHandler?method=doHandleCsv");
Dependencies
To use CSV in your camel routes you need to add the a dependency on
camel-csv which implements this data format.
If you use maven you could just add the following to your pom.xml,
substituting the version number for the latest & greatest release (see the
download page for the latest versions).
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-csv</artifactId>
<version>2.0.0</version>
</dependency>
The String Data Format is a textual based format that supports encoding.
Options
Option
Default
Description
D ATA F O R M AT A PPE NDIX
290
charset
null
To use a specific charset for encoding. If not provided
Camel will use the JVM default charset.
Marshal
In this example we marshal the file content to String object in UTF-8
encoding.
from("file://data.csv").marshal().string("UTF-8").to("jms://myqueue");
Unmarshal
In this example we unmarshal the payload from the JMS queue to a String
object using UTF-8 encoding, before its processed by the newOrder
processor.
from("jms://queue/order").unmarshal().string("UTF-8").processRef("newOrder");
Dependencies
This data format is provided in camel-core so no additional dependencies is
needed.
HL7 DataFormat
The HL7 component ships with a HL7 data format that can be used to format
between String and HL7 model objects.
▪ marshal = from Message to byte stream (can be used when
returning as response using the HL7 MLLP codec)
▪ unmarshal = from byte stream to Message (can be used when
receiving streamed data from the HL7 MLLP
To use the data format, simply instantiate an instance and invoke the
marhsal or unmarshl operation in the route builder:
DataFormat hl7 = new HL7DataFormat();
...
from("direct:hl7in").marshal(hl7).to("jms:queue:hl7out");
In the sample above, the HL7 is marshalled from a HAPI Message object to a
byte stream and put on a JMS queue.
The next example is the opposite:
291
D ATA F O R MAT A P P E N D I X
DataFormat hl7 = new HL7DataFormat();
...
from("jms:queue:hl7out").unmarshal(hl7).to("patientLookupService");
Here we unmarshal the byte stream into a HAPI Message object that is
passed to our patient lookup service.
Notice there is a shorthand syntax in Camel for well-known data formats
that is commonly used.
Then you don't need to create an instance of the HL7DataFormat object:
from("direct:hl7in").marshal().hl7().to("jms:queue:hl7out");
from("jms:queue:hl7out").unmarshal().hl7().to("patientLookupService");
EDI DATAFORMAT
We encourage end users to look at the Smooks which supports EDI and
Camel natively.
FLATPACK DATAFORMAT
The Flatpack component ships with the Flatpack data format that can be
used to format between fixed width or delimited text messages to a List of
rows as Map.
▪ marshal = from List<Map<String, Object>> to OutputStream (can
be converted to String)
▪ unmarshal = from java.io.InputStream (such as a File or String)
to a java.util.List as an
org.apache.camel.component.flatpack.DataSetList instance.
The result of the operation will contain all the data. If you need to
process each row one by one you can split the exchange, using
Splitter.
Notice: The Flatpack library does currently not support header and trailers
for the marshal operation.
Options
The data format has the following options:
Option
Default
Description
D ATA F O R M AT A PPE NDIX
292
definition
null
The flatpack pzmap configuration file.
Can be omitted in simpler situations, but
its preferred to use the pzmap.
fixed
false
Delimited or fixed.
ignoreFirstRecord
true
Whether the first line is ignored for
delimited files (for the column headers).
textQualifier
"
If the text is qualified with a char such as
".
delimiter
,
The delimiter char (could be ; , or
similar)
parserFactory
null
Uses the default Flatpack parser factory.
Usage
To use the data format, simply instantiate an instance and invoke the
marhsal or unmarshal operation in the route builder:
FlatpackDataFormat fp = new FlatpackDataFormat();
fp.setDefinition(new ClassPathResource("INVENTORY-Delimited.pzmap.xml"));
...
from("file:order/in").unmarshal(df).to("seda:queue:neworder");
The sample above will read files from the order/in folder and unmarshal the
input using the Flatpack configuration file INVENTORY-Delimited.pzmap.xml
that configures the structure of the files. The result is a DataSetList object
we store on the SEDA queue.
FlatpackDataFormat df = new FlatpackDataFormat();
df.setDefinition(new ClassPathResource("PEOPLE-FixedLength.pzmap.xml"));
df.setFixed(true);
df.setIgnoreFirstRecord(false);
from("seda:people").marshal(df).convertBodyTo(String.class).to("jms:queue:people");
In the code above we marshal the data from a Object representation as a
List of rows as Maps. The rows as Map contains the column name as the key,
and the the corresponding value. This structure can be created in Java code
from e.g. a processor. We marshal the data according to the Flatpack format
and convert the result as a String object and store it on a JMS queue.
293
D ATA F O R MAT A P P E N D I X
Dependencies
To use Flatpack in your camel routes you need to add the a dependency on
camel-flatpack which implements this data format.
If you use maven you could just add the following to your pom.xml,
substituting the version number for the latest & greatest release (see the
download page for the latest versions).
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-flatpack</artifactId>
<version>1.5.0</version>
</dependency>
JSON
JSON is a Data Format to marshal and unmarshal Java objects to and from
JSON.
In Camel 1.6 its only the XStream library that is supported and its default.
In Camel 2.0 we added support for more libraries:
Camel provides integration with two popular JSon libraries:
▪ The XStream library and Jettsion
▪ The Jackson library
By default Camel uses the XStream library.
Using JSon data format with the XStream library
// lets turn Object messages into json then send to MQSeries
from("activemq:My.Queue").
marshal().json().
to("mqseries:Another.Queue");
Using Json data format with the Jackson library
// lets turn Object messages into json then send to MQSeries
from("activemq:My.Queue").
marshal().json(JsonLibrary.Jackson).
to("mqseries:Another.Queue");
D ATA F O R M AT A PPE NDIX
294
Using Json in Spring DSL
When using Data Format in Spring DSL you need to declare the data formats
first. This is done in the DataFormats XML tag.
<dataFormats>
<!-- here we define a Json data format with the id jack and that it
should use the TestPojo as the class type when
doing unmarshal. The unmarshalTypeName is optional, if not provided
Camel will use a Map as the type -->
<json id="jack" library="Jackson"
unmarshalTypeName="org.apache.camel.component.jackson.TestPojo"/>
</dataFormats>
And then you can refer to this id in the route:
<route>
<from uri="direct:back"/>
<unmarshal ref="jack"/>
<to uri="mock:reverse"/>
</route>
Dependencies for XStream
To use JSON in your camel routes you need to add the a dependency on
camel-xstream which implements this data format.
If you use maven you could just add the following to your pom.xml,
substituting the version number for the latest & greatest release (see the
download page for the latest versions).
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-xstream</artifactId>
<version>2.0</version>
</dependency>
Dependencies for Jackson
To use JSON in your camel routes you need to add the a dependency on
camel-jackson which implements this data format.
If you use maven you could just add the following to your pom.xml,
substituting the version number for the latest & greatest release (see the
download page for the latest versions).
295
D ATA F O R MAT A P P E N D I X
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-jackson</artifactId>
<version>2.0</version>
</dependency>
The Zip Data Format is a message compression and de-compression format.
Messages marshalled using Zip compression can be unmarshalled using Zip
decompression just prior to being consumed at the endpoint. The
compression capability is quite useful when you deal with large XML and Text
based payloads. It facilitates more optimal use of network bandwidth while
incurring a small cost in order to compress and decompress payloads at the
endpoint.
Options
Option
compressionLevel
Default
null
Description
To specify a specific compression Level use
java.util.zip.Deflater settings. The
possible settings areÂ
         - Deflater.BEST_SPEED
ÂÂÂÂÂÂÂÂÂ Deflater.BEST_COMPRESSION
ÂÂÂÂÂÂÂÂÂ Deflater.DEFAULT_COMPRESSION
If compressionLevel is not explicitly
specified the compressionLevel employed is
Deflater.DEFAULT_COMPRESSION
Marshal
In this example we marshal a regular text/XML payload to a compressed
payload employing zip compression Deflater.BEST_COMPRESSION and send
it an ActiveMQ queue called MY_QUEUE.
from("direct:start").marshal().zip(Deflater.BEST_COMPRESSION).to("activemq:queue:MY_QUEUE");
Alternatively if you would like to use the default setting you could send it as
from("direct:start").marshal().zip().to("activemq:queue:MY_QUEUE");
D ATA F O R M AT A PPE NDIX
296
Unmarshal
In this example we unmarshal a zipped payload from an ActiveMQ queue
called MY_QUEUE to its original format, and forward it for processing to
the UnZippedMessageProcessor. Note that the compression Level employed
during the marshalling should be identical to the one employed during
unmarshalling to avoid errors.
from("activemq:queue:MY_QUEUE").unmarshal().zip().process(new
UnZippedMessageProcessor());Â
Dependencies
This data format is provided in camel-core so no additional dependencies is
needed.
TIDYMARKUP
TidyMarkup is a Data Format that uses the TagSoup to tidy up HTML. It can be
used to parse ugly HTML and return it as pretty wellformed HTML.
TidyMarkup only supports the unmarshal operation as we really don't want
to turn well formed HTML into ugly HTML
Java DSL Example
An example where the consumer provides some HTML
from("file://site/inbox").unmarshal().tidyMarkup().to("file://site/blogs");
Spring XML Example
The following example shows how to use TidyMarkup to unmarshal using
Spring
<camelContext id="camel" xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="file://site/inbox"/>
<unmarshal>
<tidyMarkup/>
</unmarshal>
<to uri="file://site/blogs"/>
</route>
</camelContext>
297
D ATA F O R MAT A P P E N D I X
Camel eats our own dog food soap
We had some issues in our pdf Manual where we had some strange
symbols. So Jonathan used this data format to tidy up the wiki html
pages that are used as base for rendering the pdf manuals. And
then the mysterious symbols vanished.
Dependencies
To use TidyMarkup in your camel routes you need to add the a dependency
on camel-tagsoup which implements this data format.
If you use maven you could just add the following to your pom.xml,
substituting the version number for the latest & greatest release (see the
download page for the latest versions).
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-tagsoup</artifactId>
<version>1.6.0</version>
</dependency>
BINDY
Available as of Camel 2.0
The idea that the developers has followed to design this component was to
allow the parsing/binding of non structured data (or to be more precise nonXML data)
to Java Bean using annotations. Using Bindy, you can bind data like :
▪ CSV record,
▪ Fixedlength record,
▪ FIX messages,
▪ or any other non-structured data
to one or many Plain Old Java Object (POJO) and to convert the data
according to the type of the java property. POJO can be linked together and
relation one to many is available in some cases. Moreover, for data type like
Date, Double, Float, Integer, Short, Long and BigDecimal, you can provide
the pattern to apply during the formatting of the property.
For the BigDecimal number, you can also define the precision and the
decimal or grouping separators
Type
Format Type
Pattern
example
Link
D ATA F O R M AT A PPE NDIX
298
Date
DateFormat
"dd-MM-yyyy"
http://java.sun.com/j2se/
1.5.0/docs/api/java/text/
SimpleDateFormat.html
Decimal*
Decimalformat
"##.###.###"
http://java.sun.com/j2se/
1.5.0/docs/api/java/text/
DecimalFormat.html
Decimal* = Double, Integer, Float, Short, Long
To work with camel-bindy, you must first define your model in a package (e.g.
com.acme.model) and for each model class (e.g. Order, Client, Instrument,
...) associate the required annotations (described hereafter) with Class or
property name.
ANNOTATIONS
The annotations created allow to map different concept of your model to the
POJO like :
▪ Type of record (csv, key value pair (e.g. FIX message), fixed length
...),
▪ Link (to link object in another object),
▪ DataField and their properties (int, type, ...),
▪ KeyValuePairField (for key = value format like we have in FIX financial
messages),
▪ Section (to identify header, body and footer section),
▪ OneToMany
This section will describe them :
1. CsvRecord
The CsvRecord annotation is used to identified the root class of the model. It
represents a record = a line of a CSV file and can be linked to several
children model classes.
Annotation name
Record type
Level
CsvRecord
csv
Class
Parameter name
299
type
D ATA F O R MAT A P P E N D I X
Info
Format supported
This first release only support comma separated values fields and
key value pair fields (e.g. : FIX messages).
separator
string
mandatory - can be ',' or ';' or
'anything'. This value is interpreted
as a regular expression. If you want
to use a sign which has a special
meaning in regular expressions, e.g.
the '|' sign, than you have to mask it,
like '
|'
skipFirstLine
boolean
optional - default value = false allow to skip the first line of the CSV
file
crlf
string
optional - default value = WINDOWS
- allow to define the carriage return
character to use
generateHeaderColumns
boolean
optional - default value = false - uses
to generate the header columns of
the CSV generates
isOrdered
boolean
optional - default value = false allow to change the order of the
fields when CSV is generated
Â
Â
This annotation is associated to the
root class of the model and must be
declared one time.
case 1 : separator = ','
The separator used to segregate the fields in the CSV record is ',' :
10, J, Pauline, M, XD12345678, Fortis Dynamic 15/15, 2500,
USD,08-01-2009
Listing 23. Separator ,
@CsvRecord( separator = "," )
public Class Order {
...
}
case 2 : separator = ';'
D ATA F O R M AT A PPE NDIX
300
Compare to the previous case, the separator here is ';' instead of ',' :
10; J; Pauline; M; XD12345678; Fortis Dynamic 15/15; 2500; USD;
08-01-2009
Listing 24. Separator ;
@CsvRecord( separator = ";" )
public Class Order {
...
}
case 3 : separator = '|'
Compare to the previous case, the separator here is '|' instead of ';' :
10| J| Pauline| M| XD12345678| Fortis Dynamic 15/15| 2500| USD|
08-01-2009
Listing 25. Separator
@CsvRecord( separator = "\\|" )
public Class Order {
...
}
case 3 : separator = '\",\"'
When the field to be parsed of the CSV record contains ',' or ';' which is
also used as separator, we whould find another strategy
to tell camel bindy how to handle this case. To define the field containing the
data with a comma, you will use simple or double quotes
as delimiter (e.g : '10', 'Street 10, NY', 'USA' or "10", "Street 10, NY", "USA").
Remark : In this case, the first and last character of the line which are a
simple or double quotes will removed by bindy
"10","J","Pauline"," M","XD12345678","Fortis Dynamic 15,15"
2500","USD","08-01-2009"
Listing 26. Separator ""
@CsvRecord( separator = "\",\"" )
public Class Order {
...
}
case 5 : separator & skipfirstline
The feature is interesting when the client wants to have in the first line of
the file, the name of the data fields :
order id, client id, first name, last name, isin code, instrument name,
quantity, currency, date
301
D ATA F O R MAT A P P E N D I X
To inform bindy that this first line must be skipped during the parsing
process, then we use the attribute :
Listing 27. Separator & skipFirstLine
@CsvRecord(separator = ",", skipFirstLine = true)
public Class Order {
...
}
case 6 : generateHeaderColumns
To add at the first line of the CSV generated, the attribute
generateHeaderColumns must be set to true in the annotation like this :
Listing 28. generateHeaderColumns
@CsvRecord( generateHeaderColumns = true )
public Class Order {
...
}
As a result, Bindy during the unmarshaling process will generate CSV like this
:
order id, client id, first name, last name, isin code, instrument name,
quantity, currency, date
10, J, Pauline, M, XD12345678, Fortis Dynamic 15/15, 2500, USD,08-01-2009
case 7 : carriage return
If the platform where camel-bindy will run is not Windows but Macintosh or
Unix, than you can change the crlf property like this. Three values are
available : WINDOWS, UNIX or MAC
Listing 29. carriage return
@CsvRecord(separator = ",", crlf="MAC")
public Class Order {
...
}
case 8 : isOrdered
Sometimes, the order to follow during the creation of the CSV record from
the model is different from the order used during the parsing. Then, in this
case, we can use the attribute isOrdered = true to indicate this in
combination with attribute 'position' of the DataField annotation.
Listing 30. isOrdered
@CsvRecord(isOrdered = true)
public Class Order {
D ATA F O R M AT A PPE NDIX
302
@DataField(pos = 1, position = 11)
private int orderNr;
@DataField(pos = 2, position = 10)
private String clientNr;
...
}
Remark : pos is used to parse the file, stream while positions is used to
generate the CSV
2. Link
The link annotation will allow to link objects together.
Annotation name
Record type
Level
Link
all
Class & Property
Parameter
name
type
Info
linkType
LinkType
optional - by default the value is
LinkType.oneToOne - so you are not obliged to
mention it
Â
Â
Only one-to-one relation is allowed.
e.g : If the model Class Client is linked to the Order class, then use
annotation Link in the Order class like this :
Listing 31. Property Link
@CsvRecord(separator = ",")
public class Order {
@DataField(pos = 1)
private int orderNr;
@Link
private Client client;
...
AND for the class Client :
Listing 32. Class Link
@Link
public class Client {
303
D ATA F O R MAT A P P E N D I X
...
}
3. DataField
The DataField annotation defines the property of the field. Each datafield is
identified by its position in the record, a type (string, int, date, ...) and
optionally of a pattern
Annotation name
Record type
Level
DataField
all
Property
Parameter
name
type
Info
pos
int
mandatory - digit number starting from 1 to ...
pattern
string
optional - default value = "" - will be used to
format Decimal, Date, ...
length
int
optional - represents the length of the field for
fixed length format
precision
int
optional - represents the precision to be used
when the Decimal number will be formatted/
parsed
pattern
string
optional - default value = "" - is used by the Java
Formater (SimpleDateFormat by example) to
format/validate data
position
int
optional - must be used when the position of the
field in the CSV generated must be different
compare to pos
required
boolean
optional - default value = "false"
trim
boolean
optional - default value = "false"
case 1 : pos
This parameter/attribute represents the position of the field in the csv
record
Listing 33. Position
@CsvRecord(separator = ",")
public class Order {
D ATA F O R M AT A PPE NDIX
304
@DataField(pos = 1)
private int orderNr;
@DataField(pos = 5)
private String isinCode;
...
}
As you can see in this example the position starts at '1' but continues at '5' in
the class Order. The numbers from '2' to '4' are defined in the class Client
(see here after).
Listing 34. Position continues in another model class
public class Client {
@DataField(pos = 2)
private String clientNr;
@DataField(pos = 3)
private String firstName;
@DataField(pos = 4)
private String lastName;
...
}
case 2 : pattern
The pattern allows to enrich or validates the format of your data
Listing 35. Pattern
@CsvRecord(separator = ",")
public class Order {
@DataField(pos = 1)
private int orderNr;
@DataField(pos = 5)
private String isinCode;
@DataField(name = "Name", pos = 6)
private String instrumentName;
@DataField(pos = 7, precision = 2)
private BigDecimal amount;
@DataField(pos = 8)
private String currency;
@DataField(pos = 9, pattern = "dd-MM-yyyy") -- pattern used during parsing or
305
D ATA F O R MAT A P P E N D I X
when the date is created
private Date orderDate;
...
}
case 3 : precision
The precision is helpful when you want to define the decimal part of your
number
Listing 36. Precision
@CsvRecord(separator = ",")
public class Order {
@DataField(pos = 1)
private int orderNr;
@Link
private Client client;
@DataField(pos = 5)
private String isinCode;
@DataField(name = "Name", pos = 6)
private String instrumentName;
@DataField(pos = 7, precision = 2) -- precision
private BigDecimal amount;
@DataField(pos = 8)
private String currency;
@DataField(pos = 9, pattern = "dd-MM-yyyy")
private Date orderDate;
...
}
case 4 : Position is different in output
The position attribute will inform bindy how to place the field in the CSV
record generated. By default, the position used corresponds to the position
defined with the attribute 'pos'. If the position is different (that means that
we have an asymetric processus comparing marshaling from unmarshaling)
than we can use 'position' to indicate this.
Here is an example
Listing 37. Position is different in output
@CsvRecord(separator = ",")
public class Order {
@CsvRecord(separator = ",", isOrdered = true)
D ATA F O R M AT A PPE NDIX
306
public class Order {
// Positions of the fields start from 1 and not from 0
@DataField(pos = 1, position = 11)
private int orderNr;
@DataField(pos = 2, position = 10)
private String clientNr;
@DataField(pos = 3, position = 9)
private String firstName;
@DataField(pos = 4, position = 8)
private String lastName;
@DataField(pos = 5, position = 7)
private String instrumentCode;
@DataField(pos = 6, position = 6)
private String instrumentNumber;
...
}
case 5 : required
If a field is mandatory, simply use the attribute 'required' setted to true
Listing 38. Required
@CsvRecord(separator = ",")
public class Order {
@DataField(pos = 1)
private int orderNr;
@DataField(pos = 2, required = true)
private String clientNr;
@DataField(pos = 3, required = true)
private String firstName;
@DataField(pos = 4, required = true)
private String lastName;
...
}
If this field is not present in the record, than an error will be raised by the
parser with the following information :
Some fields are missing (optional or mandatory), line :
case 6 : trim
307
D ATA F O R MAT A P P E N D I X
This attribute of the annotation @DataField must be used in
combination with attribute isOrdered = true of the annotation
@CsvRecord
If a field has leading and/or trailing spaces which should be removed
before they are processed, simply use the attribute 'trim' setted to true
Listing 39. Trim
@CsvRecord(separator = ",")
public class Order {
@DataField(pos = 1, trim = true)
private int orderNr;
@DataField(pos = 2, trim = true)
private Integer clientNr;
@DataField(pos = 3, required = true)
private String firstName;
@DataField(pos = 4)
private String lastName;
...
}
4. FixedLengthRecord
The FixedLengthRecord annotation is used to identified the root class of the
model. It represents a record = a line of a file/message containing data fixed
length formatted
and can be linked to several children model classes. This format is a bit
particular beause data of a field can be aligned to the right or to the left.
When the size of the data does not fill completely the length of the field, then
we add 'padd' characters.
Annotation name
Record type
Level
FixedLengthRecord
fixed
Class
Parameter
name
type
Info
crlf
string
optional - default value = WINDOWS - allow to
define the carriage return character to use
paddingChar
char
mandatory - default value = ' '
D ATA F O R M AT A PPE NDIX
308
length
int
mandatory = size of the fixed length record
hasHeader
boolean
optional - NOT YET IMPLEMENTED
hasFooter
boolean
optional - NOT YET IMPLEMENTED
Â
Â
This annotation is associated to the root class of
the model and must be declared one time.
case 1 : Simple fixed length record
This simple example shows how to design the model to parse/format a
fixed message
10A9PaulineMISINXD12345678BUYShare2500.45USD01-08-2009
Listing 40. Fixed-simple
@FixedLengthRecord(length=54, paddingChar=' ')
public static class Order {
@DataField(pos = 1, length=2)
private int orderNr;
@DataField(pos = 3, length=2)
private String clientNr;
@DataField(pos = 5, length=7)
private String firstName;
@DataField(pos = 12, length=1, align="L")
private String lastName;
@DataField(pos = 13, length=4)
private String instrumentCode;
@DataField(pos = 17, length=10)
private String instrumentNumber;
@DataField(pos = 27, length=3)
private String orderType;
@DataField(pos = 30, length=5)
private String instrumentType;
@DataField(pos = 35, precision = 2, length=7)
private BigDecimal amount;
@DataField(pos = 42, length=3)
private String currency;
@DataField(pos = 45, length=10, pattern = "dd-MM-yyyy")
private Date orderDate;
...
case 2 : Fixed length record with alignment and padding
309
D ATA F O R MAT A P P E N D I X
This more elaborated example show how to define the alignment for a
field and how to assign a padding character which is ' ' here''
10A9 PaulineM ISINXD12345678BUYShare2500.45USD01-08-2009
Listing 41. Fixed-padding-align
@FixedLengthRecord(length=60, paddingChar=' ')
public static class Order {
@DataField(pos = 1, length=2)
private int orderNr;
@DataField(pos = 3, length=2)
private String clientNr;
@DataField(pos = 5, length=9)
private String firstName;
@DataField(pos = 14, length=5, align="L")
the block
private String lastName;
// align text to the LEFT zone of
@DataField(pos = 19, length=4)
private String instrumentCode;
@DataField(pos = 23, length=10)
private String instrumentNumber;
@DataField(pos = 33, length=3)
private String orderType;
@DataField(pos = 36, length=5)
private String instrumentType;
@DataField(pos = 41, precision = 2, length=7)
private BigDecimal amount;
@DataField(pos = 48, length=3)
private String currency;
@DataField(pos = 51, length=10, pattern = "dd-MM-yyyy")
private Date orderDate;
...
case 3 : Field padding
Sometimes, the default padding defined for record cannnot be applied to
the field as we have a number format where we would like to padd with '0'
instead of ' '. In this case, you can use in the model the attribute
paddingField to set this value.
10A9 PaulineM ISINXD12345678BUYShare000002500.45USD01-08-2009
Listing 42. Fixed-padding-field
D ATA F O R M AT A PPE NDIX
310
@FixedLengthRecord(length = 65, paddingChar = ' ')
public static class Order {
@DataField(pos = 1, length = 2)
private int orderNr;
@DataField(pos = 3, length = 2)
private String clientNr;
@DataField(pos = 5, length = 9)
private String firstName;
@DataField(pos = 14, length = 5, align = "L")
private String lastName;
@DataField(pos = 19, length = 4)
private String instrumentCode;
@DataField(pos = 23, length = 10)
private String instrumentNumber;
@DataField(pos = 33, length = 3)
private String orderType;
@DataField(pos = 36, length = 5)
private String instrumentType;
@DataField(pos = 41, precision = 2, length = 12, paddingChar = '0')
private BigDecimal amount;
@DataField(pos = 53, length = 3)
private String currency;
@DataField(pos = 56, length = 10, pattern = "dd-MM-yyyy")
private Date orderDate;
...
5. Message
The Message annotation is used to identified the class of your model who will
contain key value pairs fields. This kind of format is used mainly in Financial
Exchange Protocol Messages (FIX). Nevertheless, this annotation can be used
for any other format where data are identified by keys. The key pair values
are separated each other by a separator which can be a special character
like a tab delimitor (unicode representation : \u0009) or a start of heading
(unicode representation : \u0001)
311
Annotation name
Record type
Level
Message
key value pair
Class
D ATA F O R MAT A P P E N D I X
"FIX information"
More information about FIX can be found on this web site :
http://www.fixprotocol.org/. To work with FIX messages, the model
must contain a Header and Trailer classes linked to the root
message class which could be a Order class. This is not mandatory
but will be very helpful when you will use camel-bindy in
combination with camel-fix which is a Fix gateway based on
quickFix project http://www.quickfixj.org/.
Parameter name
type
Info
pairSeparator
string
mandatory - can be '=' or ';' or 'anything'
keyValuePairSeparair
string
mandatory - can be '\u0001', '\u0009',
'#' or 'anything'
crlf
string
optional - default value = WINDOWS allow to define the carriage return
character to use
type
string
optional - define the type of message
(e.g. FIX, EMX, ...)
version
string
optional - version of the message (e.g.
4.1)
isOrdered
boolean
optional - default value = false - allow to
change the order of the fields when FIX
message is generated
Â
Â
This annotation is associated to the
message class of the model and must be
declared one time.
case 1 : separator = 'u0001'
The separator used to segregate the key value pair fields in a FIX message
is the ASCII '01' character or in unicode format '\u0001'. This character must
be escaped a second time to avoid a java runtime error. Here is an example :
8=FIX.4.1 9=20 34=1 35=0 49=INVMGR 56=BRKR 1=BE.CHM.001
11=CHM0001-01 22=4 ...
and how to use the annotation
Listing 43. FIX - message
D ATA F O R M AT A PPE NDIX
312
@Message(keyValuePairSeparator = "=", pairSeparator = "\u0001", type="FIX",
version="4.1")
public class Order {
...
}
6. KeyValuePairField
The KeyValuePairField annotation defines the property of a key value pair
field. Each KeyValuePairField is identified by a tag (= key) and its value
associated, a type (string, int, date, ...), optionaly a pattern and if the field is
required
Annotation name
Record type
Level
KeyValuePairField
Key Value Pair - FIX
Property
Parameter
name
type
Info
tag
int
mandatory - digit number identifying the field in
the message - must be unique
pattern
string
optional - default value = "" - will be used to
format Decimal, Date, ...
precision
int
optional - digit number - represents the precision
to be used when the Decimal number will be
formatted/parsed
position
int
optional - must be used when the position of the
key/tag in the FIX message must be different
required
boolean
optional - default value = "false"
case 1 : tag
This parameter represents the key of the field in the message
Listing 44. FIX message - Tag
@Message(keyValuePairSeparator = "=", pairSeparator = "\u0001", type="FIX",
version="4.1")
public class Order {
@Link Header header;
@Link Trailer trailer;
@KeyValuePairField(tag = 1) // Client reference
private String Account;
313
D ATA F O R MAT A P P E N D I X
Look at test cases
The ASCII character like tab, ... cannot be displayed in WIKI page. So, have a
look to the test case of camel-bindy to see exactly how the FIX message looks
like (src\test\data\fix\fix.txt) and the Order, Trailer, Header classes
(src\test\java\org\apache\camel\dataformat\bindy\model\fix\simple\Order.java)
@KeyValuePairField(tag = 11) // Order reference
private String ClOrdId;
@KeyValuePairField(tag = 22) // Fund ID type (Sedol, ISIN, ...)
private String IDSource;
@KeyValuePairField(tag = 48) // Fund code
private String SecurityId;
@KeyValuePairField(tag = 54) // Movement type ( 1 = Buy, 2 = sell)
private String Side;
@KeyValuePairField(tag = 58) // Free text
private String Text;
...
}
case 2 : Different position in output
If the tags/keys that we will put in the FIX message must be sorted
according to a predefine order, then use the attribute 'position' of the
annotation @KeyValuePairField
Listing 45. FIX message - Tag - sort
@Message(keyValuePairSeparator = "=", pairSeparator = "\\u0001", type = "FIX",
version = "4.1", isOrdered = true)
public class Order {
@Link Header header;
@Link Trailer trailer;
@KeyValuePairField(tag = 1, position = 1) // Client reference
private String account;
@KeyValuePairField(tag = 11, position = 3) // Order reference
private String clOrdId;
...
}
D ATA F O R M AT A PPE NDIX
314
7. Section
In FIX message of fixed length records, it is common to have different
sections in the representation of the information : header, body and section.
The purpose of the annotation @Section is to inform bindy about which class
of the model represents the header (= section 1), body (= section 2) and
footer (= section 3)
Only one attribute/parameter exists for this annotation.
Annotation name
Record type
Level
Section
FIX
Class
Parameter name
type
Info
number
int
digit number identifying the section position
case 1 : Section
A. Definition of the header section
Listing 46. FIX message - Section - Header
@Section(number = 1)
public class Header {
@KeyValuePairField(tag = 8, position = 1) // Message Header
private String beginString;
@KeyValuePairField(tag = 9, position = 2) // Checksum
private int bodyLength;
...
}
B. Definition of the body section
Listing 47. FIX message - Section - Body
@Section(number = 2)
@Message(keyValuePairSeparator = "=", pairSeparator = "\\u0001", type = "FIX",
version = "4.1", isOrdered = true)
public class Order {
@Link Header header;
@Link Trailer trailer;
@KeyValuePairField(tag = 1, position = 1) // Client reference
private String account;
@KeyValuePairField(tag = 11, position = 3) // Order reference
private String clOrdId;
C. Definition of the footer section
315
D ATA F O R MAT A P P E N D I X
Listing 48. FIX message - Section - Footer
@Section(number = 3)
public class Trailer {
@KeyValuePairField(tag = 10, position = 1)
// CheckSum
private int checkSum;
public int getCheckSum() {
return checkSum;
}
8. OneToMany
The purpose of the annotation @OneToMany is to allow to work with a
List<?> field defined a POJO class or from a record containing repetitive
groups.
The relation OneToMany ONLY WORKS in the following cases :
▪ Reading a FIX message containing repetitive groups (= group of tags/
keys)
▪ Generating a CSV with repetitive data
Annotation name
Record type
Level
OneToMany
all
property
Parameter
name
type
Info
mappedTo
string
optional - string - class name associated to the type
of the List<Type of the Class>
case 1 : Generating CSV with repetitive data
Here is the CSV output that we want :
Claus,Ibsen,Camel in Action 1,2010,35
Claus,Ibsen,Camel in Action 2,2012,35
Claus,Ibsen,Camel in Action 3,2013,35
Claus,Ibsen,Camel in Action 4,2014,35
Remark : the repetitive data concern the title of the book and its
publication date while first, last name and age are common
and the classes used to modeling this. The Author class contains a List of
Book.
Listing 49. Generate CSV with repetitive data
@CsvRecord(separator=",")
D ATA F O R M AT A PPE NDIX
316
Restrictions OneToMany
Be careful, the one to many of bindy does not allow to handle
repetitions defined on several levels of the hierarchy
public class Author {
@DataField(pos = 1)
private String firstName;
@DataField(pos = 2)
private String lastName;
@OneToMany
private List<Book> books;
@DataField(pos = 5)
private String Age;
...
public class Book {
@DataField(pos = 3)
private String title;
@DataField(pos = 4)
private String year;
Very simple isn't it !!!
case 2 : Reading FIX message containing group of tags/keys
Here is the message that we would like to process in our model :
"8=FIX 4.19=2034=135=049=INVMGR56=BRKR"
"1=BE.CHM.00111=CHM0001-0158=this is a camel - bindy test"
"22=448=BE000124567854=1"
"22=548=BE000987654354=2"
"22=648=BE000999999954=3"
"10=220"
tags 22, 48 and 54 are repeated
and the code
Listing 50. Reading FIX message containing group of tags/keys
public class Order {
@Link Header header;
317
D ATA F O R MAT A P P E N D I X
@Link Trailer trailer;
@KeyValuePairField(tag = 1) // Client reference
private String account;
@KeyValuePairField(tag = 11) // Order reference
private String clOrdId;
@KeyValuePairField(tag = 58) // Free text
private String text;
@OneToMany(mappedTo =
"org.apache.camel.dataformat.bindy.model.fix.complex.onetomany.Security")
List<Security> securities;
...
public class Security {
@KeyValuePairField(tag = 22) // Fund ID type (Sedol, ISIN, ...)
private String idSource;
@KeyValuePairField(tag = 48) // Fund code
private String securityCode;
@KeyValuePairField(tag = 54) // Movement type ( 1 = Buy, 2 = sell)
private String side;
Using the Java DSL
The next step consists in instantiating the DataFormat bindy class associated
with this record type and providing Java package name(s) as parameter.
For example the following uses the class CsvBindyFormat (who correspond
to the class associated with the CSV record type) which is configured with
"com.acme.model"
package name to initialize the model objects configured in this package.
DataFormat bindy = new CsvBindyDataFormat("com.acme.model");
from("file://inbox").
unmarshal(bindy).
to("bean:handleOrder");
The Camel route will pick-up files in the inbox directory, unmarshall CSV
records in a collection of model objects and send the collection
to the bean referenced by 'handleOrder'.
D ATA F O R M AT A PPE NDIX
318
The collection is a list of Map. Each Map of the list contains the objects of
the model. Each object can be retrieve using its class name.
int count = 0;
List<Map<String, Object>> models = new ArrayList<Map<String, Object>>();
Map<String, Object> model = new HashMap<String, Object>();
models = (List<Map<String, Object>>) exchange.getIn().getBody();
Iterator<Map<String, Object>> it = models.iterator();
while(it.hasNext()){
model = it.next();
for(String key : model.keySet()) {
Object obj = model.get(key);
LOG.info("Count : " + count + ", " + obj.toString());
}
count++;
}
LOG.info("Nber of CSV records received by the csv bean : " + count);
To generate CSV records from a collection of model objects, you create the
following route :
from("bean:handleOrder")
marshal(bindy)
to("file://outbox")
You can if you prefer use a named reference to a data format which can then
be defined in your Registry such as via your Spring XML file. e.g.
from("file://inbox").
unmarshal("myBindyDataFormat").
to("bean:handleOrder");
Unit test
Here is two examples showing how to marshall or unmarshall a CSV file with
Camel
Listing 51. Marshall
package org.apache.camel.dataformat.bindy.csv;
319
D ATA F O R MAT A P P E N D I X
import
import
import
import
import
import
import
java.math.BigDecimal;
java.util.ArrayList;
java.util.Calendar;
java.util.GregorianCalendar;
java.util.HashMap;
java.util.List;
java.util.Map;
import
import
import
import
import
import
import
import
import
import
import
import
import
import
org.apache.camel.EndpointInject;
org.apache.camel.Produce;
org.apache.camel.ProducerTemplate;
org.apache.camel.builder.RouteBuilder;
org.apache.camel.component.mock.MockEndpoint;
org.apache.camel.dataformat.bindy.model.complex.twoclassesandonelink.Client;
org.apache.camel.dataformat.bindy.model.complex.twoclassesandonelink.Order;
org.apache.camel.spring.javaconfig.SingleRouteCamelConfiguration;
org.junit.Test;
org.springframework.config.java.annotation.Bean;
org.springframework.config.java.annotation.Configuration;
org.springframework.config.java.test.JavaConfigContextLoader;
org.springframework.test.context.ContextConfiguration;
org.springframework.test.context.junit4.AbstractJUnit4SpringContextTests;
@ContextConfiguration(locations =
"org.apache.camel.dataformat.bindy.csv.BindyComplexCsvMarshallTest$ContextConfig",
loader = JavaConfigContextLoader.class)
public class BindyComplexCsvMarshallTest extends AbstractJUnit4SpringContextTests {
private List<Map<String, Object>> models = new ArrayList<Map<String, Object>>();
private String result = "10,A1,Julia,Roberts,BE123456789,Belgium Ventage 10/
12,150,USD,14-01-2009";
@Produce(uri = "direct:start")
private ProducerTemplate template;
@EndpointInject(uri = "mock:result")
private MockEndpoint resultEndpoint;
@Test
public void testMarshallMessage() throws Exception {
resultEndpoint.expectedBodiesReceived(result);
template.sendBody(generateModel());
resultEndpoint.assertIsSatisfied();
}
private List<Map<String, Object>> generateModel() {
Map<String, Object> model = new HashMap<String, Object>();
Order order = new Order();
order.setOrderNr(10);
order.setAmount(new BigDecimal("150"));
order.setIsinCode("BE123456789");
D ATA F O R M AT A PPE NDIX
320
order.setInstrumentName("Belgium Ventage 10/12");
order.setCurrency("USD");
Calendar calendar = new GregorianCalendar();
calendar.set(2009, 0, 14);
order.setOrderDate(calendar.getTime());
Client client = new Client();
client.setClientNr("A1");
client.setFirstName("Julia");
client.setLastName("Roberts");
order.setClient(client);
model.put(order.getClass().getName(), order);
model.put(client.getClass().getName(), client);
models.add(0, model);
return models;
}
@Configuration
public static class ContextConfig extends SingleRouteCamelConfiguration {
BindyCsvDataFormat camelDataFormat = new
BindyCsvDataFormat("org.apache.camel.dataformat.bindy.model.complex.twoclassesandonelink");
@Override
@Bean
public RouteBuilder route() {
return new RouteBuilder() {
@Override
public void configure() {
from("direct:start").marshal(camelDataFormat).to("mock:result");
}
};
}
}
}
Listing 52. Unmarshall
package org.apache.camel.dataformat.bindy.csv;
import
import
import
import
import
import
import
import
321
org.apache.camel.EndpointInject;
org.apache.camel.builder.RouteBuilder;
org.apache.camel.component.mock.MockEndpoint;
org.apache.camel.spring.javaconfig.SingleRouteCamelConfiguration;
org.junit.Test;
org.springframework.config.java.annotation.Bean;
org.springframework.config.java.annotation.Configuration;
org.springframework.config.java.test.JavaConfigContextLoader;
D ATA F O R MAT A P P E N D I X
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.AbstractJUnit4SpringContextTests;
@ContextConfiguration(locations =
"org.apache.camel.dataformat.bindy.csv.BindyComplexCsvUnmarshallTest$ContextConfig",
loader = JavaConfigContextLoader.class)
public class BindyComplexCsvUnmarshallTest extends AbstractJUnit4SpringContextTests {
@EndpointInject(uri = "mock:result")
private MockEndpoint resultEndpoint;
@Test
public void testUnMarshallMessage() throws Exception {
resultEndpoint.expectedMessageCount(1);
resultEndpoint.assertIsSatisfied();
}
@Configuration
public static class ContextConfig extends SingleRouteCamelConfiguration {
BindyCsvDataFormat csvBindyDataFormat = new
BindyCsvDataFormat("org.apache.camel.dataformat.bindy.model.complex.twoclassesandonelink");
@Override
@Bean
public RouteBuilder route() {
return new RouteBuilder() {
@Override
public void configure() {
from("file://src/test/
data?noop=true").unmarshal(csvBindyDataFormat).to("mock:result");
}
};
}
}
}
In this example, BindyCsvDataFormat class has been instantiated in a
traditional way but it is also possible to provide information directly to the
function (un)marshal like this where BindyType corresponds to the Bindy
DataFormat class to instantiate and the parameter contains the list of
package names.
public static class ContextConfig extends SingleRouteCamelConfiguration {
@Override
@Bean
public RouteBuilder route() {
return new RouteBuilder() {
@Override
public void configure() {
from("direct:start")
D ATA F O R M AT A PPE NDIX
322
.marshal().bindy(BindyType.Csv,
"org.apache.camel.dataformat.bindy.model.simple.oneclass")
.to("mock:result");
}
};
}
}
Using Spring XML
This is really easy to use Spring as your favorite DSL language to declare the
routes to be used for camel-bindy. The following example shows two routes
where the first will pick-up records from files, unmarshal the content and bind
it to their model. The result is then send to a pojo (doing nothing special) and
place them into a queue.
The second route will extract the pojos from the queue and marshal the
content to generate a file containing the csv record
Listing 53. spring dsl
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://camel.apache.org/schema/spring
http://camel.apache.org/schema/spring/camel-spring.xsd">
<bean id="bindyDataformat"
class="org.apache.camel.dataformat.bindy.csv.BindyCsvDataFormat">
<constructor-arg value="org.apache.camel.bindy.model" />
</bean>
<bean id="csv" class="org.apache.camel.bindy.csv.HandleOrderBean" />
<!-- Queuing engine - ActiveMq - work locally in mode virtual memory -->
<bean id="activemq"
class="org.apache.activemq.camel.component.ActiveMQComponent">
<property name="brokerURL" value="vm://localhost:61616"/>
</bean>
<camelContext xmlns="http://camel.apache.org/schema/spring">
<jmxAgent id="agent" disabled="false" />
<route>
<from uri="file://src/data/csv/?noop=true" />
323
D ATA F O R MAT A P P E N D I X
<unmarshal ref="bindyDataformat" />
<to uri="bean:csv" />
<to uri="activemq:queue:in" />
</route>
<route>
<from uri="activemq:queue:in" />
<marshal ref="bindyDataformat" />
<to uri="file://src/data/csv/out/" />
</route>
</camelContext>
</beans>
Dependencies
To use Bindy in your camel routes you need to add the a dependency on
camel-bindy which implements this data format.
If you use maven you could just add the following to your pom.xml,
substituting the version number for the latest & greatest release (see the
download page for the latest versions).
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-bindy</artifactId>
<version>2.1.0</version>
</dependency>
XMLSECURITY DATA FORMAT
Available as of Camel 2.0
The XMLSecurity DataFormat facilitates encryption and decryption of XML
payloads at the Document, Element and Element Content levels (including
simultaneous multi-node encryption/decryption using XPATH).
The encrytion capability is based on formats supported using the Apache
XML Security (Santaurio) project. Encryption/Decryption is "currently"
supported using Triple-DES and AES (128, 192 and 256) encryption formats.
Additional formats can be easily added later as needed. Â (Note: The support
currently offered is for symmetric encryption. This means the same keyset is
needed at both ends of the communication to encrypt/decrypt payloads).
The capability allows Camel users to encrypt/decrypt payloads while being
dispatched or received along a route.Â
D ATA F O R M AT A PPE NDIX
324
Be careful
Please verify that your model classes implements serializable
otherwise the queue manager will raise an error
Options
Option
secureTag
secureTagContents
passPhrase
xmlCipherAlgorithm
Default
Description
null
The XPATH reference to the XML
Element selected for encryption/
decryption. If no tag is specified, the
entire payload is encrypted/decrypted.
false
A boolean value to specify whether the
XML Element is to be encrypted or the
contents of the XML Element
• false = Element Level
• true = Element Content Level
null
A String used as passPhrase to encrypt/
decrypt content. The passPhrase has to
be provided. If no passPhrase is
specified, a default passPhrase is used.
The passPhrase needs to be put
together in conjunction with the
appropriate encryption algorithm. For
example using TRIPLEDES the
passPhase can be a "Only another 24
Byte key"
TRIPLEDES
The cipher algorithm to be used for
encryption/decryption. The available
choices are:
• XMLCipher.TRIPLEDES
• XMLCipher.AES_128
• XMLCipher.AES_192
• XMLCipher.AES_256
Marshal
In order to encrypt the payload, the marshal processor needs to be applied
on the route followed by the secureXML() tag.
325
D ATA F O R MAT A P P E N D I X
Unmarshal
In order to decrypt the payload, the unmarshal processor needs to be applied
on the route followed by the secureXML() tag.
Examples
Given below are several examples of how marshalling could be performaed
at the Document, Element and Content levels.
Full Payload encryption/decryption
from("direct:start").
marshal().secureXML().
unmarshal().secureXML().
to("direct:end");
Partial Payload Content Only encryption/decryption*
String tagXPATH = "//cheesesites/italy/cheese";
boolean secureTagContent = true;
...
from("direct:start").
marshal().secureXML(tagXPATH , secureTagContent ).
unmarshal().secureXML(tagXPATH , secureTagContent).
to("direct:end");
Partial Multi Node Payload Content Only encryption/
decryption*
String tagXPATH = "//cheesesites/*/cheese";
boolean secureTagContent = true;
....
from("direct:start").
marshal().secureXML(tagXPATH , secureTagContent ).
unmarshal().secureXML(tagXPATH , secureTagContent).
to("direct:end");
D ATA F O R M AT A PPE NDIX
326
Partial Payload Content Only encryption/decryption with
choice of passPhrase(password)*
String tagXPATH = "//cheesesites/italy/cheese";
boolean secureTagContent = true;
....
String passPhrase = "Just another 24 Byte key";
from("direct:start").
marshal().secureXML(tagXPATH , secureTagContent , passPhrase).
unmarshal().secureXML(tagXPATH , secureTagContent, passPhrase).
to("direct:end");
Partial Payload Content Only encryption/decryption with
passPhrase(password) and Algorithm*Â
import org.apache.xml.security.encryption.XMLCipher;
....
String tagXPATH = "//cheesesites/italy/cheese";
boolean secureTagContent = true;
String passPhrase = "Just another 24 Byte key";
String algorithm= XMLCipher.TRIPLEDES;
from("direct:start").
marshal().secureXML(tagXPATH , secureTagContent , passPhrase, algorithm).
unmarshal().secureXML(tagXPATH , secureTagContent, passPhrase, algorithm).
to("direct:end");
Dependencies
This data format is provided in the camel-xmlsecurity component.
The GZip Data Format is a message compression and de-compression
format. It uses the same deflate algorithm that is used in Zip DataFormat,
although some additional headers are provided. This format is produced by
popular gzip/gunzip tool. Messages marshalled using GZip compression can
be unmarshalled using GZip decompression just prior to being consumed at
the endpoint. The compression capability is quite useful when you deal with
large XML and Text based payloads or when you read messages previously
comressed using gzip tool.
Options
There are no options provided for this data format.
327
D ATA F O R MAT A P P E N D I X
Marshal
In this example we marshal a regular text/XML payload to a compressed
payload employing gzip compression format and send it an ActiveMQ queue
called MY_QUEUE.
from("direct:start").marshal().gzip().to("activemq:queue:MY_QUEUE");
Unmarshal
In this example we unmarshal a gzipped payload from an ActiveMQ queue
called MY_QUEUE to its original format, and forward it for processing to
the UnGZippedMessageProcessor.
from("activemq:queue:MY_QUEUE").unmarshal().gzip().process(new
UnGZippedMessageProcessor());
Dependencies
This data format is provided in camel-core so no additional dependencies is
needed.
CASTOR
Available as of Camel 2.1
Castor is a Data Format which uses the Castor XML library to unmarshal an
XML payload into Java objects or to marshal Java objects into an XML
payload.
As usually you can use either Java DSL or Spring XML to work with Castor
Data Format.
Using the Java DSL
from("direct:order").
marshal().castor().
to("activemq:queue:order");
For example the following uses a named DataFormat of Castor which uses
default Castor data binding features.
D ATA F O R M AT A PPE NDIX
328
CastorDataFormat castor = new CastorDataFormat ();
from("activemq:My.Queue").
unmarshal(castor).
to("mqseries:Another.Queue");
If you prefer to use a named reference to a data format which can then be
defined in your Registry such as via your Spring XML file. e.g.
from("activemq:My.Queue").
unmarshal("mycastorType").
to("mqseries:Another.Queue");
If you want to override default mapping schema by providing a mapping file
you can set it as follows.
CastorDataFormat castor = new CastorDataFormat ();
castor.setMappingFile("mapping.xml");
Also if you want to have more control on Castor Marshaller and Unmarshaller
you can access them as below.
castor.getMarshaller();
castor.getUnmarshaller();
Using Spring XML
The following example shows how to use Castor to unmarshal using Spring
configuring the castor data type
<camelContext id="camel" xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="direct:start"/>
<unmarshal>
<castor validation="true" />
</unmarshal>
<to uri="mock:result"/>
</route>
</camelContext>
This example shows how to configure the data type just once and reuse it on
multiple routes. You have to set the <castor> element directly in
<camelContext>.
329
D ATA F O R MAT A P P E N D I X
<camelContext>
<camelContext id="camel" xmlns="http://camel.apache.org/schema/spring">
<dataFormats>
<castor id="myCastor"/>
</dataFormats>
<route>
<from uri="direct:start"/>
<marshal ref="myCastor"/>
<to uri="direct:marshalled"/>
</route>
<route>
<from uri="direct:marshalled"/>
<unmarshal ref="myCastor"/>
<to uri="mock:result"/>
</route>
</camelContext>
Options
Castor supports the following options
Option
Type
Default
Description
encoding
String
UTF-8
Encoding to use when marshalling an
Object to XML
validation
Boolean
false
Whether validation is turned on or off.
mappingFile
String
null
Path to a Castor mapping file to load
from the classpath.
packages
String[]
null
Add additional packages to Castor
XmlContext
classNames
String[]
null
Add additional class names to Castor
XmlContext
Dependencies
To use Castor in your camel routes you need to add the a dependency on
camel-castor which implements this data format.
If you use maven you could just add the following to your pom.xml,
substituting the version number for the latest & greatest release (see the
download page for the latest versions).
D ATA F O R M AT A PPE NDIX
330
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-castor</artifactId>
<version>2.1.0</version>
</dependency>
Protobuf - Protocol Buffers
"Protocol Buffers - Google's data interchange format"
Camel provides a Data Format to serialse between Java and the Protocol
Buffer protocol. The project's site details why you may wish to choose this
format over xml. Protocol Buffer is language-neutral and platform-neutral, so
messages produced by your Camel routes may be consumed by other
language implementations.
API Site
Protobuf Implementation
Protobuf Java Tutorial
PROTOBUF OVERVIEW
This quick overview of how to use Protobuf. For more detail see the complete
tutorial
Defining the proto format
The first step is to define the format for the body of your exchange. This is
defined in a .proto file as so:
Listing 54. addressbook.proto
package org.apache.camel.component.protobuf;
option java_package = "org.apache.camel.component.protobuf";
option java_outer_classname = "AddressBookProtos";
message Person {
required string name = 1;
required int32 id = 2;
optional string email = 3;
enum PhoneType {
331
PR O T O B UF - P R O T O C OL B U F F E R S
Available from Camel 2.2
MOBILE = 0;
HOME = 1;
WORK = 2;
}
message PhoneNumber {
required string number = 1;
optional PhoneType type = 2 [default = HOME];
}
repeated PhoneNumber phone = 4;
}
message AddressBook {
repeated Person person = 1;
}
Generating Java classes
The Protobuf SDK provides a compiler which will generate the Java classes for
the format we defined in our .proto file. You can run the compiler for any
additional supported languages you require.
protoc --java_out=. ./addressbook.proto
This will generate a single Java class named AddressBookProtos which
contains inner classes for Person and AddressBook. Builders are also
implemented for you. The generated classes implement
com.google.protobuf.Message which is required by the serialisation
mechanism. For this reason it important that only these classes are used in
the body of your exchanges. Camel will throw an exception on route creation
if you attempt to tell the Data Format to use a class that does not implement
com.google.protobuf.Message. Use the generated builders to translate the
data from any of your existing domain classes.
JAVA DSL
You can use create the ProtobufDataFormat instance and pass it to Camel
DataFormat marshal and unmarsha API like this.
PR O T O B U F - PR O T O C O L B U FFE R S
332
ProtobufDataFormat format = new ProtobufDataFormat(Person.getDefaultInstance());
from("direct:in").marshal(format);
from("direct:back").unmarshal(format).to("mock:reverse");
Or use the DSL protobuf() passing the unmarshal default instance or default
instance class name like this.
// You don't need to specify the default instance for protobuf
marshaling
from("direct:marshal").marshal().protobuf();
from("direct:unmarshalA").unmarshal().
protobuf("org.apache.camel.dataformat.protobuf.generated.AddressBookProtos$Person").
to ("mock:reverse");
from("direct:unmarshalB").unmarshal().protobuf(Person.getDefaultInstance()).to("mock:reverse");
SPRING DSL
The following example shows how to use Castor to unmarshal using Spring
configuring the protobuf data type
<camelContext id="camel" xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="direct:start"/>
<unmarshal>
<protobuf
instanceClass="org.apache.camel.dataformat.protobuf.generated.AddressBookProtos$Person"
/>
</unmarshal>
<to uri="mock:result"/>
</route>
</camelContext>
Dependencies
To use Protobuf in your camel routes you need to add the a dependency on
camel-protobuf which implements this data format.
