Camel Manual 1.6.1

Apache Camel
USER GUIDE
Version 1.6.1
Copyright 2007-2009, Apache Software Foundation
Table of Contents
Table of Contents......................................................................... ii
Chapter 1
Introduction ...................................................................................1
Chapter 2
Quickstart .......................................................................................1
Chapter 3
Getting Started..............................................................................6
Chapter 4
Architecture ................................................................................ 16
Chapter 5
Enterprise Integration Patterns.............................................. 23
Chapter 6
Cook Book ................................................................................... 28
Chapter 7
Tutorials....................................................................................... 76
Chapter 8
Language Appendix.................................................................. 174
Chapter 9
Pattern Appendix..................................................................... 210
Chapter 10
Component Appendix ............................................................. 270
Index ................................................................................................0
ii
AP A C H E C A M 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-of-the-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!
CH APT ER 1 - IN T R O DUCT IO 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:
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
1
CH A PTE R 2 - Q U I CKS T A R T
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.
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
CH APT ER 2 - Q UICK ST AR T
2
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();
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>
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
3
CH A PTE R 2 - Q U I CKS T A R T
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 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.
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
CH APT ER 2 - Q UICK ST AR T
4
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>
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
5
CH A PTE R 2 - Q U I CKS T A R T
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. Some people refer
to this as the "gang of four" book, partly to distinguish this book from other books that use
"Design Patterns" in their titles and, perhaps, partly because they cannot remember the names
of all four authors.
Since the publication of Design Patterns, many other patterns 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 Woolfe. It is common for people to
refer to this book as EIP, which is an acronym of its title. As the subtitle of EIP suggests, the
book focusses 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. The
graphical symbols are intended to be used in architectural diagrams.
THE CAMEL PROJECT
Camel (http://activemq.apache.org/camel/) is an open-source, Java-based project that is a part of
the Apache ActiveMQ project. Camel provides a class library that, according to its
documentation, can be used to implement 31 design patterns in the EIP book. I am not sure
why the Camel documentation discusses only 31 of the 65 EIP design patterns. Perhaps this is
due to incomplete documentation. Or perhaps it means that the Camel project, which is less
than 1 year old at the time of writing, is not yet as feature rich as 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 read the EIP book.
C H A P T E R 3 - G ET T IN G ST AR T ED W IT H APACH E CAM EL
6
ONLINE DOCUMENTATION FOR CAMEL
The Camel project was started in early 2007. At the time of writing, the Camel project is too
young for there to be published books available on how to use Camel. Instead, the only source
of documentation seems to the documentation page on the Apache Camel website.
Problems with Camel's online documentation
Currently, the online documentation for the Apache Camel project suffers from two problems.
First, the documentation is incomplete. Second, there is no clearly specified reading order to
the documentation. For example, there is no table of contents. Instead, documentation is
fragmented over a collection of 60+ web pages, and hypertext links haphazardly tie these web
pages to each other. This documentation might suffice as reference material for people already
familiar with Camel but it does not qualify as a tutorial for beginners.
The problems with the documentation are unlikely to be due to, say, its author(s) lacking
writing ability. Rather, it is more likely that the problems are due to the author(s) lack of time. I
expect Camel's documentation will improve over time. I am writing this overview of Camel to
partially counter some of the problems that currently afflict the Camel documentation. In
particular, this document aims to serve as a (so far, incomplete) "beginner's guide to Camel". As
such, this document tries to complement, rather than compete with, the online Camel
documentation.
A useful tip for navigating the online documentation
There is one useful hint I can provide for reading the online Camel documentation. Each
documentation page has a logo at the top, and immediately underneath this is a think reddish
bar that contains some hypertext links. The Hypertext links on left side of this reddish bar
indicate your position in documentation. 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 "Architeture" and "Languages" buttons as indicating you are in the
"Languages" section of the "Architecture" chapter. Doing this gives you at least some sense of
where you are within the documentation. If you are patient then you can spend a few hours
clicking on all the hypertext links you can find in the documentation pages, bookmark each page
with a hierarchical name (for example, you might bookmark the above page with the name
"Camel – Arch – Languages") and then you can use your bookmarks to serve as a primitive
table of contents for the online Camel documentation.
7
CH A PTE R 3 - GE T T I NG S T A R T E D W I T H A PACH E CAM EL
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 communications 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, ActiveMQ API and FTP API.
CONCEPTS AND TERMINOLOGY FUNDAMENTAL TO CAMEL
I said in Section 3.1 ("Problems with Camel's online documentation") that the online Camel
documentation does not provide a tutorial for beginners. Because of this, in this section I try to
explain some of the concepts and terminology that are fundamental to Camel. This section is
not a complete Camel tutorial, but it is a first step in that direction.
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.
C H A P T E R 3 - G ET T IN G ST AR T ED W IT H APACH E CAM EL
8
•
•
•
•
•
•
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.
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 Camel-supported 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.
9
CH A PTE R 3 - GE T T I NG S T A R T E D W I T H A PACH E CAM EL
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.
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:<scheme-name>:<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 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"
C H A P T E R 3 - G ET T IN G ST AR T ED W IT H APACH E CAM EL
10
in these examples) part of a URN implicitly defines how to parse and interpret the
<unique-identifier> 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
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.
11
CH A PTE R 3 - GE T T I NG S T A R T E D W I T H A PACH E CAM EL
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 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:...");
C H A P T E R 3 - G ET T IN G ST AR T ED W IT H APACH E CAM EL
12
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.
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
13
CH A PTE R 3 - GE T T I NG S T A R T E D W I T H A PACH E CAM EL
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 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(),
C H A P T E R 3 - G ET T IN G ST AR T ED W IT H APACH E CAM EL
14
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 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.
15
CH A PTE R 3 - GE T T I NG S T A R T E D W I T H A PACH E CAM EL
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
• SQL
• XPath
CH APT ER 4 - AR CH IT ECT UR E
16
• 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
ActiveMQ / activemq-camel
activemq:[topic:]destinationName
ActiveMQ Journal / activemq-core
activemq.journal:directory-on-filesystem
Description
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
Bean / camel-core
bean:beanName[?methodName=someMethod]
Browse / camel-core
browse:someName
Cometd / camel-cometd
cometd://host:port/channelname
CXF / camel-cxf
cxf:address[?serviceClass=...]
17
CH A PTE R 4 - AR 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.
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).
Provdes 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.
Used to deliver messages using the jetty
cometd implementation of the bayeux
protocol
Working with Apache CXF for web
services integration
DataSet / camel-core
dataset:name
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
Direct / camel-core
direct:name
Esper / camel-esper in camel-extra
esper:name
Synchronous call to another endpoint
Working with the Esper Library for
Event Stream Processing
Event / camel-spring
event://default
spring-event://default
File / camel-core
file://nameOfFileOrDirectory
FIX / camel-fix in FUSE
fix://configurationResource
Flatpack / camel-flatpack
flatpack:[fixed|delim]:configFile
Freemarker / camel-freemarker
freemarker:someTemplateResource
Working with Spring ApplicationEvents
Sending messages to a file or polling a
file or directory
Sends or receives messages using the
FIX protocol
Processing fixed width or delimited files
or messages using the FlatPack library
Generates a response using a
Freemarker template
FTP / camel-ftp
ftp://host[:port]/fileName
Hibernate / camel-hibernate in camel-extra
hibernate://entityName
HL7 / camel-hl7
mina:tcp://hostname[:port]
Sending and receiving files over FTP
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
HTTP / camel-http
http://hostname[:port]
For calling out to external HTTP servers
CH APT ER 4 - AR CH IT ECT UR E
18
iBATIS / camel-ibatis
ibatis://sqlOperationName
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 in FUSE
javaspace:jini://host?spaceName=mySpace?...
JBI / servicemix-camel
jbi:serviceName
JCR / camel-jcr
jcr://user:password@repository/path/to/node
JDBC / camel-jdbc
jdbc:dataSourceName?options
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
For performing JDBC queries and
operations
Jetty / camel-jetty
jetty:url
For exposing services over HTTP
JMS / camel-jms
jms:[topic:]destinationName
JPA / camel-jpa
jpa://entityName
JT/400 / camel-jt400
jt400://user:pwd@system/<path_to_dtaq>
LDAP / camel-ldap
ldap:host[:port]?base=...[&scope=<scope>]
19
CH A PTE R 4 - AR C H I T E C T U R E
Working with JMS providers
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
Performing searches on LDAP servers
(<scope> must be one of
object|onelevel|subtree)
List / camel-core
list:someName
Log / camel-core
log:loggingCategory[?level=ERROR]
deprecated Provdes 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.
Uses Jakarta Commons Logging to log
the message exchange to some
underlying logging system like log4j
Mail / camel-mail
mail://user-info@host:port
Sending and receiving email
MINA / camel-mina
[tcp|udp|multicast]:host[:port]
Mock / camel-core
mock:name
MSMQ / camel-msmq in FUSE
msmq:msmqQueueName
MSV / camel-msv
msv:someLocalOrRemoteResource
Multicast / camel-mina
multicast://host:port
Pojo / camel-core
pojo:name
Working with Apache MINA
For testing routes and mediation rules
using mocks
Sending and receiving messages with
Microsoft Message Queuing
Validates the payload of a message using
the MSV Library
Working with TCP protocols using
Apache MINA
Deprecated. It is now an alias to the
Bean component.
POP / camel-mail
pop3://user-info@host:port
Quartz / camel-quartz
quartz://groupName/timerName
Queue / camel-core
queue:name
Receiving email using POP3 and JavaMail
Provides a scheduled delivery of
messages using the Quartz scheduler
Deprecated. It is now an alias to the
SEDA component.
CH APT ER 4 - AR CH IT ECT UR E
20
Ref / camel-core
ref:name
Restlet / camel-restlet
restlet:restletUrl[?options]
Component for lookup of existing
endpoints bound in the Registry.
Component for consuming and
producing Restful resources using
Restlet
RMI / camel-rmi
rmi://host[:port]
RNC / camel-jing
rnc:/relativeOrAbsoluteUri
RNG / camel-jing
rng:/relativeOrAbsoluteUri
RSS / camel-rss
rss:uri
SEDA / camel-core
seda:name
Working with RMI
Validates the payload of a message using
RelaxNG Compact Syntax
Validates the payload of a message using
RelaxNG
Working with ROME for RSS
integration, such as consuming an RSS
feed.
Asynchronous call to another endpoint
in the same Camel Context
SFTP / camel-ftp
sftp://host[:port]/fileName
Smooks / camel-smooks in camel-extra
unmarshal(edi)
Sending and receiving files over SFTP
For working with EDI parsing using the
Smooks library
SMTP / camel-mail
smtp://user-info@host[:port]
SpringIntegration / camel-spring-integration
spring-integration:defaultChannelName
Sending email using SMTP and JavaMail
The bridge component of Camel and
Spring Integration
SQL / camel-sql
sql:select * from table where id=#
Stream / camel-stream
stream:[in|out|err|file]
21
CH A PTE R 4 - AR C H I T E C T U R E
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
TCP / camel-mina
tcp://host:port
Test / camel-spring
test:expectedMessagesEndpointUri
Generates a response using a String
Template
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
UDP / camel-mina
udp://host:port
Validation / camel-spring
validation:someLocalOrRemoteResource
Velocity / camel-velocity
velocity:someTemplateResource
VM / camel-core
vm:name
A timer endpoint
Working with UDP protocols using
Apache MINA
Validates the payload of a message using
XML Schema and JAXP Validation
Generates a response using an Apache
Velocity template
Asynchronous call to another endpoint
in the same JVM
XMPP / camel-xmpp
xmpp://host:port/room
XQuery / camel-saxon
xquery:someXQueryResource
XSLT / camel-spring
xslt:someTemplateResource
Working with XMPP and Jabber
Generates a response using an XQuery
template
Generates a response using an XSLT
template
For a full details of the individual components see the Component Appendix
CH APT ER 4 - AR CH IT ECT UR E
22
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
23
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 A PTE R 5 - E N T E R P R I SE I NT E G R A T I ON P AT T ER 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?
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?
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?
CH A P T E R 5 - EN T ER PR ISE IN T EGR AT IO N PAT T ER N S
24
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-of-sequence
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?
Scatter-Gather
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?
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?
Loop
How can I repeat processing a message in a loop?
Message Transformation
25
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?
CH A PTE R 5 - E N T E R P R I SE I NT E G R A T I ON P AT T ER N S
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?
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?
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?
CH A P T E R 5 - EN T ER PR ISE IN T EGR AT IO N PAT T ER N S
26
Wire
Tap
How do you inspect messages that travel on a point-to-point
channel?
For a full breakdown of each pattern see the Book Pattern Appendix
27
CH A PTE R 5 - E N T E R P R I SE I NT E G R A T I ON P AT T ER 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
• 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.
CO O K B O O K
28
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
• RecipientList Annotation for creating a Recipient List from 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.
29
COO K BO O K
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
@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:
CO O K B O O K
30
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;
}
}
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.MyIdGenerator"/>
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) {
31
COO K BO O K
// process the inbound message here
}
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
• the method name can be specified explicitly in the DSL or when using POJO
Consuming
• 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
• 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
• 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.
By default the return value is set on the outbound message body.
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:
CO O K B O O K
32
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:
public class Bar {
public void doSomething(Exchange exchange) {
// process the exchange
exchange.getIn().setBody("Bye World");
}
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.
33
COO K BO O K
@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
The core annotations are as follows
Annotation
Meaning
@Body
To bind to an inbound message body
@ExchangeException
To bind to an Exception set on the
exchange (Camel 2.0)
@Header
To bind to an inbound message header
@Headers
To bind to the Map of the inbound message
headers
@OutHeaders
To bind to the Map of the outbound
message headers
@Property
To bind to a named property on the
exchange
@Properties
To bind to the property map on the
exchange
Parameter
String name of the
header
String name of the
property
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
CO O K B O O K
34
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 @MessageDriven consumer 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 {
@MessageDriven(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 @MessageDriven 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
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
35
COO K BO O K
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:
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
@Ruby
Inject a Ruby expression
@Simple
Inject an Simple expression
@XPath
Inject an XPath expression
@XQuery
Inject an XQuery expression
Example:
public class Foo {
CO O K B O O K
36
@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;
}
}
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:
37
COO K BO O K
<bean id="myCorrelationIdGenerator" class="com.mycompany.MyIdGenerator"/>
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
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 {
@MessageDriven(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 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
CO O K B O O K
38
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/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
@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.
39
COO K BO O K
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 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="
CO O K B O O K
40
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.
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.
41
COO K BO O K
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;
}
}
public class MyRouteBuilder extends RouteBuilder {
protected void configure() {
from("activemq:Orders.Incoming").beanRef("myRouterBean", "route");
}
}
Notice how we are injecting some headers or expressions and using them to determine the
recipients. 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);
}
CO O K B O O K
42
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.
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
43
COO K BO O K
@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
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.
CO O K B O O K
44
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.
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!
45
COO K BO O K
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.
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
CO O K B O O K
46
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.
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 ran 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
• that the correct payloads are received, in the right order
• that messages arrive on an endpoint in order, using some Expression to create an
order testing function
47
COO K BO O K
• that 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 also uses a
second endpoint to provide the list of expected message bodies and automatically sets up the
Mock endpoint assertions. i.e. its a Mock endpoint which 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 to uniquely identify the endpoint
Options
Option
Default
Description
reportGroup
null
A size to use a throughput logger for reporting
Simple Example
Here's a simple example of MockEndpoint in use. First the endpoint is resolved on the context.
Then we set an expectation, then after the test has run we assert our expectations are 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 20 seconds when the assertIsSatisfied() is invoked. This
can be configured by setting the setResultWaitTime(millis) method.
Setting expectations
You can see from the javadoc of MockEndpoint the various helper methods you can use to set
expectations. The main methods available are as follows:
Method
Description
CO O K B O O K
48
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 this code
resultEndpoint.message(0).header("foo").isEqualTo("bar");
There are some examples of the Mock endpoint in use in the camel-core processor tests.
A Spring Example
First here's the spring.xml file
<camelContext xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="file:src/test/data?noop=true"/>
49
COO K BO O K
<filter>
<xpath>/person/city = 'London'</xpath>
<to uri="mock:matched"/>
</filter>
</route>
</camelContext>
<bean id="myBean" class="org.apache.camel.spring.mock.MyAssertions" scope="singleton"/>
As you can see it defines a simple routing rule which consumes messages from the local src/
test/data directory. The noop flag just means not to delete or move the file after its been
processed.
Also note we instantiate a bean called myBean, here is the source of the MyAssertions
bean.
public class MyAssertions implements InitializingBean {
@EndpointInject(uri = "mock:matched")
private MockEndpoint matched;
@EndpointInject(uri = "mock:notMatched")
private MockEndpoint notMatched;
public void afterPropertiesSet() throws Exception {
// lets add some expectations
matched.expectedMessageCount(1);
notMatched.expectedMessageCount(0);
}
public void assertEndpointsValid() throws Exception {
// now lets perform some assertions that the test worked as we expect
Assert.assertNotNull("Should have a matched endpoint", matched);
Assert.assertNotNull("Should have a notMatched endpoint", notMatched);
MockEndpoint.assertIsSatisfied(matched, notMatched);
}
}
The bean is injected with a bunch of Mock endpoints using the @EndpointInject annotation, it
then sets a bunch of expectations on startup (using Spring's InitializingBean interface and
afterPropertiesSet() method) before the CamelContext starts up.
Then in our test case (which could be JUnit or TesNG) we lookup myBean in Spring (or
have it injected into our test) and then invoke the assertEndpointsValid() method on it to
verify that the mock endpoints have their assertions met. You could then inspect the message
exchanges that were delivered to any of the endpoints using the getReceivedExchanges()
method on the Mock endpoint and perform further assertions or debug logging.
Here is the actual JUnit test case we use.
See Also
• Configuring Camel
• Component
CO O K B O O K
50
• Endpoint
• Getting Started
• Spring 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.
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 {
51
COO K BO O K
String expectedBody = "<matched/>";
resultEndpoint.expectedBodiesReceived(expectedBody);
template.sendBodyAndHeader(expectedBody, "foo", "bar");
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");
CO O K B O O K
52
resultEndpoint.assertIsSatisfied();
}
@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-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="direct:start"/>
<filter>
<xpath>$foo = 'bar'</xpath>
<to uri="mock:result"/>
</filter>
</route>
</camelContext>
</beans>
Spring Test with Java Config Example
Here is the Spring Testing example using Java Config. For more information see Spring Java
Config.
@ContextConfiguration(
locations =
"org.apache.camel.spring.javaconfig.patterns.FilterTest$ContextConfig",
loader = JavaConfigContextLoader.class)
53
COO K BO O K
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();
}
@DirtiesContext
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.
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.
CO O K B O O K
54
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
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
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-test</artifactId>
<version>${camel-version}</version>
55
COO K BO O K
<scope>test</scope>
</dependency>
You might also want to add commons-logging and log4j to ensure nice logging messages (and
maybe adding a log4j.properties file into your src/test/resources directory).
<dependency>
<groupId>commons-logging</groupId>
<artifactId>commons-logging</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");
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() {
CO O K B O O K
56
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
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;
57
COO K BO O K
public void testMocksAreValid() throws Exception {
MockEndpoint.assertIsSatisfied(camelContext);
}
}
This test will load a Spring XML configuration file called MyCamelTest-context.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.
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 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();
CO O K B O O K
58
}
@DirtiesContext
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");
MockEndpoint.assertIsSatisfied(camelContext);
}
}
59
COO K BO O K
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 @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")
CO O K B O O K
60
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
• 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.
61
COO K BO O K
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.
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.
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 {
CO O K B O O K
62
@Provides
@JndiBind("foo")
Collection<RouteBuilder> foo(@Named("fooUrl") String fooUrl) {
return Lists.newArrayList(new MyRouteBuilder(fooUrl), new
MyRouteBuilder("activemq:CheeseQueue"));
}
}
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
• 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");
63
COO K BO O K
See Also
• Mock for details of mock endpoint testing (as opposed to template based stubs).
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
CO O K B O O K
64
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 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 messages which should be processed
65
COO K BO O K
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.
Interface Details
public interface AsyncProcessor extends Processor {
boolean process(Exchange exchange, AsyncCallback callback);
}
CO O K B O O K
66
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);
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 {
67
COO K BO O K
... // 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.
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:
CO O K B O O K
68
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.
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:
69
COO K BO O K
You would actually have multiple threads executing the 2nd part of the thread sequence.
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
CO O K B O O K
70
• 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 "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" />
<property name="transportIds">
<list>
<value>http://cxf.apache.org/transports/camel</value>
</list>
</property>
</bean>
71
COO K BO O K
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.
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 4. 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
...>
CO O K B O O K
72
The destination element
You configure an Camel transport server endpoint using the camel:destination element
and its children. The camel:destination 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 5. 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
camel-spring: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 6. http-conf:conduit Element
...
<camelContext id="conduit_context" xmlns="http://activemq.apache.org/camel/schema/
73
COO K BO O K
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
camel-spring: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-2.5.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
">
<bean id = "roundRobinRef"
class="org.apache.camel.processor.loadbalancer.RoundRobinLoadBalancer" />
CO O K B O O K
74
<camelContext id="dest_context" xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="jetty:http://localhost:9090/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
Better JMS Transport for CXF Webservice using Apache Camel
75
COO K BO O K
Tutorials
There now follows the documentation on camel tutorials
• Tutorial on Spring Remoting with JMS
This tutorial is focused on different techniques with Camel for Client-Server
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 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 22/04/2009
The focus of this Tutorial is to introduce you how you can create, design a simple
SOA solution using Camel and OSGI and deploy it in a OSGI Server like ServiceMix
Kernel and Spring DM Server. The tutorial has been designed in two parts. The first
part introduces basic concept 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.
T UT O R IALS
76
• Examples
While not actual tutorials you might find working through the source of the various
Examples useful
TUTORIAL ON SPRING REMOTING WITH JMS
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.
•
• Preface
• Prerequisites
• Distribution
• About
• Create the Camel Project
• Update the POM with Dependencies
• Writing the Server
• Create the Spring Service
• Define the Camel Routes
• 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.
77
TU TO RI A L S
Thanks
This tutorial was kindly donated to Apache Camel by Martin Gilday.
DISTRIBUTION
This sample is distributed with the Camel distribution as examples/
camel-example-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
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
T UT O R IALS
78
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
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>${spring-version}</version>
79
TU TO RI A L S
For the purposes of the tutorial a single Maven project will be used for both the client and
server. Ideally you would break your application down into the appropriate components.
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-aop</artifactId>
<version>${spring-version}</version>
</dependency>
<dependency>
<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 {
T UT O R IALS
80
public int multiply(final int originalNumber) {
return originalNumber * 3;
}
}
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");
// the STOP command
from("jms:queue:stop").to("shutdown");
}
}
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.
81
TU TO RI A L S
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 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-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
http://activemq.apache.org/schema/core http://activemq.apache.org/schema/core/
activemq-core-5.2.0.xsd">
We use Spring annotations for doing IoC dependencies and its component-scan 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">
<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
61616.
<!-- lets configure the ActiveMQ JMS broker server to listen on TCP 61616 -->
<broker:broker useJmx="false" persistent="false" brokerName="localhost">
<broker:transportConnectors>
<broker:transportConnector name="tcp" uri="tcp://localhost:61616"/>
</broker:transportConnectors>
</broker:broker>
T UT O R IALS
82
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:61616"/>
</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.
component-scan
Defines the package to be scanned for Spring stereotype annotations, in
this case, to load the "multiplier" bean
camel-context
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"
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/
schema/beans/spring-beans-2.5.xsd
http://www.springframework.org/schema/aop http://www.springframework.org/
schema/aop/spring-aop-2.5.xsd
http://camel.apache.org/schema/spring http://camel.apache.org/schema/spring/
camel-spring.xsd">
Then we include all the existing configuration from the normal server example:
<!-- import the normal server that is the JMS broker -->
<import resource="camel-server.xml"/>
Then we enable the AspejctJ AOP auto proxy feature of Spring that will scan for classes
annotated with the @Aspect annotation:
83
TU TO RI A L S
<!-- 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>
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.
<!-- the audit store endpoint is configued as file based -->
<camel:endpoint id="AuditStore" uri="file://target/store?append=false"/>
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 UT O R IALS
84
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-2.5.xsd
http://camel.apache.org/schema/spring http://camel.apache.org/schema/spring/
camel-spring.xsd">
<camel:camelContext id="camel"/>
<camel:template id="camelTemplate"/>
<!-- 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:61616"/>
</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
85
TU TO RI A L S
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.
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 -->
<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.
T UT O R IALS
86
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 invocing. 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);
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 non-trivial
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!
87
TU TO RI A L S
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");
// 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();
// 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:61616" 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
T UT O R IALS
88
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 7. pom.xml
<build>
<plugins>
<plugin>
<groupId>org.apache.camel</groupId>
<artifactId>camel-maven-plugin</artifactId>
</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
...
89
TU TO RI A L S
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
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 heavy-weight 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.
T UT O R IALS
90
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.
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
91
TU TO RI A L S
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
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:
T UT O R IALS
92
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.
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.
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/"
93
TU TO RI A L S
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"
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
T UT O R IALS
94
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 -->
<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>
95
TU TO RI A L S
<execution>
<id>generate-sources</id>
<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>
<load-on-startup>1</load-on-startup>
</servlet>
<!-- all our webservices are mapped under this URI pattern -->
<servlet-mapping>
<servlet-name>CXFServlet</servlet-name>
T UT O R IALS
96
<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 cxf-config.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/cxf-config.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"/>
<!-- 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"/>
97
TU TO RI A L S
</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 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;
}
T UT O R IALS
98
}
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>
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.
99
TU TO RI A L S
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.
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
T UT O R IALS
100
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:
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:
101
TU TO RI A L S
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 {
}
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:
T UT O R IALS
102
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
*
*/
/*
*
*/
@WebService(targetNamespace = "http://reportincident.example.camel.apache.org", name =
"ReportIncidentEndpoint")
@XmlSeeAlso({ObjectFactory.class})
@SOAPBinding(parameterStyle = SOAPBinding.ParameterStyle.BARE)
public interface ReportIncidentEndpoint {
/*
*
103
TU TO RI A L S
*/
@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();
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.
T UT O R IALS
104
<!-- 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
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
Date
tutorial_reportincident_part-one.zip
14
kb
Claus
Ibsen
Jul
17,
2008
LINKS
•
•
•
•
•
•
105
Introduction
Part 1
Part 2
Part 3
Part 4
Part 5
TU TO RI A L S
Comment
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.
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:
T UT O R IALS
106
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.
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.
public OutputReportIncident reportIncident(InputReportIncident parameters) {
String name = parameters.getGivenName() + " " + parameters.getFamilyName();
// let Camel do something with the name
sendToCamelLog(name);
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();
107
TU TO RI A L S
// 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();
} 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");
T UT O R IALS
108
// 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 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("");
109
TU TO RI A L S
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
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);
T UT O R IALS
110
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:
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
return sb.toString();
}
111
TU TO RI A L S
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.
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:
T UT O R IALS
112
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:
$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.
113
TU TO RI A L 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 took you through the
coding parts that requires 6 - 10 lines to send a message to an endpoint, buts it's important to
T UT O R IALS
114
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
Date
part-two.zip
17
kb
Claus
Ibsen
Jul
19,
2008
Comment
LINKS
•
•
•
•
•
•
Introduction
Part 1
Part 2
Part 3
Part 4
Part 5
PART 3
RECAP
Lets just recap on the solution we have now:
public class ReportIncidentEndpointImpl implements ReportIncidentEndpoint {
private CamelContext camel;
private ProducerTemplate template;
public ReportIncidentEndpointImpl() throws Exception {
115
TU TO RI A L S
// 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 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
T UT O R IALS
116
// 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 driven consumer
// the Processor is the code what should happen when there is an event
// (think it as the onMessage method)
Consumer consumer = endpint.createConsumer(new Processor() {
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
117
TU TO RI A L S
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.
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);
}
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
T UT O R IALS
118
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:
<!-- 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.
119
TU TO RI A L S
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.
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
T UT O R IALS
120
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:
// 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);
121
TU TO RI A L S
// 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());
}
}
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
•
Name
Size
Creator
Date
part-three.zip
18
kb
Claus
Ibsen
Jul
20,
2008
Comment
T UT O R IALS
122
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 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 {
123
TU TO RI A L S
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!
/**
* 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.
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
T UT O R IALS
124
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:
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
125
TU TO RI A L S
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.
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>
T UT O R IALS
126
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 {
}
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
127
TU TO RI A L 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.
by Claus Ibsen."));
}
/**
* Creates a dummy request to be used for input
*/
protected InputReportIncident createInput() {
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 UT O R IALS
128
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-claus-acer. 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-claus-acer\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:
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;
}
129
TU TO RI A L S
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
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
T UT O R IALS
130
// 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.
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;
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")
131
TU TO RI A L 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:
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");
}
T UT O R IALS
132
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.
// 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
•
133
TU TO RI A L S
Name
Size
Creator
Date
Comment
part-four.zip
11
kb
Claus
Ibsen
Aug
25,
2008
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 is possible but not really easy or nice. This article shows how
to use Apache Camel to provide a better JMS Transport for CXF.
You can find the original announcement for this Tutorial and some additional info on Christian
Schneider´s Blog
Why not simply use JMS Features of Apache CXF
JMS configuration in Apache CXF is possible but the configuration is not very flexible and quite
error prone. In CXF you have to configure a JMSConduit or a JMSDestination for each
webservice. The connection between Conduit and the Service proxy is the endpoint name
which looks like "{http://service.test\}HelloWorldPort.jms-conduit". As this name is never
explicitly configured elsewhere it is quite probable that you misspell the name. If this happens
then the JMS Transport just does not work. There is no good error reporting to show you
what you did wrong. The next thing is that you have to use JNDI for the connectionFactory and
the queue name. This is something that beginners with JMS have many problems with.
Why is using Apache Camel better in the JMS Transport layer
In Apache Camel you can simply reference the ConnectionFactory as a Spring bean. This means
you can either define it directly in a Spring bean what is the ideal way to start or you can use
Spring´s JNDI binding to retrieve it from your application server for production use.
The next nice thing is that you can configure all JMS options like receive timeout or username /
password in a central location, the JMSComponent and then share this config for several
services. On the other hand you can easily configure different JMS providers.
T UT O R IALS
134
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>
</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"
135
TU TO RI A L S
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 dramatically ease JMS configuration
compared with CXFs native JMS Transport. This is of course only a workaround. The CXF
team already works on the native JMS config for CXF to make it at least as good as Camel´s.
As CXF and Camel are two projects that have very good connections between them it is
perhaps even possible to have a common transport layer for CXF and camel.
TUTORIAL USING AXIS 1.4 WITH APACHE CAMEL
•
• 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
• Integrating Spring
• Using Spring
• Integrating Camel
T UT O R IALS
136
•
•
•
•
•
•
• 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.
Maven 2
Axis dependencies is available for maven 2 so we configure our pom.xml as:
137
TU TO RI A L S
<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>
<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>
T UT O R IALS
138
<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"
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>
139
TU TO RI A L S
<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 -->
<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>
T UT O R IALS
140
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
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
141
TU TO RI A L S
*/
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 server-config.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>
<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"/>
T UT O R IALS
142
</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"/>
</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.
143
TU TO RI A L S
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.
<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.
T UT O R IALS
144
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.
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
145
TU TO RI A L S
org.springframework.remoting.jaxrpc.ServletEndpointSupport so the
refactored code is:
package org.apache.camel.example.axis;
import
import
import
import
org.apache.camel.example.reportincident.InputReportIncident;
org.apache.camel.example.reportincident.OutputReportIncident;
org.apache.camel.example.reportincident.ReportIncidentService_PortType;
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);
}
}
T UT O R IALS
146
So now we have integrated Axis with Spring and we are ready for Camel.
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>
</beans>
147
TU TO RI A L 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.
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 end-user 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:
<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;
T UT O R IALS
148
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
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
149
TU TO RI A L S
/services to the URL to access the Axis frontpage. The URL should be
http://localhost:8080/camel-example-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>
<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");
T UT O R IALS
150
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:
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();
151
TU TO RI A L S
// 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();
// 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:
T UT O R IALS
152
@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>
<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 {
153
TU TO RI A L S
// 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:
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
T UT O R IALS
154
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.
@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 -->
155
TU TO RI A L S
<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.
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.
T UT O R IALS
156
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/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"
version="2.4">
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
</web-app>
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://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">
<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...
157
TU TO RI A L S
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
<build>
<plugins>
<plugin>
<groupId>org.mortbay.jetty</groupId>
<artifactId>maven-jetty-plugin</artifactId>
<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 UT O R IALS
158
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
• 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
159
TU TO RI A L S
• 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 UT O R IALS
160
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
• 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.
