Oracle Database Java Developer`s Guide

Oracle Database Java Developer`s Guide
Oracle® Database
Java Developer’s Guide,
11g Release 1 (11.1)
B31225-02
September 2007
This book describes how to develop, load, and run Java
applications in Oracle Database.
Oracle Database Java Developer’s Guide, 11g Release 1 (11.1)
B31225-02
Copyright © 1999, 2007, Oracle. All rights reserved.
Primary Author:
Tulika Das, Sheryl Maring, Rick Sapir, Michael Wiesenberg
Contributing Author:
Venkatasubramaniam Iyer, Brian Wright, Timothy Smith
Contributor: Malik Kalfane, Kuassi Mensah, Mark Jungerman, Suresh Srinivasan, Ernest Tucker, Robert H
Lee, Dmitry Nizhegorodov, David Unietis, Steve Harris, Ellen Barnes, Peter Benson, Greg Colvin, Bill
Courington, Matthieu Devin, Jim Haungs, Hal Hildebrand, Susan Kraft, Thomas Kurian, Scott Meyer, Tom
Portfolio, Dave Rosenberg, Jerry Schwarz, Harlan Sexton, David Unietis, Xuhua Li
The Programs (which include both the software and documentation) contain proprietary information; they
are provided under a license agreement containing restrictions on use and disclosure and are also protected
by copyright, patent, and other intellectual and industrial property laws. Reverse engineering, disassembly,
or decompilation of the Programs, except to the extent required to obtain interoperability with other
independently created software or as specified by law, is prohibited.
The information contained in this document is subject to change without notice. If you find any problems in
the documentation, please report them to us in writing. This document is not warranted to be error-free.
Except as may be expressly permitted in your license agreement for these Programs, no part of these
Programs may be reproduced or transmitted in any form or by any means, electronic or mechanical, for any
purpose.
If the Programs are delivered to the United States Government or anyone licensing or using the Programs on
behalf of the United States Government, the following notice is applicable:
U.S. GOVERNMENT RIGHTS Programs, software, databases, and related documentation and technical data
delivered to U.S. Government customers are "commercial computer software" or "commercial technical data"
pursuant to the applicable Federal Acquisition Regulation and agency-specific supplemental regulations. As
such, use, duplication, disclosure, modification, and adaptation of the Programs, including documentation
and technical data, shall be subject to the licensing restrictions set forth in the applicable Oracle license
agreement, and, to the extent applicable, the additional rights set forth in FAR 52.227-19, Commercial
Computer Software--Restricted Rights (June 1987). Oracle USA, Inc., 500 Oracle Parkway, Redwood City, CA
94065.
The Programs are not intended for use in any nuclear, aviation, mass transit, medical, or other inherently
dangerous applications. It shall be the licensee's responsibility to take all appropriate fail-safe, backup,
redundancy and other measures to ensure the safe use of such applications if the Programs are used for such
purposes, and we disclaim liability for any damages caused by such use of the Programs.
Oracle, JD Edwards, PeopleSoft, and Siebel are registered trademarks of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective owners.
The Programs may provide links to Web sites and access to content, products, and services from third
parties. Oracle is not responsible for the availability of, or any content provided on, third-party Web sites.
You bear all risks associated with the use of such content. If you choose to purchase any products or services
from a third party, the relationship is directly between you and the third party. Oracle is not responsible for:
(a) the quality of third-party products or services; or (b) fulfilling any of the terms of the agreement with the
third party, including delivery of products or services and warranty obligations related to purchased
products or services. Oracle is not responsible for any loss or damage of any sort that you may incur from
dealing with any third party.
Contents
Preface ............................................................................................................................................................... xv
Audience.....................................................................................................................................................
Documentation Accessibility ...................................................................................................................
Related Documents ...................................................................................................................................
Conventions ...............................................................................................................................................
What’s New in 11g Release 1 (11.1)
xv
xv
xvi
xvi
........................................................................................ xvii
Oracle JVM Compatibility with JDK 1.5 ............................................................................................... xvii
Oracle JVM Utilities Enhancements ...................................................................................................... xvii
Ease-of-Use Interface .............................................................................................................................. xviii
Oracle JVM Just-in-Time Compiler (JIT)................................................................................................ xix
1
Introduction to Java in Oracle Database
Overview of Java ...................................................................................................................................... 1-1
Java and Object-Oriented Programming Terminology ................................................................ 1-1
Classes .......................................................................................................................................... 1-2
Objects .......................................................................................................................................... 1-2
Interfaces ...................................................................................................................................... 1-3
Encapsulation .............................................................................................................................. 1-3
Inheritance ................................................................................................................................... 1-4
Polymorphism ............................................................................................................................. 1-4
Key Features of the Java Language ................................................................................................. 1-5
JVM...................................................................................................................................................... 1-6
Java Class Hierarchy.......................................................................................................................... 1-7
Using Java in Oracle Database............................................................................................................... 1-8
Java and RDBMS: A Robust Combination ..................................................................................... 1-9
Multithreading................................................................................................................................. 1-10
Automated Storage Management With Garbage Collection .................................................... 1-10
Footprint ........................................................................................................................................... 1-12
Performance of Oracle JVM ........................................................................................................... 1-12
Dynamic Class Loading ................................................................................................................. 1-14
Overview of Oracle JVM ..................................................................................................................... 1-15
Process Area..................................................................................................................................... 1-16
The main() Method ......................................................................................................................... 1-16
The GUI ............................................................................................................................................ 1-16
iii
The IDE .............................................................................................................................................
Main Components of Oracle JVM .....................................................................................................
Library Manager..............................................................................................................................
Compiler...........................................................................................................................................
Interpreter.........................................................................................................................................
Class Loader.....................................................................................................................................
Verifier ..............................................................................................................................................
Server-Side JDBC Internal Driver .................................................................................................
Server-Side SQLJ Translator ..........................................................................................................
System Classes .................................................................................................................................
Java Application Strategy of Oracle ..................................................................................................
Java in Database Application Development ...............................................................................
Java Programming Environment ..................................................................................................
Java Stored Procedures...................................................................................................................
PL/SQL Integration and Oracle RDBMS Functionality ............................................................
JDBC Drivers ............................................................................................................................
SQLJ ...........................................................................................................................................
JPublisher ..................................................................................................................................
Development Tools .........................................................................................................................
Memory Model for Dedicated Mode Sessions................................................................................
2
1-16
1-16
1-18
1-18
1-18
1-18
1-18
1-18
1-19
1-19
1-19
1-20
1-20
1-20
1-20
1-21
1-21
1-22
1-22
1-22
Java Applications on Oracle Database
Database Sessions Imposed on Java Applications ............................................................................ 2-1
Execution Control of Java Applications............................................................................................... 2-3
Java Code, Binaries, and Resources Storage ....................................................................................... 2-3
Preparing Java Class Methods for Execution...................................................................................... 2-5
Compiling Java Classes ..................................................................................................................... 2-5
Compiling Source Through javac ............................................................................................. 2-6
Compiling Source Through loadjava ....................................................................................... 2-6
Compiling Source at Run Time................................................................................................. 2-6
Specifying Compiler Options.................................................................................................... 2-6
Recompiling Automatically....................................................................................................... 2-8
Resolving Class Dependencies......................................................................................................... 2-9
Loading Classes ............................................................................................................................... 2-12
Granting Execute Rights ................................................................................................................ 2-15
Controlling the Current User ........................................................................................................ 2-16
Checking Java Uploads .................................................................................................................. 2-18
Publishing......................................................................................................................................... 2-19
Auditing............................................................................................................................................ 2-20
User Interfaces on the Server .............................................................................................................. 2-21
Shortened Class Names........................................................................................................................ 2-22
Class.forName() in Oracle Database.................................................................................................. 2-22
Supply ClassLoader in Class.forName()...................................................................................... 2-23
Supply Class and Schema Names to classForNameAndSchema() .......................................... 2-24
Supply Class and Schema Names to lookupClass()................................................................... 2-25
Supply Class and Schema Names when Serializing .................................................................. 2-25
Class.forName Example................................................................................................................. 2-25
iv
Managing Your Operating System Resources.................................................................................
Overview of Operating System Resources ..................................................................................
Garbage Collection and Operating System Resources ..............................................................
Managing Your Applications Using JMX.........................................................................................
Enabling and Starting JMX in a Session.......................................................................................
OJVM JMX Defaults and Configurability....................................................................................
Examples of SQL calls to dbms_java.start_jmx_agent...............................................................
Important Security Notes...............................................................................................................
Threading in Oracle Database ............................................................................................................
Shared Servers Considerations...........................................................................................................
End-of-Call Migration ....................................................................................................................
Oracle-Specific Support for End-of-Call Optimization .............................................................
The EndOfCallRegistry.registerCallback() Method ...................................................................
The EndOfCallRegistry.runCallbacks() Method ........................................................................
The Callback Interface ....................................................................................................................
The Callback.act() method .............................................................................................................
Operating System Resources Affected Across Calls ..................................................................
3
2-26
2-27
2-27
2-28
2-29
2-30
2-31
2-31
2-32
2-34
2-35
2-36
2-38
2-38
2-39
2-39
2-39
Calling Java Methods in Oracle Database
Invoking Java Methods ........................................................................................................................... 3-1
Using PL/SQL Wrappers.................................................................................................................. 3-1
JNI Support ......................................................................................................................................... 3-3
Utilizing SQLJ and JDBC with Java in the Database..................................................................... 3-3
JDBC.............................................................................................................................................. 3-4
SQLJ .............................................................................................................................................. 3-4
Example Comparing JDBC and SQLJ ...................................................................................... 3-5
Complete SQLJ Example............................................................................................................ 3-6
SQLJ Strong Typing Paradigm.................................................................................................. 3-7
Translating a SQLJ Program...................................................................................................... 3-7
Running a SQLJ Program in the Server ................................................................................... 3-8
Converting a Client Application to Run on the Server ......................................................... 3-8
Interacting with PL/SQL ........................................................................................................... 3-8
Using Command-Line Interface....................................................................................................... 3-9
Using the Client-Side Stub ............................................................................................................. 3-10
Debugging Server Applications......................................................................................................... 3-13
How To Tell You Are Running on the Server ................................................................................. 3-14
Redirecting Output on the Server ...................................................................................................... 3-14
Calling Java in the Database Directly ............................................................................................... 3-20
4
Java Installation and Configuration
Initializing a Java-Enabled Database ...................................................................................................
Configuring with Oracle Database Template ................................................................................
Modifying an Existing Oracle Database to Include Oracle JVM.................................................
Configuring Oracle JVM.........................................................................................................................
Using The DBMS_JAVA Package.........................................................................................................
Enabling the Java Client .........................................................................................................................
4-1
4-1
4-1
4-2
4-2
4-2
v
Install J2SE on the Client ...................................................................................................................
Set Up Environment Variables.........................................................................................................
Test Install with Samples ..................................................................................................................
Two-Tier Duration for Java Session State...........................................................................................
Setting System Properties.......................................................................................................................
5
Developing Java Stored Procedures
Stored Procedures and Run-Time Contexts ........................................................................................
Functions and Procedures.................................................................................................................
Database Triggers...............................................................................................................................
Object-Relational Methods................................................................................................................
Advantages of Stored Procedures .........................................................................................................
Performance ........................................................................................................................................
Productivity and Ease of Use ...........................................................................................................
Scalability ............................................................................................................................................
Maintainability ...................................................................................................................................
Interoperability...................................................................................................................................
Replication...........................................................................................................................................
Security ................................................................................................................................................
Java Stored Procedures Steps.................................................................................................................
Step 1: Create or Reuse the Java Classes.........................................................................................
Step 2: Load and Resolve the Java Classes .....................................................................................
Step 3: Publish the Java Classes .......................................................................................................
Step 4: Call the Stored Procedures...................................................................................................
Step 5: Debug the Stored Procedures, if Necessary ......................................................................
6
4-2
4-2
4-3
4-4
4-4
5-1
5-2
5-2
5-2
5-3
5-3
5-3
5-4
5-4
5-4
5-4
5-4
5-5
5-5
5-6
5-6
5-6
5-7
Publishing Java Classes With Call Specifications
Understanding Call Specifications ....................................................................................................... 6-1
Defining Call Specifications .................................................................................................................. 6-2
Setting Parameter Modes .................................................................................................................. 6-3
Mapping Data Types ......................................................................................................................... 6-3
Using the Server-Side Internal JDBC Driver .................................................................................. 6-5
Writing Top-Level Call Specifications................................................................................................. 6-6
Writing Packaged Call Specifications ............................................................................................... 6-10
Writing Object Type Call Specifications.......................................................................................... 6-12
Declaring Attributes ....................................................................................................................... 6-13
Declaring Methods.......................................................................................................................... 6-13
Map and Order Methods ........................................................................................................ 6-14
Constructor Methods............................................................................................................... 6-14
Examples ................................................................................................................................... 6-15
7
Calling Stored Procedures
Calling Java from the Top Level............................................................................................................
Redirecting Output ............................................................................................................................
Examples of Calling Java Stored Procedures From the Top Level .............................................
Calling Java from Database Triggers ...................................................................................................
vi
7-1
7-2
7-2
7-4
Calling Java from SQL DML.................................................................................................................. 7-7
Calling Java from PL/SQL ...................................................................................................................... 7-8
Calling PL/SQL from Java ................................................................................................................... 7-10
How Oracle JVM Handles Exceptions .............................................................................................. 7-10
8
Java Stored Procedures Application Example
Drawing the Entity-Relationship Diagram......................................................................................... 8-1
Planning the Database Schema ............................................................................................................. 8-4
Creating the Database Tables ................................................................................................................ 8-4
Writing the Java Classes.......................................................................................................................... 8-6
Loading the Java Classes...................................................................................................................... 8-10
Publishing the Java Classes................................................................................................................. 8-10
Calling the Java Stored Procedures.................................................................................................... 8-11
9
Oracle Database Java Application Performance
Oracle JVM Just-in-Time Compiler (JIT) ............................................................................................
Overview of Oracle JVM JIT.............................................................................................................
Advantages of JIT Compilation .......................................................................................................
Methods Introduced in Oracle Database 11g.................................................................................
Java Memory Usage .................................................................................................................................
Configuring Memory Initialization Parameters ............................................................................
Initializing Pool Sizes within Database Templates ................................................................
Java Pool Memory ..............................................................................................................................
Displaying Used Amounts of Java Pool Memory .........................................................................
Correcting Out of Memory Errors ...................................................................................................
10
Security for Oracle Database Java Applications
Network Connection Security ............................................................................................................
Database Contents and Oracle JVM Security ..................................................................................
Java2 Security...................................................................................................................................
Setting Permissions .........................................................................................................................
Fine-Grain Definition for Each Permission ..........................................................................
General Permission Definition Assigned to Roles ............................................................
Debugging Permissions ...............................................................................................................
Permission for Loading Classes ..................................................................................................
Database Authentication Mechanisms ...........................................................................................
11
9-1
9-1
9-2
9-2
9-4
9-4
9-5
9-6
9-7
9-8
10-1
10-2
10-2
10-4
10-5
10-17
10-17
10-18
10-18
Schema Objects and Oracle JVM Utilities
Overview of Schema Objects..............................................................................................................
What and When to Load.......................................................................................................................
Resolution of Schema Objects............................................................................................................
Schema Object Digest Table...........................................................................................................
Compilation of Schema Objects.........................................................................................................
The ojvmtc Tool.....................................................................................................................................
The loadjava Tool..................................................................................................................................
11-1
11-2
11-2
11-3
11-4
11-5
11-6
vii
Syntax................................................................................................................................................
Argument Summary .......................................................................................................................
Argument Details ..........................................................................................................................
The dropjava Tool ...............................................................................................................................
Syntax..............................................................................................................................................
Argument Summary .....................................................................................................................
Argument Details ..........................................................................................................................
Dropping Resources .....................................................................................................................
The ojvmjava Tool ..............................................................................................................................
Syntax..............................................................................................................................................
Argument Summary .....................................................................................................................
Example ..........................................................................................................................................
Functionality ..................................................................................................................................
ojvmjava Options ...................................................................................................................
Shell Commands ....................................................................................................................
12
11-7
11-7
11-11
11-16
11-17
11-17
11-18
11-19
11-19
11-20
11-20
11-21
11-21
11-21
11-24
Database Web Services
Overview of Database Web Services.................................................................................................
Using Oracle Database as Web Services Provider ..........................................................................
How to Use JPublisher for Web Services Call-Ins ......................................................................
Features of Oracle Database as a Web Service Provider ...........................................................
Using Web Services with Oracle XML DB ...........................................................................
JPublisher Support for Web Services Call-Ins to Oracle Database ..........................................
Using Oracle Database as Web Services Consumer.......................................................................
How to Use Oracle Database for Web Services Call-Outs ........................................................
Web Service Data Sources (Virtual Table Support) ...................................................................
Features of Oracle Database as a Web Service Consumer ........................................................
Overview of JPublisher Generation..............................................................................................
Adjusting the Mapping of SQL Types .........................................................................................
A
DBMS_JAVA Package
longname...................................................................................................................................................
shortname..................................................................................................................................................
get_compiler_option ...............................................................................................................................
set_compiler_option................................................................................................................................
reset_compiler_option ............................................................................................................................
resolver ......................................................................................................................................................
derivedFrom .............................................................................................................................................
fixed_in_instance.....................................................................................................................................
set_output..................................................................................................................................................
start_debugging .......................................................................................................................................
stop_debugging .......................................................................................................................................
restart_debugging....................................................................................................................................
export_source............................................................................................................................................
export_class...............................................................................................................................................
export_resource ........................................................................................................................................
loadjava .....................................................................................................................................................
viii
12-1
12-1
12-2
12-2
12-3
12-3
12-3
12-4
12-5
12-6
12-6
12-8
A-1
A-1
A-1
A-1
A-2
A-2
A-2
A-3
A-3
A-3
A-4
A-4
A-4
A-4
A-4
A-4
dropjava.....................................................................................................................................................
grant_permission.....................................................................................................................................
restrict_permission..................................................................................................................................
grant_policy_permission........................................................................................................................
revoke_permission ..................................................................................................................................
disable_permission .................................................................................................................................
enable_permission ..................................................................................................................................
delete_permission ...................................................................................................................................
set_preference ..........................................................................................................................................
runjava.......................................................................................................................................................
runjava_in_current_session...................................................................................................................
set_property ..............................................................................................................................................
get_property..............................................................................................................................................
remove_property......................................................................................................................................
show_property .........................................................................................................................................
set_output_to_sql ....................................................................................................................................
remove_output_to_sql ............................................................................................................................
enable_output_to_sql .............................................................................................................................
disable_output_to_sql ............................................................................................................................
query_output_to_sql...............................................................................................................................
set_output_to_java ..................................................................................................................................
remove_output_to_java ..........................................................................................................................
enable_output_to_java .........................................................................................................................
disable_output_to_java ........................................................................................................................
query_output_to_java...........................................................................................................................
set_output_to_file..................................................................................................................................
remove_output_to_file .........................................................................................................................
enable_output_to_file...........................................................................................................................
disable_output_to_file..........................................................................................................................
query_output_to_file ............................................................................................................................
enable_output_to_trc ............................................................................................................................
disable_output_to_trc ...........................................................................................................................
query_output_to_trc..............................................................................................................................
endsession...............................................................................................................................................
endsession_and_related_state.............................................................................................................
set_native_compiler_option ................................................................................................................
unset_native_compiler_option ...........................................................................................................
compile_class..........................................................................................................................................
compile_class..........................................................................................................................................
uncompile_class.....................................................................................................................................
uncompile_class.....................................................................................................................................
compile_method ....................................................................................................................................
compile_method ....................................................................................................................................
uncompile_method ...............................................................................................................................
uncompile_method ...............................................................................................................................
A-5
A-5
A-5
A-5
A-6
A-6
A-6
A-6
A-6
A-6
A-7
A-7
A-7
A-7
A-8
A-8
A-8
A-8
A-9
A-9
A-9
A-9
A-10
A-10
A-10
A-10
A-10
A-10
A-11
A-11
A-11
A-11
A-11
A-11
A-12
A-12
A-12
A-12
A-12
A-12
A-13
A-13
A-13
A-13
A-13
ix
B
Classpath Extensions and User Classloaded Metadata
Classpath Extensions ..............................................................................................................................
jserverQuotedClassPathTermPrefix ...............................................................................................
jserverURLPrefix ...............................................................................................................................
jserverSpecialTokenPrefix................................................................................................................