If you use maven you could just add the following to your pom.xml,
substituting the version number for the latest & greatest release (see the
download page for the latest versions).
333
PR O T O B UF - P R O T O C OL B U F F E R S
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-protobuf</artifactId>
<version>2.2.0</version>
</dependency>
SOAP DATAFORMAT
Available as of Camel 2.3
SOAP is a Data Format which uses JAXB2 and JAX-WS annotations to
marshal and unmarshal SOAP payloads. It provides the basic features of
Apache CXF without need for the CXF Stack.
ElementNameStrategy
An element name strategy is used for two purposes. The first is to find a xml
element name for a given object and soap action when marshalling the
object into a SOAP message. The second is to find an Exception class for a
given soap fault name.
Strategy
Usage
QNameStrategy
Uses a fixed qName that is configured on
instantiation. Exception lookup is not supported
TypeNameStrategy
Uses the name and namespace from the
@XMLType annotation of the given type. If no
namespace is set then package-info is used.
Exception lookup is not supported
ServiceInterfaceStrategy
Uses information from a webservice interface to
determine the type name and to find the
exception class for a SOAP fault
If you have generated the web service stub code with cxf-codegen or a
similar tool then you probably will want to use the ServiceInterfaceStrategy.
In the case you have no annotated service interface you should use
QNameStrategy or TypeNameStrategy.
Using the Java DSL
The following example uses a named DataFormat of soap which is configured
with the package com.example.customerservice to initialize the JAXBContext.
The second parameter is the ElementNameStrategy. The route is able to
marshal normal objects as well as exceptions. (Note the below just sends a
PR O T O B U F - PR O T O C O L B U FFE R S
334
SOAP Envelope to a queue. A web service provider would actually need to be
listening to the queue for a SOAP call to actually occur, in which case it would
be a one way SOAP request. If you need request reply then you should look
at the next example.)
SoapJaxbDataFormat soap = new SoapJaxbDataFormat("com.example.customerservice", new
ServiceInterfaceStrategy(CustomerService.class));
from("direct:start")
.marshal(soap)
.to("jms:myQueue");
Examples
Webservice client
The following route supports marshalling the request and unmarshalling a
response or fault.
String WS_URI = "cxf://http://myserver/
customerservice?serviceClass=com.example.customerservice&dataFormat=MESSAGE";
SoapJaxbDataFormat soapDF = new SoapJaxbDataFormat("com.example.customerservice", new
ServiceInterfaceStrategy(CustomerService.class));
from("direct:customerServiceClient")
.onException(Exception.class)
.handled(true)
.unmarshal(soapDF)
.end()
.marshal(soapDF)
.to(WS_URI)
.unmarshal(soapDF);
The below snippet creates a proxy for the service interface and makes a
SOAP call to the above route.
import org.apache.camel.Endpoint;
import org.apache.camel.component.bean.ProxyHelper;
...
Endpoint startEndpoint = context.getEndpoint("direct:customerServiceClient");
ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
// CustomerService below is the service endpoint interface, *not* the
javax.xml.ws.Service subclass
CustomerService proxy = ProxyHelper.createProxy(startEndpoint, classLoader,
CustomerService.class);
GetCustomersByNameResponse response = proxy.getCustomersByName(new
GetCustomersByName());
335
PR O T O B UF - P R O T O C OL B U F F E R S
See also
As the SOAP dataformat inherits from the JAXB dataformat most
settings apply here as well
Webservice Server
Using the following route sets up a webservice server that listens on jms
queue customerServiceQueue and processes requests using the class
CustomerServiceImpl. The customerServiceImpl of course should implement
the interface CustomerService. Instead of directly instantiating the server
class it could be defined in a spring context as a regular bean.
SoapJaxbDataFormat soapDF = new SoapJaxbDataFormat("com.example.customerservice", new
ServiceInterfaceStrategy(CustomerService.class));
CustomerService serverBean = new CustomerServiceImpl();
from("jms://queue:customerServiceQueue")
.onException(Exception.class)
.handled(true)
.marshal(soapDF)
.end()
.unmarshal(soapDF)
.bean(serverBean)
.marshal(soapDF);
Dependencies
To use the SOAP dataformat in your camel routes you need to add the
following dependency to your pom.
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-soap</artifactId>
<version>2.3.0</version>
</dependency>
CRYPTO
Available as of Camel 2.3
The Crypto Data Format integrates the Java Cryptographic Extension into
Camel, allowing simple and flexible encryption and decryption of messages
using Camel's familiar marshall and unmarshal formatting mechanism. It
PR O T O B U F - PR O T O C O L B U FFE R S
336
assumes marshalling to mean encryption to cyphertext and unmarshalling
decryption back to the original plaintext.
Options
Name
Type
Default
Description
algorithm
String
DES/CBC/
PKCS5Padding
The JCE algoorithm name indicating the cryptographic algorithm that
will be used.
algorithmParamterSpec
AlgorithmParameterSpec
null
A JCE AlgorithmParameterSpec used to initialize the Cipher.
bufferSize
Integer
2048
the size of the buffer used in the signature process.
cryptoProvider
String
null
The name of the JCE Security Provider that should be used.
initializationVector
byte[]
null
A byte array containing the Initialization Vector that will be used to
initialize the Cipher.
inline
boolean
false
Flag indicating that the configured IV should be inlined into the
encrypted data stream.
macAlgorithm
String
null
The JCE algorithm name indicating the Message Authentication
algorithm.
shouldAppendHMAC
boolean
null
Flag indicating that a Message Authentication Code should be
calculated and appended to the encrypted data.
Basic Usage
At its most basic all that is required to encrypt/decrypt an exchange is a
shared secret key. If one or more instances of the Crypto data format are
configured with this key the format can be used to encrypt the payload in
one route (or part of one) and decrypted in another. For example, using the
Java DSL as follows:
KeyGenerator generator = KeyGenerator.getInstance("DES");
CryptoDataFormat cryptoFormat = new CryptoDataFormat("DES", generator.generateKey());
from("direct:basic-encryption")
.marshal(cryptoFormat)
.to("mock:encrypted")
.unmarshal(cryptoFormat)
.to("mock:unencrypted");
In Spring the dataformat is configured first and then used in routes
<camelContext id="camel" xmlns="http://camel.apache.org/schema/spring">
<dataFormats>
<crypto id="basic" algorithm="DES" keyRef="desKey" />
</dataFormats>
...
<route>
<from uri="direct:basic-encryption" />
<marshal ref="basic" />
<to uri="mock:encrypted" />
337
PR O T O B UF - P R O T O C OL B U F F E R S
<unmarshal ref="basic" />
<to uri="mock:unencrypted" />
</route>
</camelContext>
Specifying the Encryption Algorithm.
Changing the algorithm is a matter of supplying the JCE algorithm name. If
you change the algorithm you will need to use a compatible key.
KeyGenerator generator = KeyGenerator.getInstance("DES");
CryptoDataFormat cryptoFormat = new CryptoDataFormat("DES", generator.generateKey());
cryptoFormat.setShouldAppendHMAC(true);
cryptoFormat.setMacAlgorithm("HmacMD5");
from("direct:hmac-algorithm")
.marshal(cryptoFormat)
.to("mock:encrypted")
.unmarshal(cryptoFormat)
.to("mock:unencrypted");
Specifying an Initialization Vector.
Some crypto algorhithms, particularly block algorithms, require configuration
with an initial block of data known as an Initialization Vector. In the JCE this is
passed as an AlgorithmParameterSpec when the Cipher is initialized. To use
such a vector with the CryptoDataFormat you can configure it with a byte[]
contianing the required data e.g.
KeyGenerator generator = KeyGenerator.getInstance("DES");
byte[] initializationVector = new byte[] {0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06,
0x07};
CryptoDataFormat cryptoFormat = new CryptoDataFormat("DES/CBC/PKCS5Padding",
generator.generateKey());
cryptoFormat.setInitializationVector(initializationVector);
from("direct:init-vector")
.marshal(cryptoFormat)
.to("mock:encrypted")
.unmarshal(cryptoFormat)
.to("mock:unencrypted");
or with spring, suppling a reference to a byte[]
PR O T O B U F - PR O T O C O L B U FFE R S
338
<crypto id="initvector" algorithm="DES/CBC/PKCS5Padding" keyRef="desKey"
initVectorRef="initializationVector" />
The same vector is required in both the encryption and decryption phases. As
it is not necessary to keep the IV a secret, the DataFormat allows for it to be
inlined into the encrypted data and subsequently read out in the decryption
phase to initialize the Cipher. To inline the IV set the /oinline flag.
KeyGenerator generator = KeyGenerator.getInstance("DES");
byte[] initializationVector = new byte[] {0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06,
0x07};
SecretKey key = generator.generateKey();
CryptoDataFormat cryptoFormat = new CryptoDataFormat("DES/CBC/PKCS5Padding", key);
cryptoFormat.setInitializationVector(initializationVector);
cryptoFormat.setShouldInlineInitializationVector(true);
CryptoDataFormat decryptFormat = new CryptoDataFormat("DES/CBC/PKCS5Padding", key);
decryptFormat.setShouldInlineInitializationVector(true);
from("direct:inline")
.marshal(cryptoFormat)
.to("mock:encrypted")
.unmarshal(decryptFormat)
.to("mock:unencrypted");
or with spring.
<crypto id="inline" algorithm="DES/CBC/PKCS5Padding" keyRef="desKey"
initVectorRef="initializationVector"
inline="true" />
<crypto id="inline-decrypt" algorithm="DES/CBC/PKCS5Padding" keyRef="desKey"
inline="true" />
For more information of the use of Initialization Vectors, consult
• http://en.wikipedia.org/wiki/Initialization_vector
• http://www.herongyang.com/Cryptography/
• http://en.wikipedia.org/wiki/Block_cipher_modes_of_operation
Hashed Message Authentication Codes (HMAC)
To avoid attacks against the encrypted data while it is in transit the
CryptoDataFormat can also calculate a Message Authentication Code forthe
encrypted exchange contents based on a configurable MAC algorithm. The
calculated HMAC is appended to the stream after encryption. It is separated
from the stream in the decryption phase. The MAC is recalculated and
verified against the transmitted version to insure nothing was tampered with
339
PR O T O B UF - P R O T O C OL B U F F E R S
in transit.For more information on Message Authentication Codes see
http://en.wikipedia.org/wiki/HMAC
KeyGenerator generator = KeyGenerator.getInstance("DES");
CryptoDataFormat cryptoFormat = new CryptoDataFormat("DES", generator.generateKey());
cryptoFormat.setShouldAppendHMAC(true);
from("direct:hmac")
.marshal(cryptoFormat)
.to("mock:encrypted")
.unmarshal(cryptoFormat)
.to("mock:unencrypted");
or with spring.
<crypto id="hmac" algorithm="DES" keyRef="desKey" shouldAppendHMAC="true" />
By default the HMAC is calculated using the HmacSHA1 mac algorithm
though this can be easily changed by supplying a different algorithm name.
See here for how to check what algorithms are available through the
configured security providers
KeyGenerator generator = KeyGenerator.getInstance("DES");
CryptoDataFormat cryptoFormat = new CryptoDataFormat("DES", generator.generateKey());
cryptoFormat.setShouldAppendHMAC(true);
cryptoFormat.setMacAlgorithm("HmacMD5");
from("direct:hmac-algorithm")
.marshal(cryptoFormat)
.to("mock:encrypted")
.unmarshal(cryptoFormat)
.to("mock:unencrypted");
or with spring.
<crypto id="hmac-algorithm" algorithm="DES" keyRef="desKey" macAlgorithm="HmacMD5"
shouldAppendHMAC="true" />
Supplying Keys dynamically.
When using a Recipient list or similar EIP the recipient of an exchange can
vary dynamically. Using the same key across all recipients may neither be
feasible or desirable. It would be useful to be able to specify keys
dynamically on a per exchange basis. The exchange could then be
dynamically enriched with the key of its target recipient before being
PR O T O B U F - PR O T O C O L B U FFE R S
340
processed by the data format. To facilitate this the DataFormat allow for keys
to be supplied dynamically via the message headers below
• CryptoDataFormat.KEY "CamelCryptoKey"
CryptoDataFormat cryptoFormat = new CryptoDataFormat("DES", null);
/**
* Note: the header containing the key should be cleared after
* marshalling to stop it from leaking by accident and
* potentially being compromised. The processor version below is
* arguably better as the key is left in the header when you use
* the DSL leaks the fact that camel encryption was used.
*/
from("direct:key-in-header-encrypt")
.marshal(cryptoFormat)
.removeHeader(CryptoDataFormat.KEY)
.to("mock:encrypted");
from("direct:key-in-header-decrypt").unmarshal(cryptoFormat).process(new Processor() {
public void process(Exchange exchange) throws Exception {
exchange.getIn().getHeaders().remove(CryptoDataFormat.KEY);
exchange.getOut().copyFrom(exchange.getIn());
}
}).to("mock:unencrypted");
or with spring.
<crypto id="nokey" algorithm="DES" />
Dependencies
To use the Crypto dataformat in your camel routes you need to add the
following dependency to your pom.
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-crypto</artifactId>
<version>2.3.0</version>
</dependency>
See Also
• Data Format
• Crypto (Digital Signatures)
341
PR O T O B UF - P R O T O C OL B U F F E R S
SYSLOG DATAFORMAT
Available as of Camel 2.6
The syslog dataformat is used for working with RFC3164 messages.
This component supports the following:
▪ UDP consumption of syslog messages
▪ Agnostic data format using either plain String objects or
SyslogMessage model objects.
▪ Type Converter from/to SyslogMessage and String
▪ Integration with the camel-mina component.
▪ Integration with the camel-netty component.
Maven users will need to add the following dependency to their pom.xml for
this component:
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-syslog</artifactId>
<version>x.x.x</version>
<!-- use the same version as your Camel core version -->
</dependency>
RFC3164 Syslog protocol
Syslog uses the user datagram protocol (UDP) 1 as its underlying transport
layer mechanism.
The UDP port that has been assigned to syslog is 514.
To expose a Syslog listener service we reuse the existing camel-mina
component or camel-netty where we just use the Rfc3164SyslogDataFormat
to marshal and unmarshal messages
Exposing a Syslog listener
In our Spring XML file, we configure an endpoint to listen for udp messages
on port 10514, note that in netty we disable the defaultCodec, this
will allow a fallback to a NettyTypeConverter and delivers the message as an
InputStream:
<camelContext id="myCamel" xmlns="http://camel.apache.org/schema/spring">
<dataFormats>
<syslog id="mySyslog"/>
</dataFormats>
PR O T O B U F - PR O T O C O L B U FFE R S
342
<route>
<from
uri="netty:udp://localhost:10514?sync=false&amp;allowDefaultCodec=false"/>
<unmarshal ref="mySyslog"/>
<to uri="mock:stop1"/>
</route>
</camelContext>
The same route using camel-mina
<camelContext id="myCamel" xmlns="http://camel.apache.org/schema/spring">
<dataFormats>
<syslog id="mySyslog"/>
</dataFormats>
<route>
<from uri="mina:udp://localhost:10514"/>
<unmarshal ref="mySyslog"/>
<to uri="mock:stop1"/>
</route>
</camelContext>
Sending syslog messages to a remote destination
<camelContext id="myCamel" xmlns="http://camel.apache.org/schema/spring">
<dataFormats>
<syslog id="mySyslog"/>
</dataFormats>
<route>
<from uri="direct:syslogMessages"/>
<marshal ref="mySyslog"/>
<to uri="mina:udp://remotehost:10514"/>
</route>
</camelContext>
See Also
•
•
•
•
343
Configuring Camel
Component
Endpoint
Getting Started
PR O T O B UF - P R O T O C OL B U F F E R S
CHAPTER
10
°°°°
Pattern Appendix
There now follows a breakdown of the various Enterprise Integration Patterns
that Camel supports
MESSAGING SYSTEMS
Message Channel
Camel supports the Message Channel from the EIP patterns. The Message
Channel is an internal implementation detail of the Endpoint interface and all
interactions with the Message Channel are via the Endpoint interfaces.
For more details see
• Message
• Message Endpoint
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
Message
Camel supports the Message from the EIP patterns using the Message
interface.
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
344
To support various message exchange patterns like one way Event
Message and Request Reply messages Camel uses an Exchange interface
which has a pattern property which can be set to InOnly for an Event
Message which has a single inbound Message, or InOut for a Request Reply
where there is an inbound and outbound message.
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
Pipes and Filters
Camel supports the Pipes and Filters from the EIP patterns in various ways.
With Camel you can split your processing across multiple independent
Endpoint instances which can then be chained together.
Using Routing Logic
You can create pipelines of logic using multiple Endpoint or Message
Translator instances as follows
from("direct:a").pipeline("direct:x", "direct:y", "direct:z", "mock:result");
Though pipeline is the default mode of operation when you specify multiple
outputs in Camel. The opposite to pipeline is multicast; which fires the same
message into each of its outputs. (See the example below).
In Spring XML you can use the <pipeline/> element as of 1.4.0 onwards
<route>
<from uri="activemq:SomeQueue"/>
<pipeline>
345
CH AP T E R 10 - PAT T E R N A P P E N D I X
<bean ref="foo"/>
<bean ref="bar"/>
<to uri="activemq:OutputQueue"/>
</pipeline>
</route>
In the above the pipeline element is actually unnecessary, you could use
this...
<route>
<from uri="activemq:SomeQueue"/>
<bean ref="foo"/>
<bean ref="bar"/>
<to uri="activemq:OutputQueue"/>
</route>
Its just a bit more explicit. However if you wish to use <multicast/> to avoid
a pipeline - to send the same message into multiple pipelines - then the
<pipeline/> element comes into its own.
<route>
<from uri="activemq:SomeQueue"/>
<multicast>
<pipeline>
<bean ref="something"/>
<to uri="log:Something"/>
</pipeline>
<pipeline>
<bean ref="foo"/>
<bean ref="bar"/>
<to uri="activemq:OutputQueue"/>
</pipeline>
</multicast>
</route>
In the above example we are routing from a single Endpoint to a list of
different endpoints specified using URIs. If you find the above a bit confusing,
try reading about the Architecture or try the Examples
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
346
Message Router
The Message Router from the EIP patterns allows you to consume from an
input destination, evaluate some predicate then choose the right output
destination.
The following example shows how to route a request from an input
queue:a endpoint to either queue:b, queue:c or queue:d depending on
the evaluation of various Predicate expressions
Using the Fluent Builders
RouteBuilder builder = new RouteBuilder() {
public void configure() {
errorHandler(deadLetterChannel("mock:error"));
from("seda:a")
.choice()
.when(header("foo").isEqualTo("bar"))
.to("seda:b")
.when(header("foo").isEqualTo("cheese"))
.to("seda:c")
.otherwise()
.to("seda:d");
}
};
Using the Spring XML Extensions
<camelContext errorHandlerRef="errorHandler" xmlns="http://camel.apache.org/schema/
spring">
<route>
<from uri="seda:a"/>
<choice>
<when>
<xpath>$foo = 'bar'</xpath>
<to uri="seda:b"/>
</when>
<when>
<xpath>$foo = 'cheese'</xpath>
<to uri="seda:c"/>
</when>
<otherwise>
<to uri="seda:d"/>
</otherwise>
347
CH AP T E R 10 - PAT T E R N A P P E N D I X
</choice>
</route>
</camelContext>
Choice without otherwise
If you use a choice without adding an otherwise, any unmatched exchanges
will be dropped by default.
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
Message Translator
Camel supports the Message Translator from the EIP patterns by using an
arbitrary Processor in the routing logic, by using a bean to perform the
transformation, or by using transform() in the DSL. You can also use a Data
Format to marshal and unmarshal messages in different encodings.
Using the Fluent Builders
You can transform a message using Camel's Bean Integration to call any
method on a bean in your Registry such as your Spring XML configuration file
as follows
from("activemq:SomeQueue").
beanRef("myTransformerBean", "myMethodName").
to("mqseries:AnotherQueue");
Where the "myTransformerBean" would be defined in a Spring XML file or
defined in JNDI etc. You can omit the method name parameter from
beanRef() and the Bean Integration will try to deduce the method to invoke
from the message exchange.
or you can add your own explicit Processor to do the transformation
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
348
from("direct:start").process(new Processor() {
public void process(Exchange exchange) {
Message in = exchange.getIn();
in.setBody(in.getBody(String.class) + " World!");
}
}).to("mock:result");
or you can use the DSL to explicitly configure the transformation
from("direct:start").transform(body().append(" World!")).to("mock:result");
Use Spring XML
You can also use Spring XML Extensions to do a transformation. Basically
any Expression language can be substituted inside the transform element as
shown below
<camelContext xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="direct:start"/>
<transform>
<simple>${in.body} extra data!</simple>
</transform>
<to uri="mock:end"/>
</route>
</camelContext>
Or you can use the Bean Integration to invoke a bean
<route>
<from uri="activemq:Input"/>
<bean ref="myBeanName" method="doTransform"/>
<to uri="activemq:Output"/>
</route>
You can also use Templating to consume a message from one destination,
transform it with something like Velocity or XQuery and then send it on to
another destination. For example using InOnly (one way messaging)
from("activemq:My.Queue").
to("velocity:com/acme/MyResponse.vm").
to("activemq:Another.Queue");
If you want to use InOut (request-reply) semantics to process requests on the
My.Queue queue on ActiveMQ with a template generated response, then
sending responses back to the JMSReplyTo Destination you could use this.
349
CH AP T E R 10 - PAT T E R N A P P E N D I X
from("activemq:My.Queue").
to("velocity:com/acme/MyResponse.vm");
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
▪ Content Enricher
▪ Using getIn or getOut methods on Exchange
Message Endpoint
Camel supports the Message Endpoint from the EIP patterns using the
Endpoint interface.
When using the DSL to create Routes you typically refer to Message
Endpoints by their URIs rather than directly using the Endpoint interface. Its
then a responsibility of the CamelContext to create and activate the
necessary Endpoint instances using the available Component
implementations.
For more details see
• Message
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
350
MESSAGING CHANNELS
Point to Point Channel
Camel supports the Point to Point Channel from the EIP patterns using the
following components
• SEDA for in-VM seda based messaging
• JMS for working with JMS Queues for high performance, clustering
and load balancing
• JPA for using a database as a simple message queue
• XMPP for point-to-point communication over XMPP (Jabber)
• and others
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
Publish Subscribe Channel
Camel supports the Publish Subscribe Channel from the EIP patterns using for
example the following components:
• JMS for working with JMS Topics for high performance, clustering and
load balancing
• XMPP when using rooms for group communication
• SEDA for working with SEDA in the same CamelContext which can
work in pub-sub, but allowing multiple consumers.
• VM as SEDA but for intra-JVM.
351
CH AP T E R 10 - PAT T E R N A P P E N D I X
Using Routing Logic
Another option is to explicitly list the publish-subscribe relationship in your
routing logic; this keeps the producer and consumer decoupled but lets you
control the fine grained routing configuration using the DSL or Xml
Configuration.
Using the Fluent Builders
RouteBuilder builder = new RouteBuilder() {
public void configure() {
errorHandler(deadLetterChannel("mock:error"));
from("seda:a")
.multicast().to("seda:b", "seda:c", "seda:d");
}
};
Using the Spring XML Extensions
<camelContext errorHandlerRef="errorHandler" xmlns="http://camel.apache.org/schema/
spring">
<route>
<from uri="seda:a"/>
<multicast>
<to uri="seda:b"/>
<to uri="seda:c"/>
<to uri="seda:d"/>
</multicast>
</route>
</camelContext>
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
352
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
DEAD LETTER CHANNEL
Camel supports the Dead Letter Channel from the EIP patterns using the
DeadLetterChannel processor which is an Error Handler.
Redelivery
It is common for a temporary outage or database deadlock to cause a
message to fail to process; but the chances are if its tried a few more times
with some time delay then it will complete fine. So we typically wish to use
some kind of redelivery policy to decide how many times to try redeliver a
message and how long to wait before redelivery attempts.
The RedeliveryPolicy defines how the message is to be redelivered. You
can customize things like
• how many times a message is attempted to be redelivered before it
is considered a failure and sent to the dead letter channel
• the initial redelivery timeout
• whether or not exponential backoff is used (i.e. the time between
retries increases using a backoff multiplier)
• whether to use collision avoidance to add some randomness to the
timings
• delay pattern a new option in Camel 2.0, see below for details.
Once all attempts at redelivering the message fails then the message is
forwarded to the dead letter queue.
353
CH AP T E R 10 - PAT T E R N A P P E N D I X
Difference between Dead Letter Channel and Default Error
Handler
The major difference is that Dead Letter Channel has a dead letter
queue that whenever an Exchange could not be processed is
moved to. It will always moved failed exchanges to this queue.
Unlike the Default Error Handler that does not have a dead letter queue.
So whenever an Exchange could not be processed the error is propagated
back to the client.
Notice: You can adjust this behavior of whether the client should be
notified or not with the handled option.
About moving Exchange to dead letter queue and using handled
Handled on Dead Letter Channel was introduced in Camel 2.0, this feature
does not exist in Camel 1.x
When all attempts of redelivery have failed the Exchange is moved to the
dead letter queue (the dead letter endpoint). The exchange is then complete
and from the client point of view it was processed. As such the Dead Letter
Channel have handled the Exchange.
For instance configuring the dead letter channel as:
errorHandler(deadLetterChannel("jms:queue:dead")
.maximumRedeliveries(3).redeliverDealy(5000));
The Dead Letter Channel above will clear the caused exception when the
Exchange is moved to the jms:queue:dead destination and the client will not
notice the failure.
By default handled is true.
How to let the client notice the error?
If you want to move the message to the dead letter queue and also let the
client notice the error, then you can configure the Dead Letter Channel to
not handle the error. For example:
errorHandler(deadLetterChannel("jms:queue:dead")
.maximumRedeliveries(3).redeliverDealy(5000).handled(false));
When all attempts of redelivery have failed the Exchange is moved to the
dead letter queue (the dead letter endpoint). As the Dead Letter Channel
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
354
is configured to not handle it, it will mark the Exchange as failed so the client
will be notified of this error.
About moving Exchange to dead letter queue and using the original
message
Available as of Camel 2.0
The option useOriginalMessage is used for routing the original input
message instead of the current message that potentially is modified during
routing.
For instance if you have this route:
from("jms:queue:order:input")
.to("bean:validateOrder");
.to("bean:transformOrder")
.to("bean:handleOrder");
The route listen for JMS messages and validates, transforms and handle it.
During this the Exchange payload is transformed/modified. So in case
something goes wrong and we want to move the message to another JMS
destination, then we can configure our Dead Letter Channel with the
useOriginalBody option. But when we move the Exchange to this
destination we do not know in which state the message is in. Did the error
happen in before the transformOrder or after? So to be sure we want to move
the original input message we received from jms:queue:order:input. So we
can do this by enabling the useOriginalMessage option as shown below:
// will use original body
errorHandler(deadLetterChannel("jms:queue:dead")
.useOriginalMessage().mamimumRedeliveries(5).redeliverDelay(5000);
Then the messages routed to the jms:queue:dead is the original input. If we
want to manually retry we can move the JMS message from the failed to the
input queue, with no problem as the message is the same as the original we
received.
OnRedelivery
Available in Camel 1.6.0 onwards
When Dead Letter Channel is doing redeliver its possible to configure a
Processor that is executed just before every redelivery attempt. This can be
used for the situations where you need to alter the message before its
redelivered. See below for sample.
355
CH AP T E R 10 - PAT T E R N A P P E N D I X
Handled
See also Exception Clause for more details on the handled policy
as this feature was first introduced here and thus we have more
docuemntation and samples there.
onException and onRedeliver
In Camel 2.0 we also added support for per onException to set a
onRedeliver. That means you can do special on redelivery for
different exceptions, as opposed to onRedelivery set on Dead Letter
Channel can be viewed as a global scope.
Redelivery default values
In Camel 2.0 redelivery is disabled by default, as opposed to Camel 1.x in
which Dead Letter Channel is configured with maximumRedeliveries=5.
The default redeliver policy will use the following values:
• maximumRedeliveries=0 (in Camel 1.x the default value is 5)
• redeliverDelay=1000L (1 second, new as of Camel 2.0)
◦ use initialRedeliveryDelay for previous versions
• maximumRedeliveryDelay = 60 * 1000L (60 seconds)
• And the exponential backoff and collision avoidance is turned off.
• The retriesExhaustedLogLevel are set to LoggingLevel.ERROR
• The retryAttemptedLogLevel are set to LoggingLevel.DEBUG
• Stack traces is logged for exhausted messages from Camel 2.2
onwards.
• Handled exceptions is not logged from Camel 2.3 onwards
The maximum redeliver delay ensures that a delay is never longer than the
value, default 1 minute. This can happen if you turn on the exponential
backoff.
The maximum redeliveries is the number of re delivery attempts. By
default Camel will try to process the exchange 1 + 5 times. 1 time for the
normal attempt and then 5 attempts as redeliveries.
Setting the maximumRedeliveries to a negative value such as -1 will then
always redelivery (unlimited).
Setting the maximumRedeliveries to 0 will disable any re delivery attempt.
Camel will log delivery failures at the DEBUG logging level by default. You
can change this by specifying retriesExhaustedLogLevel and/or
retryAttemptedLogLevel. See ExceptionBuilderWithRetryLoggingLevelSetTest
for an example.
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
356
In Camel 2.0 you can turn logging of stack traces on/off. If turned off
Camel will still log the redelivery attempt. Its just much less verbose.
Redeliver Delay Pattern
Available as of Camel 2.0
Delay pattern is used as a single option to set a range pattern for delays. If
used then the following options does not apply: (delay, backOffMultiplier,
useExponentialBackOff, useCollisionAvoidance, maximumRedeliveryDelay).
The idea is to set groups of ranges using the following syntax:
limit:delay;limit 2:delay 2;limit 3:delay 3;...;limit N:delay N
Each group has two values separated with colon
▪ limit = upper limit
▪ delay = delay in millis
And the groups is again separated with semi colon.
The rule of thumb is that the next groups should have a higher limit
than the previous group.
Lets clarify this with an example:
delayPattern=5:1000;10:5000;20:20000
That gives us 3 groups:
▪ 5:1000
▪ 10:5000
▪ 20:20000
Resulting in these delays for redelivery attempt:
▪ Redelivery attempt number 1..4 = 0 millis (as the first group start
with 5)
▪ Redelivery attempt number 5..9 = 1000 millis (the first group)
▪ Redelivery attempt number 10..19 = 5000 millis (the second group)
▪ Redelivery attempt number 20.. = 20000 millis (the last group)
Note: The first redelivery attempt is 1, so the first group should start with 1
or higher.
You can start a group with limit 1 to eg have a starting delay:
delayPattern=1:1000;5:5000
▪ Redelivery attempt number 1..4 = 1000 millis (the first group)
▪ Redelivery attempt number 5.. = 5000 millis (the last group)
There is no requirement that the next delay should be higher than the
previous. You can use any delay value you like. For example with
delayPattern=1:5000;3:1000 we start with 5 sec delay and then later
reduce that to 1 second.
357
CH AP T E R 10 - PAT T E R N A P P E N D I X
Redelivery header
When a message is redelivered the DeadLetterChannel will append a
customizable header to the message to indicate how many times its been
redelivered.
In Camel 1.x: The header is org.apache.camel.redeliveryCount.
In Camel 2.0: The header is CamelRedeliveryCounter, which is also
defined on the Exchange.REDELIVERY_COUNTER.
In Camel 2.6: The header CamelRedeliveryMaxCounter, which is also
defined on the Exchange.REDELIVERY_MAX_COUNTER, contains the maximum
redelivery setting. This header is absent if you use retryWhile or have
unlimited maximum redelivery configured.
And a boolean flag whether it is being redelivered or not (first attempt)
In Camel 1.x: The header org.apache.camel.Redelivered contains a
boolean if the message is redelivered or not.
In Camel 2.0: The header CamelRedelivered contains a boolean if the
message is redelivered or not, which is also defined on the
Exchange.REDELIVERED.
Which endpoint failed
Available as of Camel 2.1
When Camel routes messages it will decorate the Exchange with a
property that contains the last endpoint Camel send the Exchange to:
String lastEndpointUri = exchange.getProperty(Exchange.TO_ENDPOINT, String.class);
The Exchange.TO_ENDPOINT have the constant value CamelToEndpoint.
This information is updated when Camel sends a message to any
endpoint. So if it exists its the last endpoint which Camel send the Exchange
to.
When for example processing the Exchange at a given Endpoint and the
message is to be moved into the dead letter queue, then Camel also
decorates the Exchange with another property that contains that last
endpoint:
String failedEndpointUri = exchange.getProperty(Exchange.FAILURE_ENDPOINT,
String.class);
The Exchange.FAILURE_ENDPOINT have the constant value
CamelFailureEndpoint.
This allows for example you to fetch this information in your dead letter
queue and use that for error reporting.
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
358
This is useable if the Camel route is a bit dynamic such as the dynamic
Recipient List so you know which endpoints failed.
Notice: These information is kept on the Exchange even if the message
was successfully processed by a given endpoint, and then later fails for
example in a local Bean processing instead. So beware that this is a hint that
helps pinpoint errors.
from("activemq:queue:foo")
.to("http://someserver/somepath")
.beanRef("foo");
Now suppose the route above and a failure happens in the foo bean. Then
the Exchange.TO_ENDPOINT and Exchange.FAILURE_ENDPOINT will still
contain the value of http://someserver/somepath.
Samples
The following example shows how to configure the Dead Letter Channel
configuration using the DSL
RouteBuilder builder = new RouteBuilder() {
public void configure() {
// using dead letter channel with a seda queue for errors
errorHandler(deadLetterChannel("seda:errors"));
// here is our route
from("seda:a").to("seda:b");
}
};
You can also configure the RedeliveryPolicy as this example shows
RouteBuilder builder = new RouteBuilder() {
public void configure() {
// configures dead letter channel to use seda queue for errors and use at
most 2 redelveries
// and exponential backoff
errorHandler(deadLetterChannel("seda:errors").maximumRedeliveries(2).useExponentialBackOff());
// here is our route
from("seda:a").to("seda:b");
}
};
359
CH AP T E R 10 - PAT T E R N A P P E N D I X
How can I modify the Exchange before redelivery?
In Camel 1.6.0 we added support directly in Dead Letter Channel to set a
Processor that is executed before each redelivery attempt.
When Dead Letter Channel is doing redeliver its possible to configure a
Processor that is executed just before every redelivery attempt. This can be
used for the situations where you need to alter the message before its
redelivered.
Here we configure the Dead Letter Channel to use our processor
MyRedeliveryProcessor to be executed before each redelivery.
// we configure our Dead Letter Channel to invoke
// MyRedeliveryProcessor before a redelivery is
// attempted. This allows us to alter the message before
errorHandler(deadLetterChannel("mock:error").maximumRedeliveries(5)
.onRedelivery(new MyRedeliverProcessor())
// setting delay to zero is just to make unit testing faster
.redeliveryDelay(0L));
And this is the processor MyRedeliveryProcessor where we alter the
message.
// This is our processor that is executed before every redelivery attempt
// here we can do what we want in the java code, such as altering the message
public class MyRedeliverProcessor implements Processor {
public void process(Exchange exchange) throws Exception {
// the message is being redelivered so we can alter it
// we just append the redelivery counter to the body
// you can of course do all kind of stuff instead
String body = exchange.getIn().getBody(String.class);
int count = exchange.getIn().getHeader(Exchange.REDELIVERY_COUNTER,
Integer.class);
exchange.getIn().setBody(body + count);
// the maximum redelivery was set to 5
int max = exchange.getIn().getHeader(Exchange.REDELIVERY_MAX_COUNTER,
Integer.class);
assertEquals(5, max);
}
}
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
360
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
▪ Error Handler
▪ Exception Clause
Guaranteed Delivery
Camel supports the Guaranteed Delivery from the EIP patterns using among
others the following components:
• File for using file systems as a persistent store of messages
• JMS when using persistent delivery (the default) for working with JMS
Queues and Topics for high performance, clustering and load
balancing
• JPA for using a database as a persistence layer, or use any of the
many other database component such as SQL, JDBC, iBATIS/MyBatis,
Hibernate
• HawtDB for a lightweight key-value persistent store
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
Message Bus
Camel supports the Message Bus from the EIP patterns. You could view
Camel as a Message Bus itself as it allows producers and consumers to be
decoupled.
361
CH AP T E R 10 - PAT T E R N A P P E N D I X
Folks often assume that a Message Bus is a JMS though so you may wish
to refer to the JMS component for traditional MOM support.
Also worthy of node is the XMPP component for supporting messaging over
XMPP (Jabber)
Of course there is also ESB product such as Apache ServiceMix which is a
full fledge message bus.
You can interact with Apache ServiceMix from Camel in many ways, but in
particular you can use the NMR or JBI component to access the ServiceMix
message bus directly.
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
Message Construction
EVENT MESSAGE
Camel supports the Event Message from the EIP patterns by supporting the
Exchange Pattern on a Message which can be set to InOnly to indicate a
oneway event message. Camel Components then implement this pattern
using the underlying transport or protocols.
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
362
The default behaviour of many Components is InOnly such as for JMS, File
or SEDA
Explicitly specifying InOnly
If you are using a component which defaults to InOut you can override the
Exchange Pattern for an endpoint using the pattern property.
foo:bar?exchangePattern=InOnly
From 2.0 onwards on Camel you can specify the Exchange Pattern using the
dsl.
from("mq:someQueue").
inOnly().
bean(Foo.class);
or you can invoke an endpoint with an explicit pattern
from("mq:someQueue").
inOnly("mq:AnotherQueue");
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
363
CH AP T E R 10 - PAT T E R N A P P E N D I X
Related
See the related Request Reply message.
REQUEST REPLY
Camel supports the Request Reply from the EIP patterns by supporting the
Exchange Pattern on a Message which can be set to InOut to indicate a
request/reply. Camel Components then implement this pattern using the
underlying transport or protocols.
For example when using JMS with InOut the component will by default
perform these actions
• create by default a temporary inbound queue
• set the JMSReplyTo destination on the request message
• set the JMSCorrelationID on the request message
• send the request message
• consume the response and associate the inbound message to the
request using the JMSCorrelationID (as you may be performing many
concurrent request/responses).
Explicitly specifying InOut
When consuming messages from JMS a Request-Reply is indicated by the
presence of the JMSReplyTo header.
You can explicitly force an endpoint to be in Request Reply mode by
setting the exchange pattern on the URI. e.g.
jms:MyQueue?exchangePattern=InOut
You can specify the exchange pattern in DSL rule or Spring configuration.
// Send to an endpoint using InOut
from("direct:testInOut").inOut("mock:result");
// Send to an endpoint using InOut
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
364
Related
See the related Event Message message
from("direct:testInOnly").inOnly("mock:result");
// Set the exchange pattern to InOut, then send it from direct:inOnly to mock:result
endpoint
from("direct:testSetToInOnlyThenTo").inOnly().to("mock:result");
from("direct:testSetToInOutThenTo").inOut().to("mock:result");
// Or we can pass the pattern as a parameter to the to() method
from("direct:testToWithInOnlyParam").to(ExchangePattern.InOnly, "mock:result");
from("direct:testToWithInOutParam").to(ExchangePattern.InOut, "mock:result");
from("direct:testToWithRobustInOnlyParam").to(ExchangePattern.RobustInOnly,
"mock:result");
// Set the exchange pattern to InOut, then send it on
from("direct:testSetExchangePatternInOnly")
.setExchangePattern(ExchangePattern.InOnly).to("mock:result");
<camelContext xmlns="http://camel.apache.org/schema/spring">
<!-- Send the exchange as InOnly -->
<route>
<from uri="direct:testInOut"/>
<inOut uri="mock:result"/>
</route>
<!-- Send the exchange as InOnly -->
<route>
<from uri="direct:testInOnly"/>
<inOnly uri="mock:result"/>
</route>
<!-- lets set the exchange pattern then send it on -->
<route>
<from uri="direct:testSetToInOnlyThenTo"/>
<setExchangePattern pattern="InOnly"/>
<to uri="mock:result"/>
</route>
<route>
<from uri="direct:testSetToInOutThenTo"/>
<setExchangePattern pattern="InOut"/>
<to uri="mock:result"/>
</route>
<route>
<from uri="direct:testSetExchangePatternInOnly"/>
<setExchangePattern pattern="InOnly"/>
<to uri="mock:result"/>
365
CH AP T E R 10 - PAT T E R N A P P E N D I X
</route>
<!-- Lets pass the pattern as an argument in the to element -->
<route>
<from uri="direct:testToWithInOnlyParam"/>
<to uri="mock:result" pattern="InOnly"/>
</route>
<route>
<from uri="direct:testToWithInOutParam"/>
<to uri="mock:result" pattern="InOut"/>
</route>
<route>
<from uri="direct:testToWithRobustInOnlyParam"/>
<to uri="mock:result" pattern="RobustInOnly"/>
</route>
</camelContext>
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
Correlation Identifier
Camel supports the Correlation Identifier from the EIP patterns by getting or
setting a header on a Message.
When working with the ActiveMQ or JMS components the correlation
identifier header is called JMSCorrelationID. You can add your own
correlation identifier to any message exchange to help correlate messages
together to a single conversation (or business process).
The use of a Correlation Identifier is key to working with the Camel
Business Activity Monitoring Framework and can also be highly useful when
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
366
testing with simulation or canned data such as with the Mock testing
framework
Some EIP patterns will spin off a sub message, and in those cases, Camel
will add a correlation id on the Exchange as a property with they key
Exchange.CORRELATION_ID, which links back to the source Exchange. For
example the Splitter, Multicast, Recipient List, and Wire Tap EIP does this.
See Also
• BAM
RETURN ADDRESS
Camel supports the Return Address from the EIP patterns by using the
JMSReplyTo header.
For example when using JMS with InOut the component will by default
return to the address given in JMSReplyTo.
Requestor Code
getMockEndpoint("mock:bar").expectedBodiesReceived("Bye World");
template.sendBodyAndHeader("direct:start", "World", "JMSReplyTo", "queue:bar");
Route Using the Fluent Builders
from("direct:start").to("activemq:queue:foo?preserveMessageQos=true");
from("activemq:queue:foo").transform(body().prepend("Bye "));
from("activemq:queue:bar?disableReplyTo=true").to("mock:bar");
Route Using the Spring XML Extensions
367
CH AP T E R 10 - PAT T E R N A P P E N D I X
<route>
<from uri="direct:start"/>
<to uri="activemq:queue:foo?preserveMessageQos=true"/>
</route>
<route>
<from uri="activemq:queue:foo"/>
<transform>
<simple>Bye ${in.body}</simple>
</transform>
</route>
<route>
<from uri="activemq:queue:bar?disableReplyTo=true"/>
<to uri="mock:bar"/>
</route>
For a complete example of this pattern, see this junit test case
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
MESSAGE ROUTING
Content Based Router
The Content Based Router from the EIP patterns allows you to route
messages to the correct destination based on the contents of the message
exchanges.
The following example shows how to route a request from an input seda:a
endpoint to either seda:b, seda:c or seda:d depending on the evaluation of
various Predicate expressions
Using the Fluent Builders
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
368
RouteBuilder builder = new RouteBuilder() {
public void configure() {
errorHandler(deadLetterChannel("mock:error"));
from("seda:a")
.choice()
.when(header("foo").isEqualTo("bar"))
.to("seda:b")
.when(header("foo").isEqualTo("cheese"))
.to("seda:c")
.otherwise()
.to("seda:d");
}
};
Using the Spring XML Extensions
<camelContext errorHandlerRef="errorHandler" xmlns="http://camel.apache.org/schema/
spring">
<route>
<from uri="seda:a"/>
<choice>
<when>
<xpath>$foo = 'bar'</xpath>
<to uri="seda:b"/>
</when>
<when>
<xpath>$foo = 'cheese'</xpath>
<to uri="seda:c"/>
</when>
<otherwise>
<to uri="seda:d"/>
</otherwise>
</choice>
</route>
</camelContext>
For further examples of this pattern in use you could look at the junit test
case
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
369
CH AP T E R 10 - PAT T E R N A P P E N D I X
Message Filter
The Message Filter from the EIP patterns allows you to filter messages
The following example shows how to create a Message Filter route
consuming messages from an endpoint called queue:a which if the
Predicate is true will be dispatched to queue:b
Using the Fluent Builders
RouteBuilder builder = new RouteBuilder() {
public void configure() {
errorHandler(deadLetterChannel("mock:error"));
from("seda:a")
.filter(header("foo").isEqualTo("bar"))
.to("seda:b");
}
};
You can of course use many different Predicate languages such as XPath,
XQuery, SQL or various Scripting Languages. Here is an XPath example
from("direct:start").
filter().xpath("/person[@name='James']").
to("mock:result");
Here is another example of using a bean to define the filter behavior
from("direct:start")
.filter().method(MyBean.class, "isGoldCustomer").to("mock:result").end()
.to("mock:end");
public static class MyBean {
public boolean isGoldCustomer(@Header("level") String level) {
return level.equals("gold");
}
}
Using the Spring XML Extensions
<camelContext errorHandlerRef="errorHandler" xmlns="http://camel.apache.org/schema/
spring">
<route>
<from uri="seda:a"/>
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
370
<filter>
<xpath>$foo = 'bar'</xpath>
<to uri="seda:b"/>
</filter>
</route>
</camelContext>
For further examples of this pattern in use you could look at the junit test
case
Using stop
Available as of Camel 2.0
Stop is a bit different than a message filter as it will filter out all messages
and end the route entirely (filter only applies to its child processor). Stop is
convenient to use in a Content Based Router when you for example need to
stop further processing in one of the predicates.
In the example below we do not want to route messages any further that
has the word Bye in the message body. Notice how we prevent this in the
when predicate by using the .stop().
from("direct:start")
.choice()
.when(body().contains("Hello")).to("mock:hello")
.when(body().contains("Bye")).to("mock:bye").stop()
.otherwise().to("mock:other")
.end()
.to("mock:result");
Knowing if Exchange was filtered or not
Available as of Camel 2.5
The Message Filter EIP will add a property on the Exchange which states if
it was filtered or not.
The property has the key Exchannge.FILTER_MATCHED which has the
String value of CamelFilterMatched. Its value is a boolean indicating true or
false. If the value is true then the Exchange was routed in the filter block.
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
371
CH AP T E R 10 - PAT T E R N A P P E N D I X
filtered endpoint required inside </filter> tag
make sure you put the endpoint you want to filter (<to
uri="seda:b"/>, etc.) before the closing </filter> tag or the filter
will not be applied (in 2.8+, omitting this will result in an error)
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
DYNAMIC ROUTER
The Dynamic Router from the EIP patterns allows you to route messages
while avoiding the dependency of the router on all possible destinations
while maintaining its efficiency.
In Camel 2.5 we introduced a dynamicRouter in the DSL which is like a
dynamic Routing Slip which evaluates the slip on-the-fly.
Options
Name
Default
Value
Description
uriDelimiter
,
Delimiter used if the Expression returned multiple endpoints.
ignoreInvalidEndpoints
false
If an endpoint uri could not be resolved, should it be ignored. Otherwise Camel will thrown an
exception stating the endpoint uri is not valid.
Dynamic Router in Camel 2.5 onwards
From Camel 2.5 the Dynamic Router will set a property
(Exchange.SLIP_ENDPOINT) on the Exchange which contains the current
endpoint as it advanced though the slip. This allows you to know how far we
have processed in the slip. (It's a slip because the Dynamic Router
implementation is based on top of Routing Slip).
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
372
Beware
You must ensure the expression used for the dynamicRouter such
as a bean, will return null to indicate the end. Otherwise the
dynamicRouter will keep repeating endlessly.
Java DSL
In Java DSL you can use the routingSlip as shown below:
from("direct:start")
// use a bean as the dynamic router
.dynamicRouter(bean(DynamicRouterTest.class, "slip"));
Which will leverage a Bean to compute the slip on-the-fly, which could be
implemented as follows:
/**
* Use this method to compute dynamic where we should route next.
*
* @param body the message body
* @return endpoints to go, or <tt>null</tt> to indicate the end
*/
public String slip(String body) {
bodies.add(body);
invoked++;
if (invoked == 1) {
return "mock:a";
} else if (invoked == 2) {
return "mock:b,mock:c";
} else if (invoked == 3) {
return "direct:foo";
} else if (invoked == 4) {
return "mock:result";
}
// no more so return null
return null;
}
Mind that this example is only for show and tell. The current implementation
is not thread safe. You would have to store the state on the Exchange, to
ensure thread safety.
373
CH AP T E R 10 - PAT T E R N A P P E N D I X
Spring XML
The same example in Spring XML would be:
<bean id="mySlip" class="org.apache.camel.processor.DynamicRouterTest"/>
<camelContext xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="direct:start"/>
<dynamicRouter>
<!-- use a method call on a bean as dynamic router -->
<method ref="mySlip" method="slip"/>
</dynamicRouter>
</route>
<route>
<from uri="direct:foo"/>
<transform><constant>Bye World</constant></transform>
<to uri="mock:foo"/>
</route>
</camelContext>
@DynamicRouter annotation
You can also use the @DynamicRouter annotation, for example the Camel 2.4
example below could be written as follows. The route method would then be
invoked repeatedly as the message is processed dynamically. The idea is to
return the next endpoint uri where to go. Return null to indicate the end. You
can return multiple endpoints if you like, just as the Routing Slip, where each
endpoint is separated by a delimiter.
public class MyDynamicRouter {
@Consume(uri = "activemq:foo")
@DynamicRouter
public String route(@XPath("/customer/id") String customerId, @Header("Location")
String location, Document body) {
// query a database to find the best match of the endpoint based on the input
parameteres
// return the next endpoint uri, where to go. Return null to indicate the end.
}
}
Dynamic Router in Camel 2.4 or older
The simplest way to implement this is to use the RecipientList Annotation on
a Bean method to determine where to route the message.
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
374
public class MyDynamicRouter {
@Consume(uri = "activemq:foo")
@RecipientList
public List<String> route(@XPath("/customer/id") String customerId,
@Header("Location") String location, Document body) {
// query a database to find the best match of the endpoint based on the input
parameteres
...
}
}
In the above we can use the Parameter Binding Annotations to bind different
parts of the Message to method parameters or use an Expression such as
using XPath or XQuery.
The method can be invoked in a number of ways as described in the Bean
Integration such as
• POJO Producing
• Spring Remoting
• Bean component
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
Recipient List
The Recipient List from the EIP patterns allows you to route messages to a
number of dynamically specified recipients.
The recipients will receive a copy of the same Exchange and Camel will
execute them sequentially.
375
CH AP T E R 10 - PAT T E R N A P P E N D I X
Options
Name
Default
Value
Description
delimiter
,
Delimiter used if the Expression returned multiple endpoints.
strategyRef
Â
Refers to an AggregationStrategy to be used to assemble the replies from the recipients, into a
single outgoing message from the Recipient List. By default Camel will use the last reply as the
outgoing message.
parallelProcessing
false
Camel 2.2: If enables then sending messages to the recipients occurs concurrently. Note the
caller thread will still wait until all messages has been fully processed, before it continues. Its only
the sending and processing the replies from the recipients which happens concurrently.
executorServiceRef
Â
Camel 2.2: Refers to a custom Thread Pool to be used for parallel processing. Notice if you set this
option, then parallel processing is automatic implied, and you do not have to enable that option as
well.
stopOnException
false
Camel 2.2: Whether or not to stop continue processing immediately when an exception occurred.
If disable, then Camel will send the message to all recipients regardless if one of them failed. You
can deal with exceptions in the AggregationStrategy class where you have full control how to
handle that.
ignoreInvalidEndpoints
false
Camel 2.3: If an endpoint uri could not be resolved, should it be ignored. Otherwise Camel will
thrown an exception stating the endpoint uri is not valid.
streaming
false
Camel 2.5: If enabled then Camel will process replies out-of-order, eg in the order they come
back. If disabled, Camel will process replies in the same order as the Expression specified.
timeout
Â
Camel 2.5: Sets a total timeout specified in millis. If the Recipient List hasn't been able to send
and process all replies within the given timeframe, then the timeout triggers and the Recipient List
breaks out and continues. Notice if you provide a TimeoutAwareAggregationStrategy then the
timeout method is invoked before breaking out.
onPrepareRef
Â
Camel 2.8: Refers to a custom Processor to prepare the copy of the Exchange each recipient will
receive. This allows you to do any custom logic, such as deep-cloning the message payload if
that's needed etc.
Static Recipient List
The following example shows how to route a request from an input queue:a
endpoint to a static list of destinations
Using Annotations
You can use the RecipientList Annotation on a POJO to create a Dynamic
Recipient List. For more details see the Bean Integration.
Using the Fluent Builders
RouteBuilder builder = new RouteBuilder() {
public void configure() {
errorHandler(deadLetterChannel("mock:error"));
from("seda:a")
.multicast().to("seda:b", "seda:c", "seda:d");
}
};
Using the Spring XML Extensions
<camelContext errorHandlerRef="errorHandler" xmlns="http://camel.apache.org/schema/
spring">
<route>
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
376
<from uri="seda:a"/>
<multicast>
<to uri="seda:b"/>
<to uri="seda:c"/>
<to uri="seda:d"/>
</multicast>
</route>
</camelContext>
Dynamic Recipient List
Usually one of the main reasons for using the Recipient List pattern is that
the list of recipients is dynamic and calculated at runtime. The following
example demonstrates how to create a dynamic recipient list using an
Expression (which in this case it extracts a named header value dynamically)
to calculate the list of endpoints which are either of type Endpoint or are
converted to a String and then resolved using the endpoint URIs.