161
TU TO RI A L S
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 8. 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>
</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
T UT O R IALS
162
• 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.
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>
163
TU TO RI A L S
<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 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:
T UT O R IALS
164
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, if your test class was
org.apache.camel.tutorial.XMLInputTest, it would look for
org/apache/camel/tutorial/XMLInputTest-context.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();
165
TU TO RI A L S
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>
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 we're going to write a Camel route that applies the XSLT to the sample Customer 1
input file, and makes sure that some XML output comes out:
1. Save the input-customer1.xml file to src/test/resources
2. 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:
T UT O R IALS
166
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);
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
167
TU TO RI A L S
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.
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).
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
T UT O R IALS
168
5. Populate the partner ID, date of receipt, and order total on the Invoice
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 9. 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 10. 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:
169
TU TO RI A L S
<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
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.
T UT O R IALS
170
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>
<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
171
TU TO RI A L S
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.
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.
T UT O R IALS
172
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 commons-logging 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.
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
173
TU TO RI A L 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>
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.
LAN GUAGES SUPPO R T ED APPEN DIX
174
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:
from("activemq:topic:OrdersTopic").
filter().expression(bean(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 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(bean(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.
175
L A N G U A G E S S U P P OR T E D A P P E ND I X
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
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:
LAN GUAGES SUPPO R T ED APPEN DIX
176
<route>
<from uri="seda:foo"/>
<filter>
<el>${in.headers['My Header'] == 'bar'}</el>
<to uri="seda:bar"/>
</filter>
</route>
You could use EL to create an Predicate in a Message Filter or as an Expression for a Recipient
List
Variables
Variable
Type
Description
exchange
Exchange
the Exchange object
in
Message
the exchange.in message
out
Message
the exchange.out message
Samples
You can use EL dot notation to invoke operations. If you for instance have a body that contains
a POJO that has a getFamiliyName method then you can construct the syntax as follows:
"$in.body.familyName"
You have the full power of EL at your hand so you can invoke methods to for instance replace
text. In the sample below we replace the text in the body where id is replaced with orderId.
<from uri="seda:incomingOrders">
<setBody>
<el>${in.body.replaceAll('id','orderId')}</el>
</setBody>
<to uri="seda:processOrder"/>
And the sample using the Java DSL:
from("seda:incomingOrders").setBody().el("${in.body.replaceAll('id','orderId')}").to("seda:processOrde
Dependencies
To use EL in your camel routes you need to add the a dependency on camel-juel 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>
177
L A N G U A G E S S U P P OR T E D A P P E ND I X
<artifactId>camel-juel</artifactId>
<version>1.4.0</version>
</dependency>
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
from("queue:foo").filter().
jxpath("/in/body/foo").
to("queue:bar")
LAN GUAGES SUPPO R T ED APPEN DIX
178
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");
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 {
179
L A N G U A G E S S U P P OR T E D A P P E ND I X
@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>
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
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
LAN GUAGES SUPPO R T ED APPEN DIX
180
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>
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:
• BeanShell
• JavaScript
• Groovy
• Python
• PHP
• Ruby
181
L A N G U A G E S S U P P OR T E D A P P E ND I X
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");
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"/>
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.
LAN GUAGES SUPPO R T ED APPEN DIX
182
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>
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
... beanShell("someBeanShellExpression") ...
For example you could use the beanShell 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:
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:
183
L A N G U A G E S S U P P OR T E D A P P E ND I X
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"/>
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
LAN GUAGES SUPPO R T ED APPEN DIX
184
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>
<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.
185
L A N G U A G E S S U P P OR T E D A P P E ND I X
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"/>
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") ...
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 $100
from("queue:foo").filter(groovy("request.lineItems.any { i -> i.value > 100
}")).to("queue:bar")
LAN GUAGES SUPPO R T ED APPEN DIX
186
And the Spring DSL:
<route>
<from uri="queue:foo"/>
<filter>
<groovy>request.lineItems.any { i -> i.value > 100 }</groovy>
<to uri="queue:bar"/>
</filter>
</route>
ScriptContext
The JSR-223 scripting languages ScriptContext is pre configured with the following attributes all
set at ENGINE_SCOPE:
Attribute
Type
Value
context
org.apache.camel.CamelContext
The Camel Context
exchange
org.apache.camel.Exchange
The current Exchange
request
org.apache.camel.Message
The IN message
response
org.apache.camel.Message
The OUT message
Attributes
You can add your own attributes with the attribute(name, value) DSL method, such
as:
In the sample below we add an attribute user that is an object we already have instantiated
as myUser. This object has a getFirstName() method that we want to set as header on the
message. We use the groovy language to concat the first and last name into a single string that
is returned.
from("direct:in").setHeader("name").groovy("'$user.firstName
$user.lastName'").attribute("user", myUser").to("seda:users");
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>
187
L A N G U A G E S S U P P OR T E D A P P E ND I X
</setHeader>
<to uri="seda:users"/>
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>
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>
LAN GUAGES SUPPO R T ED APPEN DIX
188
</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):
<from uri="direct:in"/>
<setHeader headerName="firstName">
<expression language="jaskel">user.firstName</expression>
</setHeader>
<to uri="seda:users"/>
189
L A N G U A G E S S U P P OR T E D A P P E ND 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>
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:
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.
LAN GUAGES SUPPO R T ED APPEN DIX
190
from("direct:in").setHeader("name").groovy("'$user.firstName
$user.lastName'").attribute("user", myUser").to("seda:users");
Any scripting language
Camel can run any JSR-223 scripting languages using the script DSL method such as:
from("direct:in").setHeader("firstName").script("jaskel",
"user.firstName").attribute("user", myUser").to("seda:users");
This is a bit different using the Spring DSL where you use the expression element that
doesn't support setting attributes (yet):
<from uri="direct:in"/>
<setHeader headerName="firstName">
<expression language="jaskel">user.firstName</expression>
</setHeader>
<to uri="seda:users"/>
Dependencies
To use scripting languages in your camel routes you need to add the a dependency on
camel-script which integrates the JSR-223 scripting engine.
If you use maven you could just add the following to your pom.xml, substituting the version
number for the latest & greatest release (see the download page for the latest versions).
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-script</artifactId>
<version>1.4.0</version>
</dependency>
RUBY
Camel supports Ruby among other Scripting Languages to allow an Expression or Predicate to
be used in the DSL or Xml Configuration.
To use a Ruby expression use the following Java code
... ruby("someRubyExpression") ...
For example you could use the ruby function to create an Predicate in a Message Filter or as
an Expression for a Recipient List
Example
In the sample below we use Ruby to create a Predicate use in the route path, to route
exchanges from admin users to a special queue.
191
L A N G U A G E S S U P P OR T E D A P P E ND I X
from("direct:start")
.choice()
.when().ruby("$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>$request.headers['user'] == 'admin'</ruby>
<to uri="seda:adminQueue"/>
</when>
<otherwise>
<to uri="seda:regularQueue"/>
</otherwise>
</choice>
</route>
ScriptContext
The JSR-223 scripting languages ScriptContext is pre configured with the following attributes all
set at ENGINE_SCOPE:
Attribute
Type
Value
context
org.apache.camel.CamelContext
The Camel Context
exchange
org.apache.camel.Exchange
The current Exchange
request
org.apache.camel.Message
The IN message
response
org.apache.camel.Message
The OUT message
Attributes
You can add your own attributes with the attribute(name, value) DSL method, such
as:
In the sample below we add an attribute user that is an object we already have instantiated
as myUser. This object has a getFirstName() method that we want to set as header on the
message. We use the groovy language to concat the first and last name into a single string that
is returned.
from("direct:in").setHeader("name").groovy("'$user.firstName
$user.lastName'").attribute("user", myUser").to("seda:users");
LAN GUAGES SUPPO R T ED APPEN DIX
192
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"/>
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 is a really simple language you can use. Its primarily intended
for being a really small and simple language for testing without requiring any new dependencies
or knowledge of XPath; so its ideal for testing in camel-core. However for real world use cases
you are generally recommended to choose a more expressive and powerful language such as:
• Bean Language
• EL
• OGNL
• 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?".
193
L A N G U A G E S S U P P OR T E D A P P E ND I X
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
id
String
the input message id
body
Object
the input body
in.body
Object
the input body
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
out.header.foo
Object
refer to the out header foo
out.headers.foo
Object
refer to the out header foo
property.foo
Object
refer to the foo property on the exchange
sys.foo
String
refer to the system property
exception.message
String
New in Camel 2.0. Refer to the exception.messsage on
the exchange, is null if no exception set on exchange
String
New in Camel 1.5. Date formatting using the
java.text.SimepleDataFormat 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
New in 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.
date:command:pattern
bean:bean expression
LAN GUAGES SUPPO R T ED APPEN DIX
194
Operator support
Avaiable 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 ${ }.
Camel will automatically type convert the rightValue type to the leftValue type, so its able to eg.
convert a string into a numeric so you can use > comparison for numeric values.
The following operators is supported:
Operator
Description
==
equals
>
greather than
>=
greather than or equals
<
less than
<=
less than or equals
!=
not equals
contains
For testing if contains in a string based value
not
contains
For testinf if not contains in a string based value
regex
For matching against a given regular expression pattern defined as a String
value
not regex
For not matching against a given regular expression pattern defined as a String
value
in
For matching if in a set of values, each element must be separated by comma.
not in
For matching if not in a set of values, each element must be separated by
comma.
Some examples:
simple("${in.header.foo} == 'foo'")
// ' ' can be omitted
simple("${in.header.foo} == foo")
// here Camel will type convert '100' into the type of in.header.bar and if its an
Integer '100' will also be converter to an Integer
195
L A N G U A G E S S U P P OR T E D A P P E ND I X
simple("${in.header.bar} == '100'")
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:
simple("${in.header.type} not in 'gold,silver'")
Samples
In the Spring XML sample below we filter based on a header value:
<from uri="seda:orders">
<filter>
<simple>in.header.foo</simple>
<to uri="mock:fooOrders"/>
</filter>
</from>
The Simple language can be used for the predicate test above in the Message Filter pattern,
where we test if the in message has a foo header (a header with the key foo exists). If the
expression evaluates to true then the message is routed to the mock:foo endpoint,
otherwise its lost in the deep blue sea
.
LAN GUAGES SUPPO R T ED APPEN DIX
196
Can be used in Spring XML
As the Spring XML does not have all the power as the Java DSL with all its various builder
methods, you had to resort to use some other languages
for testing with simple operators. Now you can do this with the simple language. In the
sample below we want to test if the header is a widget order:
<from uri="seda:orders">
<filter>
<simple>${in.header.type} == 'widget'</simple>
<to uri="bean:orderService?method=handleWidget"/>
</filter>
</from>
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");
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");
197
L A N G U A G E S S U P P OR T E D A P P E ND I X
Dependencies
The Bean 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.
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.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:modified
Date
yes
no
yes
no
Camel 2.0: refers to the file last modified
returned as a Date type
LAN GUAGES SUPPO R T ED APPEN DIX
198
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.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\camel-core\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\camel-core\target\filelanguage\test. And
we configure out endpoint to use the absolute starting directory
\workspace\camel\camel-core\target\filelanguage. The the file tokens will
return as:
199
Expression
Returns
file:name
test\hello.txt
file:name.noext
test\hello
L A N G U A G E S S U P P OR T E D A P P E ND I X
file:onlyname
hello.txt
file:onlyname.noext
hello
file:ext
txt
file:parent
\workspace\camel\camel-core\target\filelanguage\test
file:path
\workspace\camel\camel-core\target\filelanguage\test\hello.txt
file:absolute
true
file:absolute.path
\workspace\camel\camel-core\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.
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.
LAN GUAGES SUPPO R T ED APPEN DIX
200
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.
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")
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
Dependencies
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).
201
L A N G U A G E S S U P P OR T E D A P P E ND I X
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-josql</artifactId>
<version>1.4.0</version>
</dependency>
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");
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/variables/
environment-variables
env
Object
OS environment
variables
LAN GUAGES SUPPO R T ED APPEN DIX
202
http://camel.apache.org/xml/variables/
system-properties
system
http://camel.apache.org/xml/variables/
exchange-property
Object
Java System
properties
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 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.
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");
203
L A N G U A G E S S U P P OR T E D A P P E ND I X
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>
<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!
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>
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
LAN GUAGES SUPPO R T ED APPEN DIX
204
// 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");
// 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 id="camel" 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.
205
L A N G U A G E S S U P P OR T E D A P P E ND I X
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.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")};
}
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("/foo/bar/text()") String correlationID, @Body
String body) {
// process the inbound message here
}
}
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.
LAN GUAGES SUPPO R T ED APPEN DIX
206
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:
Support
version
Variable
Type
Description
exchange
Exchange
The current Exchange
in.body
Object
The In message's body
>= 1.6.1
out.body
Object
The OUT message's body (if any)
>= 1.6.1
in.headers.*
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
out.headers.*
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.
key name
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"
207
L A N G U A G E S S U P P OR T E D A P P E ND I X
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!
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");
LAN GUAGES SUPPO R T ED APPEN DIX
208
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
• 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>
209
L A N G U A G E S S U P P OR T E D A P P E ND I X
CHAPTER
9
°°°°
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.
CH APT ER 9 - PAT T ER N APPEN DIX
210
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>
<bean ref="foo"/>
<bean ref="bar"/>
<to uri="activemq:OutputQueue"/>
</pipeline>
</route>
211
CH A PTE R 9 - PAT T E R N A P P E ND I X
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.
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.
CH APT ER 9 - PAT T ER N APPEN DIX
212
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" streamCache="false" id="camel"
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>
Choice without otherwise
If you use a choice without adding an otherwise, any unmatched exchanges will be
dropped by default. If you prefer to have an exception for an unmatched exchange, you can add
a throwFault to the otherwise.
....otherwise().throwFault("No matching when clause found on choice 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 Endpoint and URIs. Then you could try
out some of the Examples first before trying this pattern out.
213
CH A PTE R 9 - PAT T E R N A P P E ND I X
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
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
CH APT ER 9 - PAT T ER N APPEN DIX
214
<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.
from("activemq:My.Queue").
to("velocity:com/acme/MyResponse.vm");
For further examples of this pattern in use you could look at one of the JUnit tests
• TransformTest
• TransformViaDSLTest
• TransformProcessorTest
• TransformWithExpressionTest (test resource)
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 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
215
CH A PTE R 9 - PAT T E R N A P P E ND I X
• 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.
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 the following
components
• JMS for working with JMS Topics for high performance, clustering and load balancing
• XMPP when using rooms for group communication
CH APT ER 9 - PAT T ER N APPEN DIX
216
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" streamCache="false" id="camel"
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>
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.
217
CH A PTE R 9 - PAT T E R N A P P E ND I X
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.
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 client is then notified as the caused exception is set on the
Exchange. However if you want to handle this you can set the handled to true on the Dead
Letter Channel.
For instance configuring the dead letter channel as:
errorHandler(deadLetterChannel("jms:queue:dead").maximumRedeliveries(3).dealy(5000).handled(true));
CH APT ER 9 - PAT T ER N APPEN DIX
218
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 not configured and thus its false.
About moving Exchange to dead letter queue and using the original body
Available as of Camel 2.0
The option useOriginalBody is used for routing the original input body instead of the
current body that potential 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
useOriginalBody option as shown below:
// will use original body
errorHandler(deadLetterChannel("jms:queue:dead")
.useOriginalBody().handled(true).mamimumRedeliveries(5).delay(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 1.5.1 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.
Redelivery default values
The default redeliver policy will use the following values:
• maximumRedeliveries=5
• delay=1000L (1 second, new as of Camel 2.0)
• use initialRedeliveryDelay for previous versions
219
CH A PTE R 9 - PAT T E R N A P P E ND 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.
• maximumRedeliveryDelay = 60 * 1000L (60 seconds, new option in Camel 1.4)
• And the exponential backoff and collision avoidance is turned off.
• The retriesExhaustedLogLevel and retryAttemptedLogLevel are set to
LoggingLevel.ERROR
• Stack traces is logged
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 ERROR logging level by default. You can change this by
specifying retriesExhaustedLogLevel and/or retryAttemptedLogLevel. See
ExceptionBuilderWithRetryLoggingLevelSetTest for an example.
In Camel 2.0 you can turn off stack traces for the caused exceptions. As the stack trace is
logged at before each redelivery attempt. 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
CH APT ER 9 - PAT T ER N APPEN DIX
220
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:
• Attempt number 0..4 = 0 millis (as the first group start with 5)
• Attempt number 5..9 = 1000 millis (the first group)
• Attempt number 10..19 = 5000 millis (the second group)
• Attempt number 20.. = 20000 millis (the last group)
You can start a group with limit 0 to eg have a starting delay:
delayPattern=0:1000;5:5000
• Attempt number 0..4 = 1000 millis (the first group)
• 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=0:5000;3:1000 we start with
5 sec delay and then later reduce that to 1 second.
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 CamelRedeliveryCount.
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.
Samples
The following example shows how to configure the Dead Letter Channel configuration using
the DSL
RouteBuilder builder = new RouteBuilder() {
public void configure() {
221
CH A PTE R 9 - PAT T E R N A P P E ND I X
// 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");
}
};
How can I modify the Exchange before redelivery?
In Camel 1.5.1 we added support directly in Dead Letter Channel to set a Processor that is
executed before each redelivery attempt. In older releases you have to sort to other solutions
that isn't as solid as this new feature.
Camel 1.5.0 or older
When Dead Letter Channel is doing redeliver it redeliveries immediately with the original
Exchange that caused the error in the first place. However in some situations you might want
to be able to alter the message before its redelivered. As Camel at this time of writing doesn't
have a nice DSL syntax or configuration on the Dead Letter Channel to allow custom
processing before redeliver we are gonna show a different solution, that actually also pin points
the flexibility Camel has.
We are going to use an interceptor that gets triggered when an Exchange is being
redelivered. We use the fact that interceptors by default will proceed from the point of
interceptor. This is the Detour EIP pattern we are using.
The code below demonstrates this.
An error occurred: http://svn.apache.org/repos/asf/camel/trunk/camel-core/src/test/java/org/
apache/camel/processor/interceptor/InterceptAlterMessageBeforeRedeliveryTest.java. The
system administrator has been notified.
However you should notice as Camel will keep the redeliver flag on the Exchange for the
remainder of its routing this interceptor will kick in for subsequence processing. So you should
keep track if you already have altered the message before redelivery.
CH APT ER 9 - PAT T ER N APPEN DIX
222
Code uses wrong header key
As the code above is based on an unit test its based on Camel 2.x or newer. The header to
use in Camel 1.x should be "org.apache.camel.redeliveryCount" instead of
"CamelRedeliveryCount".
Camel 1.5.1 or newer
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")
.onRedelivery(new MyRedeliverPrcessor())
// setting delay to zero is just to make unit teting faster
.delay(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 MyRedeliverPrcessor 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("CamelRedeliveryCounter",
Integer.class);
exchange.getIn().setBody(body + count);
}
}
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.
• Error Handler
223
CH A PTE R 9 - PAT T E R N A P P E ND I X
• Exception Clause
Guaranteed Delivery
Camel supports the Guaranteed Delivery from the EIP patterns using 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
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.
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)
CH APT ER 9 - PAT T ER N APPEN DIX
224
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
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" streamCache="false" id="camel"
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"/>
225
CH A PTE R 9 - PAT T E R N A P P E ND I X
</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.
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");
Using the Spring XML Extensions
<camelContext errorHandlerRef="errorHandler" streamCache="false" id="camel"
xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="seda:a"/>
<filter>
<xpath>$foo = 'bar'</xpath>
<to uri="seda:b"/>
</filter>
CH APT ER 9 - PAT T ER N APPEN DIX
226
</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.
Recipient List
The Recipient List from the EIP patterns allows you to route messages to a number of
dynamically specified recipients.
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" streamCache="false" id="camel"
xmlns="http://camel.apache.org/schema/spring">
<route>
227
CH A PTE R 9 - PAT T E R N A P P E ND I X
<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 1.5.1: a single String with values separated with comma
• any other type will be regarded as a single value
Using the Spring XML Extensions
<camelContext errorHandlerRef="errorHandler" streamCache="false" id="camel"
xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="seda:a"/>
<recipientList>
<xpath>$foo</xpath>
CH APT ER 9 - PAT T ER N APPEN DIX
228
</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 1.5.1
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.
<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(","));
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
229
CH A PTE R 9 - PAT T E R N A P P E ND I X
As of Camel 2.0, you need to specify a Splitter as split(). In earlier versions of Camel,
you need to use splitter().
Example
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" streamCache="false" id="camel"
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.
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 id="camel" xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="direct:start"/>
<split>
<tokenize token="@"/>
<to uri="mock:result"/>
</split>
CH APT ER 9 - PAT T ER N APPEN DIX
230
What does the splitter return?
The Splitter will by default return the last splitted message. 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.
</route>
</camelContext>
Message Headers
The following headers is set on each Exchange that are split:
header
type
description
org.apache.camel.splitCounter
int
Camel 1.x: A split counter that
increases for each Exchange being
split. The counter starts from 0.
org.apache.camel.splitSize
int
Camel 1.x: The total number of
Exchanges that was splitted. This
header is not applied for stream based
splitting.
CamelSplitIndex
int
Camel 2.0: A split counter that
increases for each Exchange being
split. The counter starts from 0.
int
Camel 2.0: The total number of
Exchanges that was splitted. This
header is not applied for stream based
splitting.
CamelSplitSize
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");
231
CH A PTE R 9 - PAT T E R N A P P E ND I X
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
Available as of Camel 1.5
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");
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");
ThreadPoolExecutor threadPoolExecutor = new ThreadPoolExecutor(8, 16, 0L,
TimeUnit.MILLISECONDS, new LinkedBlockingQueue());
from("activemq:my.queue").split(xPathBuilder, true,
threadPoolExecutor).to("activemq:my.parts");
In the Spring DSL try this:
Available as of Camel 1.6.0
<camelContext id="camel" xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="direct:parallel-custom-pool"/>
<split executorServiceRef="threadPoolExecutor">
<xpath>/invoice/lineItems</xpath>
<to uri="mock:result"/>
</split>
</route>
</camelContext>
<!-- There's an easier way of specifying constructor args, just can't remember it
at the moment... old Spring syntax will do for now! -->
<bean id="threadPoolExecutor" class="java.util.concurrent.ThreadPoolExecutor">
<constructor-arg index="0" value="8"/>
CH APT ER 9 - PAT T ER N APPEN DIX
232
<constructor-arg index="1" value="16"/>
<constructor-arg index="2" value="0"/>
<constructor-arg index="3" value="MILLISECONDS"/>
<constructor-arg index="4"><bean
class="java.util.concurrent.LinkedBlockingQueue"/></constructor-arg>
</bean>
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 splitBody(String body) {
// since this is based on an unit test you can of couse
// 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 answer = new ArrayList();
String[] parts = body.split(",");
for (String part : parts) {
answer.add(part);
}
return answer;
}
233
CH A PTE R 9 - PAT T E R N A P P E ND I X
/**
* 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")
// 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")
CH APT ER 9 - PAT T ER N APPEN DIX
234
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
// copy from OUT as we use InOut pattern
String orders = oldExchange.getOut().getBody(String.class);
String newLine = newExchange.getOut().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.getOut().setBody(orders);
// return old as this is the one that has all the orders gathered until now
return oldExchange;
235
CH A PTE R 9 - PAT T E R N A P P E ND I X
}
}
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)]
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.
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.
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
CH APT ER 9 - PAT T ER N APPEN DIX
236
from("direct:start").resequencer(body()).to("mock:result");
This is equvalent to
from("direct:start").resequencer(body()).batch().to("mock:result");
The batch-processing resequencer can be further configured via the size() and timeout()
methods.
from("direct:start").resequencer(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.
from("direct:start").resequencer(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("JMSPriority"))
for example to reorder messages using their JMS priority.
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
resequencer(header("JMSPriority"), header("MyCustomerRating"))
Using the Spring XML Extensions
<camelContext id="camel" xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="direct:start" />
<resequencer>
<simple>body</simple>
<to uri="mock:result" />
<!-batch-config can be ommitted for default (batch) resequencer settings
-->
<batch-config batchSize="300" batchTimeout="4000" />
</resequencer>
</route>
</camelContext>
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.
237
CH A PTE R 9 - PAT T E R N A P P E ND I X
Using the Fluent Builders
from("direct:start").resequencer(header("seqnum")).stream().to("mock:result");
The stream-processing resequencer can be further configured via the capacity() and
timeout() methods.
from("direct:start").resequencer(header("seqnum")).stream().capacity(5000).timeout(4000L).to("mock:res
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").resequencer(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 comparator via the
comparator() method
ExpressionResultComparator<Exchange> comparator = new MyComparator();
from("direct:start").resequencer(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").resequencer(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"/>
CH APT ER 9 - PAT T ER N APPEN DIX
238
<resequencer>
<simple>in.header.seqnum</simple>
<to uri="mock:result" />
<stream-config capacity="5000" timeout="4000"/>
</resequencer>
</route>
</camelContext>
Further Examples
For further examples of this pattern in use you could look at the batch-processing resequencer
junit test case and the stream-processing resequencer 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.
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)
239
CH A PTE R 9 - PAT T E R N A P P E ND I X
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
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
This feature is available since Camel 2.0
Using the Fluent Builders
AggregationStrategy aggregationStrategy = ...
from("direct:start")
.enrich("direct:resource", aggregationStrategy)
.to("direct:result");
CH APT ER 9 - PAT T ER N APPEN DIX
240
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="..." />
241
CH A PTE R 9 - PAT T E R N A P P E ND 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.
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>
CH APT ER 9 - PAT T ER N APPEN DIX
242
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
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) {
243
CH A PTE R 9 - PAT T E R N A P P E ND I X
return "<person name=\"" + name + "\"/>";
}
}
Using the Spring XML Extensions
The same example in the Spring DSL
<camelContext id="camel" 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
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.
CH APT ER 9 - PAT T ER N APPEN DIX
244
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.
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.
245
CH A PTE R 9 - PAT T E R N A P P E ND I X
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
Method
name
Description
receive()
Waits until a message is available and then returns it; potentially blocking
forever
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:
CH APT ER 9 - PAT T ER N APPEN DIX
246
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:
<camelContext id="camel" 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(name = "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
247
CH A PTE R 9 - PAT T E R N A P P E ND I X
producer.sendBody("seda:foo", body);
// assert mock received the body
mock.assertIsSatisfied();
}
}
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("timer://foo?period=5000").bean(cool, "someBusinessLogic");
from("activemq:queue.foo").to("mock:result");
And then we have out logic in our bean:
public static class MyCoolBean {
private 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, wait at most 3 sec
String msg = consumer.receiveBody("activemq:queue.inbox", 3000,
String.class);
if (msg == null) {
// no more messages in queue
break;
}
// do something with body
msg = "Hello " + msg;
CH APT ER 9 - PAT T ER N APPEN DIX
248
// send it to the next queue
producer.sendBodyAndHeader("activemq:queue.foo", msg, "number", count++);
}
}
}
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
• File
• JPA
• Mail
• Quartz
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.
Competing Consumers
Camel supports the Competing Consumers from the EIP patterns using a few different
components.
249
CH A PTE R 9 - PAT T E R N A P P E ND I X
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,ß 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 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.
CH APT ER 9 - PAT T ER N APPEN DIX
250
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
•
•
•
•
JMS
Selective Consumer
Content Based Router
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.
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.
251
CH A PTE R 9 - PAT T E R N A P P E ND I X
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" streamCache="false" id="camel"
xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="seda:a"/>
<filter>
<xpath>$foo = 'bar'</xpath>
<process ref="myProcessor"/>
</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.
CH APT ER 9 - PAT T ER N APPEN DIX
252
Another alternative is to combine the Message Dispatcher or Content Based Router with
File or JPA components for durable subscribers then something like Queue for non-durable.
See Also
•
•
•
•
•
•
•
JMS
File
JPA
Message Dispatcher
Selective Consumer
Content Based Router
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.
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 MessageIdRepository 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.
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
253
CH A PTE R 9 - PAT T E R N A P P E ND I X
return new SpringRouteBuilder() {
public void configure() {
from("direct:start").idempotentConsumer(
header("messageId"),
jpaMessageIdRepository(bean(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
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" />
CH APT ER 9 - PAT T ER N APPEN DIX
254
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.
</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");
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>
255
CH A PTE R 9 - PAT T E R N A P P E ND I X
<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.
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"
CH APT ER 9 - PAT T ER N APPEN DIX
256
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"/>
</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 = bean("PROPAGATION_REQUIRED",
SpringTransactionPolicy.class);
// use this error handler instead of DeadLetterChannel that is the default
// Notice: transactionErrorHandler is in SpringRouteBuilder
if (useTransactionErrorHandler) {
// 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");
As its a unit test we need to setup the database and this is easily done with Spring JdbcTemplate
// create database and insert dummy data
final DataSource ds = getMandatoryBean(DataSource.class, "dataSource");
jdbc = new JdbcTemplate(ds);
257
CH A PTE R 9 - PAT T E R N A P P E ND I X
jdbc.execute("create table books (title varchar(50))");
jdbc.update("insert into books (title) values (?)", new Object[] {"Camel in Action"});
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) {
// expeced as we fail
assertIsInstanceOf(TransactedRuntimeCamelException.class, e.getCause());
assertTrue(e.getCause().getCause() instanceof IllegalArgumentException);
assertEquals("We don't have Donkeys, only Camels",
e.getCause().getCause().getMessage());
}
int count = jdbc.queryForInt("select count(*) from books");
assertEquals("Number of books", 1, count);
}
CH APT ER 9 - PAT T ER N APPEN DIX
258
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:policy 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="jmsConnectionFactory" class="org.apache.activemq.ActiveMQConnectionFactory">
<property name="brokerURL"
value="vm://localhost?broker.persistent=false&amp;broker.useJmx=false"/>
</bean>
<bean id="jmsTransactionManager"
class="org.springframework.jms.connection.JmsTransactionManager">
<property name="connectionFactory" ref="jmsConnectionFactory"/>
</bean>
<bean id="jmsConfig" class="org.apache.camel.component.jms.JmsConfiguration">
<property name="connectionFactory" ref="jmsConnectionFactory"/>
<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>
259
CH A PTE R 9 - PAT T E R N A P P E ND I X
<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();
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">
CH APT ER 9 - PAT T ER N APPEN DIX
260
<!-- 1: from the jms queue -->
<camel:from uri="activemq:queue:okay"/>
<!-- 2: setup the transactional boundaries to require a transaction -->
<camel:policy 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"
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.
261
CH A PTE R 9 - PAT T E R N A P P E ND I X
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.
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 id="camel" xmlns="http://camel.apache.org/schema/spring">
<route>
CH APT ER 9 - PAT T ER N APPEN DIX
262
<from uri="direct:okay"/>
<!-- we mark this route as transacted. Camel will
transaction manager
and use it by default. We can optimally pass
policy to use
that is configured with a spring transaction
Camel supports
convention over configuration as we can just
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>
lookup the spring
in arguments to specify a
manager of choice. However
use the defaults out of the
<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="jmsConnectionFactory" class="org.apache.activemq.ActiveMQConnectionFactory">
<property name="brokerURL"
value="vm://localhost?broker.persistent=false&amp;broker.useJmx=false"/>
</bean>
263
CH A PTE R 9 - PAT T E R N A P P E ND I X
<!-- setup spring jms TX manager -->
<bean id="jmsTransactionManager"
class="org.springframework.jms.connection.JmsTransactionManager">
<property name="connectionFactory" ref="jmsConnectionFactory"/>
</bean>
<!-- define our activemq component -->
<bean id="activemq" class="org.apache.activemq.camel.component.ActiveMQComponent">
<property name="connectionFactory" ref="jmsConnectionFactory"/>
<!-- 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">
<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"/>
See Also
•
•
•
•
Error handling in Camel
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.
CH APT ER 9 - PAT T ER N APPEN DIX
264
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.
Messaging Gateway
Camel has several endpoint components that support the Messaging Gateway from the EIP
patterns.
Components like Bean, CXF and Pojo provide a a way to bind a Java interface to the
message exchange.
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.
Service Activator
Camel has several endpoint components that support the Service Activator from the EIP
patterns.
265
CH A PTE R 9 - PAT T E R N A P P E ND I X
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
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.
CH APT ER 9 - PAT T ER N APPEN DIX
266
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
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.
Below is the processor variation shown:
from("direct:start")
.wireTap("direct:foo", 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");
And the Expression variation:
267
CH A PTE R 9 - PAT T E R N A P P E ND I X
from("direct:start")
.wireTap("direct:foo", 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:start"/>
<wireTap uri="direct:foo">
<body><constant>Bye World</constant></body>
</wireTap>
<to uri="mock:result"/>
</route>
And the Expression variation, where the expression is defined in the body tag:
<route>
<from uri="direct:start2"/>
<wireTap uri="direct:foo" processorRef="myProcessor"/>
<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
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" streamCache="false" id="camel"
xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="seda:a"/>
<multicast>
<to uri="seda:tap"/>
<to uri="seda:b"/>
</multicast>
</route>
</camelContext>
CH APT ER 9 - PAT T ER N APPEN DIX
268
Further Example
For another example of this pattern in use you could look at the wire tap 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.