JSERVER_CP......................................................................................................................................
JSERVER_SCHEMAc........................................................................................................................
jserver:/CP general syntax ..............................................................................................................
User Classloaded Metadata ...................................................................................................................
Index
x
B-1
B-1
B-1
B-1
B-2
B-2
B-2
B-3
xi
List of Figures
1–1
1–2
1–3
1–4
1–5
1–6
1–7
1–8
2–1
2–2
2–3
2–4
2–5
3–1
5–1
6–1
8–1
8–2
8–3
9–1
12–1
12–2
12–3
12–4
xii
Classes and Instances ................................................................................................................. 1-3
Java Component Structure ........................................................................................................ 1-6
Oracle Database Java Component Structure........................................................................... 1-7
Class Hierarchy ........................................................................................................................... 1-8
Two-Tier Client/Server Configuration.................................................................................... 1-9
Garbage Collection .................................................................................................................. 1-11
Interpreter versus Accelerator ............................................................................................... 1-14
Main Components of Oracle JVM ......................................................................................... 1-17
Java Environment Within Each Database Session ................................................................. 2-2
Loading Java into Oracle Database .......................................................................................... 2-4
Rights to Run Classes .............................................................................................................. 2-16
Invoker’s rights Solution......................................................................................................... 2-17
Indirect Access.......................................................................................................................... 2-18
Client-Side Stub Interface ....................................................................................................... 3-11
Calling a Stored Procedure........................................................................................................ 5-1
Calling a Java Method ................................................................................................................ 6-2
Rule for Drawing an E-R Diagram ........................................................................................... 8-2
E-R Diagram for Purchase Order Application........................................................................ 8-3
Schema Plan for Purchase Order Application ........................................................................ 8-4
Configuring Oracle JVM Memory Parameters ....................................................................... 9-6
Web Services Call-In to the Database.................................................................................... 12-2
Calling Web Services From Within the Database ............................................................... 12-5
Storing Results from Request in a Virtual Table ................................................................. 12-6
Creating Web Services Call-Out Stubs.................................................................................. 12-7
List of Tables
2–1
2–2
2–3
2–4
2–5
2–6
2–7
2–8
2–9
3–1
3–2
3–3
6–1
10–1
10–2
10–3
10–4
10–5
10–6
11–1
11–2
11–3
11–4
11–5
11–6
11–7
11–8
11–9
Description of Java Code and Classes..................................................................................... 2-4
Definitions for the Name and Option Parameters ................................................................ 2-7
Example JAVA$OPTIONS Table............................................................................................. 2-8
ORA Errors .............................................................................................................................. 2-11
Description of Java Files......................................................................................................... 2-12
loadjava Operations on Schema Objects.............................................................................. 2-13
Key USER_OBJECT Columns ............................................................................................... 2-18
Statement Auditing Options Related to Java Schema Objects ......................................... 2-20
Object Auditing Options Related to Java Schema Options .............................................. 2-21
Command Line Argument Summary .................................................................................. 3-10
set_output_to_sql Argument Summary .............................................................................. 3-15
set_output_to_java Argument Summary ............................................................................ 3-17
Legal Data Type Mappings ...................................................................................................... 6-3
Predefined Permissions........................................................................................................ 10-13
SYS Initial Permissions......................................................................................................... 10-15
PUBLIC Default Permissions .............................................................................................. 10-15
JAVAUSERPRIV Permissions ............................................................................................. 10-16
JAVASYSPRIV Permissions ................................................................................................ 10-16
JAVADEBUGPRIV Permissions ......................................................................................... 10-16
ojvmtc Argument Summary.................................................................................................. 11-5
loadjava Argument Summary............................................................................................... 11-8
dropjava Argument Summary............................................................................................ 11-17
ojvmjava Argument Summary............................................................................................ 11-20
ojvmjava Command Common Options............................................................................. 11-24
java Argument Summary .................................................................................................... 11-26
connect Argument Summary .............................................................................................. 11-27
runjava Argument Summary .............................................................................................. 11-27
jdwp Argument Summary................................................................................................... 11-28
xiii
xiv
Preface
This preface introduces you to the Oracle Database Java Developer’s Guide, discussing
the intended audience, structure, and conventions of this document. A list of related
Oracle documents is also provided.
Java has emerged as the object-oriented programming language of choice. It provides
platform independence and automated storage management techniques. It enables
you to create applications and applets. Oracle Database provides support for
developing and deploying Java applications.
This preface contains the following topics:
■
Audience
■
Documentation Accessibility
■
Related Documents
■
Conventions
Audience
The Oracle Database Java Developer’s Guide is intended for both Java and non-Java
developers. For PL/SQL developers who are not familiar with Java programming, this
manual provides a brief overview of Java and object-oriented concepts. For both Java
and PL/SQL developers, this manual discusses the following:
■
How Java and Database concepts merge
■
How to develop, load, and run Java stored procedures
■
Oracle JVM
■
Database concepts for managing Java objects in the database
■
Oracle Database and Java security policies
To use this document, you need knowledge of Oracle Database, SQL, and PL/SQL.
Prior knowledge of Java and object-oriented programming can be helpful.
Documentation Accessibility
Our goal is to make Oracle products, services, and supporting documentation
accessible, with good usability, to the disabled community. To that end, our
documentation includes features that make information available to users of assistive
technology. This documentation is available in HTML format, and contains markup to
facilitate access by the disabled community. Accessibility standards will continue to
evolve over time, and Oracle is actively engaged with other market-leading
xv
technology vendors to address technical obstacles so that our documentation can be
accessible to all of our customers. For more information, visit the Oracle Accessibility
Program Web site at
http://www.oracle.com/accessibility/
Accessibility of Code Examples in Documentation
Screen readers may not always correctly read the code examples in this document. The
conventions for writing code require that closing braces should appear on an
otherwise empty line; however, some screen readers may not always read a line of text
that consists solely of a bracket or brace.
Accessibility of Links to External Web Sites in Documentation
This documentation may contain links to Web sites of other companies or
organizations that Oracle does not own or control. Oracle neither evaluates nor makes
any representations regarding the accessibility of these Web sites.
TTY Access to Oracle Support Services
Oracle provides dedicated Text Telephone (TTY) access to Oracle Support Services
within the United States of America 24 hours a day, 7 days a week. For TTY support,
call 800.446.2398. Outside the United States, call +1.407.458.2479.
Related Documents
For more information, refer to the following Oracle resources:
■
Oracle Database JDBC Developer's Guide and Reference
■
Oracle Database JPublisher User's Guide
■
Oracle Database SQLJ Developer's Guide and Reference
■
Oracle Database Net Services Administrator's Guide
■
Oracle Database Advanced Security Administrator's Guide
■
Oracle Database Advanced Application Developer's Guide
Conventions
The following conventions are also used in this manual:
Convention
.
.
.
xvi
Meaning
Vertical ellipsis points in an example mean that information not directly
related to the example has been omitted.
...
Horizontal ellipsis points in statements or commands mean that parts
of the statement or command not directly related to the example have
been omitted
boldface text
Boldface type in text indicates a term defined in the text, the glossary,
or in both locations.
<>
Angle brackets enclose user-supplied names.
[]
Brackets enclose optional clauses from which you can choose one or
none.
What’s New in 11g Release 1 (11.1)
The following new Java-related features have been introduced in Oracle Database 11g
Release 1 (11.1):
■
Oracle JVM Compatibility with JDK 1.5
■
Oracle JVM Utilities Enhancements
■
Ease-of-Use Interface
■
Oracle JVM Just-in-Time Compiler (JIT)
Oracle JVM Compatibility with JDK 1.5
Sun Microsystems has introduced new features in Java Development Kit (JDK) 1.5. To
support these new features and enhancements, Oracle has upgraded Oracle JVM to the
latest Java 2 Platform, Standard Edition (J2SE).
Visit the following Web page to learn more about the new features introduced in JDK
1.5 :
http://java.sun.com/j2se/1.5.0/docs/relnotes/features.html
Oracle JVM Utilities Enhancements
In this release, the following enhancements have been added to Oracle JVM Utilities:
■
loadjava URL Support
■
List-Based Operation with dropjava
■
ojvmtc Tool
■
ojvmjava Tool Enhancements
loadjava URL Support
You can use an HTTP URL with the loadjava tool to load a JAR, class, or resource
from a remote server. This feature is discussed in detail in "The loadjava Tool" on
page 11-6.
List-Based Operation with dropjava
The dropjava command has been enhanced to provide an option that enables you to
drop classes, resources, or sources based on a list of classes, which might exist on the
client machine or the server machine. This feature is discussed in detail in "The
dropjava Tool" on page 11-16.
xvii
ojvmtc Tool
The ojvmtc tool enables you to close a specified set of classes, JARs, or both, and to
resolve all external references, prior to running the loadjava tool. This feature is
discussed in detail in "The ojvmtc Tool" on page 11-5.
ojvmjava Tool Enhancements
The ojvmjava tool has been enhanced to:
■
■
■
■
Recognize invalid commands and issue errors
Reduce the amount of stack trace information produced for an exception when it
is not in debug mode
Add a new connection command to allow connection changes without leaving the
ojvmjava tool
Add a new option runjava, which controls whether or not the ojvmjava shell
command java runs executable classes using the JDK-like command-line
interface or database resident classes.
This feature is discussed in detail in "The ojvmjava Tool" on page 11-19.
Ease-of-Use Interface
This section contains the following information about new features regarding ease of
use:
■
Using the Command-Line Interface
■
Database-Resident JARs
■
Sharing of Metadata for User Classloaded Classes
■
Two-Tier Duration for the Java Session State
■
Redirecting Output on the Server
■
Setting System Properties
Using the Command-Line Interface
The command-line interface to Oracle JVM is analogous to using the JDK or JRE Java
shell commands. This includes locating and running Java code from file-system using
standard -classpath syntax and setting of system properties using standard -D
syntax. This feature is discussed in detail in "Using Command-Line Interface" on
page 3-9.
Database-Resident JARs
Starting with 11g release 1 (11.1), when you load the contents of a JAR file into the
database, you have the option of creating a database object representing the JAR file
itself. In this way, you can retain an association between this JAR object and the class,
resource, and source objects loaded from the JAR. This feature is discussed in
"Database Resident JARs" on page 2-15.
Sharing of Metadata for User Classloaded Classes
From 11g release 1 (11.1), you can share class metadata of user classloaded classes.
This feature is discussed in "Sharing of Metadata for User Classloaded Classes" on
page 2-13.
xviii
Two-Tier Duration for the Java Session State
To support retention of system property settings and output specifications across Java
session termination, 11g release 1 (11.1) Oracle JVM supports two-tier duration for the
Java session state. This feature is discussed in "Two-Tier Duration for Java Session
State" on page 4-4.
Redirecting Output on the Server
Redirection of output on the server provides you with more extensive control over the
destination of output from Oracle JVM. This feature is discussed in "Redirecting
Output on the Server" on page 3-14.
Setting System Properties
Within an RDBMS session you can maintain a set of values that are added to the
system properties whenever a Java session is started in the RDBMS session. This
feature is discussed in "Setting System Properties" on page 4-4.
Using the Default Service Feature
Oracle Database 11g release 1 (11.1) introduces a new connection feature. Now, if you
install Oracle Database client, then you need not specify all the details in the
connection URL. This feature is discussed in "Using the Default Service Feature" on
page 3-12.
Oracle JVM Just-in-Time Compiler (JIT)
Starting with Oracle 11g release 1 (11.1), there is a just-in-time (JIT) compiler for
Oracle JVM environment. A just-in-time (JIT) compiler is a program that converts Java
bytecode into machine language instructions. Java programs compiled by a JIT
compiler run much faster than when the bytecode is executed by an interpreter. For
more information, refer to "Oracle JVM Just-in-Time Compiler (JIT)" on page 9-1.
xix
xx
1
Introduction to Java in Oracle Database
Oracle Database provides support for developing, storing, and deploying Java
applications. This chapter introduces the Java language to Oracle PL/SQL developers,
who are accustomed to developing server-side applications that are integrated with
SQL data. You can develop server-side Java applications that take advantage of the
scalability and performance of Oracle Database.
This chapter contains the following sections:
■
Overview of Java
■
Using Java in Oracle Database
■
Overview of Oracle JVM
■
Main Components of Oracle JVM
■
Java Application Strategy of Oracle
■
Memory Model for Dedicated Mode Sessions
Overview of Java
Java has emerged as the object-oriented programming language of choice. Some of the
important concepts of Java include:
■
Java virtual machine (JVM), which provides the fundamental basis for platform
independence
■
Automated storage management techniques, such as garbage collection
■
Language syntax that is similar to that of the C language
The result is a language that is object-oriented and efficient for application
programming.
This section covers the following topics:
■
Java and Object-Oriented Programming Terminology
■
Key Features of the Java Language
■
JVM
■
Java Class Hierarchy
Java and Object-Oriented Programming Terminology
The following terms are common in Java application development in Oracle Database
environment:
Introduction to Java in Oracle Database 1-1
Overview of Java
■
Classes
■
Objects
■
Interfaces
■
Encapsulation
■
Inheritance
■
Polymorphism
Classes
All object-oriented programming languages support the concept of a class. As with a
table definition, a class provides a template for objects that share common
characteristics. Each class can contain the following:
■
Attributes
Attributes are variables that are present in each object, or instance, of a particular
class. Attributes within an instance are known as fields. Instance fields are
analogous to the fields of a relational table row. The class defines the variables and
the type of each variable. You can declare variables in Java as static and
public, private, protected, or default access.
Variables of a class that are declared as static are global and common to all
instances of that class. Variables that are not declared as static are created
within each instance of the class.
The public, private, protected, and default access modifiers define the scope
of the variable in the application. The Java Language Specification (JLS) defines
the rules of visibility of data for all variables. These rules define under what
circumstances you can access the data in these variables.
In the example illustrated in Figure 1–1, the employee identifier is defined as
private, indicating that other objects cannot access this attribute directly. In the
example, objects can access the id attribute by calling the getId() method.
■
Methods
Methods are blocks of code that perform specific tasks or actions. You can call
methods on an instance of a class. You can also call methods that are inherited by
a class. Methods provide a way for instances to interact with other instances and
the application. Similar to attributes, methods can be declared as public,
private, protected, or default access.
Objects
A class needs to be instantiated before you can use the instance variables or attributes
and methods. An object is an instance of a class and is analogous to a relational table
row. The instance contains the attributes, which are known as its data or state, and the
methods defined in the class.
Figure 1–1 shows an example of an Employee class defined with two attributes, id,
which is the employee identifier, and lastName, which is the last name of the
employee, and the getId() and setId(String anId) methods. The id attribute
and the getId() method are private, and the lastName attribute and the
setId(String anId) method are public.
1-2 Oracle Database Java Developer’s Guide
Overview of Java
Figure 1–1 Classes and Instances
Classes and Instances
public class Employee
fields
Employee
new Employee ()
id = 215 63 2179
lastName = Smith
new Employee ()
id = 372 74 3215
lastName = Jones
private String id
public String lastName
...
methods
private getId ()
public setId (String anId)
...
Employee class defines
the fields that instances
hold (state) and methods
you can invoke on
instances of Employee
(behavior).
Employee
Each instance of
Employee holds its own
state. You can access that
state only if the creator of
the class defines it in a
way that provides access
to you.
When you create an instance, the attributes store individual and private information
relevant only to the employee. That is, the information contained within an employee
instance is known only to that particular employee. The example in Figure 1–1 shows
two instances of the Employee class, one for the employee Smith and one for Jones.
Each instance contains information relevant to the individual employee.
Interfaces
Java supports only single inheritance, that is, each class can inherit attributes and
methods of only one class. If you need to inherit properties from more than one
source, then Java provides the concept of interfaces, which is equivalent to multiple
inheritance. Interfaces are similar to classes. However, they define only the signature
of the methods and not their implementations. The methods that are declared in the
interface are implemented in the classes. Multiple inheritance occurs when a class
implements multiple interfaces.
Encapsulation
Encapsulation describes the ability of an object to hide its data and methods from the
rest of the world and is one of the fundamental principles of object-oriented
programming. In Java, a class encapsulates the attributes, which hold the state of an
object, and the methods, which define the actions of the object. Encapsulation enables
you to write reusable programs. It also enables you to restrict access only to those
features of an object that are declared public. All other attributes and methods are
private and can be used for internal object processing.
In the example illustrated in Figure 1–1, the id attribute is private, and access to it is
restricted to the object that defines it. Other objects can access this attribute using the
getId() method. Using encapsulation, you can deny access to the id attribute either
by declaring the getId() method as private or by not defining the getId()
method.
Inheritance
Inheritance is an important feature of object-oriented programming languages. It
enables classes to acquire properties of other classes. The class that inherits the
properties is called a child class or subclass, and the class from which the properties
are inherited is called a parent class or superclass. This feature also helps in reusing an
already defined code.
Introduction to Java in Oracle Database 1-3
Overview of Java
In the example illustrated in Figure 1–1, you can create a FullTimeEmployee class
that inherits the properties of the Employee class. The properties inherited depend on
the access modifiers declared for each attribute and method of the superclass.
Polymorphism
Polymorphism is the ability for different objects to respond differently to the same
message. In object-oriented programming languages, you can define one or more
methods with the same name. These methods can perform different actions and return
different values.
In the example in Figure 1–1, assume that the different types of employees must be
able to respond with their compensation to date. Compensation is computed
differently for different types of employees:
■
Full-time employees are eligible for a bonus.
■
Non-exempt employees get overtime pay.
In procedural languages, you write a switch statement, with the different possible
cases defined, as follows:
switch: (employee.type)
{
case: Employee
return employee.salaryToDate;
case: FullTimeEmployee
return employee.salaryToDate + employee.bonusToDate
...
}
If you add a new type of employee, then you must update the switch statement. In
addition, if you modify the data structure, then you must modify all switch
statements that use it. In an object-oriented language, such as Java, you can implement
a method, compensationToDate(), for each subclass of the Employee class, if it
contains information beyond what is already defined in the Employee class. For
example, you could implement the compensationToDate() method for a
non-exempt employee, as follows:
private float compensationToDate()
{
return (super.compensationToDate() + this.overtimeToDate());
}
For a full-time employee, the compensationToDate() method can be implemented
as follows:
private float compensationToDate()
{
return (super.compensationToDate() + this.bonusToDate());
}
This common use of the method name enables you to call methods of different classes
and obtain the required results, without specifying the type of the employee. You do
not have to write specific methods to handle full-time employees and part-time
employees.
In addition, you can create a Contractor class that does not inherit properties from
Employee and implements a compensationToDate() method in it. A program that
calculates total payroll to date would iterate over all people on payroll, regardless of
whether they were full-time or part-time employees or contractors, and add up the
1-4 Oracle Database Java Developer’s Guide
Overview of Java
values returned from calling the compensationToDate() method on each. You can
safely make changes to the individual compensationToDate() methods or the
classes, and know that callers of the methods will work correctly.
Key Features of the Java Language
The Java language provides certain key features that make it ideal for developing
server applications. These features include:
■
Simplicity
Java is simpler than most other languages that are used to create server
applications, because of its consistent enforcement of the object model. The large,
standard set of class libraries brings powerful tools to Java developers on all
platforms.
■
Portability
Java is portable across platforms. It is possible to write platform-dependent code
in Java, and it is also simple to write programs that move seamlessly across
systems.
See Also:
■
"JVM" on page 1-6
Automatic storage management
JVM automatically performs all memory allocation and deallocation while the
program is running. Java programmers cannot explicitly allocate memory for new
objects or free memory for objects that are no longer referenced. Instead, they
depend on JVM to perform these operations. The process of freeing memory is
known as garbage collection.
■
Strong typing
Before you use a variable, you must declare the type of the variable. Strong typing
in Java makes it possible to provide a reasonable and safe solution to
interlanguage calls between Java and PL/SQL applications, and to integrate Java
and SQL calls within the same application.
■
No pointers
Although Java is quite similar to C in its syntax, it does not support direct pointers
or pointer manipulation. You pass all parameters, except primitive types, by
reference and not by value. As a result, the object identity is preserved. Java does
not provide low level, direct access to pointers, thereby eliminating any possibility
of memory corruption and leaks.