Using the Fluent Builders
RouteBuilder builder = new RouteBuilder() {
public void configure() {
errorHandler(deadLetterChannel("mock:error"));
from("seda:a")
.recipientList(header("foo"));
}
};
The above assumes that the header contains a list of endpoint URIs. The
following takes a single string header and tokenizes it
from("direct:a").recipientList(
header("recipientListHeader").tokenize(","));
Iteratable value
The dynamic list of recipients that are defined in the header must be
iteratable such as:
▪ java.util.Collection
▪ java.util.Iterator
▪ arrays
▪ org.w3c.dom.NodeList
▪ Camel 1.6.0: a single String with values separated with comma
▪ any other type will be regarded as a single value
377
CH AP T E R 10 - PAT T E R N A P P E N D I X
Using the Spring XML Extensions
<camelContext errorHandlerRef="errorHandler" xmlns="http://camel.apache.org/schema/
spring">
<route>
<from uri="seda:a"/>
<recipientList>
<xpath>$foo</xpath>
</recipientList>
</route>
</camelContext>
For further examples of this pattern in use you could look at one of the junit
test case
Using delimiter in Spring XML
Available as of Camel 1.6.0
In Spring DSL you can set the delimiter attribute for setting a delimiter to
be used if the header value is a single String with multiple separated
endpoints. By default Camel uses comma as delimiter, but this option lets
you specify a customer delimiter to use instead.
<route>
<from uri="direct:a" />
<!-- use comma as a delimiter for String based values -->
<recipientList delimiter=",">
<header>myHeader</header>
</recipientList>
</route>
So if myHeader contains a String with the value "activemq:queue:foo,
activemq:topic:hello , log:bar" then Camel will split the String using
the delimiter given in the XML that was comma, resulting into 3 endpoints to
send to. You can use spaces between the endpoints as Camel will trim the
value when it lookup the endpoint to send to.
Note: In Java DSL you use the tokenizer to archive the same. The route
above in Java DSL:
from("direct:a").recipientList(header("myHeader").tokenize(","));
In Camel 2.1 its a bit easier as you can pass in the delimiter as 2nd
parameter:
from("direct:a").recipientList(header("myHeader"), "#");
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
378
Sending to multiple recipients in parallel
Available as of Camel 2.2
The Recipient List now supports parallelProcessing that for example
Splitter also supports. You can use it to use a thread pool to have concurrent
tasks sending the Exchange to multiple recipients concurrently.
from("direct:a").recipientList(header("myHeader")).parallelProcessing();
And in Spring XML its an attribute on the recipient list tag.
<route>
<from uri="direct:a"/>
<recipientList parallelProcessing="true">
<header>myHeader</header>
</recipientList>
</route>
Stop continuing in case one recipient failed
Available as of Camel 2.2
The Recipient List now supports stopOnException that for example
Splitter also supports. You can use it to stop sending to any further recipients
in case any recipient failed.
from("direct:a").recipientList(header("myHeader")).stopOnException();
And in Spring XML its an attribute on the recipient list tag.
<route>
<from uri="direct:a"/>
<recipientList stopOnException="true">
<header>myHeader</header>
</recipientList>
</route>
Note: You can combine parallelProcessing and stopOnException and
have them both true.
Ignore invalid endpoints
Available as of Camel 2.3
The Recipient List now supports ignoreInvalidEndpoints which the
Routing Slip also supports. You can use it to skip endpoints which is invalid.
379
CH AP T E R 10 - PAT T E R N A P P E N D I X
from("direct:a").recipientList(header("myHeader")).ignoreInvalidEndpoints();
And in Spring XML its an attribute on the recipient list tag.
<route>
<from uri="direct:a"/>
<recipientList ignoreInvalidEndpoints="true">
<header>myHeader</header>
</recipientList>
</route>
Then lets say the myHeader contains the following two endpoints
direct:foo,xxx:bar. The first endpoint is valid and works. However the 2nd
is invalid and will just be ignored. Camel logs at INFO level about, so you can
see why the endpoint was invalid.
Using custom AggregationStrategy
Available as of Camel 2.2
You can now use you own AggregationStrategy with the Recipient List.
However its not that often you need that. What its good for is that in case
you are using Request Reply messaging then the replies from the recipient
can be aggregated. By default Camel uses UseLatestAggregationStrategy
which just keeps that last received reply. What if you must remember all the
bodies that all the recipients send back, then you can use your own custom
aggregator that keeps those. Its the same principle as with the Aggregator
EIP so check it out for details.
from("direct:a")
.recipientList(header("myHeader")).aggregationStrategy(new
MyOwnAggregationStrategy())
.to("direct:b");
And in Spring XML its an attribute on the recipient list tag.
<route>
<from uri="direct:a"/>
<recipientList strategyRef="myStrategy">
<header>myHeader</header>
</recipientList>
<to uri="direct:b"/>
</route>
<bean id="myStrategy" class="com.mycompany.MyOwnAggregationStrategy"/>
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
380
Using custom thread pool
Available as of Camel 2.2
A thread pool is only used for parallelProcessing. You supply your own
custom thread pool via the ExecutorServiceStrategy (see Camel's
Threading Model), the same way you would do it for the
aggregationStrategy. By default Camel uses a thread pool with 10 threads
(subject to change in a future version).
Using method call as recipient list
You can use a Bean to provide the recipients, for example:
from("activemq:queue:test").recipientList().method(MessageRouter.class, "routeTo");
And then MessageRouter:
public class MessageRouter {
public String routeTo() {
String queueName = "activemq:queue:test2";
return queueName;
}
}
When you use a Bean then do not also use the @RecipientList annotation
as this will in fact add yet another recipient list, so you end up having two.
Do not do like this.
public class MessageRouter {
@RecipientList
public String routeTo() {
String queueName = "activemq:queue:test2";
return queueName;
}
}
Well you should only do like that above (using @RecipientList) if you route
just route to a Bean which you then want to act as a recipient list.
So the original route can be changed to:
from("activemq:queue:test").bean(MessageRouter.class, "routeTo");
Which then would invoke the routeTo method and detect its annotated with
@RecipientList and then act accordingly as if it was a recipient list EIP.
381
CH AP T E R 10 - PAT T E R N A P P E N D I X
Using timeout
Available as of Camel 2.5
If you use parallelProcessing then you can configure a total timeout
value in millis. Camel will then process the messages in parallel until the
timeout is hit. This allows you to continue processing if one message is slow.
For example you can set a timeout value of 20 sec.
For example in the unit test below you can see we multicast the message
to 3 destinations. We have a timeout of 2 seconds, which means only the last
two messages can be completed within the timeframe. This means we will
only aggregate the last two which yields a result aggregation which outputs
"BC".
from("direct:start")
.multicast(new AggregationStrategy() {
public Exchange aggregate(Exchange oldExchange, Exchange newExchange) {
if (oldExchange == null) {
return newExchange;
}
String body = oldExchange.getIn().getBody(String.class);
oldExchange.getIn().setBody(body +
newExchange.getIn().getBody(String.class));
return oldExchange;
}
})
.parallelProcessing().timeout(250).to("direct:a", "direct:b", "direct:c")
// use end to indicate end of multicast route
.end()
.to("mock:result");
from("direct:a").delay(500).to("mock:A").setBody(constant("A"));
from("direct:b").to("mock:B").setBody(constant("B"));
from("direct:c").to("mock:C").setBody(constant("C"));
By default if a timeout occurs the AggregationStrategy is not invoked.
However you can implement a specialized version
public interface TimeoutAwareAggregationStrategy extends AggregationStrategy {
/**
* A timeout occurred
*
* @param oldExchange the oldest exchange (is <tt>null</tt> on first aggregation
as we only have the new exchange)
* @param index
the index
* @param total
the total
* @param timeout
the timeout value in millis
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
382
Timeout in other EIPs
This timeout feature is also supported by Splitter and both
multicast and recipientList.
*/
void timeout(Exchange oldExchange, int index, int total, long timeout);
This allows you to deal with the timeout in the AggregationStrategy if you
really need to.
Using onPrepare to execute custom logic when preparing messages
Available as of Camel 2.8
See details at Multicast
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
Splitter
The Splitter from the EIP patterns allows you split a message into a number
of pieces and process them individually
As of Camel 2.0, you need to specify a Splitter as split(). In earlier
versions of Camel, you need to use splitter().
Options
Name
383
Default
Value
Description
CH AP T E R 10 - PAT T E R N A P P E N D I X
Timeout is total
The timeout is total, which means that after X time, Camel will
aggregate the messages which has completed within the
timeframe. The remainders will be cancelled. Camel will also only
invoke the timeout method in the
TimeoutAwareAggregationStrategy once, for the first index which
caused the timeout.
strategyRef
Â
Refers to an AggregationStrategy to be used to assemble the replies from the sub-messages, into a
single outgoing message from the Splitter. See the section titled What does the splitter return below for
whats used by default.
parallelProcessing
false
If enables then processing the sub-messages occurs concurrently. Note the caller thread will still wait
until all sub-messages has been fully processed, before it continues.
executorServiceRef
Â
Refers to a custom Thread Pool to be used for parallel processing. Notice if you set this option, then
parallel processing is automatic implied, and you do not have to enable that option as well.
stopOnException
false
Camel 2.2: Whether or not to stop continue processing immediately when an exception occurred. If
disable, then Camel continue splitting and process the sub-messages regardless if one of them failed.
You can deal with exceptions in the AggregationStrategy class where you have full control how to
handle that.
streaming
false
If enabled then Camel will split in a streaming fashion, which means it will split the input message in
chunks. This reduces the memory overhead. For example if you split big messages its recommended to
enable streaming. If streaming is enabled then the sub-message replies will be aggregated out-of-order,
eg in the order they come back. If disabled, Camel will process sub-message replies in the same order
as they where splitted.
timeout
Â
Camel 2.5: Sets a total timeout specified in millis. If the Recipient List hasn't been able to split and
process all replies within the given timeframe, then the timeout triggers and the Splitter breaks out and
continues. Notice if you provide a TimeoutAwareAggregationStrategy then the timeout method is
invoked before breaking out.
onPrepareRef
Â
Camel 2.8: Refers to a custom Processor to prepare the sub-message of the Exchange, before its
processed. This allows you to do any custom logic, such as deep-cloning the message payload if that's
needed etc.
Exchange properties
The following properties is set on each Exchange that are split:
header
type
description
CamelSplitIndex
int
Camel 2.0: A split counter that increases
for each Exchange being split. The
counter starts from 0.
CamelSplitSize
int
Camel 2.0: The total number of
Exchanges that was splitted. This header
is not applied for stream based splitting.
CamelSplitComplete
boolean
Camel 2.4: Whether or not this
Exchange is the last.
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
384
Examples
The following example shows how to take a request from the queue:a
endpoint the split it into pieces using an Expression, then forward each piece
to queue:b
Using the Fluent Builders
RouteBuilder builder = new RouteBuilder() {
public void configure() {
errorHandler(deadLetterChannel("mock:error"));
from("seda:a")
.split(body(String.class).tokenize("\n"))
.to("seda:b");
}
};
The splitter can use any Expression language so you could use any of the
Languages Supported such as XPath, XQuery, SQL or one of the Scripting
Languages to perform the split. e.g.
from("activemq:my.queue").split(xpath("//foo/
bar")).convertBodyTo(String.class).to("file://some/directory")
Using the Spring XML Extensions
<camelContext errorHandlerRef="errorHandler" xmlns="http://camel.apache.org/schema/
spring">
<route>
<from uri="seda:a"/>
<split>
<xpath>/invoice/lineItems</xpath>
<to uri="seda:b"/>
</split>
</route>
</camelContext>
For further examples of this pattern in use you could look at one of the junit
test case
Using Tokenizer from Spring XML Extensions*
Avaiaible as of Camel 2.0
You can use the tokenizer expression in the Spring DSL to split bodies or
headers using a token. This is a common use-case, so we provided a special
tokenizer tag for this.
385
CH AP T E R 10 - PAT T E R N A P P E N D I X
In the sample below we split the body using a @ as separator. You can of
course use comma or space or even a regex pattern, also set regex=true.
<camelContext xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="direct:start"/>
<split>
<tokenize token="@"/>
<to uri="mock:result"/>
</split>
</route>
</camelContext>
Splitting the body in Spring XML is a bit harder as you need to use the Simple
language to dictate this
<split>
<simple>${body}</simple>
<to uri="mock:result"/>
</split>
What does the splitter return?
Camel 2.2 or older:
The Splitter will by default return the last splitted message.
Camel 2.3 and newer
The Splitter will by default return the original input message.
For all versions
You can override this by suppling your own strategy as an
AggregationStrategy. There is a sample on this page (Split aggregate
request/reply sample). Notice its the same strategy as the Aggregator
supports. This Splitter can be viewed as having a build in light weight
Aggregator.
Parallel execution of distinct 'parts'
If you want to execute all parts in parallel you can use special notation of
split() with two arguments, where the second one is a boolean flag if
processing should be parallel. e.g.
XPathBuilder xPathBuilder = new XPathBuilder("//foo/bar");
from("activemq:my.queue").split(xPathBuilder, true).to("activemq:my.parts");
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
386
In Camel 2.0 the boolean option has been refactored into a builder method
parallelProcessing so its easier to understand what the route does when
we use a method instead of true|false.
XPathBuilder xPathBuilder = new XPathBuilder("//foo/bar");
from("activemq:my.queue").split(xPathBuilder).parallelProcessing().to("activemq:my.parts");
Stream based
You can split streams by enabling the streaming mode using the streaming
builder method.
from("direct:streaming").split(body().tokenize(",")).streaming().to("activemq:my.parts");
You can also supply your custom splitter to use with streaming like this:
import static org.apache.camel.builder.ExpressionBuilder.beanExpression;
from("direct:streaming")
.split(beanExpression(new MyCustomIteratorFactory(), "iterator"))
.streaming().to("activemq:my.parts")
Specifying a custom aggregation strategy
Available as of Camel 2.0
This is specified similar to the Aggregator.
Specifying a custom ThreadPoolExecutor
You can customize the underlying ThreadPoolExecutor used in the parallel
splitter. In the Java DSL try something like this:
XPathBuilder xPathBuilder = new XPathBuilder("//foo/bar");
ExecutorService pool = ...
from("activemq:my.queue")
.split(xPathBuilder).parallelProcessing().executorService(pool)
.to("activemq:my.parts");
387
CH AP T E R 10 - PAT T E R N A P P E N D I X
Using streaming()
You can't use the streaming mode in conjunction with xpath. Xpath
requires the complete DOM XML document in memory.
Using a Pojo to do the splitting
As the Splitter can use any Expression to do the actual splitting we leverage
this fact and use a method expression to invoke a Bean to get the splitted
parts.
The Bean should return a value that is iterable such as:
java.util.Collection, java.util.Iterator or an array.
In the route we define the Expression as a method call to invoke our Bean
that we have registered with the id mySplitterBean in the Registry.
from("direct:body")
// here we use a POJO bean mySplitterBean to do the split of the payload
.split().method("mySplitterBean", "splitBody")
.to("mock:result");
from("direct:message")
// here we use a POJO bean mySplitterBean to do the split of the message
// with a certain header value
.split().method("mySplitterBean", "splitMessage")
.to("mock:result");
And the logic for our Bean is as simple as. Notice we use Camel Bean Binding
to pass in the message body as a String object.
public class MySplitterBean {
/**
* The split body method returns something that is iteratable such as a
java.util.List.
*
* @param body the payload of the incoming message
* @return a list containing each part splitted
*/
public List<String> splitBody(String body) {
// since this is based on an unit test you can of cause
// use different logic for splitting as Camel have out
// of the box support for splitting a String based on comma
// but this is for show and tell, since this is java code
// you have the full power how you like to split your messages
List<String> answer = new ArrayList<String>();
String[] parts = body.split(",");
for (String part : parts) {
answer.add(part);
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
388
}
return answer;
}
/**
* The split message method returns something that is iteratable such as a
java.util.List.
*
* @param header the header of the incoming message with the name user
* @param body the payload of the incoming message
* @return a list containing each part splitted
*/
public List<Message> splitMessage(@Header(value = "user") String header, @Body
String body) {
// we can leverage the Parameter Binding Annotations
// http://camel.apache.org/parameter-binding-annotations.html
// to access the message header and body at same time,
// then create the message that we want, splitter will
// take care rest of them.
// *NOTE* this feature requires Camel version >= 1.6.1
List<Message> answer = new ArrayList<Message>();
String[] parts = header.split(",");
for (String part : parts) {
DefaultMessage message = new DefaultMessage();
message.setHeader("user", part);
message.setBody(body);
answer.add(message);
}
return answer;
}
}
Split aggregate request/reply sample
This sample shows how you can split an Exchange, process each splitted
message, aggregate and return a combined response to the original caller
using request/reply.
The route below illustrates this and how the split supports a
aggregationStrategy to hold the in progress processed messages:
// this routes starts from the direct:start endpoint
// the body is then splitted based on @ separator
// the splitter in Camel supports InOut as well and for that we need
// to be able to aggregate what response we need to send back, so we provide our
// own strategy with the class MyOrderStrategy.
from("direct:start")
.split(body().tokenize("@"), new MyOrderStrategy())
// each splitted message is then send to this bean where we can process it
.to("bean:MyOrderService?method=handleOrder")
389
CH AP T E R 10 - PAT T E R N A P P E N D I X
// this is important to end the splitter route as we do not want to do more
routing
// on each splitted message
.end()
// after we have splitted and handled each message we want to send a single
combined
// response back to the original caller, so we let this bean build it for us
// this bean will receive the result of the aggregate strategy: MyOrderStrategy
.to("bean:MyOrderService?method=buildCombinedResponse")
And the OrderService bean is as follows:
public static class MyOrderService {
private static int counter;
/**
* We just handle the order by returning a id line for the order
*/
public String handleOrder(String line) {
LOG.debug("HandleOrder: " + line);
return "(id=" + ++counter + ",item=" + line + ")";
}
/**
* We use the same bean for building the combined response to send
* back to the original caller
*/
public String buildCombinedResponse(String line) {
LOG.debug("BuildCombinedResponse: " + line);
return "Response[" + line + "]";
}
}
And our custom aggregationStrategy that is responsible for holding the in
progress aggregated message that after the splitter is ended will be sent to
the buildCombinedResponse method for final processing before the
combined response can be returned to the waiting caller.
/**
* This is our own order aggregation strategy where we can control
* how each splitted message should be combined. As we do not want to
* loos any message we copy from the new to the old to preserve the
* order lines as long we process them
*/
public static class MyOrderStrategy implements AggregationStrategy {
public Exchange aggregate(Exchange oldExchange, Exchange newExchange) {
// put order together in old exchange by adding the order from new exchange
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
390
if (oldExchange == null) {
// the first time we aggregate we only have the new exchange,
// so we just return it
return newExchange;
}
String orders = oldExchange.getIn().getBody(String.class);
String newLine = newExchange.getIn().getBody(String.class);
LOG.debug("Aggregate old orders: " + orders);
LOG.debug("Aggregate new order: " + newLine);
// put orders together separating by semi colon
orders = orders + ";" + newLine;
// put combined order back on old to preserve it
oldExchange.getIn().setBody(orders);
// return old as this is the one that has all the orders gathered until now
return oldExchange;
}
}
So lets run the sample and see how it works.
We send an Exchange to the direct:start endpoint containing a IN body with
the String value: A@B@C. The flow is:
HandleOrder: A
HandleOrder: B
Aggregate old orders: (id=1,item=A)
Aggregate new order: (id=2,item=B)
HandleOrder: C
Aggregate old orders: (id=1,item=A);(id=2,item=B)
Aggregate new order: (id=3,item=C)
BuildCombinedResponse: (id=1,item=A);(id=2,item=B);(id=3,item=C)
Response to caller: Response[(id=1,item=A);(id=2,item=B);(id=3,item=C)]
Stop processing in case of exception
Available as of Camel 2.1
The Splitter will by default continue to process the entire Exchange even in
case of one of the splitted message will thrown an exception during routing.
For example if you have an Exchange with 1000 rows that you split and route
each sub message. During processing of these sub messages an exception is
thrown at the 17th. What Camel does by default is to process the remainder
983 messages. You have the chance to remedy or handle this in the
AggregationStrategy.
But sometimes you just want Camel to stop and let the exception be
propagated back, and let the Camel error handler handle it. You can do this in
391
CH AP T E R 10 - PAT T E R N A P P E N D I X
Camel 2.1 by specifying that it should stop in case of an exception occurred.
This is done by the stopOnException option as shown below:
from("direct:start")
.split(body().tokenize(",")).stopOnException()
.process(new MyProcessor())
.to("mock:split");
And using XML DSL you specify it as follows:
<route>
<from uri="direct:start"/>
<split stopOnException="true">
<tokenize token=","/>
<process ref="myProcessor"/>
<to uri="mock:split"/>
</split>
</route>
Using onPrepare to execute custom logic when preparing messages
Available as of Camel 2.8
See details at Multicast
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
Aggregator
This applies for Camel version 2.3 or newer. If you use an older
version then use this Aggregator link instead.
The Aggregator from the EIP patterns allows you to combine a number of
messages together into a single message.
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
392
A correlation Expression is used to determine the messages which should
be aggregated together. If you want to aggregate all messages into a single
message, just use a constant expression. An AggregationStrategy is used to
combine all the message exchanges for a single correlation key into a single
message exchange.
Aggregator options
The aggregator supports the following options:
393
Option
Default
Description
correlationExpression
Â
Mandatory Expression which evaluates the correlation key to use for aggregation. The
Exchange which has the same correlation key is aggregated together. If the correlation key
could not be evaluated an Exception is thrown. You can disable this by using the
ignoreBadCorrelationKeys option.
aggregationStrategy
Â
Mandatory AggregationStrategy which is used to merge the incoming Exchange with the
existing already merged exchanges. At first call the oldExchange parameter is null. On
subsequent invocations the oldExchange contains the merged exchanges and
newExchange is of course the new incoming Exchange.
strategyRef
Â
A reference to lookup the AggregationStrategy in the Registry.
completionSize
Â
Number of messages aggregated before the aggregation is complete. This option can be
set as either a fixed value or using an Expression which allows you to evaluate a size
dynamically - will use Integer as result. If both are set Camel will fallback to use the fixed
value if the Expression result was null or 0.
completionTimeout
Â
Time in millis that an aggregated exchange should be inactive before its complete. This
option can be set as either a fixed value or using an Expression which allows you to
evaluate a timeout dynamically - will use Long as result. If both are set Camel will fallback
to use the fixed value if the Expression result was null or 0. You cannot use this option
together with completionInterval, only one of the two can be used.
completionInterval
Â
A repeating period in millis by which the aggregator will complete all current aggregated
exchanges. Camel has a background task which is triggered every period. You cannot use
this option together with completionTimeout, only one of them can be used.
completionPredicate
Â
A Predicate to indicate when an aggregated exchange is complete.
completionFromBatchConsumer
false
This option is if the exchanges are coming from a Batch Consumer. Then when enabled the
Aggregator2 will use the batch size determined by the Batch Consumer in the message
header CamelBatchSize. See more details at Batch Consumer. This can be used to
aggregate all files consumed from a File endpoint in that given poll.
eagerCheckCompletion
false
Whether or not to eager check for completion when a new incoming Exchange has been
received. This option influences the behavior of the completionPredicate option as the
Exchange being passed in changes accordingly. When false the Exchange passed in the
Predicate is the aggregated Exchange which means any information you may store on the
aggregated Exchange from the AggregationStrategy is available for the Predicate. When
true the Exchange passed in the Predicate is the incoming Exchange, which means you
can access data from the incoming Exchange.
groupExchanges
false
If enabled then Camel will group all aggregated Exchanges into a single combined
org.apache.camel.impl.GroupedExchange holder class that holds all the aggregated
Exchanges. And as a result only one Exchange is being sent out from the aggregator. Can
be used to combine many incoming Exchanges into a single output Exchange without
coding a custom AggregationStrategy yourself.
ignoreInvalidCorrelationKeys
false
Whether or not to ignore correlation keys which could not be evaluated to a value. By
default Camel will throw an Exception, but you can enable this option and ignore the
situation instead.
closeCorrelationKeyOnCompletion
Â
Whether or not too late Exchanges should be accepted or not. You can enable this to
indicate that if a correlation key has already been completed, then any new exchanges
with the same correlation key be denied. Camel will then throw a
closedCorrelationKeyException exception. When using this option you pass in a
integer which is a number for a LRUCache which keeps that last X number of closed
correlation keys. You can pass in 0 or a negative value to indicate a unbounded cache. By
passing in a number you are ensured that cache won't grow too big if you use a log of
different correlation keys.
discardOnCompletionTimeout
false
Camel 2.5: Whether or not exchanges which complete due to a timeout should be
discarded. If enabled then when a timeout occurs the aggregated message will not be sent
out but dropped (discarded).
CH AP T E R 10 - PAT T E R N A P P E N D I X
aggregationRepository
Â
Allows you to plugin you own implementation of
org.apache.camel.spi.AggregationRepository which keeps track of the current inflight
aggregated exchanges. Camel uses by default a memory based implementation.
aggregationRepositoryRef
Â
Reference to lookup a aggregationRepository in the Registry.
parallelProcessing
false
When aggregated are completed they are being send out of the aggregator. This option
indicates whether or not Camel should use a thread pool with multiple threads for
concurrency. If no custom thread pool has been specified then Camel creates a default pool
with 10 concurrent threads.
executorService
Â
If using parallelProcessing you can specify a custom thread pool to be used. In fact also
if you are not using parallelProcessing this custom thread pool is used to send out
aggregated exchanges as well.
executorServiceRef
Â
Reference to lookup a executorService in the Registry
Exchange Properties
The following properties are set on each aggregated Exchange:
header
type
description
CamelAggregatedSize
int
The total number of Exchanges aggregated into this combined Exchange.
CamelAggregatedCompletedBy
String
Indicator how the aggregation was completed as a value of either: predicate, size, consumer,
timeout or interval.
About AggregationStrategy
The AggregationStrategy is used for aggregating the old (lookup by its
correlation id) and the new exchanges together into a single exchange.
Possible implementations include performing some kind of combining or
delta processing, such as adding line items together into an invoice or just
using the newest exchange and removing old exchanges such as for state
tracking or market data prices; where old values are of little use.
Notice the aggregation strategy is a mandatory option and must be
provided to the aggregator.
About completion
When aggregation Exchanges at some point you need to indicate that the
aggregated exchanges is complete, so they can be send out of the
aggregator. Camel allows you to indicate completion in various ways as
follows:
▪ completionTimeout - Is an inactivity timeout in which is triggered if
no new exchanges have been aggregated for that particular
correlation key within the period.
▪ completionInterval - Once every X period all the current aggregated
exchanges are completed.
▪ completionSize - Is a number indicating that after X aggregated
exchanges it's complete.
▪ completionPredicate - Runs a Predicate when a new exchange is
aggregated to determine if we are complete or not
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
394
▪ completionFromBatchConsumer - Special option for Batch Consumer
which allows you to complete when all the messages from the batch
has been aggregated. |
Notice that all the completion ways are per correlation key. And you can
combine them in any way you like. It's basically the first which triggers that
wins. So you can use a completion size together with a completion timeout.
Only completionTimeout and completionInterval cannot be used at the same
time.
Notice the completion is a mandatory option and must be provided to the
aggregator. If not provided Camel will thrown an Exception on startup.
Persistent AggregationRepository
The aggregator provides a pluggable repository which you can implement
your own org.apache.camel.spi.AggregationRepository.
If you need persistent repository then you can use either Camel HawtDB or
jdbc-aggregationrepository components.
Examples
See some examples from the old Aggregator which is somewhat similar to
this new aggregator.
Using completionTimeout
In this example we want to aggregate all incoming messages and after 3
seconds of inactivity we want the aggregation to complete. This is done
using the completionTimeout option as shown:
from("direct:start")
// aggregate all exchanges correlated by the id header.
// Aggregate them using the BodyInAggregatingStrategy strategy which
// and after 3 seconds of inactivity them timeout and complete the aggregation
// and send it to mock:aggregated
.aggregate(header("id"), new BodyInAggregatingStrategy()).completionTimeout(3000)
.to("mock:aggregated");
And the same example using Spring XML:
<camelContext xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="direct:start"/>
<aggregate strategyRef="aggregatorStrategy" completionTimeout="3000">
<correlationExpression>
395
CH AP T E R 10 - PAT T E R N A P P E N D I X
Setting options in Spring XML
Many of the options are configurable as attributes on the
<aggregate> tag when using Spring XML.
<simple>header.id</simple>
</correlationExpression>
<to uri="mock:aggregated"/>
</aggregate>
</route>
</camelContext>
<bean id="aggregatorStrategy"
class="org.apache.camel.processor.BodyInAggregatingStrategy"/>
Using completionSize
In this example we want to aggregate all incoming messages and when we
have 3 messages aggregated (in the same correlation group) we want the
aggregation to complete. This is done using the completionSize option as
shown:
from("direct:start")
// aggregate all exchanges correlated by the id header.
// Aggregate them using the BodyInAggregatingStrategy strategy which
// and after 3 messages has been aggregated then complete the aggregation
// and send it to mock:aggregated
.aggregate(header("id"), new BodyInAggregatingStrategy()).completionSize(3)
.to("mock:aggregated");
And the same example using Spring XML:
<camelContext xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="direct:start"/>
<aggregate strategyRef="aggregatorStrategy" completionSize="3">
<correlationExpression>
<simple>header.id</simple>
</correlationExpression>
<to uri="mock:aggregated"/>
</aggregate>
</route>
</camelContext>
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
396
<bean id="aggregatorStrategy"
class="org.apache.camel.processor.BodyInAggregatingStrategy"/>
Using completionPredicate
In this example we want to aggregate all incoming messages and use a
Predicate to determine when we are complete. The Predicate can be
evaluated using either the aggregated exchange (default) or the incoming
exchange. We will so both situations as examples. We start with the default
situation as shown:
from("direct:start")
// aggregate all exchanges correlated by the id header.
// Aggregate them using the BodyInAggregatingStrategy strategy which
// and when the aggregated body contains A+B+C then complete the aggregation
// and send it to mock:aggregated
.aggregate(header("id"), new
BodyInAggregatingStrategy()).completionPredicate(body().contains("A+B+C"))
.to("mock:aggregated");
And the same example using Spring XML:
<camelContext xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="direct:start"/>
<aggregate strategyRef="aggregatorStrategy">
<correlationExpression>
<simple>header.id</simple>
</correlationExpression>
<completionPredicate>
<simple>${body} contains 'A+B+C'</simple>
</completionPredicate>
<to uri="mock:aggregated"/>
</aggregate>
</route>
</camelContext>
<bean id="aggregatorStrategy"
class="org.apache.camel.processor.BodyInAggregatingStrategy"/>
And the other situation where we use the eagerCheckCompletion option to
tell Camel to use the incoming Exchange. Notice how we can just test in the
completion predicate that the incoming message is the END message:
from("direct:start")
// aggregate all exchanges correlated by the id header.
397
CH AP T E R 10 - PAT T E R N A P P E N D I X
// Aggregate them using the BodyInAggregatingStrategy strategy
// do eager checking which means the completion predicate will use the incoming
exchange
// which allows us to trigger completion when a certain exchange arrived which is
the
// END message
.aggregate(header("id"), new BodyInAggregatingStrategy())
.eagerCheckCompletion().completionPredicate(body().isEqualTo("END"))
.to("mock:aggregated");
And the same example using Spring XML:
<camelContext xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="direct:start"/>
<aggregate strategyRef="aggregatorStrategy" eagerCheckCompletion="true">
<correlationExpression>
<simple>header.id</simple>
</correlationExpression>
<completionPredicate>
<simple>${body} == 'END'</simple>
</completionPredicate>
<to uri="mock:aggregated"/>
</aggregate>
</route>
</camelContext>
<bean id="aggregatorStrategy"
class="org.apache.camel.processor.BodyInAggregatingStrategy"/>
Using dynamic completionTimeout
In this example we want to aggregate all incoming messages and after a
period of inactivity we want the aggregation to complete. The period should
be computed at runtime based on the timeout header in the incoming
messages. This is done using the completionTimeout option as shown:
from("direct:start")
// aggregate all exchanges correlated by the id header.
// Aggregate them using the BodyInAggregatingStrategy strategy which
// and the timeout header contains the timeout in millis of inactivity them
timeout and complete the aggregation
// and send it to mock:aggregated
.aggregate(header("id"), new
BodyInAggregatingStrategy()).completionTimeout(header("timeout"))
.to("mock:aggregated");
And the same example using Spring XML:
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
398
<camelContext xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="direct:start"/>
<aggregate strategyRef="aggregatorStrategy">
<correlationExpression>
<simple>header.id</simple>
</correlationExpression>
<completionTimeout>
<header>timeout</header>
</completionTimeout>
<to uri="mock:aggregated"/>
</aggregate>
</route>
</camelContext>
<bean id="aggregatorStrategy"
class="org.apache.camel.processor.BodyInAggregatingStrategy"/>
Note: You can also add a fixed timeout value and Camel will fallback to use
this value if the dynamic value was null or 0.
Using dynamic completionSize
In this example we want to aggregate all incoming messages based on a
dynamic size per correlation key. The size is computed at runtime based on
the mySize header in the incoming messages. This is done using the
completionSize option as shown:
from("direct:start")
// aggregate all exchanges correlated by the id header.
// Aggregate them using the BodyInAggregatingStrategy strategy which
// and the header mySize determines the number of aggregated messages should
trigger the completion
// and send it to mock:aggregated
.aggregate(header("id"), new
BodyInAggregatingStrategy()).completionSize(header("mySize"))
.to("mock:aggregated");
And the same example using Spring XML:
<camelContext xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="direct:start"/>
<aggregate strategyRef="aggregatorStrategy">
<correlationExpression>
<simple>header.id</simple>
</correlationExpression>
<completionSize>
399
CH AP T E R 10 - PAT T E R N A P P E N D I X
<header>mySize</header>
</completionSize>
<to uri="mock:aggregated"/>
</aggregate>
</route>
</camelContext>
<bean id="aggregatorStrategy"
class="org.apache.camel.processor.BodyInAggregatingStrategy"/>
Note: You can also add a fixed size value and Camel will fallback to use this
value if the dynamic value was null or 0.
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
See also
▪
▪
▪
▪
▪
The Loan Broker Example which uses an aggregator
Blog post by Torsten Mielke about using the aggregator correctly.
The old Aggregator
HawtDB or SQL Component for persistence support
Aggregate Example for an example application
Resequencer
The Resequencer from the EIP patterns allows you to reorganise messages
based on some comparator. By default in Camel we use an Expression to
create the comparator; so that you can compare by a message header or the
body or a piece of a message etc.
Camel supports two resequencing algorithms:
• Batch resequencing collects messages into a batch, sorts the
messages and sends them to their output.
• Stream resequencing re-orders (continuous) message streams
based on the detection of gaps between messages.
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
400
Change in Camel 2.7
The <batch-config> and <stream-config> tags in XML DSL in the
Resequencer EIP must now be configured in the top, and not in the
bottom. So if you use those, then move them up just below the
<resequence> EIP starts in the XML. If you are using Camel older
than 2.7, then those configs should be at the bottom.
By default the Resequencer does not support duplicate messages and will
only keep the last message, in case a message arrives with the same
message expression. However in the batch mode you can enable it to allow
duplicates.
Batch Resequencing
The following example shows how to use the batch-processing resequencer
so that messages are sorted in order of the body() expression. That is
messages are collected into a batch (either by a maximum number of
messages per batch or using a timeout) then they are sorted in order and
then sent out to their output.
Using the Fluent Builders
from("direct:start")
.resequence().body()
.to("mock:result");
This is equvalent to
from("direct:start")
.resequence(body()).batch()
.to("mock:result");
The batch-processing resequencer can be further configured via the size()
and timeout() methods.
from("direct:start")
.resequence(body()).batch().size(300).timeout(4000L)
.to("mock:result")
This sets the batch size to 300 and the batch timeout to 4000 ms (by default,
the batch size is 100 and the timeout is 1000 ms). Alternatively, you can
provide a configuration object.
401
CH AP T E R 10 - PAT T E R N A P P E N D I X
from("direct:start")
.resequence(body()).batch(new BatchResequencerConfig(300, 4000L))
.to("mock:result")
So the above example will reorder messages from endpoint direct:a in order
of their bodies, to the endpoint mock:result.
Typically you'd use a header rather than the body to order things; or maybe a
part of the body. So you could replace this expression with
resequencer(header("mySeqNo"))
for example to reorder messages using a custom sequence number in the
header mySeqNo.
You can of course use many different Expression languages such as XPath,
XQuery, SQL or various Scripting Languages.
You can also use multiple expressions; so you could for example sort by
priority first then some other custom header
resequence(header("mySeqNo"), header("MyCustomerRating"))
Using the Spring XML Extensions
<camelContext id="camel" xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="direct:start" />
<resequence>
<simple>body</simple>
<to uri="mock:result" />
<!-batch-config can be ommitted for default (batch) resequencer settings
-->
<batch-config batchSize="300" batchTimeout="4000" />
</resequence>
</route>
</camelContext>
Allow Duplicates
Available as of Camel 2.4
In the batch mode, you can now allow duplicates. In Java DSL there is a
allowDuplicates() method and in Spring XML there is an
allowDuplicates=true attribute on the <batch-config/> you can use to
enable it.
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
402
Reverse
Available as of Camel 2.4
In the batch mode, you can now reverse the expression ordering. By
default the order is based on 0..9,A..Z, which would let messages with low
numbers be ordered first, and thus also also outgoing first. In some cases
you want to reverse order, which is now possible.
In Java DSL there is a reverse() method and in Spring XML there is an
reverse=true attribute on the <batch-config/> you can use to enable it.
Resequence JMS messages based on JMSPriority
Available as of Camel 2.4
It's now much easier to use the Resequencer to resequence messages
from JMS queues based on JMSPriority. For that to work you need to use
the two new options allowDuplicates and reverse.
from("jms:queue:foo")
// sort by JMSPriority by allowing duplicates (message can have same JMSPriority)
// and use reverse ordering so 9 is first output (most important), and 0 is last
// use batch mode and fire every 3th second
.resequence(header("JMSPriority")).batch().timeout(3000).allowDuplicates().reverse()
.to("mock:result");
Notice this is only possible in the batch mode of the Resequencer.
Stream Resequencing
The next example shows how to use the stream-processing resequencer.
Messages are re-ordered based on their sequence numbers given by a
seqnum header using gap detection and timeouts on the level of individual
messages.
Using the Fluent Builders
from("direct:start").resequence(header("seqnum")).stream().to("mock:result");
The stream-processing resequencer can be further configured via the
capacity() and timeout() methods.
from("direct:start")
.resequence(header("seqnum")).stream().capacity(5000).timeout(4000L)
.to("mock:result")
403
CH AP T E R 10 - PAT T E R N A P P E N D I X
This sets the resequencer's capacity to 5000 and the timeout to 4000 ms (by
default, the capacity is 100 and the timeout is 1000 ms). Alternatively, you
can provide a configuration object.
from("direct:start")
.resequence(header("seqnum")).stream(new StreamResequencerConfig(5000, 4000L))
.to("mock:result")
The stream-processing resequencer algorithm is based on the detection of
gaps in a message stream rather than on a fixed batch size. Gap detection in
combination with timeouts removes the constraint of having to know the
number of messages of a sequence (i.e. the batch size) in advance.
Messages must contain a unique sequence number for which a predecessor
and a successor is known. For example a message with the sequence
number 3 has a predecessor message with the sequence number 2 and a
successor message with the sequence number 4. The message sequence
2,3,5 has a gap because the sucessor of 3 is missing. The resequencer
therefore has to retain message 5 until message 4 arrives (or a timeout
occurs).
If the maximum time difference between messages (with successor/
predecessor relationship with respect to the sequence number) in a message
stream is known, then the resequencer's timeout parameter should be set to
this value. In this case it is guaranteed that all messages of a stream are
delivered in correct order to the next processor. The lower the timeout value
is compared to the out-of-sequence time difference the higher is the
probability for out-of-sequence messages delivered by this resequencer.
Large timeout values should be supported by sufficiently high capacity
values. The capacity parameter is used to prevent the resequencer from
running out of memory.
By default, the stream resequencer expects long sequence numbers but
other sequence numbers types can be supported as well by providing a
custom expression.
public class MyFileNameExpression implements Expression {
public String getFileName(Exchange exchange) {
return exchange.getIn().getBody(String.class);
}
public Object evaluate(Exchange exchange) {
// parser the file name with YYYYMMDD-DNNN pattern
String fileName = getFileName(exchange);
String[] files = fileName.split("-D");
Long answer = Long.parseLong(files[0]) * 1000 + Long.parseLong(files[1]);
return answer;
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
404
}
public <T> T evaluate(Exchange exchange, Class<T> type) {
Object result = evaluate(exchange);
return exchange.getContext().getTypeConverter().convertTo(type, result);
}
}
from("direct:start").resequence(new
MyFileNameExpression()).stream().timeout(100).to("mock:result");
or custom comparator via the comparator() method
ExpressionResultComparator<Exchange> comparator = new MyComparator();
from("direct:start")
.resequence(header("seqnum")).stream().comparator(comparator)
.to("mock:result");
or via a StreamResequencerConfig object.
ExpressionResultComparator<Exchange> comparator = new MyComparator();
StreamResequencerConfig config = new StreamResequencerConfig(100, 1000L, comparator);
from("direct:start")
.resequence(header("seqnum")).stream(config)
.to("mock:result");
Using the Spring XML Extensions
<camelContext id="camel" xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="direct:start"/>
<resequence>
<simple>in.header.seqnum</simple>
<to uri="mock:result" />
<stream-config capacity="5000" timeout="4000"/>
</resequence>
</route>
</camelContext>
Further Examples
For further examples of this pattern in use you could look at the batchprocessing resequencer junit test case and the stream-processing
resequencer junit test case
405
CH AP T E R 10 - PAT T E R N A P P E N D I X
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
Composed Message Processor
The Composed Message Processor from the EIP patterns allows you to
process a composite message by splitting it up, routing the sub-messages to
appropriate destinations and the re-aggregating the responses back into a
single message.
Available in Camel 1.5.
Example
In this example we want to check that a multipart order can be filled. Each
part of the order requires a check at a different inventory.
// split up the order so individual OrderItems can be validated by the appropriate
bean
from("direct:start")
.split().body()
.choice()
.when().method("orderItemHelper", "isWidget")
.to("bean:widgetInventory")
.otherwise()
.to("bean:gadgetInventory")
.end()
.to("seda:aggregate");
// collect and re-assemble the validated OrderItems into an order again
from("seda:aggregate")
.aggregate(new
MyOrderAggregationStrategy()).header("orderId").completionTimeout(1000L)
.to("mock:result");
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
406
Using the Spring XML Extensions
<route>
<from uri="direct:start"/>
<split>
<simple>body</simple>
<choice>
<when>
<method bean="orderItemHelper" method="isWidget"/>
<to uri="bean:widgetInventory"/>
</when>
<otherwise>
<to uri="bean:gadgetInventory"/>
</otherwise>
</choice>
<to uri="seda:aggregate"/>
</split>
</route>
<route>
<from uri="seda:aggregate"/>
<aggregate strategyRef="myOrderAggregatorStrategy" completionTimeout="1000">
<correlationExpression>
<simple>header.orderId</simple>
</correlationExpression>
<to uri="mock:result"/>
</aggregate>
</route>
To do this we split up the order using a Splitter. The Splitter then sends
individual OrderItems to a Content Based Router which checks the item
type. Widget items get sent for checking in the widgetInventory bean and
gadgets get sent to the gadgetInventory bean. Once these OrderItems
have been validated by the appropriate bean, they are sent on to the
Aggregator which collects and re-assembles the validated OrderItems into
an order again.
When an order is sent it contains a header with the order id. We use this
fact when we aggregate, as we configure this .header("orderId") on the
aggregate DSL to instruct Camel to use the header with the key orderId as
correlation expression.
For full details, check the example source here:
camel-core/src/test/java/org/apache/camel/processor/
ComposedMessageProcessorTest.java
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
407
CH AP T E R 10 - PAT T E R N A P P E N D I X
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
Scatter-Gather
The Scatter-Gather from the EIP patterns allows you to route messages to a
number of dynamically specified recipients and re-aggregate the responses
back into a single message.
Available in Camel 1.5.
Dynamic Scatter-Gather Example
In this example we want to get the best quote for beer from several different
vendors. We use a dynamic Recipient List to get the request for a quote to all
vendors and an Aggregator to pick the best quote out of all the responses.
The routes for this are defined as:
<camelContext xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="direct:start"/>
<recipientList>
<header>listOfVendors</header>
</recipientList>
</route>
<route>
<from uri="seda:quoteAggregator"/>
<aggregate strategyRef="aggregatorStrategy" completionTimeout="1000">
<correlationExpression>
<header>quoteRequestId</header>
</correlationExpression>
<to uri="mock:result"/>
</aggregate>
</route>
</camelContext>
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
408
So in the first route you see that the Recipient List is looking at the
listOfVendors header for the list of recipients. So, we need to send a
message like
Map<String, Object> headers = new HashMap<String, Object>();
headers.put("listOfVendors", "bean:vendor1, bean:vendor2, bean:vendor3");
headers.put("quoteRequestId", "quoteRequest-1");
template.sendBodyAndHeaders("direct:start", "<quote_request item=\"beer\"/>",
headers);
This message will be distributed to the following Endpoints: bean:vendor1,
bean:vendor2, and bean:vendor3. These are all beans which look like
public class MyVendor {
private int beerPrice;
@Produce(uri = "seda:quoteAggregator")
private ProducerTemplate quoteAggregator;
public MyVendor(int beerPrice) {
this.beerPrice = beerPrice;
}
public void getQuote(@XPath("/quote_request/@item") String item, Exchange
exchange) throws Exception {
if ("beer".equals(item)) {
exchange.getIn().setBody(beerPrice);
quoteAggregator.send(exchange);
} else {
throw new Exception("No quote available for " + item);
}
}
}
and are loaded up in Spring like
<bean id="aggregatorStrategy"
class="org.apache.camel.spring.processor.scattergather.LowestQuoteAggregationStrategy"/>
<bean id="vendor1" class="org.apache.camel.spring.processor.scattergather.MyVendor">
<constructor-arg>
<value>1</value>
</constructor-arg>
</bean>
<bean id="vendor2" class="org.apache.camel.spring.processor.scattergather.MyVendor">
<constructor-arg>
<value>2</value>
</constructor-arg>
</bean>
409
CH AP T E R 10 - PAT T E R N A P P E N D I X
<bean id="vendor3" class="org.apache.camel.spring.processor.scattergather.MyVendor">
<constructor-arg>
<value>3</value>
</constructor-arg>
</bean>
Each bean is loaded with a different price for beer. When the message is sent
to each bean endpoint, it will arrive at the MyVendor.getQuote method. This
method does a simple check whether this quote request is for beer and then
sets the price of beer on the exchange for retrieval at a later step. The
message is forwarded on to the next step using POJO Producing (see the
@Produce annotation).
At the next step we want to take the beer quotes from all vendors and find
out which one was the best (i.e. the lowest!). To do this we use an Aggregator
with a custom aggregation strategy. The Aggregator needs to be able to
compare only the messages from this particular quote; this is easily done by
specifying a correlationExpression equal to the value of the quoteRequestId
header. As shown above in the message sending snippet, we set this header
to quoteRequest-1. This correlation value should be unique or you may
include responses that are not part of this quote. To pick the lowest quote out
of the set, we use a custom aggregation strategy like
public class LowestQuoteAggregationStrategy implements AggregationStrategy {
public Exchange aggregate(Exchange oldExchange, Exchange newExchange) {
// the first time we only have the new exchange
if (oldExchange == null) {
return newExchange;
}
if (oldExchange.getIn().getBody(int.class) <
newExchange.getIn().getBody(int.class)) {
return oldExchange;
} else {
return newExchange;
}
}
}
Finally, we expect to get the lowest quote of $1 out of $1, $2, and $3.
result.expectedBodiesReceived(1); // expect the lowest quote
You can find the full example source here:
camel-spring/src/test/java/org/apache/camel/spring/processor/
scattergather/
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
410
camel-spring/src/test/resources/org/apache/camel/spring/processor/
scattergather/scatter-gather.xml
Static Scatter-Gather Example
You can lock down which recipients are used in the Scatter-Gather by using a
static Recipient List. It looks something like this
from("direct:start").multicast().to("seda:vendor1", "seda:vendor2", "seda:vendor3");
from("seda:vendor1").to("bean:vendor1").to("seda:quoteAggregator");
from("seda:vendor2").to("bean:vendor2").to("seda:quoteAggregator");
from("seda:vendor3").to("bean:vendor3").to("seda:quoteAggregator");
from("seda:quoteAggregator")
.aggregate(header("quoteRequestId"), new
LowestQuoteAggregationStrategy()).to("mock:result")
A full example of the static Scatter-Gather configuration can be found in the
Loan Broker Example.
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
Routing Slip
The Routing Slip from the EIP patterns allows you to route a message
consecutively through a series of processing steps where the sequence of
steps is not known at design time and can vary for each message.
411
CH AP T E R 10 - PAT T E R N A P P E N D I X
Options
Name
Default
Value
Description
uriDelimiter
,
Delimiter used if the Expression returned multiple endpoints.
ignoreInvalidEndpoints
false
If an endpoint uri could not be resolved, should it be ignored. Otherwise Camel will thrown an
exception stating the endpoint uri is not valid.
Example
The following route will take any messages sent to the Apache ActiveMQ
queue SomeQueue and pass them into the Routing Slip pattern.
from("activemq:SomeQueue").routingSlip("headerName");
Messages will be checked for the existance of the "headerName" header. The
value of this header should be a comma-delimited list of endpoint URIs you
wish the message to be routed to. The Message will be routed in a pipeline
fashion (i.e. one after the other).
Note: In Camel 1.x the default header name routingSlipHeader has
been @deprecated and is removed in Camel 2.0. We feel that the DSL
needed to express, the header it uses to locate the destinations, directly in
the DSL to not confuse readers. So the header name must be provided.
From Camel 2.5 the Routing Slip will set a property
(Exchange.SLIP_ENDPOINT) on the Exchange which contains the current
endpoint as it advanced though the slip. This allows you to know how far we
have processed in the slip.
The Routing Slip will compute the slip beforehand which means, the slip
is only computed once. If you need to compute the slip on-the-fly then use
the Dynamic Router pattern instead.
Configuration options
Here we set the header name and the URI delimiter to something different.
Using the Fluent Builders
from("direct:c").routingSlip("aRoutingSlipHeader", "#");
Using the Spring XML Extensions
<camelContext id="buildRoutingSlip" xmlns="http://activemq.apache.org/camel/schema/
spring">
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
412
<route>
<from uri="direct:c"/>
<routingSlip headerName="aRoutingSlipHeader" uriDelimiter="#"/>
</route>
</camelContext>
Ignore invalid endpoints
Available as of Camel 2.3
The Routing Slip now supports ignoreInvalidEndpoints which the
Recipient List also supports. You can use it to skip endpoints which is invalid.
from("direct:a").routingSlip("myHeader").ignoreInvalidEndpoints();
And in Spring XML its an attribute on the recipient list tag.
<route>
<from uri="direct:a"/>
<routingSlip headerName="myHeader" ignoreInvalidEndpoints="true"/>
</route>
Then lets say the myHeader contains the following two endpoints
direct:foo,xxx:bar. The first endpoint is valid and works. However the 2nd
is invalid and will just be ignored. Camel logs at INFO level about, so you can
see why the endpoint was invalid.
Expression supporting
Available as of Camel 2.4
The Routing Slip now supports to take the expression parameter as the
Recipient List does. You can tell the camel the expression that you want to
use to get the routing slip.
from("direct:a").routingSlip(header("myHeader")).ignoreInvalidEndpoints();
And in Spring XML its an attribute on the recipient list tag.
<route>
<from uri="direct:a"/>
<!--NOTE from Camel 2.4.0, you need to specify the expression element inside
of the routingSlip element -->
<routingSlip ignoreInvalidEndpoints="true">
<header>myHeader</header>
413
CH AP T E R 10 - PAT T E R N A P P E N D I X
</routingSlip>
</route>
Further Examples
For further examples of this pattern in use you could look at the routing slip
test cases.
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
Throttler
The Throttler Pattern allows you to ensure that a specific endpoint does not
get overloaded, or that we don't exceed an agreed SLA with some external
service.
Options
Name
Default
Value
Description
maximumRequestsPerPeriod
Â
Maximum number of requests per period to throttle. This option must be provided and a positive
number. Notice, in the XML DSL, from Camel 2.8 onwards this option is configured using an
Expression instead of an attribute.
timePeriodMillis
1000
The time period in millis, in which the throttler will allow at most maximumRequestsPerPeriod
number of messages.
asyncDelayed
false
Camel 2.4: If enabled then any messages which is delayed happens asynchronously using a
scheduled thread pool.
executorServiceRef
Â
Camel 2.4: Refers to a custom Thread Pool to be used if asyncDelay has been enabled.
callerRunsWhenRejected
true
Camel 2.4: Is used if asyncDelayed was enabled. This controls if the caller thread should
execute the task if the thread pool rejected the task.
Examples
Using the Fluent Builders
from("seda:a").throttle(3).timePeriodMillis(10000).to("log:result", "mock:result");
So the above example will throttle messages all messages received on
seda:a before being sent to mock:result ensuring that a maximum of 3
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
414
messages are sent in any 10 second window. Note that typically you would
often use the default time period of a second. So to throttle requests at 100
requests per second between two endpoints it would look more like this...
from("seda:a").throttle(100).to("seda:b");
For further examples of this pattern in use you could look at the junit test
case
Using the Spring XML Extensions
Camel 2.7.x or older
<route>
<from uri="seda:a" />
<throttle maximumRequestsPerPeriod="3" timePeriodMillis="10000">
<to uri="mock:result" />
</throttle>
</route>
Camel 2.8 onwards
In Camel 2.8 onwards you must set the maximum period as an Expression as
shown below where we use a Constant expression:
<route>
<from uri="seda:a"/>
<!-- throttle 3 messages per 10 sec -->
<throttle timePeriodMillis="10000">
<constant>3</constant>
<to uri="mock:result"/>
</throttle>
</route>
Dynamically changing maximum requests per period
Available os of Camel 2.8
Since we use an Expression you can adjust this value at runtime, for example
you can provide a header with the value. At runtime Camel evaluates the
expression and converts the result to a java.lang.Long type. In the example
below we use a header from the message to determine the maximum
requests per period. If the header is absent, then the Throttler uses the old
415
CH AP T E R 10 - PAT T E R N A P P E N D I X
value. So that allows you to only provide a header if the value is to be
changed:
<route>
<from uri="direct:expressionHeader"/>
<throttle timePeriodMillis="500">
<!-- use a header to determine how many messages to throttle per 0.5 sec -->
<header>throttleValue</header>
<to uri="mock:result"/>
</throttle>
</route>
Asynchronous delaying
Available as of Camel 2.4
You can let the Throttler use non blocking asynchronous delaying, which
means Camel will use a scheduler to schedule a task to be executed in the
future. The task will then continue routing. This allows the caller thread to
not block and be able to service other messages etc.
from("seda:a").throttle(100).asyncDelayed().to("seda:b");
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
SAMPLING THROTTLER
Available as of Camel 2.1
A sampling throttler allows you to extract a sample of the exchanges from
the traffic through a route.