269
CH A PTE R 9 - PAT T E R N A P P E ND I X
CHAPTER
10
°°°°
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 the 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:[topic:]destinationName
So for example to send to queue FOO.BAR you would use
activemq:FOO.BAR
You can be completely specific if you wish via
activemq:queue:FOO.BAR
If you want to send to a topic called Stocks.Prices then you would use
activemq:topic:Stocks.Prices
Options
See Options on the JMS component as all these options also apply for this component.
CH APT ER 10 - CO M PO N EN T APPEN DIX
270
Configuring the Connection Factory
The following 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>
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) {
// ...
}
}
Then use it in your Camel route as follows
from("file://foo/bar").
bean(MyListener.class);
i.e. you can reuse any of the Camel Components and easily integrate them into your JMS
MessageListener POJO!
271
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
Getting Component JAR
You 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>
<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
CH APT ER 10 - CO M PO N EN T APPEN DIX
272
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 to
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.
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 1 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:directory-name[?options]
So for example to send to the journal located in the /tmp/data directory you would use
activemq.journal:/tmp/data
Options
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
Name
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
273
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
• 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
Component
Endpoint
Getting Started
AMQP
The AMQP component supports the AMQP protocol via the Qpid project.
URI format
amqp:[queue:][topic:]destinationName[?option1=value[&option2=value2]]
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
ATOM COMPONENT
The atom: component is used for polling atom feeds.
Camel will default poll the feed every 60th seconds.
Note: The component currently only supports polling (consuming) feeds.
URI format
atom://atomUri
Where atomUri is the URI to the atom feed to poll.
CH APT ER 10 - CO M PO N EN T APPEN DIX
274
Options
Property
Default
Description
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.
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.
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
true to use fixed delay between pools, otherwise
fixed rate is used. See ScheduledExecutorService in
JDK for details.
splitEntries
filter
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
275
Value
Behavior
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
splitEntries
true
Only a single entry from the currently being processed feed is set:
exchange.in.body(Entry)
splitEntries
false
The entires 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.
Samples
In this sample we poll James Strahams 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;
// We use a simple Hashtable for our bean registry. For more advanced usage Spring is
supported out-of-the-box
private Hashtable beans = new Hashtable();
// We iniitalize Camel
private void setupCamel() throws Exception {
// First we register a blog service in our bean registry
beans.put("blogService", new BlogService());
// Then we create the camel context with our bean registry
context = new DefaultCamelContext(new
CamelInitialContextFactory().getInitialContext(beans));
// Then we add all the routes we need using the route builder DSL syntax
context.addRoutes(createRouteBuilder());
// And finally we must start Camel to let the magic routing begins
context.start();
CH APT ER 10 - CO M PO N EN T APPEN DIX
276
}
/**
* This is the route builder where we create our routes in the advanced Camel DSL
syntax
*/
protected RouteBuilder createRouteBuilder() 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");
// From the feeds we filter each blot entry by using our blog service class
from("seda:feeds").filter().method("blogService",
"goodBlog").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
*/
public void testFiltering() throws Exception {
// Get the mock endpoint
MockEndpoint mock = context.getEndpoint("mock:result", MockEndpoint.class);
// There should be two good blog entries from the feed
mock.expectedMessageCount(2);
// Asserts that the above expectations is true, will throw assertions exception if
it failed
277
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
// Camel will default wait max 20 seconds for the assertions to be true, if the
conditions
// is true sooner Camel will continue
mock.assertIsSatisfied();
}
/**
* 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();
// We like blogs about Camel
boolean good = title.toLowerCase().contains("camel");
return good;
}
}
See Also
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
BEAN COMPONENT
The bean: component binds beans to Camel message exchanges.
URI format
bean:someName[?options]
Where someName can be any string which is used to lookup the bean in the Registry
Options
Name
Type
Default
Description
CH APT ER 10 - CO M PO N EN T APPEN DIX
278
method
cache
multiParameterArray
String
boolean
boolean
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.
false
If enabled Camel will cache the result of the
first Registry lookup. Cache can be enabled if
the bean in the Registry is defined as a
singleton scope.
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 the an
array of parameters.
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.xml; or if
you don't use Spring then put 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);
279
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
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:
<camelContext id="camel" 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 IN
body to the String type and store the output of the method on the Exchange OUT body.
Bean Binding
How bean methods are chosen to be invoked (if they are not specified explicitly via the
method parameter) and how parameter values are constructed from the Message are all
defined by the Bean Binding mechanism which is used througout all of the various Bean
Integration mechanisms in Camel.
See Also
•
•
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
Bean Binding
Bean Integration
CH APT ER 10 - CO M PO N EN T APPEN DIX
280
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 have the list component to be able to browse the Exchanges that is
passed through:
from("activemq:order.in").to("browse:orderReceived").to("bean:processOrder");
Then we will be able to inspect the received exchanges from 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
COMETD COMPONENT
The cometd: component is a transport for working with the jetty implementation of the
cometd/bayeux protocol.
281
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
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.
URI format
cometd://host:port/channelname
The channelname represents a topic that can be subscribed by the Camel endpoints.
Examples
cometd://localhost:8080/service/mychannel
cometds://localhost:8443/service/mychannel
where cometds represents an SSL configured endpoint.
See this blog entry by David Greco whom contributed this component to Apache Camel, for
a full sample.
Options
Name
Default
Value
Description
resourceBase
It's the root directory for the web resources
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" then 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
See Also
• Configuring Camel
• Component
CH APT ER 10 - CO M PO N EN T APPEN DIX
282
• Endpoint
• Getting Started
CXF COMPONENT
The cxf: component provides integration with Apache CXF for connecting to JAX-WS 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>
URI format
cxf://address?options
Where address represents the CXF endpoint's address
cxf:bean:cxfEndpoint
Where cxfEndpoint represents the spring bean's name which presents the CXF endpoint
For either style above, you can append options to the URI as follows:
cxf:bean:cxfEndpoint?wsdlURL=wsdl/hello_world.wsdl&dataFormat=PAYLOAD
Options
283
Name
Description
Example
wsdlURL
The location of the WSDL.
file://local/wsdl/hello.wsdl or wsdl/
hello.wsdl
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
serviceClass
The name of the SEI(Service Endpoint
Interface) class. This class can have but does
not require JSR181 annotations.
Since 2.0, it is possible to use # notation
to reference a serviceClass object instance
from the registry. E.g.
serviceClass=#beanName. 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.
org.apache.camel.Hello
serviceClassInstance
In 1.6 or later (will be deprecated
in 2.0), serviceClassInstance works like
serviceClass=#beanName, which looks up a
serviceObject instance from the registry.
serviceClassInstance=beanName
serviceName
The service name this service is
implementing, it maps to the
wsdl:service@name.
{http://org.apache.camel}
ServiceName
portName
The port name this service is implementing,
it maps to the wsdl:port@name.
{http://org.apache.camel}
PortName
dataFormat
Which data type messages the CXF
endpoint supports
POJO, PAYLOAD, MESSAGE
relayHeaders
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
true, false
wrapped
Which kind of operation that CXF endpoint
producer will invoke
true, false
setDefaultBus
Will set the default bus when CXF endpoint
create a bus by itself
true, false
CH APT ER 10 - CO M PO N EN T APPEN DIX
284
bus
New in 2.0, use # notation to reference a
bus object from the registry. The
referenced object must be an instance of
org.apache.cxf.Bus.
bus=#busName
cxfBinding
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.
cxfBinding=#bindingName
headerFilterStrategy
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.
headerFilterStrategy=#strategyName
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.
NOTE From CAMEL 1.5.1 , the serviceClass for CXF producer (i.e. the "to" endpoint)
should be 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 at write phase. The following is an example.
285
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
<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 a perspective of a JAXWS
WSDL-first developer.
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 the wire 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
MessageHeadersRelay interface. An concrete implementation 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 asserts that all headers "in-band" and "out-of-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
CH APT ER 10 - CO M PO N EN T APPEN DIX
286
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>
<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-of-band
message headers are available for filtering as the in-band headers has 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 in-band headers is required, please you PAYLOAD mode or plug in a
(pretty straight forward) 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
287
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
uri="cxf:bean:serviceNoRelayEndpoint?headerFilterStrategy=#dropAllMessageHeadersStrategy"/>
</route>
• The MessageHeadersRelay interface has changed slightly and has been renamed to
MessageHeaderFilter. It is a property of 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.
by omitting it. -->
<bean
class="org.apache.camel.component.cxf.SoapMessageHeaderFilter"/>
It can be removed
<!-- 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
Description
type
Required?
Default
value
relayHeaders
all message headers will
be processed by
Message Header Filters
boolean
no
true
(1.6.1
behavior)
relayAllMessageHeaders
all message headers will
be propagated (without
processing by Message
Header Filters)
boolean
no
false
(1.6.1
behavior)
allowFilterNamespaceClash
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
boolean
no
false
(1.6.1
behavior)
CH APT ER 10 - CO M PO N EN T APPEN DIX
288
Configure the CXF endpoints with spring
You can configure the CXF endpoint with the below spring configuration file, and you can also
embed the endpoint into the camelContext tags.
<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 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://camel.apache.org/schema/cxf" as the
cxfendpont'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-2.0.xsd
http://camel.apache.org/schema/spring http://camel.apache.org/schema/spring/
camel-spring.xsd
">
...
289
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
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:
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.
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 jaxws 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>s or
<ref>s.
cxf:inFaultInterceptors
The incoming fault interceptors for this endpoint. A list of
<bean>s or <ref>s.
cxf:outInterceptors
The outgoing interceptors for this endpoint. A list of <bean>s or
<ref>s.
cxf:outFaultInterceptors
The outgoing fault interceptors for this endpoint. A list of
<bean>s or <ref>s.
cxf:properties
A properties map which should be supplied to the JAX-WS
endpoint. See below.
cxf:handlers
A jaxws handler list which should be supplied to the JAX-WS
endpoint. See below.
CH APT ER 10 - CO M PO N EN T APPEN DIX
290
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 let camel-cxf component to use log4j instead of java.util.logging
CXF's default logger is using java.util.logging, if you want to change it to log4j.
Here is the instruction: Create a file, in the classpath, named META-INF/cxf/
org.apache.cxf.logger.This file should contain the fully-qualified name of the class
(org.apache.cxf.common.logging.Log4jLogger), with no comments, on a single line.
How to consume the message from the 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.
291
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
public class PersonProcessor implements Processor {
private static final transient Log LOG = LogFactory.getLog(PersonProcessor.class);
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
exchange.getFault().setBody(fault);
}
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 into a list and set the
message with this parameter list will be ok. The response message's body is a
messageContentsList, you can get the result from that list.
CH APT ER 10 - CO M PO N EN T APPEN DIX
292
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 with this code message.getbody(Object[].class)
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));
How to deal with the message for the camel-cxf endpoint in PAYLOAD data
format
PAYLOAD means you will get or set the payload message which has been take out the SOAP
envelope from or into the CXF message. 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.
Change in 2.0, CxfMessage.getBody() will return a
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.
from(routerEndpointURI).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);
293
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
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);
How to throw the SOAP Fault from Camel
If you are using the 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).throwFault(SOAP_FAULT);
If your cxf endpoint working in the MESSAGE data format, you could set the the SOAP Fault
message into 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();
// 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
How to propagate 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 camel-cxf endpoint producer to invoke the outside web service, you can set the
request context and get response context with below codes.
CxfExchange exchange = (CxfExchange)template.send(getJaxwsEndpointUri(), new
Processor() {
CH APT ER 10 - CO M PO N EN T APPEN DIX
294
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 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());
CXF BEAN COMPONENT (2.0 OR LATER)
The cxfbean: component allows other Camel endpoint to send exchange and invoke web
service bean objects. (Currently, it only supports JAXRS annotated service
bean.)
Note: CxfBeanEndpoint is a ProcessorEndpoint so it has no Consumers. It works similar to
a Bean component.
URI format
cxfbean:serviceBeanRef
Where serviceBeanRef is a registry key to looks service bean object. If serviceBeanRef references
to a List, elements of the List are the service bean objects accepted by the endpoint.
Options
295
Name
Description
Example
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
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
bus
CXF bus reference specified by the "#" notation. The
referenced object must be an instance of
org.apache.cxf.Bus.
bus=#busName
headerFilterStrategy
Header filter strategy specified by the "#" notation. The
referenced object must be an instance of
org.apache.camel.spi.HeaderFilterStrategy.
headerFilterStrategy=#stra
setDefaultBus
Will set the default bus when CXF endpoint create a bus
by itself
true, false
Headers
Name
Description
type
Required?
Default
value
in/
out
Exam
CamelCxfBeanCharacterEncoding
Character encoding
String
no
none
in
ISO-8
CamelCxfBeanContentType
Content type
String
no
*/*
in
text/x
CamelCxfBeanRequestBasePath
The value of this
header will be set in
the CXF message as
the
Message.BASE_PATH
property. It is needed
by CXF JAXRS
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://
CamelCxfBeanRequestPath
Request URI's path
String
yes
none
in
consu
CamelCxfBeanVerb
RESTful request verb
String
yes
none
in
GET,
DELE
Note: Currently, CXF Bean component has (only) been tested with Jetty
HTTP component it can understand headers from Jetty HTTP component
without requiring conversion.
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.
CH APT ER 10 - CO M PO N EN T APPEN DIX
296
First, create a route as the following. 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://localhost:9000" exactly.
from("jetty:http://localhost:9000?matchOnUriPrefix=true").
to("cxfbean:customerServiceBean");
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>
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.
url = new URL("http://localhost:9000/customerservice/orders/223/products/323");
in = url.openStream();
assertEquals("{\"Product\":{\"description\":\"product 323\",\"id\":323}}",
getStringFromInputStream(in));
See Also
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
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
Where name is used to find the DataSet instance in the Registry
297
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
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 - to simulate slow producers. Will 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 - to simulate slow consumers
preloadSize
0
Sets how many messages should be preloaded (sent) before
the route completes its initialization
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 then consumed from a queue
without loosing 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.
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.
CH APT ER 10 - CO M PO N EN T APPEN DIX
298
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
Load testing ActiveMQ with Camel
There is an example of load testing an ActiveMQ queue using Camel in the ActiveMQ source
code repository. The code lives at this location
• https://svn.apache.org/repos/asf/activemq/trunk/activemq-camel-loadtest/
You can grab the code
svn co https://svn.apache.org/repos/asf/activemq/trunk/activemq-camel-loadtest/
Then try running the test case
cd activemq-camel-loadtest
mvn clean install
To see how the test is defined see the Spring XML file
<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
http://activemq.apache.org/schema/core http://activemq.apache.org/schema/core/
activemq-core.xsd
">
<camelContext xmlns="http://camel.apache.org/schema/spring">
<route>
<!-- sends messages every 10 milliseconds -->
<from uri="dataset:myDataSet?produceDelay=10"/>
<to uri="activemq:test.queue"/>
</route>
<route>
<from uri="activemq:test.queue"/>
<to uri="dataset:myDataSet?produceDelay=10"/>
</route>
299
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
</camelContext>
<bean id="myDataSet" class="org.apache.camel.component.dataset.SimpleDataSet">
<property name="size" value="10000"/>
<property name="reportCount" value="100"/>
</bean>
<!-- lets create an embedded broker for this test -->
<broker xmlns="http://activemq.apache.org/schema/core" dataDirectory="target/
activemq">
<transportConnectors>
<transportConnector uri="tcp://localhost:61616"/>
</transportConnectors>
</broker>
<!-- Lets connect the Camel ActiveMQ component to the embedded broker.
See http://activemq.apache.org/camel/activemq.html for more information.
-->
<bean id="activemq" class="org.apache.activemq.camel.component.ActiveMQComponent">
<property name="brokerURL" value="tcp://localhost:61616" />
</bean>
</beans>
See Also
•
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
Spring Testing
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 or if a client in the same JVM as the
Camel router wants to access the routes.
URI format
direct:someName
Where someName can be any string to uniquely identify the endpoint
CH APT ER 10 - CO M PO N EN T APPEN DIX
300
Asynchronous
The Seda component provides asynchronous invocation of any consumers when a
producer sends a message exchange.
Options
Name
allowMultipleConsumers
Default
Value
Description
true
If set to false, then when a second
consumer is started on the endpoint, an
IllegalStateException is thrown
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.
See Also
•
•
•
•
•
301
Configuring Camel
Component
Endpoint
Getting Started
Seda
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
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[?option1=value[&option2=value2]]
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");
Options
Name
Default Value
Description
pattern
The Esper Pattern expression as a String to filter events
eql
The Esper EQL expression as a String to filter events
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.
CH APT ER 10 - CO M PO N EN T APPEN DIX
302
URI format
event://default
As of Camel 1.5 the name has been renamed to spring-event
spring-event://default
See Also
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
FILE COMPONENT
The File component provides access to file systems; allowing files to be processed by any other
Camel Components or messages from other components can be saved to disk.
URI format
file:fileOrDirectoryName[?options]
or
file://fileOrDirectoryName[?options]
Where fileOrDirectoryName represents the underlying file name. Camel will determine if
fileOrDirectoryName is a file or directory.
URI Options
303
Name
Default
Value
Description
consumer.initialDelay
1000
Camel 1.4: milliseconds before polling the file/directory starts
consumer.delay
500
Camel 1.4: milliseconds before the next poll of the file/directory
consumer.useFixedDelay
false
Camel 1.4: true to use fixed delay between pools, otherwise fixed rate is used. See ScheduledExecutorService
in JDK for details.
consumer.exclusiveReadLock
true
Camel 1.5: Used by FileConsumer. If set to true Camel will only poll the files if it has exclusive read lock to the
file (= the file is not in progress of being written). Camel will wait until the file lock is granted. Setting to false
Camel will poll the file even if its in progress of being written (= this is the behavior of Camel 1.4).
consumer.recursive
true/false
if a directory, will look for changes in files in all the sub directories. Notice: Default value in Camel 1.4 or
older is true. In Camel 1.5 the default value is changed to false.
consumer.regexPattern
null
will only fire a an exchange for a file that matches the regex pattern
consumer.alwaysConsume
false
Camel 1.5: @deprecated. Is used to force consuming the file even if it hasn't changed since last time it was
consumed. Is useful if you for instance move files back into a folder and the file keeps the original timestamp.
consumer.timestamp
true
Camel 1.5: @deprecated. This option is introduced to have similar name as the same option in FTP
component. Setting this option will internally in Camel set the consumer.alwaysConsume option to the !
value. So if this option is true, then alwaysConsume is false and vice verca.
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
Camel 2.x
See File2 as the File component in Camel 2.x has been greatly enhanced, and has a lot of
changes and new features.
Important Information
See the section "Common gotchas with folder and filenames" below.
Timestamp
In Camel 1.5 or older the file consumer uses an internal timestamp for last polling. This
timestamp is used to match for new or changed files: if file modified timestamp > last poll
timestamp => file can be consumed. Beware that its not persistent in any way so restarting
Camel will restart the lastpolltime variable and you can potentially consume the same file
again.
You can disable this algorithm with the new option consumer.timestamp=false
or setting the consumer.alwaysConsume=true. Camel keeps track of consumed
files which leads to a memory leak for large number of files in Camel 1.5.0 and older. This
was replaced with a LRU cache in Camel 1.6.0.
Notice: This algorithm has been marked for @deprecation and has been removed in
Camel 2.0. We strongly encourage you to use a different strategy for matching new files:
such as deleting or moving the file after processing, then new files is always if there exists a
file in the directory to poll.
Cannot move/delete file after processing on Windows
There is a potential issue on Windows platform with Camel 1.5.x. That it cannot move or delete the
file after processing. You should get an exception thrown.
The workaround is to convert the body to a String after consuming using convertBodyTo: eg
from("file://inbox").convertBodyTo(String.class).to("file://outbox");.
There should be a fix in Camel 1.6.0 to remedy this, but we would like to get feedback on this issue.
So if you are on Windows please give it a go.
consumer.generateEmptyExchangeWhenIdle
false
@deprecated. Option only for the FileConsumer. If this option is true and there was no files to process we
simulate processing a single empty file, so an exchange is fired. Note: In this situation the File attribute in
FileExchange is null.
lock
true
if true will lock the file for the duration of the processing
CH APT ER 10 - CO M PO N EN T APPEN DIX
304
delete
false
If delete is true then the file will be deleted when it is processed (the default is to move it, see below)
noop
false
If true then the file is not moved or deleted in any way (see below). This option is good for read only data, or
for ETL type requirements.
moveNamePrefix
.camel/
The prefix String perpended to the filename when moving it. For example to move processed files into the done
directory, set this value to 'done/'
moveNamePostfix
null
The postfix String appended to the filename when moving it. For example to rename processed files from foo to
foo.old set this value to '.old'
append
true
When writing do we append to the end of the file, or replace it?
autoCreate
true
If set to true Camel will create the directory to the file if the file path does not exists - Uses File#mkdirs()
bufferSize
128kb
Write buffer sized in bytes. Camel uses a default of 128 * 1024 bytes.
ignoreFileNameHeader
false
@deprecated. If this flag is enabled then producers will ignore the 'org.apache.camel.file.name' header and
generate a new dynamic filename
excludedNamePrefixes
null
@deprecated. Is used to exclude files if filename is starting with any of the given prefixes. The parameter is a
String[]
excludedNamePostfixes
null
@deprecated. Is used to exclude files if filename is ending with any of the given prefixes. The parameter is a
String[]
excludedNamePrefix
null
Camel 1.5: Is used to exclude files if filename is starting with the given prefix.
excludedNamePostfix
null
Camel 1.5: Is used to exclude files if filename is ending with the given postfix.
expression
null
Camel 1.5: Use expression to dynamically set the filename. This allows you to very easily set dynamic pattern
style filenames. If an expression is set it take precedes over the org.apache.camel.file.name header.
(Note: The header can itself also be an expression). The expression options supports both String and
Expression types. If the expression is a String type then its always evaluated using the File Language. If the
expression is an Expression type then this type is of course used as it - this allows for instance to use OGNL as
expression too.
preMoveNamePrefix
null
Camel 1.5.1/2.0: The prefix String perpended to the filename when moving it before processing. For example
to move in progress files into the inprogress directory, set this value to 'inprogress/'
preMoveNamePostfix
null
Camel 1.5.1/2.0: The postfix String appended to the filename when moving it before processing. For example
to rename in progress files from foo to foo.inprogress set this value to '.inprogress'
preMoveExpression
null
Camel 1.5.1/2.0: Use expression to dynamically set the filename when moving it before processing. For
example to move in progress file into the order directory and use ,bak as extension set this value to 'order/
${file:name.noext}.bat'
Default behavior for file consumer
• By default the file is locked for the duration of the processing.
• After the route has completed they are moved into the .camel subdirectory; so that
they appear to be deleted.
• The File Consumer will always skip any file which name starts with a dot, such as
".", ".camel", ".m2" or ".groovy".
• Only files (not directories) is matched for valid filename if options such as:
consumer.regexPattern, excludeNamePrefix,
excludeNamePostfix is used. Notice: this only works properly in Camel 1.5.0,
due to issue CAMEL-920.
Default Behavior Changed in Camel 1.5.0
In Camel 1.5 the file consumer will avoid polling files that is currently in the progress of being
written (see option consumer.exclusiveReadLock). However this requires Camel being
able to rename the file for its testing. If the Camel user hasn't this rights on the file system, you
can set this option to false to revert the change to the default behavior of Camel 1.4 or older.
The recursive option has changed its default value from true to false in Camel 1.5.0.
305
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
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://inobox?m
oveNamePrefix=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. 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.
By default Camel will move consumed files to the sub folder .camel relative where the file
was consumed.
Available in Camel 1.5.1 or newer
We have introduced a pre move operation to move files before they are processed. This
allows you to mark which files has been scanned as they are moved to this sub folder before
being processed.
The following options support pre move:
• preMoveNamePrefix
• preMoveNamePostfix
• preMoveExpression
from("file://inobox?preMoveNamePrefix=inprogress/").to("bean:handleOrder");
You can combine the pre move and the regular move:
from("file://inobox?preMoveNamePrefix=inprogress/&moveNamePrefix=../
done/").to("bean:handleOrder");
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.
Message Headers
The following message headers can be used to affect the behavior of the component
Header
Description
org.apache.camel.file.name
Specifies the output file name (relative to the
endpoint directory) to be used for the output
message when sending to the endpoint. If this is not
present and no expression either then a generated
message Id is used as filename instead.
CH APT ER 10 - CO M PO N EN T APPEN DIX
306
org.apache.camel.file.name.produced
New in Camel 1.4: 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 the name of the file that was written.
Common gotchas with folder and filenames
When Camel is producing files (writing files) there are a few gotchas 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:
ID-MACHINENAME\2443-1211718892437\1-0. Such a filename is not desired and therefore
best practice is to provide the filename in the message header "org.apache.camel.file.name".
The sample code below produces files using the message id as the filename:
from("direct:report").to("file:target/reports");
To use report.txt as the filename you have to do:
from("direct:report").setHeader(FileComponent.HEADER_FILE_NAME,
constant("report.txt")).to( "file:target/reports");
Canel will default try to auto create the folder if it does not exists, and this is a bad combination
with the UUID filename from above. So if you have:
from("direct:report").to("file:target/reports/report.txt");
And you want Camel to store in the file report.txt and autoCreate is true, then Camel will
create the folder: target/reports/report.txt/. To fix this set the autoCreate=false and create the
folder target/reports manually.
from("direct:report").to("file:target/reports/report.txt?autoCreate=false");
With auto create disabled Camel will store the report in the report.txt as expected.
File consumer, scanning for new files gotcha
This only applies to Camel 1.x
The file consumer scans for new files by keeping an internal modified timestamp of the last
consumed file. So if you copy a new file that has an older modified timestamp, then Camel will
not pickup this file. This can happen if you are testing and you copy the same file back to the
folder that has just been consumed. To remedy this modify the timestamp before copying the
file back.
307
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
Filename Expression
In Camel 1.5 we have support for setting the filename using an expression. This can be set
either using the expression option or as a string based File Language expression in the
org.apache.camel.file.name header. See the File Language for some samples.
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.
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
}
});
Body will be File object pointing to the file that was just dropped to 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 as 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 to do.
The route above using Spring DSL:
<route>
<from uri="file://inputdir/"/>
<convertBodyTo type="java.lang.String"/>
<to uri="jms:test.queue"/>
</route>
CH APT ER 10 - CO M PO N EN T APPEN DIX
308
Writing to files
Camel is of course also able to write files, eg. producing 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("seda:reports", "This is a great report");
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("seda: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");
}
}
309
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
Using expression for filenames
In this sample we want to move consumed files to a backup folder using todays date as a sub
foldername:
from("file://inbox?expression=backup/${date:now:yyyyMMdd}/${file:name}").to("...");
See File Language for more samples.
Write to subdirectory using FileComponent.HEADER_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 FileComponent.HEADER_FILE_NAME to values such as:
FileComponent.HEADER_FILE_NAME = hello.txt => /rootDirectory/hello.txt
FileComponent.HEADER_FILE_NAME = foo/bye.txt => /rootDirectory/foo/bye.txt
This allows you to have a single route to write files to multiple destinations.
See Also
•
•
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
File Language
File2
FIX
The FIX component supports the FIX protocol by using the QuickFix/J library.
URI format
fix://configurationResource
Where configurationResource points to the QuickFix/J configuration file to define how to
connect to FIX. This could be a resource on the classpath or refer to a full URL using http: or
file: schemes.
CH APT ER 10 - CO M PO N EN T APPEN DIX
310
Message Formats
By default this component will attempt to use the Type Converter to turn the inbound message
body into a QuickFix Message class and all outputs from FIX will be in the same format.
If you are using the Artix Data Services support then any payload such as files or streams or
byte arrays can be converted nicely into FIX messages.
Using camel-fix
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-parent</artifactId>
<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>
See Also
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
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.
311
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
URI format
flatpack:[delim|fixed]:flatPackConfig.pzmap.xml
or for a delimited file handler with no configuration file just use
flatpack:someName
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
URI Options
Name
Default
Value
Description
delimiter
','
The default character delimiter for delimited files
textQualifier
'"'
The text qualifier 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.
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 have
converters for java.util.Map or java.util.List.
Usually you want the Map if you process one row at a time (splitRows=true). And the List for
CH APT ER 10 - CO M PO N EN T APPEN DIX
312
the entire content (splitRows=false), where each element in the list is a Map.
Each Map contain 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 is supported. However it is
required that you must use fixed record id names:
• header for the header record (must be lowercase)
• trailer for the trailer record (must be lowercase)
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>
313
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
<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)
• unmarshal = from java.io.InputStream (such as a File, 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 (; , or the likes)
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"));
CH APT ER 10 - CO M PO N EN T APPEN DIX
314
...
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 converts 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
FTP/SFTP COMPONENT
This component provides access to remote file systems over the FTP and SFTP protocols.
URI format
ftp://[username@]hostname[:port]/filename[?options]
sftp://[username@]hostname[:port]/filename[?options]
315
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
Where filename represents the underlying file name or directory. Can contain nested folders.
The username is currently only possible to provide in the hostname parameter.
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)
Examples
ftp://someone@someftpserver.com/public/upload/images/
holiday2008?password=secret&binary=true
ftp://someoneelse@someotherftpserver.co.uk:12049/reports/2008/
budget.txt?password=secret&binary=false&directory=false
ftp://publicftpserver.com/download
URI Options
Name
Default
Value
Description
directory
true
indicates whether or not the given file name should be interpreted by default as a directory or file (as it sometimes hard to
be sure with some FTP servers)
password
null
specifies the password to use to login to the remote file system
binary
false
specifies the file transfer mode BINARY or ASCII. Default is ASCII.
ftpClientConfig
null
Camel 1.5: Reference to a bean in the registry as a org.apache.commons.net.ftp.FTPClientConfig class. Use
this option if you need to configure the client according to the FTP Server date format, locale, timezone, platform etc. See
the javadoc FTPClientConfig for more documentation.
consumer.recursive
true/false
if a directory, will look for changes in files in all the sub directories. Is true as default for Camel 1.4 or older. Will change to
false as default value as of Camel 1.5
consumer.setNames
true
@deprecated Used by FTPConsumer. If true Camel will use the filename the file has on the FTP server. The filename is
stored on the IN message in the header FileComponent.HEADER_FILE_NAME. Note: In Camel 1.4 the default value
has changed to true.
consumer.delay
500
Delay in millis between each poll
consumer.initialDelay
1000
Millis before polling starts
consumer.userFixedDelay
false
true to use fixed delay between pools, otherwise fixed rate is used. See ScheduledExecutorService in JDK for details.
consumer.regexPattern
null
Used by FTPConsumer. Regular expression to use for matching files when consuming.
consumer.exclusiveReadLock
false
Camel 1.5: Used by FTPConsumer. If set to true Camel will only poll the ftp files if it has exclusive read to the file (= the file
is not in progress of being written). Camel will wait until it is granted, testing once every second. The test is implemented by
Camel will try to rename the file. Setting to false Camel will poll the file even if its in progress of being written.
consumer.deleteFile
false
Camel 1.5: Used by FTPConsumer. Flag to set if the consumed file should be deleted after it has been downloaded.
consumer.moveNamePrefix
null
Camel 1.5: Used by FTPConsumer. The prefix String perpended to the filename when moving it. For example to move
processed files into the done directory, set this value to 'done/'
consumer.moveNamePostfix
null
Camel 1.5: Used by FTPConsumer. The postfix String appended to the filename when moving it. For example to rename
processed files from foo to foo.old set this value to '.old'
consumer.excludedNamePrefix
null
Camel 1.5: Used by FTPConsumer. Is used to exclude files if filename is starting with the given prefix.
consumer.excludedNamePostfix
null
Camel 1.5: Used by FTPConsumer. Is used to exclude files if filename is ending with the given postfix.
consumer.timestamp
false
Camel 1.5: @deprecated will be removed in Camel 2.0. This option is only for backwards comparability.
expression
null
Camel 1.5: Use expression to dynamically set the filename. This allows you to very easily set dynamic pattern style filenames.
If an expression is set it take precedes over the org.apache.camel.file.name header. (Note: The header can itself
also be an expression). The expression options supports both String and Expression types. If the expression is a String type
then its always evaluated using the File Language. If the expression is an Expression type then this type is of course used as
it - this allows for instance to use OGNL as expression too.
passiveMode
false
Camel 1.5.1/2.0: Set whether to use passive mode connections. Default is active. This feature is only for regular FTP, not
SFTP.