■
Exception handling
Java exceptions are objects. Java requires developers to declare which exceptions
can be thrown by methods in any particular class.
■
Flexible namespace
Java defines classes and places them within a hierarchical structure that mirrors
the domain namespace of the Internet. You can distribute Java applications and
avoid name collisions. Java extensions, such as the Java Naming and Directory
Interface (JNDI), provide a framework for multiple name services to be federated.
The namespace approach of Java is flexible enough for Oracle to incorporate the
concept of a schema for resolving class names in full compliance with the JLS.
■
Security
Introduction to Java in Oracle Database 1-5
Overview of Java
The design of Java bytecodes and JVM allow for built-in mechanisms to verify the
security of Java binary code. Oracle Database is installed with an instance of
Security Manager that, when combined with Oracle Database security, determines
who can call any Java methods.
■
Standards for connectivity to relational databases
Java Database Connectivity (JDBC) and SQLJ enable Java code to access and
manipulate data in relational databases. Oracle provides drivers that allow
vendor-independent, portable Java code to access the relational database.
JVM
As with other high-level computer languages, the Java source compiles to low-level
machine instructions. In Java, these instructions are known as bytecodes, because each
instruction has a uniform size of one byte. Most other languages, such as C, compile to
machine-specific instructions, such as instructions specific to an Intel or HP processor.
When compiled, the Java code gets converted to a standard, platform-independent set
of bytecodes, which interacts with a JVM. JVM is a separate program that is optimized
for the specific platform on which you run your Java code.
Figure 1–2 illustrates how Java can maintain platform independence. Each platform
has JVM installed that is specific to the operating system. The Java bytecodes get
interpreted through JVM into the appropriate platform dependent actions.
Figure 1–2 Java Component Structure
Java Application
Java Virtual Machine
Operating System
When you develop a Java application, you use predefined core class libraries written
in the Java language. The Java core class libraries are logically divided into packages
that provide commonly used functionality. Basic language support is provided by the
java.lang package, I/O support is provided by the java.io package, and network
access is provided by the java.net package. Together, JVM and core class libraries
provide a platform on which Java programmers can develop applications, which will
run successfully on any operating system that supports Java. This concept is what
drives the "write once, run anywhere" idea of Java.
Figure 1–3 illustrates how Oracle Java applications reside on top of the Java core class
libraries, which reside on top of JVM. Because the Oracle Java support system is
located within the database, JVM interacts with Oracle Database libraries, instead of
directly interacting with the operating system.
1-6 Oracle Database Java Developer’s Guide
Overview of Java
Figure 1–3 Oracle Database Java Component Structure
Java Server Applications
Oracle-Supported Java APIs: SQLJ, JDBC, JNDI
Java Core Class Libraries
Oracle Database JVM
Oracle Database Libraries
Operating System
Sun Microsystems provides publicly available specifications for both the Java
language and the JVM. The JLS defines the syntax and semantics, and JVM
specification defines the necessary low-level actions for the system that runs the
application. In addition, Sun Microsystems provides a compatibility test suite for JVM
implementors to determine if they have complied with the specifications. This test
suite is known as the Java Compatibility Kit (JCK). Oracle JVM implementation
complies fully with JCK. Part of the overall Java strategy is that an openly specified
standard, together with a simple way to verify compliance with that standard, allows
vendors to offer uniform support for Java across all platforms.
Java Class Hierarchy
Java defines classes within a large hierarchy of classes. At the top of the hierarchy is
the Object class. All classes in Java inherit from the Object class at some level, as
you walk up through the inheritance chain of superclasses. When we say Class B
inherits from Class A, each instance of Class B contains all the fields defined in class B,
as well as all the fields defined in Class A.
Figure 1–4 illustrates a generic Java class hierarchy. The FullTimeEmployee class
contains the id and lastName fields defined in the Employee class, because it
inherits from the Employee class. In addition, the FullTimeEmployee class adds
another field, bonus, which is contained only within FullTimeEmployee.
You can call any method on an instance of Class B that was defined in either Class A
or Class B. In the example, the FullTimeEmployee instance can call methods defined
only in the FullTimeEmployee class and methods defined in the Employee class.
Introduction to Java in Oracle Database 1-7
Using Java in Oracle Database
Figure 1–4 Class Hierarchy
Using Inheritance to Localize Behavior and State
Employee class has two
subclasses,
PartTimeEmployee and
FullTimeEmployee,
rather than using
attributes of Employee to
differentiate between
different Employee types.
class Employee
id
lastName
class PartTimeEmployee
class FullTimeEmployee
schedule
bonus
Each
FullTimeEmployee is
considered exempt
if he works for a
monthly salary, or
non-exempt if he
works at an hourly
rate. Each one
computes
salaryToDate
differently.
PartTimeEmployees
have to track their
schedules, while
FullTimeEmployees
are eligible for bonuses.
class ExemptEmployee
class NonExemptEmployee
salaryToDate()
salaryToDate()
Instances of Class B can be substituted for instances of Class A, which makes
inheritance another powerful construct of object-oriented languages for improving
code reuse. You can create classes that define behavior and state where it makes sense
in the hierarchy, yet make use of preexisting functionality in class libraries.
Using Java in Oracle Database
You can write and load Java applications within the database because it is a safe
language with a lot of security features. Java has been developed to prevent anyone
from tampering with the operating system where the Java code resides in. Some
languages, such as C, can introduce security problems within the database. However,
Java, because of its design, is a robust language that can be used within the database.
Although the Java language presents many advantages to developers, providing an
implementation of a JVM that supports Java server applications in a scalable manner is
a challenge. This section discusses the following challenges:
■
Java and RDBMS: A Robust Combination
■
Multithreading
■
Automated Storage Management With Garbage Collection
■
Footprint
■
Performance of Oracle JVM
■
Dynamic Class Loading
Java and RDBMS: A Robust Combination
Oracle Database provides Java applications with a dynamic data-processing engine
that supports complex queries and different views of the same data. All client requests
are assembled as data queries for immediate processing, and query results are
generated dynamically.
1-8 Oracle Database Java Developer’s Guide
Using Java in Oracle Database
The combination of Java and Oracle Database helps you to create component-based,
network-centric applications that can be easily updated as business needs change. In
addition, you can move applications and data stores off the desktop and onto
intelligent networks and network-centric servers. More important, you can access
those applications and data stores from any client device.
Figure 1–5 shows a traditional two-tier, client/server configuration in which clients
call Java stored procedures the same way they call PL/SQL stored procedures. The
figure also shows how the Oracle Net Services Connection Manager can combine
many network connections into a single database connection. This enables Oracle
Database to support a large number of concurrent users.
Figure 1–5 Two-Tier Client/Server Configuration
Oracle Database
Thin Client
NC
Java
Applet
JDBC
Driver
Oracle Net
Relational
Data
Object Relational
Data
Fat Client
OCI
Clients
Pre*
Client
ODBC
Client
Oracle Net
Oracle Net
Connection
Manager
Oracle Net
Java Stored
Procedure
Oracle Forms and Oracle Reports
Oracle Net
PL/SQL Stored
Procedure
Multithreading
Multithreading is one of the key scalability features of the Java language. The Java
language and class libraries make it simpler to write multithreaded applications in
Java than many other languages, but it is still a daunting task in any language to write
reliable, scalable multithreaded code.
Oracle Database server efficiently schedules work for thousands of users. Oracle JVM
uses the facilities of the database server to concurrently schedule the running of Java
application for thousands of users. Although Oracle Database supports Java
language-level threads required by the JLS and JCK, scalability will not increase by
using threads within the scope of the database. By using the embedded scalability of
the database, the need for writing multithreaded Java servers is eliminated.
You should use the facilities of Oracle Database for scheduling users by writing
single-threaded Java applications. The database can schedule processes between each
application, and thus, you achieve scalability without having to manage threads. You
can still write multithreaded Java applications, but multiple Java threads will not
increase the performance of the server.
One complication multithreading creates is the interaction of threads and automated
storage management or garbage collection. The garbage collector running in a generic
JVM has no knowledge of which Java language threads are running or how the
underlying operating system schedules them. The difference between a non-Oracle
Database model and Oracle JVM model is as follows:
■
Non-Oracle Database model
A single user maps to a single Java thread and a single garbage collector manages
all garbage from all users. Different techniques typically deal with allocation and
Introduction to Java in Oracle Database 1-9
Using Java in Oracle Database
collection of objects of varying lifetimes and sizes. The result in a heavily
multithreaded application is, at best, dependent upon operating system support
for native threads, which can be unreliable and limited in scalability. High levels
of scalability for such implementations have not been convincingly demonstrated.
■
Oracle JVM model
Even when thousands of users connect to the server and run the same Java code,
each user experiences it as if he or she is running his or her own Java code on his
or her own JVM. The responsibility of Oracle JVM is to make use of operating
system processes and threads and the scalable approach of Oracle Database. As a
result of this approach, the garbage collector of Oracle JVM is more reliable and
efficient because it never collects garbage from more than one user at any time.
See Also:
"Threading in Oracle Database" on page 2-32
Automated Storage Management With Garbage Collection
Garbage collection is a major function of the automated storage management feature
of Java, eliminating the need for Java developers to allocate and free memory
explicitly. Consequently, this eliminates a large source of memory leaks that are
commonly found in C and C++ programs. However, garbage collection contributes to
the overhead of program execution speed and footprint.
Garbage collection imposes a challenge to the JVM developer seeking to supply a
highly scalable and fast Java platform. Oracle JVM meets these challenges in the
following ways:
■
■
■
Oracle JVM uses Oracle Database scheduling facilities, which can manage multiple
users efficiently.
Garbage collection is performed consistently for multiple users, because garbage
collection is focused on a single user within a single session. Oracle JVM has an
advantage, because the burden and complexity of the job of the memory manager
does not increase as the number of users increases. The memory manager
performs the allocation and collection of objects within a single session, which
typically translates to the activity of a single user.
Oracle JVM uses different garbage collection techniques depending on the type of
memory used. These techniques provide high efficiency and low overhead.
The two types of memory space are call space and session space.
Memory space
Description
Call space
It is a fast and inexpensive type of memory. It primarily exists for the
length of a call. Call memory space is divided into new and old
segments. All new objects are created within new memory. Objects that
have survived several scavenges are moved into old memory.
Session space
It is an expensive, performance-wise memory. It primarily exists for the
length of a session. All static variables and any objects that exist
beyond the lifetime of a call exist here.
Figure 1–6 illustrates the different actions performed by the garbage collector.
1-10 Oracle Database Java Developer’s Guide
Using Java in Oracle Database
Figure 1–6 Garbage Collection
Call and Sessions Memory Space
Garbage collected
often and very
quicklyduring Call
Call Memory
“new” Objects
go here
New Space
Garbage collected
less often
during Call
Old Space
Survived objects
after several
scavenging
Garbage collected
at end of Call
Session Memory
Survived objects
after the end
of a call
Garbage collection algorithms within Oracle JVM adhere to the following rules:
1.
New objects are created within a new call space.
2.
Scavenging occurs at a set interval. Some programmers create objects frequently
for only a short duration. These types of objects are created and garbage-collected
quickly within the new call space. This is known as scavenging.
3.
Any objects that have survived several iterations of scavenging are considered to
be objects that can exist for a while. These objects are moved out of new call space
into old call space. During the move, they are also compacted. Old call space is
scavenged or garbage collected less often and, therefore, provides better
performance.
4.
At the end of the call, any objects that are to exist beyond the call are moved into
session space.
Figure 1–6 illustrates the steps listed in the preceding text. This approach applies
sophisticated allocation and collection schemes tuned to the types and lifetimes of
objects. For example, new objects are allocated in fast and inexpensive call memory,
designed for quick allocation and access. Objects held in Java static variables are
migrated to the more precious and expensive session space.
Footprint
The footprint of a running Java program is affected by many factors:
■
Size of the program
The size of the program depends on the number of classes and methods and how
much code they contain.
■
Complexity of the program
The complexity of the program depends on the number of core class libraries that
Oracle JVM uses as the program runs, as opposed to the program itself.
■
Amount of space JVM uses
The amount of space JVM uses depends on the number of objects JVM allocates,
how large these objects are, and how many objects must be retained across calls.
Introduction to Java in Oracle Database
1-11
Using Java in Oracle Database
■
Ability of the garbage collector and memory manager to deal with the demands of
the program running
This can not be determined often. The speed with which objects are allocated and
the way they are held on to by other objects influences the importance of this
factor.
From a scalability perspective, the key to supporting multiple clients concurrently is a
minimum per-user session footprint. Oracle JVM keeps the per-user session footprint
to a minimum by placing all read-only data for users, such as Java bytecodes, in
shared memory. Appropriate garbage collection algorithms are applied against call
and session memories to maintain a small footprint for the user's session. Oracle JVM
uses the following types of garbage collection algorithms to maintain the user's session
memory:
■
Generational scavenging for short-lived objects
■
Mark and lazy sweep collection for objects that exist for the life of a single call
■
Copying collector for long-lived objects, that is, objects that live across calls within
a session
Performance of Oracle JVM
The performance of Oracle JVM is enhanced by implementing a native compiler. The
platform-independent Java bytecodes run on top of a JVM, and JVM interacts with the
specific hardware platform. Any time you add levels within software, the performance
is degraded. Because Java requires going through an intermediary to interpret the
bytecodes, a degree of inefficiency exists for Java applications as compared to
applications developed using a platform-dependent language, such as C. To address
this issue, several JVM suppliers create native compilers. Native compilers translate
Java bytecodes into platform-dependent native code, which eliminates the interpreter
step and improves performance.
The following table describes two methods for native compilation:
Compiler
Description
Just-In-Time (JIT)
Compilation
JIT compilers quickly compile Java bytecodes to platform-specific, or
native, machine code during run time. These compilers do not produce an
executable file to be run on the platform. Instead, they provide
platform-dependent code from Java bytecodes that is run directly after it
is translated. JIT compilers should be used for Java code that is run
frequently and at speeds closer to that of code developed in other
languages, such as C.
Ahead-of-Time
Compilation
This compilation translates Java bytecodes to platform-independent C
code before run time. Then a standard C compiler compiles the C code
into an executable file for the target platform. This approach is more
suitable for Java applications that are not modified frequently. This
approach takes advantage of the mature and efficient platform-specific
compilation technology found in modern C compilers.
Oracle Database uses Ahead-of-Time compilation to deliver its core Java class
libraries, such as JDBC code, in natively compiled form. It is applicable across all the
platforms Oracle supports. A JIT approach requires low-level, processor-dependent
code to be written and maintained for each platform. You can use this native
compilation technology with your own Java code.
1-12 Oracle Database Java Developer’s Guide
Using Java in Oracle Database
Figure 1–7 illustrates how natively compiled code runs up to 10 times faster than
interpreted code. As a result, the more native code your program uses, the faster it
runs.
Figure 1–7 Interpreter versus Accelerator
Java Source Code
Java Compiler
Java Bytecode
Java Interpreter
Accelerator
Execution speed is X
C Source Code
Platform C Compiler
Native Code
Execution Speed is 2X to 10X
(depends on the number of casts,
array accesses, message sends,
accessor calls, etc. in the code)
Dynamic Class Loading
Another strong feature of Java is dynamic class loading. The class loader loads classes
from the disk and places them in the JVM-specific memory structures necessary for
interpretation. The class loader locates the classes in CLASSPATH and loads them only
when they are used while the program is running. This approach, which works well
for applets, poses the following problems in a server environment:
Problem
Description
Solution
Predictability
The class loading operation places a severe
penalty when the program is run for the first
time. A simple program can cause Oracle
JVM to load many core classes to support its
needs. A programmer cannot easily predict
or determine the number of classes loaded.
Oracle JVM loads classes dynamically, just as
with any other JVM. The same one-time class
loading speed hit is encountered. However,
because the classes are loaded into shared
memory, no other users of those classes will
cause the classes to load again, and they will
use the same preloaded classes.
Introduction to Java in Oracle Database
1-13
Overview of Oracle JVM
Problem
Description
Solution
Reliability
A benefit of dynamic class loading is that it
supports program updating. For example,
you would update classes on a server, and
clients, who download the program and
load it dynamically, see the update
whenever they next use the program. Server
programs tend to emphasize reliability. As a
developer, you must know that every client
runs a specific program configuration. You
do not want clients to inadvertently load
some classes that you did not intend them to
load.
Oracle Database separates the upload and
resolve operation from the class loading
operation at run time. You upload Java code
you developed to the server using the
loadjava tool. Instead of using CLASSPATH,
you specify a resolver at installation time. The
resolver is analogous to CLASSPATH, but
enables you to specify the schemas in which
the classes reside. This separation of
resolution from class loading ensures that you
always know what programs users run.
See Also: Chapter 11, "Schema Objects and
Oracle JVM Utilities"
Overview of Oracle JVM
Oracle JVM is a standard, Java-compatible environment that runs any pure Java
application. It is compatible with the JLS and the JVM specification laid down by Sun
Microsystems. It supports the standard Java binary format and the standard Java APIs.
In addition, Oracle Database adheres to standard Java language semantics, including
dynamic class loading at run time.
Java in Oracle Database introduces the following terms:
■
Session
A session in Oracle Database Java environment is identical to the standard Oracle
Database usage. A session is typically, although not necessarily, bounded by the
time a single user connects to the server. As a user who calls a Java code, you must
establish a session in the server.
■
Call
When a user causes a Java code to run within a session, it is termed as a call. A call
can be started in the following different ways:
–
A SQL client program runs a Java stored procedure.
–
A trigger runs a Java stored procedure.
–
A PL/SQL program calls a Java code.
In all the cases defined, a call begins, some combination of Java, SQL, or PL/SQL
code is run to completion, and the call ends.
The concept of session and call apply across all uses of Oracle
Database.
Note:
Unlike other Java environments, Oracle JVM is embedded within Oracle Database and
introduces a number of new concepts. This section discusses some important
differences between Oracle JVM and typical client JVMs based on:
■
Process Area
■
The main() Method
■
The GUI
■
The IDE
1-14 Oracle Database Java Developer’s Guide
Main Components of Oracle JVM
Process Area
In a standard Java environment, you run a Java application through the interpreter by
issuing the following command on the command line, where classname is the name
of the class that you want the JVM to interpret first:
java classname
This command causes the application to run within a process on your operating
system. However, if you are not using the command-line interface, you must load the
application into the database, publish the interface, and then run the application
within a database session.
Chapter 2, "Java Applications on Oracle Database" for
information about loading, publishing, and running Java applications
See Also:
The main() Method
Client-based Java applications declare a single, top-level method, public static
void main(String args[]). This method defines the profile of an application. As
with applets, server-based applications have no such inner loop. Instead, they are
driven by logically independent clients.
Each client begins a session, calls its server-side logic modules through top-level entry
points, and eventually ends the session. The server environment hides the process of
management of sessions, networks, and other shared resources from hosted Java
programs.
The GUI
A server cannot provide GUIs, but it can provide the logic that drives them. Oracle
JVM supports only the headless mode of the Java Abstract Window Toolkit (AWT).
All Java AWT classes are available within the server environment and your programs
can use the Java AWT functionality, as long as they do not attempt to materialize a
GUI on the server.
See Also:
"User Interfaces on the Server" on page 2-21
The IDE
Oracle JVM is oriented to Java application deployment, and not development. You can
write and test applications on any preferred integrated development environment
(IDE), such as Oracle JDeveloper, and then deploy them within the database for the
clients to access and run them.
See Also:
"Development Tools" on page 1-22
The binary compatibility of Java enables you to work on any IDE and then upload the
Java class files to the server. You need not move your Java source files to the database.
Instead, you can use powerful client-side IDEs to maintain Java applications that are
deployed on the server.
Main Components of Oracle JVM
This section briefly describes the main components of Oracle JVM and some of the
facilities they provide.
Introduction to Java in Oracle Database
1-15
Main Components of Oracle JVM
Oracle JVM is a complete, Java2-compliant environment for running Java applications.
It runs in the same process space and address space as the database kernel by sharing
its memory heaps and directly accessing its relational data. This design optimizes
memory use and increases throughput.
Oracle JVM provides a run-time environment for Java objects. It fully supports Java
data structures, method dispatch, exception handling, and language-level threads. It
also supports all the core Java class libraries, including java.lang, java.io,
java.net, java.math, and java.util.
Figure 1–8 shows the main components of Oracle JVM.