It is configured with a sampling period during which only a single exchange is
allowed to pass through. All other exchanges will be stopped.
Will by default use a sample period of 1 seconds.
Options
Name
Default Value
Description
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
416
messageFrequency
Â
Samples the message every N'th message. You can only use either frequency or period.
samplePeriod
1
Samples the message every N'th period. You can only use either frequency or period.
units
SECOND
Time unit as an enum of java.util.concurrent.TimeUnit from the JDK.
Samples
You use this EIP with the sample DSL as show in these samples.
Using the Fluent Builders
These samples also show how you can use the different syntax to configure
the sampling period:
from("direct:sample")
.sample()
.to("mock:result");
from("direct:sample-configured")
.sample(1, TimeUnit.SECONDS)
.to("mock:result");
from("direct:sample-configured-via-dsl")
.sample().samplePeriod(1).timeUnits(TimeUnit.SECONDS)
.to("mock:result");
from("direct:sample-messageFrequency")
.sample(10)
.to("mock:result");
from("direct:sample-messageFrequency-via-dsl")
.sample().sampleMessageFrequency(5)
.to("mock:result");
Using the Spring XML Extensions
And the same example in Spring XML is:
<route>
<from uri="direct:sample"/>
<sample samplePeriod="1" units="seconds">
<to uri="mock:result"/>
</sample>
</route>
<route>
<from uri="direct:sample-messageFrequency"/>
<sample messageFrequency="10">
<to uri="mock:result"/>
</sample>
</route>
<route>
<from uri="direct:sample-messageFrequency-via-dsl"/>
<sample messageFrequency="5">
417
CH AP T E R 10 - PAT T E R N A P P E N D I X
<to uri="mock:result"/>
</sample>
</route>
And since it uses a default of 1 second you can omit this configuration in
case you also want to use 1 second
<route>
<from uri="direct:sample"/>
<!-- will by default use 1 second period -->
<sample>
<to uri="mock:result"/>
</sample>
</route>
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
See Also
▪ Throttler
▪ Aggregator
Delayer
The Delayer Pattern allows you to delay the delivery of messages to some
destination.
Options
Name
Default
Value
Description
asyncDelayed
false
Camel 2.4: If enabled then delayed messages happens asynchronously using a scheduled
thread pool.
executorServiceRef
Â
Camel 2.4: Refers to a custom Thread Pool to be used if asyncDelay has been enabled.
callerRunsWhenRejected
true
Camel 2.4: Is used if asyncDelayed was enabled. This controls if the caller thread should
execute the task if the thread pool rejected the task.
Using the Fluent Builders
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
418
The Delayer in Camel 1.x works a bit differently than Camel 2.0
onwards.
In Camel 1.x the expression is used to calculate an absolute time in millis.
So if you want to wait 3 sec from now and want to use the expression for
that you have to set the absolute time as currentTimeInMillis() +
3000.
In Camel 2.0 the expression is a value in millis to wait from the current
time, so the expression should just be 3000.
However in both Camel 1.x and 2.0 you can use a long value for a fixed
value to indicate the delay in millis.
See the Spring DSL samples for Delayer in Camel 1.x vs. Camel 2.0.
Using Delayer in Java DSL
See this ticket: https://issues.apache.org/jira/browse/CAMEL-2654
from("seda:b").delay(1000).to("mock:result");
So the above example will delay all messages received on seda:b 1 second
before sending them to mock:result.
You can of course use many different Expression languages such as XPath,
XQuery, SQL or various Scripting Languages. You can just delay things a fixed
amount of time from the point at which the delayer receives the message.
For example to delay things 2 seconds
delayer(2000)
The above assume that the delivery order is maintained and that the
messages are delivered in delay order. If you want to reorder the messages
based on delivery time, you can use the Resequencer with this pattern. For
example
from("activemq:someQueue").resequencer(header("MyDeliveryTime")).delay("MyRedeliveryTime").to("activem
Camel 2.0 - Spring DSL
The sample below demonstrates the delay in Spring DSL:
419
CH AP T E R 10 - PAT T E R N A P P E N D I X
<camelContext xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="seda:a"/>
<delay>
<header>MyDelay</header>
</delay>
<to uri="mock:result"/>
</route>
<route>
<from uri="seda:b"/>
<delay>
<constant>1000</constant>
</delay>
<to uri="mock:result"/>
</route>
</camelContext>
Camel 1.x - Spring DSL
The delayer is using slightly different names in Camel 1.x:
<delayer>
<delayTime>3000</delayTime>
</expression>
</delayer>
The empty tag </expression> is needed to fulfill the XSD validation as its an
optional element and we use JAXB annotations to generated the XSD in
Camel and some combinations is hard to auto generate with optional
elements.
For further examples of this pattern in use you could look at the junit test
case
Asynchronous delaying
Available as of Camel 2.4
You can let the Delayer use non blocking asynchronous delaying, which
means Camel will use a scheduler to schedule a task to be executed in the
future. The task will then continue routing. This allows the caller thread to
not block and be able to service other messages etc.
From Java DSL
You use the asyncDelayed() to enable the async behavior.
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
420
from("activemq:queue:foo").delay(1000).asyncDelayed().to("activemq:aDelayedQueue");
From Spring XML
You use the asyncDelayed="true" attribute to enable the async behavior.
<route>
<from uri="activemq:queue:foo"/>
<delay asyncDelayed="true">
<constant>1000</constant>
</delay>
<to uri="activemq:aDealyedQueue"/>
</route>
Creating a custom delay
You can use an expression to determine when to send a message using
something like this
from("activemq:foo").
delay().method("someBean", "computeDelay").
to("activemq:bar");
then the bean would look like this...
public class SomeBean {
public long computeDelay() {
long delay = 0;
// use java code to compute a delay value in millis
return delay;
}
}
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
421
CH AP T E R 10 - PAT T E R N A P P E N D I X
Load Balancer
The Load Balancer Pattern allows you to delegate to one of a number of
endpoints using a variety of different load balancing policies.
Build in load balancing policies
Camel has out of the box the following policies:
Policy
Description
Round
Robin
The exchanges is selected in a round robin fashion. This is a
well known and classic policy. This spreads the load even.
Random
A random endpoint is selected for each exchange
Sticky
Sticky load balancing using an Expression to calculate a
correlation key to perform the sticky load balancing; rather like
jsessionid in the web or JMSXGroupID in JMS.
Topic
Topic which sends to all destinations (rather like JMS Topics)
Failover
Camel 2.0: In case of failures the exchange is tried on the
next endpoint.
Weighted
RoundRobin
Camel 2.5: The weighted load balancing policy allows you to
specify a processing load distribution ratio for each server with
respect to others.In addition to the weight, endpoint selection
is then further refined using round-robin distribution based
on weight.
Weighted
Random
Camel 2.5: The weighted load balancing policy allows you to
specify a processing load distribution ratio for each server with
respect to others.In addition to the weight, endpoint selection
is then further refined using random distribution based on
weight.
Round Robin
Camel 1.x behavior
The round robin load balancer can actually be used to failover with Camel
1.x. This is no longer possible in Camel 2.x as the underlying Error Handler
foundation has been significantly overhauled in Camel 2.x. Frankly the round
robin load balancer in Camel 1.x was not thought to be used in a failover
scenario.
Camel 2.x behavior
The round robin load balancer is not meant to work with failover, for that you
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
422
should use the dedicated failover load balancer. The round robin load
balancer will only change to next endpoint per message.
The round robin load balancer is statefull as it keeps state which endpoint
to use next time.
Using the Fluent Builders
from("direct:start").loadBalance().
roundRobin().to("mock:x", "mock:y", "mock:z");
Using the Spring configuration
<camelContext id="camel" xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="direct:start"/>
<loadBalance>
<roundRobin/>
<to uri="mock:x"/>
<to uri="mock:y"/>
<to uri="mock:z"/>
</loadBalance>
</route>
</camelContext>
So the above example will load balance requests from direct:start to one of
the available mock endpoint instances, in this case using a round robbin
policy.
For further examples of this pattern in use you could look at the junit test
case
Failover
Available as of Camel 2.0
The failover load balancer is capable of trying the next processor in case
an Exchange failed with an exception during processing.
You can configure the failover with a list of specific exception to only
failover. If you do not specify any exceptions it will failover over any
exceptions. It uses the same strategy for matching exceptions as the
Exception Clause does for the onException.
It has the following options:
Option
423
Type
CH AP T E R 10 - PAT T E R N A P P E N D I X
Default
Description
Enable stream caching if using streams
If you use streaming then you should enable Stream caching when
using the failover load balancer. This is needed so the stream can
be re-read when failing over.
inheritErrorHandler
boolean
true
Camel 2.3: Whether or
not the Error Handler
configured on the route
should be used or not.
You can disable it if you
want the failover to
trigger immediately and
failover to the next
endpoint. On the other
hand if you have this
option enabled, then
Camel will first let the
Error Handler try to
process the message.
The Error Handler may
have been configured to
redelivery and use
delays between
attempts. If you have
enabled a number of
redeliveries then Camel
will try to redeliver to
the same endpoint, and
only failover to the next
endpoint, when the Error
Handler is exhausted.
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
424
maximumFailoverAttempts
roundRobin
int
boolean
-1
Camel 2.3: A value to
indicate after X failver
attempts we should
exhaust (give up). Use -1
to indicate newer give
up and always try to
failover. Use 0 to newer
failover. And use e.g. 3
to failover at most 3
times before giving up.
This option can be used
whether or not round
robin is enabled or not.
false
Camel 2.3: Whether or
not the failover load
balancer should operate
in round robin mode or
not. If not, then it will
always start from the
first endpoint when a
new message is to be
processed. In other
words it restart from the
top for every message. If
round robin is enabled,
then it keeps state and
will continue with the
next endpoint in a round
robin fashion. When
using round robin it will
not stick to last known
good endpoint, it will
always pick the next
endpoint to use.
Camel 2.2 or older behavior
The current implement of failover load balancer is a simple logic which
always tries the first endpoint, and in case of an exception being thrown it
tries the next in the list, and so forth. It has no state, and the next message
will thus always start with the first endpoint.
Camel 2.3 onwards behavior
The failover load balancer now supports round robin mode, which allows
you to failover in a round robin fashion. See the roundRobin option.
425
CH AP T E R 10 - PAT T E R N A P P E N D I X
Redelivery must be enabled
In Camel 2.2 or older the failover load balancer requires you have
enabled Camel Error Handler to use redelivery. In Camel 2.3
onwards this is not required as such, as you can mix and match.
See the inheritErrorHandler option.
Here is a sample to failover only if a IOException related exception was
thrown:
from("direct:start")
// here we will load balance if IOException was thrown
// any other kind of exception will result in the Exchange as failed
// to failover over any kind of exception we can just omit the exception
// in the failOver DSL
.loadBalance().failover(IOException.class)
.to("direct:x", "direct:y", "direct:z");
You can specify multiple exceptions to failover as the option is varargs, for
instance:
// enable redelivery so failover can react
errorHandler(defaultErrorHandler().maximumRedeliveries(5));
from("direct:foo").
loadBalance().failover(IOException.class, MyOtherException.class)
.to("direct:a", "direct:b");
Using failover in Spring DSL
Failover can also be used from Spring DSL and you configure it as:
<route errorHandlerRef="myErrorHandler">
<from uri="direct:foo"/>
<loadBalance>
<failover>
<exception>java.io.IOException</exception>
<exception>com.mycompany.MyOtherException</exception>
</failover>
<to uri="direct:a"/>
<to uri="direct:b"/>
</loadBalance>
</route>
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
426
Using failover in round robin mode
An example using Java DSL:
from("direct:start")
// Use failover load balancer in stateful round robin mode
// which mean it will failover immediately in case of an exception
// as it does NOT inherit error handler. It will also keep retrying as
// its configured to newer exhaust.
.loadBalance().failover(-1, false, true).
to("direct:bad", "direct:bad2", "direct:good", "direct:good2");
And the same example using Spring XML:
<route>
<from uri="direct:start"/>
<loadBalance>
<!-- failover using stateful round robin,
which will keep retrying forever those 4 endpoints until success.
You can set the maximumFailoverAttempt to break out after X attempts -->
<failover roundRobin="true"/>
<to uri="direct:bad"/>
<to uri="direct:bad2"/>
<to uri="direct:good"/>
<to uri="direct:good2"/>
</loadBalance>
</route>
Weighted Round-Robin and Random Load Balancing
Available as of Camel 2.5
In many enterprise environments where server nodes of unequal
processing power & performance characteristics are utilized to host services
and processing endpoints, it is frequently necessary to distribute processing
load based on their individual server capabilities so that some endpoints are
not unfairly burdened with requests. Obviously simple round-robin or random
load balancing do not alleviate problems of this nature. A Weighted RoundRobin and/or Weighted Random load balancer can be used to address this
problem.
The weighted load balancing policy allows you to specify a processing load
distribution ratio for each server with respect to others. You can specify this
as a positive processing weight for each server. A larger number indicates
that the server can handle a larger load. The weight is utilized to determine
the payload distribution ratio to different processing endpoints with respect
to others.
The parameters that can be used are
427
CH AP T E R 10 - PAT T E R N A P P E N D I X
Disabled inheritErrorHandler
You can configure inheritErrorHandler=false if you want to
failover to the next endpoint as fast as possible. By disabling the
Error Handler you ensure it does not intervene which allows the
failover load balancer to handle failover asap. By also enabling
roundRobin mode, then it will keep retrying until it success. You can
then configure the maximumFailoverAttempts option to a high
value to let it eventually exhaust (give up) and fail.
Disabled inheritErrorHandler
As of Camel 2.6, the Weighted Load balancer usage has been
further simplified, there is no need to send in distributionRatio as a
List<Integer>. It can be simply sent as a delimited String of integer
weights separated by a delimiter of choice.
In Camel 2.5
Option
roundRobin
distributionRatio
Type
boolean
List<Integer>
Default
Description
false
The default value for roundrobin is false. In the absence
of this setting or parameter
the load balancing algorithm
used is random.
none
The distributionRatio is a list
consisting on integer weights
passed in as a parameter.
The distributionRatio must
match the number of
endpoints and/or processors
specified in the load balancer
list. In Camel 2.5 if endpoints
do not match ratios, then a
best effort distribution is
attempted.
Available In Camel 2.6
Option
Type
Default
Description
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
428
roundRobin
distributionRatio
distributionRatioDelimiter
boolean
String
String
false
The default value for
round-robin is false. In the
absence of this setting or
parameter the load
balancing algorithm used
is random.
none
The distributionRatio is a
delimited String
consisting on integer
weights separated by
delimiters for example
"2,3,5". The
distributionRatio must
match the number of
endpoints and/or
processors specified in
the load balancer list.
,
The
distributionRatioDelimiter
is the delimiter used to
specify the
distributionRatio. If this
attribute is not specified a
default delimiter "," is
expected as the delimiter
used for specifying the
distributionRatio.
Using Weighted round-robin & random load balancing
In Camel 2.5
An example using Java DSL:
ArrayList<integer> distributionRatio = new ArrayList<integer>();
distributionRatio.add(4);
distributionRatio.add(2);
distributionRatio.add(1);
// round-robin
from("direct:start")
.loadBalance().weighted(true, distributionRatio)
.to("mock:x", "mock:y", "mock:z");
429
CH AP T E R 10 - PAT T E R N A P P E N D I X
//random
from("direct:start")
.loadBalance().weighted(false, distributionRatio)
.to("mock:x", "mock:y", "mock:z");
And the same example using Spring XML:
<route>
<from uri="direct:start"/>
<loadBalance>
<weighted roundRobin="false" distributionRatio="4 2 1"/>
<to uri="mock:x"/>
<to uri="mock:y"/>
<to uri="mock:z"/>
</loadBalance>
</route>
Available In Camel 2.6
An example using Java DSL:
// round-robin
from("direct:start")
.loadBalance().weighted(true, "4:2:1" distributionRatioDelimiter=":")
.to("mock:x", "mock:y", "mock:z");
//random
from("direct:start")
.loadBalance().weighted(false, "4,2,1")
.to("mock:x", "mock:y", "mock:z");
And the same example using Spring XML:
<route>
<from uri="direct:start"/>
<loadBalance>
<weighted roundRobin="false" distributionRatio="4-2-1"
distributionRatioDelimiter="-" />
<to uri="mock:x"/>
<to uri="mock:y"/>
<to uri="mock:z"/>
</loadBalance>
</route>
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
430
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
Multicast
The Multicast allows to route the same message to a number of endpoints
and process them in a different way. The main difference between the
Multicast and Splitter is that Splitter will split the message into several pieces
but the Multicast will not modify the request message.
Options
Name
Default
Value
Description
strategyRef
Â
Refers to an AggregationStrategy to be used to assemble the replies from the multicasts, into a single
outgoing message from the Multicast. By default Camel will use the last reply as the outgoing message.
parallelProcessing
false
If enables then sending messages to the multicasts occurs concurrently. Note the caller thread will still
wait until all messages has been fully processed, before it continues. Its only the sending and
processing the replies from the multicasts which happens concurrently.
executorServiceRef
Â
Refers to a custom Thread Pool to be used for parallel processing. Notice if you set this option, then
parallel processing is automatic implied, and you do not have to enable that option as well.
stopOnException
false
Camel 2.2: Whether or not to stop continue processing immediately when an exception occurred. If
disable, then Camel will send the message to all multicasts regardless if one of them failed. You can
deal with exceptions in the AggregationStrategy class where you have full control how to handle that.
streaming
false
If enabled then Camel will process replies out-of-order, eg in the order they come back. If disabled,
Camel will process replies in the same order as multicasted.
timeout
Â
Camel 2.5: Sets a total timeout specified in millis. If the Multicast hasn't been able to send and process
all replies within the given timeframe, then the timeout triggers and the Multicast breaks out and
continues. Notice if you provide a TimeoutAwareAggregationStrategy then the timeout method is
invoked before breaking out.
onPrepareRef
Â
Camel 2.8: Refers to a custom Processor to prepare the copy of the Exchange each multicast will
receive. This allows you to do any custom logic, such as deep-cloning the message payload if that's
needed etc.
Example
The following example shows how to take a request from the direct:a
endpoint , then multicast these request to direct:x, direct:y, direct:z.
Using the Fluent Builders
from("direct:a").multicast().to("direct:x", "direct:y", "direct:z");
By default Multicast invokes each endpoint sequentially. If parallel processing
is desired, simply use
431
CH AP T E R 10 - PAT T E R N A P P E N D I X
from("direct:a").multicast().parallelProcessing().to("direct:x", "direct:y",
"direct:z");
In case of using InOut MEP, an AggregationStrategy is used for aggregating
all reply messages. The default is to only use the latest reply message and
discard any earlier replies. The aggregation strategy is configurable:
from("direct:start")
.multicast(new MyAggregationStrategy())
.parallelProcessing().timeout(500).to("direct:a", "direct:b", "direct:c")
.end()
.to("mock:result");
Stop processing in case of exception
Available as of Camel 2.1
The Multicast will by default continue to process the entire Exchange even
in case one of the multicasted messages will thrown an exception during
routing.
For example if you want to multicast to 3 destinations and the 2nd
destination fails by an exception. What Camel does by default is to process
the remainder destinations. You have the chance to remedy or handle this in
the AggregationStrategy.
But sometimes you just want Camel to stop and let the exception be
propagated back, and let the Camel error handler handle it. You can do this in
Camel 2.1 by specifying that it should stop in case of an exception occurred.
This is done by the stopOnException option as shown below:
from("direct:start")
.multicast()
.stopOnException().to("direct:foo", "direct:bar", "direct:baz")
.end()
.to("mock:result");
from("direct:foo").to("mock:foo");
from("direct:bar").process(new MyProcessor()).to("mock:bar");
from("direct:baz").to("mock:baz");
And using XML DSL you specify it as follows:
<route>
<from uri="direct:start"/>
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
432
<multicast stopOnException="true">
<to uri="direct:foo"/>
<to uri="direct:bar"/>
<to uri="direct:baz"/>
</multicast>
<to uri="mock:result"/>
</route>
<route>
<from uri="direct:foo"/>
<to uri="mock:foo"/>
</route>
<route>
<from uri="direct:bar"/>
<process ref="myProcessor"/>
<to uri="mock:bar"/>
</route>
<route>
<from uri="direct:baz"/>
<to uri="mock:baz"/>
</route>
Using onPrepare to execute custom logic when preparing messages
Available as of Camel 2.8
The Multicast will copy the source Exchange and multicast each copy.
However the copy is a shallow copy, so in case you have mutateable
message bodies, then any changes will be visible by the other copied
messages. If you want to use a deep clone copy then you need to use a
custom onPrepare which allows you to do this using the Processor interface.
Notice the onPrepare can be used for any kind of custom logic which you
would like to execute before the Exchange is being multicasted.
For example if you have a mutable message body as this Animal class:
Listing 55. Animal
public class Animal implements Serializable {
private int id;
private String name;
public Animal() {
}
public Animal(int id, String name) {
this.id = id;
this.name = name;
433
CH AP T E R 10 - PAT T E R N A P P E N D I X
Design for immutable
Its best practice to design for immutable objects.
}
public Animal deepClone() {
Animal clone = new Animal();
clone.setId(getId());
clone.setName(getName());
return clone;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Override
public String toString() {
return id + " " + name;
}
}
Then we can create a deep clone processor which clones the message body:
Listing 56. AnimalDeepClonePrepare
public class AnimalDeepClonePrepare implements Processor {
public void process(Exchange exchange) throws Exception {
Animal body = exchange.getIn().getBody(Animal.class);
// do a deep clone of the body which wont affect when doing multicasting
Animal clone = body.deepClone();
exchange.getIn().setBody(clone);
}
}
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
434
Then we can use the AnimalDeepClonePrepare class in the Multicast route
using the onPrepare option as shown:
Listing 57. Multicast using onPrepare
from("direct:start")
.multicast().onPrepare(new
AnimalDeepClonePrepare()).to("direct:a").to("direct:b");
And the same example in XML DSL
Listing 58. Multicast using onPrepare
<camelContext xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="direct:start"/>
<!-- use on prepare with multicast -->
<multicast onPrepareRef="animalDeepClonePrepare">
<to uri="direct:a"/>
<to uri="direct:b"/>
</multicast>
</route>
<route>
<from uri="direct:a"/>
<process ref="processorA"/>
<to uri="mock:a"/>
</route>
<route>
<from uri="direct:b"/>
<process ref="processorB"/>
<to uri="mock:b"/>
</route>
</camelContext>
<!-- the on prepare Processor which performs the deep cloning -->
<bean id="animalDeepClonePrepare"
class="org.apache.camel.processor.AnimalDeepClonePrepare"/>
<!-- processors used for the last two routes, as part of unit test -->
<bean id="processorA"
class="org.apache.camel.processor.MulticastOnPrepareTest$ProcessorA"/>
<bean id="processorB"
class="org.apache.camel.processor.MulticastOnPrepareTest$ProcessorB"/>
Notice the onPrepare option is also available on other EIPs such as Splitter,
Recipient List, and Wire Tap.
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
435
CH AP T E R 10 - PAT T E R N A P P E N D I X
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
LOOP
The Loop allows to process the a message a number of times and possibly
process them in a different way. Useful mostly for testing.
For each iteration two properties are set on the Exchange that could be
used by processors down the pipeline to process the Message in different
ways.
Property
Description
CamelIterationCount
Camel 1.x: Total number of iterations to be run
CamelIterationIndex
Camel 1.x: Index of the current iteration (0
based)
CamelLoopSize
Camel 2.0: Total number of loops
CamelLoopIndex
Camel 2.0: Index of the current iteration (0
based)
that could be used by processors down the pipeline to process the Message
in different ways.
Examples
The following example shows how to take a request from the direct:x
endpoint , then send the message repetitively to mock:result. The number
of times the message is sent is either passed as an argument to loop(), or
determined at runtime by evaluating an expression. The expression must
evaluate to an int, otherwise a RuntimeCamelException is thrown.
Using the Fluent Builders
Pass loop count as an argument
from("direct:a").loop(8).to("mock:result");
Use expression to determine loop count
from("direct:b").loop(header("loop")).to("mock:result");
Use expression to determine loop count
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
436
from("direct:c").loop().xpath("/hello/@times").to("mock:result");
Using the Spring XML Extensions
Pass loop count as an argument
<route>
<from uri="direct:a"/>
<loop>
<constant>8</constant>
<to uri="mock:result"/>
</loop>
</route>
Use expression to determine loop count
<route>
<from uri="direct:b"/>
<loop>
<header>loop</header>
<to uri="mock:result"/>
</loop>
</route>
For further examples of this pattern in use you could look at one of the junit
test case
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
MESSAGE TRANSFORMATION
Content Enricher
Camel supports the Content Enricher from the EIP patterns using a Message
Translator, an artibrary Processor in the routing logic or using the enrich DSL
element to enrich the message.
437
CH AP T E R 10 - PAT T E R N A P P E N D I X
Content enrichment using a Message Translator or a
Processor
Using the Fluent Builders
You can use Templating to consume a message from one destination,
transform it with something like Velocity or XQuery and then send it on to
another destination. For example using InOnly (one way messaging)
from("activemq:My.Queue").
to("velocity:com/acme/MyResponse.vm").
to("activemq:Another.Queue");
If you want to use InOut (request-reply) semantics to process requests on the
My.Queue queue on ActiveMQ with a template generated response, then
sending responses back to the JMSReplyTo Destination you could use this.
from("activemq:My.Queue").
to("velocity:com/acme/MyResponse.vm");
Here is a simple example using the DSL directly to transform the message
body
from("direct:start").setBody(body().append(" World!")).to("mock:result");
In this example we add our own Processor using explicit Java code
from("direct:start").process(new Processor() {
public void process(Exchange exchange) {
Message in = exchange.getIn();
in.setBody(in.getBody(String.class) + " World!");
}
}).to("mock:result");
Finally we can use Bean Integration to use any Java method on any bean to
act as the transformer
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
438
from("activemq:My.Queue").
beanRef("myBeanName", "myMethodName").
to("activemq:Another.Queue");
For further examples of this pattern in use you could look at one of the JUnit
tests
• TransformTest
• TransformViaDSLTest
Using Spring XML
<route>
<from uri="activemq:Input"/>
<bean ref="myBeanName" method="doTransform"/>
<to uri="activemq:Output"/>
</route>
Content enrichment using the enrich DSL element
Camel comes with two flavors of content enricher in the DSL
▪ enrich
▪ pollEnrich
enrich is using a Producer to obtain the additional data. It is usually used
for Request Reply messaging, for instance to invoke an external web service.
pollEnrich on the other hand is using a Polling Consumer to obtain the
additional data. It is usually used for Event Message messaging, for instance
to read a file or download a FTP file.
This feature is available since Camel 2.0
Enrich Options
Name
Default
Value
Description
uri
Â
The endpoint uri for the external servie to enrich from. You must use either uri or ref.
ref
Â
Refers to the endpoint for the external servie to enrich from. You must use either uri or ref.
strategyRef
Â
Refers to an AggregationStrategy to be used to merge the reply from the external service, into a single outgoing
message. By default Camel will use the reply from the external service as outgoing message.
Using the Fluent Builders
AggregationStrategy aggregationStrategy = ...
from("direct:start")
.enrich("direct:resource", aggregationStrategy)
.to("direct:result");
439
CH AP T E R 10 - PAT T E R N A P P E N D I X
from("direct:resource")
...
The content enricher (enrich) retrieves additional data from a resource
endpoint in order to enrich an incoming message (contained in the orginal
exchange). An aggregation strategy is used to combine the original exchange
and the resource exchange. The first parameter of the
AggregationStrategy.aggregate(Exchange, Exchange) method
corresponds to the the original exchange, the second parameter the resource
exchange. The results from the resource endpoint are stored in the resource
exchange's out-message. Here's an example template for implementing an
aggregation strategy.
public class ExampleAggregationStrategy implements AggregationStrategy {
public Exchange aggregate(Exchange original, Exchange resource) {
Object originalBody = original.getIn().getBody();
Object resourceResponse = resource.getOut().getBody();
Object mergeResult = ... // combine original body and resource response
if (original.getPattern().isOutCapable()) {
original.getOut().setBody(mergeResult);
} else {
original.getIn().setBody(mergeResult);
}
return original;
}
}
Using this template the original exchange can be of any pattern. The
resource exchange created by the enricher is always an in-out exchange.
Using Spring XML
The same example in the Spring DSL
<camelContext id="camel" xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="direct:start"/>
<enrich uri="direct:resource" strategyRef="aggregationStrategy"/>
<to uri="direct:result"/>
</route>
<route>
<from uri="direct:resource"/>
...
</route>
</camelContext>
<bean id="aggregationStrategy" class="..." />
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
440
Aggregation strategy is optional
The aggregation strategy is optional. If you do not provide it Camel will by
default just use the body obtained from the resource.
from("direct:start")
.enrich("direct:resource")
.to("direct:result");
In the route above the message send to the direct:result endpoint will
contain the output from the direct:resource as we do not use any custom
aggregation.
And in Spring DSL you just omit the strategyRef attribute:
<route>
<from uri="direct:start"/>
<enrich uri="direct:resource"/>
<to uri="direct:result"/>
</route>
Content enrich using pollEnrich
The pollEnrich works just as the enrich however as it uses a Polling
Consumer we have 3 methods when polling
▪ receive
▪ receiveNoWait
▪ receive(timeout)
PollEnrich Options
Name
Default
Value
Description
uri
Â
The endpoint uri for the external servie to enrich from. You must use either uri or ref.
ref
Â
Refers to the endpoint for the external servie to enrich from. You must use either uri or ref.
strategyRef
Â
Refers to an AggregationStrategy to be used to merge the reply from the external service, into a single outgoing
message. By default Camel will use the reply from the external service as outgoing message.
timeout
0
Timeout in millis to use when polling from the external service. See below for important details about the
timeout.
By default Camel will use the receiveNoWait.
If there is no data then the newExchange in the aggregation strategy is null.
You can pass in a timeout value that determines which method to use
▪ timeout is -1 or negative then receive is selected
▪ timeout is 0 then receiveNoWait is selected
▪ otherwise receive(timeout) is selected
The timeout values is in millis.
441
CH AP T E R 10 - PAT T E R N A P P E N D I X
Data from current Exchange not used
pollEnrich does not access any data from the current Exchange
which means when polling it cannot use any of the existing headers
you may have set on the Exchange. For example you cannot set a
filename in the Exchange.FILE_NAME header and use pollEnrich
to consume only that file. For that you must set the filename in the
endpoint URI.
Example
In this example we enrich the message by loading the content from the file
named inbox/data.txt.
from("direct:start")
.pollEnrich("file:inbox?fileName=data.txt")
.to("direct:result");
And in XML DSL you do:
<route>
<from uri="direct:start"/>
<pollEnrich uri="file:inbox?fileName=data.txt"/>
<to uri="direct:result"/>
</route>
If there is no file then the message is empty. We can use a timeout to either
wait (potential forever) until a file exists, or use a timeout to wait a period.
For example to wait up til 5 seconds you can do:
<route>
<from uri="direct:start"/>
<pollEnrich uri="file:inbox?fileName=data.txt" timeout="5000"/>
<to uri="direct:result"/>
</route>
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
442
Content Filter
Camel supports the Content Filter from the EIP patterns using one of the
following mechanisms in the routing logic to transform content from the
inbound message.
• Message Translator
• invoking a Java bean
• Processor object
A common way to filter messages is to use an Expression in the DSL like
XQuery, SQL or one of the supported Scripting Languages.
Using the Fluent Builders
Here is a simple example using the DSL directly
from("direct:start").setBody(body().append(" World!")).to("mock:result");
In this example we add our own Processor
from("direct:start").process(new Processor() {
public void process(Exchange exchange) {
Message in = exchange.getIn();
in.setBody(in.getBody(String.class) + " World!");
}
}).to("mock:result");
For further examples of this pattern in use you could look at one of the JUnit
tests
• TransformTest
• TransformViaDSLTest
Using Spring XML
<route>
<from uri="activemq:Input"/>
<bean ref="myBeanName" method="doTransform"/>
<to uri="activemq:Output"/>
</route>
You can also use XPath to filter out part of the message you are interested in:
<route>
<from uri="activemq:Input"/>
443
CH AP T E R 10 - PAT T E R N A P P E N D I X
<setBody><xpath resultType="org.w3c.dom.Document">//foo:bar</xpath></setBody>
<to uri="activemq:Output"/>
</route>
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
Claim Check
The Claim Check from the EIP patterns allows you to replace message
content with a claim check (a unique key), which can be used to retrieve the
message content at a later time. The message content is stored temporarily
in a persistent store like a database or file system. This pattern is very useful
when message content is very large (thus it would be expensive to send
around) and not all components require all information.
It can also be useful in situations where you cannot trust the information
with an outside party; in this case, you can use the Claim Check to hide the
sensitive portions of data.
Available in Camel 1.5.
Example
In this example we want to replace a message body with a claim check, and
restore the body at a later step.
from("direct:start").to("bean:checkLuggage", "mock:testCheckpoint",
"bean:dataEnricher", "mock:result");
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
444
The example route is pretty simple - its just a Pipeline. In a real application
you would have some other steps where the mock:testCheckpoint endpoint
is in the example.
The message is first sent to the checkLuggage bean which looks like
public static final class CheckLuggageBean {
public void checkLuggage(Exchange exchange, @Body String body, @XPath("/order/
@custId") String custId) {
// store the message body into the data store, using the custId as the claim
check
dataStore.put(custId, body);
// add the claim check as a header
exchange.getIn().setHeader("claimCheck", custId);
// remove the body from the message
exchange.getIn().setBody(null);
}
}
This bean stores the message body into the data store, using the custId as
the claim check. In this example, we're just using a HashMap to store the
message body; in a real application you would use a database or file system,
etc. Next the claim check is added as a message header for use later. Finally
we remove the body from the message and pass it down the pipeline.
The next step in the pipeline is the mock:testCheckpoint endpoint which
is just used to check that the message body is removed, claim check added,
etc.
To add the message body back into the message, we use the
dataEnricher bean which looks like
public static final class DataEnricherBean {
public void addDataBackIn(Exchange exchange, @Header("claimCheck") String
claimCheck) {
// query the data store using the claim check as the key and add the data
// back into the message body
exchange.getIn().setBody(dataStore.get(claimCheck));
// remove the message data from the data store
dataStore.remove(claimCheck);
// remove the claim check header
exchange.getIn().removeHeader("claimCheck");
}
}
This bean queries the data store using the claim check as the key and then
adds the data back into the message. The message body is then removed
from the data store and finally the claim check is removed. Now the message
is back to what we started with!
For full details, check the example source here:
445
CH AP T E R 10 - PAT T E R N A P P E N D I X
camel-core/src/test/java/org/apache/camel/processor/ClaimCheckTest.java
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
Normalizer
Camel supports the Normalizer from the EIP patterns by using a Message
Router in front of a number of Message Translator instances.
Example
This example shows a Message Normalizer that converts two types of XML
messages into a common format. Messages in this common format are then
filtered.
Using the Fluent Builders
// we need to normalize two types of incoming messages
from("direct:start")
.choice()
.when().xpath("/employee").to("bean:normalizer?method=employeeToPerson")
.when().xpath("/customer").to("bean:normalizer?method=customerToPerson")
.end()
.to("mock:result");
In this case we're using a Java bean as the normalizer. The class looks like
this
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
446
public class MyNormalizer {
public void employeeToPerson(Exchange exchange, @XPath("/employee/name/text()")
String name) {
exchange.getOut().setBody(createPerson(name));
}
public void customerToPerson(Exchange exchange, @XPath("/customer/@name") String
name) {
exchange.getOut().setBody(createPerson(name));
}
private String createPerson(String name) {
return "<person name=\"" + name + "\"/>";
}
}
Using the Spring XML Extensions
The same example in the Spring DSL
<camelContext xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="direct:start"/>
<choice>
<when>
<xpath>/employee</xpath>
<to uri="bean:normalizer?method=employeeToPerson"/>
</when>
<when>
<xpath>/customer</xpath>
<to uri="bean:normalizer?method=customerToPerson"/>
</when>
</choice>
<to uri="mock:result"/>
</route>
</camelContext>
<bean id="normalizer" class="org.apache.camel.processor.MyNormalizer"/>
See Also
• Message Router
• Content Based Router
• Message Translator
447
CH AP T E R 10 - PAT T E R N A P P E N D I X
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
SORT
Available as of Camel 2.0
Sort can be used to sort a message. Imagine you consume text files and
before processing each file you want to be sure the content is sorted.
Sort will by default sort the body using a default comparator that handles
numeric values or uses the string representation. You can provide your own
comparator, and even an expression to return the value to be sorted. Sort
requires the value returned from the expression evaluation is convertible to
java.util.List as this is required by the JDK sort operation.
Options
Name
Default
Value
Description
comparatorRef
Â
Refers to a custom java.util.Comparator to use for sorting the message body. Camel will by default use
a comparator which does a A..Z sorting.
Using from Java DSL
In the route below it will read the file content and tokenize by line breaks so
each line can be sorted.
from("file://inbox").sort(body().tokenize("\n")).to("bean:MyServiceBean.processLine");
You can pass in your own comparator as a 2nd argument:
from("file://inbox").sort(body().tokenize("\n"), new
MyReverseComparator()).to("bean:MyServiceBean.processLine");
Using from Spring DSL
In the route below it will read the file content and tokenize by line breaks so
each line can be sorted.
Listing 59. Camel 2.7 or better
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
448
<route>
<from uri="file://inbox"/>
<sort>
<simple>body</simple>
</sort>
<beanRef ref="myServiceBean" method="processLine"/>
</route>
Listing 60. Camel 2.6 or older
<route>
<from uri="file://inbox"/>
<sort>
<expression>
<simple>body</simple>
</expression>
</sort>
<beanRef ref="myServiceBean" method="processLine"/>
</route>
And to use our own comparator we can refer to it as a spring bean:
Listing 61. Camel 2.7 or better
<route>
<from uri="file://inbox"/>
<sort comparatorRef="myReverseComparator">
<simple>body</simple>
</sort>
<beanRef ref="MyServiceBean" method="processLine"/>
</route>
<bean id="myReverseComparator" class="com.mycompany.MyReverseComparator"/>
Listing 62. Camel 2.6 or older
<route>
<from uri="file://inbox"/>
<sort comparatorRef="myReverseComparator">
<expression>
<simple>body</simple>
</expression>
</sort>
<beanRef ref="MyServiceBean" method="processLine"/>
</route>
<bean id="myReverseComparator" class="com.mycompany.MyReverseComparator"/>
Besides <simple>, you can supply an expression using any language you
like, so long as it returns a list.
449
CH AP T E R 10 - PAT T E R N A P P E N D I X
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
MESSAGING ENDPOINTS
Messaging Mapper
Camel supports the Messaging Mapper from the EIP patterns by using either
Message Translator pattern or the Type Converter module.
See also
• Message Translator
• Type Converter
• CXF for JAX-WS support for binding business logic to messaging &
web services
• Pojo
• Bean
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
Event Driven Consumer
Camel supports the Event Driven Consumer from the EIP patterns. The
default consumer model is event based (i.e. asynchronous) as this means
that the Camel container can then manage pooling, threading and
concurrency for you in a declarative manner.
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
450
The Event Driven Consumer is implemented by consumers implementing
the Processor interface which is invoked by the Message Endpoint when a
Message is available for processing.
For more details see
• Message
• Message Endpoint
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
Polling Consumer
Camel supports implementing the Polling Consumer from the EIP patterns
using the PollingConsumer interface which can be created via the
Endpoint.createPollingConsumer() method.
So in your Java code you can do
Endpoint endpoint = context.getEndpoint("activemq:my.queue");
PollingConsumer consumer = endpoint.createPollingConsumer();
Exchange exchange = consumer.receive();
Notice in Camel 2.0 we have introduced the ConsumerTemplate.
There are 3 main polling methods on PollingConsumer
451
Method name
Description
receive()
Waits until a message is available and then returns it;
potentially blocking forever
CH AP T E R 10 - PAT T E R N A P P E N D I X
receive(long)
Attempts to receive a message exchange, waiting up to
the given timeout and returning null if no message
exchange could be received within the time available
receiveNoWait()
Attempts to receive a message exchange immediately
without waiting and returning null if a message
exchange is not available yet
ConsumerTemplate
Available as of Camel 2.0
The ConsumerTemplate is a template much like Spring's JmsTemplate or
JdbcTemplate supporting the Polling Consumer EIP. With the template you can
consume Exchanges from an Endpoint.
The template supports the 3 operations above, but also including
convenient methods for returning the body, etc consumeBody.
The example from above using ConsumerTemplate is:
Exchange exchange = consumerTemplate.receive("activemq:my.queue");
Or to extract and get the body you can do:
Object body = consumerTemplate.receiveBody("activemq:my.queue");
And you can provide the body type as a parameter and have it returned as
the type:
String body = consumerTemplate.receiveBody("activemq:my.queue", String.class);
You get hold of a ConsumerTemplate from the CamelContext with the
createConsumerTemplate operation:
ConsumerTemplate consumer = context.createConsumerTemplate();
Using ConsumerTemplate with Spring DSL
With the Spring DSL we can declare the consumer in the CamelContext with
the consumerTemplate tag, just like the ProducerTemplate. The example
below illustrates this:
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
452
<camelContext xmlns="http://camel.apache.org/schema/spring">
<!-- define a producer template -->
<template id="producer"/>
<!-- define a consumer template -->
<consumerTemplate id="consumer"/>
<route>
<from uri="seda:foo"/>
<to id="result" uri="mock:result"/>
</route>
</camelContext>
Then we can get leverage Spring to inject the ConsumerTemplate in our java
class. The code below is part of an unit test but it shows how the consumer
and producer can work together.
@ContextConfiguration
public class SpringConsumerTemplateTest extends AbstractJUnit38SpringContextTests {
@Autowired
private ProducerTemplate producer;
@Autowired
private ConsumerTemplate consumer;
@EndpointInject(ref = "result")
private MockEndpoint mock;
public void testConsumeTemplate() throws Exception {
// we expect Hello World received in our mock endpoint
mock.expectedBodiesReceived("Hello World");
// we use the producer template to send a message to the seda:start endpoint
producer.sendBody("seda:start", "Hello World");
// we consume the body from seda:start
String body = consumer.receiveBody("seda:start", String.class);
assertEquals("Hello World", body);
// and then we send the body again to seda:foo so it will be routed to the
mock
// endpoint so our unit test can complete
producer.sendBody("seda:foo", body);
// assert mock received the body
mock.assertIsSatisfied();
}
}
453
CH AP T E R 10 - PAT T E R N A P P E N D I X
Timer based polling consumer
In this sample we use a Timer to schedule a route to be started every 5th
second and invoke our bean MyCoolBean where we implement the business
logic for the Polling Consumer. Here we want to consume all messages from
a JMS queue, process the message and send them to the next queue.
First we setup our route as:
MyCoolBean cool = new MyCoolBean();
cool.setProducer(template);
cool.setConsumer(consumer);
from("activemq:queue.foo").to("mock:result");
from("timer://foo?period=1000").bean(cool, "someBusinessLogic");
And then we have out logic in our bean:
public static class MyCoolBean {
private volatile int count;
private ConsumerTemplate consumer;
private ProducerTemplate producer;
public void setConsumer(ConsumerTemplate consumer) {
this.consumer = consumer;
}
public void setProducer(ProducerTemplate producer) {
this.producer = producer;
}
public void someBusinessLogic() {
// loop to empty queue
while (true) {
// receive the message from the queue
String msg = consumer.receiveBodyNoWait("activemq:queue.inbox",
String.class);
if (msg == null) {
// no more messages in queue
break;
}
// do something with body
msg = "Hello " + msg;
// send it to the next queue
producer.sendBodyAndHeader("activemq:queue.foo", msg, "number", count++);
}
}
}
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
454
Scheduled Poll Components
Quite a few inbound Camel endpoints use a scheduled poll pattern to receive
messages and push them through the Camel processing routes. That is to
say externally from the client the endpoint appears to use an Event Driven
Consumer but internally a scheduled poll is used to monitor some kind of
state or resource and then fire message exchanges.
Since this a such a common pattern, polling components can extend the
ScheduledPollConsumer base class which makes it simpler to implement this
pattern.
There is also the Quartz Component which provides scheduled delivery of
messages using the Quartz enterprise scheduler.
For more details see:
• PollingConsumer
• Scheduled Polling Components
◦ ScheduledPollConsumer
◦ Atom
◦ File
◦ FTP
◦ iBATIS
◦ JPA
◦ Mail
◦ Quartz
◦ SNMP
◦ AWS-SQS
ScheduledPollConsumer Options
The ScheduledPollConsumer supports the following options:
455
Option
Description
pollStrategy
Camel 2.0: A pluggable
org.apache.camel.PollingConsumerPollStrategy
allowing you to provide your custom implementation to
control error handling usually occurred during the poll
operation before an Exchange have been created and
being routed in Camel. In other words the error occurred
while the polling was gathering information, for instance
access to a file network failed so Camel cannot access it to
scan for files. The default implementation will log the
caused exception at WARN level and ignore it.
CH AP T E R 10 - PAT T E R N A P P E N D I X
About error handling and scheduled polling consumers
ScheduledPollConsumer is scheduled based and its run method is invoked
periodically based on schedule settings. But errors can also occur when a poll
being executed. For instance if Camel should poll a file network, and this
network resource is not available then a java.io.IOException could occur.
As this error happens before any Exchange has been created and prepared
for routing, then the regular Error handling in Camel does not apply. So what
does the consumer do then? Well the exception is propagated back to the
run method where its handled. Camel will by default log the exception at
WARN level and then ignore it. At next schedule the error could have been
resolved and thus being able to poll the endpoint successfully.
Controlling the error handling using
PollingConsumerPollStrategy
Available as of Camel 2.0
org.apache.camel.PollingConsumerPollStrategy is a pluggable strategy
that you can configure on the ScheduledPollConsumer. The default
implementation
org.apache.camel.impl.DefaultPollingConsumerPollStrategy will log
the caused exception at WARN level and then ignore this issue.
The strategy interface provides the following 3 methods
▪ begin
▪ void begin(Consumer consumer, Endpoint endpoint)
▪ begin (Camel 2.3)
▪ boolean begin(Consumer consumer, Endpoint endpoint)
▪ commit
▪ void commit(Consumer consumer, Endpoint endpoint)
▪ commit (Camel 2.6)
▪ void commit(Consumer consumer, Endpoint endpoint,
int polledMessages)
▪ rollback
▪ boolean rollback(Consumer consumer, Endpoint
endpoint, int retryCounter, Exception e) throws
Exception
In Camel 2.3 onwards the begin method returns a boolean which indicates
whether or not to skipping polling. So you can implement your custom logic
and return false if you do not want to poll this time.
In Camel 2.6 onwards the commit method has an additional parameter
containing the number of message that was actually polled. For example if
there was no messages polled, the value would be zero, and you can react
accordingly.
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
456
The most interesting is the rollback as it allows you do handle the caused
exception and decide what to do.
For instance if we want to provide a retry feature to a scheduled consumer
we can implement the PollingConsumerPollStrategy method and put the
retry logic in the rollback method. Lets just retry up till 3 times:
public boolean rollback(Consumer consumer, Endpoint endpoint, int retryCounter,
Exception e) throws Exception {
if (retryCounter < 3) {
// return true to tell Camel that it should retry the poll immediately
return true;
}
// okay we give up do not retry anymore
return false;
}
Notice that we are given the Consumer as a parameter. We could use this to
restart the consumer as we can invoke stop and start:
// error occurred lets restart the consumer, that could maybe resolve the issue
consumer.stop();
consumer.start();
Notice: If you implement the begin operation make sure to avoid throwing
exceptions as in such a case the poll operation is not invoked and Camel will
invoke the rollback directly.
Configuring an Endpoint to use
PollingConsumerPollStrategy
To configure an Endpoint to use a custom PollingConsumerPollStrategy
you use the option pollStrategy. For example in the file consumer below we
want to use our custom strategy defined in the Registry with the bean id
myPoll:
from("file://inbox/?pollStrategy=#myPoll").to("activemq:queue:inbox")
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
457
CH AP T E R 10 - PAT T E R N A P P E N D I X
See Also
▪ POJO Consuming
▪ Batch Consumer
Competing Consumers
Camel supports the Competing Consumers from the EIP patterns using a few
different components.
You can use the following components to implement competing
consumers:• SEDA for SEDA based concurrent processing using a thread pool
• JMS for distributed SEDA based concurrent processing with queues
which support reliable load balancing, failover and clustering.
Enabling Competing Consumers with JMS
To enable Competing Consumers you just need to set the
concurrentConsumers property on the JMS endpoint.
For example
from("jms:MyQueue?concurrentConsumers=5").bean(SomeBean.class);
or in Spring DSL
<route>
<from uri="jms:MyQueue?concurrentConsumers=5"/>
<to uri="bean:someBean"/>
</route>
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
458
Or just run multiple JVMs of any ActiveMQ or JMS route
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
Message Dispatcher
Camel supports the Message Dispatcher from the EIP patterns using various
approaches.
You can use a component like JMS with selectors to implement a Selective
Consumer as the Message Dispatcher implementation. Or you can use an
Endpoint as the Message Dispatcher itself and then use a Content Based
Router as the Message Dispatcher.
See Also
•
•
•
•
459
JMS
Selective Consumer
Content Based Router
Endpoint
CH AP T E R 10 - PAT T E R N A P P E N D I X
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
Selective Consumer
The Selective Consumer from the EIP patterns can be implemented in two
ways
The first solution is to provide a Message Selector to the underlying URIs
when creating your consumer. For example when using JMS you can specify a
selector parameter so that the message broker will only deliver messages
matching your criteria.
The other approach is to use a Message Filter which is applied; then if the
filter matches the message your consumer is invoked as shown in the
following example
Using the Fluent Builders
RouteBuilder builder = new RouteBuilder() {
public void configure() {
errorHandler(deadLetterChannel("mock:error"));
from("seda:a")
.filter(header("foo").isEqualTo("bar"))
.process(myProcessor);
}
};
Using the Spring XML Extensions
<bean id="myProcessor" class="org.apache.camel.builder.MyProcessor"/>
<camelContext errorHandlerRef="errorHandler" xmlns="http://camel.apache.org/schema/
spring">
<route>
<from uri="seda:a"/>
<filter>
<xpath>$foo = 'bar'</xpath>
<process ref="myProcessor"/>
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
460
</filter>
</route>
</camelContext>
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
Durable Subscriber
Camel supports the Durable Subscriber from the EIP patterns using the JMS
component which supports publish & subscribe using Topics with support for
non-durable and durable subscribers.
Another alternative is to combine the Message Dispatcher or Content
Based Router with File or JPA components for durable subscribers then
something like SEDA for non-durable.
See Also
•
•
•
•
•
•
•
461
JMS
File
JPA
Message Dispatcher
Selective Consumer
Content Based Router
Endpoint
CH AP T E R 10 - PAT T E R N A P P E N D I X
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
Idempotent Consumer
The Idempotent Consumer from the EIP patterns is used to filter out
duplicate messages.
This pattern is implemented using the IdempotentConsumer class. This
uses an Expression to calculate a unique message ID string for a given
message exchange; this ID can then be looked up in the
IdempotentRepository to see if it has been seen before; if it has the message
is consumed; if its not then the message is processed and the ID is added to
the repository.
The Idempotent Consumer essentially acts like a Message Filter to filter
out duplicates.
Camel will add the message id eagerly to the repository to detect
duplication also for Exchanges currently in progress.
On completion Camel will remove the message id from the repository if the
Exchange failed, otherwise it stays there.
Camel provides the following Idempotent Consumer implementations:
▪ MemoryIdempotentRepository
▪ FileIdempotentRepository
▪ JdbcMessageIdRepository (Available as of Camel 2.7)
▪ JpaMessageIdRepository
Options
The Idempotent Consumer has the following options:
Option
Default
Description
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
462
eager
messageIdRepositoryRef
skipDuplicate
true
Camel 2.0: Eager controls whether
Camel adds the message to the
repository before or after the
exchange has been processed. If
enabled before then Camel will be
able to detect duplicate messages
even when messages are currently in
progress. By disabling Camel will only
detect duplicates when a message
has successfully been processed.
null
A reference to a
IdempotentRepository to lookup in
the registry. This option is mandatory
when using XML DSL.
true
Camel 2.8: Sets whether to skip
duplicate messages. If set to false
then the message will be continued.
However the Exchange has been
marked as a duplicate by having the
Exchange.DUPLICATE_MESSAG
exchange property set to a
Boolean.TRUE value.
Using the Fluent Builders
The following example will use the header myMessageId to filter out
duplicates
RouteBuilder builder = new RouteBuilder() {
public void configure() {
errorHandler(deadLetterChannel("mock:error"));
from("seda:a")
.idempotentConsumer(header("myMessageId"),
MemoryIdempotentRepository.memoryIdempotentRepository(200))
.to("seda:b");
}
};
The above example will use an in-memory based MessageIdRepository which
can easily run out of memory and doesn't work in a clustered environment.