CH APT ER 10 - CO M PO N EN T APPEN DIX
316
Camel 2.x
See FTP2 as the File component in Camel 2.x has been greatly enhanced, and has a lot of
changes and new features.
Timestamp
In Camel 1.4 or older the FTP consumer uses an internal timestamp for last polling. This
timestamp is used to match for new remote files: if remote file modified timestamp > last
poll timestamp => file can be consumed.
In Camel 1.5 this algorithm has been disabled by default as its not reliable over the FTP
protocol. FTP Servers only return file modified timestamps using HH:mm (not seconds).
And of course the clocks between the client and server can also be out of sync. Bottom
line is that timestamp check for FTP protocol should not be used. That is why this feature
is marked as @deprecated and will be removed in Camel 2.0.
We encourage you to use a different strategy for matching new remote files: such as
deleting or moving the file after download.
More examples
This component is an extension of the File component. So there could be more samples
and details on the File component page as well.
knownHosts
null
Camel 1.5.1/2.0: Sets the known_hosts file so that the SFTP endpoint can do host key verification.
privateKeyFile
null
Camel 1.5.1/2.0: Set the private key file to that the SFTP endpoint can do private key verification.
privateKeyFilePassphrase
null
Camel 1.5.1/2.0: Set the private key file passphrase to that the SFTP endpoint can do private key verification.
New default behavior for FTP/SFTP-Consumers in Camel 1.5
The consumer will always skip any file which name starts with a dot, such as ".",
".camel", ".m2" or ".groovy". Only files (not directories) is matched for valid
filename if options such as: consumer.regexPattern,
consumer.excludeNamePrefix, consumer.excludeNamePostfix is used.
The consumer recursive option will be changed from true to false as the default value.
We don't feel that Camel out-of-the-box should recursive poll.
317
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
The consumer will not use timestamp algorithm for determine if a remote file is a new file see warning section above. To use the old behavior of Camel 1.4 or older you can use the
option consumer.timestamp=true.
Exclusive Read Lock
The option readLock can be used to force Camel not to consume files that is currently in
the progress of being written. However this option is default turned off, as it requires that the
user has write access. There are other solutions to avoid consuming files that are currently
being written over FTP, for instance you can write the a temporary destination and move the
file after it has been written.
Message Headers
The following message headers can be used to affect the behavior of the component
Header
Description
org.apache.camel.file.name
Specifies the output file name (relative to the
endpoint directory) to be used for the output
message when sending to the endpoint. If this is not
present and no expression either then a generated
message Id is used as filename instead.
org.apache.camel.file.name.produced
New in Camel 1.5: 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 the name of the file that was written.
org.apache.camel.file.total
Camel 2.0: Current index out of total number of files
being consumed in this batch.
org.apache.camel.file.index
Camel 2.0: Total number of files being consumed in
this batch.
file.remote.host
The hostname of the remote server
file.remote.name
The name of the file consumed from the remote
server
file.remote.fullName
The fullname of the file consumed from the remote
server
Consumer properties
When using FTPConsumer (downloading files from a FTP Server) the consumer specific
properties from the File component should be prefixed with "consumer.". For example the
CH APT ER 10 - CO M PO N EN T APPEN DIX
318
delay option from File Component should be specified as "consumer.delay=30000" in the URI.
See the samples or some of the unit tests of this component.
Filename Expression
In Camel 1.5 we have support for setting the filename using an expression. This can be set
either using the expression option or as a string based File Language expression in the
org.apache.camel.file.name header. See the File Language for some samples.
Camel 1.x Known issues
See the timestamp warning.
When consuming files (downloading) you must use type conversation to either String or to
InputStream for ASCII and BINARY file types.
In Camel 1.4 this is fixed, as there are build in type converters for the ASCII and BINARY file
types, meaning that you do not need the convertBodyTo expression.
In Camel 1.4 or below Camel FTPConsumer will poll files regardless if the file is currently
being written. See the consumer.exclusiveReadLock option.
Also in Camel 1.3 since setNames is default false then you must explicitly set the filename
using the setHeader expression when consuming from FTP directly to File.
The code below illustrates this:
private String ftpUrl =
"ftp://camelrider@localhost:21/public/downloads?password=admin&binary=false";
private String fileUrl = "file:myfolder/?append=false&noop=true";
return new RouteBuilder() {
public void configure() throws Exception {
from(ftpUrl).setHeader(FileComponent.HEADER_FILE_NAME,
constant("downloaded.txt")).convertBodyTo(String.class).to(fileUrl);
}
};
Or you can set the option to true as illustrated below:
private String ftpUrl =
"ftp://camelrider@localhost:21/public/downloads?password=admin&binary=false&consumer.setNames=true";
private String fileUrl = "file:myfolder/?append=false&noop=true";
return new RouteBuilder() {
public void configure() throws Exception {
from(ftpUrl).convertBodyTo(String.class).to(fileUrl);
}
};
319
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
Sample
In the sample below we setup Camel to download all the reports from the FTP server once
every hour (60 min) as BINARY content and store it as files on the local file system.
protected RouteBuilder createRouteBuilder() throws Exception {
return new RouteBuilder() {
public void configure() throws Exception {
// we use a delay of 60 minutes (eg. once pr. hour we poll the FTP server
long delay = 60 * 60 * 1000L;
// from the given FTP server we poll (= download) all the files
// from the public/reports folder as BINARY types and store this as files
// in a local directory. Camel will use the filenames from the FTPServer
//
"consumer." in
//
consumer.delay
//
Component.
notice that the FTPConsumer properties must be prefixed with
the URL
the delay parameter is from the FileConsumer component so we should use
as
the URI parameter name. The FTP Component is an extension of the File
from("ftp://scott@localhost/public/reports?password=tiger&binary=true&consumer.delay="
+ delay).
to("file://target/test-reports");
}
};
}
And the route using Spring DSL:
<route>
<from uri="ftp://scott@localhost/public/
reports?password=tiger&amp;binary=true&amp;consumer.delay=60000"/>
<to uri="file://target/test-reports"/>
</route>
Using expression for filenames
In this sample we want to move consumed files to a backup folder using today's date as a sub
foldername. Notice that the move happens on the remote FTP server. If you want to store the
downloaded file on your local disk then route it to the File component as the sample above
illustrates.
from(ftpUrl + "&expression=backup/${date:now:yyyyMMdd}/${file:name}").to("...");
See File Language for more samples.
CH APT ER 10 - CO M PO N EN T APPEN DIX
320
Consuming a remote FTP server triggered by a route
The FTP consumer is build as a scheduled consumer to be used in the from route. However if
you want to start consuming from a FTP server triggered within a route it's a bit cumbersome
to do this in Camel 1.x (we plan to improve this in Camel 2.x). However it's possible as this
code below demonstrates.
In the sample we have a Seda queue where a message arrives that holds a message
containing a filename to poll from a remote FTP server. So we setup a basic FTP url as:
// we use delay=5000 to use 5 sec delay between pools to avoid polling a second time
before we stop the consumer
// this is because we only want to run a single poll and get the file
private String getFtpUrl() {
return "ftp://admin@localhost:" + getPort() +
"/getme?password=admin&binary=false&delay=5000";
}
And then we have the route where we use Processor within the route so we can use Java code.
In this Java code we create the ftp consumer that downloads the file we want. And after the
download we can get the content of the file and put it in the original exchange that continues
being routed. As this is based on an unit test it routes to a Mock endpoint.
from("seda:start").process(new Processor() {
public void process(final Exchange exchange) throws Exception {
// get the filename from our custome header we want to get from a remote server
String filename = exchange.getIn().getHeader("myfile", String.class);
// construct the total url for the ftp consumer
// add the fileName option with the file we want to consume
String url = getFtpUrl() + "&fileName=" + filename;
// create a ftp endpoint
Endpoint ftp = context.getEndpoint(url);
// create a polling consumer where we can poll the myfile from the ftp server
PollingConsumer consumer = ftp.createPollingConsumer();
// must start the consumer before we can receive
consumer.start();
// poll the file from the ftp server
Exchange result = consumer.receive();
// the result is the response from the FTP consumer (the downloaded file)
// replace the outher exchange with the content from the downloaded file
exchange.getIn().setBody(result.getIn().getBody());
// stop the consumer
consumer.stop();
}
}).to("mock:result");
321
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
Debug logging
This component has log level TRACE that can be helpful if you have problems.
See Also
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
HIBERNATE COMPONENT
The hibernate: component allows you to work with databases using Hibernate as the object
relational mapping technology to map POJOs to database tables. The camel-hibernate
library is provided by the Camel Extra project which hosts all *GPL related components for
Camel.
Sending to the endpoint
Sending POJOs to the hibernate endpoint inserts entities into the database. The body of the
message is assumed to be an entity bean that you have mapped to a relational table using the
hibernate .hbm.xml files.
If the body does not contain an entity bean then use a Message Translator in front of the
endpoint to perform the necessary conversion first.
Consuming from the endpoint
Consuming messages removes (or updates) entities in the database. This allows you to use a
database table as a logical queue, consumers take messages from the queue and then delete/
update them to logically remove them from the queue.
If you do not wish to delete the entity when it has been processed you can specify
consumeDelete=false on the URI. This will result in the entity being processed each poll.
If you would rather perform some update on the entity to mark it as processed (such as to
exclude it from a future query) then you can annotate a method with @Consumed which will
be invoked on your entity bean when the entity bean is consumed.
URI format
hibernate:[entityClassName]
For sending to the endpoint, the entityClassName is optional. If specified it is used to help
use the [Type Conversion] to ensure the body is of the correct type.
CH APT ER 10 - CO M PO N EN T APPEN DIX
322
For consuming the entityClassName is mandatory.
Options
Name
Default
Value
Description
entityType
entityClassName
Is the provided entityClassName from the
URI
consumeDelete
true
Option for HibernateConsumer only.
Enables / disables whether or not the entity
is deleted after it is consumed.
true
Option for HibernateConsumer only.
Enables / disables whether or not to use
exclusive locking of each entity while
processing the results from the pooling.
true
Option for HibernateProducer only. Flushes
the EntityManager after the entity beans has
been persisted.
maximumResults
-1
Option for HibernateConsumer only. Set
the maximum number of results to retrieve
on the Query.
consumer.delay
500
Option for HibernateConsumer only. Delay
in millis between each poll.
consumer.initialDelay
1000
Option for HibernateConsumer only. Millis
before polling starts.
false
Option for HibernateConsumer only. true
to use fixed delay between pools, otherwise
fixed rate is used. See
ScheduledExecutorService in JDK for
details.
consumeLockEntity
flushOnSend
consumer.userFixedDelay
See Also
•
•
•
•
323
Configuring Camel
Component
Endpoint
Getting Started
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
HL7 COMPONENT
The hl7 component is used for working with the HL7 MLLP protocol and the HL7 model using
the HAPI library.
This component supports the following:
• HL7 MLLP codec for Mina
• Agnostic data format using either plain String objects or HAPI HL7 model objects.
• Type Converter from/to HAPI and String
• HL7 DataFormat using HAPI library
• Even more easy-of-use as its integrated well with the camel-mina component.
HL7 MLLP protocol
HL7 is often used with the HL7 MLLP protocol that is a text based TCP socket based protocol.
This component ships with a Mina Codec that conforms to the MLLP protocol so you can easily
expose a HL7 listener that accepts HL7 requests over the TCP transport.
To expose a HL7 listener service we reuse the existing camel-mina component where we
just use the HL7MLLPCodec as codec.
The HL7 MLLP codec has the following options:
Name
Default
Value
Description
startByte
0x0b
The start byte spanning the HL7 payload. Is the HL7 default
value of 0x0b (11 decimal)
endByte1
0x1c
The first end byte spanning the HL7 payload. Is the HL7
default value of 0x1c (28 decimal)
endByte2
0x0d
The 2nd end byte spanning the HL7 payload. Is the HL7
default value of 0x0d (13 decimal)
charset
JVM
Default
The encoding (is a charset name) to use for the codec. If not
provided Camel will use the JVM default Charset.
convertLFtoCR
true
Will convert \n to \r (0x0d, 13 decimal) as HL7 usually uses \r
as segment terminators. The HAPI library requires to use \r.
Exposing a HL7 listener
In our spring xml file we configure an endpoint to listen for HL7 requests using TCP:
<endpoint id="hl7listener"
uri="mina:tcp://localhost:8888?sync=true&amp;codec=hl7codec"/>
Notice we configure it to use camel-mina with TCP on the localhost on port 8888. We use the
sync=true to indicate that this listener is synchronous and therefore will return a HL7
CH APT ER 10 - CO M PO N EN T APPEN DIX
324
response to the caller. Then we setup mina to use our HL7 codec with codec=hl7codec.
Notice that hl7codec is just a spring bean id, so we could have named it
mygreatcodecforhl7 or whatever. The codec is also setup in the spring xml file:
<bean id="hl7codec" class="org.apache.camel.component.hl7.HL7MLLPCodec">
<property name="charset" value="iso-8859-1"/>
</bean>
And here we configure the charset encoding to use, and iso-8859-1 is commonly used.
The endpoint hl7listener can then be used in a route as a consumer, as this java DSL
example illustrates:
from("hl7socket").to("patientLookupService");
This is a very simple route that will listen for HL7 and route it to a service named
patientLookupService that is also a spring bean id we have configured in the spring xml as:
<bean id="patientLookupService"
class="com.mycompany.healtcare.service.PatientLookupService"/>
And another powerful feature of Camel is that we can have our busines logic in POJO classes
that is not at all tied to Camel as shown here:
public class PatientLookupService {
public Message lookupPatient(Message input) throws HL7Exception {
QRD qrd = (QRD)input.get("QRD");
String patientId = qrd.getWhoSubjectFilter(0).getIDNumber().getValue();
// find patient data based on the patient id and create a HL7 model object
with the response
Message response = ... create and set response data
return response
}
Notice that this class is just using imports from the HAPI library and none from Camel.
HL7 Model using java.lang.String
The HL7MLLP codec uses plain String as data format. And Camel uses Type Converter to
convert from/to Strings to the HAPI HL7 model objects. However you can use the plain String
objects if you would like to, for instance if you need to parse the data yourself.
See samples for such an example.
HL7 Model using HAPI
The HL7 model is Java objects from the HAPI library. Using this library we can encode and
decode from the EDI format (ER7) that is mostly used with HL7.
With this model you can code with Java objects instead of the EDI based HL7 format that can
be hard for humans to read and understand.
The ER7 sample below is a request to lookup a patient with the patient id 0101701234.
325
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
MSH|^~\\&|MYSENDER|MYRECEIVER|MYAPPLICATION||200612211200||QRY^A19|1234|P|2.4
QRD|200612211200|R|I|GetPatient|||1^RD|0101701234|DEM||
Using the HL7 model we can work with the data as a
ca.uhn.hl7v2.model.Message.Message object.
To retrieve the patient id for the patient in the ER7 above you can do this in java code:
Message msg = exchange.getIn().getBody(Message.class);
QRD qrd = (QRD)msg.get("QRD");
String patientId = qrd.getWhoSubjectFilter(0).getIDNumber().getValue();
Camel has build in type converters so when this operation is invoked:
Message msg = exchange.getIn().getBody(Message.class);
Camel will converter the received HL7 data from String to the Message object. This is powerful
when combined with the HL7 listener, then you as the end-user don't have to work with byte[],
String or any other simple object formats. You can just use the HAPI HL7 model objects.
HL7 DATAFORMAT
The HL7 component ships with a HL7 dataformat 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:
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");
CH APT ER 10 - CO M PO N EN T APPEN DIX
326
Message Headers
The unmarshal operation adds these MSH fields as headers on the Camel message:
Camel 1.x
Key
MSH field
Example
hl7.msh.sendingApplication
MSH-3
MYSERVER
hl7.msh.sendingFacility
MSH-4
MYSERVERAPP
hl7.msh.receivingApplication
MSH-5
MYCLIENT
hl7.msh.receivingFacility
MSH-6
MYCLIENTAPP
hl7.msh.timestamp
MSH-7
20071231235900
hl7.msh.security
MSH-8
null
hl7.msh.messageType
MSH-9-1
ADT
hl7.msh.triggerEvent
MSH-9-2
A01
hl7.msh.messageControl
MSH-10
1234
hl7.msh.processingId
MSH-11
P
hl7.msh.versionId
MSH-12
2.4
Camel 2.0
327
Key
MSH field
Example
CamelHL7SendingApplication
MSH-3
MYSERVER
CamelHL7SendingFacility
MSH-4
MYSERVERAPP
CamelHL7ReceivingApplication
MSH-5
MYCLIENT
CamelHL7ReceivingFacility
MSH-6
MYCLIENTAPP
CamelHL7Timestamp
MSH-7
20071231235900
CamelHL7Security
MSH-8
null
CamelHL7MessageType
MSH-9-1
ADT
CamelHL7TriggerEvent
MSH-9-2
A01
CamelHL7MessageControl
MSH-10
1234
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
CamelHL7ProcessingId
MSH-11
P
CamelHL7VersionId
MSH-12
2.4
All headers are String types. If a header value is missing its value is null.
Dependencies
To use HL7 in your camel routes you need to add the a dependency on camel-hl7 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-hl7</artifactId>
<version>1.6.0</version>
</dependency>
SAMPLES
In the following example we send a HL7 request to a HL7 listener and retrieves a response. We
use plain String types in this example:
String line1 =
"MSH|^~\\&|MYSENDER|MYRECEIVER|MYAPPLICATION||200612211200||QRY^A19|1234|P|2.4";
String line2 = "QRD|200612211200|R|I|GetPatient|||1^RD|0101701234|DEM||";
StringBuffer in = new StringBuffer();
in.append(line1);
in.append("\n");
in.append(line2);
String out =
(String)template.requestBody("mina:tcp://127.0.0.1:8888?sync=true&codec=#hl7codec",
in.toString());
In the next sample we want to route HL7 requests from our HL7 listener to our business logic.
We have our business logic in a plain POJO that we have registered in the registry as
hl7service = for instance using Spring and letting the bean id = hl7service.
Our business logic is a plain POJO only using the HAPI library so we have these operations
defined:
public class MyHL7BusinessLogic {
// This is a plain POJO that has NO imports whatsoever on Apache Camel.
// its a plain POJO only importing the HAPI library so we can much easier work
with the HL7 format.
public Message handleA19(Message msg) throws Exception {
CH APT ER 10 - CO M PO N EN T APPEN DIX
328
// here you can have your business logic for A19 messages
assertTrue(msg instanceof QRY_A19);
// just return the same dummy response
return createADR19Message();
}
public Message handleA01(Message msg) throws Exception {
// here you can have your business logic for A01 messages
assertTrue(msg instanceof ADT_A01);
// just return the same dummy response
return createADT01Message();
}
}
Then we setup the Camel routes using the RouteBuilder as:
DataFormat hl7 = new HL7DataFormat();
// we setup or HL7 listener on port 8888 (using the hl7codec) and in sync mode so we
can return a response
from("mina:tcp://127.0.0.1:8888?sync=true&codec=#hl7codec")
// we use the HL7 data format to unmarshal from HL7 stream to the HAPI Message
model
// this ensures that the camel message has been enriched with hl7 specific headers
to
// make the routing much easier (see below)
.unmarshal(hl7)
// using choice as the content base router
.choice()
// where we choose that A19 queries invoke the handleA19 method on our
hl7service bean
.when(header("CamelHL7TriggerEvent").isEqualTo("A19"))
.beanRef("hl7service", "handleA19")
.to("mock:a19")
// and A01 should invoke the handleA01 method on our hl7service bean
.when(header("CamelHL7TriggerEvent").isEqualTo("A01")).to("mock:a01")
.beanRef("hl7service", "handleA01")
.to("mock:a19")
// other types should go to mock:unknown
.otherwise()
.to("mock:unknown")
// end choice block
.end()
// marhsal response back
.marshal(hl7);
Notice that we use the HL7 DataFormat to enrich our Camel Message with the MSH fields
preconfigued on the Camel Message. This let us much more easily define our routes using the
fluent builders.
If we do not use the HL7 DataFormat then we do not gains these headers and we must resort
to a different technique for computing the MSH trigger event (= what kind of HL7 message it
is). This is a big advantage of the HL7 DataFormat over the plain HL7 type converters.
329
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
Sample using plain String objects
In this sample we use plain String objects as the data format, that we send, process and receive.
As the sample is part of an unit test there is some code for assertions, but you should be able
to understand what happens. First we send the plain String Hello World to the HL7MLLPCodec
and receives the response that is also just plain string as we receive Bye World.
MockEndpoint mock = getMockEndpoint("mock:result");
mock.expectedBodiesReceived("Bye World");
// send plain hello world as String
Object out =
template.requestBody("mina:tcp://127.0.0.1:8888?sync=true&codec=#hl7codec", "Hello
World");
assertMockEndpointsSatisfied();
// and the response is also just plain String
assertEquals("Bye World", out);
Here we process the incoming data as plain String and send the response also as plain String:
from("mina:tcp://127.0.0.1:8888?sync=true&codec=#hl7codec")
.process(new Processor() {
public void process(Exchange exchange) throws Exception {
// use plain String as message format
String body = exchange.getIn().getBody(String.class);
assertEquals("Hello World", body);
// return the response as plain string
exchange.getOut().setBody("Bye World");
}
})
.to("mock:result");
See Also
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
HTTP COMPONENT
The http: component provides HTTP based endpoints for consuming external HTTP
resources (as a client to call external servers using HTTP).
URI format
http:hostname[:port][/resourceUri][?options]
CH APT ER 10 - CO M PO N EN T APPEN DIX
330
Will default use port 80 for http and 443 for https.
Options
Default
Value
Description
true
Camel 2.0: Option to disable throwing the HttpOperationFailedExc
in case of failed responses from the remote server. This allows you to
responses regardles of the HTTP status code.
httpBindingRef
null
Reference to a
org.apache.camel.component.http.HttpBinding in the
Registry.
username
null
Username for basic http authentication.
password
null
Password for basic http authentication.
httpClientConfigurerRef
null
Reference to a
org.apache.camel.component.http.HttpClientConfi
in the Registry.
httpClient.XXX
null
Setting options on the HttpClientParams. For instance
httpClient.soTimeout(5000) will set the SO_TIMEOUT to 5 seconds.
Name
throwExceptionOnFailure
Message Headers
Camel 1.x
331
Name
Type
Description
HttpProducer.HTTP_URI
String
Camel 1.5.1: URI to call. Will
override existing URI set directly on
the endpoint. Is set on the IN message.
HttpProducer.HTTP_RESPONSE_CODE
int
The http response code from the
external server. Is 200 for OK. Is set
on the OUT message.
HttpProducer.QUERY
String
URI parameters. Will override existing
URI parameters set directly on the
endpoint. Is set on the IN message.
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
camel-http vs camel-jetty
You can only produce to endpoints generated by the HTTP component. Therefore it
should never be used as input into your camel Routes. To bind/expose an HTTP endpoint
via a http server as input to a camel route, you can use the Jetty Component
Camel 2.0
Name
Type
Description
HttpConstants.HTTP_URI
String
URI to call. Will override
existing URI set directly on
the endpoint. Is set on the
IN message.
HttpConstants.HTTP_PATH
String
Request URI's path. Is set on
the IN message.
HttpConstants.HTTP_QUERY
String
URI parameters. Will
override existing URI
parameters set directly on
the endpoint. Is set on the
IN message.
HttpConstants.HTTP_CHARACTER_ENCODING
String
Character encoding. Is set on
the IN message.
HttpConstants.HTTP_CONTENT_TYPE
String
Content type. Is set on the
IN message.
int
The http response code
from the external server. Is
200 for OK. Is set on the
OUT message.
HttpConstants.HTTP_RESPONSE_CODE
Message Body
Camel will store the http response from the external server on the OUT body. All headers
from the IN message will be copied to the OUT message so headers is preserved during
routing.
Additionally Camel will add the http response headers as well to the OUT message.
Response code
Camel will handle according to the http response code:
CH APT ER 10 - CO M PO N EN T APPEN DIX
332
• response code is between 100..299 then Camel regard it as a success response
• response code is between 300..399 then Camel regard it as a redirection was
returned and will throw a HttpOperationFailedException with the information
• response code is 400+ then Camel regard it as a external server failure and will throw
a HttpOperationFailedException with the information
HttpOperationFailedException
This exception contains the following information
• the http status code
• the http status line (text of the status code)
• redirect location if server returned a redirect
• responseBody as a java.io.InputStream if server provided a body as response
Calling using GET or POST
In Camel 1.5 the following algorithm is used to determine if either GET or POST http
method should be used:
1. Use method provided in header
2. GET is query string is provided in header
3. GET if endpoint is configured with a query string
4. POST if there is data to send (body is not null)
5. GET otherwise
Configuring URI to call
You can set the http producer's URI directly form the endpoint URI. In the route below Camel
will call our to the external server oldhost using HTTP.
from("direct:start")
.to("http://oldhost");
And the equivalent spring sample:
<camelContext xmlns="http://activemq.apache.org/camel/schema/spring">
<route>
<from uri="direct:start"/>
<to uri="http://oldhost"/>
</route>
</camelContext>
In Camel 1.5.1 you can override the http endpoint URI by adding a header with the key
HttpProducer.HTTP_URI on the message.
from("direct:start")
.setHeader(org.apache.camel.component.http.HttpProducer.HTTP_URI,
constant("http://newhost"))
.to("http://oldhost");
333
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
throwExceptionOnFailure
The option throwExceptionOnFailure can be set to false to prevent the
HttpOperationFailedException to be thrown for failed response codes. This allows you to
get any response from the remote server.
There is a sample below demonstrating this.
In the sample above Camel will call the http://newhost despite the endpoint is configured with
http://oldhost.
And the same code in Camel 2.0:
from("direct:start")
.setHeader(HttpConstants.HTTP_URI, constant("http://newhost"))
.to("http://oldhost");
Where Constants is the class org.apache.camel.component.http.Constants.
Configuring URI Parameters
The http producer supports URI parameters to be sent to the HTTP server. The URI
parameters can either be set directly on the endpoint URI or as a header with the key
HttpProducer.QUERY on the message.
from("direct:start")
.to("http://oldhost?order=123&detail=short");
Or options provided in a header:
from("direct:start")
.setHeader(HttpConstants.HTTP_QUERY, constant("order=123&detail=short"))
.to("http://oldhost");
How to set the http method (GET/POST/PUT/DELETE/HEAD/OPTIONS/
TRACE) to the HTTP producer
The HTTP component provides a way to set the HTTP request method by setting the message
header. Here is an example;
from("direct:start")
.setHeader(HttpConstants.HTTP_METHOD,
constant(org.apache.camel.component.http.HttpMethods.POST))
.to("http://www.google.com")
.to("mock:results");
The method can be written a bit shorter using the string constants:
.setHeader("CamelHttpMethod", constant("POST"))
And the equivalent spring sample:
CH APT ER 10 - CO M PO N EN T APPEN DIX
334
<camelContext xmlns="http://activemq.apache.org/camel/schema/spring">
<route>
<from uri="direct:start"/>
<setHeader headerName="CamelHttpMethod">
<constant>POST</constant>
</setHeader>
<to uri="http://www.google.com"/>
<to uri="mock:results"/>
</route>
</camelContext>
Configuring charset
If you are using POST to send data you can configure the charset using the Exchange property:
exchange.setProperty(Exchange.CHARSET_NAME, "iso-8859-1");
Or the HttpClient options: httpClient.contentCharset=iso-8859-1
Sample with scheduled poll
The sample polls the Google homepage every 10 seconds and write the page to the file
message.html
from("timer://foo?fixedRate=true&delay=0&period=10000")
.to("http://www.google.com")
.setHeader(FileComponent.HEADER_FILE_NAME, "message.html").to("file:target/
google");
URI Parameters from the endpoint URI
In this sample we have the complete URI endpoint that is just what you would have typed in a
web browser. Multiple URI parameters can of course be set using the & as separator, just as
you would in the web browser. Camel does no tricks here.
// we query for Camel at the Google page
template.sendBody("http://www.google.com/search?q=Camel", null);
URI Parameters from the Message
Map headers = new HashMap();
headers.put(HttpProducer.QUERY, "q=Camel&lr=lang_en");
// we query for Camel and English language at Google
template.sendBody("http://www.google.com/search", null, headers);
In the header value above notice that it should not be prefixed with ? and you can separate
parameters as usual with the & char.
335
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
Getting the Response Code
You can get the http response code from the http component by getting the value from out
message header with HttpProducer.HTTP_RESPONSE_CODE.
Exchange exchange = template.send("http://www.google.com/search", new Processor() {
public void process(Exchange exchange) throws Exception {
exchange.getIn().setHeader(HttpProducer.QUERY,
constant("hl=en&q=activemq"));
}
});
Message out = exchange.getOut();
int responseCode = out.getHeader(HttpProducer.HTTP_RESPONSE_CODE, Integer.class);
Using throwExceptionOnFailure=false to get any response back
Available as of Camel 2.0
In the route below we want to route a message that we enrich with data returned from a
remote HTTP call. As we want any response from the remote server we set the
throwExceptionOnFailure option to false so we get any response in the
AggregationStrategy. As the code is based on an unit test that simulates a http status
code 404, there is some assertion code etc.
// We set throwExceptionOnFailure to false to let Camel return any response from the
remove HTTP server without thrown
// HttpOperationFailedException in case of failures.
// This allows us to handle all responses in the aggregation strategy where we can
check the HTTP response code
// and decide what to do. As this is based on an unit test we assert the code is 404
from("direct:start").enrich("http://localhost:8222/
myserver?throwExceptionOnFailure=false&user=Camel", new AggregationStrategy() {
public Exchange aggregate(Exchange original, Exchange resource) {
// get the response code
Integer code = resource.getOut().getHeader(Exchange.HTTP_RESPONSE_CODE,
Integer.class);
assertEquals(404, code.intValue());
return resource;
}
}).to("mock:result");
// this is our jetty server where we simulate the 404
from("jetty://http://localhost:8222/myserver")
.process(new Processor() {
public void process(Exchange exchange) throws Exception {
exchange.getOut().setBody("Page not found");
exchange.getOut().setHeader(Exchange.HTTP_RESPONSE_CODE, 404);
}
});
CH APT ER 10 - CO M PO N EN T APPEN DIX
336
Advanced Usage
If you need more control over the http producer you should use the HttpComponent where
you can set various classes to give you custom behavior.
Setting MaxConnectionsPerHost
The Http Component have a
org.apache.commons.httpclient.HttpConnectionManager where you can
configure various global configuration for the given component.
By global, we mean, that any endpoint the component creates has the same shared
HttpConnectionManager. So if we want to set a different value for the max connection per
host, we need to define on the http component and not on the endpoint URI that we usually
uses. So here comes:
First we define the http component in spring XML. Yes we can use the same scheme name
http that Camel otherwise will auto discover and create the component with default settings.
What we need is to overrule this so we can set our options. In the sample below we set the
max connection to 5 instead of the default of 2.
<bean id="http" class="org.apache.camel.component.http.HttpComponent">
<property name="camelContext" ref="camel"/>
<property name="httpConnectionManager" ref="myHttpConnectionManager"/>
</bean>
<bean id="myHttpConnectionManager"
class="org.apache.commons.httpclient.MultiThreadedHttpConnectionManager">
<property name="params" ref="myHttpConnectionManagerParams"/>
</bean>
<bean id="myHttpConnectionManagerParams"
class="org.apache.commons.httpclient.params.HttpConnectionManagerParams">
<property name="defaultMaxConnectionsPerHost" value="5"/>
</bean>
And then we can just use it as we normally do in our routes:
<camelContext id="camel" xmlns="http://camel.apache.org/schema/spring" trace="true">
<route>
<from uri="direct:start"/>
<to uri="http://www.google.com"/>
<to uri="mock:result"/>
</route>
</camelContext>
See Also
• Configuring Camel
• Component
• Endpoint
337
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
• Getting Started
• Jetty
IBATIS
The ibatis: component allows you to query, poll, insert, update and delete data in a relational
database using Apache iBATIS.
URI format
ibatis:statementName[?options]
Where statementName is the name in the iBATIS XML configuration file which maps to
the query, insert, update or delete operation you wish to evaluate.
Options
Option
consumer.onConsume
consumer.useIterator
consumer.routeEmptyResultSet
Type
String
Boolean
Boolean
Default
Description
null
Statements to run after
consuming. Can be used to
eg. update rows after they
have been consumed and
processed in Camel. See
sample later. Multiple
statements can be separated
with comma.
true
If true each row returned
when polling will be
processed individually. If
false the entire List of data
is set as the IN body.
false
Camel 2.0: Sets whether
empty resultset should be
routed or not. By default
empty result sets are not
routed.