Figure 1–8 Main Components of Oracle JVM
Oracle JVM
Interpreter &
Run-time System
Memory
SQL Calls
Natively
Compiled Code
loadjava Utility
CREATE JAVA Statement
Class Loader
Garbage Collector
RDBMS
Library Manager
RDBMS
Memory Manager
Oracle JVM embeds the standard Java namespace in the database schemas. This
feature lets Java programs access Java objects stored in Oracle Database and
application servers across the enterprise.
In addition, Oracle JVM is tightly integrated with the scalable, shared memory
architecture of the database. Java programs use call, session, and object lifetimes
efficiently without user intervention. As a result, Oracle JVM and middle-tier Java
business objects can be scaled, even when they have session-long state.
The following sections provide an overview of some of the components of Oracle JVM
and the JDBC driver and the SQLJ translator:
■
Library Manager
■
Compiler
■
Interpreter
■
Class Loader
■
Verifier
■
Server-Side JDBC Internal Driver
■
Server-Side SQLJ Translator
■
System Classes
See Also: "Automated Storage Management With Garbage
Collection" on page 1-10 and "Performance of Oracle JVM" on
page 1-12
Library Manager
To store Java classes in Oracle Database, you use the loadjava command-line tool,
which uses the SQL CREATE JAVA statements to do its work. When called by the
1-16 Oracle Database Java Developer’s Guide
Main Components of Oracle JVM
CREATE JAVA {SOURCE | CLASS | RESOURCE} statement, the library manager
loads Java source, class, or resource files into the database. These Java schema objects
are not accessed directly, and only Oracle JVM uses them.
Compiler
Oracle JVM includes a standard Java compiler. When the CREATE JAVA SOURCE
statement is run, it translates Java source files into architecture-neutral, one-byte
instructions known as bytecodes. Each bytecode consists of an opcode followed by its
operands. The resulting Java class files, which conform fully to the Java standard, are
submitted to the interpreter at run time.
Interpreter
To run Java programs, Oracle JVM includes a standard Java2 bytecode interpreter. The
interpreter and the associated Java run-time system run standard Java class files. The
run-time system supports native methods and call-in and call-out from the host
environment.
You can also compile your Java code to improve performance.
Oracle JVM uses natively compiled versions of the core Java class
libraries, SQLJ translator, and JDBC drivers.
Note:
Class Loader
In response to requests from the run-time system, the Java class loader locates, loads,
and initializes Java classes stored in the database. The class loader reads the class and
generates the data structures needed to run it. Immutable data and metadata are
loaded into initialize-once shared memory. As a result, less memory is required for
each session. The class loader attempts to resolve external references when necessary.
In addition, if the source files are available, then the class loader calls the Java compiler
automatically when Java class files must be recompiled.
Verifier
Java class files are fully portable and conform to a well-defined format. The verifier
prevents the inadvertent use of spoofed Java class files, which might alter program
flow or violate access restrictions. Oracle security and Java security work with the
verifier to protect your applications and data.
Server-Side JDBC Internal Driver
JDBC is a standard and defines a set of Java classes providing vendor-independent
access to relational data. Specified by Sun Microsystems and modeled after ODBC and
the X/Open SQL Call Level Interface (CLI), the JDBC classes provide standard
features, such as simultaneous connections to several databases, transaction
management, simple queries, calls to stored procedures, and streaming access to LONG
column data.
Using low-level entry points, a specially tuned JDBC driver runs directly inside Oracle
Database, providing fast access to Oracle data from Java stored procedures. The
server-side JDBC internal driver complies fully with the standard JDBC specification.
Tightly integrated with the database, the JDBC driver supports Oracle-specific data
types, globalization character sets, and stored procedures. In addition, the client-side
and server-side JDBC APIs are the same, which makes it easy to partition applications.
Introduction to Java in Oracle Database
1-17
Java Application Strategy of Oracle
Server-Side SQLJ Translator
SQLJ enables you to embed SQL statements in Java programs. It is more concise than
JDBC and more responsive to static analysis and type checking. The SQLJ
preprocessor, which itself is a Java program, takes as input a Java source file in which
SQLJ clauses are embedded. Then, it translates the SQLJ clauses into Java class
definitions that implement the specified SQL statements. The Java type system ensures
that objects of those classes are called with the correct arguments.
A highly optimized SQLJ translator runs directly inside the database, where it
provides run-time access to Oracle data using the server-side internal JDBC driver.
SQLJ forms can include queries, data manipulation language (DML) statements, data
definition language (DDL) statements, transaction control statements, and calls to
stored procedures. The client-side and server-side SQLJ APIs are identical, making it
easy to partition applications.
System Classes
A set of classes that constitute a significant portion of the implementation of Java in
Oracle Database environment is known as the System classes. These classes are
defined in the SYS schema and exported for all users by public synonym. A class with
the same name as one of the System classes can be defined in a schema other than the
SYS schema1. But, this is a bad practice because the alternate version of the class may
behave in a manner that violates assumptions about the semantics of that class that are
present in other System classes or in the underlying implementation of Java Virtual
Machine. Oracle strongly discourages this practice.
Java Application Strategy of Oracle
Oracle provides enterprise application developers an end-to-end Java solution for
creating, deploying, and managing Java applications. The total solution consists of
client-side and server-side programmatic interfaces, tools to support Java
development, and a JVM integrated with Oracle Database. All these products are fully
compatible with Java standards. This section covers the following topics:
■
Java in Database Application Development
■
Java Programming Environment
■
Java Stored Procedures
■
PL/SQL Integration and Oracle RDBMS Functionality
■
Development Tools
Java in Database Application Development
The most important features of Java in database application development are:
■
■
1
Providing flexible partitioning of Java2 Platform, Standard Edition (J2SE)
applications for symmetric data access at the JDBC and SQLJ level.
Bridging SQL and the Java2 Platform, Enterprise Edition (J2EE) world by:
–
Calling out Web components, such as JSP and servlet
–
Calling out Enterprise JavaBean (EJB) components
You cannot always define a class with the same name as one of the System Classes. For the
classes present in some packages, for example, java.lang, such definitions are explicitly
prohibited by the code.
1-18 Oracle Database Java Developer’s Guide
Java Application Strategy of Oracle
–
Bridging SQL and Web Services
*
Calling out Web Services
–
Using Oracle JVM as ERP Integration Hub
–
Invalidating cache
Java Programming Environment
In addition to Oracle JVM, the Java programming environment provides:
■
Java stored procedures as the Java equivalent and companion for PL/SQL. Java
stored procedures are tightly integrated with PL/SQL. You can call Java stored
procedures from PL/SQL packages and PL/SQL procedures from Java stored
procedures.
■
The JDBC and SQLJ programming interfaces for accessing SQL data.
■
Tools and scripts that assist in developing, loading, and managing classes.
The following table helps you decide when to use which Java API:
Type of functionality you need
Java API to use
To have a Java procedure called from SQL, such as a trigger.
Java stored procedures
To call a static, simple SQL statement from a known table with
known column names from a Java object.
SQLJ
To call dynamic, complex SQL statements from a Java object.
JDBC
Java Stored Procedures
Java stored procedures are Java programs written and deployed on a server and run
from the server, exactly like a PL/SQL stored procedure. You invoke it directly with
products like SQL*Plus, or indirectly with a trigger. You can access it from any Oracle
Net client, such as OCI and PRO*, or JDBC or SQLJ.
See Also:
Chapter 5, "Developing Java Stored Procedures"
In addition, you can use Java to develop powerful, server-side programs, which can be
independent of PL/SQL. Oracle Database provides a complete implementation of the
standard Java programming language and a fully compliant JVM.
PL/SQL Integration and Oracle RDBMS Functionality
You can call existing PL/SQL programs from Java and Java programs from PL/SQL.
This solution protects and leverages your PL/SQL and Java code and opens up the
advantages and opportunities of Java-based Internet computing.
Oracle Database offers two different Java APIs for accessing SQL data, JDBC and
SQLJ. Both these APIs are available on the client and the server. As a result, you can
deploy your applications on the client and server, without modifying the code.
The following topics introduce the Java APIs and the JPublisher tool provided by
Oracle Database:
■
JDBC Drivers
■
SQLJ
■
JPublisher
Introduction to Java in Oracle Database
1-19
Java Application Strategy of Oracle
JDBC Drivers
JDBC is a database access protocol that enables you to connect to a database and run
SQL statements and queries to the database. The core Java class libraries provide only
one JDBC API, java.sql. However, JDBC is designed to enable vendors to supply
drivers that offer the necessary specialization for a particular database. Oracle
provides the following distinct JDBC drivers:
Driver
Description
JDBC Thin driver
You can use the JDBC Thin driver to write pure Java applications and
applets that access Oracle SQL data. The JDBC Thin driver is especially
well-suited for Web-based applications and applets, because you can
dynamically download it from a Web page, similar to any other Java
applet.
JDBC OCI driver
The JDBC OCI driver accesses Oracle-specific native code, that is,
non-Java code, and libraries on the client or middle tier, providing
performance boost compared to the JDBC Thin driver, at the cost of
significantly larger size and client-side installation.
JDBC server-side
internal driver
Oracle Database uses the server-side internal driver when the Java code
runs on the server. It allows Java applications running in Oracle JVM on
the server to access locally defined data, that is, data on the same system
and in the same process, with JDBC. It provides a performance boost,
because of its ability to use the underlying Oracle RDBMS libraries
directly, without the overhead of an intervening network connection
between the Java code and SQL data. By supporting the same Java-SQL
interface on the server, Oracle Database does not require you to rework
code when deploying it.
See Also:
■
"Utilizing SQLJ and JDBC with Java in the Database" on page 3-3
■
Oracle Database JDBC Developer's Guide and Reference
SQLJ
Oracle has worked with other vendors, including IBM, Tandem, Sybase, and Sun
Microsystems, to develop a standard way to embed SQL statements in Java programs
called SQLJ. This work has resulted in a new standard, ANSI x.3.135.10-1998, for a
simpler and more highly productive programming API than JDBC. A user writes
applications to this higher-level API and then uses a preprocessor to translate the
program to standard Java source with JDBC calls. At run time, the program can
communicate with multi-vendor databases using standard JDBC drivers.
SQLJ provides a simple, but powerful, way to develop both client-side and middle-tier
applications that access databases from Java. You can use SQLJ in stored procedures,
triggers, and methods within the Oracle Database 10g environment. In addition, you
can combine SQLJ programs with JDBC.
The SQLJ translator is a Java program that translates embedded SQL in Java source
code to pure JDBC-based Java code. Because Oracle Database 10g provides a complete
Java environment, you cannot compile SQLJ programs on a client that will run on the
server. Instead, you can compile them directly on the server. The adherence of Oracle
Database to the Internet standards enables you to choose the development style as per
your requirements.
1-20 Oracle Database Java Developer’s Guide
Memory Model for Dedicated Mode Sessions
See Also:
■
"Utilizing SQLJ and JDBC with Java in the Database" on page 3-3
■
Oracle Database SQLJ Developer's Guide and Reference
JPublisher
JPublisher provides a simple and convenient tool to create Java programs that access
existing Oracle relational database tables.
See Also:
Oracle Database JPublisher User's Guide
Development Tools
The introduction of Java in Oracle Database enables you to use several Java IDEs. The
adherence of Oracle Database to the Java standards and specifications and the open
Internet standards and protocols ensures that your Java programs work successfully,
when you deploy them on Oracle Database. Oracle provides many tools or utilities
that are written in Java making development and deployment of Java server
applications easier. Oracle JDeveloper, a Java IDE provided by Oracle, has many
features designed specifically to make deployment of Java stored procedures and EJBs
easier. You can download JDeveloper from:
http://www.oracle.com/technology/software/products/jdev/index.ht
ml
Memory Model for Dedicated Mode Sessions
In Oracle Database 10g, Oracle JVM has a new memory model for sessions that
connect to the database through a dedicated server. The basic memory structures
associated with Oracle include:
■
System Global Area (SGA)
The SGA is a group of shared memory structures, known as SGA components,
that contain data and control information for one Oracle Database instance. The
SGA is shared by all server and background processes. Examples of data stored in
the SGA include cached data blocks and shared SQL areas.
■
Program Global Areas (PGA)
A PGA is a memory region that contains data and control information for a server
process. It is nonshared memory created by Oracle when a server process is
started. Access to the PGA is exclusive to the server process. There is one PGA for
each server process. Background processes also allocate their own PGAs. The total
PGA memory allocated for all background and server processes attached to an
Oracle instance is referred to as the aggregate PGA.
The simplest way to manage memory is to allow the database to automatically manage
and tune it for you. To do so, you set only a target memory size initialization
parameter (MEMORY_TARGET) and a maximum memory size initialization parameter
(MEMORY_MAX_TARGET), on most platforms. The database then tunes to the target
memory size, redistributing memory as needed between the SGA and aggregate PGA.
Because the target memory initialization parameter is dynamic, you can change the
target memory size at any time without restarting the database. The maximum
memory size serves as an upper limit so that you cannot accidentally set the target
memory size too high. Because certain SGA components either cannot easily shrink or
must remain at a minimum size, the database also prevents you from setting the target
memory size too low.
Introduction to Java in Oracle Database
1-21
Memory Model for Dedicated Mode Sessions
See Also:
Oracle Database Administrator's Guide
1-22 Oracle Database Java Developer’s Guide
2
Java Applications on Oracle Database
Oracle Database runs standard Java applications. However, the Java-integrated Oracle
Database environment is different from a typical Java development environment. This
chapter describes the basic differences for writing, installing, and deploying Java
applications within Oracle Database. This chapter contains the following sections:
■
Database Sessions Imposed on Java Applications
■
Execution Control of Java Applications
■
Java Code, Binaries, and Resources Storage
■
Preparing Java Class Methods for Execution
■
User Interfaces on the Server
■
Shortened Class Names
■
Class.forName() in Oracle Database
■
Managing Your Operating System Resources
■
Managing Your Applications Using JMX
■
Threading in Oracle Database
■
Shared Servers Considerations
Database Sessions Imposed on Java Applications
In the Java-integrated Oracle Database, your Java applications exist within the context
of a database session. Oracle JVM sessions are entirely analogous to traditional Oracle
sessions. Each Oracle JVM session maintains the state of the Java applications accessed
by the client across calls within the session.
Figure 2–1 illustrates how each Java client starts a database session as the environment
for running Java applications within the database. Each Java database session has a
separate garbage collector, session memory, and call memory.
Java Applications on Oracle Database 2-1
Database Sessions Imposed on Java Applications
Figure 2–1 Java Environment Within Each Database Session
database session 1
client 1
database session 2
client 2
database session 3
client 3
Each Java
database
session
JVM
session
memory
call
memory
Within the context of a session, the client performs the following:
1.
Connects to the database and opens a session.
2.
Runs Java within the database. This is referred to as a call.
3.
Continues to work within the session, performing as many calls as required.
4.
Ends the session.
Within a session, the client has its own Java environment. It appears to the client as if a
separate, individual JVM was started for each session, although the implementation is
more efficient than this seems to imply. Within a session, Oracle JVM manages the
scalability of applications. Every call from a single client is managed within its own
session, and calls from each client is handled separately. Oracle JVM maximizes
sharing read-only data between clients and emphasizes a minimum amount of
per-session incremental footprint, to maximize performance for multiple clients.
The underlying server environment hides the details associated with session, network,
state, and other shared resource management issues from the Java code. Variables
defined as static are local to the client. No client can access the static variables of
other clients, because the memory is not available across session boundaries. Because
each client runs the Java application calls within its own session, activities of each
client are separate from any other client. During a call, you can store objects in static
fields of different classes, which will be available in the next session. The entire state of
your Java program is private and exists for your entire session.
Oracle JVM manages the following within the session:
■
All the objects referenced by static Java variables, all the objects referred to by
these objects, and so on, till their transitive closure
■
Garbage collection for the client that created the session
■
Session memory for static variables and across call memory needs
2-2 Oracle Database Java Developer’s Guide
Java Code, Binaries, and Resources Storage
■
Call memory for variables that exist within a call
Execution Control of Java Applications
In the Java2 Platform, Standard Edition (J2SE) environment, you develop Java
applications with a main() method, which is called by the interpreter when the class
is run. The main() method is called when you enter the following command on the
command-line:
java classname
This command starts the Java interpreter and passes the desired class, that is, the class
specified by classname, to the Java interpreter. The interpreter loads the class and
starts running the application by calling main(). However, Java applications within
the database do not start by a call to the main() method.
After loading your Java application within the database, you can run it by calling any
static method within the loaded class. The class or methods must be published
before you can run them. In Oracle Database, the entry point for Java applications is
not assumed to be main(). Instead, when you run your Java application, you specify
a method name within the loaded class as your entry point.
For example, in a normal Java environment, you would start the Java object on the
server by running the following command:
java myprogram
where, myprogram is the name of a class that contains the main() method. In
myprogram, main() immediately calls mymethod() for processing incoming
information.
In Oracle Database, you load the myprogram.class file into the database and
publish mymethod() as an entry-point. Then, the client or trigger can invoke
mymethod() explicitly.
Java Code, Binaries, and Resources Storage
In the standard Java development environment, Java source code, binaries, and
resources are stored as files in a file system, as follows:
■
Source code files are saved as .java files.
■
Compiled Java binary files are saved as .class files.
■
Resources are any data files, such as .properties or .ser files, that are stored
in the file system hierarchy and are loaded and used at run time.
In addition, when you run a Java application, you specify the CLASSPATH, which is a
file or directory path in the file system that contains your .class files. Java also
provides a way to group these files into a single archive form, a ZIP or Java Archive
(JAR) file.
Both these concepts are different in Oracle Database environment.
Table 2–1 describes how Oracle Database handles Java classes and locates dependent
classes.
Java Applications on Oracle Database 2-3
Java Code, Binaries, and Resources Storage
Table 2–1
Description of Java Code and Classes
Java Code and Classes
Description
Storing Java code, binaries, In Oracle Database, source code, classes, and resources reside
and resources
within the database and are known as Java schema objects,
where a schema corresponds to a database user. There are three
types of Java schema objects: source, class, and resource. There
are no .java, .class, .sqlj, .properties, or .ser files on
the server. Instead, these files map to the appropriate Java
schema objects.
Locating Java classes
Instead of the CLASSPATH, you use a resolver to specify one or
more schemas to search for Java source, class, and resource
schema objects.
Java Classes Loaded in the Database
If you are not using the command-line interface, you must load Java files into the
database as schema objects, to make them available to Oracle JVM. As Figure 2–2
illustrates, the loadjava tool can call the Java compiler of Oracle JVM, which
compiles source files into standard class files.
"Using Command-Line Interface" on page 3-9
See Also:
Figure 2–2 shows that loadjava can set the values of options stored in a system
database table. Among other things, these options affect the processing of Java source
files.
Figure 2–2 Loading Java into Oracle Database
.java file
.class file
.jar file
loadjava
RDBMS
Schema
Java
Source
Java
Class
Java
Complier
Java
Class
Java
Resource
Options
Table
Each Java class is stored as a schema object. The name of the object is derived from the
fully qualified name of the class, which includes the names of containing packages.
For example, the full name of the class Handle is:
oracle.aurora.rdbms.Handle
In the Java schema object name, slashes replace periods, so the full name of the class
becomes:
oracle/aurora/rdbms/Handle
2-4 Oracle Database Java Developer’s Guide
Preparing Java Class Methods for Execution
Oracle Database accepts Java names up to 4000 characters long. However, the names
of Java schema objects cannot be longer than 30 characters. Therefore, if a schema
object name is longer than 30 characters, then the system generates a short name, or
alias, for the schema object. Otherwise, the fully qualified name, also called full name,
is used. You can specify the full name in any context that requires it. When needed,
name mapping is handled by Oracle Database.
"Shortened Class Names" on page 2-22 and "System
Classes" on page 1-19
See Also:
Preparing Java Class Methods for Execution
To ensure that your Java methods run, you must do the following:
1.
Decide when the Java source code is going to be compiled.
2.
Decide if you are going to use the default resolver or another resolver for locating
supporting Java classes within the database.
3.
Load the classes into the database. If you do not wish to use the default resolver
for your classes, then you should specify a separate resolver with the load
command.
4.
Publish your class or method.