So you might prefer to use the JPA based implementation which uses a
database to store the message IDs which have been processed
463
CH AP T E R 10 - PAT T E R N A P P E N D I X
from("direct:start").idempotentConsumer(
header("messageId"),
jpaMessageIdRepository(lookup(JpaTemplate.class), PROCESSOR_NAME)
).to("mock:result");
In the above example we are using the header messageId to filter out
duplicates and using the collection myProcessorName to indicate the
Message ID Repository to use. This name is important as you could process
the same message by many different processors; so each may require its
own logical Message ID Repository.
For further examples of this pattern in use you could look at the junit test
case
Spring XML example
The following example will use the header myMessageId to filter out
duplicates
<!-- repository for the idempotent consumer -->
<bean id="myRepo"
class="org.apache.camel.processor.idempotent.MemoryIdempotentRepository"/>
<camelContext xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="direct:start"/>
<idempotentConsumer messageIdRepositoryRef="myRepo">
<!-- use the messageId header as key for identifying duplicate messages
-->
<header>messageId</header>
<!-- if not a duplicate send it to this mock endpoint -->
<to uri="mock:result"/>
</idempotentConsumer>
</route>
</camelContext>
How to handle duplicate messages in the route
Available as of Camel 2.8
You can now set the skipDuplicate option to false which instructs the
idempotent consumer to route duplicate messages as well. However the
duplicate message has been marked as duplicate by having a property on
the Exchange set to true. We can leverage this fact by using a Content Based
Router or Message Filter to detect this and handle duplicate messages.
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
464
For example in the following example we use the Message Filter to send
the message to a duplicate endpoint, and then stop continue routing that
message.
Listing 63. Filter duplicate messages
from("direct:start")
// instruct idempotent consumer to not skip duplicates as we will filter then our
self
.idempotentConsumer(header("messageId")).messageIdRepository(repo).skipDuplicate(false)
.filter(property(Exchange.DUPLICATE_MESSAGE).isEqualTo(true))
// filter out duplicate messages by sending them to someplace else and then
stop
.to("mock:duplicate")
.stop()
.end()
// and here we process only new messages (no duplicates)
.to("mock:result");
The sample example in XML DSL would be:
Listing 64. Filter duplicate messages
<!-- idempotent repository, just use a memory based for testing -->
<bean id="myRepo"
class="org.apache.camel.processor.idempotent.MemoryIdempotentRepository"/>
<camelContext xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="direct:start"/>
<!-- we do not want to skip any duplicate messages -->
<idempotentConsumer messageIdRepositoryRef="myRepo" skipDuplicate="false">
<!-- use the messageId header as key for identifying duplicate messages
-->
<header>messageId</header>
<!-- we will to handle duplicate messages using a filter -->
<filter>
<!-- the filter will only react on duplicate messages, if this
property is set on the Exchange -->
<property>CamelDuplicateMessage</property>
<!-- and send the message to this mock, due its part of an unit test
-->
<!-- but you can of course do anything as its part of the route -->
<to uri="mock:duplicate"/>
<!-- and then stop -->
<stop/>
</filter>
<!-- here we route only new messages -->
<to uri="mock:result"/>
</idempotentConsumer>
</route>
</camelContext>
465
CH AP T E R 10 - PAT T E R N A P P E N D I X
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
Transactional Client
Camel recommends supporting the Transactional Client from the EIP patterns
using spring transactions.
Transaction Oriented Endpoints (Camel Toes) like JMS support using a
transaction for both inbound and outbound message exchanges. Endpoints
that support transactions will participate in the current transaction context
that they are called from.
You should use the SpringRouteBuilder to setup the routes since you will
need to setup the spring context with the TransactionTemplates that will
define the transaction manager configuration and policies.
For inbound endpoint to be transacted, they normally need to be
configured to use a Spring PlatformTransactionManager. In the case of the
JMS component, this can be done by looking it up in the spring context.
You first define needed object in the spring configuration.
<bean id="jmsTransactionManager"
class="org.springframework.jms.connection.JmsTransactionManager">
<property name="connectionFactory" ref="jmsConnectionFactory" />
</bean>
<bean id="jmsConnectionFactory"
class="org.apache.activemq.ActiveMQConnectionFactory">
<property name="brokerURL" value="tcp://localhost:61616"/>
</bean>
Then you look them up and use them to create the JmsComponent.
PlatformTransactionManager transactionManager = (PlatformTransactionManager)
spring.getBean("jmsTransactionManager");
ConnectionFactory connectionFactory = (ConnectionFactory)
spring.getBean("jmsConnectionFactory");
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
466
Convention over configuration
In Camel 2.0 onwards we have improved the default configuration
reducing the number of Spring XML gobble you need to configure.
In this wiki page we provide the Camel 1.x examples and the same
2.0 example that requires less XML setup.
Configuration of Redelivery
The redelivery in transacted mode is not handled by Camel but by
the backing system (the transaction manager). In such cases you
should resort to the backing system how to configure the redelivery.
JmsComponent component = JmsComponent.jmsComponentTransacted(connectionFactory,
transactionManager);
component.getConfiguration().setConcurrentConsumers(1);
ctx.addComponent("activemq", component);
Transaction Policies
Outbound endpoints will automatically enlist in the current transaction
context. But what if you do not want your outbound endpoint to enlist in the
same transaction as your inbound endpoint? The solution is to add a
Transaction Policy to the processing route. You first have to define transaction
policies that you will be using. The policies use a spring TransactionTemplate
under the covers for declaring the transaction demarcation to use. So you
will need to add something like the following to your spring xml:
<bean id="PROPAGATION_REQUIRED"
class="org.apache.camel.spring.spi.SpringTransactionPolicy">
<property name="transactionManager" ref="jmsTransactionManager"/>
</bean>
<bean id="PROPAGATION_REQUIRES_NEW"
class="org.apache.camel.spring.spi.SpringTransactionPolicy">
<property name="transactionManager" ref="jmsTransactionManager"/>
<property name="propagationBehaviorName" value="PROPAGATION_REQUIRES_NEW"/>
</bean>
Then in your SpringRouteBuilder, you just need to create new
SpringTransactionPolicy objects for each of the templates.
467
CH AP T E R 10 - PAT T E R N A P P E N D I X
public void configure() {
...
Policy requried = bean(SpringTransactionPolicy.class, "PROPAGATION_REQUIRED"));
Policy requirenew = bean(SpringTransactionPolicy.class,
"PROPAGATION_REQUIRES_NEW"));
...
}
Once created, you can use the Policy objects in your processing routes:
// Send to bar in a new transaction
from("activemq:queue:foo").policy(requirenew).to("activemq:queue:bar");
// Send to bar without a transaction.
from("activemq:queue:foo").policy(notsupported ).to("activemq:queue:bar");
Camel 1.x - Database Sample
In this sample we want to ensure that two endpoints is under transaction
control. These two endpoints inserts data into a database.
The sample is in its full as a unit test.
First of all we setup the usual spring stuff in its configuration file. Here we
have defined a DataSource to the HSQLDB and a most importantly
the Spring DataSoruce TransactionManager that is doing the heavy lifting of
ensuring our transactional policies. You are of course free to use any
of the Spring based TransactionMananger, eg. if you are in a full blown J2EE
container you could use JTA or the WebLogic or WebSphere specific
managers.
We use the required transaction policy that we define as the
PROPOGATION_REQUIRED spring bean. And as last we have our book service
bean that does the business logic
and inserts data in the database as our core business logic.
<!-- datasource to the database -->
<bean id="dataSource"
class="org.springframework.jdbc.datasource.DriverManagerDataSource">
<property name="driverClassName" value="org.hsqldb.jdbcDriver"/>
<property name="url" value="jdbc:hsqldb:mem:camel"/>
<property name="username" value="sa"/>
<property name="password" value=""/>
</bean>
<!-- spring transaction manager -->
<bean id="txManager"
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
468
class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
<property name="dataSource" ref="dataSource"/>
</bean>
<!-- policy for required transaction used in our Camel routes -->
<bean id="PROPAGATION_REQUIRED"
class="org.apache.camel.spring.spi.SpringTransactionPolicy">
<property name="transactionManager" ref="txManager"/>
<property name="propagationBehaviorName" value="PROPAGATION_REQUIRED"/>
</bean>
<!-- bean for book business logic -->
<bean id="bookService" class="org.apache.camel.spring.interceptor.BookService">
<property name="dataSource" ref="dataSource"/>
</bean>
In our Camel route that is Java DSL based we setup the transactional policy,
wrapped as a Policy.
// Notice that we use the SpringRouteBuilder that has a few more features than
// the standard RouteBuilder
return new SpringRouteBuilder() {
public void configure() throws Exception {
// lookup the transaction policy
SpringTransactionPolicy required = lookup("PROPAGATION_REQUIRED",
SpringTransactionPolicy.class);
// use this error handler instead of DeadLetterChannel that is the default
// Notice: transactionErrorHandler is in SpringRouteBuilder
if (isUseTransactionErrorHandler()) {
// useTransactionErrorHandler is only used for unit testing to reuse code
// for doing a 2nd test without this transaction error handler, so ignore
// this. For spring based transaction, end users are encouraged to use the
// transaction error handler instead of the default DeadLetterChannel.
errorHandler(transactionErrorHandler(required));
}
Then we are ready to define our Camel routes. We have two routes: 1 for
success conditions, and 1 for a forced rollback condition.
This is after all based on a unit test.
// set the required policy for this route
from("direct:okay").policy(required).
setBody(constant("Tiger in Action")).beanRef("bookService").
setBody(constant("Elephant in Action")).beanRef("bookService");
// set the required policy for this route
from("direct:fail").policy(required).
setBody(constant("Tiger in Action")).beanRef("bookService").
setBody(constant("Donkey in Action")).beanRef("bookService");
469
CH AP T E R 10 - PAT T E R N A P P E N D I X
As its a unit test we need to setup the database and this is easily done with
Spring JdbcTemplate
Error formatting macro: snippet: java.lang.IndexOutOfBoundsException:
Index: 20, Size: 20
And our core business service, the book service, will accept any books except
the Donkeys.
public class BookService {
private SimpleJdbcTemplate jdbc;
public BookService() {
}
public void setDataSource(DataSource ds) {
jdbc = new SimpleJdbcTemplate(ds);
}
public void orderBook(String title) throws Exception {
if (title.startsWith("Donkey")) {
throw new IllegalArgumentException("We don't have Donkeys, only Camels");
}
// create new local datasource to store in DB
jdbc.update("insert into books (title) values (?)", title);
}
}
Then we are ready to fire the tests. First to commit condition:
public void testTransactionSuccess() throws Exception {
template.sendBody("direct:okay", "Hello World");
int count = jdbc.queryForInt("select count(*) from books");
assertEquals("Number of books", 3, count);
}
And lastly the rollback condition since the 2nd book is a Donkey book:
public void testTransactionRollback() throws Exception {
try {
template.sendBody("direct:fail", "Hello World");
} catch (RuntimeCamelException e) {
// expected as we fail
assertIsInstanceOf(RuntimeCamelException.class, e.getCause());
assertTrue(e.getCause().getCause() instanceof IllegalArgumentException);
assertEquals("We don't have Donkeys, only Camels",
e.getCause().getCause().getMessage());
}
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
470
int count = jdbc.queryForInt("select count(*) from books");
assertEquals("Number of books", 1, count);
}
Camel 1.x - JMS Sample
In this sample we want to listen for messages on a queue and process the
messages with our business logic java code and send them along. Since its
based on a unit test the destination is a mock endpoint.
This time we want to setup the camel context and routes using the Spring
XML syntax.
<!-- here we define our camel context -->
<camel:camelContext id="myroutes">
<!-- and now our route using the XML syntax -->
<camel:route errorHandlerRef="errorHandler">
<!-- 1: from the jms queue -->
<camel:from uri="activemq:queue:okay"/>
<!-- 2: setup the transactional boundaries to require a transaction -->
<camel:transacted ref="PROPAGATION_REQUIRED"/>
<!-- 3: call our business logic that is myProcessor -->
<camel:process ref="myProcessor"/>
<!-- 4: if success then send it to the mock -->
<camel:to uri="mock:result"/>
</camel:route>
</camel:camelContext>
<!-- this bean is our business logic -->
<bean id="myProcessor"
class="org.apache.camel.component.jms.tx.JMSTransactionalClientTest$MyProcessor"/>
Since the rest is standard XML stuff its nothing fancy now for the reader:
<!-- the transactional error handler -->
<bean id="errorHandler"
class="org.apache.camel.spring.spi.TransactionErrorHandlerBuilder">
<property name="springTransactionPolicy" ref="PROPAGATION_REQUIRED"/>
</bean>
<bean id="poolConnectionFactory"
class="org.apache.activemq.pool.PooledConnectionFactory">
<property name="maxConnections" value="8"/>
<property name="connectionFactory" ref="jmsConnectionFactory"/>
</bean>
<bean id="jmsConnectionFactory" class="org.apache.activemq.ActiveMQConnectionFactory">
<property name="brokerURL"
value="vm://localhost?broker.persistent=false&amp;broker.useJmx=false"/>
471
CH AP T E R 10 - PAT T E R N A P P E N D I X
</bean>
<bean id="jmsTransactionManager"
class="org.springframework.jms.connection.JmsTransactionManager">
<property name="connectionFactory" ref="poolConnectionFactory"/>
</bean>
<bean id="jmsConfig" class="org.apache.camel.component.jms.JmsConfiguration">
<property name="connectionFactory" ref="poolConnectionFactory"/>
<property name="transactionManager" ref="jmsTransactionManager"/>
<property name="transacted" value="true"/>
<property name="concurrentConsumers" value="1"/>
</bean>
<bean id="activemq" class="org.apache.activemq.camel.component.ActiveMQComponent">
<property name="configuration" ref="jmsConfig"/>
</bean>
<bean id="PROPAGATION_REQUIRED"
class="org.apache.camel.spring.spi.SpringTransactionPolicy">
<property name="transactionManager" ref="jmsTransactionManager"/>
</bean>
Our business logic is set to handle the incomming messages and fail the first
two times. When its a success it responds with a Bye World message.
public static class MyProcessor implements Processor {
private int count;
public void process(Exchange exchange) throws Exception {
if (++count <= 2) {
throw new IllegalArgumentException("Forced Exception number " + count +
", please retry");
}
exchange.getIn().setBody("Bye World");
exchange.getIn().setHeader("count", count);
}
}
And our unit test is tested with this java code. Notice that we expect the Bye
World message to be delivered at the 3rd attempt.
MockEndpoint mock = getMockEndpoint("mock:result");
mock.expectedMessageCount(1);
mock.expectedBodiesReceived("Bye World");
// success at 3rd attempt
mock.message(0).header("count").isEqualTo(3);
template.sendBody("activemq:queue:okay", "Hello World");
mock.assertIsSatisfied();
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
472
Camel 1.x - Spring based configuration
In Camel 1.4 we have introduced the concept of configuration of the error
handlers using spring XML configuration. The sample below demonstrates
that you can configure transaction error handlers in Spring XML as spring
beans. These can then be set as global, per route based or per policy based
error handler. The latter has been demonstrated in the samples above. This
sample is the database sample configured in Spring XML.
Notice that we have defined two error handler, one per route. The first
route uses the transaction error handler, and the 2nd uses no error handler
at all.
<!-- here we define our camel context -->
<camel:camelContext id="myroutes">
<!-- first route with transaction error handler -->
<!-- here we refer to our transaction error handler we define in this Spring XML
file -->
<!-- in this route the transactionErrorHandler is used -->
<camel:route errorHandlerRef="transactionErrorHandler">
<!-- 1: from the jms queue -->
<camel:from uri="activemq:queue:okay"/>
<!-- 2: setup the transactional boundaries to require a transaction -->
<camel:transacted ref="required"/>
<!-- 3: call our business logic that is myProcessor -->
<camel:process ref="myProcessor"/>
<!-- 4: if success then send it to the mock -->
<camel:to uri="mock:result"/>
</camel:route>
<!-- 2nd route with no error handling -->
<!-- this route doens't use error handler, in fact the spring bean with id
noErrorHandler -->
<camel:route errorHandlerRef="noErrorHandler">
<camel:from uri="activemq:queue:bad"/>
<camel:to uri="log:bad"/>
</camel:route>
</camel:camelContext>
The following snippet is the Spring XML configuration to setup the error
handlers in pure spring XML:
<!-- camel policy we refer to in our route -->
<bean id="required" class="org.apache.camel.spring.spi.SpringTransactionPolicy">
<property name="transactionTemplate" ref="PROPAGATION_REQUIRED"/>
</bean>
<!-- the standard spring transaction template for required -->
<bean id="PROPAGATION_REQUIRED"
473
CH AP T E R 10 - PAT T E R N A P P E N D I X
class="org.springframework.transaction.support.TransactionTemplate">
<property name="transactionManager" ref="jmsTransactionManager"/>
</bean>
<!-- the transaction error handle we refer to from the route -->
<bean id="transactionErrorHandler"
class="org.apache.camel.spring.spi.TransactionErrorHandlerBuilder">
<property name="transactionTemplate" ref="PROPAGATION_REQUIRED"/>
</bean>
<!-- the no error handler -->
<bean id="noErrorHandler" class="org.apache.camel.builder.NoErrorHandlerBuilder"/>
DelayPolicy (@deprecated)
DelayPolicy is a new policy introduced in Camel 1.5, to replaces the
RedeliveryPolicy used in Camel 1.4. Notice the transactionErrorHandler
can be configured with a DelayPolicy to set a fixed delay in millis between
each redelivery attempt. Camel does this by sleeping the delay until
transaction is marked for rollback and the caused exception is rethrown.
This allows a simple redelivery interval that can be configured for
development mode or light production to avoid a rapid redelivery strategy
that can exhaust a system that constantly fails.
The DelayPolicy is @deprecated and removed in Camel 2.0. All redelivery
configuration should be configured on the back system.
We strongly recommend that you configure the backing system
for correct redelivery policy in your environment.
Camel 2.0 - Database Sample
In this sample we want to ensure that two endpoints is under transaction
control. These two endpoints inserts data into a database.
The sample is in its full as a unit test.
First of all we setup the usual spring stuff in its configuration file. Here we
have defined a DataSource to the HSQLDB and a most importantly
the Spring DataSoruce TransactionManager that is doing the heavy lifting of
ensuring our transactional policies. You are of course free to use any
of the Spring based TransactionMananger, eg. if you are in a full blown J2EE
container you could use JTA or the WebLogic or WebSphere specific
managers.
As we use the new convention over configuration we do not need to
configure a transaction policy bean, so we do not have any
PROPAGATION_REQUIRED beans.
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
474
All the beans needed to be configured is standard Spring beans only, eg.
there are no Camel specific configuration at all.
<!-- this example uses JDBC so we define a data source -->
<bean id="dataSource"
class="org.springframework.jdbc.datasource.DriverManagerDataSource">
<property name="driverClassName" value="org.hsqldb.jdbcDriver"/>
<property name="url" value="jdbc:hsqldb:mem:camel"/>
<property name="username" value="sa"/>
<property name="password" value=""/>
</bean>
<!-- spring transaction manager -->
<!-- this is the transaction manager Camel will use for transacted routes -->
<bean id="txManager"
class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
<property name="dataSource" ref="dataSource"/>
</bean>
<!-- bean for book business logic -->
<bean id="bookService" class="org.apache.camel.spring.interceptor.BookService">
<property name="dataSource" ref="dataSource"/>
</bean>
Then we are ready to define our Camel routes. We have two routes: 1 for
success conditions, and 1 for a forced rollback condition.
This is after all based on a unit test. Notice that we mark each route as
transacted using the transacted tag.
<camelContext xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="direct:okay"/>
<!-- we mark this route as transacted. Camel will lookup the spring
transaction manager
and use it by default. We can optimally pass in arguments to specify a
policy to use
that is configured with a spring transaction manager of choice. However
Camel supports
convention over configuration as we can just use the defaults out of the
box and Camel
that suites in most situations -->
<transacted/>
<setBody>
<constant>Tiger in Action</constant>
</setBody>
<bean ref="bookService"/>
<setBody>
<constant>Elephant in Action</constant>
</setBody>
<bean ref="bookService"/>
</route>
475
CH AP T E R 10 - PAT T E R N A P P E N D I X
<route>
<from uri="direct:fail"/>
<!-- we mark this route as transacted. See comments above. -->
<transacted/>
<setBody>
<constant>Tiger in Action</constant>
</setBody>
<bean ref="bookService"/>
<setBody>
<constant>Donkey in Action</constant>
</setBody>
<bean ref="bookService"/>
</route>
</camelContext>
That is all that is needed to configure a Camel route as being transacted. Just
remember to use the transacted DSL. The rest is standard Spring XML to
setup the transaction manager.
Camel 2.0 - JMS Sample
In this sample we want to listen for messages on a queue and process the
messages with our business logic java code and send them along. Since its
based on a unit test the destination is a mock endpoint.
First we configure the standard Spring XML to declare a JMS connection
factory, a JMS transaction manager and our ActiveMQ component that we use
in our routing.
<!-- setup JMS connection factory -->
<bean id="poolConnectionFactory"
class="org.apache.activemq.pool.PooledConnectionFactory">
<property name="maxConnections" value="8"/>
<property name="connectionFactory" ref="jmsConnectionFactory"/>
</bean>
<bean id="jmsConnectionFactory" class="org.apache.activemq.ActiveMQConnectionFactory">
<property name="brokerURL"
value="vm://localhost?broker.persistent=false&amp;broker.useJmx=false"/>
</bean>
<!-- setup spring jms TX manager -->
<bean id="jmsTransactionManager"
class="org.springframework.jms.connection.JmsTransactionManager">
<property name="connectionFactory" ref="poolConnectionFactory"/>
</bean>
<!-- define our activemq component -->
<bean id="activemq" class="org.apache.activemq.camel.component.ActiveMQComponent">
<property name="connectionFactory" ref="poolConnectionFactory"/>
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
476
<!-- define the jms consumer/producer as transacted -->
<property name="transacted" value="true"/>
<!-- setup the transaction manager to use -->
<!-- if not provided then Camel will automatic use a JmsTransactionManager,
however if you
for instance use a JTA transaction manager then you must configure it -->
<property name="transactionManager" ref="jmsTransactionManager"/>
</bean>
And then we configure our routes. Notice that all we have to do is mark the
route as transacted using the transacted tag.
<camelContext xmlns="http://camel.apache.org/schema/spring">
<!-- disable JMX during testing -->
<jmxAgent id="agent" disabled="true"/>
<route>
<!-- 1: from the jms queue -->
<from uri="activemq:queue:okay"/>
<!-- 2: mark this route as transacted -->
<transacted/>
<!-- 3: call our business logic that is myProcessor -->
<process ref="myProcessor"/>
<!-- 4: if success then send it to the mock -->
<to uri="mock:result"/>
</route>
</camelContext>
<bean id="myProcessor"
class="org.apache.camel.component.jms.tx.JMSTransactionalClientTest$MyProcessor"/>
USING MULTIPLE ROUTES WITH DIFFERENT PROPAGATION
BEHAVIORS
Available as of Camel 2.2
Suppose you want to route a message through two routes and by which the
2nd route should run in its own transaction. How do you do that? You use
propagation behaviors for that where you configure it as follows:
▪ The first route use PROPAGATION_REQUIRED
▪ The second route use PROPAGATION_REQUIRES_NEW
This is configured in the Spring XML file:
<bean id="PROPAGATION_REQUIRED"
class="org.apache.camel.spring.spi.SpringTransactionPolicy">
<property name="transactionManager" ref="txManager"/>
<property name="propagationBehaviorName" value="PROPAGATION_REQUIRED"/>
</bean>
477
CH AP T E R 10 - PAT T E R N A P P E N D I X
Transaction error handler
When a route is marked as transacted using transacted Camel will
automatic use the TransactionErrorHandler as Error Handler. It
supports basically the same feature set as the DefaultErrorHandler,
so you can for instance use Exception Clause as well.
<bean id="PROPAGATION_REQUIRES_NEW"
class="org.apache.camel.spring.spi.SpringTransactionPolicy">
<property name="transactionManager" ref="txManager"/>
<property name="propagationBehaviorName" value="PROPAGATION_REQUIRES_NEW"/>
</bean>
Then in the routes you use transacted DSL to indicate which of these two
propagations it uses.
from("direct:mixed")
// using required
.transacted("PROPAGATION_REQUIRED")
// all these steps will be okay
.setBody(constant("Tiger in Action")).beanRef("bookService")
.setBody(constant("Elephant in Action")).beanRef("bookService")
// continue on route 2
.to("direct:mixed2");
from("direct:mixed2")
// tell Camel that if this route fails then only rollback this last route
// by using (rollback only *last*)
.onException(Exception.class).markRollbackOnlyLast().end()
// using a different propagation which is requires new
.transacted("PROPAGATION_REQUIRES_NEW")
// this step will be okay
.setBody(constant("Lion in Action")).beanRef("bookService")
// this step will fail with donkey
.setBody(constant("Donkey in Action")).beanRef("bookService");
Notice how we have configured the onException in the 2nd route to indicate
in case of any exceptions we should handle it and just rollback this
transaction.
This is done using the markRollbackOnlyLast which tells Camel to only do it
for the current transaction and not globally.
See Also
• Error handling in Camel
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
478
• TransactionErrorHandler
• Error Handler
• JMS
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
Messaging Gateway
Camel has several endpoint components that support the Messaging
Gateway from the EIP patterns.
Components like Bean and CXF provide a a way to bind a Java interface to
the message exchange.
However you may want to read the Using CamelProxy documentation as a
true Messaging Gateway EIP solution.
Another approach is to use @Produce which you can read about in POJO
Producing which also can be used as a Messaging Gateway EIP solution.
See Also
•
•
•
•
•
Bean
CXF
Using CamelProxy
POJO Producing
Spring Remoting
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
479
CH AP T E R 10 - PAT T E R N A P P E N D I X
Service Activator
Camel has several endpoint components that support the Service Activator
from the EIP patterns.
Components like Bean, CXF and Pojo provide a a way to bind the message
exchange to a Java interface/service where the route defines the endpoints
and wires it up to the bean.
In addition you can use the Bean Integration to wire messages to a bean
using annotation.
See Also
• Bean
• Pojo
• CXF
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
SYSTEM MANAGEMENT
Detour
The Detour from the EIP patterns allows you to send messages through
additional steps if a control condition is met. It can be useful for turning on
extra validation, testing, debugging code when needed.
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
480
Available in Camel 1.5.
Example
In this example we essentially have a route like
from("direct:start").to("mock:result") with a conditional detour to the
mock:detour endpoint in the middle of the route..
from("direct:start").choice()
.when().method("controlBean", "isDetour").to("mock:detour").end()
.to("mock:result");
Using the Spring XML Extensions
<route>
<from uri="direct:start"/>
<choice>
<when>
<method bean="controlBean" method="isDetour"/>
<to uri="mock:detour"/>
</when>
</choice>
<to uri="mock:result"/>
</split>
</route>
whether the detour is turned on or off is decided by the ControlBean. So,
when the detour is on the message is routed to mock:detour and then
mock:result. When the detour is off, the message is routed to mock:result.
For full details, check the example source here:
camel-core/src/test/java/org/apache/camel/processor/DetourTest.java
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
481
CH AP T E R 10 - PAT T E R N A P P E N D I X
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
Wire Tap
The Wire Tap from the EIP patterns allows you to route messages to a
separate tap location while it is forwarded to the ultimate destination.
Options
Name
Default
Value
Description
uri
Â
The endpoint uri where to send the wire tapped message. You should use either uri or ref.
ref
Â
Refers to the endpoint where to send the wire tapped message. You should use either uri or ref.
executorServiceRef
Â
Refers to a custom Thread Pool to be used when processing the wire tapped messages. If not set then
Camel uses a default thread pool.
processorRef
Â
Refers to a custom Processor to be used for creating a new message (eg the send a new message
mode). See below.
copy
true
Camel 2.3: Should a copy of the Exchange to used when wire tapping the message.
onPrepareRef
Â
Camel 2.8: Refers to a custom Processor to prepare the copy of the Exchange to be wire tapped. This
allows you to do any custom logic, such as deep-cloning the message payload if that's needed etc.
WireTap node
Available as of Camel 2.0
In Camel 2.0 we have introduced a new wireTap node for properly doing
wire taps. Camel will copy the original Exchange and set its Exchange Pattern
to InOnly as we want the tapped Exchange to be sent as a fire and forget
style. The tapped Exchange is then send in a separate thread so it can run in
parallel with the original
We have extended the wireTap to support two flavors when tapping an
Exchange
▪ send a copy of the original Exchange (the traditional wire tap)
▪ send a new Exchange, allowing you to populate the Exchange
beforehand
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
482
Sending a copy (traditional wire tap)
Using the Fluent Builders
from("direct:start")
.to("log:foo")
.wireTap("direct:tap")
.to("mock:result");
Using the Spring XML Extensions
<route>
<from uri="direct:start"/>
<to uri="log:foo"/>
<wireTap uri="direct:tap"/>
<to uri="mock:result"/>
</route>
Sending a new Exchange
Using the Fluent Builders
Camel supports either a processor or an Expression to populate the new
Exchange. Using processor gives you full power how the Exchange is
populated as you can set properties, headers etc. The Expression can only be
used to set the IN body.
From Camel 2.3 onwards the Expression or Processor is pre populated
with a copy of the original Exchange which allows you to access the original
message when you prepare the new Exchange to be sent. You can use the
copy option to indicate if you want this or not (default is enabled). If your
turn copy=false then it works as in Camel 2.2 or older, where the Exchange
always will be empty.
Below is the processor variation shown. This example is from Camel 2.3,
where we disable copy by passing in false. This will create a new empty
Exchange.
from("direct:start")
.wireTap("direct:foo", false, new Processor() {
public void process(Exchange exchange) throws Exception {
exchange.getIn().setBody("Bye World");
exchange.getIn().setHeader("foo", "bar");
}
}).to("mock:result");
from("direct:foo").to("mock:foo");
483
CH AP T E R 10 - PAT T E R N A P P E N D I X
And the Expression variation. This example is from Camel 2.3, where we
disable copy by passing in false. This will create a new empty Exchange.
from("direct:start")
.wireTap("direct:foo", false, constant("Bye World"))
.to("mock:result");
from("direct:foo").to("mock:foo");
Using the Spring XML Extensions
The processor variation, notice we use a processorRef attribute to refer to a
spring bean with this id:
<route>
<from uri="direct:start2"/>
<wireTap uri="direct:foo" processorRef="myProcessor"/>
<to uri="mock:result"/>
</route>
And the Expression variation, where the expression is defined in the body
tag:
<route>
<from uri="direct:start"/>
<wireTap uri="direct:foo">
<body><constant>Bye World</constant></body>
</wireTap>
<to uri="mock:result"/>
</route>
And this variation accesses the body of the original message and creates a
new Exchange which is based on the Expression.
It will create a new Exchange and have the body contain "Bye ORIGINAL
BODY MESSAGE HERE"
<route>
<from uri="direct:start"/>
<wireTap uri="direct:foo">
<body><simple>Bye ${body}</simple></body>
</wireTap>
<to uri="mock:result"/>
</route>
Camel 1.x
The following example shows how to route a request from an input queue:a
endpoint to the wire tap location queue:tap it is received by queue:b
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
484
Using the Fluent Builders
RouteBuilder builder = new RouteBuilder() {
public void configure() {
errorHandler(deadLetterChannel("mock:error"));
from("seda:a")
.multicast().to("seda:tap", "seda:b");
}
};
Using the Spring XML Extensions
<camelContext errorHandlerRef="errorHandler" xmlns="http://camel.apache.org/schema/
spring">
<route>
<from uri="seda:a"/>
<multicast>
<to uri="seda:tap"/>
<to uri="seda:b"/>
</multicast>
</route>
</camelContext>
Further Example
For another example of this pattern in use you could look at the wire tap test
case.
Sending a new Exchange and set headers in DSL
Available as of Camel 2.8
If you send a new messages using the Wire Tap then you could only set the
message body using an Expression from the DSL. If you also need to set new
headers you would have to use a Processor for that. So in Camel 2.8 onwards
we have improved this situation so you can now set headers as well in the
DSL.
The following example sends a new message which has
▪ "Bye World" as message body
▪ a header with key "id" with the value 123
▪ a header with key "date" which has current date as value
485
CH AP T E R 10 - PAT T E R N A P P E N D I X
Java DSL
from("direct:start")
// tap a new message and send it to direct:tap
// the new message should be Bye World with 2 headers
.wireTap("direct:tap")
// create the new tap message body and headers
.newExchangeBody(constant("Bye World"))
.newExchangeHeader("id", constant(123))
.newExchangeHeader("date", simple("${date:now:yyyyMMdd}"))
.end()
// here we continue routing the original messages
.to("mock:result");
// this is the tapped route
from("direct:tap")
.to("mock:tap");
XML DSL
The XML DSL is slightly different than Java DSL as how you configure the
message body and headers. In XML you use <body> and <setHeader> as
shown:
<route>
<from uri="direct:start"/>
<!-- tap a new message and send it to direct:tap -->
<!-- the new message should be Bye World with 2 headers -->
<wireTap uri="direct:tap">
<!-- create the new tap message body and headers -->
<body><constant>Bye World</constant></body>
<setHeader headerName="id"><constant>123</constant></setHeader>
<setHeader headerName="date"><simple>${date:now:yyyyMMdd}</simple></setHeader>
</wireTap>
<!-- here we continue routing the original message -->
<to uri="mock:result"/>
</route>
Using onPrepare to execute custom logic when preparing messages
Available as of Camel 2.8
See details at Multicast
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
486
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
LOG
How can I log processing a Message?
Camel provides many ways to log processing a message. Here is just some
examples:
▪ You can use the Log component which logs the Message content.
▪ You can use the Tracer which trace logs message flow.
▪ You can also use a Processor or Bean and log from Java code.
▪ You can use the log DSL.
Using log DSL
And in Camel 2.2 you can use the log DSL which allows you to use Simple
language to construct a dynamic message which gets logged.
For example you can do
from("direct:start").log("Processing ${id}").to("bean:foo");
Which will construct a String message at runtime using the Simple language.
The log message will by logged at INFO level using the route id as the log
name. By default a route is named route-1, route-2 etc. But you can use
the routeId("myCoolRoute") to set a route name of choice.
The log DSL have overloaded methods to set the logging level and/or name
as well.
from("direct:start").log(LoggingLevel.DEBUG, "Processing ${id}").to("bean:foo");
For example you can use this to log the file name being processed if you
consume files.
from("file://target/files").log(LoggingLevel.DEBUG, "Processing file
${file:name}").to("bean:foo");
487
CH AP T E R 10 - PAT T E R N A P P E N D I X
Difference between log in the DSL and Log component
The log DSL is much lighter and meant for logging human logs
such as Starting to do ... etc. It can only log a message based
on the Simple language. On the other hand Log component is a full
fledged component which involves using endpoints and etc. The
Log component is meant for logging the Message itself and you
have many URI options to control what you would like to be logged.
Using log DSL from Spring
In Spring DSL its also easy to use log DSL as shown below:
<route id="foo">
<from uri="direct:foo"/>
<log message="Got ${body}"/>
<to uri="mock:foo"/>
</route>
The log tag has attributes to set the message, loggingLevel and logName.
For example:
<route id="baz">
<from uri="direct:baz"/>
<log message="Me Got ${body}" loggingLevel="FATAL" logName="cool"/>
<to uri="mock:baz"/>
</route>
Using This Pattern
If you would like to use this EIP Pattern then please read the Getting Started,
you may also find the Architecture useful particularly the description of
Endpoint and URIs. Then you could try out some of the Examples first before
trying this pattern out.
CHA P TE R 1 0 - PAT TE R N A PPE NDIX
488
CHAPTER
11
°°°°
Component Appendix
There now follows the documentation on each Camel component.
ACTIVEMQ COMPONENT
The ActiveMQ component allows messages to be sent to a JMS Queue or
Topic or messages to be consumed from a JMS Queue or Topic using Apache
ActiveMQ.
This component is based on JMS Component and uses Spring's JMS support
for declarative transactions, using Spring's JmsTemplate for sending and a
MessageListenerContainer for consuming. All the options from the JMS
component also applies for this component.
To use this component make sure you have the activemq.jar or
activemq-core.jar on your classpath along with any Camel dependencies
such as camel-core.jar, camel-spring.jar and camel-jms.jar.
URI format
activemq:[queue:|topic:]destinationName
Where destinationName is an ActiveMQ queue or topic name. By default,
the destinationName is interpreted as a queue name. For example, to
connect to the queue, FOO.BAR, use:
activemq:FOO.BAR
You can include the optional queue: prefix, if you prefer:
activemq:queue:FOO.BAR
To connect to a topic, you must include the topic: prefix. For example, to
connect to the topic, Stocks.Prices, use:
489
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
activemq:topic:Stocks.Prices
Options
See Options on the JMS component as all these options also apply for this
component.
Configuring the Connection Factory
This test case shows how to add an ActiveMQComponent to the
CamelContext using the activeMQComponent() method while specifying the
brokerURL used to connect to ActiveMQ.
camelContext.addComponent("activemq",
activeMQComponent("vm://localhost?broker.persistent=false"));
Configuring the Connection Factory using Spring XML
You can configure the ActiveMQ broker URL on the ActiveMQComponent as
follows
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-2.0.xsd
http://camel.apache.org/schema/spring
http://camel.apache.org/schema/spring/camel-spring.xsd">
<camelContext xmlns="http://camel.apache.org/schema/spring">
</camelContext>
<bean id="activemq"
class="org.apache.activemq.camel.component.ActiveMQComponent">
<property name="brokerURL" value="tcp://somehost:61616"/>
</bean>
</beans>
Using connection pooling
When sending to an ActiveMQ broker using Camel it's recommended to use a
pooled connection factory to efficiently handle pooling of JMS connections,
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
490
sessions and producers. This is documented on the ActiveMQ Spring Support
page.
You can grab ActiveMQ's
org.apache.activemq.pool.PooledConnectionFactory with Maven:
<dependency>
<groupId>org.apache.activemq</groupId>
<artifactId>activemq-pool</artifactId>
<version>5.3.2</version>
</dependency>
And then setup the activemq Camel component as follows:
<bean id="jmsConnectionFactory"
class="org.apache.activemq.ActiveMQConnectionFactory">
<property name="brokerURL" value="tcp://localhost:61616" />
</bean>
<bean id="pooledConnectionFactory"
class="org.apache.activemq.pool.PooledConnectionFactory">
<property name="maxConnections" value="8" />
<property name="maximumActive" value="500" />
<property name="connectionFactory" ref="jmsConnectionFactory" />
</bean>
<bean id="jmsConfig"
class="org.apache.camel.component.jms.JmsConfiguration">
<property name="connectionFactory" ref="pooledConnectionFactory"/>
<property name="transacted" value="false"/>
<property name="concurrentConsumers" value="10"/>
</bean>
<bean id="activemq"
class="org.apache.activemq.camel.component.ActiveMQComponent">
<property name="configuration" ref="jmsConfig"/>
</bean>
Invoking MessageListener POJOs in a Camel route
The ActiveMQ component also provides a helper Type Converter from a JMS
MessageListener to a Processor. This means that the Bean component is
capable of invoking any JMS MessageListener bean directly inside any route.
So for example you can create a MessageListener in JMS like this:
public class MyListener implements MessageListener {
public void onMessage(Message jmsMessage) {
// ...
491
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
}
}
Then use it in your Camel route as follows
from("file://foo/bar").
bean(MyListener.class);
That is, you can reuse any of the Camel Components and easily integrate
them into your JMS MessageListener POJO!
Consuming Advisory Messages
ActiveMQ can generate Advisory messages which are put in topics that you
can consume. Such messages can help you send alerts in case you detect
slow consumers or to build statistics (number of messages/produced per day,
etc.) The following Spring DSL example shows you how to read messages
from a topic.
The below route starts by reading the topic ActiveMQ.Advisory.Connection.
To watch another topic, simply change the name according to the name
provided in ActiveMQ Advisory Messages documentation. The parameter
mapJmsMessage=false allows for converting the
org.apache.activemq.command.ActiveMqMessage object from the jms queue.
Next, the body received is converted into a String for the purposes of this
example and a carriage return is added. Finally, the string is added to a file
<route>
<from uri="activemq:topic:ActiveMQ.Advisory.Connection?mapJmsMessage=false" />
<convertBodyTo type="java.lang.String"/>
<transform>
<simple>${in.body}&#13;</simple>
</transform>
<to uri="file://data/activemq/
?fileExist=Append&amp;fileName=advisoryConnection-${date:now:yyyyMMdd}.txt" />
</route>
If you consume a message on a queue, you should see the following files
under the data/activemq folder :
advisoryConnection-20100312.txt
advisoryProducer-20100312.txt
and containing string:
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
492
ActiveMQMessage {commandId = 0, responseRequired = false,
messageId = ID:dell-charles-3258-1268399815140
-1:0:0:0:221, originalDestination = null, originalTransactionId = null,
producerId = ID:dell-charles-3258-1268399815140-1:0:0:0,
destination = topic://ActiveMQ.Advisory.Connection, transactionId = null,
expiration = 0, timestamp = 0, arrival = 0, brokerInTime = 1268403383468,
brokerOutTime = 1268403383468, correlationId = null, replyTo = null,
persistent = false, type = Advisory, priority = 0, groupID = null, groupSequence = 0,
targetConsumerId = null, compressed = false, userID = null, content = null,
marshalledProperties = org.apache.activemq.util.ByteSequence@17e2705,
dataStructure = ConnectionInfo {commandId = 1, responseRequired = true,
connectionId = ID:dell-charles-3258-1268399815140-2:50,
clientId = ID:dell-charles-3258-1268399815140-14:0, userName = , password = *****,
brokerPath = null, brokerMasterConnector = false, manageable = true,
clientMaster = true}, redeliveryCounter = 0, size = 0, properties =
{originBrokerName=master, originBrokerId=ID:dell-charles-3258-1268399815140-0:0,
originBrokerURL=vm://master}, readOnlyProperties = true, readOnlyBody = true,
droppable = false}
Getting Component JAR
You will need these dependencies
▪ camel-jms
▪ activemq-camel
camel-jms
You must have the camel-jms as dependency as ActiveMQ is an extension to
the JMS component.
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-jms</artifactId>
<version>1.6.0</version>
</dependency>
The ActiveMQ Camel component is released with the ActiveMQ project itself.
For Maven 2 users you simply just need to add the following dependency to
your project.
ActiveMQ 5.2 or later
<dependency>
<groupId>org.apache.activemq</groupId>
493
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
<artifactId>activemq-camel</artifactId>
<version>5.2.0</version>
</dependency>
ActiveMQ 5.1.0
For 5.1.0 its in the activemq-core library
<dependency>
<groupId>org.apache.activemq</groupId>
<artifactId>activemq-core</artifactId>
<version>5.1.0</version>
</dependency>
Alternatively you can download the component jar directly from the Maven
repository:
• activemq-camel-5.2.0.jar
• activemq-core-5.1.0.jar
ActiveMQ 4.x
For this version you must use the JMS component instead. Please be careful
to use a pooling connection factory as described in the JmsTemplate Gotchas
See Also
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
ACTIVEMQ JOURNAL COMPONENT
The ActiveMQ Journal Component allows messages to be stored in a rolling
log file and then consumed from that log file. The journal aggregates and
batches up concurrent writes so that the overhead of writing and waiting for
the disk sync is relatively constant regardless of how many concurrent writes
are being done. Therefore, this component supports and encourages you to
use multiple concurrent producers to the same journal endpoint.
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
494
Each journal endpoint uses a different log file and therefore write batching
(and the associated performance boost) does not occur between multiple
endpoints.
This component only supports one active consumer on the endpoint. After
the message is processed by the consumer's processor, the log file is marked
and only subsequent messages in the log file will get delivered to consumers.
URI format
activemq.journal:directoryName[?options]
So for example, to send to the journal located in the /tmp/data directory you
would use the following URI:
activemq.journal:/tmp/data
Options
Name
Default
Value
Description
syncConsume
false
If set to true, when the journal is marked after a message is consumed, wait till the Operating System has
verified the mark update is safely stored on disk.
syncProduce
true
If set to true, wait till the Operating System has verified the message is safely stored on disk.
You can append query options to the URI in the following format,
?option=value&option=value&...
Expected Exchange Data Types
The consumer of a Journal endpoint generates DefaultExchange objects with
the in message :
• header "journal" : set to the endpoint uri of the journal the message
came from
• header "location" : set to a Location which identifies where the
recored was stored on disk
• body : set to ByteSequence which contains the byte array data of the
stored message
The producer to a Journal endpoint expects an Exchange with an In message
where the body can be converted to a ByteSequence or a byte[].
See Also
• Configuring Camel
495
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
• Component
• Endpoint
• Getting Started
AMQP
The amqp: component supports the AMQP protocol using the Client API of
the Qpid project.
Maven users will need to add the following dependency to their pom.xml
for this component:
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-ampq</artifactId>
<version>x.x.x</version> <!-- use the same version as your Camel core version -->
</dependency>
URI format
amqp:[queue:|topic:]destinationName[?options]
You can specify all of the various configuration options of the JMS component
after the destination name.
See Also
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
SQS COMPONENT
Available as of Camel 2.6
The sqs component supports sending and receiving messages to Amazon's
SQS service.
URI Format
aws-sqs://queue-name[?options]
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
496
Prerequisites
You must have a valid Amazon Web Services developer account,
and be signed up to use Amazon SQS. More information are
available at Amazon SQS.
The queue will be created if they don't already exists.
You can append query options to the URI in the following format,
?options=value&option2=value&...
URI Options
Name
Default
Value
Context
Description
amazonSQSClient
null
Shared
Reference to a
com.amazonaws.services.sqs.AmazonS
Registry.
accessKey
null
Shared
Amazon AWS Access Key
secretKey
null
Shared
Amazon AWS Secret Key
amazonSQSEndpoint
null
Shared
The region with which the AWS-SQS clien
attributeNames
null
Consumer
A list of attributes to set in the
com.amazonaws.services.sqs.model.R
defaultVisibilityTimeout
null
Shared
The visibility timeout (in seconds) to set
com.amazonaws.services.sqs.model.C
deleteAfterRead
true
Consumer
Delete message from SQS after it has be
maxMessagesPerPoll
null
Consumer
The maximum number of messages whi
one poll to set in the
com.amazonaws.services.sqs.model.R
Consumer
The duration (in seconds) that the receiv
from subsequent retrieve requests after
ReceiveMessage request to set in the
com.amazonaws.services.sqs.model.R
visibilityTimeout
null
Batch Consumer
This component implements the Batch Consumer.
497
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
Required SQS component options
You have to provide the amazonSQSClient in the Registry or your
accessKey and secretKey to access the Amazon's SQS.
This allows you for instance to know how many messages exists in this
batch and for instance let the Aggregator aggregate this number of
messages.
Usage
Message headers set by the SQS producer
Header
Type
Description
CamelAwsSqsMD5OfBody
String
The MD5 checksum of the Amazon SQS message.
CamelAwsSqsMessageId
String
The Amazon SQS message ID.
Message headers set by the SQS consumer
Header
Type
Description
CamelAwsSqsMD5OfBody
String
The MD5 checksum of the Amazon SQS message.
CamelAwsSqsMessageId
String
The Amazon SQS message ID.
CamelAwsSqsReceiptHandle
String
The Amazon SQS message receipt handle.
CamelAwsSqsAttributes
Map<String, String>
The Amazon SQS message attributes.
Advanced AmazonSQSClient configuration
If your Camel Application is running behind a firewall or if you need to have
more control over the AmazonSQSClient configuration, you can create your
own instance:
AWSCredentials awsCredentials = new BasicAWSCredentials("myAccessKey", "mySecretKey");
ClientConfiguration clientConfiguration = new ClientConfiguration();
clientConfiguration.setProxyHost("http://myProxyHost");
clientConfiguration.setProxyPort(8080);
AmazonSQSClient client = new AmazonSQSClient(awsCredentials, clientConfiguration);
and refer to it in your Camel aws-sqs component configuration:
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
498
from("aws-sqs://MyQueue?amazonSQSClient=#amazonSQSClient&delay=5000&maxMessagesPerPoll=5")
.to("mock:result");
Dependencies
Maven users will need to add the following dependency to their pom.xml.
Listing 65. pom.xml
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-aws</artifactId>
<version>${camel-version}</version>
</dependency>
where ${camel-version} must be replaced by the actual version of Camel
(2.6 or higher).
See Also
•
•
•
•
▪
Configuring Camel
Component
Endpoint
Getting Started
AWS Component
ATOM COMPONENT
The atom: component is used for polling Atom feeds.
Camel will poll the feed every 60 seconds by default.
Note: The component currently only supports polling (consuming) feeds.
Maven users will need to add the following dependency to their pom.xml
for this component:
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-atom</artifactId>
<version>x.x.x</version>
<!-- use the same version as your Camel core version -->
</dependency>
499
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
URI format
atom://atomUri[?options]
Where atomUri is the URI to the Atom feed to poll.
Options
Property
Default
Description
splitEntries
true
If true Camel will poll the feed and for the subsequent polls return each entry poll by poll. If the
feed contains 7 entries then Camel will return the first entry on the first poll, the 2nd entry on the
next poll, until no more entries where as Camel will do a new update on the feed. If false then
Camel will poll a fresh feed on every invocation.
filter
true
Is only used by the split entries to filter the entries to return. Camel will default use the
UpdateDateFilter that only return new entries from the feed. So the client consuming from the
feed never receives the same entry more than once. The filter will return the entries ordered by
the newest last.
lastUpdate
null
Is only used by the filter, as the starting timestamp for selection never entries (uses the
entry.updated timestamp). Syntax format is: yyyy-MM-ddTHH:MM:ss. Example:
2007-12-24T17:45:59.
throttleEntries
true
Camel 2.5: Sets whether all entries identified in a single feed poll should be delivered
immediately. If true, only one entry is processed per consumer.delay. Only applicable when
splitEntries is set to true.
feedHeader
true
Sets whether to add the Abdera Feed object as a header.
sortEntries
false
If splitEntries is true, this sets whether to sort those entries by updated date.
consumer.delay
60000
Delay in millis between each poll.
consumer.initialDelay
1000
Millis before polling starts.
consumer.userFixedDelay
false
If true, use fixed delay between pools, otherwise fixed rate is used. See
ScheduledExecutorService in JDK for details.
You can append query options to the URI in the following format,
?option=value&option=value&...
Exchange data format
Camel will set the In body on the returned Exchange with the entries.
Depending on the splitEntries flag Camel will either return one Entry or a
List<Entry>.
Option
Value
Behavior
splitEntries
true
Only a single entry from the currently being processed feed is set: exchange.in.body(Entry)
splitEntries
false
The entire list of entries from the feed is set: exchange.in.body(List<Entry>)
Camel can set the Feed object on the In header (see feedHeader option to
disable this):
Message Headers
Camel atom uses these headers.
Header
Description
org.apache.camel.component.atom.feed
Camel 1.x: When consuming the org.apache.abdera.model.Feed object is set to this header.
CamelAtomFeed
Camel 2.0: When consuming the org.apache.abdera.model.Feed object is set to this header.
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
500
Samples
In this sample we poll James Strachan's blog.
from("atom://http://macstrac.blogspot.com/feeds/posts/default").to("seda:feeds");
In this sample we want to filter only good blogs we like to a SEDA queue. The
sample also shows how to setup Camel standalone, not running in any
Container or using Spring.
// This is the CamelContext that is the heart of Camel
private CamelContext context;
protected CamelContext createCamelContext() throws Exception {
// First we register a blog service in our bean registry
SimpleRegistry registry = new SimpleRegistry();
registry.put("blogService", new BlogService());
// Then we create the camel context with our bean registry
context = new DefaultCamelContext(registry);
// Then we add all the routes we need using the route builder DSL syntax
context.addRoutes(createMyRoutes());
return context;
}
/**
* This is the route builder where we create our routes using the Camel DSL
*/
protected RouteBuilder createMyRoutes() throws Exception {
return new RouteBuilder() {
public void configure() throws Exception {
// We pool the atom feeds from the source for further processing in the
seda queue
// we set the delay to 1 second for each pool as this is a unit test also
and we can
// not wait the default poll interval of 60 seconds.
// Using splitEntries=true will during polling only fetch one Atom Entry
at any given time.
// As the feed.atom file contains 7 entries, using this will require 7
polls to fetch the entire
// content. When Camel have reach the end of entries it will refresh the
atom feed from URI source
// and restart - but as Camel by default uses the UpdatedDateFilter it
will only deliver new
// blog entries to "seda:feeds". So only when James Straham updates his
blog with a new entry
// Camel will create an exchange for the seda:feeds.
from("atom:file:src/test/data/
feed.atom?splitEntries=true&consumer.delay=1000").to("seda:feeds");
501
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
// From the feeds we filter each blot entry by using our blog service
class
from("seda:feeds").filter().method("blogService",
"isGoodBlog").to("seda:goodBlogs");
// And the good blogs is moved to a mock queue as this sample is also
used for unit testing
// this is one of the strengths in Camel that you can also use the mock
endpoint for your
// unit tests
from("seda:goodBlogs").to("mock:result");
}
};
}
/**
* This is the actual junit test method that does the assertion that our routes is
working as expected
*/
@Test
public void testFiltering() throws Exception {
// create and start Camel
context = createCamelContext();
context.start();
// Get the mock endpoint
MockEndpoint mock = context.getEndpoint("mock:result", MockEndpoint.class);
// There should be at least two good blog entries from the feed
mock.expectedMinimumMessageCount(2);
// Asserts that the above expectations is true, will throw assertions exception
if it failed
// Camel will default wait max 20 seconds for the assertions to be true, if the
conditions
// is true sooner Camel will continue
mock.assertIsSatisfied();
// stop Camel after use
context.stop();
}
/**
* Services for blogs
*/
public class BlogService {
/**
* Tests the blogs if its a good blog entry or not
*/
public boolean isGoodBlog(Exchange exchange) {
Entry entry = exchange.getIn().getBody(Entry.class);
String title = entry.getTitle();
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
502
// We like blogs about Camel
boolean good = title.toLowerCase().contains("camel");
return good;
}
}
See Also
•
•
•
•
▪
Configuring Camel
Component
Endpoint
Getting Started
RSS
BEAN COMPONENT
The bean: component binds beans to Camel message exchanges.