CH APT ER 10 - CO M PO N EN T APPEN DIX
338
statementType
StatementType
Camel 1.6.1/2.0:
Mandatory to specify for
IbatisProducer to control
which iBatis
SqlMapClient method
to invoke. The enum values
are: QueryForObject,
QueryForList, Insert,
Update, Delete.
null
Message Headers
Camel will populate the result message, either IN or OUT with a header with the
operationName used:
Header
Type
Description
org.apache.camel.ibatis.queryName
String
Camel 1.x: The
statementName used (for
example: insertAccount)
CamelIBatisStatementName
String
Camel 2.0: The
statementName used (for
example: insertAccount)
Samples
For example if you wish to consume beans from a JMS queue and insert them into a database
you could do.
from("activemq:queue:newAccount").
to("ibatis:insertAccount?statementType=Insert");
Notice we have to specify the statementType, as we need to instruct Camel which
SqlMapClient operation to invoke.
Where insertAccount is the iBatis id in the SQL map file:
<!-- Insert example, using the Account parameter class -->
<insert id="insertAccount" parameterClass="Account">
insert into ACCOUNT (
ACC_ID,
ACC_FIRST_NAME,
ACC_LAST_NAME,
ACC_EMAIL
)
values (
#id#, #firstName#, #lastName#, #emailAddress#
339
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
)
</insert>
Using StatementType for better control of IBatis
Available as of Camel 1.6.1/2.0
When routing to an iBatis endpoint you want more fine grained control so you can control
whether the SQL statement to be executed is a SELEECT, UPDATE, DELETE or INSERT etc.
This is now possible in Camel 1.6.1/2.0. So for instance if we want to route to an iBatis
endpoint in which the IN body contains parameters to a SELECT statement we can do:
from("direct:start")
.to("ibatis:selectAccountById?statementType=QueryForObject")
.to("mock:result");
In the code above we can invoke the iBatis statement selectAccountById and the IN body
should contain the account id we want to retrieve, such as an Integer type.
We can do the same for some of the other operations, such as QueryForList:
from("direct:start")
.to("ibatis:selectAllAccounts?statementType=QueryForList")
.to("mock:result");
And the same for UPDATE, where we can send an Account object as IN body to iBatis:
from("direct:start")
.to("ibatis:updateAccount?statementType=Update")
.to("mock:result");
Scheduled polling example
Since this component does not support scheduled polling you need to use another mechanism
for triggering the scheduled pools such as the Timer or Quartz components.
In the sample below we poll the database, every 30th second using the Timer component
and sends the data to the JMS queue:
from("timer://pollTheDatabase?delay=30000").to("ibatis:selectAllAccounts?statementType=QueryForList").
And the iBatis SQL map file used:
<!-- Select with no parameters using the result map for Account class. -->
<select id="selectAllAccounts" resultMap="AccountResult">
select * from ACCOUNT
</select>
CH APT ER 10 - CO M PO N EN T APPEN DIX
340
Using onConsume
This component supports executing statements after data have been consumed and processed
by Camel. This allows you to do post updates in the database. Notice all statements must be
UPDATE statements. Camel supports executing multiple statements whose name should be
separated by comma.
The route below illustrates we execute the consumeAccount statement data is
processed. This allows us to change the status of the row in the database to processed, so we
avoid consuming it twice or more.
from("ibatis:selectUnprocessedAccounts?consumer.onConsume=consumeAccount").to("mock:results");
And the statements in the sqlmap file:
<select id="selectUnprocessedAccounts" resultMap="AccountResult">
select * from ACCOUNT where PROCESSED = false
</select>
<update id="consumeAccount" parameterClass="Account">
update ACCOUNT set PROCESSED = true where ACC_ID = #id#
</update>
See Also
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
IRC COMPONENT
The irc: component implements an IRC (Iternet Relay Chat) transport.
URI format
irc:host[:port]/#room
See Also
•
•
•
•
341
Configuring Camel
Component
Endpoint
Getting Started
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
JAVASPACE COMPONENT
The javaspace: component is a transport for working with any JavaSpace compliant
implementation, this component has been tested with both the Blitz implementation and the
GigaSpace implementation .
This component can be used for sending and receiving any object inheriting from the Jini Entry
class, it's also possible to pass an id (Spring Bean) of a template that can be used for reading/
taking the entries from the space.
This component can be also used for sending/receiving any serializable object acting as a sort of
generic transport. The JavaSpace component contains a special optimization for dealing with the
BeanExchange. It can be used, then, for invoking remotely a POJO using as a transport a
JavaSpace.
This latter feature can be used for an easy implementation of the master/worker pattern where
a POJO provides the business logic for the worker.
Look at the test cases for seeing the various usage option for this component.
URI format
javaspace:jini://host?options
Examples
Sending and Receiving Entries
//Sending route
from("direct:input").to("javaspace:jini://localhost?spaceName=mySpace");
//Receiving Route
from("javaspace:jini://localhost?spaceName=mySpace&templateId=template&verb
In this case the payload can be any object inheriting from the Jini Entry.
Sending and receiving serializable objects
Using the routes as above it's also possible to send and receive any serializable object. The
camel component detects that the payload is not a Jini Entry and then it automatically wraps the
payload into a Camel Jini Entry. In this way a JavaSpace can be used as a generic transport.
Using JavaSpace as a remote invocation transport
The camel-javaspace component has been tailored to work in combination with the camel-bean
component. It's possible, then, to call a remote POJO using JavaSpace as a transport:
CH APT ER 10 - CO M PO N EN T APPEN DIX
342
from("direct:input").to("javaspace:jini://localhost?spaceName=mySpace");
//Client side
from("javaspace:jini://localhost?concurrentConsumers=10&spaceName=mySpace")
//Server side
In the code there are two test cases showing how to use the a POJO for realizing the master/
worker pattern. The idea is to use the POJO for providing the business logic and relying on
camel for sending/receiving requests/replies with the proper correlation.
Options
Name
Default Value
Description
spaceName
null
This is the JavaSpace name
verb
take
This is the verb for getting JavaSpace entries,
it can be: take or read
transactional
false
if true, sending and receiving of entries is
performed under a transaction
transactionalTimeout
Long.MAX_VALUE
the transaction timeout
concurrentConsumers
1
the number of concurrent consumer getting
entries from the JavaSpace
templateId
null
if present, this option it's a Spring Bean id to
be used as a template for reading/taking
entries
Using camel-javaspace
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-parent</artifactId>
<version>1.4.0.0-fuse</version>
</dependency>
And ensure you are pointing at the maven repo
<repository>
<id>open.iona.m2</id>
<name>IONA Open Source Community Release Repository</name>
<url>http://repo.open.iona.com/maven2</url>
<snapshots>
<enabled>false</enabled>
343
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
</snapshots>
<releases>
<enabled>true</enabled>
</releases>
</repository>
Building From Source
The source for camel-javaspace is available here: https://projects.open.iona.com/projects/svn/
iona/camel/trunk/components/camel-javaspace/
You'll need to register with http://open.iona.com to be able to access subversion.
The full FUSE distro is here: https://projects.open.iona.com/projects/svn/iona/camel/trunk/
See Also
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
JBI COMPONENT
The jbi: component is provided by the ServiceMix Camel module and provides integration with
a JBI Normalized Message Router such as provided by Apache ServiceMix
Following code
from("jbi:endpoint:http://foo.bar.org/MyService/MyEndpoint")
automatically exposes new endpoint to the bus where service qname is
{http://foo.bar.org}MyService and endpoint name is MyEndpoint (refer to URI format later).
All that has to be done to use this endpoint is to send messages from some endpoint already
declared (for example with jms:endpoint) to this JBI camel endpoint (the same way as
messages are sent to EIP endpoints or any other endpoint) and camel will pick it up the same
way as it picks any other messages.
Sending works in the same way:
to("jbi:endpoint:http://foo.bar.org/MyService/MyEndpoint")
Is used to send messages to JBI endpoint already deployed to the bus. It could be an endpoint
exposed by jms:endpoint, http:provider or anything else.
CH APT ER 10 - CO M PO N EN T APPEN DIX
344
See below for information regarding using StreamSource types from ServiceMix in Camel.
URI format
jbi:service:serviceNamespace[sep]serviceName
jbi:endpoint:serviceNamespace[sep]serviceName[sep]endpointName
jbi:name:endpointName
The separator used will be:
• '/' if the namespace looks like 'http://'
• ':' if the namespace looks like 'urn:foo:bar'
For more details of valid JBI URIs see the ServiceMix URI Guide.
Using the jbi:service: or jbi:endpoint: URI forms will set the service QName on the JBI
endpoint to the exact one you give. Otherwise the default Camel JBI Service QName will be
used which is
{http://activemq.apache.org/camel/schema/jbi}endpoint
Examples
jbi:service:http://foo.bar.org/MyService
jbi:endpoint:urn:foo:bar:MyService:MyEndpoint
jbi:endpoint:http://foo.bar.org/MyService/MyEndpoint
jbi:name:cheese
URI options
Name
Default value
Description
mep
<MEP of Camel
Exchange>
Allows users to override the MEP being used for
interacting with JBI (values are in-only, in-out,
robust-in-out and in-optional-out)
operation
<value of the
jbi.operation
header property>
Specify the JBI operation to be used for the
MessageExchange. If no value is supplied, the JBI
binding will use the value of the jbi.operation
header property
Examples
jbi:service:http://foo.bar.org/MyService?mep=in-out
JBI MessageExchanges)
345
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
(override the MEP, use InOut
jbi:endpoint:urn:foo:bar:MyService:MyEndpoint?mep=in
(override the MEP, use
InOnly JBI MessageExchanges)
jbi:endpoint:urn:foo:bar:MyService:MyEndpoint?operation={http://www.mycompany.org}AddNumbers
(overide the operation for the JBI Exchange to {http://www.mycompany.org}AddNumbers)
Using Stream bodies
If you are using any stream types as bodies then you should be aware that a stream is only
capable of being read once. So if you are enabling DEBUG logging then the body is usually debug
logged and thus read. To cater for this Camel has streamCaching that caches the stream is
it can be read multiple times.
from("jbi:endpoint:http://foo.bar.org/MyService/
MyEndpoint").streamCaching().to("xslt:transform.xsl", "bean:doSomething");
In Camel 1.5 onwards the stream caching is default enabled, so adding streamCaching()
is not needed.
In Camel 2.0 we are storing the big (over than 64K by default) input stream into to a temp
file by using CachedOutputStream(TODO need to add the java doc link), and when you close
the input stream , the temp file will be deleted.
Creating a JBI Service Unit
If you have some Camel routes you want to deploy inside JBI as a Service Unit you can use the
JBI Service Unit Archetype to create a new project.
If you have an existing maven project which you need to convert into a JBI Service Unit you
may want to refer to the ServiceMix Maven JBI Plugins for further help. Basically you just need
to make sure
• you have a spring XML file at src/main/resources/camel-context.xml which
is used to boot up your routes inside the JBI Service Unit
• you change the pom's packaging to jbi-service-unit
Your pom.xml should look something like this to enable the jbi-service-unit packaging.
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/
XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/
maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>myGroupId</groupId>
<artifactId>myArtifactId</artifactId>
<packaging>jbi-service-unit</packaging>
<version>1.0-SNAPSHOT</version>
<name>A Camel based JBI Service Unit</name>
<url>http://www.myorganization.org</url>
CH APT ER 10 - CO M PO N EN T APPEN DIX
346
<properties>
<camel-version>1.0.0</camel-version>
<servicemix-version>3.3</servicemix-version>
</properties>
<dependencies>
<dependency>
<groupId>org.apache.servicemix</groupId>
<artifactId>servicemix-camel</artifactId>
<version>${servicemix-version}</version>
</dependency>
<dependency>
<groupId>org.apache.servicemix</groupId>
<artifactId>servicemix-core</artifactId>
<version>${servicemix-version}</version>
<scope>provided</scope>
</dependency>
</dependencies>
<build>
<defaultGoal>install</defaultGoal>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<source>1.5</source>
<target>1.5</target>
</configuration>
</plugin>
<!-- creates the JBI deployment unit -->
<plugin>
<groupId>org.apache.servicemix.tooling</groupId>
<artifactId>jbi-maven-plugin</artifactId>
<version>${servicemix-version}</version>
<extensions>true</extensions>
</plugin>
</plugins>
</build>
</project>
See Also
•
•
•
•
•
•
•
347
Configuring Camel
Component
Endpoint
Getting Started
ServiceMix Camel module
Using Camel with ServiceMix
Cookbook on using Camel with ServiceMix
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
JCR COMPONENT
The jcr: component allows you to add nodes to a JCR (JSR-170) compliant content
repository (e.g. Apache Jackrabbit ).
URI format
jcr://user:password@repository/path/to/node
Usage
The repository element of the URI is used to look up the JCR Repository object in the
Camel context registry.
If a message is sent to a producer endpoint created by this component:
• a new node is created in the content repository
• all the message properties of the in message will be transformed to JCR Value
instances and added to the new node
• the node's UUID is returned in the out message
Message properties
All message properties are converted to node properties, except for the
CamelJcrNodeName (you can refer to JcrConstants.NODE_NAME in your code), which
is used to determine the node name.
Example
The snippet below will create a node named node under the /home/test node in the
content repository. One additional attribute will be added to the node as well:
my.contents.property will contain the body of the message being sent.
from("direct:a").setProperty(JcrConstants.JCR_NODE_NAME, constant("node"))
.setProperty("my.contents.property", body()).to("jcr://user:pass@repository/home/
test");
See Also
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
CH APT ER 10 - CO M PO N EN T APPEN DIX
348
JDBC COMPONENT
The jdbc: component allows you to work with databases using JDBC queries and operations
via SQL text as the message payload.
This component uses standard Java JDBC to work with the database, unlike the SQL
Component component that uses spring-jdbc.
URI format
jdbc:dataSourceName?options
This component only supports producer, meaning that you can not use routes with this
component in the from type.
Options
Name
Default
Value
Description
readSize
0 / 2000
The default maximum number of rows that can be read by a polling
query. The default value is 2000 for Camel 1.5.0 or older. In newer
releases the default value is 0.
Result
The result is returned in the OUT body as a ArrayList<HashMap<String, Object>>
list object with the result. The List contains the list of rows and the Map contains each row
with the string key as the column name.
Note: This component fetches ResultSetMetaData to be able to return the column name as
the key in the Map.
Message Headers
Header
Description
CamelJdbcRowCount
If the query is a select query the row count is returned in
this OUT header
CamelJdbcUpdateCount
If the query is an update query the update count is returned
in this OUT header
Samples
In the sample below we fetch the rows from the customer table.
349
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
So far endpoints from this component could be used only as producers. It means that you
cannot use them in from() statement.
First we register our datasource in the Camel registry as testdb:
JndiRegistry reg = super.createRegistry();
reg.bind("testdb", ds);
return reg;
Then we configure a route that routes to the JDBC component so the SQL will be executed,
notice that we refer to the testdb datasource that was bound in the previous step:
// lets add simple route
public void configure() throws Exception {
from("direct:hello").to("jdbc:testdb?readSize=100");
}
Or you can create a datasource in Spring like this:
<camelContext id="camel" xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="timer://kickoff?period=10000"/>
<setBody>
<constant>select * from customer</constant>
</setBody>
<to uri="jdbc:testdb"/>
<to uri="mock:result"/>
</route>
</camelContext>
<!-- Just add a demo to show how to bind a date source for camel in Spring-->
<bean id="testdb" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
<property name="driverClassName" value="org.hsqldb.jdbcDriver"/>
<property name="url" value="jdbc:hsqldb:mem:camel_jdbc" />
<property name="username" value="sa" />
<property name="password" value="" />
</bean>
And then we create the endpoint and sends the exchange containing the SQL query to execute
in the in body. The result is returned in the out body.
// first we create our exchange using the endpoint
Endpoint endpoint = context.getEndpoint("direct:hello");
Exchange exchange = endpoint.createExchange();
// then we set the SQL on the in body
exchange.getIn().setBody("select * from customer order by ID");
// now we send the exchange to the endpoint, and receives the response from Camel
Exchange out = template.send(endpoint, exchange);
// assertions of the response
assertNotNull(out);
assertNotNull(out.getOut());
CH APT ER 10 - CO M PO N EN T APPEN DIX
350
ArrayList<HashMap<String, Object>> data = out.getOut().getBody(ArrayList.class);
assertNotNull("out body could not be converted to an ArrayList - was: "
+ out.getOut().getBody(), data);
assertEquals(2, data.size());
HashMap<String, Object> row = data.get(0);
assertEquals("cust1", row.get("ID"));
assertEquals("jstrachan", row.get("NAME"));
row = data.get(1);
assertEquals("cust2", row.get("ID"));
assertEquals("nsandhu", row.get("NAME"));
Sample - Polling the database every minute
If we want to poll a database using this component we need to combine this with a polling
scheduler such as the Timer or Quartz etc.
In this sample we retrieve data from the database every 60th seconds.
from("timer://foo?period=60000").setBody(constant("select * from
customer")).to("jdbc:testdb").to("activemq:queue:customers");
See Also
•
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
SQL
JETTY COMPONENT
The jetty: component provides HTTP based endpoints for consuming HTTP requests that
arrive at a http endpoint.
URI format
jetty:http://hostname[:port][/resourceUri][?options]
Options
351
Name
Default
Value
Description
sessionSupport
false
The option to enable the session manager in the server side of
Jetty.
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
null
Camel 1.5.1/2.0: Configuration of the HttpClient Jetty uses.
So setting httpClient.idleTimeout=30000 will set the idle
timeout to 30 seconds.
httpBindingRef
null
Camel 1.5.1/2.0: Reference to a
org.apache.camel.component.http.HttpBinding
in the Registry. HttpBinding can be used to customize how
response should be written.
matchOnUriPrefix
false
Camel 2.0: Whether or not the CamelServlet should try to
find a target consumer by matching URI prefix if no exact
match is found.
null
Camel 1.6.1/2.0: Specifies a comma delimited set of
org.mortbay.jetty.Handler instances in your Registry
(such as your Spring ApplicationContext). These handlers are
added to the Jetty servlet context, for instance to add security.
httpClient.XXX
handlers
Message Headers
Camel will apply the same Message Headers form the HTTP component.
Camel will also populate all request.parameter and request.headers. For instance of a client
request with http://myserver/myserver?orderid=123 then the exchange will
contain a header named orderid with the value 123. This feature is introduced in Camel 1.5.
Usage
You can only consume from endpoints generated by the Jetty component. Therefore it should
only be used as input into your camel Routes. To issue HTTP requests against other HTTP
endpoints you can use the HTTP Component
Sample
In this sample we define a route where we expose a http service at
http://localhost:8080/myapp/myservice:
from("jetty:http://localhost:9080/myapp/myservice").process(new MyBookService());
Our business logic is implemented in our MyBookService class where we can access the http
request stuff and return a response.
Note: The assert is because the code is part of an unit test.
public class MyBookService implements Processor {
public void process(Exchange exchange) throws Exception {
// just get the body as a string
String body = exchange.getIn().getBody(String.class);
CH APT ER 10 - CO M PO N EN T APPEN DIX
352
Usage of localhost
When specifying localhost in URL Camel will expose the endpoint only on local
interface, so it cannot be accessed from outside the machine it operates on.
If an endpoint should be exposed on specific network interface, specific IP address of
this interface should be used. If an endpoint should be exposed on all interfaces 0.0.0.0
address should be used.
// we have access to the HttpServletRequest here and we can grab it if we need
it
HttpServletRequest req = exchange.getIn().getBody(HttpServletRequest.class);
assertNotNull(req);
// for unit testing
assertEquals("bookid=123", body);
// send a html response
exchange.getOut().setBody("<html><body>Book 123 is Camel in
Action</body></html>");
}
}
In the sample below we have a content based route that routes all requests that contain the
URI parameter one to mock:one and all others to mock:other.
from("jetty:" + serverUri)
.choice()
.when().simple("in.header.one").to("mock:one")
.otherwise()
.to("mock:other");
So if a client sends the http request: http://serverUri?one=hello then camel-jetty will
copy the http request parameter one to the exchange.in.header. Then we can use the simple
language to route exchanges that contain this header to a specific endpoint and all others to
another. If we used a more powerful language than Simple such as El or OGNL would could
also test for the parameter value and do routing based on the header value as well.
Session Support
Session support can be used to enable HttpSession and being able to get this while processing
the exchange.
<route>
<from uri="jetty:http://0.0.0.0/myapp/myservice/?sessionSupport=true"/>
<processRef ref="myCode"/>
<route>
353
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
And then we have a Processor that we configure as:
<bean id="myCode" class="com.mycompany.MyCodeProcessor"/>
And in this processor we can get the HttpSession:
public void process(Exchange exchange) throws Exception {
HttpSession session = ((HttpExchange)exchange).getRequest().getSession();
...
}
SSL https Support
Jetty Provides SSL support out of the box. To configure Jetty to run in SSL mode, you simply
set the uri to have https:// as the parameter.
<from uri="jetty:https://0.0.0.0/myapp/myservice/"/>
Jetty will need to know where to load your keystore from and what passwords to use in order
to load the correct SSL certificate. The relevant System Properties set will point jetty in the
right direction.
For the keystore path, use jetty.ssl.keystore
For the passwords, use jetty.ssl.keypassword and jetty.ssl.password
To create a certificate, and for Password issues, read the following documentation at the
Jetty Site. http://docs.codehaus.org/display/JETTY/How+to+configure+SSL
Default behavior for returning HTTP status codes
Camel will default use
org.apache.camel.component.http.DefaultHttpBinding that handles how
response is written, and also setting the http status code.
If the exchange could be processed with success http status code 200 is returned. However
if the OUT message contains a header HttpProducer.HTTP_RESPONSE_CODE then this
code is used instead. To allow end users to set a specific status code.
If the exchange failed with an exception http status code 500 is returned, and the stacktrace is
returned in the body.
Customizing HttpBinding
Available as of Camel 1.5.1/2.0
Camel will default use
org.apache.camel.component.http.DefaultHttpBinding that handles how
response is written.
This behavior can be customized by implementing your own HttpBinding class or extending
DefaultHttpBinding and override appropriate methods.
In the sample below we use our own binding to change how exceptions should be returned:
CH APT ER 10 - CO M PO N EN T APPEN DIX
354
public class MyHttpBinding extends DefaultHttpBinding {
@Override
public void doWriteExceptionResponse(Throwable exception, HttpServletResponse
response) throws IOException {
// we override the doWriteExceptionResponse as we only want to alter the
binding how exceptions is
// written back to the client.
// we just return HTTP 200 so the client thinks its okay
response.setStatus(200);
// and we return this fixed text
response.getWriter().write("Something went wrong but we dont care");
}
}
Then we can have our binding registered in the registry as:
<bean id="mybinding" class="com.mycompany.MyHttpBinding"/>
And then we can refer to this binding when we configure the route:
<route>
<from uri="jetty:http://0.0.0.0:8080/myapp/myservice?httpBindingRef=mybinding"/>
<to uri="bean:doSomething"/>
</route>
Jetty Handlers for e.g. security
Available as of Camel 1.6.1/2.0 you can configure a list of handlers on the endpoint.
These handlers could be configured in Spring XML as:
<-- Jetty Security handling -->
<bean id="userRealm" class="org.mortbay.jetty.plus.jaas.JAASUserRealm">
<property name="name" value="tracker-users" />
<property name="loginModuleName" value="ldaploginmodule" />
</bean>
<bean id="constraint" class="org.mortbay.jetty.security.Constraint">
<property name="name" value="BASIC" />
<property name="roles" value="tracker-users" />
<property name="authenticate" value="true" />
</bean>
<bean id="constraintMapping"
class="org.mortbay.jetty.security.ConstraintMapping">
<property name="constraint" ref="constraint" />
<property name="pathSpec" value="/*" />
</bean>
<bean id="securityHandler" class="org.mortbay.jetty.security.SecurityHandler">
<property name="userRealm" ref="userRealm" />
<property name="constraintMappings" ref="constraintMapping" />
</bean>
And then you could define the endpoint as:
from("jetty:http://0.0.0.0:9080/myservice?handlers=securityHandler")
355
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
If you need more handlers then just add another separated with comma.
See Also
•
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
Http
JING COMPONENT
The Jing component uses the Jing Library to perform XML validation of the message body using
either
• RelaxNG XML Syntax
• RelaxNG Compact Syntax
Note that the MSV component can also support RelaxNG XML syntax.
URI format
rng:someLocalOrRemoteResource
rnc:someLocalOrRemoteResource
Where rng means use the RelaxNG XML Syntax whereas rnc means use RelaxNG Compact
Syntax. The following examples show possible URI values
Example
Description
rng:foo/bar.rng
Will take the XML file foo/bar.rng on the classpath
rnc:http://foo.com/
bar.rnc
Will use the RelaxNG Compact Syntax file from the URL
http://foo.com/bar.rnc
Example
The following example shows how to configure a route from endpoint direct:start which
then goes to one of two endpoints, either mock:valid or mock:invalid based on whether
or not the XML matches the given RelaxNG Compact Syntax schema (which is supplied on the
classpath).
<camelContext xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="direct:start"/>
<doTry>
<to uri="rnc:org/apache/camel/component/validator/jing/schema.rnc"/>
<to uri="mock:valid"/>
CH APT ER 10 - CO M PO N EN T APPEN DIX
356
<doCatch>
<exception>org.apache.camel.ValidationException</exception>
<to uri="mock:invalid"/>
</doCatch>
<doFinally>
<to uri="mock:finally"/>
</doFinally>
</doTry>
</route>
</camelContext>
See Also
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
JMS COMPONENT
The JMS component allows messages to be sent to a JMS Queue or Topic; or messages to be
consumed from a JMS Queue or Topic. The implementation of the JMS Component uses
Spring's JMS support for declarative transactions, using Spring's JmsTemplate for sending and a
MessageListenerContainer for consuming.
URI format
jms:[topic:]destinationName?options
So for example to send to queue FOO.BAR you would use
jms:FOO.BAR
You can be completely specific if you wish via
jms:queue:FOO.BAR
If you want to send to a topic called Stocks.Prices then you would use
jms:topic:Stocks.Prices
Using Temporary Destinations
As of 1.4.0 of Camel you can use temporary queues using the following URL format
jms:temp:queue:foo
or temporary topics as
357
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
Using ActiveMQ
If you are using Apache ActiveMQ you should prefer to use the ActiveMQ component as it
has been particularly optimized for ActiveMQ.
All the options and samples on this page applies as well for ActiveMQ component.
jms:temp:topic:bar
Where foo and bar, the text after the String jms:temp:queue: or jms:temp:topic:, are
the names of the destinations. This enables multiple routes or processors or beans to refer to
the same temporary destination. e.g. you can create 3 temporary destinations and use them in
routes as inputs or outputs by referring to them by name.
Notes
If you wish to use durable topic subscriptions, you need to specify both clientId and
durableSubscriptionName. Note that the value of the clientId must be unique and can
only be used by a single JMS connection instance in your entire network. You may prefer to use
Virtual Topics instead to avoid this limitation. More background on durable messaging here.
When using message headers; the JMS specification states that header names must be valid
Java identifiers. So by default camel will ignore any headers which do not match this rule. So try
name your headers as if they are valid Java identifiers. One added bonus of this is that you can
then use your headers inside a JMS Selector - which uses SQL92 syntax which mandates Java
identifier syntax for headers.
From Camel 1.4 a simple strategy for mapping headers names is used by default. The
strategy is to replace any dots in the headername with underscore, and vice-versa when the
header name is restored from the JMS message that was sent over the wire. What does this
means? No more loosing method names to invoke on a bean component, no more loosing the
filename header for the File Component etc.
Current header name strategy used for accepting header names in Camel:
• replace all dots with underscores (e.g. org.apache.camel.MethodName =>
org_apache_camel_MethodName)
• test if the name is a valid java identifier using the JDK core classes
• if test success then the header is added and sent over the wire, if not its dropped
(logged at DEBUG level)
Options
You can configure lots of different properties on the JMS endpoint which map to properties on
the JMSConfiguration POJO. Notice: Many of these properties maps to properties on Spring
JMS that Camel uses for sending and receiving messages. So you can get more information
about these properties by consulting the Spring documentation.
CH APT ER 10 - CO M PO N EN T APPEN DIX
358
If you are using ActiveMQ
Note that the JMS component reuses Spring 2's JmsTemplate for sending messages. This is
not ideal for use in a non-J2EE container and typically requires some caching JMS provider
to avoid performance being lousy.
So if you intent to use Apache ActiveMQ as your Message Broker - which is a good
choice as ActiveMQ rocks
, then we recommend that you either
• use the ActiveMQ component which is already configured to use
ActiveMQ efficiently
• use the PoolingConnectionFactory in ActiveMQ
For Consuming Messages cacheLevelName settings are vital!
If you are using Spring before 2.5.1 and Camel before 1.3.0 then you might want to set the
cacheLevelName to be CACHE_CONSUMER for maximum performance.
Due to a bug in earlier Spring versions causing a lack of transactional integrity, previous
versions of Camel and Camel versions from 1.3.0 onwwards when used with earlier Spring
versions than 2.5.1 will default to use CACHE_CONNECTION. See the JIRAs CAMEL-163
and CAMEL-294.
Also if you are using XA or running in a J2EE container then you may want to set the
cacheLevelName to be CACHE_NONE as we have seen using JBoss with TibCo EMS
and JTA/XA you must disable caching.
Another end user reports issue with using WebSphere MQ 6.0.2.5, Camel 1.6.0 and
Spring 2.5.6. Not running XA or inside a J2EE Container, but the
cacheLevelName=CACHE_NONE seems to have solved the problem with WebSphere
MQ.
See also more about JmsTemplate gotchas.
359
Option
Default Value
Description
acceptMessagesWhileStopping
false
Should the consumer accept messages while it is stopping
acknowledgementModeName
"AUTO_ACKNOWLEDGE"
The JMS acknowledgement name which is one of: TRANSACTED, CLIENT_ACKNOWLEDGE, AUTO_ACKNOWLEDGE,
DUPS_OK_ACKNOWLEDGE
acknowledgementMode
-1
The JMS acknowledgement mode defined as an Integer. Allows to set vendor-specific extensions to the acknowledgment
mode. For the regular modes prefer to use the acknowledgementModeName instead.
alwaysCopyMessage
false
If true then Camel will always make a JMS message copy of the message when it's passed to the producer for sending.
Copying the message is needed in some situations such as when a replyToDestinationSelectorName is set (Camel will by
the way set the alwaysCopyMessage to true if a replyToDestinationSelectorName is set)
autoStartup
true
Should the consumer container auto-startup
cacheLevelName
"CACHE_CONSUMER"
Sets the cache level by name for the underlying JMS resources. Possible values are: CACHE_AUTO,
CACHE_CONNECTION, CACHE_CONSUMER, CACHE_NONE and CACHE_SESSION. See the Spring documentation.
And see the warning above.
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
cacheLevel
-1
Sets the cache level by id for the underlying JMS resources
clientId
null
Sets the JMS client ID to use. Note that this value if specified must be unique and can only be used by a single JMS
connection instance. Its typically only required for durable topic subscriptions. You may prefer to use Virtual Topics instead
consumerType
Default
The consumer type to use, either: Simple, Default or ServerSessionPool. The consumer type determines which
Spring JMS listener should be used. Default will use
org.springframework.jms.listener.DefaultMessageListenerContainer. Simple will use
org.springframework.jms.listener.SimpleMessageListenerContainer and ServerSessionPool
will use
org.springframework.jms.listener.serversession.ServerSessionMessageListenerContainer.
If option useVersion102=true then Camel will of course use the JMS 1.0.2 Spring classes instead.
ServerSessionPool is @deprecated and will be removed in Camel 2.0.
concurrentConsumers
1
Specifies the default number of concurrent consumers
connectionFactory
null
The default JMS connection factory to use for the listenerConnectionFactory and templateConnectionFactory if neither are
specified
deliveryPersistent
true
Is persistent delivery used by default?
destination
null
(2.0 onwards) specifies the JMS Destination object to use on this endpoint
destinationName
null
(2.0 onwards) specifies the JMS destination name to use on this endpoint
disableReplyTo
false
Do you want to ignore the JMSReplyTo header and so treat messages as InOnly by default and not send a reply back?
durableSubscriptionName
null
The durable subscriber name for specifying durable topic subscriptions
eagerLoadingOfProperties
false
Enables eager loading of JMS properties as soon as a message is received which generally is inefficient as the JMS properties
may not be required but sometimes can catch early any issues with the underlying JMS provider and the use of JMS
properties. Can be used for testing purpose to ensure JMS properties can be understood and handled correctly.
exceptionListener
null
The JMS Exception Listener used to be notified of any underlying JMS exceptions
explicitQosEnabled
false
Set if the deliveryMode, priority or timeToLive should be used when sending messages
exposeListenerSession
true
Set if the listener session should be exposed when consuming messages
idleTaskExecutionLimit
1
Specify the limit for idle executions of a receive task, not having received any message within its execution. If this limit is
reached, the task will shut down and leave receiving to other executing tasks (in case of dynamic scheduling; see the
"maxConcurrentConsumers" setting).
jmsMessageType
null
Camel 2.0: Allows you to force to use a specific javax.jms.Message implementation for sending a jms message. Possible
values: Bytes, Map, Object, Stream, Text. By default Camel will determine from the IN body type which Jms
message type to use. This option allows you to choose it.
jmsOperations
null
Allow to use your own implementation of the org.springframework.jms.core.JmsOperations interface.