This sections covers the following topics:
■
Compiling Java Classes
■
Resolving Class Dependencies
■
Loading Classes
■
Granting Execute Rights
■
Controlling the Current User
■
Checking Java Uploads
■
Publishing
■
Auditing
Compiling Java Classes
Compilation of the Java source code can be done in one of the following ways:
■
■
■
You can compile the source explicitly on a client system before loading it into the
database, through a Java compiler, such as javac.
You can ask the database to compile the source during the loading process, which
is managed by the loadjava tool.
You can force the compilation to occur dynamically at run time.
If you decide to compile through loadjava, then you can
specify the compiler options. Refer to "Specifying Compiler Options"
on page 2-6 for more information.
Note:
This section includes the following topics:
■
Compiling Source Through javac
Java Applications on Oracle Database 2-5
Preparing Java Class Methods for Execution
■
Compiling Source Through loadjava
■
Compiling Source at Run Time
■
Specifying Compiler Options
■
Recompiling Automatically
Compiling Source Through javac
You can compile Java source code with a conventional Java compiler, such as javac.
After compilation, you load the compiled binary into the database, rather than the
source itself. This is a better option, because it is normally easier to debug the Java
code on your own system, rather than debugging it on the database.
Compiling Source Through loadjava
When you specify the -resolve option with loadjava for a source file, the
following occurs:
1.
The source file is loaded as a source schema object.
2.
The source file is compiled.
3.
Class schema objects are created for each class defined in the compiled .java file.
4.
The compiled code is stored in the class schema objects.
Oracle Database writes all compilation errors to the log file of the loadjava tool as
well as the USER_ERRORS view.
Compiling Source at Run Time
When you load the Java source into the database without the -resolve option,
Oracle Database compiles the source automatically when the class is needed during
run time. The source file is loaded into a source schema object.
Oracle Database writes all compilation errors to the log file of the loadjava tool as
well as the USER_ERRORS view.
Specifying Compiler Options
You can specify the compiler options in the following ways:
■
■
Specify compiler options on the command line with loadjava. You can also
specify the encoding option with loadjava.
Specify persistent compiler options in the JAVA$OPTIONS table. The
JAVA$OPTIONS table exists for each schema. Every time you compile, the
compiler uses these options. However, any compiler options specified with the
loadjava command override the options defined in this table. You must create
this table yourself if you wish to specify compiler options in this manner.
See Also:
"Compiler Options Specified in a Database Table"
Default Compiler Options
When compiling a source schema object for which neither a JAVA$OPTIONS entry
exists nor a command-line value for any option is specified, the compiler assumes a
default value as follows:
■
encoding=System.getProperty("file.encoding");
■
online=true
2-6 Oracle Database Java Developer’s Guide
Preparing Java Class Methods for Execution
This option applies only to Java sources that contain SQLJ constructs.
■
debug=true
This option is equivalent to:
javac -g
Compiler Options on the Command Line
The encoding compiler option specified with loadjava identifies the encoding of
the .java file. This option overrides any matching value in the JAVA$OPTIONS table.
The values are identical to:
javac -encoding
This option is relevant only when loading a source file.
Compiler Options Specified in a Database Table
Each JAVA$OPTIONS entry contains the names of source schema objects to which an
option setting applies. You can use multiple rows to set the options differently for
different source schema objects.
You can set JAVA$OPTIONS entries by using the following procedures and functions,
which are defined in the database package DBMS_JAVA:
PROCEDURE set_compiler_option(name VARCHAR2, option VARCHAR2, value VARCHAR2);
FUNCTION get_compiler_option(name VARCHAR2, option VARCHAR2) RETURNS VARCHAR2;
PROCEDURE reset_compiler_option(name VARCHAR2, option VARCHAR2);
Table 2–2 describes the parameters for these methods.
Table 2–2
Definitions for the Name and Option Parameters
Parameter
Description
name
This is a Java package name, a fully qualified class name, or an
empty string. When the compiler searches the JAVA$OPTIONS
table for the options to use for compiling a Java source schema
object, it uses the row that has a value for name that most closely
matches the fully qualified class name of a schema object. A
name whose value is the empty string matches any schema
object name.
option
The option parameter is either online, encoding, or debug.
Initially, a schema does not have a JAVA$OPTIONS table. To create a JAVA$OPTIONS
table, use the java.set_compiler_option procedure from the DBMS_JAVA
package to set a value. The procedure will create the table, if it does not exist. Specify
parameters in single quotes. For example:
SQL> execute dbms_java.set_compiler_option('x.y', 'online', 'false');
Table 2–3 represents a hypothetical JAVA$OPTIONS database table. The pattern match
rule is to match as much of the schema name against the table entry as possible. The
schema name with a higher resolution for the pattern match is the entry that applies.
Because the table has no entry for the encoding option, the compiler uses the default
or the value specified on the command line. The online option shown in the table
matches schema object names as follows:
Java Applications on Oracle Database 2-7
Preparing Java Class Methods for Execution
■
■
■
The name a.b.c.d matches class and package names beginning with a.b.c.d.
The packages and classes are compiled with online=true.
The name a.b matches class and package names beginning with a.b. The name
a.b does not match a.b.c.d. The packages and classes are compiled with
online=false.
All other packages and classes match the empty string entry and are compiled
with online=true.
Table 2–3
Example JAVA$OPTIONS Table
Name
Option
Value
Match Examples
a.b.c.d
online
true
■
a.b.c.d
Matches the pattern exactly.
■
a.b.c.d.e
First part matches the pattern exactly.
No other rule matches the full
qualified name.
a.b
online
false
■
a.b
Matches the pattern exactly
■
a.b.c.x
First part matches the pattern exactly.
No other rule matches beyond this
rule.
Empty string
online
true
■
a.c
No pattern match with any defined
name. Defaults to the empty string
rule.
■
x.y
No pattern match with any defined
name. Defaults to the empty string
rule.
Recompiling Automatically
Oracle Database provides a dependency management and automatic build facility that
transparently recompiles source programs when you make changes to the source or
binary programs upon which they depend. Consider the following example:
public class A
{
B b;
public void assignB()
{
b = new B()
}
}
public class B
{
C c;
public void assignC()
{
c = new C()
}
}
public class C
2-8 Oracle Database Java Developer’s Guide
Preparing Java Class Methods for Execution
{
A a;
public void assignA()
{
a = new A()
}
}
The system tracks dependencies at a class level of granularity. In the preceding
example, you can see that classes A, B, and C depend on one another, because A holds
an instance of B, B holds an instance of C, and C holds an instance of A. If you change
the definition of class A by adding a new field to it, then the dependency mechanism in
Oracle Database flags classes B and C as invalid. Before you use any of these classes
again, Oracle Database attempts to resolve them and recompile, if necessary. Note that
classes can be recompiled only if the source file is present on the server.
The dependency system enables you to rely on Oracle Database to manage
dependencies between classes, to recompile, and to resolve automatically. You must
force compilation and resolution yourself only if you are developing and you want to
find problems early. The loadjava tool also provides the facilities for forcing
compilation and resolution if you do not want the dependency management facilities
to perform this for you.
Resolving Class Dependencies
Many Java classes contain references to other classes, which is the essence of reusing
code. A conventional JVM searches for .class, .zip, and .jar files within the
directories specified in CLASSPATH. In contrast, Oracle JVM searches database
schemas for class objects. In Oracle Database, because you load all Java classes into the
database, you may need to specify where to find the dependent classes for your Java
class within the database.
All classes loaded within the database are referred to as class schema objects and are
loaded within certain schemas. All predefined Java application programming
interfaces (APIs), such as java.lang.* , are loaded within the PUBLIC schema. If
your classes depend on other classes you have defined, then you will probably load
them all within your own schema. For example, if your schema is SCOTT, the database
resolver searches the SCOTT schema before searching the PUBLIC schema. The listing
of schemas to search is known as a resolver specification. Resolver specifications are
defined for each class. This is in contrast to a classic JVM, where CLASSPATH is global
to all classes.
When locating and resolving the interclass dependencies for classes, the resolver
marks each class as valid or invalid, depending on whether all interdependent classes
are located. If the class that you load contains a reference to a class that is not found
within the appropriate schemas, then the class is listed as invalid. Unsuccessful
resolution at run time produces a ClassNotFound exception. Also, run-time
resolution can fail for lack of database resources, if the tree of classes is very large.
As with the Java compiler, loadjava resolves references to
classes, but not to resources. Ensure that you correctly load the
resource files that your classes require.
Note:
For each interclass reference in a class, the resolver searches the schemas specified by
the resolver specification for a valid class schema object that satisfies the reference. If
all references are resolved, then the resolver marks the class valid. A class that has
Java Applications on Oracle Database 2-9
Preparing Java Class Methods for Execution
never been resolved, or has been resolved unsuccessfully, is marked invalid. A class
that depends on a schema object that becomes invalid is also marked invalid.
To make searching for dependent classes easier, Oracle Database provides a default
resolver and resolver specification that searches the definer’s schema first and then
searches the PUBLIC schema. This covers most of the classes loaded within the
database. However, if you are accessing classes within a schema other than your own
or PUBLIC, you must define your own resolver specification.
Classes can be resolved in the following ways:
■
Loading using the default resolver, which searches the definer's schema and
PUBLIC:
loadjava -resolve
■
Loading using your own resolver specification definition:
loadjava-resolve -resolver "((* SCOTT)(* OTHER)(* PUBLIC))"
In the preceding example, the resolver specification definition includes the SCOTT
schema, OTHER schema, and PUBLIC.
The -resolver option specifies the objects to search within the schemas defined. In
the preceding example, all class schema objects are searched within SCOTT, OTHER,
and PUBLIC. However, if you want to search for only a certain class or group of
classes within the schema, then you could narrow the scope for the search. For
example, to search only for the my/gui/* classes within the OTHER schema, you
would define the resolver specification as follows:
loadjava -resolve -resolver '((* SCOTT) ("my/gui/*" OTHER) (* PUBLIC))’
The first parameter within the resolver specification is for the class schema object, and
the second parameter defines the schema within which to search for these class
schema objects.
Allowing References to Nonexistent Classes
You can specify a special option within a resolver specification that allows an
unresolved reference to a nonexistent class. Sometimes, internal classes are never used
within a product. In a normal Java environment, this is not a problem, because as long
as the methods are not called, JVM ignores them. However, Oracle Database resolver
tries to resolve all classes referenced within the JAR file, including the unused classes.
If the reference cannot be validated, then the classes within the JAR file are marked as
invalid.
To ignore references, you can specify the wildcard, minus sign (-), within the resolver
specification. The following example specifies that any references to classes within
my/gui are to be allowed, even if it is not present within the resolver specification
schema list.
loadjava -resolve -resolver '((* SCOTT) (* PUBLIC) ("my/gui/*" -))'
Without the wildcard, if a dependent class is not found within one of the schemas,
your class is listed as invalid and cannot be run.
In addition, you can define that all classes not found are to be ignored. However, this
is dangerous, because a class that has a dependent class will be marked as valid, even
if the dependent class does not exist. However, the class can never run without the
dependent class. In this case, you will receive an exception at run time.
2-10 Oracle Database Java Developer’s Guide
Preparing Java Class Methods for Execution
To ignore all classes not found within SCOTT or PUBLIC, specify the following
resolver specification:
loadjava -resolve -resolver "((* SCOTT) (* PUBLIC) (* -))"
If you later intend to load the nonexistent classes that required you to use such a
resolver, then you should not use a resolver containing the minus sign (-) wildcard.
Instead, include all referenced classes in the schema before resolving.
An alternative mechanism for dealing with nonexistent classes
is using the -gemissing option of loadjava. This option causes
loadjava to create and load definitions of classes that are referenced,
but not defined.
Note:
Bytecode Verifier
According to JVM specification, .class files are subject to verification before the class
they define is available in a JVM. In Oracle JVM, the verification process occurs at class
resolution.
Table 2–4 describes the problems the resolver may find and the appropriate Oracle
error code issued.
Table 2–4
ORA Errors
Error Code
Description
ORA-29545
If the resolver determines that the class is malformed, then the
resolver does not mark it valid. When the resolver rejects a class,
it issues an ORA-29545 error. The loadjava tool reports the
error. For example, this error is thrown if the contents of a
.class file are not the result of a Java compilation or if the file
has been corrupted.
ORA-29552
In some situations, the resolver allows a class to be marked
valid, but will replace bytecodes in the class to throw an
exception at run time. In these cases, the resolver issues an
ORA-29552 warning that loadjava reports. The loadjava
tool issues this warning when the Java Language Specification
(JLS) requires an IncompatibleClassChangeError to be
thrown. Oracle JVM relies on the resolver to detect these
situations, supporting the proper run-time behavior that the JLS
requires.
A resolver with the minus sign (-) wildcard marks your class valid, regardless of
whether classes referenced by your class are present. Because of inheritance and
interfaces, you may want to write valid Java methods that use an instance of a class as
if it were an instance of a superclass or of a specific interface. When the method being
verified uses a reference to class A as if it were a reference to class B, the resolver must
check that A either extends or implements B. For example, consider the following
potentially valid method, whose signature implies a return of an instance of B, but
whose body returns an instance of A:
B myMethod(A a)
{
return a;
}
The method is valid only if A extends B or A implements the interface B. If A or B have
been resolved using the minus sign (-) wildcard, then the resolver does not know that
Java Applications on Oracle Database
2-11
Preparing Java Class Methods for Execution
this method is safe. In this case, the resolver replaces the bytecodes of myMethod with
bytecodes that throw an exception if myMethod is called.
A resolver without the minus sign (-) wildcard ensures that the class definitions of A
and B are found and resolved properly if they are present in the schemas they
specifically identify. The only time you may consider using the alternative resolver is
if you must load an existing JAR file containing classes that reference other nonsystem
classes, which are not included in the JAR file.
See Also: Chapter 11, "Schema Objects and Oracle JVM Utilities" for
more information about class resolution and loading your classes
within the database.
Loading Classes
This section gives an overview of loading your classes into the database using the
loadjava tool. You can also run loadjava from within SQL commands.
Note: You do not have to load the classes to the database as schema
objects if you use the command-line interface. For more information
about command-line interface, refer to "Using Command-Line
Interface" on page 9.
See Also:
Chapter 11, "Schema Objects and Oracle JVM Utilities"
Unlike a conventional JVM, which compiles and loads from files, Oracle JVM compiles
and loads from database schema objects.
Table 2–5 describes database schema objects that correspond to the files used by a
conventional JVM.
Table 2–5
Description of Java Files
Java File Types
Description
.java source files or .sqlj source files
correspond to Java source schema objects
.class compiled Java files
correspond to Java class schema objects
.properties Java resource files, .ser SQLJ
profile files, or data files
correspond to Java resource schema objects
You must load all classes or resources into the database to be used by other classes
within the database. In addition, at load time, you define who can run your classes
within the database.
Table 2–6 describes the activities the loadjava tool performs for each type of file.
2-12 Oracle Database Java Developer’s Guide
Preparing Java Class Methods for Execution
Table 2–6
loadjava Operations on Schema Objects
Schema Object
loadjava Operations on Objects
.java source files
1.
Creates a Java source schema object in the definer's schema
unless another schema is specified.
2.
Loads the contents of the source file into a schema object.
3.
Creates a class schema object for all classes defined in the
source file.
4.
If -resolve is requested, compiles the source schema
object and resolves the class and its dependencies. It then
stores the compiled class into a class schema object.
1.
Creates a source schema object in the definer's schema
unless another schema is specified.
2.
Loads contents of the source file into the schema object.
3.
Creates a class schema object for all classes and resources
defined in the source file.
4.
If -resolve is requested, translates and compiles the
source schema object and stores the compiled class into a
class schema object. It then stores the profile into a .ser
resource schema object and customizes it.
1.
Creates a class schema object in the definer's schema unless
another schema is specified.
2.
Loads the class file into the schema object.
3.
Resolves and verifies the class and its dependencies if
-resolve is specified.
1.
Creates a resource schema object in the definer's schema
unless another schema is specified.
2.
Loads a resource file into a schema object.
1.
Creates a resource schema object in the definer's schema
unless another schema is specified.
2.
Loads the .ser resource file into a schema object and
customizes it.
.sqlj source files
.class compiled Java files
.properties Java
resource files
.ser SQLJ profile
The dropjava tool performs the reverse of loadjava. It deletes schema objects that
correspond to Java files. Always use dropjava to delete a Java schema object created
with loadjava. Dropping with SQL data definition language (DDL) commands will
not update the auxiliary data maintained by loadjava and dropjava. You can also
run the dropjava tool from within SQL commands.
After loading the classes and resources, you can access the USER_OBJECTS view in
your database schema to verify whether your classes and resources have been loaded
properly.
Sharing of Metadata for User Classloaded Classes
Classes loaded by the built-in mechanism for loading database resident classes are
known as system classloaded, whereas those loaded by other means are called user
classloaded. When you load a class into the database, a representation of the class is
created in memory, part of which is referred to here as the class metadata. The class
metadata is the same for any session using the class and is potentially sharable. Earlier,
such sharing was available only for system classloaded classes. From 11g release 1
(11.1), you can also share class metadata of user classloaded classes, at the discretion of
the system administrator.
Java Applications on Oracle Database
2-13
Preparing Java Class Methods for Execution
See Also: Appendix B, "Classpath Extensions and User Classloaded
Metadata"
Defining the Same Class Twice
You cannot have two class objects with the same name in the same schema. This rule
affects you in two ways:
An exception to this rule is when you use the
-prependjarnames option for database resident JARs. If you use
this option, then you can have two classes with the same class name in
the same schema. For more information about database resident JARs,
see "Database Resident JARs" on page 2-15.
Note:
■
You can load either a particular Java .class file or its .java file, but not both.
Oracle Database tracks whether you loaded a class file or a source file. If you want
to update the class, then you must load the same type of file that you originally
loaded. If you want to update the other type, then you must drop the first before
loading the second. For example, if you loaded x.java as the source for class y,
then to load x.class, you must first drop x.java.
■
You cannot define the same class within two different schema objects in the same
schema. For example, suppose x.java defines class y and you want to move the
definition of y to z.java. If x.java has already been loaded, then loadjava
rejects any attempt to load z.java, which also defines y. Instead, do either of the
following:
■
■
Drop x.java, load z.java, which defines y, and then load the new x.java,
which does not define y.
Load the new x.java, which does not define y, and then load z.java, which
defines y.
See Also:
"System Classes" on page 1-19
Designating Database Privileges and JVM Permissions
You must have the following SQL database privileges to load classes:
■
■
■
CREATE PROCEDURE and CREATE TABLE privileges to load into your schema.
CREATE ANY PROCEDURE and CREATE ANY TABLE privileges to load into
another schema.
oracle.aurora.security.JServerPermission.loadLibraryInClass.
classname.
See Also:
"Permission for Loading Classes" on page 10-18
Loading JAR or ZIP Files
The loadjava tool accepts .class, .java, .properties, .sqlj, .ser, .jar, or
.zip files. The JAR or ZIP files can contain source, class, and data files. When you
pass a JAR or ZIP file to loadjava, it opens the archive and loads the members of the
archive individually. There is no JAR or ZIP schema object. If the JAR or ZIP content
has not changed since the last time it was loaded, then it is not reloaded. Therefore,
there is little performance penalty for loading JAR or ZIP files. In fact, loading JAR or
ZIP files is the simplest way to use loadjava.
2-14 Oracle Database Java Developer’s Guide
Preparing Java Class Methods for Execution
Oracle Database does not reload a class if it has not changed
since the last load. However, you can force a class to be reloaded
using the -force option.
Note:
Database Resident JARs
Starting with 11g release 1 (11.1), when you load the contents of a JAR into the
database, you have the option of creating a database object representing the JAR itself.
In this way, you can retain an association between this JAR object and the class,
resource, and source objects loaded from the JAR. This enables you to:
■
■
Use signed JARs and JAR namespace segregation in the same way as you use
them in standard JVM.
Manage the classes that you have derived from a JAR while loading it into the
database as a single unit. This helps you to prevent individual redefinition of the
classes loaded from the JAR. It also enables you to drop the whole set of classes
loaded from the JAR, irrespective of the contents or the continued existence of the
JAR on the external file system, at the time of dropping it.
In order to load a JAR into the database, you have the following loadjava options:
■
-jarsasdbobjects
■
-prependjarnames
For more information regarding loadjava options, refer to "The loadjava Tool"
section on page 11-6.