URI format
bean:beanID[?options]
Where beanID can be any string which is used to look up the bean in the
Registry
Options
Name
Type
Default
Description
method
String
null
The method name from the bean that will be invoked. If not provided, Camel will try to
determine the method itself. In case of ambiguity an exception will be thrown. See Bean
Binding for more details. From Camel 2.8 onwards you can specify type qualifiers to pinpoint exact method to use for overloaded methods.
cache
boolean
false
If enabled, Camel will cache the result of the first Registry look-up. Cache can be enabled
if the bean in the Registry is defined as a singleton scope.
multiParameterArray
boolean
false
Camel 1.5: How to treat the parameters which are passed from the message body; if it is
true, the In message body should be an array of parameters.
You can append query options to the URI in the following format,
?option=value&option=value&...
503
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
Using
The object instance that is used to consume messages must be explicitly
registered with the Registry. For example, if you are using Spring you must
define the bean in the Spring configuration, spring.xml; or if you don't use
Spring, by registering the bean in JNDI.
// lets populate the context with the services we need
// note that we could just use a spring.xml file to avoid this step
JndiContext context = new JndiContext();
context.bind("bye", new SayService("Good Bye!"));
CamelContext camelContext = new DefaultCamelContext(context);
Once an endpoint has been registered, you can build Camel routes that use it
to process exchanges.
// lets add simple route
camelContext.addRoutes(new RouteBuilder() {
public void configure() {
from("direct:hello").to("bean:bye");
}
});
A bean: endpoint cannot be defined as the input to the route; i.e. you cannot
consume from it, you can only route from some inbound message Endpoint
to the bean endpoint as output. So consider using a direct: or queue:
endpoint as the input.
You can use the createProxy() methods on ProxyHelper to create a proxy
that will generate BeanExchanges and send them to any endpoint:
Endpoint endpoint = camelContext.getEndpoint("direct:hello");
ISay proxy = ProxyHelper.createProxy(endpoint, ISay.class);
String rc = proxy.say();
assertEquals("Good Bye!", rc);
And the same route using Spring DSL:
<route>
<from uri="direct:hello">
<to uri="bean:bye"/>
</route>
Bean as endpoint
Camel also supports invoking Bean as an Endpoint. In the route below:
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
504
<camelContext xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="direct:start"/>
<to uri="myBean"/>
<to uri="mock:results"/>
</route>
</camelContext>
<bean id="myBean" class="org.apache.camel.spring.bind.ExampleBean"/>
What happens is that when the exchange is routed to the myBean Camel will
use the Bean Binding to invoke the bean.
The source for the bean is just a plain POJO:
public class ExampleBean {
public String sayHello(String name) {
return "Hello " + name + "!";
}
}
Camel will use Bean Binding to invoke the sayHello method, by converting
the Exchange's In body to the String type and storing the output of the
method on the Exchange Out body.
Bean Binding
How bean methods to be invoked are chosen (if they are not specified
explicitly through the method parameter) and how parameter values are
constructed from the Message are all defined by the Bean Binding
mechanism which is used throughout all of the various Bean Integration
mechanisms in Camel.
See Also
•
•
•
•
•
•
•
505
Configuring Camel
Component
Endpoint
Getting Started
Class component
Bean Binding
Bean Integration
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
BEAN VALIDATION COMPONENT
Available as of Camel 2.3
The Validation component performs bean validation of the message body
using the Java Bean Validation API (JSR 303). Camel uses the reference
implementation, which is Hibernate Validator.
Maven users will need to add the following dependency to their pom.xml
for this component:
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-bean-validator</artifactId>
<version>x.x.x</version>
<!-- use the same version as your Camel core version -->
</dependency>
URI format
bean-validator:something[?options]
or
bean-validator://something[?options]
Where something must be present to provide a valid url
You can append query options to the URI in the following format,
?option=value&option=value&...
URI Options
Option
Default
Description
group
javax.validation.groups.Default
The custom validation group to use.
messageInterpolator
org.hibernate.validator.engine.
ResourceBundleMessageInterpolator
Reference to a custom
javax.validation.MessageInterpolator in the Registry.
traversableResolver
org.hibernate.validator.engine.resolver.
DefaultTraversableResolver
Reference to a custom
javax.validation.TraversableResolver in the Registry.
constraintValidatorFactory
org.hibernate.validator.engine.
ConstraintValidatorFactoryImpl
Reference to a custom
javax.validation.ConstraintValidatorFactory in the
Registry.
ServiceMix4/OSGi Deployment.
The bean-validator when deployed in an OSGi environment requires a little
help to accommodate the resource loading specified in JSR303, this was fixed
in Servicemix-Specs 1.6-SNAPSHOT.
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
506
Example
Assumed we have a java bean with the following annotations
Listing 66. Car.java
public class Car {
@NotNull
private String manufacturer;
@NotNull
@Size(min = 5, max = 14, groups = OptionalChecks.class)
private String licensePlate;
// getter and setter
}
and an interface definition for our custom validation group
Listing 67. OptionalChecks.java
public interface OptionalChecks {
}
with the following Camel route, only the @NotNull constraints on the
attributes manufacturer and licensePlate will be validated (Camel uses the
default group javax.validation.groups.Default).
from("direct:start")
.to("bean-validator://x")
.to("mock:end")
If you want to check the constraints from the group OptionalChecks, you
have to define the route like this
from("direct:start")
.to("bean-validator://x?group=OptionalChecks")
.to("mock:end")
If you want to check the constraints from both groups, you have to define a
new interface first
Listing 68. AllChecks.java
@GroupSequence({Default.class, OptionalChecks.class})
public interface AllChecks {
}
and then your route definition should looks like this
507
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
from("direct:start")
.to("bean-validator://x?group=AllChecks")
.to("mock:end")
And if you have to provide your own message interpolator, traversable
resolver and constraint validator factory, you have to write a route like this
<bean id="myMessageInterpolator" class="my.ConstraintValidatorFactory" />
<bean id="myTraversableResolver" class="my.TraversableResolver" />
<bean id="myConstraintValidatorFactory" class="my.ConstraintValidatorFactory" />
from("direct:start")
.to("bean-validator://x?group=AllChecks&messageInterpolator=#myMessageInterpolator
&traversableResolver=#myTraversableResolver&constraintValidatorFactory=#myConstraintValidatorFactory")
.to("mock:end")
It's also possible to describe your constraints as XML and not as Java
annotations. In this case, you have to provide the file META-INF/
validation.xml which could looks like this
Listing 69. validation.xml
<?xml version="1.0" encoding="UTF-8"?>
<validation-config
xmlns="http://jboss.org/xml/ns/javax/validation/configuration"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://jboss.org/xml/ns/javax/validation/configuration">
<default-provider>org.hibernate.validator.HibernateValidator</default-provider>
<message-interpolator>org.hibernate.validator.engine.ResourceBundleMessageInterpolator</message-interp
<traversable-resolver>org.hibernate.validator.engine.resolver.DefaultTraversableResolver</traversable-
<constraint-validator-factory>org.hibernate.validator.engine.ConstraintValidatorFactoryImpl</constrain
<constraint-mapping>/constraints-car.xml</constraint-mapping>
</validation-config>
and the constraints-car.xml file
Listing 70. constraints-car.xml
<?xml version="1.0" encoding="UTF-8"?>
<constraint-mappings xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://jboss.org/xml/ns/javax/validation/mapping
validation-mapping-1.0.xsd"
xmlns="http://jboss.org/xml/ns/javax/validation/mapping">
<default-package>org.apache.camel.component.bean.validator</default-package>
<bean class="CarWithoutAnnotations" ignore-annotations="true">
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
508
<field name="manufacturer">
<constraint annotation="javax.validation.constraints.NotNull"
/>
</field>
<field name="licensePlate">
<constraint annotation="javax.validation.constraints.NotNull"
/>
<constraint annotation="javax.validation.constraints.Size">
<groups>
<value>org.apache.camel.component.bean.validator.OptionalChecks</value>
</groups>
<element name="min">5</element>
<element name="max">14</element>
</constraint>
</field>
</bean>
</constraint-mappings>
See Also
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
BROWSE COMPONENT
Available as of Camel 2.0
The Browse component provides a simple BrowsableEndpoint which can
be useful for testing, visualisation tools or debugging. The exchanges sent to
the endpoint are all available to be browsed.
URI format
browse:someName
Where someName can be any string to uniquely identify the endpoint.
Sample
In the route below, we insert a browse: component to be able to browse the
Exchanges that are passing through:
509
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
from("activemq:order.in").to("browse:orderReceived").to("bean:processOrder");
We can now inspect the received exchanges from within the Java code:
private CamelContext context;
public void inspectRecievedOrders() {
BrowsableEndpoint browse = context.getEndpoint("browse:orderReceived",
BrowsableEndpoint.class);
List<Exchange> exchanges = browse.getExchanges();
...
// then we can inspect the list of received exchanges from Java
for (Exchange exchange : exchanges) {
String payload = exchange.getIn().getBody();
...
}
}
See Also
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
CACHE COMPONENT
Available as of Camel 2.1
The cache component enables you to perform caching operations using
EHCache as the Cache Implementation. The cache itself is created on
demand or if a cache of that name already exists then it is simply utilized
with its original settings.
This component supports producer and event based consumer endpoints.
The Cache consumer is an event based consumer and can be used to
listen and respond to specific cache activities. If you need to perform
selections from a pre-existing cache, used the processors defined for the
cache component.
Maven users will need to add the following dependency to their pom.xml
for this component:
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-cache</artifactId>
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
510
<version>x.x.x</version>
<!-- use the same version as your Camel core version -->
</dependency>
URI format
cache://cacheName[?options]
You can append query options to the URI in the following format,
?option=value&option=value&...
Options
Name
Default Value
Description
maxElementsInMemory
1000
The numer of elements that may be stored in the defined cache
memoryStoreEvictionPolicy
MemoryStoreEvictionPolicy.LFU
The number of elements that may be stored in the defined cache.
Options include
▪
MemoryStoreEvictionPolicy.LFU - Least frequently
used
▪
MemoryStoreEvictionPolicy.LRU - Least recently used
▪
MemoryStoreEvictionPolicy.FIFO - first in first out,
the oldest element by creation time
overflowToDisk
true
Specifies whether cache may overflow to disk
eternal
false
Sets whether elements are eternal. If eternal, timeouts are ignored
and the
element is never expired.
timeToLiveSeconds
300
The maximum time between creation time and when an element
expires.
Is only used if the element is not eternal
timeToIdleSeconds
300
The maximum amount of time between accesses before an
element expires
diskPersistent
true
Whether the disk store persists between restarts of the Virtual
Machine.
The default value is false.
diskExpiryThreadIntervalSeconds
120
The number of seconds between runs of the disk expiry thread. The
default value
is 120 seconds
cacheManagerFactory
null
Camel 2.3: If you want to use a custom factory which instantiates
and creates the EHCache net.sf.ehcache.CacheManager.
Sending/Receiving Messages to/from the cache
Message Headers up to Camel 2.7
Header
511
Description
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
CACHE_OPERATION
CACHE_KEY
The operation
▪
▪
▪
▪
▪
▪
to be performed on the cache. The valid options are
GET
CHECK
ADD
UPDATE
DELETE
DELETEALL
The GET and CHECK requires Camel 2.3 onwards.
The cache key used to store the Message in the cache. The cache key is optional if the CACHE_OPERATION is DELETEALL
Message Headers Camel 2.8+
Header
Description
CamelCacheOperation
The operation
▪
▪
▪
▪
▪
▪
CamelCacheKey
The cache key used to store the Message in the cache. The cache key is optional if the CamelCacheOperation is
CamelCacheDeleteAll
to be performed on the cache. The valid options are
CamelCacheGet
CamelCacheCheck
CamelCacheAdd
CamelCacheUpdate
CamelCacheDelete
CamelCacheDeleteAll
Cache Producer
Sending data to the cache involves the ability to direct payloads in
exchanges to be stored in a pre-existing or created-on-demand cache. The
mechanics of doing this involve
▪ setting the Message Exchange Headers shown above.
▪ ensuring that the Message Exchange Body contains the message
directed to the cache
Cache Consumer
Receiving data from the cache involves the ability of the CacheConsumer to
listen on a pre-existing or created-on-demand Cache using an event Listener
and receive automatic notifications when any cache activity take place (i.e
CamelCacheGet/CamelCacheUpdate/CamelCacheDelete/
CamelCacheDeleteAll). Upon such an activity taking place
▪ an exchange containing Message Exchange Headers and a Message
Exchange Body containing the just added/updated payload is placed
and sent.
▪ in case of a CamelCacheDeleteAll operation, the Message Exchange
Header CamelCacheKey and the Message Exchange Body are not
populated.
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
512
Header changes in Camel 2.8
The header names and supported values have changed to be
prefixed with 'CamelCache' and use mixed case. This makes them
easier to identify and keep separate from other headers. The
CacheConstants variable names remain unchanged, just their
values have been changed. Also, these headers are now being
removed from the exchange after the cache operation is performed.
Cache Processors
There are a set of nice processors with the ability to perform cache lookups
and selectively replace payload content at the
▪ body
▪ token
▪ xpath level
Cache Usage Samples
Example 1: Configuring the cache
from("cache://MyApplicationCache" +
"?maxElementsInMemory=1000" +
"&memoryStoreEvictionPolicy=" +
"MemoryStoreEvictionPolicy.LFU" +
"&overflowToDisk=true" +
"&eternal=true" +
"&timeToLiveSeconds=300" +
"&timeToIdleSeconds=true" +
"&diskPersistent=true" +
"&diskExpiryThreadIntervalSeconds=300")
Example 2: Adding keys to the cache
RouteBuilder builder = new RouteBuilder() {
public void configure() {
from("direct:start")
.setHeader(CacheConstants.CACHE_OPERATION,
constant(CacheConstants.CACHE_OPERATION_ADD))
.setHeader(CacheConstants.CACHE_KEY, constant("Ralph_Waldo_Emerson"))
.to("cache://TestCache1")
513
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
}
};
Example 2: Updating existing keys in a cache
RouteBuilder builder = new RouteBuilder() {
public void configure() {
from("direct:start")
.setHeader(CacheConstants.CACHE_OPERATION,
constant(CacheConstants.CACHE_OPERATION_UPDATE))
.setHeader(CacheConstants.CACHE_KEY, constant("Ralph_Waldo_Emerson"))
.to("cache://TestCache1")
}
};
Example 3: Deleting existing keys in a cache
RouteBuilder builder = new RouteBuilder() {
public void configure() {
from("direct:start")
.setHeader(CacheConstants.CACHE_OPERATION, constant(CacheConstants.CACHE_DELETE))
.setHeader(CacheConstants.CACHE_KEY", constant("Ralph_Waldo_Emerson"))
.to("cache://TestCache1")
}
};
Example 4: Deleting all existing keys in a cache
RouteBuilder builder = new RouteBuilder() {
public void configure() {
from("direct:start")
.setHeader(CacheConstants.CACHE_OPERATION,
constant(CacheConstants.CACHE_DELETEALL))
.to("cache://TestCache1");
}
};
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
514
Example 5: Notifying any changes registering in a Cache
to Processors and other Producers
RouteBuilder builder = new RouteBuilder() {
public void configure() {
from("cache://TestCache1")
.process(new Processor() {
public void process(Exchange exchange)
throws Exception {
String operation = (String)
exchange.getIn().getHeader(CacheConstants.CACHE_OPERATION);
String key = (String) exchange.getIn().getHeader(CacheConstants.CACHE_KEY);
Object body = exchange.getIn().getBody();
// Do something
}
})
}
};
Example 6: Using Processors to selectively replace
payload with cache values
RouteBuilder builder = new RouteBuilder() {
public void configure() {
//Message Body Replacer
from("cache://TestCache1")
.filter(header(CacheConstants.CACHE_KEY).isEqualTo("greeting"))
.process(new CacheBasedMessageBodyReplacer("cache://TestCache1","farewell"))
.to("direct:next");
//Message Token replacer
from("cache://TestCache1")
.filter(header(CacheConstants.CACHE_KEY).isEqualTo("quote"))
.process(new CacheBasedTokenReplacer("cache://TestCache1","novel","#novel#"))
.process(new CacheBasedTokenReplacer("cache://TestCache1","author","#author#"))
.process(new CacheBasedTokenReplacer("cache://TestCache1","number","#number#"))
.to("direct:next");
//Message XPath replacer
from("cache://TestCache1").
.filter(header(CacheConstants.CACHE_KEY).isEqualTo("XML_FRAGMENT"))
.process(new CacheBasedXPathReplacer("cache://TestCache1","book1","/books/book1"))
.process (new CacheBasedXPathReplacer("cache://TestCache1","book2","/books/
book2"))
.to("direct:next");
}
};
515
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
Example 7: Getting an entry from the Cache
from("direct:start")
// Prepare headers
.setHeader(CacheConstants.CACHE_OPERATION,
constant(CacheConstants.CACHE_OPERATION_GET))
.setHeader(CacheConstants.CACHE_KEY, constant("Ralph_Waldo_Emerson")).
.to("cache://TestCache1").
// Check if entry was not found
.choice().when(header(CacheConstants.CACHE_ELEMENT_WAS_FOUND).isNull()).
// If not found, get the payload and put it to cache
.to("cxf:bean:someHeavyweightOperation").
.setHeader(CacheConstants.CACHE_OPERATION,
constant(CacheConstants.CACHE_OPERATION_ADD))
.setHeader(CacheConstants.CACHE_KEY, constant("Ralph_Waldo_Emerson"))
.to("cache://TestCache1")
.end()
.to("direct:nextPhase");
Example 8: Checking for an entry in the Cache
Note: CHECK command tests existence of the entry in the cache but doesn't
place message to the body.
from("direct:start")
// Prepare headers
.setHeader(CacheConstants.CACHE_OPERATION,
constant(CacheConstants.CACHE_OPERATION_CHECK))
.setHeader(CacheConstants.CACHE_KEY, constant("Ralph_Waldo_Emerson")).
.to("cache://TestCache1").
// Check if entry was not found
.choice().when(header(CacheConstants.CACHE_ELEMENT_WAS_FOUND).isNull()).
// If not found, get the payload and put it to cache
.to("cxf:bean:someHeavyweightOperation").
.setHeader(CacheConstants.CACHE_OPERATION,
constant(CacheConstants.CACHE_OPERATION_ADD))
.setHeader(CacheConstants.CACHE_KEY, constant("Ralph_Waldo_Emerson"))
.to("cache://TestCache1")
.end();
Management of EHCache
EHCache has its own statistics and management from JMX.
Here's a snippet on how to expose them via JMX in a Spring application
context:
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
516
<bean id="ehCacheManagementService"
class="net.sf.ehcache.management.ManagementService" init-method="init"
lazy-init="false">
<constructor-arg>
<bean class="net.sf.ehcache.CacheManager" factory-method="getInstance"/>
</constructor-arg>
<constructor-arg>
<bean class="org.springframework.jmx.support.JmxUtils"
factory-method="locateMBeanServer"/>
</constructor-arg>
<constructor-arg value="true"/>
<constructor-arg value="true"/>
<constructor-arg value="true"/>
<constructor-arg value="true"/>
</bean>
Of course you can do the same thing in straight Java:
ManagementService.registerMBeans(CacheManager.getInstance(), mbeanServer, true, true,
true, true);
You can get cache hits, misses, in-memory hits, disk hits, size stats this way.
You can also change CacheConfiguration parameters on the fly.
CLASS COMPONENT
Available as of Camel 2.4
The class: component binds beans to Camel message exchanges. It works
in the same way as the Bean component but instead of looking up beans
from a Registry it creates the bean based on the class name.
URI format
class:className[?options]
Where className is the fully qualified class name to create and use as
bean.
Options
517
Name
Type
Default
Description
method
String
null
The method name that bean will be invoked. If not provided, Camel will try to pick the
method itself. In case of ambiguity an exception is thrown. See Bean Binding for more
details.
multiParameterArray
boolean
false
How to treat the parameters which are passed from the message body; if it is true, the In
message body should be an array of parameters.
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
You can append query options to the URI in the following format,
?option=value&option=value&...
Using
You simply use the class component just as the Bean component but by
specifying the fully qualified classname instead.
For example to use the MyFooBean you have to do as follows:
from("direct:start").to("class:org.apache.camel.component.bean.MyFooBean").to("mock:result");
You can also specify which method to invoke on the MyFooBean, for example
hello:
from("direct:start").to("class:org.apache.camel.component.bean.MyFooBean?method=hello").to("mock:resul
SETTING PROPERTIES ON THE CREATED INSTANCE
In the endpoint uri you can specify properties to set on the created instance,
for example if it has a setPrefix method:
from("direct:start")
.to("class:org.apache.camel.component.bean.MyPrefixBean?prefix=Bye")
.to("mock:result");
And you can also use the # syntax to refer to properties to be looked up in
the Registry.
from("direct:start")
.to("class:org.apache.camel.component.bean.MyPrefixBean?cool=#foo")
.to("mock:result");
Which will lookup a bean from the Registry with the id foo and invoke the
setCool method on the created instance of the MyPrefixBean class.
See Also
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
518
See more
See more details at the Bean component as the class component
works in much the same way.
• Bean
• Bean Binding
• Bean Integration
COMETD COMPONENT
The cometd: component is a transport for working with the jetty
implementation of the cometd/bayeux protocol.
Using this component in combination with the dojo toolkit library it's possible
to push Camel messages directly into the browser using an AJAX based
mechanism.
Maven users will need to add the following dependency to their pom.xml
for this component:
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-cometd</artifactId>
<version>x.x.x</version>
<!-- use the same version as your Camel core version -->
</dependency>
URI format
cometd://host:port/channelName[?options]
The channelName represents a topic that can be subscribed to by the
Camel endpoints.
Examples
cometd://localhost:8080/service/mychannel
cometds://localhost:8443/service/mychannel
where cometds: represents an SSL configured endpoint.
519
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
See this blog entry by David Greco who contributed this component to
Apache Camel, for a full sample.
Options
Name
Default
Value
Description
resourceBase
Â
The root directory for the web resources or classpath. Use the protocol file: or classpath: depending if
you want that the component loads the resource from file system or classpath. Classpath is required for
OSGI deployment where the resources are packaged in the jar
timeout
240000
The server side poll timeout in milliseconds. This is how long the server will hold a reconnect request
before responding.
interval
0
The client side poll timeout in milliseconds. How long a client will wait between reconnects
maxInterval
30000
The max client side poll timeout in milliseconds. A client will be removed if a connection is not received
in this time.
multiFrameInterval
1500
The client side poll timeout, if multiple connections are detected from the same browser.
jsonCommented
true
If true, the server will accept JSON wrapped in a comment and will generate JSON wrapped in a
comment. This is a defence against Ajax Hijacking.
logLevel
1
0=none, 1=info, 2=debug.
You can append query options to the URI in the following format,
?option=value&option=value&...
Here is some examples on How to pass the parameters
For file (for webapp resources located in the Web Application directory -->
cometd://localhost:8080?resourceBase=file./webapp
For classpath (when by example the web resources are packaged inside the
webapp folder --> cometd://localhost:8080?resourceBase=classpath:webapp
Authentication
Available as of Camel 2.8
You can configure custom SecurityPolicy and Extension's to the
CometdComponent which allows you to use authentication as documented
here
See Also
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
CONTEXT COMPONENT
Available as of Camel 2.7
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
520
The context component allows you to create new Camel Components
from a CamelContext with a number of routes which is then treated as a
black box, allowing you to refer to the local endpoints within the component
from other CamelContexts.
It is similar to the Routebox component in idea, though the Context
component tries to be really simple for end users; just a simple convention
over configuration approach to refer to local endpoints inside the
CamelContext Component.
Maven users will need to add the following dependency to their pom.xml
for this component:
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-context</artifactId>
<version>x.x.x</version>
<!-- use the same version as your Camel core version -->
</dependency>
URI format
context:camelContextId:localEndpointName[?options]
Or you can omit the "context:" prefix.
camelContextId:localEndpointName[?options]
• camelContextId is the ID you used to register the CamelContext
into the Registry.
• localEndpointName can be a valid Camel URI evaluated within the
black box CamelContext. Or it can be a logical name which is
mapped to any local endpoints. For example if you locally have
endpoints like direct:invoices and seda:purchaseOrders inside a
CamelContext of id supplyChain, then you can just use the URIs
supplyChain:invoices or supplyChain:purchaseOrders to omit
the physical endpoint kind and use pure logical URIs.
You can append query options to the URI in the following format,
?option=value&option=value&...
Example
In this example we'll create a black box context, then we'll use it from
another CamelContext.
521
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
Defining the context component
First you need to create a CamelContext, add some routes in it, start it and
then register the CamelContext into the Registry (JNDI, Spring, Guice or OSGi
etc).
This can be done in the usual Camel way from this test case (see the
createRegistry() method); this example shows Java and JNDI being used...
// lets create our black box as a camel context and a set of routes
DefaultCamelContext blackBox = new DefaultCamelContext(registry);
blackBox.setName("blackBox");
blackBox.addRoutes(new RouteBuilder() {
@Override
public void configure() throws Exception {
// receive purchase orders, lets process it in some way then send an invoice
// to our invoice endpoint
from("direct:purchaseOrder").
setHeader("received").constant("true").
to("direct:invoice");
}
});
blackBox.start();
registry.bind("accounts", blackBox);
Notice in the above route we are using pure local endpoints (direct and
seda). Also note we expose this CamelContext using the accounts ID. We
can do the same thing in Spring via
<camelContext id="accounts" xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="direct:purchaseOrder"/>
...
<to uri="direct:invoice"/>
</route>
</camelContext>
Using the context component
Then in another CamelContext we can then refer to this "accounts black box"
by just sending to accounts:purchaseOrder and consuming from
accounts:invoice.
If you prefer to be more verbose and explicit you could use
context:accounts:purchaseOrder or even
context:accounts:direct://purchaseOrder if you prefer. But using logical
endpoint URIs is preferred as it hides the implementation detail and provides
a simple logical naming scheme.
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
522
For example if we wish to then expose this accounts black box on some
middleware (outside of the black box) we can do things like...
<camelContext xmlns="http://camel.apache.org/schema/spring">
<route>
<!-- consume from an ActiveMQ into the black box -->
<from uri="activemq:Accounts.PurchaseOrders"/>
<to uri="accounts:purchaseOrders"/>
</route>
<route>
<!-- lets send invoices from the black box to a different ActiveMQ Queue -->
<from uri="accounts:invoice"/>
<to uri="activemq:UK.Accounts.Invoices"/>
</route>
</camelContext>
Naming endpoints
A context component instance can have many public input and output
endpoints that can be accessed from outside it's CamelContext. When there
are many it is recommended that you use logical names for them to hide the
middleware as shown above.
However when there is only one input, output or error/dead letter endpoint
in a component we recommend using the common posix shell names in, out
and err
CRYPTO COMPONENT FOR DIGITAL SIGNATURES
Available as of Camel 2.3
Using Camel cryptographic endpoints and Java's Cryptographic extension
it is easy to create Digital Signatures for Exchanges. Camel provides a pair of
flexible endpoints which get used in concert to create a signature for an
exchange in one part of the exchange's workflow and then verify the
signature in a later part of the workflow.
Maven users will need to add the following dependency to their pom.xml
for this component:
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-crypto</artifactId>
<version>x.x.x</version>
<!-- use the same version as your Camel core version -->
</dependency>
523
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
Introduction
Digital signatures make use Asymmetric Cryptographic techniques to sign
messages. From a (very) high level, the algorithms use pairs of
complimentary keys with the special property that data encrypted with one
key can only be decrypted with the other. One, the private key, is closely
guarded and used to 'sign' the message while the other, public key, is shared
around to anyone interested in verifying your messages. Messages are
signed by encrypting a digest of the message with the private key. This
encrypted digest is transmitted along with the message. On the other side
the verifier recalculates the message digest and uses the public key to
decrypt the the digest in the signature. If both digest match the verifier
knows only the holder of the private key could have created the signature.
Camel uses the Signature service from the Java Cryptographic Extension
to do all the heavy cryptographic lifting required to create exchange
signatures. The following are some excellent sources for explaining the
mechanics of Cryptography, Message digests and Digital Signatures and how
to leverage them with the JCE.
▪ Bruce Schneier's Applied Cryptography
▪ Beginning Cryptography with Java by David Hook
▪ The ever insightful, Wikipedia Digital_signatures
URI format
As mentioned Camel provides a pair of crypto endpoints to create and verify
signatures
crypto:sign:name[?options]
crypto:verify:name[?options]
• crypto:sign creates the signature and stores it in the Header keyed
by the constant Exchange.SIGNATURE, i.e.
"CamelDigitalSignature".
• crypto:verify will read in the contents of this header and do the
verification calculation.
In order to correctly function, sign and verify need to share a pair of keys,
sign requiring a PrivateKey and verify a PublicKey (or a Certificate
containing one). Using the JCE is is very simple to generate these key pairs
but it is usually most secure to use a KeyStore to house and share your keys.
The DSL is very flexible about how keys are supplied and provides a number
of mechanisms.
Note a crypto:sign endpoint is typically defined in one route and the
complimentary crypto:verify in another, though for simplicity in the
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
524
examples they appear one after the other. It goes without saying that both
sign and verify should be configured identically.
Options
Name
Type
Default
Description
algorithm
String
DSA
The name of the JCE Signature algorithm that will be used.
alias
String
null
An alias name that will be used to select a key from the keystore.
bufferSize
Integer
2048
the size of the buffer used in the signature process.
certificate
Certificate
null
A Certificate used to verify the signature of the exchange's payload. Either this or a Public Key
is required.
keystore
KeyStore
null
A reference to a JCE Keystore that stores keys and certificates used to sign and verify.
provider
String
null
The name of the JCE Security Provider that should be used.
privateKey
PrivatKey
null
The private key used to sign the exchange's payload.
publicKey
PublicKey
null
The public key used to verify the signature of the exchange's payload.
secureRandom
secureRandom
null
A reference to a SecureRandom object that wil lbe used to initialize the Signature service.
password
char[]
null
The password for the keystore.
Using
1) Raw keys
The most basic way to way to sign an verify an exchange is with a KeyPair as
follows.
from("direct:keypair").to("crypto:sign://basic?privateKey=#myPrivateKey",
"crypto:verify://basic?publicKey=#myPublicKey", "mock:result");
The same can be achieved with the Spring XML Extensions using references
to keys
<route>
<from uri="direct:keypair"/>
<to uri="crypto:sign://basic?privateKey=#myPrivateKey" />
<to uri="crypto:verify://basic?publicKey=#myPublicKey" />
<to uri="mock:result"/>
</route>
2) KeyStores and Aliases.
The JCE provides a very versatile KeyStore for housing pairs of PrivateKeys
and Certificates keeping them encrypted and password protected. They can
be retrieved from it by applying an alias to the retrieval apis. There are a
number of ways to get keys and Certificates into a keystore most often this is
525
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
done with the external 'keytool' application. This is a good example of using
keytool to create a KeyStore with a self signed Cert and Private key.
The examples use a Keystore with a key and cert aliased by 'bob'. The
password for the keystore and the key is 'letmein'
The following shows how to use a Keystore via the Fluent builders, it also
shows how to load and initialize the keystore.
from("direct:keystore").to("crypto:sign://keystore?keystore=#keystore&alias=bob&password=letmein",
"crypto:verify://keystore?keystore=#keystore&alias=bob", "mock:result");
Again in Spring a ref is used to lookup an actual keystore instance.
<route>
<from uri="direct:keystore"/>
<to
uri="crypto:sign://keystore?keystore=#keystore&amp;alias=bob&amp;password=letmein" />
<to uri="crypto:verify://keystore?keystore=#keystore&amp;alias=bob" />
<to uri="mock:result"/>
</route>
3) Changing JCE Provider and Algorithm
Changing the Signature algorithm or the Security provider is a simple matter
of specifying their names. You will need to also use Keys that are compatible
with the algorithm you choose.
KeyPairGenerator keyGen = KeyPairGenerator.getInstance("RSA");
keyGen.initialize(512, new SecureRandom());
keyPair = keyGen.generateKeyPair();
PrivateKey privateKey = keyPair.getPrivate();
PublicKey publicKey = keyPair.getPublic();
// we can set the keys explicitly on the endpoint instances.
context.getEndpoint("crypto:sign://rsa?algorithm=MD5withRSA",
DigitalSignatureEndpoint.class).setPrivateKey(privateKey);
context.getEndpoint("crypto:verify://rsa?algorithm=MD5withRSA",
DigitalSignatureEndpoint.class).setPublicKey(publicKey);
from("direct:algorithm").to("crypto:sign://rsa?algorithm=MD5withRSA",
"crypto:verify://rsa?algorithm=MD5withRSA", "mock:result");
from("direct:provider").to("crypto:sign://provider?privateKey=#myPrivateKey&provider=SUN",
"crypto:verify://provider?publicKey=#myPublicKey&provider=SUN", "mock:result");
or
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
526
<route>
<from uri="direct:algorithm"/>
<to uri="crypto:sign://rsa?algorithm=MD5withRSA&amp;privateKey=#rsaPrivateKey" />
<to uri="crypto:verify://rsa?algorithm=MD5withRSA&amp;publicKey=#rsaPublicKey" />
<to uri="mock:result"/>
</route>
<route>
<from uri="direct:provider"/>
<to uri="crypto:sign://provider?privateKey=#myPrivateKey&amp;provider=SUN" />
<to uri="crypto:verify://provider?publicKey=#myPublicKey&amp;provider=SUN" />
<to uri="mock:result"/>
</route>
4) Changing the Signature Mesasge Header
It may be desirable to change the message header used to store the
signature. A different header name can be specified in the route definition as
follows
from("direct:signature-header").to("crypto:sign://another?privateKey=#myPrivateKey&signatureHeader=Ano
"crypto:verify://another?publicKey=#myPublicKey&signatureHeader=AnotherDigitalSignature",
"mock:result");
or
<route>
<from uri="direct:signature-header"/>
<to
uri="crypto:sign://another?privateKey=#myPrivateKey&amp;signatureHeader=AnotherDigitalSignature"
/>
<to
uri="crypto:verify://another?publicKey=#myPublicKey&amp;signatureHeader=AnotherDigitalSignature"
/>
<to uri="mock:result"/>
</route>
5) Changing the buffersize
In case you need to update the size of the buffer...
527
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
from("direct:buffersize").to("crypto:sign://buffer?privateKey=#myPrivateKey&buffersize=1024",
"crypto:verify://buffer?publicKey=#myPublicKey&buffersize=1024", "mock:result");
or
<route>
<from uri="direct:buffersize" />
<to uri="crypto:sign://buffer?privateKey=#myPrivateKey&amp;buffersize=1024" />
<to uri="crypto:verify://buffer?publicKey=#myPublicKey&amp;buffersize=1024" />
<to uri="mock:result"/>
</route>
6) Supplying Keys dynamically.
When using a Recipient list or similar EIP the recipient of an exchange can
vary dynamically. Using the same key across all recipients may neither be
feasible or desirable. It would be useful to be able to specify the signature
keys dynamically on a per exchange basis. The exchange could then be
dynamically enriched with the key of its target recipient prior to signing. To
facilitate this the signature mechanisms allow for keys to be supplied
dynamically via the message headers below
• Exchange.SIGNATURE_PRIVATE_KEY, "CamelSignaturePrivateKey"
• Exchange.SIGNATURE_PUBLIC_KEY_OR_CERT,
"CamelSignaturePublicKeyOrCert"
from("direct:headerkey-sign").to("crypto:sign://alias");
from("direct:headerkey-verify").to("crypto:verify://alias", "mock:result");
or
<route>
<from uri="direct:headerkey-sign"/>
<to uri="crypto:sign://headerkey" />
</route>
<route>
<from uri="direct:headerkey-verify"/>
<to uri="crypto:verify://headerkey" />
<to uri="mock:result"/>
</route>
Better again would be to dynamically supply a keystore alias. Again the alias
can be supplied in a message header
• Exchange.KEYSTORE_ALIAS, "CamelSignatureKeyStoreAlias"
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
528
from("direct:alias-sign").to("crypto:sign://alias?keystore=#keystore");
from("direct:alias-verify").to("crypto:verify://alias?keystore=#keystore",
"mock:result");
or
<route>
<from uri="direct:alias-sign"/>
<to uri="crypto:sign://alias?keystore=#keystore" />
</route>
<route>
<from uri="direct:alias-verify"/>
<to uri="crypto:verify://alias?keystore=#keystore" />
<to uri="mock:result"/>
</route>
The header would be set as follows
Exchange unsigned = getMandatoryEndpoint("direct:alias-sign").createExchange();
unsigned.getIn().setBody(payload);
unsigned.getIn().setHeader(DigitalSignatureConstants.KEYSTORE_ALIAS, "bob");
unsigned.getIn().setHeader(DigitalSignatureConstants.KEYSTORE_PASSWORD,
"letmein".toCharArray());
template.send("direct:alias-sign", unsigned);
Exchange signed = getMandatoryEndpoint("direct:alias-sign").createExchange();
signed.getIn().copyFrom(unsigned.getOut());
signed.getIn().setHeader(KEYSTORE_ALIAS, "bob");
template.send("direct:alias-verify", signed);
See Also
•
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
Crypto Crypto is also available as a Data Format
CXF COMPONENT
The cxf: component provides integration with Apache CXF for connecting to
JAX-WS services hosted in CXF.
• CXF Component
• URI format
• Options
• The descriptions of the dataformats
529
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
When using CXF as a consumer, the CXF Bean Component allows
you to factor out how message payloads are received from their
processing as a RESTful or SOAP web service. This has the potential
of using a multitude of transports to consume web services. The
bean component's configuration is also simpler and provides the
fastest method to implement web services using Camel and CXF.
•
•
•
•
•
•
How to enable CXF's LoggingOutInterceptor in MESSAGE mode
Description of relayHeaders option
Available in Release 1.6.1 and after (only in POJO mode)
Changes since Release 2.0
Configure the CXF endpoints with Spring
How to make the camel-cxf component use log4j instead of
java.util.logging
• How to let camel-cxf response message with xml start document
• How to consume a message from a camel-cxf endpoint in POJO data
format
• How to prepare the message for the camel-cxf endpoint in POJO data
format
• How to deal with the message for a camel-cxf endpoint in PAYLOAD
data format
• How to get and set SOAP headers in POJO mode
• How to get and set SOAP headers in PAYLOAD mode
• SOAP headers are not available in MESSAGE mode
• How to throw a SOAP Fault from Camel
• How to propagate a camel-cxf endpoint's request and response
context
• Attachment Support
• See Also
Maven users will need to add the following dependency to their pom.xml for
this component:
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-cxf</artifactId>
<version>x.x.x</version>
<!-- use the same version as your Camel core version -->
</dependency>
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
530
CXF dependencies
If you want to learn about CXF dependencies you can checkout the
WHICH-JARS text file.
URI format
cxf:bean:cxfEndpoint[?options]
Where cxfEndpoint represents a bean ID that references a bean in the
Spring bean registry. With this URI format, most of the endpoint details are
specified in the bean definition.
cxf://someAddress[?options]
Where someAddress specifies the CXF endpoint's address. With this URI
format, most of the endpoint details are specified using options.
For either style above, you can append options to the URI as follows:
cxf:bean:cxfEndpoint?wsdlURL=wsdl/hello_world.wsdl&dataFormat=PAYLOAD
Options
Name
Required
wsdlURL
No
Description
The location of the WSDL. It is obtained from endpoint address by default.
Example: file://local/wsdl/hello.wsdl or wsdl/hello.wsdl
serviceClass
Yes
The name of the SEI (Service Endpoint Interface) class. This class can have, but does not
require, JSR181 annotations.
Since 2.0, this option is only required by POJO mode. If the wsdlURL option is provided,
serviceClass is not required for PAYLOAD and MESSAGE mode. When wsdlURL option is used
without serviceClass, the serviceName and portName (endpointName for Spring
configuration) options MUST be provided. It is possible to use # notation to reference a
serviceClass object instance from the registry. E.g. serviceClass=#beanName.
Since 2.8, it is possible to omit both wsdlURL and serviceClass options for PAYLOAD and
MESSAGE mode. When they are omitted, arbitrary XML elements can be put in CxfPayload's
body in PAYLOAD mode to facilitate CXF Dispatch Mode.
Please be advised that the referenced object cannot be a Proxy (Spring AOP Proxy is
OK) as it relies on Object.getClass().getName() method for non Spring AOP Proxy.
Example: org.apache.camel.Hello
serviceClassInstance
No
Use either serviceClass or serviceClassInstance.
Deprecated in 2.x. In 1.6.x serviceClassInstance works like serviceClass=#beanName,
which looks up a serviceObject instance from the registry.
Example: serviceClassInstance=beanName
The service name this service is implementing, it maps to the wsdl:service@name.
serviceName
No
Required for camel-cxf consumer since camel-2.2.0 or if more than one serviceName is
present in WSDL.
Example: {http:Â//org.apache.camel}ServiceName
531
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
The port name this service is implementing, it maps to the wsdl:port@name.
portName
No
Required for camel-cxf consumer since camel-2.2.0 or if more than one portName is
present under serviceName.
Example: {http:Â//org.apache.camel}PortName
The data type messages supported by the CXF endpoint.
dataFormat
relayHeaders
No
No
Default: POJO
Example: POJO, PAYLOAD, MESSAGE
Available since 1.6.1. Please see the Description of relayHeaders option section for this
option in 2.0. Should a CXF endpoint relay headers along the route. Currently only available
when dataFormat=POJO
Default: true
Example: true, false
Which kind of operation that CXF endpoint producer will invoke
wrapped
wrappedStyle
No
No
Default: false
Example: true, false
New in 2.5.0 The WSDL style that describes how parameters are represented in the SOAP
body. If the value is false, CXF will chose the document-literal unwrapped style, If the value
is true, CXF will chose the document-literal wrapped style
Default: Null
Example: true, false
Will set the default bus when CXF endpoint create a bus by itself
setDefaultBus
No
bus
No
Default: false
Example: true, false
New in 2.0.0. A default bus created by CXF Bus Factory. Use # notation to reference a bus
object from the registry. The referenced object must be an instance of org.apache.cxf.Bus.
Example: bus=#busName
cxfBinding
No
New in 2.0. Use # notation to reference a CXF binding object from the registry. The
referenced object must be an instance of org.apache.camel.component.cxf.CxfBinding
(use an instance of org.apache.camel.component.cxf.DefaultCxfBinding).
Example: cxfBinding=#bindingName
headerFilterStrategy
No
New in 2.0. Use # notation to reference a header filter strategy object from the registry. The
referenced object must be an instance of org.apache.camel.spi.HeaderFilterStrategy
(use an instance of org.apache.camel.component.cxf.CxfHeaderFilterStrategy).
Example: headerFilterStrategy=#strategyName
New in 2.3. This option enables CXF Logging Feature which writes inbound and outbound
SOAP messages to log.
loggingFeatureEnabled
No
Default: false
Example: loggingFeatureEnabled=true
New in 2.4, this option will set the default operationName that will be used by the
CxfProducer which invokes the remote service.
defaultOperationName
No
Default: null
Example: defaultOperationName=greetMe
New in 2.4. This option will set the default operationNamespace that will be used by the
CxfProducer which invokes the remote service.
defaultOperationNameSpace
No
Default: null
Example: defaultOperationNamespace=http://apache.org/hello_world_soap_http
synchronous
No
New in 2.5. This option will let cxf endpoint decide to use sync or async API to do the
underlying work. The default value is false which means camel-cxf endpoint will try to use
async API by default.
Default: false
Example: synchronous=true
New in 2.5. This option can override the endpointUrl that published from the WSDL which
can be accessed with service address url plus ?wsdl.
publishedEndpointUrl
No
Default: null
Example: publshedEndpointUrl=http://example.com/service
The serviceName and portName are QNames, so if you provide them be sure
to prefix them with their {namespace} as shown in the examples above.
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
532
NOTE From CAMEL 1.5.1 , the serviceClass for a CXF producer (that is,
the to endpoint) should be a Java interface.
The descriptions of the dataformats
DataFormat
Description
POJO
POJOs (Plain old Java objects) are the Java parameters to the method being invoked on the target server. Both Protocol
and Logical JAX-WS handlers are supported.
PAYLOAD
PAYLOAD is the message payload (the contents of the soap:body) after message configuration in the CXF endpoint is
applied. Only Protocol JAX-WS handler is supported. Logical JAX-WS handler is not supported.
MESSAGE
MESSAGE is the raw message that is received from the transport layer. JAX-WS handler is not supported.
You can determine the data format mode of an exchange by retrieving the
exchange property, CamelCXFDataFormat. The exchange key constant is
defined in
org.apache.camel.component.cxf.CxfConstants.DATA_FORMAT_PROPERTY.
How to enable CXF's LoggingOutInterceptor in MESSAGE mode
CXF's LoggingOutInterceptor outputs outbound message that goes on the
wire to logging system (Java Util Logging). Since the
LoggingOutInterceptor is in PRE_STREAM phase (but PRE_STREAM phase is
removed in MESSAGE mode), you have to configure LoggingOutInterceptor
to be run during the WRITE phase. The following is an example.
<bean id="loggingOutInterceptor"
class="org.apache.cxf.interceptor.LoggingOutInterceptor">
<!-- it really should have been user-prestream but CXF does have such phase!
-->
<constructor-arg value="write"/>
</bean>
<cxf:cxfEndpoint id="serviceEndpoint" address="http://localhost:9002/helloworld"
serviceClass="org.apache.camel.component.cxf.HelloService">
<cxf:outInterceptors>
<ref bean="loggingOutInterceptor"/>
</cxf:outInterceptors>
<cxf:properties>
<entry key="dataFormat" value="MESSAGE"/>
</cxf:properties>
</cxf:cxfEndpoint>
Description of relayHeaders option
There are in-band and out-of-band on-the-wire headers from the perspective
of a JAXWS WSDL-first developer.
533
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
The in-band headers are headers that are explicitly defined as part of the
WSDL binding contract for an endpoint such as SOAP headers.
The out-of-band headers are headers that are serialized over the wire, but
are not explicitly part of the WSDL binding contract.
Headers relaying/filtering is bi-directional.
When a route has a CXF endpoint and the developer needs to have on-thewire headers, such as SOAP headers, be relayed along the route to be
consumed say by another JAXWS endpoint, then relayHeaders should be set
to true, which is the default value.
Available in Release 1.6.1 and after (only in POJO mode)
The relayHeaders=true express an intent to relay the headers. The actual
decision on whether a given header is relayed is delegated to a pluggable
instance that implements the MessageHeadersRelay interface. A concrete
implementation of MessageHeadersRelay will be consulted to decide if a
header needs to be relayed or not. There is already an implementation of
SoapMessageHeadersRelay which binds itself to well-known SOAP name
spaces. Currently only out-of-band headers are filtered, and in-band headers
will always be relayed when relayHeaders=true. If there is a header on the
wire, whose name space is unknown to the runtime, then a fall back
DefaultMessageHeadersRelay will be used, which simply allows all headers
to be relayed.
The relayHeaders=false setting asserts that all headers in-band and outof-band will be dropped.
You can plugin your own MessageHeadersRelay implementations
overriding or adding additional ones to the list of relays. In order to override
a preloaded relay instance just make sure that your MessageHeadersRelay
implementation services the same name spaces as the one you looking to
override. Also note, that the overriding relay has to service all of the name
spaces as the one you looking to override, or else a runtime exception on
route start up will be thrown as this would introduce an ambiguity in name
spaces to relay instance mappings.
<cxf:cxfEndpoint ...>
<cxf:properties>
<entry key="org.apache.camel.cxf.message.headers.relays">
<list>
<ref bean="customHeadersRelay"/>
</list>
</entry>
</cxf:properties>
</cxf:cxfEndpoint>
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
534
<bean id="customHeadersRelay"
class="org.apache.camel.component.cxf.soap.headers.CustomHeadersRelay"/>
Take a look at the tests that show how you'd be able to relay/drop headers
here:
https://svn.apache.org/repos/asf/camel/branches/camel-1.x/components/
camel-cxf/src/test/java/org/apache/camel/component/cxf/soap/headers/
CxfMessageHeadersRelayTest.java
Changes since Release 2.0
• POJO and PAYLOAD modes are supported. In POJO mode, only out-ofband message headers are available for filtering as the in-band
headers have been processed and removed from header list by CXF.
The in-band headers are incorporated into the MessageContentList
in POJO mode. The camel-cxf component does make any attempt to
remove the in-band headers from the MessageContentList as it
does in 1.6.1. If filtering of in-band headers is required, please use
PAYLOAD mode or plug in a (pretty straightforward) CXF interceptor/
JAXWS Handler to the CXF endpoint.
• The Message Header Relay mechanism has been merged into
CxfHeaderFilterStrategy. The relayHeaders option, its semantics,
and default value remain the same, but it is a property of
CxfHeaderFilterStrategy.
Here is an example of configuring it.
<bean id="dropAllMessageHeadersStrategy"
class="org.apache.camel.component.cxf.CxfHeaderFilterStrategy">
<!-- Set relayHeaders to false to drop all SOAP headers -->
<property name="relayHeaders" value="false"/>
</bean>
Then, your endpoint can reference the CxfHeaderFilterStrategy.
<route>
<from
uri="cxf:bean:routerNoRelayEndpoint?headerFilterStrategy=#dropAllMessageHeadersStrategy"/>
<to
uri="cxf:bean:serviceNoRelayEndpoint?headerFilterStrategy=#dropAllMessageHeadersStrategy"/>
</route>
• The MessageHeadersRelay interface has changed slightly and has
been renamed to MessageHeaderFilter. It is a property of
535
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
CxfHeaderFilterStrategy. Here is an example of configuring user
defined Message Header Filters:
<bean id="customMessageFilterStrategy"
class="org.apache.camel.component.cxf.CxfHeaderFilterStrategy">
<property name="messageHeaderFilters">
<list>
<!-- SoapMessageHeaderFilter is the built in filter.
removed by omitting it. -->
<bean
class="org.apache.camel.component.cxf.SoapMessageHeaderFilter"/>
It can be
<!-- Add custom filter here -->
<bean
class="org.apache.camel.component.cxf.soap.headers.CustomHeaderFilter"/>
</list>
</property>
</bean>
• Other than relayHeaders, there are new properties that can be
configured in CxfHeaderFilterStrategy.
Name
Required
relayHeaders
No
relayAllMessageHeaders
No
Description
All message headers will be processed by Message Header Filters
Type: boolean
Default: true (1.6.1 behavior)
All message headers will be propagated (without processing by Message
Header Filters)
Type: boolean
Default: false (1.6.1 behavior)
allowFilterNamespaceClash
No
If two filters overlap in activation namespace, the property control how it
should be handled. If the value is true, last one wins. If the value is false, it
will throw an exception
Type: boolean
Default: false (1.6.1 behavior)
Configure the CXF endpoints with Spring
You can configure the CXF endpoint with the Spring configuration file
shown below, and you can also embed the endpoint into the
camelContext tags. When you are invoking the service endpoint, you
can set the operationName and operationNameSpace headers to
explicitly state which operation you are calling.
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:cxf="http://activemq.apache.org/camel/schema/cxfEndpoint"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-2.0.xsd
http://activemq.apache.org/camel/schema/cxfEndpoint
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
536
http://activemq.apache.org/camel/schema/cxf/camel-cxf-1.6.0.xsd
http://activemq.apache.org/camel/schema/spring
http://activemq.apache.org/camel/schema/spring/camel-spring.xsd
">
<cxf:cxfEndpoint id="routerEndpoint" address="http://localhost:9003/
CamelContext/RouterPort"
serviceClass="org.apache.hello_world_soap_http.GreeterImpl"/>
<cxf:cxfEndpoint id="serviceEndpoint" address="http://localhost:9000/
SoapContext/SoapPort"
wsdlURL="testutils/hello_world.wsdl"
serviceClass="org.apache.hello_world_soap_http.Greeter"
endpointName="s:SoapPort"
serviceName="s:SOAPService"
xmlns:s="http://apache.org/hello_world_soap_http" />
<camelContext id="camel" xmlns="http://activemq.apache.org/camel/schema/
spring">
<route>
<from uri="cxf:bean:routerEndpoint" />
<to uri="cxf:bean:serviceEndpoint" />
</route>
</camelContext>
</beans>
NOTE In Camel 2.x we change to use {{http:Â//camel.apache.org/
schema/cxf}} as the CXF endpoint's target namespace.
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:cxf="http://camel.apache.org/schema/cxf"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-2.0.xsd
http://camel.apache.org/schema/cxf http://camel.apache.org/schema/
cxf/camel-cxf.xsd
http://camel.apache.org/schema/spring http://camel.apache.org/schema/
spring/camel-spring.xsd
">
...
Be sure to include the JAX-WS schemaLocation attribute specified on
the root beans element. This allows CXF to validate the file and is
required. Also note the namespace declarations at the end of the
<cxf:cxfEndpoint/> tag--these are required because the combined
{namespace}localName syntax is presently not supported for this
tag's attribute values.
The cxf:cxfEndpoint element supports many additional
attributes:
537
Name
Value
PortName
The endpoint name this service is implementing, it maps to the wsdl:port@name. In the format of ns:PORT_NAME
where ns is a namespace prefix valid at this scope.
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
serviceName
The service name this service is implementing, it maps to the wsdl:service@name. In the format of
ns:SERVICE_NAME where ns is a namespace prefix valid at this scope.
wsdlURL
The location of the WSDL. Can be on the classpath, file system, or be hosted remotely.
bindingId
The bindingId for the service model to use.
address
The service publish address.
bus
The bus name that will be used in the JAX-WS endpoint.
serviceClass
The class name of the SEI (Service Endpoint Interface) class which could have JSR181 annotation or not.