Camel uses JmsTemplate as default. Can be used for testing purpose, but not used much as stated in the spring API docs.
jmsKeyFormatStrategy
default
Camel 2.0: Pluggable strategy for encoding and decoding JMS keys so they can be compliant with the JMS spec. Camel
provides two implementations out of the box: default and passthrough. Default will safely marshal dots and hyphens
(. and -). Passthrough lets the key as is. Can be used for JMS brokers which do not care about JMS header keys containing
illegal characters. You can provide you own implementation of the
org.apache.camel.component.jms.JmsKeyFormatStrategy and refer to it using the # notation.
lazyCreateTransactionManager
true
(new added in Camel 2.0)If it is true , Camel will create a JmsTransactionManager if there is no transactionManager injected
when the transacted is true
listenerConnectionFactory
null
The JMS connection factory used for consuming messages
maxConcurrentConsumers
1
Specifies the maximum number of concurrent consumers
maxMessagesPerTask
1
The number of messages per task
messageConverter
null
The Spring Message Converter
messageIdEnabled
true
When sending, should message IDs be added
messageTimestampEnabled
true
Should timestamps be enabled by default on sending messages
password
null
The password which is set for the connector factory
priority
-1
Values of > 1 specify the message priority when sending, if the explicitQosEnabled property is specified (with 0 as the lowest
priority and 9 as the highest)
preserveMessageQos
false
Set to true if you want to send message using the QoS settings specified on the message, instead of the QoS settings on the
JMS endpoint
pubSubNoLocal
false
Set whether to inhibit the delivery of messages published by its own connection
selector
null
Sets the JMS Selector which is an SQL 92 predicate used to apply to messages to filter them at the message broker. You
may have to encode special characters such as = as %3D
receiveTimeout
none
The timeout when receiving messages
recoveryInterval
none
The recovery interval
replyTo
null
Provides an explicit reply to destination which overrides any incoming value of Message.getJMSReplyTo()
CH APT ER 10 - CO M PO N EN T APPEN DIX
360
replyToTempDestinationAffinity
endpoint
defines the component created temporary replyTo destination sharing strategy. Possible values are: component,
endpoint or producer. component = a single temp queue is shared among all producers for a given component
instance. endpoint = a single temp queue is shared among all producers for a given endpoint instance. producer = a
single temp queue is created per producer.
replyToDestinationSelectorName
null
Sets the JMS Selector using the fixed name to be used so you can filter out your own replies from the others, when using a
shared queue (i.e. if you are not using a temporary reply queue).
replyToDeliveryPersistent
true
Is persistent delivery used by default for reply?
requestTimeout
20000
The timeout when sending messages
serverSessionFactory
null
@deprecated - will be removed in Camel 2.0. The JMS ServerSessionFactory if you wish to use ServerSessionFactory for
consumption
subscriptionDurable
false
Enabled by default if you specify a durableSubscriberName and a clientId
taskExecutor
null
Allows you to specify a custom task executor for consuming messages
templateConnectionFactory
null
The JMS connection factory used for sending messages
timeToLive
null
Is a time to live specified when sending messages
transacted
false
If transacted mode will be used for sending/receiving messages using the InOnly Exchange Pattern. See section Enabling
Transacted Consumption for more details.
transactedInOut
false
If transacted mode will be used when sending/receiving messages using the InOut Exchange Pattern. See section Enabling
Transacted Consumption for more details.
transactionManager
null
The Spring transaction manager to use
transactionName
null
The name of the transaction to use
transactionTimeout
null
The timeout value of the transaction if using transacted mode
transferException
false
Camel 2.0: If enabled and you are using Request Reply messaging (InOut) and an Exchange failed on the consumer side
then the caused Exception will be send back as response as a javax.jms.ObjectMessage. If the client is Camel then
that returned Exception will be rethrown. This allows you to use Camel JMS as a bridge in your routing, e.g. using persistent
queues to enable robust routing. Notice that if you also have transferExchange enabled then this option takes
precedence. The exceptions caught is required to be serializable. The original caused Exception on the consumer side can
be wrapped in an outer exception such as org.apache.camel.RuntimeCamelException when returned to the
producer.
transferExchange
false
Camel 2.0: You can transfer the exchange over the wire instead of just the body and headers. The following fields is
transferred: in body, out body, fault body, in headers, out headers, fault headers, exchange properties, exchange exception.
This requires that the objects are Serializable. Camel will exclude any non serializable objects and log it at WARN level.
username
null
The username which is set for the connector factory
useMessageIDAsCorrelationID
false
Should JMSMessageID be used as JMSCorrelationID for InOut messages. Camel will by default use a GUID
useVersion102
false
Should the old JMS API be used
Message Mapping between JMS and Camel
Camel will automatically map messages between javax.jms.Message and
org.apache.camel.Message.
When sending a JMS message Camel will convert the body to the following JMS message:
361
Body Type
JMS Message
String
javax.jms.TextMessage
org.w3c.dom.Node
javax.jms.TextMessage
Map
javax.jms.MapMessage
java.io.Serializable
javax.jms.ObjectMessage
byte[]
javax.jms.BytesMessage
java.io.File
javax.jms.BytesMessage
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
Comment
The DOM will be converted to
String
java.io.Reader
javax.jms.BytesMessage
java.io.InputStream
javax.jms.BytesMessage
java.nio.ByteBuffer
javax.jms.BytesMessage
When receiving a JMS message Camel will convert the JMS message to the following body type:
JMS Message
Body Type
javax.jms.TextMessage
String
javax.jms.BytesMessage
byte[]
javax.jms.MapMessage
Map<String, Object>
javax.jms.ObjectMessage
Object
Comment
Overriding or controlling the mapping
Available as of Camel 2.0
You can use the option jmsMessageType on the endpoint to force using a specific
message type for all messages.
In the route below we will poll files from a folder and send them as
javax.jms.TextMessage as we have forced the JMS producer endpoint to use Text
messages.
from("file://inbox/order").to("jms:queue:order?jmsMessageType=Text");
You can also provide a per. message type as a header with the key CamelJmsMessageType.
from("file://inbox/order").setHeader("CamelJmsMessageType",
JmsMessageType.Text).to("jms:queue:order");
The possible values is defined in an enum class
org.apache.camel.jms.JmsMessageType.
Message format when sending
The exchange that is sent over the JMS wire must conform to the JMS Message spec.
For the exchange.in.header the following rules apply for the keys:
• Keys stating with JMS or JMSX is reserved. All user keys will be dropped.
• exchange.in.headers keys must be literals and all be valid Java identifiers. (do
not use dots in the key name)
• In Camel 1.4 onwards Camel will automatically replace all dots with underscore for
key names. And vice-versa when Camel consumes JMS messages.
• In Camel 2.0 onwards Camel will also replace all hyphens with the special token:
_HYPHEN_. And vice-versa when Camel consumes JMS messages.
CH APT ER 10 - CO M PO N EN T APPEN DIX
362
• See also option jmsKeyFormatStrategy introduced in Camel 2.0.
For the exchange.in.header the following rules apply for the values:
• The values must be primitives or their counter objects (such as Integer, Long,
Character). String, CharSequence, Date, BigDecimal or BigInteger is all converted to
their toString() representation. All other types is dropped.
Camel will log with category org.apache.camel.component.jms.JmsBinding at
DEBUG level if it drops a given header value. Example:
2008-07-09 06:43:04,046 [main
] DEBUG JmsBinding
- Ignoring non primitive header: order of class:
org.apache.camel.component.jms.issues.DummyOrder with value: DummyOrder{orderId=333,
itemId=4444, quantity=2}
Message format when receiving
Camel will add the following properties to the Exchange when it receives a message:
Property
Type
Description
org.apache.camel.jms.replyDestination
javax.jms.Destination
The reply
destination
Camel will add the following JMS properties to the IN Message headers when it receives a JMS
message:
Header
Type
Description
JMSCorrelationID
String
The JMS correlation id
JMSDeliveryMode
int
The JMS delivery mode
JMSDestination
javax.jms.Destination
The JMS destination
JMSExpiration
long
The JMS expiration
JMSMessageID
String
The JMS unique message id
JMSPriority
int
The JMS priority (with 0 as the lowest
priority and 9 as the highest)
JMSRedelivered
boolean
Is the JMS message redelivered
JMSReplyTo
javax.jms.Destination
The JMS reply to destination
JMSTimestamp
long
The JMS timestamp
JMSType
String
The JMS type
JMSXGroupID
String
The JMS group id
As all the above information is standard JMS you can check the JMS documentation for further
details.
363
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
Configuring different JMS providers
You can configure your JMS provider inside the Spring XML as follows...
<camelContext id="camel" xmlns="http://camel.apache.org/schema/spring">
</camelContext>
<bean id="activemq" class="org.apache.camel.component.jms.JmsComponent">
<property name="connectionFactory">
<bean class="org.apache.activemq.ActiveMQConnectionFactory">
<property name="brokerURL" value="vm://localhost?broker.persistent=false"/>
</bean>
</property>
</bean>
Basically you can configure as many JMS component instances as you wish and give them a
unique name via the id attribute. The above example configures an 'activemq'
component. You could do the same to configure MQSeries, TibCo, BEA, Sonic etc.
Once you have a named JMS component you can then refer to endpoints within that
component using URIs. For example for the component name'activemq' you can then refer to
destinations as activemq:[queue:|topic:]destinationName. So you could use the same
approach for working with all other JMS providers.
This works by the SpringCamelContext lazily fetching components from the spring context
for the scheme name you use for Endpoint URIs and having the Component resolve the
endpoint URIs.
Using JNDI to find the ConnectionFactory
If you are using a J2EE container you might want to lookup in JNDI to find your
ConnectionFactory rather than use the usual <bean> mechanism in spring. You can do this
using Spring's factory bean or the new Spring XML namespace. e.g.
<bean id="weblogic" class="org.apache.camel.component.jms.JmsComponent">
<property name="connectionFactory" ref="myConnectionFactory"/>
</bean>
<jee:jndi-lookup id="myConnectionFactory" jndi-name="jms/connectionFactory"/>
Concurrent Consuming
A common requirement with JMS is to consume messages concurrently in many threads to
achieve high throughput. As shown above you use the concurrentConsumers property
above.
from("jms:SomeQueue?concurrentConsumers=20").
bean(MyClass.class);
You can configure the properties on the JmsComponent if you wish or on specific endpoints via
the URI or by configuring the JmsEndpoint directly.
CH APT ER 10 - CO M PO N EN T APPEN DIX
364
Enabling Transacted Consumption
A common requirement is to consume from a queue in a transaction then process the message
using the Camel route. To do this just ensure you set the following properties on the
component/endpoint
• transacted = true
• transactionManager = a Transsaction Manager - typically the JmsTransactionManager
See also the Transactional Client EIP pattern for further details.
Using JMSReplyTo for late replies
Avaiable as of Camel 2.0
When using Camel as a JMS listener it will place a property on the Exchange with the
ReplyTo javax.jms.Destination object in the key ReplyTo.
You can obtain this Destination as shown here:
Destination replyDestination =
exchange.getProperty(JmsConstants.JMS_REPLY_DESTINATION, Destination.class);
And then later use it to send a reply using regular or Camel JMS.
// we need to pass in the JMS component, and in this sample we use ActiveMQ
JmsEndpoint endpoint = JmsEndpoint.newInstance(replyDestination,
activeMQComponent);
// now we have the endpoint we can use regular Camel API to send a message to it
template.sendBody(endpoint, "Here is the late reply.");
A different solution to sending it is to provide the replyDestination object in the same Exchange
property when sending. Then Camel will pickup this property and use it for the real destination.
This requires however that you send it to some dummy destination. Okay here goes:
// we pretend to send it to some non existing dummy queue
template.send("activemq:queue:dummy, new Processor() {
public void process(Exchange exchange) throws Exception {
// and here we override the destination with the ReplyTo destination
object so the message is sent to there instead of dummy
exchange.setProperty(JmsConstants.JMS_DESTINATION, replyDestination);
exchange.getIn().setBody("Here is the late reply.");
}
}
Using request timeout
In the sample below we send a Request Reply style message Exchange (we use the
requestBody method = InOut) to the slow queue for further processing in Camel and we
wait for a return reply.
// send a in-out with a timeout for 5 sec
Object out = template.requestBody("activemq:queue:slow?requestTimeout=5000", "Hello
World");
365
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
Transaction and Request Reply over JMS
Note that when using Request Reply over JMS you cannot use a single transaction; as JMS
will not send any messages until a commit is performed so the server side won't receive
anything at all until the transaction commits. So with request/response you must commit a
transaction after sending the first request and then use a separate transaction for receiving
the response.
Its for this reason that the transacted property only applies to InOnly message
Exchange Pattern. If you still want to use transacted for InOut then you must use
transactedInOut=true.
To recap: if you have transacted=true, transactedInOut=false and are
sending an InOut then the Exchange will not use transaction.
Samples
JMS is used in many examples for other components as well. But we provide a few samples
below to get started.
Receiving from JMS
In this sample we configure a route that receives JMS messages and routes the message to a
POJO
from("jms:queue:foo").
to("bean:myBusinessLogic");
You can of course use any of the EIP pattern so the route can be context based, such as
filtering an order topic for the big spenders:
from("jms:topic:OrdersTopic").
filter().method("myBean", "isGoldCustomer").
to("jms:queue:BigSpendersQueue");
Sending to a JMS
In the sample below we poll a file folder and send the file content to a JMS topic. As we want
the content of the file as a TextMessage instead of a BytesMessage we need to convert the
body to a String.
from("file://orders").
convertBodyTo(String.class).
to("jms:topic:OrdersTopic");
CH APT ER 10 - CO M PO N EN T APPEN DIX
366
Using Annotations
Camel also has annotations so you can use POJO Consuming and POJO Producing.
Spring DSL sample
The sample above are using the Java DSL. Camel also supports using Spring XML DSL. Here is
the big spender sample using Spring DSL:
<route>
<from uri="jms:topic:OrdersTopic"/>
<filter>
<method bean="myBean" method="isGoldCustomer"/>
<to uri="jms:queue:BigSpendersQueue"/>
</filter>
</route>
Other samples
JMS is used a lot in other samples for other components and EIP patterns as well in this Camel
documentation. So feel free to browse the documentation. If you have good time then check
out the this tutorial that uses JMS but focuses on how well Spring Remoting and Camel works
together Tutorial-JmsRemoting.
Using JMS as a Dead Letter Queue storing Exchange
Available as of Camel 2.0
Normally when using JMS as transport in only transfers the body and headers as payload. If you
want to use JMS with Dead Letter Channel using a JMS queue as the Dead Letter Queue then
normally the caused Exception is not stored in the JMS message. You can therefore use the
option transferExchange on the JMS dead letter queue to instruct Camel to store the
entire Exchange in the queue as a javax.jms.ObjectMessage that holds a
org.apache.camel.impl.DefaultExchangeHolder. This allows you to consume
from the Dead Letter Queue and grap the caused exception using a Exchange property with the
key Exchange.EXCEPTION_CAUGHT. The demo below illustrates this:
// setup error handler to use JMS as queue and store the entire Exchange
errorHandler(deadLetterChannel("jms:queue:dead?transferExchange=true"));
Then you can consume from the JMS queue and analyze the problem:
from("jms:queue:dead").to("bean:myErrorAnalyzer");
// and in our bean
String body = exchange.getIn().getBody();
Exception cause = exchange.getProperty(Exchange.EXCEPTION_CAUGHT, Exception.class);
367
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
// the cause message is
String problem = cause.getMessage();
Using JMS as Dead Letter Channel storing error only
You can use JMS to store the cause error message or a custom body as you can set as you like.
We use Message Translator EIP to do a transformation on the failed exchange before its moved
to the JMS dead letter queue. The demo below illustrates this:
// we sent it to a seda dead queue first
errorHandler(deadLetterChannel("seda:dead"));
// and on the seda dead queue we can do the custom transformation before its sent to
the JMS queue
from("seda:dead").transform(exceptionMessage()).to("jms:queue:dead");
Here we only store the original cause error message in the transform. You can however use
any Expression to send whatever you like. Eg you can invoke a method on a Bean, use a custom
processor or what else.
See Also
•
•
•
•
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
Transactional Client
Bean Integration
Tutorial-JmsRemoting
JMSTemplate gotchas
JPA COMPONENT
The jpa: component allows you to work with databases using JPA (EJB 3 Persistence) such as
for working with OpenJPA, Hibernate, TopLink to work with relational databases.
Sending to the endpoint
Sending POJOs to the JPA endpoint inserts entities into the database. The body of the message
is assumed to be an entity bean (i.e. a POJO with an @Entity annotation on it).
If the body does not contain an entity bean then use a Message Translator in front of the
endpoint to perform the necessary conversion first.
CH APT ER 10 - CO M PO N EN T APPEN DIX
368
Consuming from the endpoint
Consuming messages removes (or updates) entities in the database. This allows you to use a
database table as a logical queue, consumers take messages from the queue and then delete/
update them to logically remove them from the queue.
If you do not wish to delete the entity when it has been processed you can specify
consumeDelete=false on the URI. This will result in the entity being processed each poll.
If you would rather perform some update on the entity to mark it as processed (such as to
exclude it from a future query) then you can annotate a method with @Consumed which will
be invoked on your entity bean when the entity bean is consumed.
URI format
jpa:[entityClassName]?options
For sending to the endpoint, the entityClassName is optional. If specified it is used to help
use the Type Converter to ensure the body is of the correct type.
For consuming the entityClassName is mandatory.
Options
369
Name
Default
Value
Description
entityType
entityClassName
Is the provided entityClassName from the
URI
persistenceUnit
camel
the JPA persistence unit used by default
consumeDelete
true
Option for JpaConsumer only. Enables /
disables whether or not the entity is deleted
after it is consumed.
consumeLockEntity
true
Option for JpaConsumer only. Enables /
disables whether or not to use exclusive
locking of each entity while processing the
results from the pooling.
flushOnSend
true
Option for JpaProducer only. Flushes the
EntityManager after the entity beans has
been persisted.
maximumResults
-1
Option for JpaConsumer only. Set the
maximum number of results to retrieve on
the Query.
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
transactionManager
null
Camel 1.6.1/2.0: Sets the transaction
manager to use. If none provided Camel will
default use JpaTransactionManager.
Can be used to set a JTA transaction
manager.
consumer.delay
500
Option for JpaConsumer only. Delay in
millis between each poll.
consumer.initialDelay
1000
Option for JpaConsumer only. Millis before
polling starts.
false
Option for JpaConsumer only. true to use
fixed delay between pools, otherwise fixed
rate is used. See ScheduledExecutorService
in JDK for details.
consumer.userFixedDelay
Configuring EntityManagerFactory
You can configure the EntityManagerFactory to use on the JpaComponent itself. For instance in
Spring XML:
<bean id="jpa" class="org.apache.camel.component.jpa.JpaComponent">
<property name="entityManagerFactory" ref="myEMFactory"/>
</bean>
Configuring TransactionManager
You can configure the TransactionManager to use on the JpaComponent itself. For instance in
Spring XML:
<bean id="jpa" class="org.apache.camel.component.jpa.JpaComponent">
<property name="entityManagerFactory" ref="myEMFactory"/>
<property name="transactionManager" ref="myTransactionManager"/>
</bean>
Example
See Tracer Example for an example using JPA to store traced messages into a database.
See Also
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
CH APT ER 10 - CO M PO N EN T APPEN DIX
370
• Tracer Example
JT/400 COMPONENT
The jt400: component allows you to exchanges messages with an AS/400 system using data
queues. This components is only available in Camel 1.5 and above.
URI format
jt400://user:password@system/QSYS.LIB/LIBRARY.LIB/QUEUE.DTAQ
URI options
Name
Default
value
Description
ccsid
default
system
CCSID
specifies the CCSID to use for the
connection with the AS/400 system
format
text
specifies the data format for sending
messages
valid options are: text (represented by
String) and binary (represented by
byte[])
consumer.delay
500
Delay in millis between each poll
consumer.initialDelay
1000
Millis before polling starts
false
true to use fixed delay between pools,
otherwise fixed rate is used. See
ScheduledExecutorService in JDK for
details.
consumer.userFixedDelay
Usage
When configured as a consumer endpoint, the endpoint will poll a data queue on a remote
system. For every entry on the data queue, a new Exchange is sent with the entry's data in the
'in' message's body, formatted as either a String or a byte[], depending on the format.
For a provider endpoint, the 'in' message body contents will be put on the data queue as
either raw bytes or text.
371
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
Example
In the snippet below, the data for an exchange sent to the direct:george will be put in the
data queue PENNYLANE in library BEATLES on a system named LIVERPOOL.
Another user connects to the same data queue to receive the information from the data queue
and forward it to the mock:ringo endpoint.
public class Jt400RouteBuilder extends RouteBuilder {
@Override
public void configure() throws Exception {
from("direct:george").to("jt400://GEORGE:EGROEG@LIVERPOOL/QSYS.LIB/BEATLES.LIB/
PENNYLANE.DTAQ");
from("jt400://RINGO:OGNIR@LIVERPOOL/QSYS.LIB/BEATLES.LIB/
PENNYLANE.DTAQ").to("mock:ringo");
}
}
See Also
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
LDAP COMPONENT
The ldap: component allows you to perform searches in LDAP servers using filters as the
message payload.
This component uses standard JNDI (javax.naming) to access the server.
URI format
ldap:ldapServerBean?options
This component only supports producer, meaning that you can not use routes with this
component in the from type.
Options
Name
Default
Value
Description
base
ou=system
The base DN for searches
CH APT ER 10 - CO M PO N EN T APPEN DIX
372
scope
subtree
Search the whole subtree. Value must be one of: "object",
"onelevel" or "subtree"
Result
The result is returned in the out body as a
ArrayList<javax.naming.directory.SearchResult> list object with the result.
DirContext
The ldapServerBean portion of the URI refers to a DirContext bean in the registry.
Given an ldapServerBean of "ldapserver", a bean may be declared via Spring as:
<bean id="ldapserver" class="javax.naming.directory.InitialDirContext"
scope="prototype">
<constructor-arg>
<props>
<prop key="java.naming.factory.initial">com.sun.jndi.ldap.LdapCtxFactory</prop>
<prop key="java.naming.provider.url">ldap://localhost:10389</prop>
<prop key="java.naming.security.authentication">none</prop>
</props>
</constructor-arg>
</bean>
The above declares a regular Sun based LDAP DirContext that connects anonymously to a
locally hosted LDAP server.
Samples
Following on from the Spring configuration above, the code sample below sends an ldap request
to filter search a group for a member. The common name is then extracted from the response.
ProducerTemplate<Exchange> template = exchange
.getContext().createProducerTemplate();
Collection<?> results = (Collection<?>) (template
.sendBody(
"ldap:ldapserver?base=ou=mygroup,ou=groups,ou=system",
"(member=uid=huntc,ou=users,ou=system)"));
if (results.size() > 0) {
// Extract what we need from the device's profile
Iterator<?> resultIter = results.iterator();
SearchResult searchResult = (SearchResult) resultIter
.next();
Attributes attributes = searchResult
.getAttributes();
Attribute deviceCNAttr = attributes.get("cn");
String deviceCN = (String) deviceCNAttr.get();
373
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
DirContext objects are not required to support concurrency by contract. It is therefore
important that the directory context is declared as scope="prototype" (in the case when
using Spring) or that the context supports concurrency. Prototype scoped objects are
instantiated each time they are looked up.
Camel 1.6.1 and Camel 2.0 include a fix to support by concurrency for LDAP producers.
ldapServerBean contexts are now looked up each time a request is sent to the LDAP server.
In addition the contexts are released as soon as the producer completes.
...
If no specific filter is required i.e. you just need to look an entry up, specify a wildcard filter
expression. In the case where there is a common name use a filter expression like:
(cn=*)
See Also
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
LIST COMPONENT
deprecated: is renamed to the Browse component in Camel 2.0
The List 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
list:someName
Where someName can be any string to uniquely identify the endpoint.
CH APT ER 10 - CO M PO N EN T APPEN DIX
374
Sample
In the route below we have the list component to be able to browse the Exchanges that is
passed through:
from("activemq:order.in").to("list:orderReceived").to("bean:processOrder");
Then we will be able to inspect the received exchanges from java code:
private CamelContext context;
public void inspectRecievedOrders() {
BrowsableEndpoint browse = context.getEndpoint("list: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
Browse
LOG COMPONENT
The log: component logs message exchanges to the underlying logging mechanism.
Camel uses commons-logging which allows you to configure logging via
• Log4j
• JDK 1.4 logging
• Avalon
• SimpleLog - a simple provider in commons-logging
Refer to the commons-logging user guide for a more complete overview of how to use and
configure commons-logging.
URI format
log:loggingCategory[?level=loggingLevel][options]
Where loggingCategory is the name of the logging category to use and loggingLevel is
the logging level such as DEBUG, INFO, WARN, ERROR - the default is INFO
375
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
By default Camel uses a regular logging that logs every exchange. However Camel also ships
with a Throughput logger that is used if the groupSize option is specified.
Options
Option
Default
Type
Description
level
INFO
String
Logging level to use. Possible values: FATAL, ERROR,
WARN, INFO, DEBUG, TRACE, OFF
groupSize
null
Integer
An integer that specifies a group size for throughput
logging. By default regular logging is used.
Formatting
The log formats the execution of exchanges to log lines.
The log uses by default LogFormatter to format the log output.
LogFormatter has the following options:
Option
Default
Description
showExchangeId
false
To output the unique exchange id.
showProperties
false
Output the exchange properties
showHeaders
false
Output the in message headers
showBodyType
true
Output the in body Java type
showBody
true
Output the in body
showOut
false
If the exchange has an out message then its also shown
showAll
false
quick option for turning all options on
multiline
false
if enabled then each information is logged on a new line
maxChars
Camel 2.0: Is used to limit the number of chars logged per
line.
Regular logger sample
In the route below we logs the incoming orders at DEBUG level before the order is processed.
from("activemq:orders").to("log:com.mycompany.order?level=DEBUG").to("bean:processOrder");
And using Spring DSL as the route:
<route>
<from uri="activemq:orders"/>
<to uri="log:com.mycompany.order?level=DEBUG"/>
CH APT ER 10 - CO M PO N EN T APPEN DIX
376
<to uri="bean:processOrder"/>
</route>
Regular logger with formatter sample
In the route below we logs the incoming orders at INFO level before the order is processed.
from("activemq:orders").
to("log:com.mycompany.order?showAll=true&multiline=true").to("bean:processOrder");
Throughput logger sample
In the route below we log the throughput of the incoming orders at DEBUG level grouped by
10 messages.
from("activemq:orders").
to("log:com.mycompany.order?level=DEBUG?groupSize=10").to("bean:processOrder");
See Also
•
•
•
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
Tracer
How do I use log4j
How do I use Java 1.4 logging
MAIL COMPONENT
The mail component provides access to Email via Spring's Mail support and the underlying
JavaMail system.
URI format
smtp://[user-info@]host:port[?password=somepwd]
pop3://[user-info@]host:port[?password=somepwd]
imap://[user-info@]host:port[?password=somepwd]
which supports either POP, IMAP or SMTP underlying protocols.
It is possible to omit the user-info and specify the username as a URI parameter instead
smtp://host:port?password=somepwd&username=someuser
Such as:
smtp://mycompany.mailserver:30?password=tiger&username=scott
377
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
Classpath issue
If you have trouble with sending mails that for instance doesn't contain any subject, has
wrong recipients or other unforeseen errors then it could be because of having
geronimo-javamail_1.4_spec-1.3.jar in the classpath. This was the culprit in a
long bug hunt reported in CAMEL-869.
Geronimo mail .jar
We have discovered that the geronimo mail .jar (v1.6) have a bug when polling mails with
attachments. It cannot correctly identify Content-Type. So if you attach a jepg file to a
mail and you poll it then the Content-Type is resolved as text/plain and not as
image/jpeg. For that reason we have added a
org.apache.camel.component.ContentTypeResolver SPI interface where
you can provide your own implementation and fix this by returning the correct mime type
based on the file name. So if the file name ends with jpeg/jpg you can return image/
jpeg.
You can set your custom resolver on the MailComponent or the MailEndpoint. This
feature is added in Camel 1.6.2/2.0.
POP3 or IMAP
POP3 has some limitations and end users is encouraged to use IMAP if possible.
SSL support
Camel have support for secure mail protocols. Just add a s to the scheme such as:
smtps://[user-info@]host:port[?password=somepwd]
pop3s://[user-info@]host:port[?password=somepwd]
imaps://[user-info@]host:port[?password=somepwd]
Default Ports
As of Camel 1.4 support for default port number has been added. If the port number is omitted
Camel will determine based on the protocol the port number to use.
Protocol
Default Port Number
SMPT
25
CH APT ER 10 - CO M PO N EN T APPEN DIX
378
SSL Information
Its the underlying mail framework that is handling the SSL support. Camel uses SUN
JavaMail. However SUN JavaMail only trusts certificates issued by well known Certificate
Authorities. So if you have issued your own certificate you have to import it into the local
Java keystore file (see SSLNOTES.txt in JavaMail for details).
If you are using your own signed certificates sometimes it can be cumbersome to install
your certificate in the local keystore. Camel provides a test option
dummyTrustManager that when enabled will accept any given certificate.
Notice: this is strongly discouraged not using in production environments.
SMPTS
465
POP3
110
POP3S
995
IMAP
143
IMAPS
993
Options
Property
Default
host
port
379
Description
The host name or IP address to connect to
See Default
Ports
The TCP port number to connect on
user-info
The user name on the email server
username
The user name on the email server configured as a URI pa
password
null
The users password to use, can be omitted if the mail serv
ignoreUriScheme
false
If disabled Camel will use the scheme to determine the tra
imap, smtp etc.)
defaultEncoding
null
The default encoding to use for MineMessages
contentType
text/plain
New option in Camel 1.5. The mail message content type.
mails.
folderName
INBOX
The folder to poll
destination
user-info@host
@deprecated use To option. The TO recipients (the re
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
to
user-info@host
The TO recipients (the receivers of the mail). This option
CC
null
The CC recipients (the receivers of the mail). This option
BCC
null
The BCC recipients (the receivers of the mail). This optio
from
camel@localhost
The FROM email address
deleteProcessedMessages
true/false
Deletes the messages after they have been processed. Thi
DELETED flag on the mail message. If false then the flag S
1.5 the default setting is now false.
delete
false
Camel 2.0: Deletes the messages after they have been pro
the DELETED flag on the mail message. If false then the f
processOnlyUnseenMessages
false/true
As of Camel 1.4 its possible to configure MailConsumer to
(eg new messages) or all. Note Camel will always skip dele
option to true will filter to only unseen messages. As of C
now true. POP3 does not support the SEEN flag so this o
POP3, instead use IMAP.
unseen
true
Camel 2.0: Is used to only fetch unseen messages (eg new
not support the SEEN flag, instead use IMAP.
fetchSize
-1
As of Camel 1.4 a maximum number of messages to consu
This can be used to not exhaust a mail server if a mailbox
messages. Default value of -1 means no fetch size and all m
Setting the value to 0 is a special corner case where Came
at all.
debugMode
false
As of Camel 1.4 its possible to enable the debug mode on
SUN Mail framework will default output to System.out.
connectionTimeout
30000
As of Camel 1.4 the connection timeout can be configured
dummyTrustManager
false
As of Camel 1.4 testing SSL connections can be easier if en
that trust any given certificate. Notice this is only to be us
provide any security at all.
consumer.initialDelay
1000
Millis before the polling starts
consumer.delay
60000
As of Camel 1.4 the default consumer delay is now 60 sec
poll the mailbox once a minute to not exhaust the mail se
1.3 is 500 millis.
consumer.useFixedDelay
false
true to use fixed delay between pools, otherwise fixed ra
ScheduledExecutorService in JDK for details.
CH APT ER 10 - CO M PO N EN T APPEN DIX
380
mail.XXX
null
As of Camel 2.0 you can set any additional java mail pro
to set a special property when using POP3 you can now p
URI such as: mail.pop3.forgettopheaders=true
options, such as:
mail.pop3.forgettopheaders=true&mail.mim
Defaults changed in Camel 1.4
As of Camel 1.4 the default consumer delay is now 60 seconds. Camel will therefore only poll
the mailbox once a minute to not exhaust the mail server. The default value in Camel 1.3 is 500
millis.