Granting Execute Rights
If you load all classes within your own schema and do not reference any class outside
your schema, then you already have rights to run the classes. You have the privileges
necessary for your objects to call other objects loaded in the same schema. That is, the
ability for class A to call class B. Class A must be given the right to call class B.
The classes that define a Java application are stored within Oracle Database under the
SQL schema of their owner. By default, classes that reside in one user's schema cannot
be run by other users, because of security concerns. You can provide other users the
right to run your class in the following ways:
■
Using the loadjava -grant option
See Also:
■
"The loadjava Tool" on page 11-6
Using the following command:
SQL> grant execute on myclass to scott;
where, myclass is the name of the underlying Java class.
If the classname is over 30 characters in length, then you need to change it to the
shortened name found by the following command:
SQL> select dbms_java.shortname('long classname') from dual;
You can grant rights to run your classes to a certain user or schema, but you cannot
grant rights to a role, which includes the superuser DBA role. The setting of rights to
run classes is the same as used to grant or revoke privileges in SQL DDL statements.
Java Applications on Oracle Database
2-15
Preparing Java Class Methods for Execution
Prior to Oracle Database 11g release 1 (11.1), granting execute
right to a stored procedure would mean granting execute right to both
the stored procedure and the Java class referred by the stored
procedure. In Oracle Database 11g release, if you want to grant
execute right on the underlying Java class as well, then you need to
grant execute right on the class explicitly. This is implemented for
better security.
Note:
Figure 2–3 illustrates the rights required to run classes.
Figure 2–3 Rights to Run Classes
Class A
Class B
Class C
Method invocation: Class A invokes Class B; Class B invokes Class C.
Execution rights for classes:
– Class A needs execution rights for B.
– Class A does not need execution rights for C.
– Class B needs execution rights for C.
See Also: Chapter 9, "Oracle Database Java Application
Performance" for information about JVM security permissions
Controlling the Current User
During the execution of PL/SQL code, there is always a current user. The same
concept is used for the execution of Java code. Initially, the current user is the user,
who creates the session that invokes the Java code. A Java method is called from SQL
or PL/SQL through a corresponding wrapper. Java wrappers are special PL/SQL
entities, which expose Java methods to SQL and PL/SQL as PL/SQL stored
procedures or functions. Such a wrapper might change the current effective user. The
wrappers that change the current effective user to the owner of the wrapper are called
definer's rights wrappers. If a wrapper does not change the current effective user, then
the effective user remains unchanged.
By default, Java wrappers are definer's rights wrappers. If you want to override this,
then create the wrapper using the AUTHID CURRENT_USER option.
See Also: "Writing Top-Level Call Specifications" on page 6-6 for
more information about the AUTHID CURRENT_USER option
At any time during the execution of Java code, a Java call stack is maintained. The
stack contains frames corresponding to Java methods entered, with the innermost
frame corresponding to the currently executing method. By default, Java methods
execute on the stack without changing the current user, that is, with the privileges of
their current effective invoker, not their definer.
You can load a Java class to the database with the loadjava -definer option. Any
method of a class having the definer attribute marked, becomes a definer's rights
method. When such a method is entered, a special kind of frame called a definer's
frame is created onto the Java stack. This frame switches the current effective user to
the owner (definer) of such a class. A new user ID remains effective for all inner
frames until either the definer's frame is popped off the stack or a nested definer's
frame is entered.
2-16 Oracle Database Java Developer’s Guide
Preparing Java Class Methods for Execution
Thus, at any given time during the execution of a Java method that is called from SQL
or PL/SQL through its wrapper, the effective user is one of the following:
■
■
The innermost definer's frame on the Java stack
Either the owner of the PL/SQL wrapper of the topmost Java method, if it is
definer's rights, or the user who called the wrapper.
Consider a company that uses a definer’s rights procedure to analyze sales. To provide
local sales statistics, the procedure analyze must access sales tables that reside at
each regional site. To do this, the procedure must also reside at each regional site. This
causes a maintenance problem. To solve the problem, the company installs an
invoker’s rights version of the procedure analyze at headquarters.
Figure 2–4 shows how all regional sites can use the same procedure to query their own
sales tables.
Figure 2–4 Invoker’s rights Solution
Schema WEST
Schema HQ
Schema EAST
analyze
(IR)
Sales
Sales
Occasionally, you may want to override the default invoker’s rights behavior. Suppose
headquarters wants the analyze procedure to calculate sales commissions and
update a central payroll table. This presents a problem, because invokers of
analyze should not have direct access to the payroll table, which stores employee
salaries and other sensitive data.
Figure 2–5 illustrates the solution, where the analyze procedure call the definer’s
rights procedure, calcComm, which in turn updates the payroll table.
Figure 2–5 Indirect Access
Schema WEST
Schema HQ
Schema EAST
analyze
(IR)
calc_comm
(DR)
Sales
Sales
payroll
Checking Java Uploads
You can query the USER_OBJECTS database view to obtain information about schema
objects that you own, including Java sources, classes, and resources. This enables you,
Java Applications on Oracle Database
2-17
Preparing Java Class Methods for Execution
for example, to verify whether sources, classes, or resources that you load are properly
stored in schema objects.
Table 2–7 lists the key columns in USER_OBJECTS and their description.
Table 2–7
Key USER_OBJECT Columns
Name
Description
OBJECT_NAME
Name of the object
OBJECT_TYPE
Type of the object, such as JAVA SOURCE, JAVA CLASS, or
JAVA RESOURCE.
STATUS
Status of the object. The values can be either VALID or INVALID.
It is always VALID for JAVA RESOURCE.
Object Name and Type
An OBJECT_NAME in USER_OBJECTS is the alias. The fully qualified name is stored as
an alias if it exceeds 30 characters.
See Also: "Shortened Class Names" on page 2-22 for information
about fully qualified names and aliases.
If the server uses an alias for a schema object, then you can use the LONGNAME()
function of the DBMS_JAVA package to receive it from a query as a fully qualified
name, without having to know the alias or the conversion rules.
SQL> SELECT dbms_java.longname(object_name) FROM user_objects WHERE
object_type='JAVA SOURCE';
This statement displays the fully qualified name of the Java source schema objects.
Where no alias is used, no conversion occurs.
Note:
SQL and PL/SQL are not case-sensitive.
You can use the SHORTNAME() function of the DBMS_JAVA package to use a fully
qualified name as a query criterion, without having to know whether it was converted
to an alias in the database.
SQL*Plus> SELECT object_type FROM user_objects WHERE
object_name=dbms_java.shortname('known_fullname ');
This statement displays the OBJECT_TYPE of the schema object with the specified
fully qualified name. This presumes that the fully qualified name is representable in
the database character set.
SQL> select * from javasnm;
SHORT LONGNAME
---------------------------------------------------------------------/78e6d350_BinaryExceptionHandl sun/tools/java/BinaryExceptionHandler
/b6c774bb_ClassDeclaration sun/tools/java/ClassDeclaration
/af5a8ef3_JarVerifierStream1 sun/tools/jar/JarVerifierStream$1
Status
STATUS is a character string that indicates the validity of a Java schema object. A Java
source schema object is VALID if it compiled successfully, and a Java class schema
2-18 Oracle Database Java Developer’s Guide
Preparing Java Class Methods for Execution
object is VALID if it was resolved successfully. A Java resource schema object is always
VALID, because resources are not resolved.
Example: Accessing USER_OBJECTS
The following SQL*Plus script accesses the USER_OBJECTS view to display
information about uploaded Java sources, classes, and resources:
COL object_name format a30
COL object_type format a15
SELECT object_name, object_type, status
FROM user_objects
WHERE object_type IN ('JAVA SOURCE', 'JAVA CLASS', 'JAVA RESOURCE')
ORDER BY object_type, object_name;
You can optionally use wildcards in querying USER_OBJECTS, as in the following
example:
SELECT object_name, object_type, status
FROM user_objects
WHERE object_name LIKE '%Alerter';
The preceding statement finds any OBJECT_NAME entries that end with the characters
Alerter.
Publishing
Oracle Database enables clients and SQL to call Java methods that are loaded in the
database after they are published. You publish either the object itself or individual
methods. If you write a Java stored procedure that you intend to call with a trigger,
directly or indirectly in SQL data manipulation language (DML) or in PL/SQL, then
you must publish individual methods in the class. Using a call specification, specify
how to access the method. Java programs consist of many methods in many classes.
However, only a few static methods are typically exposed with call specifications.
See Also: Chapter 6, "Publishing Java Classes With Call
Specifications"
Auditing
In releases prior to Oracle Database 10g release 2 (10.2), Java classes in the database
cannot be audited directly. However, you can audit the PL/SQL wrapper. Typically,
all Java stored procedures are started from some wrappers. Therefore, all Java stored
procedures can be audited, though not directly.
In Oracle Database 10g release 2 (10.2), you can audit DDL statements for creating,
altering, or dropping Java source, class, and resource schema objects, as with any other
DDL statement. Oracle Database 10g release 2 (10.2) provides auditing options for
auditing Java activities easily and directly. You can also audit any modification of Java
sources, classes, and resources.
You can audit database activities related to Java schema objects at two different levels,
statement level and object level. At the statement level you can audit all activities
related to a special pattern of statements.
Table 2–8 lists the statement auditing options and the corresponding SQL statements
related to Java schema objects.
Java Applications on Oracle Database
2-19
User Interfaces on the Server
Table 2–8
Statement Auditing Options Related to Java Schema Objects
Statement Option
SQL Statements
CREATE JAVA SOURCE
CREATE JAVA SOURCE
CREATE OR REPLACE JAVA SOURCE
ALTER JAVA SOURCE
ALTER JAVA SOURCE
DROP JAVA SOURCE
DROP JAVA SOURCE
CREATE JAVA CLASS
CREATE JAVA CLASS
CREATE OR REPLACE JAVA CLASS
ALTER JAVA CLASS
ALTER JAVA CLASS
DROP JAVA CLASS
DROP JAVA CLASS
CREATE JAVA RESOURCE
CREATE JAVA RESOURCE
CREATE OR REPLACE JAVA RESOURCE
ALTER JAVA RESOURCE
ALTER JAVA RESOURCE
DROP JAVA RESOURCE
DROP JAVA RESOURCE
For example, if you want to audit the ALTER JAVA SOURCE DDL statement, then
enter the following statement at the SQL prompt:
AUDIT ALTER JAVA SOURCE
Object level auditing provides finer granularity. It enables you to identify specific
problems by zooming into specific objects.
Table 2–9 lists the object auditing options for each Java schema object. The entry X in a
cell indicates that the corresponding SQL command can be audited for that Java
schema object. The entry NA indicates that the corresponding SQL command is not
applicable for that Java schema object.
Table 2–9
Object Auditing Options Related to Java Schema Options
Object Option
Java Source
Java Resource
Java Class
ALTER
X
NA
X
EXECUTE
NA
NA
X
AUDIT
X
X
X
GRANT
X
X
X
See Also:
■
Oracle Database Security Guide
■
Oracle Database SQL Language Reference
User Interfaces on the Server
Oracle Database furnishes all core Java class libraries on the server, including those
associated with presentation of the user interfaces. However, it is inappropriate for
code running on the server to attempt to materialize or display a user interface on the
server. Users running applications in Oracle JVM environment should not be expected
nor allowed to interact with or depend on the display and input hardware of the
server where Oracle Database is running.
2-20 Oracle Database Java Developer’s Guide
Shortened Class Names
To address compatibility issues on platforms that do not support display, keyboard, or
mouse, Java 1.4 outlines Headless Abstract Window Toolkit (AWT) support. The
Headless AWT API introduces a new public run-time exception class,
java.awt.HeadlessException. The constructors of the Applet class, all
heavy-weight components, and many of the methods in the Toolkit and
GraphicsEnvironment classes, which rely on the native display devices, are
changed to throw HeadlessException if the platform does not support a display. In
Oracle Database, user interfaces are supported only on client applications.
Accordingly, Oracle JVM is a Headless Platform and throws HeadlessException if
these methods are called.
Most AWT computation that does not involve accessing the underlying native display
or input devices is allowed in Headless AWT. In fact, Headless AWT is quite powerful
as it provides programmers access to fonts, imaging, printing, and color and ICC
manipulation. For example, applications running in Oracle JVM can parse,
manipulate, and write out images as long as they do not try to physically display it on
the server. The Sun Microsystems reference JVM implementation can be started in the
Headless mode, by supplying the -Djava.awt.headless=true property, and run
with the same Headless AWT restrictions as Oracle JVM does. Oracle JVM fully
complies with the Java Compatibility Kit (JCK) with respect to Headless AWT.
See Also:
http://java.sun.com/j2se/1.4/docs/guide/awt/AWTChang
es.html#headless
Oracle JVM takes a similar approach for sound support. Applications in Oracle JVM
are not allowed to access the underlying sound system for purposes of sound playback
or recording. Instead, the system sound resources appear to be unavailable in a
manner consistent with the sound API specification of the methods that are trying to
access the resources. For example, methods in javax.sound.midi.MidiSystem
that attempt to access the underlying system sound resources throw the
MidiUnavailableException checked exception to signal that the system is
unavailable. However, similar to the Headless AWT support, Oracle Database
supports the APIs that allow sound file manipulation, free of the native sound devices.
Oracle JVM also fully complies with the JCK, when it implements the sound API.
Shortened Class Names
Each Java source, class, and resource is stored in its own schema object in the server.
The name of the schema object is derived from the fully qualified name, which
includes relevant path or package information. Dots are replaced by slashes.
Schema object names, however, have a maximum of only 30 characters, and all
characters must be legal and convertible to characters in the database character set. If
any fully qualified name is longer than 30 characters or contains illegal or
nonconvertible characters, then Oracle Database converts it to a short name, or alias, to
use as the name of the schema object. Oracle Database keeps track of both the names
and how to convert between them. If the fully qualified name is 30 characters or less
and has no illegal or inconvertible characters, then it is used as the schema object
name.
Because Java classes and methods can have names exceeding the maximum SQL
identifier length, Oracle Database uses abbreviated names internally for SQL access.
Oracle Database provides the LONGNAME() function within the DBMS_JAVA package
for retrieving the original Java class name for any truncated name.
FUNCTION longname (shortname VARCHAR2) RETURN VARCHAR2
Java Applications on Oracle Database
2-21
Class.forName() in Oracle Database
This function returns the fully qualified name of the Java schema object, which is
specified using its alias. The following is an example of a statement used to display the
fully qualified name of classes that are invalid:
SELECT dbms_java.longname (object_name) FROM user_objects WHERE object_type =
'JAVA CLASS' and status = 'INVALID';
You can also specify a full name to the database by using the SHORTNAME() function
of the DBMS_JAVA package. The function takes a full name as input and returns the
corresponding short name. This function is useful for verifying whether the classes are
loaded successfully, by querying the USER_OBJECTS view.
FUNCTION shortname (longname VARCHAR2) RETURN VARCHAR2
See Also:
"System Classes" on page 1-19
Class.forName() in Oracle Database
The JLS provides the following description of Class.forName():
Given the fully qualified name of a class, this method attempts to locate, load, and link
the class. If it succeeds, then a reference to the Class object for the class is returned. If
it fails, then an instance of ClassNotFoundException is thrown.
Class lookup is always on behalf of a referencing class and is done through an instance
of ClassLoader. The difference between the Java Development Kit (JDK)
implementation and Oracle JVM implementation is the method in which the class is
found:
■
■
The JDK uses one instance of ClassLoader that searches the set of directory tree
roots specified by the CLASSPATH environment variable.
Oracle JVM defines several resolvers that specify how to locate classes. Every class
has a resolver associated with it, and each class can, potentially, have a different
resolver. When you run a method that calls Class.forName(), the resolver of
the currently running class, which is this, is used to locate the class.
See Also:
"Resolving Class Dependencies" on page 2-9
You can receive unexpected results if you try to locate a class with an incorrect
resolver. For example, if a class X in schema X requests a class Y in schema Y to look up
class Z, you will experience an error if you expected the resolver of class X to be used.
Because class Y is performing the lookup, the resolver associated with class Y is used
to locate class Z. In summary, if the class exists in another schema and you specified
different resolvers for different classes, as would happen by default if they are in
different schemas, you may not find the class.
You can solve this resolver problem as follows:
■
Avoid any class name lookup by passing the Class object itself.
■
Supply the ClassLoader instance in the Class.forName() method.
■
Supply the class and the schema it resides in to the classForNameAndSchema()
method.
■
Supply the schema and class name to ClassForName.lookupClass().
■
Serialize your objects with the schema name and the class name.
2-22 Oracle Database Java Developer’s Guide
Class.forName() in Oracle Database
Another unexpected behavior can occur if system classes
invoke Class.forName(). The desired class is found only if it
resides in SYS or in PUBLIC. If your class does not exist in either SYS
or PUBLIC, then you can declare a PUBLIC synonym for the class.
Note:
This section covers the following topics:
■
Supply ClassLoader in Class.forName()
■
Supply Class and Schema Names to classForNameAndSchema()
■
Supply Class and Schema Names to lookupClass()
■
Supply Class and Schema Names when Serializing
■
Class.forName Example
Supply ClassLoader in Class.forName()
Oracle Database uses resolvers for locating classes within schemas. Every class has a
specified resolver associated with it, and each class can have a different resolver
associated with it. As a result, the locating of classes is dependent on the definition of
the associated resolver. The ClassLoader instance knows which resolver to use,
based on the class that is specified. When you supply a ClassLoader instance to
Class.forName(), your class is looked up in the schemas defined in the resolver of
the class. The syntax of this variant of Class.forName() is as follows:
Class forName (String name, boolean initialize, ClassLoader loader);
The following examples show how to supply the class loader of either the current class
instance or the calling class instance.
Example 2–1 Retrieve Resolver from Current Class
You can retrieve the class loader of any instance by using the
Class.getClassLoader() method. The following example retrieves the class
loader of the class represented by instance x:
Class c1 = Class.forName (x.whatClass(), true, x.getClass().getClassLoader());
Example 2–2 Retrieve Resolver from Calling Class
You can retrieve the class of the instance that called the running method by using the
oracle.aurora.vm.OracleRuntime.getCallerClass() method. After you
retrieve the class, call the Class.getClassLoader() method on the returned class.
The following example retrieves the class of the instance that called the
workForCaller() method. Then, its class loader is retrieved and supplied to the
Class.forName() method. As a result, the resolver used for looking up the class is
the resolver of the calling class.
void workForCaller()
{
ClassLoader c1=oracle.aurora.vm.OracleRuntime.getCallerClass().getClassLoader();
...
Class c=Class.forName(name, true, c1);
...
}
Java Applications on Oracle Database
2-23
Class.forName() in Oracle Database
Supply Class and Schema Names to classForNameAndSchema()
You can resolve the problem of where to find the class by supplying the resolver,
which can identify the schemas to be searched. Alternatively, you can supply the
schema in which the class is loaded. If you know in which schema the class is loaded,
then you can use the classForNameAndSchema() method, which is in the
DbmsJava class provided by Oracle Database. This method takes both the name of the
class and the schema in which the class resides and locates the class within the
designated schema.
Example 2–3 Providing Schema and Class Names
The following example shows how you can save the schema and class names using the
save() method. Both names are retrieved, and the class is located using the
DbmsJava.classForNameAndSchema() method.
import oracle.aurora.rdbms.ClassHandle;
import oracle.aurora.rdbms.Schema;
import oracle.aurora.rdbms.DbmsJava;
void save (Class c1)
{
ClassHandle handle = ClassHandle.lookup(c1);
Schema schema = handle.schema();
writeName (schema.getName());
writeName (c1.getName());
}
Class restore()
{
String schemaName = readName();
String className = readName();
return DbmsJava.classForNameAndSchema (schemaName, className);
}
Supply Class and Schema Names to lookupClass()
You can supply a String value containing both the schema and class names to the
oracle.aurora.util.ClassForName.lookupClass() method. When called,
this method locates the class in the specified schema. The string must be in the
following format:
"<schema>:<class>"
For example, to locate com.package.myclass in the SCOTT schema, use the
following:
oracle.aurora.util.ClassForName.lookupClass("SCOTT:com.package.myclass");
Note: Use uppercase characters for the schema name. In this case,
the schema name is case-sensitive.
Supply Class and Schema Names when Serializing
When you deserialize a class, part of the operation is to lookup a class based on a
name. To ensure that the lookup is successful, the serialized object must contain both
the class and schema names.