It also supports many child elements:
Name
Value
cxf:inInterceptors
The incoming interceptors for this endpoint. A list of <bean> or <ref>.
cxf:inFaultInterceptors
The incoming fault interceptors for this endpoint. A list of <bean> or <ref>.
cxf:outInterceptors
The outgoing interceptors for this endpoint. A list of <bean> or <ref>.
cxf:outFaultInterceptors
The outgoing fault interceptors for this endpoint. A list of <bean> or <ref>.
cxf:properties
A properties map which should be supplied to the JAX-WS endpoint. See below.
cxf:handlers
A JAX-WS handler list which should be supplied to the JAX-WS endpoint. See below.
cxf:dataBinding
You can specify the which DataBinding will be use in the endpoint. This can be supplied using the
Spring <bean class="MyDataBinding"/> syntax.
cxf:binding
You can specify the BindingFactory for this endpoint to use. This can be supplied using the
Spring <bean class="MyBindingFactory"/> syntax.
cxf:features
The features that hold the interceptors for this endpoint. A list of {{<bean>}}s or {{<ref>}}s
cxf:schemaLocations
The schema locations for endpoint to use. A list of {{<schemaLocation>}}s
cxf:serviceFactory
The service factory for this endpoint to use. This can be supplied using the Spring <bean
class="MyServiceFactory"/> syntax
You can find more advanced examples which show how to provide
interceptors , properties and handlers here:
http://cwiki.apache.org/CXF20DOC/jax-ws-configuration.html
NOTE
You can use cxf:properties to set the camel-cxf endpoint's dataFormat and
setDefaultBus properties from spring configuration file.
<cxf:cxfEndpoint id="testEndpoint" address="http://localhost:9000/router"
serviceClass="org.apache.camel.component.cxf.HelloService"
endpointName="s:PortName"
serviceName="s:ServiceName"
xmlns:s="http://www.example.com/test">
<cxf:properties>
<entry key="dataFormat" value="MESSAGE"/>
<entry key="setDefaultBus" value="true"/>
</cxf:properties>
</cxf:cxfEndpoint>
How to make the camel-cxf component use log4j instead of
java.util.logging
CXF's default logger is java.util.logging. If you want to change it to log4j,
proceed as follows. Create a file, in the classpath, named META-INF/cxf/
org.apache.cxf.logger. This file should contain the fully-qualified name of
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
538
the class, org.apache.cxf.common.logging.Log4jLogger, with no
comments, on a single line.
How to let camel-cxf response message with xml start document
If you are using some soap client such as PHP, you will get this kind of error,
because CXF doesn't add the XML start document "<?xml version="1.0"
encoding="utf-8"?>"
Error:sendSms: SoapFault exception: [Client] looks like we got no XML document in
[...]
To resolved this issue, you just need to tell StaxOutInterceptor to write the
XML start document for you.
public class WriteXmlDeclarationInterceptor extends
AbstractPhaseInterceptor<SoapMessage> {
public WriteXmlDeclarationInterceptor() {
super(Phase.PRE_STREAM);
addBefore(StaxOutInterceptor.class.getName());
}
public void handleMessage(SoapMessage message) throws Fault {
message.put("org.apache.cxf.stax.force-start-document", Boolean.TRUE);
}
}
You can add a customer interceptor like this and configure it into you camelcxf endpont
<cxf:cxfEndpoint id="routerEndpoint" address="http://localhost:9003/CamelContext/
RouterPort"
serviceClass="org.apache.hello_world_soap_http.GreeterImpl">
<cxf:outInterceptors>
<!-- This interceptor will force the CXF server send the XML start document
to client -->
<bean class="org.apache.camel.component.cxf.WriteXmlDeclarationInterceptor"/>
</cxf:outInterceptors>
<cxf:properties>
<!-- Set the publishedEndpointUrl which could override the service address
from generated WSDL as you want -->
<entry key="publishedEndpointUrl" value="http://www.simple.com/services/
test" />
</cxf:properties>
</cxf:cxfEndpoint>
Or adding a message header for it like this if you are using Camel 2.4.
539
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
// set up the response context which force start document
Map<String, Object> map = new HashMap<String, Object>();
map.put("org.apache.cxf.stax.force-start-document", Boolean.TRUE);
exchange.getOut().setHeader(Client.RESPONSE_CONTEXT, map);
How to consume a message from a camel-cxf endpoint in POJO data
format
The camel-cxf endpoint consumer POJO data format is based on the cxf
invoker, so the message header has a property with the name of
CxfConstants.OPERATION_NAME and the message body is a list of the SEI
method parameters.
public class PersonProcessor implements Processor {
private static final transient Logger LOG =
LoggerFactory.getLogger(PersonProcessor.class);
@SuppressWarnings("unchecked")
public void process(Exchange exchange) throws Exception {
LOG.info("processing exchange in camel");
BindingOperationInfo boi =
(BindingOperationInfo)exchange.getProperty(BindingOperationInfo.class.toString());
if (boi != null) {
LOG.info("boi.isUnwrapped" + boi.isUnwrapped());
}
// Get the parameters list which element is the holder.
MessageContentsList msgList = (MessageContentsList)exchange.getIn().getBody();
Holder<String> personId = (Holder<String>)msgList.get(0);
Holder<String> ssn = (Holder<String>)msgList.get(1);
Holder<String> name = (Holder<String>)msgList.get(2);
if (personId.value == null || personId.value.length() == 0) {
LOG.info("person id 123, so throwing exception");
// Try to throw out the soap fault message
org.apache.camel.wsdl_first.types.UnknownPersonFault personFault =
new org.apache.camel.wsdl_first.types.UnknownPersonFault();
personFault.setPersonId("");
org.apache.camel.wsdl_first.UnknownPersonFault fault =
new org.apache.camel.wsdl_first.UnknownPersonFault("Get the null
value of person name", personFault);
// Since camel has its own exception handler framework, we can't throw
the exception to trigger it
// We just set the fault message in the exchange for camel-cxf component
handling and return
exchange.getOut().setFault(true);
exchange.getOut().setBody(fault);
return;
}
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
540
name.value = "Bonjour";
ssn.value = "123";
LOG.info("setting Bonjour as the response");
// Set the response message, first element is the return value of the
operation,
// the others are the holders of method parameters
exchange.getOut().setBody(new Object[] {null, personId, ssn, name});
}
}
How to prepare the message for the camel-cxf endpoint in POJO
data format
The camel-cxf endpoint producer is based on the cxf client API. First you
need to specify the operation name in the message header, then add the
method parameters to a list, and initialize the message with this parameter
list. The response message's body is a messageContentsList, you can get the
result from that list.
NOTE After Camel 1.5 , we change the message body from object array to
message content list. If you still want to get the object array from the
message body, you can get the body using
message.getbody(Object[].class), as follows:
Exchange senderExchange = new DefaultExchange(context, ExchangePattern.InOut);
final List<String> params = new ArrayList<String>();
// Prepare the request message for the camel-cxf procedure
params.add(TEST_MESSAGE);
senderExchange.getIn().setBody(params);
senderExchange.getIn().setHeader(CxfConstants.OPERATION_NAME, ECHO_OPERATION);
Exchange exchange = template.send("direct:EndpointA", senderExchange);
org.apache.camel.Message out = exchange.getOut();
// The response message's body is an MessageContentsList which first element is the
return value of the operation,
// If there are some holder parameters, the holder parameter will be filled in the
reset of List.
// The result will be extract from the MessageContentsList with the String class type
MessageContentsList result = (MessageContentsList)out.getBody();
LOG.info("Received output text: " + result.get(0));
Map<String, Object> responseContext =
CastUtils.cast((Map)out.getHeader(Client.RESPONSE_CONTEXT));
assertNotNull(responseContext);
assertEquals("We should get the response context here", "UTF-8",
responseContext.get(org.apache.cxf.message.Message.ENCODING));
assertEquals("Reply body on Camel is wrong", "echo " + TEST_MESSAGE, result.get(0));
541
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
How to deal with the message for a camel-cxf endpoint in PAYLOAD
data format
PAYLOAD means that you process the payload message from the SOAP
envelope. You can use the Header.HEADER_LIST as the key to set or get the
SOAP headers and use the List<Element> to set or get SOAP body elements.
Camel 1.x branch, you can get the List<Element> and header from the CXF
Message, but if you want to set the response message, you need to create
the CXF message using the CXF API.
protected RouteBuilder createRouteBuilder() {
return new RouteBuilder() {
public void configure() {
from(SIMPLE_ENDPOINT_URI +
"&dataFormat=PAYLOAD").to("log:info").process(new Processor() {
public void process(final Exchange exchange) throws Exception {
Message inMessage = exchange.getIn();
if (inMessage instanceof CxfMessage) {
CxfMessage cxfInMessage = (CxfMessage) inMessage;
CxfMessage cxfOutMessage = (CxfMessage) exchange.getOut();
List<Element> inElements =
cxfInMessage.getMessage().get(List.class);
List<Element> outElements = new ArrayList<Element>();
XmlConverter converter = new XmlConverter();
String documentString = ECHO_RESPONSE;
if (inElements.get(0).getLocalName().equals("echoBoolean")) {
documentString = ECHO_BOOLEAN_RESPONSE;
}
org.apache.cxf.message.Exchange ex =
((CxfExchange)exchange).getExchange();
Endpoint ep = ex.get(Endpoint.class);
org.apache.cxf.message.Message response =
ep.getBinding().createMessage();
Document outDocument =
converter.toDOMDocument(documentString);
outElements.add(outDocument.getDocumentElement());
response.put(List.class, outElements);
cxfOutMessage.setMessage(response);
}
}
});
}
};
}
Change in 2.0, There is no more CxfMessage, we just use the common
Camel DefaultMessageImpl under layer. Message.getBody() will return an
org.apache.camel.component.cxf.CxfPayload object, which has getters
for SOAP message headers and Body elements. This change enables
decoupling the native CXF message from the Camel message.
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
542
protected RouteBuilder createRouteBuilder() {
return new RouteBuilder() {
public void configure() {
from(SIMPLE_ENDPOINT_URI +
"&dataFormat=PAYLOAD").to("log:info").process(new Processor() {
@SuppressWarnings("unchecked")
public void process(final Exchange exchange) throws Exception {
CxfPayload<SoapHeader> requestPayload =
exchange.getIn().getBody(CxfPayload.class);
List<Element> inElements = requestPayload.getBody();
List<Element> outElements = new ArrayList<Element>();
// You can use a customer toStringConverter to turn a CxfPayLoad
message into String as you want
String request = exchange.getIn().getBody(String.class);
XmlConverter converter = new XmlConverter();
String documentString = ECHO_RESPONSE;
if (inElements.get(0).getLocalName().equals("echoBoolean")) {
documentString = ECHO_BOOLEAN_RESPONSE;
assertEquals("Get a wrong request", ECHO_BOOLEAN_REQUEST,
request);
} else {
assertEquals("Get a wrong request", ECHO_REQUEST, request);
}
Document outDocument = converter.toDOMDocument(documentString);
outElements.add(outDocument.getDocumentElement());
// set the payload header with null
CxfPayload<SoapHeader> responsePayload = new
CxfPayload<SoapHeader>(null, outElements);
exchange.getOut().setBody(responsePayload);
}
});
}
};
}
How to get and set SOAP headers in POJO mode
POJO means that the data format is a "list of Java objects" when the Camelcxf endpoint produces or consumes Camel exchanges. Even though Camel
expose message body as POJOs in this mode, Camel-cxf still provides access
to read and write SOAP headers. However, since CXF interceptors remove inband SOAP headers from Header list after they have been processed, only
out-of-band SOAP headers are available to Camel-cxf in POJO mode.
The following example illustrate how to get/set SOAP headers. Suppose we
have a route that forwards from one Camel-cxf endpoint to another. That is,
SOAP Client -> Camel -> CXF service. We can attach two processors to
obtain/insert SOAP headers at (1) before request goes out to the CXF service
and (2) before response comes back to the SOAP Client. Processor (1) and (2)
543
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
in this example are InsertRequestOutHeaderProcessor and
InsertResponseOutHeaderProcessor. Our route looks like this:
<route>
<from uri="cxf:bean:routerRelayEndpointWithInsertion"/>
<process ref="InsertRequestOutHeaderProcessor" />
<to uri="cxf:bean:serviceRelayEndpointWithInsertion"/>
<process ref="InsertResponseOutHeaderProcessor" />
</route>
In 2.x SOAP headers are propagated to and from Camel Message headers.
The Camel message header name is "org.apache.cxf.headers.Header.list"
which is a constant defined in CXF
(org.apache.cxf.headers.Header.HEADER_LIST). The header value is a List of
CXF SoapHeader objects (org.apache.cxf.binding.soap.SoapHeader). The
following snippet is the InsertResponseOutHeaderProcessor (that insert a
new SOAP header in the response message). The way to access SOAP
headers in both InsertResponseOutHeaderProcessor and
InsertRequestOutHeaderProcessor are actually the same. The only difference
between the two processors is setting the direction of the inserted SOAP
header.
public static class InsertResponseOutHeaderProcessor implements Processor {
@SuppressWarnings("unchecked")
public void process(Exchange exchange) throws Exception {
List<SoapHeader> soapHeaders =
(List)exchange.getIn().getHeader(Header.HEADER_LIST);
// Insert a new header
String xml = "<?xml version=\"1.0\" encoding=\"utf-8\"?><outofbandHeader "
+ "xmlns=\"http://cxf.apache.org/outofband/Header\"
hdrAttribute=\"testHdrAttribute\" "
+ "xmlns:soap=\"http://schemas.xmlsoap.org/soap/envelope/\"
soap:mustUnderstand=\"1\">"
+
"<name>New_testOobHeader</name><value>New_testOobHeaderValue</value></outofbandHeader>";
SoapHeader newHeader = new SoapHeader(soapHeaders.get(0).getName(),
DOMUtils.readXml(new StringReader(xml)).getDocumentElement());
// make sure direction is OUT since it is a response message.
newHeader.setDirection(Direction.DIRECTION_OUT);
//newHeader.setMustUnderstand(false);
soapHeaders.add(newHeader);
}
}
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
544
In 1.x SOAP headers are not propagated to and from Camel Message
headers. Users have to go deeper into CXF APIs to access SOAP headers.
Also, accessing the SOAP headers in a request message is slight different
than in a response message. The InsertRequestOutHeaderProcessor and
InsertResponseOutHeaderProcessor are as follow.
public static class InsertRequestOutHeaderProcessor implements Processor {
public void process(Exchange exchange) throws Exception {
CxfMessage message = exchange.getIn().getBody(CxfMessage.class);
Message cxf = message.getMessage();
List<SoapHeader> soapHeaders = (List)cxf.get(Header.HEADER_LIST);
// Insert a new header
String xml = "<?xml version=\"1.0\" encoding=\"utf-8\"?><outofbandHeader "
+ "xmlns=\"http://cxf.apache.org/outofband/Header\"
hdrAttribute=\"testHdrAttribute\" "
+ "xmlns:soap=\"http://schemas.xmlsoap.org/soap/envelope/\"
soap:mustUnderstand=\"1\">"
+
"<name>New_testOobHeader</name><value>New_testOobHeaderValue</value></outofbandHeader>";
SoapHeader newHeader = new SoapHeader(soapHeaders.get(0).getName(),
DOMUtils.readXml(new
StringReader(xml)).getDocumentElement());
// make sure direction is IN since it is a request message.
newHeader.setDirection(Direction.DIRECTION_IN);
//newHeader.setMustUnderstand(false);
soapHeaders.add(newHeader);
}
}
public static class InsertResponseOutHeaderProcessor implements Processor {
public void process(Exchange exchange) throws Exception {
CxfMessage message = exchange.getIn().getBody(CxfMessage.class);
Map responseContext = (Map)message.getMessage().get(Client.RESPONSE_CONTEXT);
List<SoapHeader> soapHeaders = (List)responseContext.get(Header.HEADER_LIST);
// Insert a new header
String xml = "<?xml version=\"1.0\" encoding=\"utf-8\"?><outofbandHeader "
+ "xmlns=\"http://cxf.apache.org/outofband/Header\"
hdrAttribute=\"testHdrAttribute\" "
+ "xmlns:soap=\"http://schemas.xmlsoap.org/soap/envelope/\"
soap:mustUnderstand=\"1\">"
+
"<name>New_testOobHeader</name><value>New_testOobHeaderValue</value></outofbandHeader>";
SoapHeader newHeader = new SoapHeader(soapHeaders.get(0).getName(),
DOMUtils.readXml(new StringReader(xml)).getDocumentElement());
// make sure direction is OUT since it is a response message.
newHeader.setDirection(Direction.DIRECTION_OUT);
//newHeader.setMustUnderstand(false);
soapHeaders.add(newHeader);
545
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
}
}
How to get and set SOAP headers in PAYLOAD mode
We've already shown how to access SOAP message (CxfPayload object) in
PAYLOAD mode (See "How to deal with the message for a camel-cxf endpoint
in PAYLOAD data format").
In 2.x Once you obtain a CxfPayload object, you can invoke the
CxfPayload.getHeaders() method that returns a List of DOM Elements (SOAP
headers).
from(getRouterEndpointURI()).process(new Processor() {
@SuppressWarnings("unchecked")
public void process(Exchange exchange) throws Exception {
CxfPayload<SoapHeader> payload = exchange.getIn().getBody(CxfPayload.class);
List<Element> elements = payload.getBody();
assertNotNull("We should get the elements here", elements);
assertEquals("Get the wrong elements size", 1, elements.size());
assertEquals("Get the wrong namespace URI", "http://camel.apache.org/pizza/
types",
elements.get(0).getNamespaceURI());
List<SoapHeader> headers = payload.getHeaders();
assertNotNull("We should get the headers here", headers);
assertEquals("Get the wrong headers size", headers.size(), 1);
assertEquals("Get the wrong namespace URI",
((Element)(headers.get(0).getObject())).getNamespaceURI(),
"http://camel.apache.org/pizza/types");
}
})
.to(getServiceEndpointURI());
*In 1.x" You can get/set to the CXF Message by the key
"org.apache.cxf.headers.Header.list" which is a constant defined in CXF
(org.apache.cxf.headers.Header.HEADER_LIST).
from(routerEndpointURI).process(new Processor() {
@SuppressWarnings("unchecked")
public void process(Exchange exchange) throws Exception {
Message inMessage = exchange.getIn();
CxfMessage message = (CxfMessage) inMessage;
List<Element> elements = message.getMessage().get(List.class);
assertNotNull("We should get the payload elements here" , elements);
assertEquals("Get the wrong elements size" , elements.size(), 1);
assertEquals("Get the wrong namespace URI" ,
elements.get(0).getNamespaceURI(), "http://camel.apache.org/pizza/types");
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
546
List<SoapHeader> headers =
CastUtils.cast((List<?>)message.getMessage().get(Header.HEADER_LIST));
assertNotNull("We should get the headers here", headers);
assertEquals("Get the wrong headers size", headers.size(), 1);
assertEquals("Get the wrong namespace URI" ,
((Element)(headers.get(0).getObject())).getNamespaceURI(), "http://camel.apache.org/
pizza/types");
}
})
.to(serviceEndpointURI);
SOAP headers are not available in MESSAGE mode
SOAP headers are not available in MESSAGE mode as SOAP processing is
skipped.
How to throw a SOAP Fault from Camel
If you are using a camel-cxf endpoint to consume the SOAP request, you
may need to throw the SOAP Fault from the camel context.
Basically, you can use the throwFault DSL to do that; it works for POJO,
PAYLOAD and MESSAGE data format.
You can define the soap fault like this
SOAP_FAULT = new SoapFault(EXCEPTION_MESSAGE, SoapFault.FAULT_CODE_CLIENT);
Element detail = SOAP_FAULT.getOrCreateDetail();
Document doc = detail.getOwnerDocument();
Text tn = doc.createTextNode(DETAIL_TEXT);
detail.appendChild(tn);
Then throw it as you like
from(routerEndpointURI).setFaultBody(constant(SOAP_FAULT));
If your CXF endpoint is working in the MESSAGE data format, you could set the
the SOAP Fault message in the message body and set the response code in
the message header.
from(routerEndpointURI).process(new Processor() {
public void process(Exchange exchange) throws Exception {
Message out = exchange.getOut();
547
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
// Set the message body with the
out.setBody(this.getClass().getResourceAsStream("SoapFaultMessage.xml"));
// Set the response code here
out.setHeader(org.apache.cxf.message.Message.RESPONSE_CODE, new Integer(500));
}
});
NOTE the response code setting only works in Camel's version >= 1.5.1
Same for using POJO data format. You can set the SOAPFault on the out
body and also indicate it's a fault by calling Message.setFault(true):
from("direct:start").onException(SoapFault.class).maximumRedeliveries(0).handled(true)
.process(new Processor() {
public void process(Exchange exchange) throws Exception {
SoapFault fault = exchange
.getProperty(Exchange.EXCEPTION_CAUGHT, SoapFault.class);
exchange.getOut().setFault(true);
exchange.getOut().setBody(fault);
}
}).end().to(SERVICE_URI);
How to propagate a camel-cxf endpoint's request and response
context
cxf client API provides a way to invoke the operation with request and
response context. If you are using a camel-cxf endpoint producer to invoke
the outside web service, you can set the request context and get response
context with the following code:
CxfExchange exchange = (CxfExchange)template.send(getJaxwsEndpointUri(), new
Processor() {
public void process(final Exchange exchange) {
final List<String> params = new ArrayList<String>();
params.add(TEST_MESSAGE);
// Set the request context to the inMessage
Map<String, Object> requestContext = new HashMap<String, Object>();
requestContext.put(BindingProvider.ENDPOINT_ADDRESS_PROPERTY,
JAXWS_SERVER_ADDRESS);
exchange.getIn().setBody(params);
exchange.getIn().setHeader(Client.REQUEST_CONTEXT , requestContext);
exchange.getIn().setHeader(CxfConstants.OPERATION_NAME,
GREET_ME_OPERATION);
}
});
org.apache.camel.Message out = exchange.getOut();
// The output is an object array, the first element of the array is the
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
548
return value
Object\[\] output = out.getBody(Object\[\].class);
LOG.info("Received output text: " + output\[0\]);
// Get the response context form outMessage
Map<String, Object> responseContext =
CastUtils.cast((Map)out.getHeader(Client.RESPONSE_CONTEXT));
assertNotNull(responseContext);
assertEquals("Get the wrong wsdl opertion name", "{http://apache.org/
hello_world_soap_http}greetMe",
responseContext.get("javax.xml.ws.wsdl.operation").toString());
Attachment Support
POJO Mode: Both SOAP with Attachment and MTOM are supported (see
example in Payload Mode for enabling MTOM). However, SOAP with
Attachment is not tested. Since attachments are marshalled and
unmarshalled into POJOs, users typically do not need to deal with the
attachment themself. Attachments are propagated to Camel message's
attachments since 2.1. So, it is possible to retreive attachments by Camel
Message API
DataHandler Message.getAttachment(String id)
.
Payload Mode: MTOM is supported since 2.1. Attachments can be
retrieved by Camel Message APIs mentioned above. SOAP with Attachment
(SwA) is supported and attachments can be retrieved since 2.5. SwA is the
default (same as setting the CXF endpoint property "mtom_enabled" to
false).Â
To enable MTOM, set the CXF endpoint property "mtom_enabled" to true. (I
believe you can only do it with Spring.)
<cxf:cxfEndpoint id="routerEndpoint" address="http://localhost:9091/jaxws-mtom/hello"
wsdlURL="mtom.wsdl"
serviceName="ns:HelloService"
endpointName="ns:HelloPort"
xmlns:ns="http://apache.org/camel/cxf/mtom_feature">
<cxf:properties>
<!-- enable mtom by setting this property to true -->
<entry key="mtom-enabled" value="true"/>
<!-- set the camel-cxf endpoint data fromat to PAYLOAD mode -->
<entry key="dataFormat" value="PAYLOAD"/>
</cxf:properties>
549
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
You can produce a Camel message with attachment to send to a CXF
endpoint in Payload mode.
Exchange exchange = context.createProducerTemplate().send("direct:testEndpoint", new
Processor() {
public void process(Exchange exchange) throws Exception {
exchange.setPattern(ExchangePattern.InOut);
List<Element> elements = new ArrayList<Element>();
elements.add(DOMUtils.readXml(new
StringReader(MtomTestHelper.REQ_MESSAGE)).getDocumentElement());
CxfPayload<SoapHeader> body = new CxfPayload<SoapHeader>(new
ArrayList<SoapHeader>(),
elements);
exchange.getIn().setBody(body);
exchange.getIn().addAttachment(MtomTestHelper.REQ_PHOTO_CID,
new DataHandler(new ByteArrayDataSource(MtomTestHelper.REQ_PHOTO_DATA,
"application/octet-stream")));
exchange.getIn().addAttachment(MtomTestHelper.REQ_IMAGE_CID,
new DataHandler(new ByteArrayDataSource(MtomTestHelper.requestJpeg,
"image/jpeg")));
}
});
// process response
CxfPayload<SoapHeader> out = exchange.getOut().getBody(CxfPayload.class);
Assert.assertEquals(1, out.getBody().size());
Map<String, String> ns = new HashMap<String, String>();
ns.put("ns", MtomTestHelper.SERVICE_TYPES_NS);
ns.put("xop", MtomTestHelper.XOP_NS);
XPathUtils xu = new XPathUtils(ns);
Element ele = (Element)xu.getValue("//ns:DetailResponse/ns:photo/xop:Include",
out.getBody().get(0),
XPathConstants.NODE);
String photoId = ele.getAttribute("href").substring(4); // skip "cid:"
ele = (Element)xu.getValue("//ns:DetailResponse/ns:image/xop:Include",
out.getBody().get(0),
XPathConstants.NODE);
String imageId = ele.getAttribute("href").substring(4); // skip "cid:"
DataHandler dr = exchange.getOut().getAttachment(photoId);
Assert.assertEquals("application/octet-stream", dr.getContentType());
MtomTestHelper.assertEquals(MtomTestHelper.RESP_PHOTO_DATA,
IOUtils.readBytesFromStream(dr.getInputStream()));
dr = exchange.getOut().getAttachment(imageId);
Assert.assertEquals("image/jpeg", dr.getContentType());
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
550
BufferedImage image = ImageIO.read(dr.getInputStream());
Assert.assertEquals(560, image.getWidth());
Assert.assertEquals(300, image.getHeight());
You can also consume a Camel message received from a CXF endpoint in
Payload mode.
public static class MyProcessor implements Processor {
@SuppressWarnings("unchecked")
public void process(Exchange exchange) throws Exception {
CxfPayload<SoapHeader> in = exchange.getIn().getBody(CxfPayload.class);
// verify request
Assert.assertEquals(1, in.getBody().size());
Map<String, String> ns = new HashMap<String, String>();
ns.put("ns", MtomTestHelper.SERVICE_TYPES_NS);
ns.put("xop", MtomTestHelper.XOP_NS);
XPathUtils xu = new XPathUtils(ns);
Element ele = (Element)xu.getValue("//ns:Detail/ns:photo/xop:Include",
in.getBody().get(0),
XPathConstants.NODE);
String photoId = ele.getAttribute("href").substring(4); // skip "cid:"
Assert.assertEquals(MtomTestHelper.REQ_PHOTO_CID, photoId);
ele = (Element)xu.getValue("//ns:Detail/ns:image/xop:Include",
in.getBody().get(0),
XPathConstants.NODE);
String imageId = ele.getAttribute("href").substring(4); // skip "cid:"
Assert.assertEquals(MtomTestHelper.REQ_IMAGE_CID, imageId);
DataHandler dr = exchange.getIn().getAttachment(photoId);
Assert.assertEquals("application/octet-stream", dr.getContentType());
MtomTestHelper.assertEquals(MtomTestHelper.REQ_PHOTO_DATA,
IOUtils.readBytesFromStream(dr.getInputStream()));
dr = exchange.getIn().getAttachment(imageId);
Assert.assertEquals("image/jpeg", dr.getContentType());
MtomTestHelper.assertEquals(MtomTestHelper.requestJpeg,
IOUtils.readBytesFromStream(dr.getInputStream()));
// create response
List<Element> elements = new ArrayList<Element>();
elements.add(DOMUtils.readXml(new
StringReader(MtomTestHelper.RESP_MESSAGE)).getDocumentElement());
CxfPayload<SoapHeader> body = new CxfPayload<SoapHeader>(new
ArrayList<SoapHeader>(),
elements);
551
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
exchange.getOut().setBody(body);
exchange.getOut().addAttachment(MtomTestHelper.RESP_PHOTO_CID,
new DataHandler(new ByteArrayDataSource(MtomTestHelper.RESP_PHOTO_DATA,
"application/octet-stream")));
exchange.getOut().addAttachment(MtomTestHelper.RESP_IMAGE_CID,
new DataHandler(new ByteArrayDataSource(MtomTestHelper.responseJpeg,
"image/jpeg")));
}
}
Message Mode: Attachments are not supported as it does not process the
message at all.
See Also
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
CXF BEAN COMPONENT (2.0 OR LATER)
The cxfbean: component allows other Camel endpoints to send exchange
and invoke Web service bean objects. (Currently, it only supports JAXRS,
JAXWS(new to camel2.1) annotated service bean.)
URI format
cxfbean:serviceBeanRef
Where serviceBeanRef is a registry key to look up the service bean object.
If serviceBeanRef references a List object, elements of the List are the
service bean objects accepted by the endpoint.
Options
Name
Description
Example
Required?
Defa
cxfBeanBinding
CXF bean binding specified by the # notation. The referenced
object must be an instance of
org.apache.camel.component.cxf.cxfbean.CxfBeanBinding.
cxfBinding=#bindingName
No
Default
bus
CXF bus reference specified by the # notation. The referenced
object must be an instance of org.apache.cxf.Bus.
bus=#busName
No
Default
Bus Fac
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
552
CxfBeanEndpoint is a ProcessorEndpoint so it has no consumers.
It works similarly to a Bean component.
headerFilterStrategy
Header filter strategy specified by the # notation. The
referenced object must be an instance of
org.apache.camel.spi.HeaderFilterStrategy.
headerFilterStrategy=#strategyName
No
CxfHead
setDefaultBus
Will set the default bus when CXF endpoint create a bus by
itself.
true, false
No
false
populateFromClass
Since 2.3, the wsdlLocation annotated in the POJO is ignored
(by default) unless this option is set to false. Prior to 2.3,
the wsdlLocation annotated in the POJO is always honored and
it is not possible to ignore.
true, false
No
true
providers
Since 2.5, setting the providers for the CXFRS endpoint.
providers=#providerRef1,#providerRef2
No
null
Headers
Name
Description
Type
Required?
Default
Value
In/
Out
Examples
CamelHttpCharacterEncoding
(before 2.0-m2:
CamelCxfBeanCharacterEncoding)
Character encoding
String
No
None
In
ISO-8859-1
CamelContentType (before 2.0-m2:
CamelCxfBeanContentType)
Content type
String
No
*/*
In
text/xml
CamelHttpBaseUri
(2.0-m3 and before:
CamelCxfBeanRequestBasePath)
The value of this
header will be set in
the CXF message as
the
Message.BASE_PATH
property. It is needed
by CXF JAX-RS
processing. Basically, it
is the scheme, host
and port portion of the
request URI.
String
Yes
The Endpoint
URI of the
source
endpoint in
the Camel
exchange
In
http://localhost:9000
CamelHttpPath (before 2.0-m2:
CamelCxfBeanRequestPath)
Request URI's path
String
Yes
None
In
consumer/123
CamelHttpMethod (before 2.0-m2:
CamelCxfBeanVerb)
RESTful request verb
String
Yes
None
In
GET, PUT, POST,
DELETE
CamelHttpResponseCode
HTTP response code
Integer
No
None
Out
200
A Working Sample
This sample shows how to create a route that starts a Jetty HTTP server. The
route sends requests to a CXF Bean and invokes a JAXRS annotated service.
First, create a route as follows. The from endpoint is a Jetty HTTP endpoint
that is listening on port 9000. Notice that the matchOnUriPrefix option must
be set to true because RESTful request URI will not match the endpoint's URI
http:Â//localhost:9000 exactly.
<route>
<from uri="jetty:http://localhost:9000?matchOnUriPrefix=true" />
553
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
Currently, CXF Bean component has (only) been tested with Jetty
HTTP component it can understand headers from Jetty HTTP
component without requiring conversion.
<to uri="cxfbean:customerServiceBean" />
</route>
The to endpoint is a CXF Bean with bean name customerServiceBean. The
name will be looked up from the registry. Next, we make sure our service
bean is available in Spring registry. We create a bean definition in the Spring
configuration. In this example, we create a List of service beans (of one
element). We could have created just a single bean without a List.
<util:list id="customerServiceBean">
<bean class="org.apache.camel.component.cxf.jaxrs.testbean.CustomerService" />
</util:list>
<bean class="org.apache.camel.wsdl_first.PersonImpl" id="jaxwsBean" />
That's it. Once the route is started, the web service is ready for business. A
HTTP client can make a request and receive response.
Error formatting macro: snippet: java.lang.IndexOutOfBoundsException:
Index: 20, Size: 20
CXFRS COMPONENT
The cxfrs: component provides integration with Apache CXF for connecting
to JAX-RS services hosted in CXF.
Maven users will need to add the following dependency to their pom.xml
for this component:
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-cxf</artifactId>
<version>x.x.x</version> <!-- use the same version as your Camel core version -->
</dependency>
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
554
When using CXF as a consumer, the CXF Bean Component allows
you to factor out how message payloads are received from their
processing as a RESTful or SOAP web service. This has the potential
of using a multitude of transports to consume web services. The
bean component's configuration is also simpler and provides the
fastest method to implement web services using Camel and CXF.
URI format
cxfrs://address?options
Where address represents the CXF endpoint's address
cxfrs:bean:rsEndpoint
Where rsEndpoint represents the spring bean's name which presents the
CXFRS client or server
For either style above, you can append options to the URI as follows:
cxfrs:bean:cxfEndpoint?resourceClass=org.apache.camel.rs.Example
Options
555
Name
Description
Example
Required?
default
value
resourceClasses
The resource classes which
you want to export as REST
service
resourceClasses
=org.apache.camel.rs.Example1,org.apache.camel.rs.Exchange2
No
None
httpClientAPI
new to Camel 2.1 If it is
true, the CxfRsProducer will
use the HttpClientAPI to
invoke the service
If it is false, the
CxfRsProducer will use the
ProxyClientAPI to invoke the
service
httpClientAPI=true
No
true
synchronous
New in 2.5, this option will
let CxfRsConsumer decide to
use sync or async API to do
the underlying work. The
default value is false which
means it will try to use async
API by default.
synchronous=true
No
false
throwExceptionOnFailure
New in 2.6, this option tells
the CxfRsProducer to inspect
return codes and will
generate an Exception if the
return code is larger than
207.
throwExceptionOnFailure=true
No
true
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
maxClientCacheSize
New in 2.6, you can set a IN
message header
CamelDestinationOverrideUrl
to dynamically override the
target destination Web
Service or REST Service
defined in your routes. The
implementation caches CXF
clients or ClientFactoryBean
in CxfProvider and
CxfRsProvider. This option
allows you to configure the
maximum size of the cache.
maxClientCacheSize=5
No
10
You can also configure the CXF REST endpoint through the spring
configuration. Since there are lots of difference between the CXF REST client
and CXF REST Server, we provides different configuration for them.
Please check out the schema file and CXF REST user guide for more
information.
How to configure the REST endpoint in Camel
In camel-cxf schema file, there are two elements for the REST endpoint
definition. cxf:rsServer for REST consumer, cxf:rsClient for REST producer.
You can find an camel REST service route configuration example here.
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:cxf="http://camel.apache.org/schema/cxf"
xmlns:jaxrs="http://cxf.apache.org/jaxrs"
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/
schema/beans/spring-beans.xsd
http://camel.apache.org/schema/cxf http://camel.apache.org/schema/cxf/
camel-cxf.xsd
http://cxf.apache.org/jaxrs http://cxf.apache.org/schemas/jaxrs.xsd
http://camel.apache.org/schema/spring http://camel.apache.org/schema/spring/
camel-spring.xsd
">
<!-- Defined the real JAXRS back end service -->
<jaxrs:server id="restService"
address="http://localhost:9002/rest"
staticSubresourceResolution="true">
<jaxrs:serviceBeans>
<ref bean="customerService"/>
</jaxrs:serviceBeans>
</jaxrs:server>
<!--
bean id="jsonProvider" class="org.apache.cxf.jaxrs.provider.JSONProvider"/-->
<bean id="customerService"
class="org.apache.camel.component.cxf.jaxrs.testbean.CustomerService" />
<!-- Defined the server endpoint to create the cxf-rs consumer -->
<cxf:rsServer id="rsServer" address="http://localhost:9000/route"
serviceClass="org.apache.camel.component.cxf.jaxrs.testbean.CustomerService" />
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
556
<!-- Defined the client endpoint to create the cxf-rs consumer -->
<cxf:rsClient id="rsClient" address="http://localhost:9002/rest"
serviceClass="org.apache.camel.component.cxf.jaxrs.testbean.CustomerService"/>
<!-- The camel route context -->
<camelContext id="camel" xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="cxfrs://bean://rsServer"/>
<!-- We can remove this configure as the CXFRS producer is using the HttpAPI
by default -->
<setHeader headerName="CamelCxfRsUsingHttpAPI">
<constant>True</constant>
</setHeader>
<to uri="cxfrs://bean://rsClient"/>
</route>
</camelContext>
</beans>
How to consumer the REST request in Camel
CXF JAXRS front end implements the JAXRS(JSR311) API, so we can export the
resources classes as a REST service. And we leverage the CXF Invoker API to
turn a REST request into a normal Java object method invocation.
Unlike the camel-restlet, you don't need to specify the URI template within
your restlet endpoint, CXF take care of the REST request URI to resource
class method mapping according to the JSR311 specification. All you need to
do in Camel is delegate this method request to a right processor or endpoint.
Here is an example
protected RouteBuilder createRouteBuilder() throws Exception {
return new RouteBuilder() {
public void configure() {
errorHandler(new NoErrorHandlerBuilder());
from(CXF_RS_ENDPOINT_URI).process(new Processor() {
public void process(Exchange exchange) throws Exception {
Message inMessage = exchange.getIn();
// Get the operation name from in message
String operationName =
inMessage.getHeader(CxfConstants.OPERATION_NAME, String.class);
if ("getCustomer".equals(operationName)) {
String httpMethod = inMessage.getHeader(Exchange.HTTP_METHOD,
String.class);
assertEquals("Get a wrong http method", "GET", httpMethod);
String path = inMessage.getHeader(Exchange.HTTP_PATH,
String.class);
// The parameter of the invocation is stored in the body of
557
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
in message
String id = (String) inMessage.getBody(String.class);
if ("/customerservice/customers/126".equals(path))
{
Customer customer = new Customer();
customer.setId(Long.parseLong(id));
customer.setName("Willem");
// We just put the response Object into the out message
body
exchange.getOut().setBody(customer);
} else {
if ("/customerservice/customers/456".equals(path)) {
Response r = Response.status(404).entity("Can't found
the customer with uri " + path).build();
throw new WebApplicationException(r);
} else {
throw new RuntimeCamelException("Can't found the
customer with uri " + path);
}
}
}
if ("updateCustomer".equals(operationName)) {
assertEquals("Get a wrong customer message header",
"header1;header2", inMessage.getHeader("test"));
String httpMethod = inMessage.getHeader(Exchange.HTTP_METHOD,
String.class);
assertEquals("Get a wrong http method", "PUT", httpMethod);
Customer customer = inMessage.getBody(Customer.class);
assertNotNull("The customer should not be null.", customer);
// Now you can do what you want on the customer object
assertEquals("Get a wrong customer name.", "Mary",
customer.getName());
// set the response back
exchange.getOut().setBody(Response.ok().build());
}
}
});
}
};
}
How to invoke the REST service through camel-cxfrs producer
CXF JAXRS front end implements a proxy based client API, with this API you
can invoke the remote REST service through a proxy.
camel-cxfrs producer is based on this proxy API.
So, you just need to specify the operation name in the message header and
prepare the parameter in the message body, camel-cxfrs producer will
generate right REST request for you.
Here is an example
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
558
Exchange exchange = template.send("direct://proxy", new Processor() {
public void process(Exchange exchange) throws Exception {
exchange.setPattern(ExchangePattern.InOut);
Message inMessage = exchange.getIn();
setupDestinationURL(inMessage);
// set the operation name
inMessage.setHeader(CxfConstants.OPERATION_NAME, "getCustomer");
// using the proxy client API
inMessage.setHeader(CxfConstants.CAMEL_CXF_RS_USING_HTTP_API, Boolean.FALSE);
// set the parameters , if you just have one parameter
// camel will put this object into an Object[] itself
inMessage.setBody("123");
}
});
// get the response message
Customer response = (Customer) exchange.getOut().getBody();
assertNotNull("The response should not be null ", response);
assertEquals("Get a wrong customer id ", String.valueOf(response.getId()), "123");
assertEquals("Get a wrong customer name", response.getName(), "John");
CXF JAXRS front end also provides a http centric client API, You can also
invoke this API from camel-cxfrs producer. You need to specify the
HTTP_PATH and Http method and let the the producer know to use the http
centric client by using the URI option httpClientAPI or set the message
header with CxfConstants.CAMEL_CXF_RS_USING_HTTP_API. You can turn the
response object to the type class that you specify with
CxfConstants.CAMEL_CXF_RS_RESPONSE_CLASS.
Exchange exchange = template.send("direct://http", new Processor() {
public void process(Exchange exchange) throws Exception {
exchange.setPattern(ExchangePattern.InOut);
Message inMessage = exchange.getIn();
setupDestinationURL(inMessage);
// using the http central client API
inMessage.setHeader(CxfConstants.CAMEL_CXF_RS_USING_HTTP_API, Boolean.TRUE);
// set the Http method
inMessage.setHeader(Exchange.HTTP_METHOD, "GET");
// set the relative path
inMessage.setHeader(Exchange.HTTP_PATH, "/customerservice/customers/
123");
// Specify the response class , cxfrs will use InputStream as the response
object type
inMessage.setHeader(CxfConstants.CAMEL_CXF_RS_RESPONSE_CLASS, Customer.class);
// since we use the Get method, so we don't need to set the message body
inMessage.setBody(null);
}
});
// get the response message
559
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
Customer response = (Customer) exchange.getOut().getBody();
assertNotNull("The response should not be null ", response);
assertEquals("Get a wrong customer id ", String.valueOf(response.getId()), "123");
assertEquals("Get a wrong customer name", response.getName(), "John");
From Camel 2.1, we also support to specify the query parameters from cxfrs
URI for the CXFRS http centric client.
Exchange exchange = template.send("cxfrs://http://localhost:9003/
testQuery?httpClientAPI=true&q1=12&q2=13"
To support the Dynamical routing, you can override the URI's query
parameters by using the CxfConstants.CAMEL_CXF_RS_QUERY_MAP header to
set the parameter map for it.To support the Dynamical routing, you can
override the URI's query parameters by using the
CxfConstants.CAMEL_CXF_RS_QUERY_MAP header to set the parameter map
for it.
Map<String, String> queryMap = new LinkedHashMap<String,
String>();
queryMap.put("q1", "new");
queryMap.put("q2", "world");
inMessage.setHeader(CxfConstants.CAMEL_CXF_RS_QUERY_MAP, queryMap);
DATASET COMPONENT
Testing of distributed and asynchronous processing is notoriously difficult.
The Mock, Test and DataSet endpoints work great with the Camel Testing
Framework to simplify your unit and integration testing using Enterprise
Integration Patterns and Camel's large range of Components together with
the powerful Bean Integration.
The DataSet component (available since 1.3.0) provides a mechanism to
easily perform load & soak testing of your system. It works by allowing you to
create DataSet instances both as a source of messages and as a way to
assert that the data set is received.
Camel will use the throughput logger when sending dataset's.
URI format
dataset:name[?options]
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
560
Where name is used to find the DataSet instance in the Registry
Camel ships with a support implementation of
org.apache.camel.component.dataset.DataSet, the
org.apache.camel.component.dataset.DataSetSupport class, that can be
used as a base for implementing your own DataSet. Camel also ships with a
default implementation, the
org.apache.camel.component.dataset.SimpleDataSet that can be used
for testing.
Options
Option
Default
Description
produceDelay
3
Allows a delay in ms to be specified, which causes producers to pause in order to simulate slow producers.
Uses a minimum of 3 ms delay unless you set this option to -1 to force no delay at all.
consumeDelay
0
Allows a delay in ms to be specified, which causes consumers to pause in order to simulate slow consumers.
preloadSize
0
Sets how many messages should be preloaded (sent) before the route completes its initialization.
initialDelay
1000
Camel 2.1: Time period in millis to wait before starting sending messages.
minRate
0
Wait until the DataSet contains at least this number of messages
You can append query options to the URI in the following format,
?option=value&option=value&...
Configuring DataSet
Camel will lookup in the Registry for a bean implementing the DataSet
interface. So you can register your own DataSet as:
<bean id="myDataSet" class="com.mycompany.MyDataSet">
<property name="size" value="100"/>
</bean>
Example
For example, to test that a set of messages are sent to a queue and then
consumed from the queue without losing any messages:
// send the dataset to a queue
from("dataset:foo").to("activemq:SomeQueue");
// now lets test that the messages are consumed correctly
from("activemq:SomeQueue").to("dataset:foo");
The above would look in the Registry to find the foo DataSet instance which
is used to create the messages.
561
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
Then you create a DataSet implementation, such as using the
SimpleDataSet as described below, configuring things like how big the data
set is and what the messages look like etc.
Properties on SimpleDataSet
Property
Type
Description
defaultBody
Object
Specifies the default message body. For SimpleDataSet it is a constant payload; though if you want to create
custom payloads per message, create your own derivation of DataSetSupport.
reportGroup
long
Specifies the number of messages to be received before reporting progress. Useful for showing progress of a
large load test.
size
long
Specifies how many messages to send/consume.
See Also
•
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
Spring Testing
DB4O COMPONENT
Available as of Camel 2.5
The db4o: component allows you to work with db4o NoSQL database. The
camel-db4o library is provided by the Camel Extra project which hosts all
*GPL related components for Camel.
Sending to the endpoint
Sending POJO object to the db4o endpoint adds and saves object into the
database. The body of the message is assumed to be a POJO that has to be
saved into the db40 database store.
Consuming from the endpoint
Consuming messages removes (or updates) POJO objects in the database.
This allows you to use a Db4o datastore as a logical queue; consumers take
messages from the queue and then delete them to logically remove them
from the queue.
If you do not wish to delete the object when it has been processed, you
can specify consumeDelete=false on the URI. This will result in the POJO
being processed each poll.
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
562
URI format
db4o:className[?options]
You can append query options to the URI in the following format,
?option=value&option=value&...
Options
Name
Default
Value
Description
consumeDelete
true
Option for Db4oConsumer only. Specifies whether or not the entity is deleted after it is consumed.
consumer.delay
500
Option for HibernateConsumer only. Delay in millis between each poll.
consumer.initialDelay
1000
Option for HibernateConsumer only. Millis before polling starts.
consumer.userFixedDelay
false
Option for HibernateConsumer only. Set to true to use fixed delay between polls, otherwise fixed
rate is used. See ScheduledExecutorService in JDK for details.
See Also
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
DIRECT COMPONENT
The direct: component provides direct, synchronous invocation of any
consumers when a producer sends a message exchange.
This endpoint can be used to connect existing routes in the same camel
context.
URI format
direct:someName[?options]
Where someName can be any string to uniquely identify the endpoint
Options
Name
563
Default
Value
Description
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
Asynchronous
The SEDA component provides asynchronous invocation of any
consumers when a producer sends a message exchange.
Connection to other camel contexts
The VM component provides connections between Camel contexts
as long they run in the same JVM.
allowMultipleConsumers
true
@deprecated If set to false, then when a second consumer is started on the endpoint, an
IllegalStateException is thrown. Will be removed in Camel 2.1: Direct endpoint does not
support multiple consumers.
You can append query options to the URI in the following format,
?option=value&option=value&...
Samples
In the route below we use the direct component to link the two routes
together:
from("activemq:queue:order.in")
.to("bean:orderServer?method=validate")
.to("direct:processOrder");
from("direct:processOrder")
.to("bean:orderService?method=process")
.to("activemq:queue:order.out");
And the sample using spring DSL:
<route>
<from uri="activemq:queue:order.in"/>
<to uri="bean:orderService?method=validate"/>
<to uri="direct:processOrder"/>
</route>
<route>
<from uri="direct:processOrder"/>
<to uri="bean:orderService?method=process"/>
<to uri="activemq:queue:order.out"/>
</route>
See also samples from the SEDA component, how they can be used together.
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
564
See Also
•
•
•
•
▪
▪
Configuring Camel
Component
Endpoint
Getting Started
SEDA
VM
DNS
Available as of Camel 2.7
This is an additional component for Camel to run DNS queries, using
DNSJava. The component is a thin layer on top of DNSJava.
The component offers the following operations:
▪ ip, to resolve a domain by its ip
▪ lookup, to lookup information about the domain
▪ dig, to run DNS queries
Maven users will need to add the following dependency to their pom.xml for
this component:
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-dns</artifactId>
<version>x.x.x</version>
<!-- use the same version as your Camel core version -->
</dependency>
URI format
The URI scheme for a DNS component is as follows
dns://operation
This component only supports producers.
Options
None.
Headers
Header
565
Type
Operations
Description
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
dns.domain
String
ip
The domain name. Mandatory.
dns.name
String
lookup
The name to lookup. Mandatory.
dns.type
▪
lookup, dig
The type of the lookup. Should match the values of org.xbill.dns.Type. Optional.
dns.class
▪
lookup, dig
he DNS class of the lookup. Should match the values of org.xbill.dns.DClass.
Optional.
dns.query
String
dig
The query itself. Mandatory.
dns.server
String
dig
The server in particular for the query. If none is given, the default one specified by the
OS will be used. Optional.
Examples
IP lookup
<route id="IPCheck">
<from uri="direct:start"/>
<to uri="dns:ip"/>
</route>
This looks up a domain's IP. For example, www.example.com resolves to
192.0.32.10.
The IP address to lookup must be provided in the header with key
"dns.domain".
DNS lookup
<route id="IPCheck">
<from uri="direct:start"/>
<to uri="dns:lookup"/>
</route>
This returns a set of DNS records associated with a domain.
The name to lookup must be provided in the header with key "dns.name".
DNS Dig
Dig is a Unix command-line utility to run DNS queries.
<route id="IPCheck">
<from uri="direct:start"/>
<to uri="dns:dig"/>
</route>
The query must be provided in the header with key "dns.query".
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
566
See Also
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
EJB COMPONENT
Available as of Camel 2.4
The ejb: component binds EJBs to Camel message exchanges.
Maven users will need to add the following dependency to their pom.xml
for this component:
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-ejb</artifactId>
<version>x.x.x</version>
<!-- use the same version as your Camel core version -->
</dependency>
URI format
ejb:ejbName[?options]
Where ejbName can be any string which is used to look up the EJB in the
Application Server JNDI Registry
Options
Name
Type
Default
Description
method
String
null
The method name that bean will be invoked. If not provided, Camel will try to pick the
method itself. In case of ambiguity an exception is thrown. See Bean Binding for more
details.
multiParameterArray
boolean
false
How to treat the parameters which are passed from the message body; if it is true, the In
message body should be an array of parameters.
You can append query options to the URI in the following format,
?option=value&option=value&...
The EJB component extends the Bean component in which most of the
details from the Bean component applies to this component as well.
567
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
Bean Binding
How bean methods to be invoked are chosen (if they are not specified
explicitly through the method parameter) and how parameter values are
constructed from the Message are all defined by the Bean Binding
mechanism which is used throughout all of the various Bean Integration
mechanisms in Camel.
Examples
In the following examples we use the Greater EJB which is defined as follows:
Listing 71. GreaterLocal.java
public interface GreaterLocal {
String hello(String name);
String bye(String name);
}
And the implementation
Listing 72. GreaterImpl.java
@Stateless
public class GreaterImpl implements GreaterLocal {
public String hello(String name) {
return "Hello " + name;
}
public String bye(String name) {
return "Bye " + name;
}
}
Using Java DSL
In this example we want to invoke the hello method on the EJB. Since this
example is based on an unit test using Apache OpenEJB we have to set a
JndiContext on the EJB component with the OpenEJB settings.
@Override
protected CamelContext createCamelContext() throws Exception {
CamelContext answer = new DefaultCamelContext();
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
568
// enlist EJB component using the JndiContext
EjbComponent ejb = answer.getComponent("ejb", EjbComponent.class);
ejb.setContext(createEjbContext());
return answer;
}
private static Context createEjbContext() throws NamingException {
// here we need to define our context factory to use OpenEJB for our testing
Properties properties = new Properties();
properties.setProperty(Context.INITIAL_CONTEXT_FACTORY,
"org.apache.openejb.client.LocalInitialContextFactory");
return new InitialContext(properties);
}
Then we are ready to use the EJB in the Camel route:
from("direct:start")
// invoke the greeter EJB using the local interface and invoke the hello method
.to("ejb:GreaterImplLocal?method=hello")
.to("mock:result");
Using Spring XML
And this is the same example using Spring XML instead:
Again since this is based on an unit test we need to setup the EJB
component:
<!-- setup Camel EJB component -->
<bean id="ejb" class="org.apache.camel.component.ejb.EjbComponent">
<property name="properties" ref="jndiProperties"/>
</bean>
<!-- use OpenEJB context factory -->
<p:properties id="jndiProperties">
<prop
key="java.naming.factory.initial">org.apache.openejb.client.LocalInitialContextFactory</prop>
</p:properties>
Before we are ready to use EJB in the Camel routes:
<camelContext xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="direct:start"/>
<to uri="ejb:GreaterImplLocal?method=hello"/>
<to uri="mock:result"/>
569
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
In a real application server
In a real application server you most likely do not have to setup a
JndiContext on the EJB component as it will create a default
JndiContext on the same JVM as the application server, which
usually allows it to access the JNDI registry and lookup the EJBs.