Defaults changed in Camel 1.5
In Camel 1.5 the following default options has changed:
• deleteProcessedMessages is now false as we felt Camel should not delete
mails on the mail server by default.
• processOnlyUnseenMessages is now true as we felt Camel should only poll
new mails by default.
Mail Message Content
Camel will use the Exchange Message IN body as the MimeMessage text content. The body is
converted to String.class.
Camel copies all the Exchange Message IN headers to the MimeMessage headers.
The subject of the MimeMessage can be configured using a header property on the in
message. The code below demonstrates this:
from("direct:a").setHeader("subject", constant(subject)).to("smtp://james2@localhost");
The same applies for other MimeMessage headers such as recipients, so you can use a header
property as the TO:
Map map = new HashMap();
map.put("To", "davsclaus@apache.org");
map.put("From", "jstrachan@apache.org");
map.put("Subject", "Camel rocks");
String body = "Hello Claus.\nYes it does.\n\nRegards James.";
template.sendBodyAndHeaders("smtp://davsclaus@apache.org", body, map);
Headers take precedence over pre configured recipeients
From Camel 1.5 onwards the recipients from the message headers will always take precedence
over any pre configured. The idea is that if you provide any recipients in the message headers
381
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
then its what you get (WYSIWYG). The pre configuration is just there for fallback or if you use
fixed recipients.
In the sample code below the mail is sent to davsclaus@apache.org since it will take
precedence over the pre configured. Even if we have CC pre configured they will not recieve
the mail. The headers is all or nothing, it will not mix and match between headers and pre
configured. You either get one or the other.
Map<String, Object> headers = new HashMap<String, Object>();
headers.put("to", "davsclaus@apache.org");
template.sendBodyAndHeaders("smtp://admin@localhost?to=info@mycompany.com",
"Hello World", headers);
Multiple recipients easier configuration
Also new in Camel 1.5 is the possibility to set multiple recipients in a single String parameter.
This applied to both the headers and pre configuration.
Map<String, Object> headers = new HashMap<String, Object>();
headers.put("to", "davsclaus@apache.org ; jstrachan@apache.org ;
ningjiang@apache.org");
In the sample above we use semi colon as separators. Camel support both semicolon = ;
and comma = , as separator char.
SUN JavaMail
SUN JavaMail is used under the covers for consuming and producing mails.
We encourage end-users to consult these links when using either POP3 or IMAP protocol.
Notice that especially POP3 have limited features compared to IMAP.
• SUN POP3 API
• SUN IMAP API
• And generally about the MAIL Flags
Samples
We start with a simple route that sends the messages received from a JMS queue as emails. The
email account with be the admin account on mymailserver.com.
from("jms://queue:subscription").to("smtp://admin@mymailserver.com?password=secret");
In the next sample we will poll a mailbox for new emails once every minute. Notice that we use
the special consumer parameter for setting the poll interval consumer.delay as 60000 millis
= 60 seconds.
from("imap://admin@mymailserver.com?password=secret&processOnlyUnseenMessages=true&consumer.delay=6000
CH APT ER 10 - CO M PO N EN T APPEN DIX
382
In this sample we want to send a mail to multiple recipients. This feature was introduced in
camel 1.4.
// all the recipients of this mail are:
// To: camel@riders.org , easy@riders.org
// CC: me@you.org
// BCC: someone@somewhere.org
String recipients =
"&To=camel@riders.org,easy@riders.org&CC=me@you.org&BCC=someone@somewhere.org";
from("direct:a").to("smtp://you@mymailserver.com?password=secret&From=you@apache.org"
+ recipients);
Sending mail with attachment sample
Attachments is a new feature in Camel 1.4 that of course is also supported by the mail
component. In the sample below we send a mail message containing a plain text message with a
logo file attachment.
// create an exchange with a normal body and attachment to be produced as email
Endpoint endpoint =
context.getEndpoint("smtp://james@mymailserver.com?password=secret");
// create the exchange with the mail message that is multipart with a file and a Hello
World text/plain message.
Exchange exchange = endpoint.createExchange();
Message in = exchange.getIn();
in.setBody("Hello World");
in.addAttachment("logo.jpeg", new DataHandler(new FileDataSource("src/test/data/
logo.jpeg")));
// create a producer that can produce the exchange (= send the mail)
Producer producer = endpoint.createProducer();
// start the producer
producer.start();
// and let it go (processes the exchange by sending the email)
producer.process(exchange);
SSL sample
In this sample we want to poll our Google mail inbox for mails. Google mail requires to use SSL
and have it configured for other clients to access your mailbox. This is done by logging into
your google mail and change your settings to allow IMAP access. Google have extensive
documentation how to do this.
from("imaps://imap.gmail.com?username=YOUR_USERNAME@gmail.com&password=YOUR_PASSWORD"
+
"&deleteProcessedMessages=false&processOnlyUnseenMessages=true&consumer.delay=60000").to("log:newmail"
The route above will poll the google mail inbox for new mails once every minute and log it to
the newmail logger category.
Running the sample with DEBUG logging enabled we can monitor the progress in the logs:
383
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
2008-05-08 06:32:09,640 DEBUG MailConsumer - Connecting to MailStore
imaps//imap.gmail.com:993 (SSL enabled), folder=INBOX
2008-05-08 06:32:11,203 DEBUG MailConsumer - Polling mailfolder:
imaps//imap.gmail.com:993 (SSL enabled), folder=INBOX
2008-05-08 06:32:11,640 DEBUG MailConsumer - Fetching 1 messages. Total 1 messages.
2008-05-08 06:32:12,171 DEBUG MailConsumer - Processing message: messageNumber=[332],
from=[James Bond <007@mi5.co.uk>], to=YOUR_USERNAME@gmail.com], subject=[...
2008-05-08 06:32:12,187 INFO newmail - Exchange[MailMessage: messageNumber=[332],
from=[James Bond <007@mi5.co.uk>], to=YOUR_USERNAME@gmail.com], subject=[...
SSL sample with dummyTrustManager
In the next sample we want to sent mails from Camel using our own mail server using secure
connections. As our own mail server is using our own signed certificate we need either to
1. install our certificate in the local keystore Camel uses
2. use the dummyTrustManager option for testing purpose to see if the secure
communication works
In the sample we use the dummyTrustManager option:
from("seda:mailsToSend").to("imaps://ourmailsserver.com?username=camelmail&password=secret&dummyTrustM
Consuming mails with attachment sample
In this sample we poll a mailbox and want to store all attachments from the mails as files. First
we define our route to poll the mailbox. As this sample is based on google mail, it uses the
same route as shown in the SSL sample:
from("imaps://imap.gmail.com?username=YOUR_USERNAME@gmail.com&password=YOUR_PASSWORD"
+
"&deleteProcessedMessages=false&processOnlyUnseenMessages=true&consumer.delay=60000").process(new
MyMailProcessor());
Instead of logging the mail we use a processor where we can process the mail from java code:
public void process(Exchange exchange) throws Exception {
// the API is a bit clunky so we need to loop
Map<String, DataHandler> attachments = exchange.getIn().getAttachments();
if (attacments.size() > 0) {
for (String name : attachments.keySet()) {
DataHandler dh = attachments.get(name);
// get the file name
String filename = dh.getName();
// get the content and convert it to byte[]
byte[] data =
exchange.getContext().getTypeConverter().convertTo(byte[].class, dh.getInputStream());
// write the data to a file
FileOutputStream out = new FileOutputStream(filename);
out.write(data);
out.flush();
out.close();
CH APT ER 10 - CO M PO N EN T APPEN DIX
384
}
}
}
As you can see the API to handle attachments is a bit clunky but it's there so you can get the
javax.activation.DataHandler so you can handle the attachments using standard
API.
See Also
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
MINA COMPONENT
The mina: component is a transport for working with Apache MINA
URI format
mina:tcp://hostname[:port]
mina:udp://hostname[:port]
mina:multicast://hostname[:port]
mina:vm://hostname[:port}
From Camel 1.3 onwards you can specify a codec in the Registry using the codec option. If you
are using TCP and no codec is specified then the textline flag is used to determine if text line
based codec or object serialization should be used instead. By default the object serialization is
used.
For UDP/Multicast if no codec is specified the default uses a basic ByteBuffer based codec.
Multicast also has a shorthand notation mcast.
The VM protocol is used as a direct forwarding mechanism in the same JVM. See the MINA
VM-Pipe API documentation for details.
A MinaProducer has a default timeout value of 30 seconds, while it waits for a response
from the remote server.
In normal usage camel-mina only supports marshalling the body content - message headers
and exchange properties will not be sent.
However the option transferExchange does allow to transfer the exchange itself over the
wire. See options below.
385
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
Options
Default
Value
Description
null
As of 1.3 or later you can refer to a named
ProtocolCodecFactory instance in your Registry such as
your Spring ApplicationContext which is then used for
the marshalling
null
Camel 2.0: You must use the # notation to lookup
your codec in the Registry. eg use #myCodec to lookup
a bean with the id myCodec.
false
Only used for TCP. If no codec is specified then you can
use this flag in 1.3 or later to indicate a text line based
codec; if not specified or the value is false then Object
Serialization is assumed over TCP.
DEFAULT
Camel 1.5.1/2.0 Only used for TCP and if
textline=true. Sets the text line delimiter to use.
Possible values are: DEFAULT, AUTO, WINDOWS, UNIX
or MAC. If none provided Camel will default use
DEFAULT. This delimiter is used to mark the end of
text.
sync
false/true
As of 1.3 or later you can configure the exchange
pattern to be either InOnly (default) or InOut. Setting
sync=true means a synchronous exchange (InOut),
where the client can read the response from MINA (The
exchange out message). The default value has changed in
Camel 1.5 to true. In older releases the default value is
false.
lazySessionCreation
See
description
As of 1.3 or later session can be lazy created to avoid
exceptions if the remote server is not up and running
when the Camel producer is started. Is default false in
Camel 1.x. Is default true in Camel 2.0 onwards.
30000
As of 1.3 or later you can configure the timeout while
waiting for a response from a remote server. The
timeout unit is in millis, so 60000 is 60 seconds. The
timeout is only used for MinaProducer.
Option
codec
codec
textline
textlineDelimiter
timeout
CH APT ER 10 - CO M PO N EN T APPEN DIX
386
JVM
Default
As of 1.3 or later you can configure the encoding (is a
charset name) to use for the TCP textline codec and the
UDP protocol. If not provided Camel will use the JVM
default Charset.
transferExchange
false
Only used for TCP. As of 1.3 or later you can transfer
the exchange over the wire instead of just the body. The
following fields is transferred: in body, out body, fault
body, in headers, out headers, fault headers, exchange
properties, exchange exception. This requires that the
objects are Serializable. Camel will exclude any non
serializable objects and log it at WARN level.
minaLogger
false
As of 1.3 or later you can enable Apache MINA logging
filter. Apache MINA uses slf4j logging at INFO level to
log all input and output.
filters
null
As of 2.0 or later you can set a list of Mina IoFilters to
register. The type must be
List<org.apache.mina.common.IoFilter>.
encoding
Default behavior changed
In Camel 2.0 the codec option must use # notation for lookup of the codec bean in the
Registry.
In Camel 2.0 the lazySessionCreation option is now default true.
In Camel 1.5 the sync option has changed its default value from false to true, as we felt it
was confusing for end-users when they used Mina to call remote servers and Camel wouldn't
wait for the response.
In Camel 1.4 or later codec=textline is no longer supported. Use the
textline=true option instead.
Using custom codec
See the Mina documentation how to write your own codec. To use your custom codec with
camel-mina you should register your codec in the Registry such as the Spring XML file. Then
use the codec option to set your codec with its bean id. See HL7 that has a custom codec.
Sample with sync=false
In this sample we let Camel expose a service that listen for TCP connections on port 6200. We
use the textline codec. In out route we create the mina in the from to create the consumer
that listen on port 6200:
387
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
from("mina:tcp://localhost:6200?textline=true&sync=false").to("mock:result");
As the sample is part of an unit test we test it by sending some data on port 6200 to it.
MockEndpoint mock = getMockEndpoint("mock:result");
mock.expectedBodiesReceived("Hello World");
template.sendBody("mina:tcp://localhost:6200?textline=true&sync=false", "Hello World");
assertMockEndpointsSatisfied();
Sample with sync=true
In the next sample we have a more common use-case where we expose a TCP service on port
6201 also using the textline codec. However this time we want to return a response and
indicate that we support this so we set the sync option to true on the consumer.
from("mina:tcp://localhost:6201?textline=true&sync=true").process(new Processor() {
public void process(Exchange exchange) throws Exception {
String body = exchange.getIn().getBody(String.class);
exchange.getOut().setBody("Bye " + body);
}
});
Then we test it by sending some data and retrieving the response using the
template.requestBody() method. As we know the response is a String we cast it to
String and can assert that the response is in fact something we have dynamically set in our
processor code logic.
String response =
(String)template.requestBody("mina:tcp://localhost:6201?textline=true&sync=true",
"World");
assertEquals("Bye World", response);
Sample with Spring DSL
Spring DSL can of course also be used for Mina. In the simple sample below we expose a TCP
server on port 5555:
<route>
<from uri="mina:tcp://localhost:5555?textline=true"/>
<to uri="bean:myTCPOrderHandler"/>
</route>
In the route above we expose a TCP server on port 5555 using the textline codec and we let a
spring bean with the id myTCPOrderHandler handle the request and return a reply. For
instance this can be done as:
public String handleOrder(String payload) {
...
return "Order: OK"
}
CH APT ER 10 - CO M PO N EN T APPEN DIX
388
Configuring Mina endpoints using Spring bean style
Avaiable as of Camel 2.0
Configuration of Mina endpoints is now possible using regular Spring bean style configuration
in the Spring DSL.
However configuring Apache Mina itself is quite complex to setup the acceptor, connector
as you can not use simple setters. To resolve this we will leverage the MinaComponent as a
Spring factory bean to configure this for us. If you really need to configure this yourself there
are setters on the MinaEndpoint to set these when needed.
The sample below shows the factory approach:
<!-- Creating mina endpoints is a bit complex so we reuse MinaComponnet
as a factory bean to create our endpoint, this is the easiest to do -->
<bean id="myMinaFactory" class="org.apache.camel.component.mina.MinaComponent">
<!-- we must provide a camel context so we refer to it by its id -->
<constructor-arg index="0" ref="myCamel"/>
</bean>
<!-- This is our mina endpoint configured with spring, we will use the factory above
to create it for us. The goal is to invoke the createEndpoint method with the
mina configuration parameter we defined using the constructor-arg option -->
<bean id="myMinaEndpoint"
factory-bean="myMinaFactory"
factory-method="createEndpoint">
<!-- and here we can pass it our configuration -->
<constructor-arg index="0" ref="myMinaConfig"/>
</bean>
<!-- this is our mina configuration with plain properties -->
<bean id="myMinaConfig" class="org.apache.camel.component.mina.MinaConfiguration">
<property name="protocol" value="tcp"/>
<property name="host" value="localhost"/>
<property name="port" value="1234"/>
<property name="sync" value="false"/>
</bean>
And then we can refer to our endpoint directly in the route such as:
<route>
<!-- here we route from or mina endpoint we have defined above -->
<from ref="myMinaEndpoint"/>
<to uri="mock:result"/>
</route>
Closing Session When Complete
Avaiable as of Camel 1.6.1
When acting as a server you sometimes want to close the session when e.g. a client
conversion is finished. To instruct Camel to close the session you should set add a header with
the key CamelMinaCloseSessionWhenComplete to a boolean true value.
389
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
For instance the example below will close the session after it have written the bye message
back to the client:
from("mina:tcp://localhost:8080?sync=true&textline=true").process(new Processor() {
public void process(Exchange exchange) throws Exception {
String body = exchange.getIn().getBody(String.class);
exchange.getOut().setBody("Bye " + body);
exchange.getOut().setHeader(MinaConsumer.HEADER_CLOSE_SESSION_WHEN_COMPLETE, true);
}
});
Configuring Mina filters
Avaiable as of Camel 2.0
Filters permits you to use some Mina Filters, such as SslFilter. You can also implement some
customized filters. Please note that codec and logger are also Mina IoFitler, and the filters
you may define are appended at the end of the FilterChain, then after codec and logger.
For instance, the example below will send a keep-alive message after 10 seconds of inactivity:
public class KeepAliveFilter extends IoFilterAdapter {
@Override
public void sessionCreated(NextFilter nextFilter, IoSession session)
throws Exception {
session.setIdleTime(IdleStatus.BOTH_IDLE, 10);
nextFilter.sessionCreated(session);
}
@Override
public void sessionIdle(NextFilter nextFilter, IoSession session,
IdleStatus status) throws Exception {
session.write("NOOP"); // NOOP is a FTP command for keep alive
nextFilter.sessionIdle(session, status);
}
}
As Camel Mina may ues a request-reply scheme, the endpoint as a client would like to drop
some message, such as greeting when the connection is established. For example, when you
connect to an FTP server, you will get a 220 message with a greeting (220 Welcome to
Pure-FTPd). If you don't drop the message, you request-reply scheme will be broken.
public class DropGreetingFilter extends IoFilterAdapter {
@Override
public void messageReceived(NextFilter nextFilter, IoSession session,
Object message) throws Exception {
if (message instanceof String) {
String ftpMessage = (String) message;
// "220" is given as greeting. "200 Zzz" is given as a response to "NOOP"
(keep alive)
if (ftpMessage.startsWith("220") || or ftpMessage.startsWith("200 Zzz")) {
CH APT ER 10 - CO M PO N EN T APPEN DIX
390
// Dropping greeting
return;
}
}
nextFilter.messageReceived(session, message);
}
}
Then, you can configure your endpoint. Using Spring DSL:
<bean id="myMinaFactory" class="org.apache.camel.component.mina.MinaComponent">
<constructor-arg index="0" ref="camelContext" />
</bean>
<bean id="myMinaEndpoint"
factory-bean="myMinaFactory"
factory-method="createEndpoint">
<constructor-arg index="0" ref="myMinaConfig"/>
</bean>
<bean id="myMinaConfig" class="org.apache.camel.component.mina.MinaConfiguration">
<property name="protocol" value="tcp" />
<property name="host" value="localhost" />
<property name="port" value="2121" />
<property name="sync" value="true" />
<property name="minaLogger" value="true" />
<property name="filters" ref="listFilters"/>
</bean>
<bean id="listFilters" class="java.util.ArrayList" >
<constructor-arg>
<list value-type="org.apache.mina.common.IoFilter">
<bean class="com.example.KeepAliveFilter"/>
<bean class="com.example.DropGreetingFilter"/>
</list>
</constructor-arg>
</bean>
See Also
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
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.
391
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
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 ran 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
• that the correct payloads are received, in the right order
• that messages arrive on an endpoint in order, using some Expression to create an
order testing function
• that 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 also uses a
second endpoint to provide the list of expected message bodies and automatically sets up the
Mock endpoint assertions. i.e. its a Mock endpoint which 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 to uniquely identify the endpoint
Options
Option
Default
Description
reportGroup
null
A size to use a throughput logger for reporting
Simple Example
Here's a simple example of MockEndpoint in use. First the endpoint is resolved on the context.
Then we set an expectation, then after the test has run we assert our expectations are 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.
CH APT ER 10 - CO M PO N EN T APPEN DIX
392
Camel will by default wait 20 seconds when the assertIsSatisfied() is invoked. This
can be configured by setting the setResultWaitTime(millis) method.
Setting expectations
You can see from the javadoc of MockEndpoint the various helper methods you can use to set
expectations. The main methods available 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 this code
resultEndpoint.message(0).header("foo").isEqualTo("bar");
393
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
There are some examples of the Mock endpoint in use in the camel-core processor tests.
A Spring Example
First here's the spring.xml file
<camelContext xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="file:src/test/data?noop=true"/>
<filter>
<xpath>/person/city = 'London'</xpath>
<to uri="mock:matched"/>
</filter>
</route>
</camelContext>
<bean id="myBean" class="org.apache.camel.spring.mock.MyAssertions" scope="singleton"/>
As you can see it defines a simple routing rule which consumes messages from the local src/
test/data directory. The noop flag just means not to delete or move the file after its been
processed.
Also note we instantiate a bean called myBean, here is the source of the MyAssertions
bean.
public class MyAssertions implements InitializingBean {
@EndpointInject(uri = "mock:matched")
private MockEndpoint matched;
@EndpointInject(uri = "mock:notMatched")
private MockEndpoint notMatched;
public void afterPropertiesSet() throws Exception {
// lets add some expectations
matched.expectedMessageCount(1);
notMatched.expectedMessageCount(0);
}
public void assertEndpointsValid() throws Exception {
// now lets perform some assertions that the test worked as we expect
Assert.assertNotNull("Should have a matched endpoint", matched);
Assert.assertNotNull("Should have a notMatched endpoint", notMatched);
MockEndpoint.assertIsSatisfied(matched, notMatched);
}
}
The bean is injected with a bunch of Mock endpoints using the @EndpointInject annotation, it
then sets a bunch of expectations on startup (using Spring's InitializingBean interface and
afterPropertiesSet() method) before the CamelContext starts up.
Then in our test case (which could be JUnit or TesNG) we lookup myBean in Spring (or
have it injected into our test) and then invoke the assertEndpointsValid() method on it to
verify that the mock endpoints have their assertions met. You could then inspect the message
CH APT ER 10 - CO M PO N EN T APPEN DIX
394
exchanges that were delivered to any of the endpoints using the getReceivedExchanges()
method on the Mock endpoint and perform further assertions or debug logging.
Here is the actual JUnit test case we use.
See Also
•
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
Spring Testing
MSMQ COMPONENT
The msmq: component is a transport for working with Microsoft Message Queuing
This component natively sends and receives direct allocated ByteBuffer instances. This allows to
access the JNI layer without expensive memory copying.
In fact using ByteBuffer created with the method allocateDirect can be passed to the JNI layer
and the native code is able to directly access the memory.
It's up to the developer to marshal/unmarshal any other kind of payloads to/from direct
allocated ByteBuffer instances.
Look at the tests to see some usage examples.
URI format
msmq:msmqQueueName
Examples
msmq:DIRECT=OS:localhost\\private$\\test?concurrentConsumers=1
msmq:DIRECT=OS:localhost\\private$\\test?deliveryPersistent=true&priority=5
Options
395
Name
Default
Value
Description
deliveryPersistent
false
if true the message is put persistently on the queue
priority
5
the message priority, it's a value in the range 1-7
timeToLive
INFINITE
the time in seconds before a message is discarded if it
doesn't reach the destination
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
concurrentConsumers
1
the numbers of consumers that get messages from the
queue at the same time
initialBufferSize
128
the initial buffer size
128
if the initial buffer size is not enough big for containing
the received message it's incremented by
incrementBufferSize
incrementBufferSize
Using camel-msmq
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-parent</artifactId>
<version>1.3.4.0-fuse</version>
</dependency>
And ensure you are pointing at the maven repo
<repository>
<id>open.iona.m2</id>
<name>IONA Open Source Community Release Repository</name>
<url>http://repo.open.iona.com/maven2</url>
<snapshots>
<enabled>false</enabled>
</snapshots>
<releases>
<enabled>true</enabled>
</releases>
</repository>
Building From Source
The source for camel-msmq is available here: https://projects.open.iona.com/projects/svn/iona/
camel/trunk/components/camel-msmq/
You'll need to register with http://open.iona.com to be able to access subversion.
The full FUSE distro is here: https://projects.open.iona.com/projects/svn/iona/camel/trunk/
See Also
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
CH APT ER 10 - CO M PO N EN T APPEN DIX
396
MSV COMPONENT
The MSV component performs XML validation of the message body using the MSV Library using
any of the XML schema languages supported such as XML Schema or RelaxNG XML Syntax.
Note that the Jing component also supports RelaxNG Compact Syntax
URI format
msv:someLocalOrRemoteResource
Where someLocalOrRemoteResource is some URL to a local resource on the classpath
or a full URL to a remote resource or resource on the file system. For example
• msv:org/foo/bar.rng
• msv:file:../foo/bar.rng
• msv:http://acme.com/cheese.rng
Example
The following example shows how to configure a route from endpoint direct:start which
then goes to one of two endpoints, either mock:valid or mock:invalid based on whether
or not the XML matches the given RelaxNG XML Schema (which is supplied on the classpath).
<camelContext xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="direct:start"/>
<doTry>
<to uri="msv:org/apache/camel/component/validator/msv/schema.rng"/>
<to uri="mock:valid"/>
<doCatch>
<exception>org.apache.camel.ValidationException</exception>
<to uri="mock:invalid"/>
</doCatch>
<doFinally>
<to uri="mock:finally"/>
</doFinally>
</doTry>
</route>
</camelContext>
See Also
•
•
•
•
397
Configuring Camel
Component
Endpoint
Getting Started
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
POJO COMPONENT
The pojo: component is now just an alias for the Bean component.
Has been removed in Camel 2.0.
See Also
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
QUARTZ COMPONENT
The quartz: component provides a scheduled delivery of messages using the Quartz
scheduler.
Each endpoint represents a different timer (in Quartz terms, a Trigger and JobDetail).
URI format
quartz://timerName?parameters
quartz://groupName/timerName?parameters
quartz://groupName/timerName/cronExpression
quartz://groupName/timerName/?cron=expression
quartz://timerName?cron=expression
(@deprecated)
(Camel 2.0)
(Camel 2.0)
Camel will either use a SimpleTrigger or a CronTrigger. If no cron expression is given
it will use a simple trigger.
If no groupName is provided Camel will use Camel as group name.
You can configure the Trigger and JobDetail using the parameters (if not using cron
expression)
Parameter
Default
Description
trigger.repeatCount
0
SimpleTrigger: How many times should the timer repeat
for?
trigger.repeatInterval
0
SimpleTrigger: The amount of time in milliseconds
between repeated triggers
job.name
null
Sets the name of the job
job.XXX
null
Sets the job option with the XXX setter name
trigger.XXX
null
Sets the trigger option with the XXX setter name
stateful
false
Uses a Quartz StatefulJob instead of the default Job
CH APT ER 10 - CO M PO N EN T APPEN DIX
398
Using cron expressions
Configuring the cron expression in Camel 1.x is based on path separators. We changed this
to an URI parameter in Camel 2.0 allowing a much nicer configuraiton.
Also its not possible to use the / cron special character (for increaments) in Camel 1.x,
which Camel 2.0 also fixes.
For example the following routing rule will fire 2 timer events to the endpoint mock:results
from("quartz://myGroup/
myTimerName?trigger.repeatInterval=2&trigger.repeatCount=1").to("mock:result");
When using a StatefulJob the JobDataMap is re-persisted after every execution of the job, thus
preserving state for the next execution.
Message Headers
Camel adds the getters from Quartz Execution Context as header values. These headers is
added:
calendar, fireTime, jobDetail, jobInstance, jobRuntTime,
mergedJobDataMap, nextFireTime, previousFireTime, refireCount,
result, scheduledFireTime, scheduler, trigger, triggerName,
triggerGroup.
The fireTime header contains the java.util.Date for when the exchange was fired.
Using Cron Triggers
Avaiable as of Camel 2.0
Quartz supports Cron-like expressions for specifying timers in a handy format. You can use
these expressions in the cron URI parameter; though to preserve valid URI encoding we allow
+ to be used instead of spaces. Quartz provides a little tutorial on how to use cron
expressions.
For example the following will fire a message at 12pm (noon) every day
from("quartz://myGroup/myTimerName?cron=0+0/
5+12-18+?+*+MON-FRI").to("activemq:Totally.Rocks");
which is equivalent to using the cron expression
0 0/5 12-18 ? * MON-FRI
The following table shows the URI character encodings we use to preserve valid URI syntax
399
URI Character
Cron character
'+'
''
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
Using Cron Triggers in Camel 1.x
@deprecated
Quartz supports Cron-like expressions for specifying timers in a handy format. You can use
these expressions in the URI; though to preserve valid URI encoding we allow / to be used
instead of spaces and $ to be used instead of ?.
For example the following will fire a message at 12pm (noon) every day
from("quartz://myGroup/myTimerName/0/0/12/*/*/$").to("activemq:Totally.Rocks");
which is equivalent to using the cron expression
0 0 12 * * ?
The following table shows the URI character encodings we use to preserve valid URI syntax
URI Character
Cron character
'/'
''
'$'
'?'
See Also
•
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
Timer
QUEUE COMPONENT
The queue: component provides asynchronous SEDA behaviour so that messages are
exchanged on a BlockingQueue and consumers are invoked in a seperate thread pool to the
producer.
Note that queues are only visible within a single CamelContext. If you want to communicate
across CamelContext instances such as to communicate across web applications, see the VM
component.
Note also that this component has nothing to do with JMS, if you want a distributed SEA
then try using either JMS or ActiveMQ or even MINA
URI format
queue:someName
Where someName can be any string to uniquely identify the endpoint within the current
CamelContext
CH APT ER 10 - CO M PO N EN T APPEN DIX
400
Deprecated
To avoid confusion with JMS queues, this component is now deprecated in 1.1 onwards.
Please use the SEDA component instead
See Also
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
REF COMPONENT
The ref: component is used for lookup of existing endpoints bound in the Registry.
URI format
ref:someName
Where someName can be any string which is used to lookup the endpoint in the Registry.
Runtime lookup
This component can be used when you need dynamic discovery of endpoints in the Registry
where you can compute the URI at runtime. Then you can lookup the endpoint using:
// lookup the endpoint
String myEndpointRef = "bigspenderOrder";
Endpoint endpoint = context.getEndpoint("ref:" + myEndpointRef);
Producer producer = endpoint.createProducer();
Exchange exchange = producer.createExchange();
exchange.getIn().setBody(payloadToSend);
// send the exchange
producer.process(exchange);
...
And you could have a list of endpoints defined in the Registry such as:
<camelContext id="camel" xmlns="http://activemq.apache.org/camel/schema/spring">
<endpoint id="normalOrder" uri="activemq:order.slow"/>
<endpoint id="bigspenderOrder" uri="activemq:order.high"/>
401
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
Sample
In the sample below we use the ref: in the URI to reference the endpoint with the spring id
endpoint2:
<bean id="mybean" class="org.apache.camel.spring.example.DummyBean">
<property name="endpoint" ref="endpoint1"/>
</bean>
<camelContext id="camel" xmlns="http://camel.apache.org/schema/spring">
<endpoint id="endpoint1" uri="direct:start"/>
<endpoint id="endpoint2" uri="mock:end"/>
<route>
<from ref="endpoint1"/>
<to uri="ref:endpoint2"/>
</route>
</camelContext>
You could of course have used the ref attribute instead:
<to ref="endpoint2"/>
That is more commonly used.
See Also
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
RMI COMPONENT
The rmi: component bind the PojoExchanges to the RMI protocol (JRMP).
Since this binding is just using RMI, normal RMI rules still apply in regards to what the
methods can be used over it. This component only supports PojoExchanges that carry a
method invocation that is part of an interface that extends the Remote interface. All parameters
in the method should be either Serializable or Remote objects too.
URI format
rmi://rmi-regisitry-host:rmi-registry-port/registry-path
For example:
rmi://localhost:1099/path/to/service
CH APT ER 10 - CO M PO N EN T APPEN DIX
402
Using
To call out to an existing RMI service registered in an RMI registry, create a Route similar to:
from("pojo:foo").to("rmi://localhost:1099/foo");
To bind an existing camel processor or service in an RMI registry, create a Route like:
RmiEndpoint endpoint= (RmiEndpoint) endpoint("rmi://localhost:1099/bar");
endpoint.setRemoteInterfaces(ISay.class);
from(endpoint).to("pojo:bar");
Notice that when binding an inbound RMI endpoint, the Remote interfaces exposed must be
specified.
Options
Name
Default
Value
Description
method
null
As of 1.3 or later you can set the name of the method to
invoke
See Also
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
RSS COMPONENT
The rss: component is used for polling RSS feeds. Camel will default poll the feed every 60th
seconds.
Note: The component currently only supports polling (consuming) feeds.
New in Camel 2.0
URI format
rss:rssUri
Where rssUri is the URI to the RSS feed to poll.
Options
Property
403
Default
Description
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
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.
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.
feedHeader
true
Sets whether to add the ROME SyndFeed 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
true to use fixed delay between pools, otherwise
fixed rate is used. See ScheduledExecutorService in
JDK for details.
splitEntries
filter
Exchange data types
Camel will set the in body on the returned Exchange with a ROME SyndFeed. Depending on
the splitEntries flag Camel will either return a SyndFeed with one SyndEntry or a List of
SyndEntrys.
Option
Value
Behavior
splitEntries
true
Only a single entry from the currently being processed feed is set in
the new exchange feed.
CH APT ER 10 - CO M PO N EN T APPEN DIX
404
splitEntries
false
The entires list of entries from the feed is set in the new exchange
feed.