2-24 Oracle Database Java Developer’s Guide
Class.forName() in Oracle Database
Oracle Database provides the following classes for serializing and deserializing
objects:
■
oracle.aurora.rdbms.DbmsObjectOutputStream
This class extends java.io.ObjectOutputStream and adds schema names in
the appropriate places.
■
oracle.aurora.rdbms.DbmsObjectInputStream
This class extends java.io.ObjectInputStream and reads streams written by
DbmsObjectOutputStream. You can use this class in any environment. If used
within Oracle Database, then the schema names are read out and used when
performing the class lookup. If used on a client, then the schema names are
ignored.
Class.forName Example
The following example shows several methods for looking up a class:
import oracle.aurora.vm.OracleRuntime;
import oracle.aurora.rdbms.Schema;
import oracle.aurora.rdbms.DbmsJava;
public class ForName
{
private Class from;
/* Supply an explicit class to the constructor */
public ForName(Class from)
{
this.from = from;
}
/* Use the class of the code containing the "new ForName()" */
public ForName()
{
from = OracleRuntime.getCallerClass();
}
/* lookup relative to Class supplied to constructor */
public Class lookupWithClassLoader(String name) throws ClassNotFoundException
{
/* A ClassLoader uses the resolver associated with the class*/
return Class.forName(name, true, from.getClassLoader());
}
/* In case the schema containing the class is known */
static Class lookupWithSchema(String name, String schema)
{
Schema s = Schema.lookup(schema);
return DbmsJava.classForNameAndSchema(name, s);
}
}
The preceding example uses the following methods for locating a class:
■
To use the resolver of the class of an instance, call lookupWithClassLoader().
This method supplies a class loader to the Class.forName() method in the
from variable. The class loader specified in the from variable defaults to this
class.
Java Applications on Oracle Database
2-25
Managing Your Operating System Resources
■
■
■
To use the resolver from a specific class, call ForName() with the designated class
name, followed by lookupWithClassLoader(). The ForName() method sets
the from variable to the specified class. The lookupWithClassLoader()
method uses the class loader from the specified class.
To use the resolver from the calling class, first call the ForName() method
without any parameters. It sets the from variable to the calling class. Then, call the
lookupWithClassLoader() method to locate the class using the resolver of the
calling class.
To lookup a class in a specified schema, call the lookupWithSchema() method.
This provides the class and schema name to the classForNameAndSchema()
method.
Managing Your Operating System Resources
Operating system resources are a limited commodity on any computer. Because Java is
targeted at providing a computing platform as well as a programming language, it
contains platform-independent classes and frameworks for accessing platform-specific
resources. The Java class methods access operating system resources through JVM.
Java has potential problems with this model, because programmers rely on the
garbage collector to manage all resources, when all that the garbage collector manages
is Java objects and not the operating system resources that the Java objects hold on to.
In addition, when you use shared servers, your operating system resources, which are
contained within Java objects, can be invalidated if they are maintained across calls
within a session.
See Also: "Operating System Resources Affected Across Calls" on
page 2-39
The following sections discuss these potential problems:
■
Overview of Operating System Resources
■
Garbage Collection and Operating System Resources
Overview of Operating System Resources
In general, your operating system resources contain the following:
Operating System
Resources
memory
Description
Oracle Database manages memory internally, allocating memory as you create objects and
freeing objects as you no longer need them. The language and class libraries do not
support a direct means to allocate and free memory.
See Also: "Automated Storage Management With Garbage Collection" on page 1-10.
files and sockets
Java contains classes that represent file or socket resources. Instances of these classes hold
on to the file or socket constructs, such as file handles, of the operating system.
threads
Oracle JVM threads provide no additional scalability over what is provided by the
database support of multiple concurrently executing sessions. However, Oracle JVM
supports the full Java threading API.
See Also: "Threading in Oracle Database" on page 2-32.
2-26 Oracle Database Java Developer’s Guide
Managing Your Operating System Resources
Operating System Resource Access
By default, a Java user does not have direct access to most operating system resources.
A system administrator can give permissions to a user to access these resources by
modifying JVM security restrictions. JVM security enforced upon system resources
conforms to Java2 security.
See Also:
"Java2 Security" on page 10-2
Operating System Resource Lifetime
You can access operating system resources using the standard core Java classes and
methods. Once you access a resource, the time that it remains active varies according
to the type of resource. Memory is garbage collected. Files, threads, and sockets persist
across calls when you use a dedicated mode server. In shared server mode, files,
threads, and sockets terminate when the call ends.
See Also: "Operating System Resources Affected Across Calls" on
page 2-39.
Garbage Collection and Operating System Resources
Imagine that memory is divided into two realms: Java object memory and operating
system constructs. The Java object memory realm contains all objects and variables.
Operating system constructs include resources that the operating system allocates to
the object when it asks. These resources include files, sockets, and so on.
Basic programming rules dictate that you close all memory, both Java objects and
operating system constructs. Java programmers incorrectly assume that memory is
freed by the garbage collector. The garbage collector was created to collect all unused
Java object memory. However, it does not close operating system constructs. All
operating system constructs must be closed by the program before the Java object is
garbage collected.
For example, whenever an object opens a file, the operating system creates the file and
gives the object a file handle. If the file is not closed, then the operating system holds
the file handle construct open until the call ends or JVM exits. This may cause you to
run out of these constructs earlier than necessary. There are a finite number of handles
within each operating system. To guarantee that you do not run out of handles, close
your resources before exiting the method. This includes closing the streams attached to
your sockets before closing the socket.
For performance reasons, the garbage collector cannot examine each object to see if it
contains a handle. As a result, the garbage collector collects Java objects and variables,
but does not issue the appropriate operating system methods for freeing any handles.
Example 2–4 shows how to close the operating system constructs.
Example 2–4 Closing Your Operating System Resources
public static void addFile(String[] newFile)
{
File inFile = new File(newFile);
FileReader in = new FileReader(inFile);
int i;
while ((i = in.read()) != -1)
out.write(i);
/*closing the file, which frees up the operating system file handle*/
in.close();
Java Applications on Oracle Database
2-27
Managing Your Applications Using JMX
}
If you do not close inFile, then eventually the File object will be garbage collected.
Even after the File object is garbage collected, the operating system treats the file as if
it were in use, because it was not closed.
You may want to use Java finalizers to close resources.
However, finalizers are not guaranteed to run in a timely manner.
Instead, finalizers are put on a queue to run when the garbage
collector has time. If you close your resources within your finalizer,
then it might not be freed until JVM exits. The best approach is to
close your resources within the method.
Note:
Managing Your Applications Using JMX
JMX (Java Management Extensions) is a Java technology that supplies tools for
managing and monitoring applications, system objects, devices, service-oriented
networks, and JVM (Java Virtual Machine). This API allows its classes to be
dynamically constructed and changed. So, you can use this technology to monitor and
manage resources as they are created, installed, and implemented. The JMX API also
includes remote access, so a remote management program can interact with a running
application for these purposes.
In JMX, a given resource is instrumented by one or more Java objects known as
MBeans (Managed Beans). These MBeans are registered in a core managed object
server, known as an MBean server, that acts as a management agent and can run on
most devices enabled for the Java programming language. A JMX agent consists of an
MBean server, in which MBeans are registered, and a set of services for handling
MBeans.
See Also:
■
http://java.sun.com/javase/technologies/core/mntr-m
gmt/javamanagement/
■
http://java.sun.com/j2se/1.5.0/docs/guide/security/
jsse/JSSERefGuide.html
■
http://java.sun.com/j2se/1.4.2/docs/guide/security/
jaas/JAASLMDevGuide.html
This section contain the following:
■
Enabling and Starting JMX in a Session
■
OJVM JMX Defaults and Configurability
■
Examples of SQL calls to dbms_java.start_jmx_agent
■
Important Security Notes
Enabling and Starting JMX in a Session
Oracle Database 11g release 1 (11.1) introduces a new role JMXSERVER and a new
procedure dbms_java.start_jmx_agent to support JMX in the database. The
JMXSERVER role provides permissions you need to start and maintain a JMX agent in
a session. The procedure dbms_java.start_jmx_agent starts the agent in a
2-28 Oracle Database Java Developer’s Guide
Managing Your Applications Using JMX
specific session that generally remains active for the duration of the session. Perform
the following to enable and start JMX:
1.
Obtain JMXSERVER from SYS or SYSTEM:
SQL> grant jmxserver to scott;
where, scott is the user name.
2.
Invoke the procedure dbms_java.start_jmx_agent to startup JMX in the
session. This procedure starts an agent activating OJVM JMX server and a listener.
The JMX server runs as one or more daemon threads in the current session and in
general is available for the duration of the session. Once JMX Agent is started in a
session, Java code running in the session can be monitored.
The dbms_java.start_jmx_agent procedure can be invoked with the
following arguments:
port: the port for the JMX listener. The value of this parameter sets the Java
property com.sun.management.jmxremote.port.
ssl: sets the value for the Java property
com.sun.management.jmxremote.ssl. Case for true and false values is
ignored.
auth: the value for the property
com.sun.management.jmxremote.authenticate, otherwise a
semicolon-separated list of JAAS credentials. The value is not case-sensitive.
Each of these arguments can be null or omitted, with null as the default value.
when an argument is null, it does not alter the previously present value of the
corresponding property in the session.
The Java properties corresponding to the parameters of
dbms_java.start_jmx_agent are from the set of Java properties
specified in Sun Java 5.0 JMX documentation. For the full list of Java
JMX properties please refer to
http://java.sun.com/j2se/1.5.0/docs/guide/management
/agent.html
Note:
OJVM JMX Defaults and Configurability
When dbms_java.start_jmx_agent is activated, the property
com.sun.management.jmxremote is set to true. Before invoking
start_jmx_agent, a JMXSERVER-privileged user can preset various management
properties in the following ways:
■
Using the PL/SQL function dbms_java.set_property
■
Invoking method java.lang.System.setProperty
The JMXSERVER role user can also preset the properties in database resident Java
resource specified by Java property com.sun.management.config.file. The
default name for this resource, tried when com.sun.management.config.file is
not set, is lib.management.management.properties. This resource mechanism
is OJVM extension of Sun’s file-based JMX configuration management. This
mechanism is superior for OJVM as it provides more security and per-schema
management. When the resource does not exist in schema, a file-read is attempted as a
fall-back. The default file path, tried when com.sun.management.config.file is
Java Applications on Oracle Database
2-29
Managing Your Applications Using JMX
not set, is $(java.home)/lib/management/management.properties. In Oracle
Database 11g release 1 (11.1) this file contains the following presets:
com.sun.management.jmxremote.ssl.need.client.auth = true
com.sun.management.jmxremote.authenticate = false
The property com.sun.management.jmxremote.ssl.need.client.auth in
conjunction with com.sun.management.jmxremote.ssl, sets JMX for two-way
encrypted SSL authentication with client and server certificates. The default value of
com.sun.management.jmxremote.ssl is true. This configuration is the default
and is preferred over JAAS password authentication.
Note:
For more information visit the following:
■
http://java.sun.com/j2se/1.5.0/docs/guide/managemen
t/agent.html
■
http://java.sun.com/j2se/1.5.0/docs/guide/security/
jsse/JSSERefGuide.html#CustomizingStores
The default Sun JMX Login Module providing file-based store
for passwords is not supported in OJVM for security reasons1. So, if
JAAS password authentication must be used instead of SSL client
authentication, then pass transient JAAS credentials securely as the
auth parameter to dbms_java.start_jmx_agent as illustrated in
this section, or configure JMX to use a secure custom LDAP login
module.
Note:
1
An RMI-related JAAS vulnerability identified in early versions of JDK 5.0 is fixed in
JDK 5.0_10, on which the 11.1 OJVM is based. But, still the default JMX login module
uses clear-text files to store passwords and is not supported. Files
jmxremote.access do not store passwords and are supported.
Examples of SQL calls to dbms_java.start_jmx_agent
Following are some examples of starting the JMX server:
■
Starts the JMX server and the listener using the default settings as described in the
preceding sections or the values set earlier in the same session:
call dbms_java.start_jmx_agent;
■
Starts the JMX server and the listener using the default settings as described in the
preceding sections or the values set earlier in the same session:
call dbms_java.start_jmx_agent(null, null, null);
■
Starts the JMX server and the listener on port 9999 with the other JMX settings
having the default values or the values set earlier in the same session:
call dbms_java.start_jmx_agent('9999');
■
Starts the JMX server and the listener on port 9999 with the other JMX settings
having the default values or the values set earlier in the same session:
call dbms_java.start_jmx_agent('9999', null, null);
2-30 Oracle Database Java Developer’s Guide
Threading in Oracle Database
■
Starts the JMX server and the listener with the JMX settings having the default
values or the values set earlier in the same session and with JAAS credentials
monitorRole/1z2x and controlRole/2p3o:
call dbms_java.start_jmx_agent(null, null,
'monitorRole/1z2x;controlRole/2p3o');
These credentials are transient. The property
com.sun.management.jmxremote.authenticate is set to true.
■
Starts JMX listener on port 9999 with no SSL and no JAAS authentication. Used
only for development or demonstration.
See Also:
"Important Security Notes" on page 2-31
call dbms_java.start_jmx_agent('9999', 'false', 'false');
Important Security Notes
By starting the remote listener with disabled SSL and authentication you violate the
general security guidelines and hence make server vulnerable to attacks. Therefore, it
is always advisable not to use such mode in production environment. This mode is
supported for compatibility with JDK and for development; any production use of
JMX in OJVM must use secure JMX connections.
When supplying security-related property values to dbms_java.set_property,
System.setProperty, or dbms_java.start_jmx_agent, use a non-echo listener
or invoke these through an encrypted JDBC connection from a secure application
layer, such as Oracle Application Server. Do not store passwords in clear-text files. Use
Oracle Wallet to create and manage certificates. Use client certificates for SSL
authentication for better security.
Oracle Database Security Guide for more information about
Oracle database security features
See Also:
Threading in Oracle Database
Oracle JVM is based on the database session model, which is a single-client,
nonpreemptive threading model. Although Java in Oracle Database allows running
threaded programs, it is single-threaded at the execution level. In this model, JVM
runs all Java threads associated with a database session on a single operating system
thread. Once dispatched, a thread continues execution until it explicitly yields by
calling Thread.yield(), blocks by calling Socket.read(), or is preempted by
the execution engine. Once a thread yields, blocks or is preempted, JVM dispatches
another thread.
Note: Starting with 11g release 1 (11.1), Oracle JVM supports thread
preemption. Thread preemption is not mandated by the Java
specification, but is needed to support the new
java.util.concurrent API, present in JDK1.5, properly.
Oracle JVM has added the following features for better performance and thread
management:
Java Applications on Oracle Database
2-31
Threading in Oracle Database
■
■
System calls are at a minimum. Oracle JVM has exchanged some of the normal
system calls with nonsystem solutions. For example, entering a
monitor-synchronized block or method does not require a system call.
Deadlocks are detected.
–
Oracle JVM monitors for deadlocks between threads. If a deadlock occurs,
then Oracle JVM terminates one of the threads and throws the
oracle.aurora.vm.DeadlockError exception.
–
Single-threaded applications cannot suspend. If the application has only a
single thread and you try to suspend it, then the
oracle.aurora.vm.LimboError exception is thrown.
Thread Life Cycle
In a single-threaded application, a call ends when one of the following events occurs:
■
The thread returns to its caller.
■
An exception is thrown and is not caught in Java code.
■
■
The System.exit(), OracleRuntime.exitSession(), or
oracle.aurora.vm.OracleRuntime.exitCall() method is called.
The DBMS_JAVA.endsession() or
DBMS_JAVA.endsession_and_related_state() method is called.
If the initial thread creates and starts other Java threads, then the call ends in one of
the following ways:
■
■
■
The main thread returns to its caller or an exception is thrown and not caught in
this thread and in either case all other non-daemon threads are processed.
Non-daemon threads complete either by returning from their initial method or
because an exception is thrown and not caught in the thread.
Any thread calls the System.exit(), OracleRuntime.exitSession(), or
oracle.aurora.vm.OracleRuntime.exitCall() method.
A call to DBMS_JAVA.endsession() or
DBMS_JAVA.endsession_and_related_state() method.
See Also: "Operating System Resources Affected Across Calls" on
page 2-39.
Prior to 11g release 1 (11.1), when a call ended because of a call to System.exit() or
oracle.aurora.vm.OracleRuntime.exitCall(), Oracle JVM ended the call
abruptly and terminated all threads, in both the dedicated and shared server modes.
In 11g release 1 (11.1), this is addressed by the addition of the following PL/SQL
functions to the DBMS_JAVA package:
■
FUNCTION endsession RETURN VARCHAR2;
■
FUNCTION endsession_and_related_state RETURN VARCHAR2;
See Also:
"Two-Tier Duration for Java Session State" on page 4-4.
During a call, a Java program can recursively cause more Java code to be run. For
example, your program can issue a SQL query using JDBC or SQLJ that, in turn, calls a
trigger written in Java. All the preceding remarks regarding call lifetime apply to the
top-most call to Java code, not to the recursive call. For example, a call to
2-32 Oracle Database Java Developer’s Guide
Threading in Oracle Database
System.exit() from within a recursive call exits the entire top-most call to Java, not
just the recursive call.
System.exit(), OracleRuntime.exitSession(), and OracleRuntime.exitCall()
The System.exit() method terminates JVM, preserving no Java state. It does not
cause the database session to terminate or the client to disconnect. However, the
database session may, and often does, terminate itself immediately afterward.
OracleRuntime.exitSession() also terminates JVM, preserving no Java state.
However, it also terminates the database session and disconnects the client.
The behavior of OracleRuntime.exitCall() varies depending on
OracleRuntime.threadTerminationPolicy(). This method returns a boolean
value. If this value is true, then any active thread should be terminated, rather than
left quiescent, at the end of a database call.
■
■
In a shared server process, threadTerminationPolicy() is always true.
In a shadow (dedicated) process, the default value is false. You can change the
value by calling OracleRuntime.setThreadTerminationPolicy().
–
If you set the value to false, that is the default value, all threads are left
quiescent but receive a ThreadDeath exception for graceful termination.
–
If the value is true, all threads are terminated abruptly.
In addition, there is another method, OracleRuntime.callExitPolicy(). This
method determines when a call is exited if none of the
OracleRuntime.exitSession(), OracleRuntime.exitCall(), or
System.exit() methods were ever called. The call exit policy can be set to one of
the following, using OracleRuntime.setCallExitPolicy():
■
OracleRuntime.EXIT_CALL_WHEN_MAIN_THREAD_TERMINATES
If set to this value, then as soon as the main thread returns or an uncaught
exception occurs on the main thread, all remaining threads, both daemon and
non-daemon are:
■
–
Killed, if threadTerminationPolicy() is true, always in shared server
mode.
–
Left quiescent, if threadTerminationPolicy() is false.
OracleRuntime.EXIT_CALL_WHEN_ALL_NON_DAEMON_THREADS_TERMINATE
This is the default value. If this value is set, then the call ends when only daemon
threads are left running. At this point:
■
–
If the threadTerminationPolicy() is true, always in shared server
mode, then the daemon threads are killed.
–
If the threadTerminationPolicy() is false, then the daemon threads
are left quiescent until the next call. This is the default setting for shadow
(dedicated) server mode.
OracleRuntime.EXIT_CALL_WHEN_ALL_THREADS_TERMINATE
If set to this value, then the call ends only when all threads have either returned or
ended due to an uncaught exception. At this point, the call ends regardless of the
value of threadTerminationPolicy().
Java Applications on Oracle Database
2-33
Shared Servers Considerations
In Oracle database 9.x and earlier database releases, JVM
behaves as if the callExitPolicy() were
OracleRuntime.EXIT_CALL_WHEN_ALL_NON_DAEMON_THREADS_
TERMINATE and the threadTerminationPolicy() were true for
both shared and dedicated server processes. This means kill the
daemon threads at this point. Also, if exitCall() were executed,
then all threads are killed before the call is ended, in both shared and
dedicated server processes.
Note:
Shared Servers Considerations
Oracle recommends dedicated servers for performance
reasons. But it is also possible to have a class of applications that rely
on threads and sockets staying open across calls.
Note:
For sessions that use shared servers, certain limitations exist across calls. The reason is
that a session that uses a shared server is not guaranteed to connect to the same
process on a subsequent database call, and hence the session-specific memory and
objects that need to live across calls are saved in the SGA. This means that
process-specific resources, such as threads, open files, and sockets, must be cleaned up
at the end of each call, and therefore, will not be available for the next call.