However if you need to access a application server on a remote JVM
or the likes, you have to prepare the properties beforehand.
</route>
</camelContext>
See Also
•
•
•
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
Bean
Bean Binding
Bean Integration
ESPER
The Esper component supports the Esper Library for Event Stream
Processing. The camel-esper library is provided by the Camel Extra project
which hosts all *GPL related components for Camel.
URI format
esper:name[?options]
When consuming from an Esper endpoint you must specify a pattern or eql
statement to query the event stream.
For example
from("esper://cheese?pattern=every event=MyEvent(bar=5)").
to("activemq:Foo");
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
570
Options
Name
Default Value
Description
pattern
Â
The Esper Pattern expression as a String to filter events
eql
Â
The Esper EQL expression as a String to filter events
You can append query options to the URI in the following format,
?option=value&option=value&...
Demo
There is a demo which shows how to work with ActiveMQ, Camel and Esper in
the Camel Extra project
See Also
•
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
Esper Camel Demo
EVENT COMPONENT
The event: component provides access to the Spring ApplicationEvent
objects. This allows you to publish ApplicationEvent objects to a Spring
ApplicationContext or to consume them. You can then use Enterprise
Integration Patterns to process them such as Message Filter.
URI format
spring-event://default
If you use Camel 1.x then you may need to remove the // to get it working
with the Spring event notification
spring-event:default
See Also
• Configuring Camel
• Component
• Endpoint
571
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
• Getting Started
FILE COMPONENT - CAMEL 2.0 ONWARDS
The File component provides access to file systems, allowing files to be
processed by any other Camel Components or messages from other
components to be saved to disk.
URI format
file:directoryName[?options]
or
file://directoryName[?options]
Where directoryName represents the underlying file directory.
You can append query options to the URI in the following format,
?option=value&option=value&...
URI Options
Common
Name
Default
Value
Description
autoCreate
true
Automatically create missing directories in the file's pathname. For the file consumer, that means creating the
starting directory. For the file producer, it means the directory to where the files should be written.
bufferSize
128kb
Write buffer sized in bytes.
fileName
null
Use Expression such as File Language to dynamically set the filename. For consumers, it's used as a filename
filter. For producers, it's used to evaluate the filename to write. If an expression is set, it take precedence over
the CamelFileName header. (Note: The header itself can also be an Expression). The expression options support
both String and Expression types. If the expression is a String type, it is always evaluated using the File
Language. If the expression is an Expression type, the specified Expression type is used - this allows you, for
instance, to use OGNL expressions. For the consumer, you can use it to filter filenames, so you can for instance
consume today's file using the File Language syntax: mydata-${date:now:yyyyMMdd}.txt.
flatten
false
Flatten is used to flatten the file name path to strip any leading paths, so it's just the file name. This allows you
to consume recursively into sub-directories, but when you eg write the files to another directory they will be
written in a single directory. Setting this to true on the producer enforces that any file name recived in
CamelFileName header will be stripped for any leading paths.
charset
null
Camel 2.5: this option is used to specify the encoding of the file, and camel will set the Exchange property with
Exchange.CHARSET_NAME with the value of this option.
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
572
Using Camel 1.x
This documentation is only for Camel 2.0 or newer. If you are using
Camel 1.x then see this link instead.
Only directories
Camel 2.0 only support endpoints configured with a starting
directory. So the directoryName must be a directory.
If you want to consume a single file only, you can use the fileName
option, e.g. by setting fileName=thefilename.
Also, the starting directory must not contain dynamic expressions
with ${ } placeholders. Again use the fileName option to specify
the dynamic part of the filename.
In Camel 1.x you could also configure a file and this caused more harm
than good as it could lead to confusing situations.
Avoid reading files currently being written by another
application
Beware the JDK File IO API is a bit limited in detecting whether
another application is currently writing/copying a file. And the
implementation can be different depending on OS platform as well.
This could lead to that Camel thinks the file is not locked by another
process and start consuming it. Therefore you have to do you own
investigation what suites your environment. To help with this Camel
provides different readLock options and doneFileOption option
that you can use. See also the section Consuming files from folders
where others drop files directly.
Consumer
573
Name
Default
Value
Description
initialDelay
1000
Milliseconds before polling the file/directory starts.
delay
500
Milliseconds before the next poll of the file/directory.
useFixedDelay
false
Set to true to use fixed delay between pools, otherwise fixed rate is used. See
ScheduledExecutorService in JDK for details.
recursive
false
If a directory, will look for files in all the sub-directories as well.
delete
false
If true, the file will be deleted after it is processed
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
noop
false
If true, the file is not moved or deleted in any way. This option is good for readonly data, or
for ETL type requirements. If noop=true, Camel will set idempotent=true as well, to avoid
consuming the same files over and over again.
preMove
null
Expression (such as File Language) used to dynamically set the filename when moving it
before processing. For example to move in-progress files into the order directory set this
value to order.
move
.camel
Expression (such as File Language) used to dynamically set the filename when moving it
after processing. To move files into a .done subdirectory just enter .done.
moveFailed
null
Expression (such as File Language) used to dynamically set a different target directory when
moving files after processing (configured via move defined above) failed. For example, to
move files into a .error subdirectory use: .error. Note: When moving the files to the
“fail� location Camel will handle the error and will not pick up the file again.
include
null
Is used to include files, if filename matches the regex pattern.
exclude
null
Is used to exclude files, if filename matches the regex pattern.
idempotent
false
Option to use the Idempotent Consumer EIP pattern to let Camel skip already processed files.
Will by default use a memory based LRUCache that holds 1000 entries. If noop=true then
idempotent will be enabled as well to avoid consuming the same files over and over again.
idempotentRepository
null
Pluggable repository as a org.apache.camel.processor.idempotent.MessageIdRepository
class. Will by default use MemoryMessageIdRepository if none is specified and idempotent
is true.
inProgressRepository
memory
Pluggable in-progress repository as a
org.apache.camel.processor.idempotent.MessageIdRepository class. The in-progress
repository is used to account the current in progress files being consumed. By default a
memory based repository is used.
filter
null
Pluggable filter as a org.apache.camel.component.file.GenericFileFilter class. Will
skip files if filter returns false in its accept() method. Camel also ships with an ANT path
matcher filter in the camel-spring component. More details in section below.
sorter
null
Pluggable sorter as a java.util.Comparator<org.apache.camel.component.file.GenericFile>
class.
sortBy
null
Built-in sort using the File Language. Supports nested sorts, so you can have a sort by file
name and as a 2nd group sort by modified date. See sorting section below for details.
markerFile
Used by consumer, to only poll the files if it has exclusive read-lock on the file (i.e. the file is
not in-progress or being written). Camel will wait until the file lock is granted.
This option provides the build in strategies:
markerFile is the behaviour from Camel 1.x, where Camel will create a marker file and hold
a lock on the marker file. This option is not avail for the FTP component.
changed is using file length/modification timestamp to detect whether the file is currently
being copied or not. Will at least use 1 sec. to determine this, so this option cannot consume
files as fast as the others, but can be more reliable as the JDK IO API cannot always
determine whether a file is currently being used by another process. This option is not avail
for the FTP component.
fileLock is for using java.nio.channels.FileLock. This option is not avail for the FTP
component.
rename is for using a try to rename the file as a test if we can get exclusive read-lock.
none is for no read locks at all.
▪
Optional timeout in millis for the read-lock, if supported by the read-lock. If the read-lock
could not be granted and the timeout triggered, then Camel will skip the file. At next poll
Camel, will try the file again, and this time maybe the read-lock could be granted. Use a
value of 0 or lower to indicate forever. In Camel 2.0 the default value is 0. In Camel 2.1 the
default value is 10000. Currently fileLock, changed and rename support the timeout.
readLock
readLockTimeout
readLockCheckInterval
1000
Camel 2.6: Interval in millis for the read-lock, if supported by the read lock. This interval is
used for sleeping between attempts to acquire the read lock. For example when using the
changed read lock, you can set a higher interval period to cater for slow writes. The default
of 1 sec. may be too fast if the producer is very slow writing the file.
exclusiveReadLockStrategy
null
Pluggable read-lock as a
org.apache.camel.component.file.GenericFileExclusiveReadLockStrategy
implementation.
processStrategy
null
A pluggable org.apache.camel.component.file.GenericFileProcessStrategy allowing
you to implement your own readLock option or similar. Can also be used when special
conditions must be met before a file can be consumed, such as a special ready file exists. If
this option is set then the readLock option does not apply.
maxMessagesPerPoll
0
An integer that defines the maximum number of messages to gather per poll. By default, no
maximum is set. Can be used to set a limit of e.g. 1000 to avoid having the server read
thousands of files as it starts up. Set a value of 0 or negative to disabled it.
startingDirectoryMustExist
false
Camel 2.5: Whether the starting directory must exist. Mind that the autoCreate option is
default enabled, which means the starting directory is normally auto created if it doesn't
exist. You can disable autoCreate and enable this to ensure the starting directory must exist.
Will thrown an exception if the directory doesn't exist.
directoryMustExist
false
Camel 2.5: Similar to startingDirectoryMustExist but this applies during polling
recursive sub directories.
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
574
doneFileName
null
Camel 2.6: If provided, Camel will only consume files if a done file exists. This option
configures what file name to use. Either you can specify a fixed name. Or you can use
dynamic placeholders. The done file is always expected in the same folder as the original
file. See using done file and writing done file sections for examples.
maxMessagesPerPoll
0
An integer to define a maximum messages to gather per poll. By default no maximum is set.
Can be used to set a limit of e.g. 1000 to avoid when starting up the server that there are
thousands of files. Set a value of 0 or negative to disabled it. See more details at Batch
Consumer.
Default behavior for file consumer
• By default the file is locked for the duration of the processing.
• After the route has completed, files are moved into the .camel
subdirectory, so that they appear to be deleted.
• The File Consumer will always skip any file whose name starts with a
dot, such as ., .camel, .m2 or .groovy.
• Only files (not directories) are matched for valid filename, if options
such as: include or exclude are used.
Producer
Name
Default
Value
Description
fileExist
Override
What to do if a file already exists with the same name. The following values can be specified:
Override, Append, Fail and Ignore. Override, which is the default, replaces the existing file.
Append adds content to the existing file. Fail throws a GenericFileOperationException,
indicating that there is already an existing file. Ignore silently ignores the problem and does not
override the existing file, but assumes everything is okay.
tempPrefix
null
This option is used to write the file using a temporary name and then, after the write is complete,
rename it to the real name. Can be used to identify files being written and also avoid consumers
(not using exclusive read locks) reading in progress files. Is often used by FTP when uploading big
files.
tempFileName
null
Camel 2.1: The same as tempPrefix option but offering a more fine grained control on the naming
of the temporary filename as it uses the File Language.
keepLastModified
false
Camel 2.2: Will keep the last modified timestamp from the source file (if any). Will use the
Exchange.FILE_LAST_MODIFIED header to located the timestamp. This header can contain either a
java.util.Date or long with the timestamp. If the timestamp exists and the option is enabled it
will set this timestamp on the written file. Note: This option only applies to the file producer. You
cannot use this option with any of the ftp producers.
eagerDeleteTargetFile
true
Camel 2.3: Whether or not to eagerly delete any existing target file. This option only applies when
you use fileExists=Override and the tempFileName option as well. You can use this to disable
(set it to false) deleting the target file before the temp file is written. For example you may write big
files and want the target file to exists during the temp file is being written. This ensure the target
file is only deleted until the very last moment, just before the temp file is being renamed to the
target filename.
doneFileName
null
Camel 2.6: If provided, then Camel will write a 2nd done file when the original file has been
written. The done file will be empty. This option configures what file name to use. Either you can
specify a fixed name. Or you can use dynamic placeholders. The done file will always be written in
the same folder as the original file. See writing done file section for examples.
Default behavior for file producer
• By default it will override any existing file, if one exist with the same
name.
575
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
Override is now default
In Camel 1.x the Append is the default for the file producer. We have
changed this to Override in Camel 2.0 as this is also the default file
operation using java.io.File.
And also the default for the FTP library we use in the camel-ftp
component.
Move and Delete operations
Any move or delete operations is executed after (post command) the routing
has completed; so during processing of the Exchange the file is still located in
the inbox folder.
Lets illustrate this with an example:
from("file://inbox?move=.done").to("bean:handleOrder");
When a file is dropped in the inbox folder, the file consumer notices this and
creates a new FileExchange that is routed to the handleOrder bean. The
bean then processes the File object. At this point in time the file is still
located in the inbox folder. After the bean completes, and thus the route is
completed, the file consumer will perform the move operation and move the
file to the .done sub-folder.
The move and preMove options should be a directory name, which can
be either relative or absolute. If relative, the directory is created as a subfolder from within the folder where the file was consumed.
By default, Camel will move consumed files to the .camel sub-folder
relative to the directory where the file was consumed.
If you want to delete the file after processing, the route should be:
from("file://inobox?delete=true").to("bean:handleOrder");
We have introduced a pre move operation to move files before they are
processed. This allows you to mark which files have been scanned as they
are moved to this sub folder before being processed.
from("file://inbox?preMove=inprogress").to("bean:handleOrder");
You can combine the pre move and the regular move:
from("file://inbox?preMove=inprogress&move=.done").to("bean:handleOrder");
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
576
So in this situation, the file is in the inprogress folder when being processed
and after it's processed, it's moved to the .done folder.
Fine grained control over Move and PreMove option
The move and preMove option is Expression-based, so we have the full
power of the File Language to do advanced configuration of the directory and
name pattern.
Camel will, in fact, internally convert the directory name you enter into a File
Language expression. So when we enter move=.done Camel will convert this
into: ${file:parent}/.done/${file:onlyname}. This is only done if Camel
detects that you have not provided a ${ } in the option value yourself. So
when you enter a ${ } Camel will not convert it and thus you have the full
power.
So if we want to move the file into a backup folder with today's date as the
pattern, we can do:
move=backup/${date:now:yyyyMMdd}/${file:name}
About moveFailed
The moveFailed option allows you to move files that could not be processed
succesfully to another location such as a error folder of your choice. For
example to move the files in an error folder with a timestamp you can use
moveFailed=/error/${file:name.noext}${date:now:yyyyMMddHHmmssSSS}.${file:ext}.
See more examples at File Language
Message Headers
The following headers are supported by this component:
File producer only
577
Header
Description
CamelFileName
Specifies the name of the file to write (relative to the endpoint directory). The name can be a String; a String with
a File Language or Simple expression; or an Expression object. If it's null then Camel will auto-generate a filename
based on the message unique ID.
CamelFileNameProduced
The actual absolute filepath (path + name) for the output file that was written. This header is set by Camel and its
purpose is providing end-users with the name of the file that was written.
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
File consumer only
Header
Description
CamelFileName
Name of the consumed file as a relative file path with offset from the starting directory configured on the endpoint.
CamelFileNameOnly
Only the file name (the name with no leading paths).
CamelFileAbsolute
A boolean option specifying whether the consumed file denotes an absolute path or not. Should normally be false
for relative paths. Absolute paths should normally not be used but we added to the move option to allow moving
files to absolute paths. But can be used elsewhere as well.
CamelFileAbsolutePath
The absolute path to the file. For relative files this path holds the relative path instead.
CamelFilePath
The file path. For relative files this is the starting directory + the relative filename. For absolute files this is the
absolute path.
CamelFileRelativePath
The relative path.
CamelFileParent
The parent path.
CamelFileLength
A long value containing the file size.
CamelFileLastModified
A Date value containing the last modified timestamp of the file.
Batch Consumer
This component implements the Batch Consumer.
Exchange Properties, file consumer only
As the file consumer is BatchConsumer it supports batching the files it polls.
By batching it means that Camel will add some properties to the Exchange so
you know the number of files polled the current index in that order.
Property
Description
CamelBatchSize
The total number of files that was polled in this batch.
CamelBatchIndex
The current index of the batch. Starts from 0.
CamelBatchComplete
A boolean value indicating the last Exchange in the batch. Is only true for the last entry.
This allows you for instance to know how many files exists in this batch and
for instance let the Aggregator2 aggregate this number of files.
Common gotchas with folder and filenames
When Camel is producing files (writing files) there are a few gotchas affecting
how to set a filename of your choice. By default, Camel will use the message
ID as the filename, and since the message ID is normally a unique generated
ID, you will end up with filenames such as: IDMACHINENAME-2443-1211718892437-1-0. If such a filename is not desired,
then you must provide a filename in the CamelFileName message header.
The constant, Exchange.FILE_NAME, can also be used.
The sample code below produces files using the message ID as the
filename:
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
578
from("direct:report").to("file:target/reports");
To use report.txt as the filename you have to do:
from("direct:report").setHeader(Exchange.FILE_NAME, constant("report.txt")).to(
"file:target/reports");
... the same as above, but with CamelFileName:
from("direct:report").setHeader("CamelFileName", constant("report.txt")).to(
"file:target/reports");
And a syntax where we set the filename on the endpoint with the fileName
URI option.
from("direct:report").to("file:target/reports/?fileName=report.txt");
Filename Expression
Filename can be set either using the expression option or as a string-based
File Language expression in the CamelFileName header. See the File
Language for syntax and samples.
Consuming files from folders where others drop files directly
Beware if you consume files from a folder where other applications write files
directly. Take a look at the different readLock options to see what suits your
use cases. The best approach is however to write to another folder and after
the write move the file in the drop folder. However if you write files directly to
the drop folder then the option changed could better detect whether a file is
currently being written/copied as it uses a file changed algorithm to see
whether the file size / modification changes over a period of time. The other
read lock options rely on Java File API that sadly is not always very good at
detecting this. You may also want to look at the doneFileName option, which
uses a marker file (done) to signal when a file is done and ready to be
consumed.
Using done files
Available as of Camel 2.6
See also section writing done files below.
579
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
If you want only to consume files when a done file exist, then you can use
the doneFileName option on the endpoint.
from("file:bar?doneFileName=done");
Will only consume files from the bar folder, if a file name done exists in the
same directory as the target files. Camel will automatic delete the done file
when it's done consuming the files.
However its more common to have one done file per target file. This
means there is a 1:1 correlation. To do this you must use dynamic
placeholders in the doneFileName option. Currently Camel supports the
following two dynamic tokens: file:name and file:name.noext which must
be enclosed in ${ }. The consumer only supports the static part of the done
file name as either prefix or suffix (not both).
from("file:bar?doneFileName=${file:name}.done");
In this example only files will be polled if there exists a done file with the
name file name.done. For example
▪ hello.txt - is the file to be consumed
▪ hello.txt.done - is the associated done file
You can also use a prefix for the done file, such as:
from("file:bar?doneFileName=ready-${file:name}");
▪ hello.txt - is the file to be consumed
▪ ready-hello.txt - is the associated done file
Writing done files
Available as of Camel 2.6
After you have written af file you may want to write an additional done file
as a kinda of marker, to indicate to others that the file is finished and has
been written. To do that you can use the doneFileName option on the file
producer endpoint.
.to("file:bar?doneFileName=done");
Will simply create a file named done in the same directory as the target file.
However its more common to have one done file per target file. This
means there is a 1:1 correlation. To do this you must use dynamic
placeholders in the doneFileName option. Currently Camel supports the
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
580
following two dynamic tokens: file:name and file:name.noext which must
be enclosed in ${ }.
.to("file:bar?doneFileName=done-${file:name}");
Will for example create a file named done-foo.txt if the target file was
foo.txt in the same directory as the target file.
.to("file:bar?doneFileName=${file:name}.done");
Will for example create a file named foo.txt.done if the target file was
foo.txt in the same directory as the target file.
.to("file:bar?doneFileName=${file:name.noext}.done");
Will for example create a file named foo.done if the target file was foo.txt
in the same directory as the target file.
Samples
Read from a directory and write to another directory
from("file://inputdir/?delete=true").to("file://outputdir")
Listen on a directory and create a message for each file dropped there. Copy
the contents to the outputdir and delete the file in the inputdir.
Reading recursive from a directory and write the another
from("file://inputdir/?recursive=true&delete=true").to("file://outputdir")
Listen on a directory and create a message for each file dropped there. Copy
the contents to the outputdir and delete the file in the inputdir. Will scan
recursively into sub-directories. Will lay out the files in the same directory
structure in the outputdir as the inputdir, including any sub-directories.
inputdir/foo.txt
inputdir/sub/bar.txt
Will result in the following output layout:
581
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
outputdir/foo.txt
outputdir/sub/bar.txt
Using flatten
If you want to store the files in the outputdir directory in the same directory,
disregarding the source directory layout (e.g. to flatten out the path), you
just add the flatten=true option on the file producer side:
from("file://inputdir/
?recursive=true&delete=true").to("file://outputdir?flatten=true")
Will result in the following output layout:
outputdir/foo.txt
outputdir/bar.txt
Reading from a directory and the default move operation
Camel will by default move any processed file into a .camel subdirectory in
the directory the file was consumed from.
from("file://inputdir/?recursive=true&delete=true").to("file://outputdir")
Affects the layout as follows:
before
inputdir/foo.txt
inputdir/sub/bar.txt
after
inputdir/.camel/foo.txt
inputdir/sub/.camel/bar.txt
outputdir/foo.txt
outputdir/sub/bar.txt
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
582
Read from a directory and process the message in java
from("file://inputdir/").process(new Processor() {
public void process(Exchange exchange) throws Exception {
Object body = exchange.getIn().getBody();
// do some business logic with the input body
}
});
The body will be a File object that points to the file that was just dropped
into the inputdir directory.
Read files from a directory and send the content to a jms
queue
from("file://inputdir/").convertBodyTo(String.class).to("jms:test.queue")
By default the file endpoint sends a FileMessage which contains a File
object as the body. If you send this directly to the JMS component the JMS
message will only contain the File object but not the content. By converting
the File to a String, the message will contain the file contents what is
probably what you want.
The route above using Spring DSL:
<route>
<from uri="file://inputdir/"/>
<convertBodyTo type="java.lang.String"/>
<to uri="jms:test.queue"/>
</route>
Writing to files
Camel is of course also able to write files, i.e. produce files. In the sample
below we receive some reports on the SEDA queue that we processes before
they are written to a directory.
public void testToFile() throws Exception {
MockEndpoint mock = getMockEndpoint("mock:result");
mock.expectedMessageCount(1);
mock.expectedFileExists("target/test-reports/report.txt");
template.sendBody("direct:reports", "This is a great report");
583
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
assertMockEndpointsSatisfied();
}
protected JndiRegistry createRegistry() throws Exception {
// bind our processor in the registry with the given id
JndiRegistry reg = super.createRegistry();
reg.bind("processReport", new ProcessReport());
return reg;
}
protected RouteBuilder createRouteBuilder() throws Exception {
return new RouteBuilder() {
public void configure() throws Exception {
// the reports from the seda queue is processed by our processor
// before they are written to files in the target/reports directory
from("direct:reports").processRef("processReport").to("file://target/
test-reports", "mock:result");
}
};
}
private class ProcessReport implements Processor {
public void process(Exchange exchange) throws Exception {
String body = exchange.getIn().getBody(String.class);
// do some business logic here
// set the output to the file
exchange.getOut().setBody(body);
// set the output filename using java code logic, notice that this is done by
setting
// a special header property of the out exchange
exchange.getOut().setHeader(Exchange.FILE_NAME, "report.txt");
}
}
Write to subdirectory using Exchange.FILE_NAME
Using a single route, it is possible to write a file to any number of
subdirectories. If you have a route setup as such:
<route>
<from uri="bean:myBean"/>
<to uri="file:/rootDirectory"/>
</route>
You can have myBean set the header Exchange.FILE_NAME to values such as:
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
584
Exchange.FILE_NAME = hello.txt => /rootDirectory/hello.txt
Exchange.FILE_NAME = foo/bye.txt => /rootDirectory/foo/bye.txt
This allows you to have a single route to write files to multiple destinations.
Using expression for filenames
In this sample we want to move consumed files to a backup folder using
today's date as a sub-folder name:
from("file://inbox?move=backup/${date:now:yyyyMMdd}/${file:name}").to("...");
See File Language for more samples.
Avoiding reading the same file more than once (idempotent
consumer)
Camel supports Idempotent Consumer directly within the component so it
will skip already processed files. This feature can be enabled by setting the
idempotent=true option.
from("file://inbox?idempotent=true").to("...");
By default Camel uses a in memory based store for keeping track of
consumed files, it uses a least recently used cache storing holding up to
1000 entries. You can plugin your own implementation of this store by using
the idempotentRepository option using the # sign in the value to indicate
it's a referring to a bean in the Registry with the specified id.
<!-- define our store as a plain spring bean -->
<bean id="myStore" class="com.mycompany.MyIdempotentStore"/>
<route>
<from uri="file://inbox?idempotent=true&amp;idempotentRepository=#myStore"/>
<to uri="bean:processInbox"/>
</route>
Camel will log at DEBUG level if it skips a file because it has been consumed
before:
DEBUG FileConsumer is idempotent and the file has been consumed before. Will skip
this file: target\idempotent\report.txt
585
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
Using a file based idempotent repository
In this section we will use the file based idempotent repository
org.apache.camel.processor.idempotent.FileIdempotentRepository
instead of the in-memory based that is used as default.
This repository uses a 1st level cache to avoid reading the file repository. It
will only use the file repository to store the content of the 1st level cache.
Thereby the repository can survive server restarts. It will load the content of
the file into the 1st level cache upon startup. The file structure is very simple
as it store the key in separate lines in the file. By default, the file store has a
size limit of 1mb when the file grew larger Camel will truncate the file store
be rebuilding the content by flushing the 1st level cache in a fresh empty file.
We configure our repository using Spring XML creating our file idempotent
repository and define our file consumer to use our repository with the
idempotentRepository using # sign to indicate Registry lookup:
<!-- this is our file based idempotent store configured to use the .filestore.dat as
file -->
<bean id="fileStore"
class="org.apache.camel.processor.idempotent.FileIdempotentRepository">
<!-- the filename for the store -->
<property name="fileStore" value="target/fileidempotent/.filestore.dat"/>
<!-- the max filesize in bytes for the file. Camel will trunk and flush the cache
if the file gets bigger -->
<property name="maxFileStoreSize" value="512000"/>
<!-- the number of elements in our store -->
<property name="cacheSize" value="250"/>
</bean>
<camelContext xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="file://target/fileidempotent/
?idempotent=true&amp;idempotentRepository=#fileStore&amp;move=done/${file:name}"/>
<to uri="mock:result"/>
</route>
</camelContext>
Using a JPA based idempotent repository
In this section we will use the JPA based idempotent repository instead of the
in-memory based that is used as default.
First we need a persistence-unit in META-INF/persistence.xml where we
need to use the class
org.apache.camel.processor.idempotent.jpa.MessageProcessed as
model.
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
586
<persistence-unit name="idempotentDb" transaction-type="RESOURCE_LOCAL">
<class>org.apache.camel.processor.idempotent.jpa.MessageProcessed</class>
<properties>
<property name="openjpa.ConnectionURL" value="jdbc:derby:target/
idempotentTest;create=true"/>
<property name="openjpa.ConnectionDriverName"
value="org.apache.derby.jdbc.EmbeddedDriver"/>
<property name="openjpa.jdbc.SynchronizeMappings" value="buildSchema"/>
<property name="openjpa.Log" value="DefaultLevel=WARN, Tool=INFO"/>
</properties>
</persistence-unit>
Then we need to setup a Spring jpaTemplate in the spring XML file:
<!-- this is standard spring JPA configuration -->
<bean id="jpaTemplate" class="org.springframework.orm.jpa.JpaTemplate">
<property name="entityManagerFactory" ref="entityManagerFactory"/>
</bean>
<bean id="entityManagerFactory"
class="org.springframework.orm.jpa.LocalEntityManagerFactoryBean">
<!-- we use idempotentDB as the persitence unit name defined in the
persistence.xml file -->
<property name="persistenceUnitName" value="idempotentDb"/>
</bean>
And finally we can create our JPA idempotent repository in the spring XML file
as well:
<!-- we define our jpa based idempotent repository we want to use in the file
consumer -->
<bean id="jpaStore"
class="org.apache.camel.processor.idempotent.jpa.JpaMessageIdRepository">
<!-- Here we refer to the spring jpaTemplate -->
<constructor-arg index="0" ref="jpaTemplate"/>
<!-- This 2nd parameter is the name (= a cateogry name).
You can have different repositories with different names -->
<constructor-arg index="1" value="FileConsumer"/>
</bean>
And yes then we just need to refer to the jpaStore bean in the file consumer
endpoint using the [[idempotentRepository}} using the # syntax option:
<route>
<from uri="file://inbox?idempotent=true&amp;idempotentRepository=#jpaStore"/>
<to uri="bean:processInbox"/>
</route>
587
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
Filter using org.apache.camel.component.file.GenericFileFilter
Camel supports pluggable filtering strategies. You can then configure the
endpoint with such a filter to skip certain files being processed.
In the sample we have build our own filter that skips files starting with
skip in the filename:
public class MyFileFilter implements GenericFileFilter {
public boolean accept(GenericFile pathname) {
// we dont accept any files starting with skip in the name
return !pathname.getFileName().startsWith("skip");
}
}
And then we can configure our route using the filter attribute to reference
our filter (using # notation) that we have defines in the spring XML file:
<!-- define our sorter as a plain spring bean -->
<bean id="myFilter" class="com.mycompany.MyFileSorter"/>
<route>
<from uri="file://inbox?filter=#myFilter"/>
<to uri="bean:processInbox"/>
</route>
Filtering using ANT path matcher
The ANT path matcher is shipped out-of-the-box in the camel-spring jar. So
you need to depend on camel-spring if you are using Maven.
The reasons is that we leverage Spring's AntPathMatcher to do the actual
matching.
The file paths is matched with the following rules:
▪ ? matches one character
▪ * matches zero or more characters
▪ ** matches zero or more directories in a path
The sample below demonstrates how to use it:
<camelContext xmlns="http://camel.apache.org/schema/spring">
<template id="camelTemplate"/>
<!-- use myFilter as filter to allow setting ANT paths for which files to scan
for -->
<endpoint id="myFileEndpoint" uri="file://target/
antpathmatcher?recursive=true&amp;filter=#myAntFilter"/>
<route>
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
588
<from ref="myFileEndpoint"/>
<to uri="mock:result"/>
</route>
</camelContext>
<!-- we use the antpath file filter to use ant paths for includes and exlucde -->
<bean id="myAntFilter"
class="org.apache.camel.component.file.AntPathMatcherGenericFileFilter">
<!-- include and file in the subfolder that has day in the name -->
<property name="includes" value="**/subfolder/**/*day*"/>
<!-- exclude all files with bad in name or .xml files. Use comma to seperate
multiple excludes -->
<property name="excludes" value="**/*bad*,**/*.xml"/>
</bean>
Sorting using Comparator
Camel supports pluggable sorting strategies. This strategy it to use the build
in java.util.Comparator in Java. You can then configure the endpoint with
such a comparator and have Camel sort the files before being processed.
In the sample we have built our own comparator that just sorts by file
name:
public class MyFileSorter implements Comparator<GenericFile> {
public int compare(GenericFile o1, GenericFile o2) {
return o1.getFileName().compareToIgnoreCase(o2.getFileName());
}
}
And then we can configure our route using the sorter option to reference to
our sorter (mySorter) we have defined in the spring XML file:
<!-- define our sorter as a plain spring bean -->
<bean id="mySorter" class="com.mycompany.MyFileSorter"/>
<route>
<from uri="file://inbox?sorter=#mySorter"/>
<to uri="bean:processInbox"/>
</route>
Sorting using sortBy
Camel supports pluggable sorting strategies. This strategy it to use the File
Language to configure the sorting. The sortBy option is configured as
follows:
589
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
URI options can reference beans using the # syntax
In the Spring DSL route about notice that we can refer to beans in
the Registry by prefixing the id with #. So writing
sorter=#mySorter, will instruct Camel to go look in the Registry for
a bean with the ID, mySorter.
sortBy=group 1;group 2;group 3;...
Where each group is separated with semi colon. In the simple situations you
just use one group, so a simple example could be:
sortBy=file:name
This will sort by file name, you can reverse the order by prefixing reverse:
to the group, so the sorting is now Z..A:
sortBy=reverse:file:name
As we have the full power of File Language we can use some of the other
parameters, so if we want to sort by file size we do:
sortBy=file:length
You can configure to ignore the case, using ignoreCase: for string
comparison, so if you want to use file name sorting but to ignore the case
then we do:
sortBy=ignoreCase:file:name
You can combine ignore case and reverse, however reverse must be specified
first:
sortBy=reverse:ignoreCase:file:name
In the sample below we want to sort by last modified file, so we do:
sortBy=file:modifed
And then we want to group by name as a 2nd option so files with same
modifcation is sorted by name:
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
590
sortBy=file:modifed;file:name
Now there is an issue here, can you spot it? Well the modified timestamp of
the file is too fine as it will be in milliseconds, but what if we want to sort by
date only and then subgroup by name?
Well as we have the true power of File Language we can use the its date
command that supports patterns. So this can be solved as:
sortBy=date:file:yyyyMMdd;file:name
Yeah, that is pretty powerful, oh by the way you can also use reverse per
group, so we could reverse the file names:
sortBy=date:file:yyyyMMdd;reverse:file:name
Using GenericFileProcessStrategy
The option processStrategy can be used to use a custom
GenericFileProcessStrategy that allows you to implement your own begin,
commit and rollback logic.
For instance lets assume a system writes a file in a folder you should
consume. But you should not start consuming the file before another ready
file have been written as well.
So by implementing our own GenericFileProcessStrategy we can
implement this as:
▪ In the begin() method we can test whether the special ready file
exists. The begin method returns a boolean to indicate if we can
consume the file or not.
▪ in the commit() method we can move the actual file and also delete
the ready file.
Debug logging
This component has log level TRACE that can be helpful if you have
problems.
See Also
• Configuring Camel
• Component
• Endpoint
591
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
• Getting Started
▪ File Language
▪ FTP2
FLATPACK COMPONENT
The Flatpack component supports fixed width and delimited file parsing via
the FlatPack library.
Notice: This component only supports consuming from flatpack files to
Object model. You can not (yet) write from Object model to flatpack format.
Maven users will need to add the following dependency to their pom.xml
for this component:
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-flatpack</artifactId>
<version>x.x.x</version>
<!-- use the same version as your Camel core version -->
</dependency>
URI format
flatpack:[delim|fixed]:flatPackConfig.pzmap.xml[?options]
Or for a delimited file handler with no configuration file just use
flatpack:someName[?options]
You can append query options to the URI in the following format,
?option=value&option=value&...
URI Options
Name
Default
Value
Description
delimiter
,
The default character delimiter for delimited files.
textQualifier
"
The text qualifier for delimited files.
ignoreFirstRecord
true
Whether the first line is ignored for delimited files (for the column headers).
splitRows
true
As of Camel 1.5, the component can either process each row one by one or the entire content
at once.
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
592
Examples
• flatpack:fixed:foo.pzmap.xml creates a fixed-width endpoint
using the foo.pzmap.xml file configuration.
• flatpack:delim:bar.pzmap.xml creates a delimited endpoint using
the bar.pzmap.xml file configuration.
• flatpack:foo creates a delimited endpoint called foo with no file
configuration.
Message Headers
Camel will store the following headers on the IN message:
Header
Description
camelFlatpackCounter
The current row index. For splitRows=false the counter is the total number of rows.
Message Body
The component delivers the data in the IN message as a
org.apache.camel.component.flatpack.DataSetList object that has
converters for java.util.Map or java.util.List.
Usually you want the Map if you process one row at a time (splitRows=true).
Use List for the entire content (splitRows=false), where each element in
the list is a Map.
Each Map contains the key for the column name and its corresponding value.
For example to get the firstname from the sample below:
Map row = exchange.getIn().getBody(Map.class);
String firstName = row.get("FIRSTNAME");
However, you can also always get it as a List (even for splitRows=true).
The same example:
List data = exchange.getIn().getBody(List.class);
Map row = (Map)data.get(0);
String firstName = row.get("FIRSTNAME");
Header and Trailer records
In Camel 1.5 onwards the header and trailer notions in Flatpack are
supported. However, you must use fixed record IDs:
• header for the header record (must be lowercase)
• trailer for the trailer record (must be lowercase)
593
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
The example below illustrates this fact that we have a header and a trailer.
You can omit one or both of them if not needed.
<RECORD id="header" startPosition="1" endPosition="3" indicator="HBT">
<COLUMN name="INDICATOR" length="3"/>
<COLUMN name="DATE" length="8"/>
</RECORD>
<COLUMN
<COLUMN
<COLUMN
<COLUMN
<COLUMN
<COLUMN
name="FIRSTNAME" length="35" />
name="LASTNAME" length="35" />
name="ADDRESS" length="100" />
name="CITY" length="100" />
name="STATE" length="2" />
name="ZIP" length="5" />
<RECORD id="trailer" startPosition="1" endPosition="3" indicator="FBT">
<COLUMN name="INDICATOR" length="3"/>
<COLUMN name="STATUS" length="7"/>
</RECORD>
Using the endpoint
A common use case is sending a file to this endpoint for further processing in
a separate route. For example:
<camelContext xmlns="http://activemq.apache.org/camel/schema/spring">
<route>
<from uri="file://someDirectory"/>
<to uri="flatpack:foo"/>
</route>
<route>
<from uri="flatpack:foo"/>
...
</route>
</camelContext>
You can also convert the payload of each message created to a Map for easy
Bean Integration
FLATPACK DATAFORMAT
The Flatpack component ships with the Flatpack data format that can be
used to format between fixed width or delimited text messages to a List of
rows as Map.
▪ marshal = from List<Map<String, Object>> to OutputStream (can
be converted to String)
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
594
▪ unmarshal = from java.io.InputStream (such as a File or String)
to a java.util.List as an
org.apache.camel.component.flatpack.DataSetList instance.
The result of the operation will contain all the data. If you need to
process each row one by one you can split the exchange, using
Splitter.
Notice: The Flatpack library does currently not support header and trailers
for the marshal operation.
Options
The data format has the following options:
Option
Default
Description
definition
null
The flatpack pzmap configuration file.
Can be omitted in simpler situations, but
its preferred to use the pzmap.
fixed
false
Delimited or fixed.
ignoreFirstRecord
true
Whether the first line is ignored for
delimited files (for the column headers).
textQualifier
"
If the text is qualified with a char such as
".
delimiter
,
The delimiter char (could be ; , or
similar)
parserFactory
null
Uses the default Flatpack parser factory.
Usage
To use the data format, simply instantiate an instance and invoke the
marhsal or unmarshal operation in the route builder:
FlatpackDataFormat fp = new FlatpackDataFormat();
fp.setDefinition(new ClassPathResource("INVENTORY-Delimited.pzmap.xml"));
...
from("file:order/in").unmarshal(df).to("seda:queue:neworder");
The sample above will read files from the order/in folder and unmarshal the
input using the Flatpack configuration file INVENTORY-Delimited.pzmap.xml
that configures the structure of the files. The result is a DataSetList object
we store on the SEDA queue.
595
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
FlatpackDataFormat df = new FlatpackDataFormat();
df.setDefinition(new ClassPathResource("PEOPLE-FixedLength.pzmap.xml"));
df.setFixed(true);
df.setIgnoreFirstRecord(false);
from("seda:people").marshal(df).convertBodyTo(String.class).to("jms:queue:people");
In the code above we marshal the data from a Object representation as a
List of rows as Maps. The rows as Map contains the column name as the key,
and the the corresponding value. This structure can be created in Java code
from e.g. a processor. We marshal the data according to the Flatpack format
and convert the result as a String object and store it on a JMS queue.
Dependencies
To use Flatpack in your camel routes you need to add the a dependency on
camel-flatpack which implements this data format.
If you use maven you could just add the following to your pom.xml,
substituting the version number for the latest & greatest release (see the
download page for the latest versions).
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-flatpack</artifactId>
<version>1.5.0</version>
</dependency>
See Also
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
FREEMARKER
Available as of Camel 1.6
The freemarker: component allows you to process a message using a
FreeMarker template. This can be ideal when using Templating to generate
responses for requests.
Maven users will need to add the following dependency to their pom.xml
for this component:
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
596
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-freemarker</artifactId>
<version>x.x.x</version> <!-- use the same version as your Camel core version -->
</dependency>
URI format
freemarker:templateName[?options]
Where templateName is the classpath-local URI of the template to invoke;
or the complete URL of the remote template (eg: file://folder/myfile.ftl).
You can append query options to the URI in the following format,
?option=value&option=value&...
Options
Option
Default
Description
contentCache
true
Cache for the resource content when its loaded.
encoding
null
Character encoding of the resource content.
Headers
Headers set during the FreeMarker evaluation are returned to the message
and added as headers. Then its kinda possible to return values from
FreeMarker to the Message.
An example: Set the header value of fruit in the FreeMarker template:
${request.setHeader('fruit', 'Apple')}
The header, fruit, is now accessible from the message.out.headers.
FreeMarker Context
Camel will provide exchange information in the FreeMarker context (just a
Map). The Exchange is transfered as:
597
key
value
exchange
The Exchange itself.
headers
The headers of the In message.
camelContext
The Camel Context.
request
The In message.
body
The In message body.
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
response
The Out message (only for InOut message exchange pattern).
Hot reloading
The FreeMarker template resource is by default not hot reloadable for both
file and classpath resources (expanded jar). If you set contentCache=false,
then Camel will not cache the resource and hot reloading is thus enabled.
This scenario can be used in development.
Dynamic templates
Camel provides two headers by which you can define a different resource
location for a template or the template content itself. If any of these headers
is set then Camel uses this over the endpoint configured resource. This
allows you to provide a dynamic template at runtime.
Header
Type
Description
Support
Version
FreemarkerConstants.FREEMARKER_RESOURCE
org.springframework.core.io.Resource
The template resource
<= 1.6.2, <=
2.1
FreemarkerConstants.FREEMARKER_RESOURCE_URI
String
A URI for the template resource
to use instead of the endpoint
configured.
>= 2.1
FreemarkerConstants.FREEMARKER_TEMPLATE
String
The template to use instead of
the endpoint configured.
>= 2.1
Samples
For example you could use something like:
from("activemq:My.Queue").
to("freemarker:com/acme/MyResponse.ftl");
To use a FreeMarker template to formulate a response for a message for
InOut message exchanges (where there is a JMSReplyTo header).
If you want to use InOnly and consume the message and send it to
another destination you could use:
from("activemq:My.Queue").
to("freemarker:com/acme/MyResponse.ftl").
to("activemq:Another.Queue");
And to disable the content cache, e.g. for development usage where the
.ftl template should be hot reloaded:
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
598
from("activemq:My.Queue").
to("freemarker:com/acme/MyResponse.ftl?contentCache=false").
to("activemq:Another.Queue");
And a file-based resource:
from("activemq:My.Queue").
to("freemarker:file://myfolder/MyResponse.ftl?contentCache=false").
to("activemq:Another.Queue");
In Camel 2.1 it's possible to specify what template the component should
use dynamically via a header, so for example:
from("direct:in").
setHeader(FreemarkerConstants.FREEMARKER_RESOURCE_URI).constant("path/to/my/
template.ftl").
to("freemarker:dummy");
The Email Sample
In this sample we want to use FreeMarker templating for an order
confirmation email. The email template is laid out in FreeMarker as:
Dear ${headers.lastName}, ${headers.firstName}
Thanks for the order of ${headers.item}.
Regards Camel Riders Bookstore
${body}
And the java code:
private Exchange createLetter() {
Exchange exchange = context.getEndpoint("direct:a").createExchange();
Message msg = exchange.getIn();
msg.setHeader("firstName", "Claus");
msg.setHeader("lastName", "Ibsen");
msg.setHeader("item", "Camel in Action");
msg.setBody("PS: Next beer is on me, James");
return exchange;
}
@Test
public void testFreemarkerLetter() throws Exception {
MockEndpoint mock = getMockEndpoint("mock:result");
599
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
mock.expectedMessageCount(1);
mock.expectedBodiesReceived("Dear Ibsen, Claus\n\nThanks for the order of Camel
in Action."
+ "\n\nRegards Camel Riders Bookstore\nPS: Next beer is on me, James");
template.send("direct:a", createLetter());
mock.assertIsSatisfied();
}
protected RouteBuilder createRouteBuilder() throws Exception {
return new RouteBuilder() {
public void configure() throws Exception {
from("direct:a")
.to("freemarker:org/apache/camel/component/freemarker/letter.ftl")
.to("mock:result");
}
};
}
See Also
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
FTP/SFTP/FTPS COMPONENT - CAMEL 2.0 ONWARDS
This component provides access to remote file systems over the FTP and
SFTP protocols.
Maven users will need to add the following dependency to their pom.xml
for this component:
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-ftp</artifactId>
<version>x.x.x</version>
<!-- use the same version as your Camel core version -->
</dependency>
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
600
Using Camel 1.x
If you are using Camel 1.x then see this link for documentation.
This page is only for Camel 2.0 or newer.
Using FTPS
The FTPS component is only available in Camel 2.2 or newer.
FTPS (also known as FTP Secure) is an extension to FTP that adds
support for the Transport Layer Security (TLS) and the Secure
Sockets Layer (SSL) cryptographic protocols.
Libraries used
This component uses two different libraries for the actual FTP work.
FTP and FTPS uses Apache Commons Net while SFTP uses JCraft
JSCH.
URI format
ftp://[username@]hostname[:port]/directoryname[?options]
sftp://[username@]hostname[:port]/directoryname[?options]
ftps://[username@]hostname[:port]/directoryname[?options]
Where directoryname represents the underlying directory. Can contain
nested folders.
If no username is provided, then anonymous login is attempted using no
password.
If no port number is provided, Camel will provide default values according to
the protocol (ftp = 21, sftp = 22, ftps = 2222).
You can append query options to the URI in the following format,
?option=value&option=value&...
URI Options
The options below are exclusive for the FTP2 component.
601
Name
Default
Value
Description
username
null
Specifies the username to use to log in to the remote file systen.
password
null
Specifies the password to use to log in to the remote file system.
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
binary
false
Specifies the file transfer mode, BINARY or ASCII. Default is ASCII (false).
disconnect
false
Camel 2.2: Whether or not to disconnect from remote FTP server right after use. Can
be used for both consumer and producer. Disconnect will only disconnect the current
connection to the FTP server. If you have a consumer which you want to stop, then you
need to stop the consumer/route instead.
localWorkDirectory
null
When consuming, a local work directory can be used to store the remote file content
directly in local files, to avoid loading the content into memory. This is beneficial, if you
consume a very big remote file and thus can conserve memory. See below for more
details.
passiveMode
false
FTP and FTPS only: Specifies whether to use passive mode connections. Default is
active mode (false).
securityProtocol
TLS
FTPS only: Sets the underlying security protocol. The following values are defined:
TLS: Transport Layer Security
SSL: Secure Sockets Layer
disableSecureDataChannelDefaults
false
Camel 2.4: FTPS only: Whether or not to disable using default values for execPbsz
and execProt when using secure data transfer. You can set this option to true if you
want to be in absolute full control what the options execPbsz and execProt should be
used.
execProt
null
Camel 2.4: FTPS only: Will by default use option P if secure data channel defaults
hasn't been disabled. Possible values are:
C: Clear
S: Safe (SSL protocol only)
E: Confidential (SSL protocol only)
P: Private
execPbsz
null
Camel 2.4: FTPS only: This option specifies the buffer size of the secure data
channel. If option useSecureDataChannel has been enabled and this option has not
been explicit set, then value 0 is used.
isImplicit
false
FTPS only: Sets the security mode(implicit/explicit). Default is explicit (false).
knownHostsFile
null
SFTP only: Sets the known_hosts file, so that the SFTP endpoint can do host key
verification.
privateKeyFile
null
SFTP only: Set the private key file to that the SFTP endpoint can do private key
verification.
privateKeyFilePassphrase
null
SFTP only: Set the private key file passphrase to that the SFTP endpoint can do
private key verification.
strictHostKeyChecking
no
SFTP only: Camel 2.2: Sets whether to use strict host key checking. Possible values
are: no, yes and ask. ask does not make sense to use as Camel cannot answer the
question for you as its meant for human intervention. Note: The default in Camel 2.1
and below was ask.
maximumReconnectAttempts
3
Specifies the maximum reconnect attempts Camel performs when it tries to connect to
the remote FTP server. Use 0 to disable this behavior.
reconnectDelay
1000
Delay in millis Camel will wait before performing a reconnect attempt.
connectTimeout
10000
Camel 2.4: Is the connect timeout in millis. This corresponds to using
ftpClient.connectTimeout for the FTP/FTPS. For SFTP this option is also used when
attempting to connect.
soTimeout
null
FTP and FTPS Only: Camel 2.4: Is the SocketOptions.SO_TIMEOUT value in millis.
Note SFTP will automatic use the connectTimeout as the soTimeout.
timeout
30000
FTP and FTPS Only: Camel 2.4: Is the data timeout in millis. This corresponds to
using ftpClient.dataTimeout for the FTP/FTPS. For SFTP there is no data timeout.
throwExceptionOnConnectFailed
false
Camel 2.5: Whether or not to thrown an exception if a successful connection and
login could not be establish. This allows a custom pollStrategy to deal with the
exception, for example to stop the consumer or the likes.
siteCommand
null
FTP and FTPS Only: Camel 2.5: To execute site commands after successful login.
Multiple site commands can be separated using a new line character (\n). Use help
site to see which site commands your FTP server supports.
stepwise
true
Camel 2.6: Whether or not stepwise traversing directories should be used or not.
Stepwise means that it will CD one directory at a time. See more details below. You can
disable this in case you can't use this approach.
separator
Auto
Camel 2.6: Dictates what path separator char to use when uploading files. Auto =
Use the path provided without altering it. UNIX = Use unix style path separators.
Windows = Use Windows style path separators.
ftpClient
null
FTP and FTPS Only: Camel 2.1: Allows you to use a custom
org.apache.commons.net.ftp.FTPClient instance.
ftpClientConfig
null
FTP and FTPS Only: Camel 2.1: Allows you to use a custom
org.apache.commons.net.ftp.FTPClientConfig instance.
serverAliveInterval
0
SFTP Only: Camel 2.8 Allows you to set the serverAliveInterval of the sftp session
{{serverAliveCountMax }}
1
SFTP Only: Camel 2.8 Allows you to set the serverAliveCountMax of the sftp session
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
602
ftpClient.trustStore.file
null
FTPS Only: Sets the trust store file, so that the FTPS client can look up for trusted
certificates.
ftpClient.trustStore.type
JKS
FTPS Only: Sets the trust store type.
ftpClient.trustStore.algorithm
SunX509
FTPS Only: Sets the trust store algorithm.
ftpClient.trustStore.password
null
FTPS Only: Sets the trust store password.
ftpClient.keyStore.file
null
FTPS Only: Sets the key store file, so that the FTPS client can look up for the private
certificate.
ftpClient.keyStore.type
JKS
FTPS Only: Sets the key store type.
ftpClient.keyStore.algorithm
SunX509
FTPS Only: Sets the key store algorithm.
ftpClient.keyStore.password
null
FTPS Only: Sets the key store password.
ftpClient.keyStore.keyPassword
null
FTPS Only: Sets the private key password.
You can configure additional options on the ftpClient and ftpClientConfig
from the URI directly by using the ftpClient. or ftpClientConfig. prefix.
For example to set the setDataTimeout on the FTPClient to 30 seconds
you can do:
from("ftp://foo@myserver?password=secret&ftpClient.dataTimeout=30000").to("bean:foo");
You can mix and match and have use both prefixes, for example to configure
date format or timezones.
from("ftp://foo@myserver?password=secret&ftpClient.dataTimeout=30000&ftpClientConfig.serverLanguageCod
You can have as many of these options as you like.
See the documentation of the Apache Commons FTP FTPClientConfig for
possible options and more details.
And as well for Apache Commons FTP FTPClient.
If you do not like having many and long configuration in the url you can
refer to the ftpClient or ftpClientConfig to use by letting Camel lookup in
the Registry for it.
For example:
<bean id="myConfig" class="org.apache.commons.net.ftp.FTPClientConfig">
<property name="lenientFutureDates" value="true"/>
<property name="serverLanguageCode" value="fr"/>
</bean>
And then let Camel lookup this bean when you use the # notation in the url.
from("ftp://foo@myserver?password=secret&ftpClientConfig=#myConfig").to("bean:foo");
More URI options
603
CH AP T E R 11 - C OM P ON E N T A P P E N DIX
FTPS component default trust store
By default, the FTPS component trust store accept all certificates. If
you only want trust selective certificates, you have to configure the
trust store with the ftpClient.trustStore.xxx options or by
configuring a custom ftpClient.
See File2 as all the options there also applies for this component.
Stepwise changing directories
Camel FTP can operate in two modes in terms of traversing directories when
consuming files (eg downloading) or producing files (eg uploading)
▪ stepwise
▪ not stepwise
You may want to pick either one depending on your situation and security
issues. Some Camel end users can only download files if they use stepwise,
while others can only download if they do not. At least you have the choice to
pick (from Camel 2.6 onwards).
In Came 2.0 - 2.5 there is only one mode and it is:
▪ 2.0 to 2.4 not stepwise
▪ 2.5 stepwise
From Camel 2.6 onwards there is now an option stepwise you can use to
control the behavior.
Note that stepwise changing of directory will in most cases only work
when the user is confined to it's home directory and when the home
directory is reported as "/".
The difference between the two of them is best illustrated with an
example. Suppose we have the following directory structure on the remote
FTP server we need to traverse and download files:
/
/one
/one/two
/one/two/sub-a
/one/two/sub-b
And that we have a file in each of sub-a (a.txt) and sub-b (b.txt) folder.
C H A P TE R 1 1 - C O M P O NE N T A PPE NDIX
604
Using stepwise=true (default mode)
TYPE A
200 Type set to A
PWD
257 "/" is current directory.
CWD one
250 CWD successful. "/one" is current directory.
CWD two
250 CWD successful. "/one/tw