Message Headers
Header
Description
org.apache.camel.component.rss.feed
Camel 1.x: The entire SyncFeed
object.
CamelRssFeed
Camel 2.0: The entire SyncFeed
object.
RSS Dataformat
The RSS component ships with an RSS dataformat that can be used to convert between String
(as XML) and ROME RSS model objects.
• marshal = from ROME SyndFeed to XML String
• unmarshal = from XML String to ROME SyndFeed
A route using this would look something like this:
from("rss:file:src/test/data/
rss20.xml?splitEntries=false&consumer.delay=1000").marshal().rss().to("mock:marshal");
The idea is to be able to use Camel's lovely built in expressions for manipulating RSS messages.
As shown below, an XPath expression can be used to filter the RSS message:
// only entries with Camel in the title will get through the filter
from("rss:file:src/test/data/rss20.xml?splitEntries=true&consumer.delay=100")
.marshal().rss().filter().xpath("//item/
title[contains(.,'Camel')]").to("mock:result");
Merging multiple incoming feeds
To merge multiple incoming feeds into a single feed, you can utilize a custom
AggregationCollection provided with camel-rss. An example usage would look something like
this:
from("rss:file:src/test/data/
rss20.xml?sortEntries=true&consumer.delay=50").to("seda:temp");
from("rss:file:target/rss20.xml?sortEntries=true&consumer.delay=50").to("seda:temp");
from("seda:temp").aggregate(new
AggregateRssFeedCollection()).batchTimeout(5000L).to("mock:result");
Here we use a Seda queue to gather up entries from two RSS feeds. The entries are then fed
into a custom aggregator which combines these entries into a single ROME SyndFeed object.
405
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
Filtering entries
You can filter out entries quite easily by using XPath as shown in the data format section above.
You can also utilize Camel's Bean Integration to implement your own conditions. For instance, a
filter equivalent to the XPath example above would be:
// only entries with Camel in the title will get through the filter
from("rss:file:src/test/data/rss20.xml?splitEntries=true&consumer.delay=100").
filter().method("myFilterBean", "titleContainsCamel").to("mock:result");
The custom bean for this would be
public static class FilterBean {
public boolean titleContainsCamel(@Body SyndFeed feed) {
SyndEntry firstEntry = (SyndEntry) feed.getEntries().get(0);
return firstEntry.getTitle().contains("Camel");
}
}
See Also
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
SEDA COMPONENT
The seda: component provides asynchronous SEDA behavior so that messages are exchanged
on a BlockingQueue and consumers are invoked in a separate thread to the producer.
Note that queues are only visible within a single CamelContext. If you want to communicate
across CamelContext instances such as to communicate across web applications, see the VM
component.
This component does not implement any kind of persistence or recovery if the VM
terminates while messages are yet to be processed. If you need persistence, reliability or
distributed SEDA then try using either JMS or ActiveMQ.
URI format
seda:someName
Where someName can be any string to uniquely identify the endpoint within the current
CamelContext
CH APT ER 10 - CO M PO N EN T APPEN DIX
406
Synchronous
The Direct component provides synchronous invocation of any consumers when a
producer sends a message exchange.
Options
Name
Default
Description
size
1000
The maximum size of the SEDA queue
concurrentConsumers
1
Camel 1.6.1/2.0: Number of concurrent threads
processing exchanges.
Concurrent consumers
By default Camel uses a single consumer. You can configure the endpoint to use concurrent
consumers. So instead of thread pools you can use:
from("seda:stageName?concurrentConsumers=5").process(...)
Difference between thread pools and concurrent consumers
The thread pool is a pool that dynamically can increase/shrink at runtime depending on load,
the concurrent consumers is always fixed.
Thread pools
Be aware that adding a thread pool to a seda endpoint by doing something like:
from("seda:stageName").thread(5).process(...)
can wind up with two BlockQueues. One from seda endpoint and one from the workqueue of
the thread pool which may not be what you want. Instead, you might want to consider
configuring a Direct endpoint with a thread pool which can process messages both
synchronously and asynchronously. For example:
from("direct:stageName").thread(5).process(...)
You can also directly configure number of threads that process messages on seda endpoint
using concurrentConsumers parameter.
407
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
Sample
In the route below we use the SEDA queue to send the request to this async queue to be able
to send a fire-and-forget message for further processing in another thread, and return a
constant reply in this thread to the original caller.
public void configure() throws Exception {
from("direct:start")
// send it to the seda queue that is async
.to("seda:next")
// return a constant response
.transform(constant("OK"));
from("seda:next").to("mock:result");
}
Here we send a Hello World message and expects the reply to be OK.
Object out = template.requestBody("direct:start", "Hello World");
assertEquals("OK", out);
The "Hello World" message will be consumed from the SEDA queue from another thread for
further processing, since this is from an unit test it will be sent to a mock endpoint where we
can do assertions in the unit test.
See Also
•
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
Direct
SMOOKS
The Smooks component supports the Smooks Library for EDI parsing. The camel-smooks
library is provided by the Camel Extra project which hosts all *GPL related components for
Camel.
It is only the EDI parsing feature that is implemented in this component. The other features
from Smooks is covered in existing camel components.
Parsing from a any given data source to EDI is implemented using Camel Data Format.
EDI DATAFORMAT
This component ships with a EDI dataformat that can be used to format from a
java.io.InputStream to XML as a org.w3c.Document Object.
• marshal = currently not supported by Smooks
CH APT ER 10 - CO M PO N EN T APPEN DIX
408
• unmarshal = from stream to XML (can be used when reading EDI files)
The EDIDataFormat must be configued with either a:
• setSmooksConfig(configfile) = a fully Smooks configuration file
• setMappingModel(modelfile) = just the mapping model xml file and Camel
will use a default Smooks configuration
To use the data format simply instantiate an instance, set the configuration (above) and invoke
the unmarshal operation in the route builder:
DataFormat edi = new EDIDataFormat();
edi.setMappingModel("my-order-mapping.xml");
...
from("file://edi/in").
unmarshal(edi).
to("jms:queue:edi");
And you can also provide the full Smooks configuration file where you can configure Smooks as
you want, in case the default configuration isn't useful:
DataFormat edi = new EDIDataFormat();
edi.setSmooksConfig("my-smooks-config.xml");
...
from("file://edi/in").
unmarshal(edi).
to("jms:queue:edi");
Dependencies
To use EDI in your camel routes you need to add the a dependency on camel-smooks
which implements this data format.
This component is hosted at the Camel Extra project since the Smooks library uses a
licenses which cant be included directly in an Apache project.
SPRING INTEGRATION COMPONENT
The spring-integration: component provides a bridge for Camel components to talk to
spring integration endpoints.
URI format
spring-integration:defaultChannelName[?options]
Where defaultChannelName represents the default channel name which is used by the
Spring Integration Spring context. It will equal to the inputChannel name for the Spring
Integration consumer and the outputChannel name for the Spring Integration provider.
409
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
Options
Name
Description
Example
Required
inputChannel
The spring integration
input channel name this
endpoint wants to
consume from that is
defined in the spring
context
inputChannel=requestChannel
No
outputChannel
The spring integration
output channel name to
send message to the
spring integration context
outputChannel=replyChannel
No
def
val
inOut
The exchange pattern
that spring integration
endpoint should use
inOut=true
No
inO
the
inte
con
and
out
for
spri
inte
pro
consumer.delay
Delay in millis between
each poll
consumer.delay=60000
No
500
consumer.initialDelay
Millis before polling starts
consumer.initialDelay=10000
No
100
consumer.userFixedDelay
true to use fixed delay
between pools, otherwise
fixed rate is used. See
ScheduledExecutorService
in JDK for details.
consumer.userFixedDelay=false
No
false
Usage
Spring Integration component is a bridge which connects Spring Integration endpoints through
the Spring integration's input and output channels with the Camel endpoints. In this way, we can
send out the Camel message to Spring Integration endpoints or receive the message from
Spring Integration endpoint in Camel routing context.
CH APT ER 10 - CO M PO N EN T APPEN DIX
410
Examples
Using the Spring Integration Endpoint
You could setup the Spring Integration Endpoint by using the URI
<beans:beans xmlns="http://www.springframework.org/schema/integration"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:beans="http://www.springframework.org/schema/beans"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/
spring-beans-2.5.xsd
http://www.springframework.org/schema/integration
http://www.springframework.org/schema/integration/
spring-integration-1.0.xsd
http://camel.apache.org/schema/spring
http://camel.apache.org/schema/spring/camel-spring.xsd">
<channel id="inputChannel"/>
<channel id="outputChannel"/>
<channel id="onewayChannel"/>
<service-activator input-channel="inputChannel"
ref="helloService"
method="sayHello"/>
<service-activator input-channel="onewayChannel"
ref="helloService"
method="greet"/>
<beans:bean id="helloService"
class="org.apache.camel.component.spring.integration.HelloWorldService"/>
<camelContext id="camel" xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="direct:twowayMessage"/>
<!-- Using the &amp; as the separator of & -->
<to
uri="spring-integration:inputChannel?inOut=true&amp;inputChannel=outputChannel"/>
</route>
<route>
<from uri="direct:onewayMessage"/>
<to uri="spring-integration:onewayChannel?inOut=false"/>
</route>
</camelContext>
<channel id="requestChannel"/>
<channel id="responseChannel"/>
<beans:bean id="myProcessor"
class="org.apache.camel.component.spring.integration.MyProcessor"/>
<camelContext id="camel" xmlns="http://camel.apache.org/schema/spring">
<route>
411
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
<!-- Using the &amp; as the separator of & -->
<from
uri="spring-integration://requestChannel?outputChannel=responseChannel&amp;inOut=true"/>
<process ref="myProcessor"/>
</route>
</camelContext>
or by the Spring Integration Channel name
<beans:beans xmlns="http://www.springframework.org/schema/integration"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:beans="http://www.springframework.org/schema/beans"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/
spring-beans-2.5.xsd
http://www.springframework.org/schema/integration
http://www.springframework.org/schema/integration/
spring-integration-1.0.xsd
http://camel.apache.org/schema/spring
http://camel.apache.org/schema/spring/camel-spring.xsd">
<channel id="outputChannel"/>
<camelContext id="camel" xmlns="http://camel.apache.org/schema/spring">
<route>
<!-- camel will create a spring integration endpoint automatically -->
<from uri="outputChannel"/>
<to uri="mock:result"/>
</route>
</camelContext>
The Source and Target adapter
Spring Integartion also provides the Spring Integration's Source and Target adapters which
could route the message from the Spring Integration channel to a camel context endpoint or
from a camel context endpoint to a Spring Integration Channel.
Here is the name spaces header
<beans:beans xmlns="http://www.springframework.org/schema/integration"
xmlns:beans="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:camel-si="http://camel.apache.org/schema/spring/integration"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
http://www.springframework.org/schema/integration
http://www.springframework.org/schema/integration/spring-integration-1.0.xsd
http://camel.apache.org/schema/spring/integration
http://camel.apache.org/schema/spring/integration/camel-spring-integration.xsd
http://camel.apache.org/schema/spring
http://camel.apache.org/schema/spring/camel-spring.xsd
">
Now you could bind your source or target to camel context endpoint
CH APT ER 10 - CO M PO N EN T APPEN DIX
412
<!-- Create the camel context here -->
<camelContext id="camelTargetContext" xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="direct:EndpointA" />
<to uri="mock:result" />
</route>
<route>
<from uri="direct:EndpointC"/>
<process ref="myProcessor"/>
</route>
</camelContext>
<!-- We can bind the camelTarget to the camel context's endpoint by specifying the
camelEndpointUri attribute -->
<camel-si:camelTarget id="camelTargetA" camelEndpointUri="direct:EndpointA"
expectReply="false">
<camel-si:camelContextRef>camelTargetContext</camel-si:camelContextRef>
</camel-si:camelTarget>
<camel-si:camelTarget id="camelTargetB" camelEndpointUri="direct:EndpointC"
replyChannel="channelC" expectReply="true">
<camel-si:camelContextRef>camelTargetContext</camel-si:camelContextRef>
</camel-si:camelTarget>
<camel-si:camelTarget id="camelTargetD" camelEndpointUri="direct:EndpointC"
expectReply="true">
<camel-si:camelContextRef>camelTargetContext</camel-si:camelContextRef>
</camel-si:camelTarget>
<beans:bean id="myProcessor"
class="org.apache.camel.component.spring.integration.MyProcessor"/>
<camelContext id="camelSourceContext" xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="direct:OneWay"/>
<to uri="direct:EndpointB" />
</route>
<route>
<from uri="direct:TwoWay"/>
<to uri="direct:EndpointC" />
</route>
</camelContext>
<!-- camelSource will redirect the message coming for direct:EndpointB to the spring
requestChannel channelA -->
<camel-si:camelSource id="camelSourceA" camelEndpointUri="direct:EndpointB"
requestChannel="channelA" expectReply="false">
<camel-si:camelContextRef>camelSourceContext</camel-si:camelContextRef>
</camel-si:camelSource>
<!-- camelSource will redirect the message coming for direct:EndpointC to the spring
requestChannel channelB
then it will pull the response from channelC and put the response message back to
direct:EndpointC -->
413
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
<camel-si:camelSource id="camelSourceB" camelEndpointUri="direct:EndpointC"
requestChannel="channelB" replyChannel="channelC" expectReply="true">
<camel-si:camelContextRef>camelSourceContext</camel-si:camelContextRef>
</camel-si:camelSource>
See Also
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
STREAM COMPONENT
The stream: component provides access to the System.in, System.out and System.err streams
together with allowing streaming of file and url.
URI format
stream:in
stream:out
stream:err
stream:header
And the file and url is supported in Camel 2.0:
stream:file?fileName=/foo/bar.txt
stream:url
If the stream:header option is specified then the stream header is used to find the stream
to write to. This option is only available for StreamProducer.
Options
Name
Default
Value
Description
delay
0
Initial delay in millis before consuming or producing the
stream.
encoding
JVM
Default
As of 1.4 or later you can configure the encoding (is a
charset name) to use text based streams (eg. message
body is a String object). If not provided Camel will use
the JVM default Charset.
CH APT ER 10 - CO M PO N EN T APPEN DIX
414
null
Camel 2.0: Leading prompt message that can be used
when reading from stream:in to have a leading text such
as Enter a command:
promptMessageDelay
0
Camel 2.0: Optional delay in millis before showing the
prompt message. Can be used when system startup to
avoid prompt message being written while other logging
is done to the System out.
promptDelay
0
Camel 2.0: Optional delay in millis before showing the
prompt message.
promptInitialDelay
2000
Camel 2.0: initial delay in millis before showing the
prompt message. This delay only occurs once. Can be
used when system startup to avoid prompt message
being written while other logging is done to the System
out.
fileName
null
Camel 2.0: When using the stream:file notation
this specifies the file name to stream to/from.
scanStream
false
Camel 2.0: To be used for continuously reading a
stream such as the unit tail command.
scanStreamDelay
0
Camel 2.0: Delay in millis between read attempts
when using scanStream.
promptMessage
Message content
The stream: component supports either String or byte[] for writing to streams. Just add to
the message.in.body either a Stirng or byte[] content.
The special stream:header URI is used for custom output streams. Just add a
java.io.OutputStream to message.in.header in the key header.
See samples for an example.
Samples
In this sample we output to System.out the content from the message when its put on the
direct:in queue.
public void testStringContent() throws Exception {
template.sendBody("direct:in", "Hello Text World\n");
}
public void testBinaryContent() {
template.sendBody("direct:in", "Hello Bytes World\n".getBytes());
}
415
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
protected RouteBuilder createRouteBuilder() {
return new RouteBuilder() {
public void configure() {
from("direct:in").to("stream:out");
}
};
}
This sample demonstrates how the header type can be used to determine which stream to use.
In the sample we use our own output stream (MyOutputStream).
private OutputStream mystream = new MyOutputStream();
private StringBuffer sb = new StringBuffer();
public void testStringContent() {
template.sendBody("direct:in", "Hello");
// StreamProducer appends \n in text mode
assertEquals("Hello\n", sb.toString());
}
public void testBinaryContent() {
template.sendBody("direct:in", "Hello".getBytes());
// StreamProducer is in binary mode so no \n is appended
assertEquals("Hello", sb.toString());
}
protected RouteBuilder createRouteBuilder() {
return new RouteBuilder() {
public void configure() {
from("direct:in").setHeader("stream", constant(mystream)).
to("stream:header");
}
};
}
private class MyOutputStream extends OutputStream {
public void write(int b) throws IOException {
sb.append((char)b);
}
}
This sample demonstrates how to continously read a file stream such as the Unix tail command:
from("stream:file?fileName=/server/logs/
server.log?scanStream=true&scanStreamDelay=1000").to("bean:logService?method=parseLogLine");
See Also
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
CH APT ER 10 - CO M PO N EN T APPEN DIX
416
STRING TEMPLATE
The string-template: component allows you to process a message using a String Template.
This can be ideal when using Templating to generate responses for requests.
URI format
string-template:templateName
Where templateName is the classpath-local URI of the template to invoke; or the complete
URL of the remote template.
Options
Option
Default
Description
contentCache
false
New option in Camel 1.4. Cache for the resource content
when its loaded.
Headers
Camel will store a reference to the resource in the message header in the key
org.apache.camel.stringtemplate.resource. The Resource is an
org.springframework.core.io.Resource object.
Hot reloading
The stringtemplate resource is by default hot reloadable for both file and classpath resources
(expanded jar). Setting the contentCache=true then Camel will only load the resource once,
and thus hot reloading is not possible. This scenario can be used in production usage when the
resource never changes.
StringTemplate Attributes
Camel will provide exchange information as attributes (just a Map) to the string template. The
Exchange is transfered as:
417
key
value
exchange
The Exchange itself
headers
The headers of the in message
camelContext
The Camel Context
request
The in message
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
in
The in message
body
The in message body
out
The out message (only for InOut message exchange pattern)
response
The out message (only for InOut message exchange pattern)
Samples
For example you could use something like
from("activemq:My.Queue").
to("string-template:com/acme/MyResponse.tm");
To use a string template to formulate a response for a message
The Email Sample
In this sample we want to use StringTemplate as templating for an order confirmation email.
The email template is laid out in StringTemplate 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;
}
public void testVelocityLetter() throws Exception {
MockEndpoint mock = getMockEndpoint("mock:result");
mock.expectedMessageCount(1);
mock.expectedBodiesReceived("Dear Ibsen, Claus! Thanks for the order of Camel in
Action. Regards Camel Riders Bookstore PS: Next beer is on me, James");
template.send("direct:a", createLetter());
mock.assertIsSatisfied();
}
protected RouteBuilder createRouteBuilder() throws Exception {
CH APT ER 10 - CO M PO N EN T APPEN DIX
418
return new RouteBuilder() {
public void configure() throws Exception {
from("direct:a").to("string-template:org/apache/camel/component/
stringtemplate/letter.tm").to("mock:result");
}
};
}
See Also
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
TEST 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 Test component extends the Mock component to support pulling messages from another
endpoint on startup to set the expected message bodies on the underlying Mock endpoint.
i.e. you use the test endpoint in a route and messages arriving on it will be implicitly
compared to some expected messages extracted from some other location.
So you can use for example an expected set of message bodies as files. This will then setup a
properly configured Mock endpoint which is only valid if the received messages match the
number of expected messages and their message payloads are equal.
URI format
test:expectedMessagesEndpointUri
Where expectedMessagesEndpointUri refers to some other Component URI where
the expected message bodies are pulled from before starting the test.
Example
For example you could write a test case as follows
from("seda:someEndpoint").
to("test:file://data/expectedOutput?noop=true");
If your test then invokes the MockEndpoint.assertIsSatisfied(camelContext) method then your
test case will perform the necessary assertions.
419
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
Here is a real example test case using Mock and Spring along with its Spring XML.
To see how you can set other expectations on the test endpoint, see the Mock component.
See Also
•
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
Spring Testing
TIMER COMPONENT
The timer: component is used to generate message exchanges when a timer fires You can
only consume events from this endpoint.
URI format
timer:name?options
Where name of the Timer object which is created and shared across endpoints. So if you use
the same name for all your timer endpoints then only one Timer object & thread will be used.
Notice: The IN body of the generated exchange is null. So
exchange.getIn().getBody() returns null.
Options
Where options is a query string that can specify any of the following parameters:
Name
Default
Value
Description
time
null
A java.util.Date the first event should be generated
period
1000
If greater than 0, then generate periodic events every period
milliseconds
delay
0
The number of milliseconds to wait before the first event is
generated. Should not be used in conjunction with the time
parameter.
fixedRate
false
Events take place at approximately regular intervals, separated by
the specified period
daemon
true
Should the thread associated with the timer endpoint be run as a
daemon
CH APT ER 10 - CO M PO N EN T APPEN DIX
420
Advanced Scheduler
See also the Quartz component that supports much more advanced scheduling.
Exchange Properties
When the timer is fired it adds the following information as properties to the Exchange.
Name
Type
Description
org.apache.camel.timer.name
String
the name option
org.apache.camel.timer.time
Date
the time option
org.apache.camel.timer.period
long
the period option
org.apache.camel.timer.firedTime
Date
Camel 1.5: the current time when the
consumer fired
Message Headers
When the timer is fired it adds the following information as headers to the IN message
Name
Type
Description
firedTime
Date
Camel 1.5: the current time when the consumer fired
Sample
To setup a route that generates an event every 60 seconds:
from("timer://foo?fixedRate=true&period=60000").to("bean:myBean?method=someMethodName");
The above route will generate an event then invoke the someMethodName on the bean called
myBean in the Registry such as JNDI or Spring.
And the route in Spring DSL:
<route>
<from uri="timer://foo?fixedRate=true&amp;period=60000"/>
<to uri="bean:myBean?method=someMethodName"/>
</route>
See Also
•
•
•
•
421
Configuring Camel
Component
Endpoint
Getting Started
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
• Quartz
VALIDATION COMPONENT
The Validation component performs XML validation of the message body using the JAXP
Validation API using any of the supported XML schema languages, which defaults to XML
Schema
Note that the Jing component also supports the following schema languages which are useful
• RelaxNG Compact Syntax
• RelaxNG XML Syntax
The MSV component also supports RelaxNG XML Syntax.
URI format
validator:someLocalOrRemoteResource
Where someLocalOrRemoteResource is some URL to a local resource on the classpath
or a full URL to a remote resource or resource on the file system which contains the XSD to
validate against. For example
• msv:org/foo/bar.xsd
• msv:file:../foo/bar.xsd
• msv:http://acme.com/cheese.xsd
• validator:com/mypackage/myschema.xsd
Example
The following example shows how to configure a route from endpoint direct:start which
then goes to one of two endpoints, either mock:valid or mock:invalid based on whether
or not the XML matches the given schema (which is supplied on the classpath).
<camelContext xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="direct:start"/>
<doTry>
<to uri="validator:org/apache/camel/component/validator/schema.xsd"/>
<to uri="mock:valid"/>
<doCatch>
<exception>org.apache.camel.ValidationException</exception>
<to uri="mock:invalid"/>
</doCatch>
<doFinally>
<to uri="mock:finally"/>
</doFinally>
</doTry>
</route>
</camelContext>
CH APT ER 10 - CO M PO N EN T APPEN DIX
422
See Also
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
VELOCITY
The velocity: component allows you to process a message using an Apache Velocity template.
This can be ideal when using Templating to generate responses for requests.
URI format
velocity:templateName
Where templateName is the classpath-local URI of the template to invoke; or the complete
URL of the remote template (eg: file://folder/myfile.vm).
Options
Option
Default
Description
loaderCache
true
Velocity based file loader cache
New option in Camel 1.4. Cache for the resource content
when its loaded. Is default false in Camel 1.x. Is default true in
Camel 2.x.
contentCache
encoding
null
New option in Camel 1.6. Character encoding of the resource
content.
Message Headers
423
Header
Description
org.apache.camel.velocity.resource
Camel 1.x: The resource as an
org.springframework.core.io.Resource
object.
org.apache.camel.velocity.resourceUri
Camel 1.x: The templateName as String object.
CamelVelocityResource
Camel 2.0: The resource as an
org.springframework.core.io.Resource
object.
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
CamelVelocityRsourceUri
Camel 2.0: The templateName as String object.
In Camel 1.4 headers set during the velocity evaluation is returned to the message and added as
headers. Then its kinda possible to return values from Velocity to the Message.
An example: Set the header value of fruit in the Velocity template .tm:
$in.setHeader('fruit', 'Apple')
The header 'fruit' is now accessible from the message.out.headers.
Velocity Context
Camel will provide exchange information in the Velocity context (just a Map). The Exchange is
transfered as:
key
value
exchange
The Exchange itself
headers
The headers of the in message
camelContext
The Camel Context
request
The in message
in
The in message
body
The in message body
out
The out message (only for InOut message exchange pattern)
response
The out message (only for InOut message exchange pattern)
Hot reloading
The velocity template resource is by default hot reloadable for both file and classpath resources
(expanded jar). Setting the contentCache=true then Camel will only load the resource once,
and thus hot reloading is not possible. This scenario can be used in production usage when the
resource never changes.
Samples
For example you could use something like
from("activemq:My.Queue").
to("velocity:com/acme/MyResponse.vm");
To use a velocity template to formulate a response for a message for InOut message exchanges
(where there is a JMSReplyTo header).
CH APT ER 10 - CO M PO N EN T APPEN DIX
424
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");
And to use content cache, eg. for production usage where the .vm template never changes:
from("activemq:My.Queue").
to("velocity:com/acme/MyResponse.vm?contentCache=true").
to("activemq:Another.Queue");
And a file based resource:
from("activemq:My.Queue").
to("velocity:file://myfolder/MyResponse.vm?contentCache=true").
to("activemq:Another.Queue");
The Email Sample
In this sample we want to use Velocity as templating for an order confirmation email. The email
template is laid out in Velocity 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;
}
public void testVelocityLetter() throws Exception {
MockEndpoint mock = getMockEndpoint("mock:result");
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 {
425
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
return new RouteBuilder() {
public void configure() throws Exception {
from("direct:a").to("velocity:org/apache/camel/component/velocity/
letter.vm").to("mock:result");
}
};
}
See Also
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
VM COMPONENT
The vm: component provides asynchronous SEDA behavior so that messages are exchanged
on a BlockingQueue and consumers are invoked in a separate thread pool to the producer.
This component differs from the Seda component in that VM supports communication
across CamelContext instances so you can use this mechanism to communicate across web
applications, provided that the camel-core.jar is on the system/boot classpath.
This component is an extension to the Seda component.
URI format
vm:someName
Where someName can be any string to uniquely identify the endpoint within the JVM (or at
least within the classloader which loaded the camel-core.jar)
Options
Name
Default
Description
size
1000
The maximum size of the SEDA queue
Samples
In the route below we send the exchange to the VM queue that is working across
CamelContext instances.
from("direct:in").bean(MyOrderBean.class).to("vm:order.email");
And then in another Camel context such as deployed as in another .war application:
CH APT ER 10 - CO M PO N EN T APPEN DIX
426
from("vm:order.email").bean(MyOrderEmailSender.class);
See Also
•
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
Seda
XMPP COMPONENT
The xmpp: component implements an XMPP (Jabber) transport.
URI format
xmpp://[login@]hostname[:port][/participant][?Options]
The component supports both room based and private person-person conversations.
The component supports both producer and consumer (you can get messages from xmpp or
send messages to xmpp). Consumer mode supports rooms starting from camel-1.5.0.
Options
427
Name
Description
room
If room is specified then component will connect to MUC (Multi User
Chat). Usually domain name for MUC is different from login domain. For
example if you are superman@jabber.org and want to join "krypton" room
then room url is krypton@conference.jabber.org. Note "conference" part.
Starting from camel-1.5.0 it is not required to provide full room JID. If
room parameter does not contain "@" symbol then domain part will be
discovered and added by Camel
user
User name (without server name). If not specified then anonymous login
attempt will be performed.
password
Password
resource
XMPP resource. The default is "Camel"
createAccount
If "true" then an attempt to create an account will be made. Default is
false
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
participant
JID (Jabber ID) of person to receive messages. "room" parameter has
precedence over "participant".
nickname
Use nick when joining room. If room is specified and nickname is not then
"user" will be used for nick
serviceName
Camel 1.6/2.0 The name of the service you are connecting to. For
Google Talk, this would be gmail.com
Examples
User "superman" to join room krypton at jabber server with password "secret".
xmpp://superman@jabber.org/?room=krypton@conference.jabber.org&password=secret
User "superman" to send messages to joker
xmpp://superman@jabber.org/joker@jabber.org?password=secret
Routing example in Java
from("timer://kickoff?period=10000").
setBody(constant("I will win!\n Your Superman.")).
to("xmpp://superman@jabber.org/joker@jabber.org?password=secret");
Consumer configuration. Will write all messages from Joker into a queue "evil.talk".
from("xmpp://superman@jabber.org/joker@jabber.org?password=secret").
to("activemq:evil.talk");
Consumer configuration listening to a room messages (supported from camel-1.5.0)
from("xmpp://superman@jabber.org/?password=secret&room=krypton@conference.jabber.org").
to("activemq:krypton.talk");
Room in short notation (no domain part; for camel-1.5.0+)
from("xmpp://superman@jabber.org/?password=secret&room=krypton").
to("activemq:krypton.talk");
When connecting to the Google Chat service, you'll need to specify the serviceName as well as
your credentials (as of Camel 1.6/2.0)
// send a message from fromuser@gmail.com to touser@gmail.com
from("direct:start").
to("xmpp://talk.google.com:5222/
touser@gmail.com?serviceName=gmail.com&user=fromuser&password=secret").
to("mock:result");
See Also
• Configuring Camel
• Component
CH APT ER 10 - CO M PO N EN T APPEN DIX
428
• Endpoint
• Getting Started
XQUERY
The xquery: component allows you to process a message using an XQuery template. This can
be ideal when using Templating to generate respopnses for requests.
URI format
xquery:templateName
Where templateName is the classpath-local URI of the template to invoke; or the complete
URL of the remote template.
For example you could use something like
from("activemq:My.Queue").
to("xquery:com/acme/mytransform.xquery");
To use a xquery template to forumulate 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("xquery:com/acme/mytransform.xquery").
to("activemq:Another.Queue");
Options
Name
Default Value
Description
See Also
•
•
•
•
Configuring Camel
Component
Endpoint
Getting Started
XSLT
The xslt: component allows you to process a message using an XSLT template. This can be
ideal when using Templating to generate respopnses for requests.
429
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X
URI format
xslt:templateName
Where templateName is the classpath-local URI of the template to invoke; or the complete
URL of the remote template. Refer to the Spring Documentation for more detail of the URI
syntax
Here are some example URIs
URI
Description
xslt:com/acme/mytransform.xsl
refers to the file com/acme/mytransform.xsl on the
classpath
xslt:file:///foo/bar.xsl
refers to the file /foo/bar.xsl
xslt:http://acme.com/cheese/
foo.xsl
refers to the remote http resource
Using XSLT endpoints
For example you could use something like
from("activemq:My.Queue").
to("xslt:com/acme/mytransform.xsl");
To use a xslt template to forumulate 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("xslt:com/acme/mytransform.xsl").
to("activemq:Another.Queue");
Getting Parameters into the XSLT to work with
By default, all headers are added as parameters which are available in the XSLT.
To do this you will need to declare the parameter so it is then 'useable'.
<setHeader headerName="myParam"><constant>42</constant></setHeader>
<to uri="xslt:MyTransform.xsl"/>
and the XSLT just needs to declare it at the top level for it to be available.
<xsl: ...... >
<xsl:param name="myParam"/>
<xsl:template ...>
CH APT ER 10 - CO M PO N EN T APPEN DIX
430
Spring XML versions
To use the above examples in Spring XML you would use something like
<camelContext xmlns="http://activemq.apache.org/camel/schema/spring">
<route>
<from uri="activemq:My.Queue"/>
<to uri="xslt:org/apache/camel/spring/processor/example.xsl"/>
<to uri="activemq:Another.Queue"/>
</route>
</camelContext>
There is a test case along with its Spring XML if you want a concrete example.
Options
Name
converter
transformerFactory
transformerFactoryClass
Default
Value
Description
null
Option to override default XmlConverter. Will
lookup for the converter in the Registry. The
provided converted must be of type
org.apache.camel.converter.jaxp.XmlConverter.
null
New added in Camel 1.6 Option to override
default TransformerFactory. Will lookup for the
transformerFactory in the Registry. The provided
transformer factory must be of type
javax.xml.transform.TransformerFactory.
null
New added in Camel 1.6 Option to override
default TransformerFactory. Will create a
TransformerFactoryClass instance and set it to the
coverter.
See Also
•
•
•
•
431
Configuring Camel
Component
Endpoint
Getting Started
CH A PTE R 1 0 - C OMP ONE NT A P P E ND I X