This section covers the following topics:
■
End-of-Call Migration
■
Oracle-Specific Support for End-of-Call Optimization
■
The EndOfCallRegistry.registerCallback() Method
■
The EndOfCallRegistry.runCallbacks() Method
■
The Callback Interface
■
The Callback.act() method
■
Operating System Resources Affected Across Calls
End-of-Call Migration
In the shared server mode, Oracle Database preserves the state of your Java program
between calls by migrating all objects that are reachable from static variables to
session space at the end of the call. Session space exists within the session of the client
to store static variables and objects that exist between calls. Oracle JVM
automatically performs this migration operation at the end of every call.
This migration operation is a memory and performance consideration. Hence, you
should be aware of what you designate to exist between calls and keep the static
variables and objects to a minimum. If you store objects in static variables
needlessly, then you impose an unnecessary burden on the memory manager to
perform the migration and consume per-session resources. By limiting your static
variables to only what is necessary, you help the memory manager and improve the
performance of your server.
To maximize the number of users who can run your Java program at the same time, it
is important to minimize the footprint of a session. In particular, to achieve maximum
2-34 Oracle Database Java Developer’s Guide
Shared Servers Considerations
scalability, an inactive session should take up as little memory space as possible. A
simple technique to minimize footprint is to release large data structures at the end of
every call. You can lazily re-create many data structures when you need them again in
another call. For this reason, Oracle JVM has a mechanism for calling a specified Java
method when a session is about to become inactive, such as at the end of a call.
This mechanism is the EndOfCallRegistry notification. It enables you to clear
static variables at the end of the call and reinitialize the variables using a lazy
initialization technique when the next call comes in. You should run this only if you
are concerned about the amount of storage you require the memory manager to store
in between calls. It becomes a concern only for complex stateful server applications
that you implement in Java.
The decision of whether to null-out data structures at the end of the call and then
re-create them for each new call is a typical time and space trade-off. There is some
extra time spent in re-creating the structure, but you can save significant space by not
holding on to the structure between calls. In addition, there is a time consideration,
because objects, especially large objects, are more expensive to access after they have
been migrated to session space. The penalty results from the differences in
representation of session, as opposed to objects based on call-space.
Examples of data structures that are candidates for this type of optimization include:
■
■
■
Buffers or caches.
Static fields, such as arrays, which once initialized can remain unchanged during
the course of the program.
Any dynamically built data structure that can have a space-efficient representation
between calls and a more speed-efficient representation for the duration of a call.
This can be tricky and may complicate your code, making it hard to maintain.
Therefore, you should consider doing this only after demonstrating that the space
saved is worth the effort.
Oracle-Specific Support for End-of-Call Optimization
You can register the static variables that you want cleared at the end of the call
when the buffer, field, or data structure is created. Within the
oracle.aurora.memoryManager.EndOfCallRegistry class, the
registerCallback() method takes an object that implements a Callback object.
The registerCallback() method stores this object until the end of the call. At the
end of the call, Oracle JVM calls the act() method within all registered Callback
objects. The act() method within the Callback object is implemented to clear the
user-defined buffer, field, or data structure. Once cleared, the Callback object is
removed from the registry.
If the end of the call is also the end of the session, then
callbacks are not started, because the session space will be cleared
anyway.
Note:
A weak table holds the registry of end-of-call callbacks. If either the Callback object
or value are not reachable from the Java program, then both the object and the value
will be dropped from the table. The use of a weak table to hold callbacks also means
that registering a callback will not prevent the garbage collector from reclaiming that
object. Therefore, you must hold on to the callback yourself if you need it, and you
cannot rely on the table holding it back.
Java Applications on Oracle Database
2-35
Shared Servers Considerations
The way you use EndOfCallRegistry depends on whether you are dealing with
objects held in static fields or instance fields.
Static fields
Use EndOfCallRegistry to clear state associated with an entire class. In this case,
the Callback object should be held in a private static field. Any code that
requires access to the cached data that was dropped between calls must call a method
that lazily creates, or re-creates, the cached data.
Consider the following example:
import oracle.aurora.memoryManager.Callback;
import oracle.aurora.memoryManager.EndOfCallRegistry;
class Example
{
static Object cachedField = null;
private static Callback thunk = null;
static void clearCachedField()
{
// clear out both the cached field, and the thunk so they don't
// take up session space between calls
cachedField = null;
thunk = null;
}
private static Object getCachedField()
{
if (cachedField == null)
{
// save thunk in static field so it doesn't get reclaimed
// by garbage collector
thunk = new Callback () {
public void act(Object obj)
{
Example.clearCachedField();
}
};
// register thunk to clear cachedField at end-of-call.
EndOfCallRegistry.registerCallback(thunk);
// finally, set cached field
cachedField = createCachedField();
}
return cachedField;
}
private static Object createCachedField()
{
...
}
}
The preceding example does the following:
1.
Creates a Callback object within a static field, thunk.
2.
Registers this Callback object for end-of-call migration.
2-36 Oracle Database Java Developer’s Guide
Shared Servers Considerations
3.
Implements the Callback.act() method to free up all static variables,
including the Callback object itself.
4.
Provides a method, createCachedField(), for lazily re-creating the cache.
When you create the cache, the Callback object is automatically registered within the
getCachedField() method. At end-of-call, Oracle JVM calls the registered
Callback.act() method, which frees the static memory.
Instance fields
Use EndOfCallRegistry to clear state in data structures held in instance fields. For
example, when a state is associated with each instance of a class, each instance has a
field that holds the cached state for the instance and fills in the cached field as
necessary. You can access the cached field with a method that ensures the state is
cached.
Consider the following example:
import oracle.aurora.memoryManager.Callback;
import oracle.aurora.memoryManager.EndOfCallRegistry;
class Example2 implements Callback
{
private Object cachedField = null;
public voidact (Object obj)
{
// clear cached field
cachedField = null;
obj = null;
}
// our accessor method
private static Object getCachedField()
{
if (cachedField == null)
{
// if cachedField is not filled in then we need to
// register self, and fill it in.
EndOfCallRegistry.registerCallback(self);
cachedField = createCachedField();
}
return cachedField;
}
private Object createCachedField()
{
...
}
}
The preceding example does the following:
1.
Implements the instance as a Callback object.
2.
Implements the Callback.act() method to free up the instance fields.
3.
When you request a cache, the Callback object registers itself for the end-of-call
migration.
4.
Provides a method, createCachedField(), for lazily re-creating the cache.
Java Applications on Oracle Database
2-37
Shared Servers Considerations
When you create the cache, the Callback object is automatically registered within the
getCachedField() method. At end-of-call, Oracle JVM calls the registered
Callback.act() method, which frees the cache.
This approach ensures that the lifetime of the Callback object is identical to the
lifetime of the instance, because they are the same object.
The EndOfCallRegistry.registerCallback() Method
The registerCallback() method installs a Callback object within a registry. At
the end of the call, Oracle JVM calls the act() method of all registered Callback
objects.
You can register your Callback object by itself or with an Object instance. If you
need additional information stored within an object to be passed into act(), then you
can register this object with the value parameter, which is an instance of Object.
The following are the valid signatures of the registerCallback() method:
public static void registerCallback(Callback thunk, Object value);
public static void registerCallback(Callback thunk);
The following table lists the parameters of registerCallback and their description:
Parameter
Description
thunk
The Callback object to be called at the end-of-call migration.
value
If you need additional information stored within an object to be passed into
act(), then you can register this object with the value parameter. In some
cases, the value parameter is necessary to hold the state that the callback
needs. However, most users do not need to specify a value for this
parameter.
The EndOfCallRegistry.runCallbacks() Method
The signature of the runCallbacks() method is as follows:
static void runCallbacks()
JVM calls this method at end-of-call and calls act() for every Callback object
registered using registerCallback(). It is called at end-of-call, before object
migration and before the last finalization step.
Note:
Do not call this method in your code.
The Callback Interface
The interface is declared as follows:
Interface oracle.aurora.memoryManager.Callback
Any object you want to register using
EndOfCallRegistry.registerCallback() must implement the Callback
interface. This interface can be useful in your application, where you require
notification at end-of-call.
2-38 Oracle Database Java Developer’s Guide
Shared Servers Considerations
The Callback.act() method
The signature of the act() method is as follows:
public void act(Object value)
You can implement any activity that you require to occur at the end of the call.
Normally, this method contains procedures for clearing any memory that would be
saved to session space.
Operating System Resources Affected Across Calls
In the shared server mode, Oracle JVM closes any open operating system resources at
the end of a database call, as shown in the following table:
Resource
Lifetime
Files
The system closes all files left open when a database call ends.
Threads
All threads are terminated when a call ends.
Sockets
■
Client sockets can exist across calls.
■
Server sockets terminate when the call ends.
Objects that depend
on operating system
resources
Regardless of the usable lifetime of the object, the Java object can be
valid for the duration of the session. This can occur, for example, if the
Java object is stored in a static class variable, or a class variable
references it directly or indirectly. If you attempt to use one of these
Java objects after its usable lifetime is over, then Oracle Database will
throw an exception. This is true for the following examples:
■
■
If an attempt is made to read from a
java.io.FileInputStream that was closed at the end of a
previous call, then a java.io.IOException is raised.
java.lang.Thread.isAlive() is false for any Thread
object running in a previous call and still accessible in a
subsequent call.
You should close resources that are local to a single call when the call ends. However,
for static objects that hold on to operating system resources, you must be aware of
how these resources are affected after the call ends.
Files
In the shared server mode, Oracle JVM automatically closes open operating system
constructs when the call ends. This can affect any operating system resources within
your Java object. If you have a file opened within a static variable, then the file
handle is closed at the end of the call for you. Therefore, if you hold on to the File
object across calls, then the next usage of the file handle throws an exception.
In Example 2–5, the Concat class enables multiple files to be written into a single file,
outFile. On the first call, outFile is created. The first input file is opened, read,
written to outFile, and the call ends. Because outFile is defined as a static
variable, it is moved into session space between call invocations. However, the file
handle is closed at the end of the call. The next time you call addFile(), you will get
an exception.
Example 2–5 Compromising Your Operating System Resources
public class Concat
{
Java Applications on Oracle Database
2-39
Shared Servers Considerations
static File outFile = new File("outme.txt");
FileWriter out = new FileWriter(outFile);
public static void addFile(String[] newFile)
{
File inFile = new File(newFile);
FileReader in = new FileReader(inFile);
int i;
while ((i = in.read()) != -1)
out.write(i);
in.close();
}
}
There are workarounds. To ensure that your handles stay valid, close your files,
buffers, and so on, at the end of every call, and reopen the resource at the beginning of
the next call. Another option is to use the database rather than using operating system
resources. For example, try to use database tables rather than a file. Alternatively, do
not store operating system resources within static objects that are expected to live
across calls. Instead, use operating system resources only within objects local to the
call.
Example 2–6 shows how you can perform concatenation, as in Example 2–5, without
compromising your operating system resources. The addFile() method opens the
outme.txt file within each call, ensuring that anything written into the file is
appended to the end. At the end of each call, the file is closed. Two things occur:
The File object no longer exists outside a call.
■
The operating system resource, the outme.txt file, is reopened for each call. If
you had made the File object a static variable, then the closing of outme.txt
within each call would ensure that the operating system resource is not
compromised.
■
Example 2–6 Correctly Managing Your Operating System Resources
public class Concat
{
public static void addFile(String[] newFile)
{
/*open the output file each call; make sure the input*/
/*file is written out to the end by making it "append=true"*/
FileWriter out = new FileWriter("outme.txt", TRUE);
File inFile = new File(newFile);
FileReader in = new FileReader(inFile);
int i;
while ((i = in.read()) != -1)
out.write(i);
in.close();
/*close the output file between calls*/
out.close();
}
}
2-40 Oracle Database Java Developer’s Guide
Shared Servers Considerations
Sockets
Sockets are used in setting up a connection between a client and a server. For each
database connection, sockets are used at either end of the connection. Your application
does not set up the connection. The connection is set up by the underlying networking
protocol, TTC or IIOP of Oracle Net.
See Also: "Configuring Oracle JVM" on page 4-2 for information
about how to configure your connection.
You may also want to set up another connection, for example, connecting to a
specified URL from within one of the classes stored within the database. To do so,
instantiate sockets for servicing the client and server sides of the connection using the
following:
■
The java.net.Socket() constructor creates a client socket.
■
The java.net.ServerSocket() constructor creates a server socket.
A socket exists at each end of the connection. The server side of the connection that
listens for incoming calls is serviced by a ServerSocket instance. The client side of
the connection that sends requests is serviced through a Socket instance. You can use
sockets as defined within JVM with the restriction that a ServerSocket instance
within a shared server cannot exist across calls.
The following table lists the socket types and their description:
Socket Type
Description
Socket
Because the client side of the connection is outbound, the Socket
instance can be serviced across calls within a shared server.
ServerSocket
The server side of the connection is a listener. The ServerSocket
instance is closed at the end of a call within a shared server. The shared
servers move on to another client at the end of every call. You will
receive an I/O exception stating that the socket was closed, if you try to
use the ServerSocket instance outside of the call it was created in.
Threads
In the shared server mode, when a call ends because of a return or uncaught
exceptions, Oracle JVM throws ThreadDeathException in all daemon threads.
ThreadDeathException essentially forces threads to stop running. Code that
depends on threads living across calls does not behave as expected in the shared
server mode. For example, the value of a static variable that tracks initialization of a
thread may become incorrect in subsequent calls because all threads are killed at the
end of a database call.
As a specific example, the RMI Server, which Sun Microsystems supplies, functions in
the shared server mode. However, it is useful only within the context of a single call.
This is because the RMI Server forks daemon threads, which in the shared server
mode are killed at the end of call, that is, when all non-daemon threads return. If the
RMI server session is reentered in a subsequent call, then these daemon threads are
not restarted and the RMI server fails to function properly.
Java Applications on Oracle Database
2-41
Shared Servers Considerations
2-42 Oracle Database Java Developer’s Guide
3
Calling Java Methods in Oracle Database
This chapter provides an overview and examples of calling Java methods that reside in
Oracle Database. It contains the following sections:
■
Invoking Java Methods
■
Debugging Server Applications
■
How To Tell You Are Running on the Server
■
Redirecting Output on the Server
■
Calling Java in the Database Directly
Invoking Java Methods
The type of the Java application determines how the client calls a Java method. The
following sections discuss each of the Java application programming interfaces (APIs)
available for calling a Java method:
■
Using PL/SQL Wrappers
■
JNI Support
■
Utilizing SQLJ and JDBC with Java in the Database
■
Using Command-Line Interface
■
Using the Client-Side Stub
Using PL/SQL Wrappers
You can run Java stored procedures in the same way as PL/SQL stored procedures. In
Oracle Database, Java is usually invoked through PL/SQL interface.
To call a Java stored procedure, you must publish it through a call specification. The
following example shows how to create, resolve, load, and publish a simple Java
stored procedure that returns a string:
1.
Define a class, Hello, as follows:
public class Hello
{
public static String world()
{
return "Hello world";
}
}
Calling Java Methods in Oracle Database 3-1
Invoking Java Methods
Save the file as a Hello.java file.
2.
Compile the class on your client system using the standard Java compiler, as
follows:
javac Hello.java
It is a good idea to specify the CLASSPATH on the command line with the javac
command, especially when writing shell scripts or make files. The Java compiler
produces a Java binary file, in this case, Hello.class.
You need to determine the location at which this Java code must run. If you run
Hello.class on your client system, then it searches the CLASSPATH for all the
supporting core classes that Hello.class needs for running. This search should
result in locating the dependent classes in one of the following:
■
■
3.
As individual files in one or more directories, where the directories are
specified in the CLASSPATH
Within .jar or .zip files, where the directories containing these files are
specified in the CLASSPATH
Decide on the resolver for the Hello class.
In this case, load Hello.class on the server, where it is stored in the database as
a Java schema object. When you call the world() method, Oracle JVM locates the
necessary supporting classes, such as String, using a resolver. In this case, Oracle
JVM uses the default resolver. The default resolver looks for these classes, first in
the current schema, and then in PUBLIC. All core class libraries, including the
java.lang package, are found in PUBLIC. You may need to specify different
resolvers. You can trace problems earlier, rather than at run time, by forcing
resolution to occur when you use loadjava.
"Resolving Class Dependencies" on page 2-9 and
Chapter 11, "Schema Objects and Oracle JVM Utilities"
See Also:
4.
Load the class on the server using loadjava. You must specify the user name and
password. Run the loadjava command as follows:
loadjava -user scott Hello.class
Password: password
5.
Publish the stored procedure through a call specification.
To call a Java static method with a SQL call, you need to publish the method
with a call specification. A call specification defines the arguments that the method
takes and the SQL types that it returns.
In SQL*Plus, connect to the database and define a top-level call specification for
Hello.world() as follows:
SQL> CONNECT scott
Enter password: password
connected
SQL> CREATE OR REPLACE FUNCTION helloworld RETURN VARCHAR2 AS
2 LANGUAGE JAVA NAME 'Hello.world () return java.lang.String';
3 /
Function created.
6.
Call the stored procedure, as follows:
SQL> VARIABLE myString VARCHAR2(20);
3-2 Oracle Database Java Developer’s Guide
Invoking Java Methods
SQL> CALL helloworld() INTO :myString;
Call completed.
SQL> PRINT myString;
MYSTRING
--------------------------------------Hello world
SQL>
The call helloworld() into :myString statement performs a top-level
call in Oracle Database. SQL and PL/SQL see no difference between a stored
procedure that is written in Java, PL/SQL, or any other language. The call
specification provides a means to tie inter-language calls together in a consistent
manner. Call specifications are necessary only for entry points that are called with
triggers or SQL and PL/SQL calls. Furthermore, JDeveloper can automate the task
of writing call specifications.
See Also:
Chapter 5, "Developing Java Stored Procedures"
JNI Support
The Java Native Interface (JNI) is a standard programming interface for writing
Java native methods and embedding the JVM into native applications. The primary
goal of JNI is to provide binary compatibility of Java applications that use
platform-specific native libraries.
Oracle Database does not support the use of JNI in Java applications. If you use JNI,
then your application is not 100 percent pure Java and the native methods require
porting between platforms. Native methods can cause server failure, violate security,
and corrupt data.
Utilizing SQLJ and JDBC with Java in the Database
You can use SQLJ and Java Database Connectivity (JDBC) APIs from a Java client. Both
APIs establish a session with a given user name and password on the database and
run SQL queries against the database. The following table lists the APIs and their
description:
API
Description
JDBC
Use this API for more complex or dynamic SQL queries. JDBC requires you
to establish the session, construct the query, and so on.
SQLJ
Use this API for easy SQL queries, both static and dynamic. SQLJ typically
runs against a known table with known column names.
This section covers the following topics:
■
JDBC
■
SQLJ
■
Example Comparing JDBC and SQLJ
■
Complete SQLJ Example
■
SQLJ Strong Typing Paradigm
■
Translating a SQLJ Program
Calling Java Methods in Oracle Database 3-3
Invoking Java Methods
■
Running a SQLJ Program in the Server
■
Converting a Client Application to Run on the Server
■
Interacting with PL/SQL
JDBC
JDBC is an industry-standard API developed by Sun Microsystems that lets you
embed SQL statements as Java method arguments. JDBC is based on the X/Open SQL
Call Level Interface (CLI) and complies with the SQL92 Entry Level standard. Each
vendor, such as Oracle, creates its JDBC implementation by implementing the
interfaces of the standard java.sql package. Oracle provides the following JDBC
drivers that implement these standard interfaces:
■
■
■
The JDBC Thin driver, a 100 percent pure Java solution that you can use for either
client-side applications or applets and requires no Oracle client installation.
The JDBC OCI driver, which you use for client-side applications and requires an
Oracle client installation.
The server-side JDBC driver embedded in Oracle Database.
Using JDBC is a step-by-step process of performing the following tasks:
1.
Obtaining a connection handle
2.
Creating a statement object of some type for your desired SQL operation
3.
Assigning any local variables that you want to bind to the SQL operation
4.
Carrying out the operation
5.
Optionally retrieving the result sets
This process is sufficient for many applications, but becomes cumbersome for any
complicated statements. Dynamic SQL operations, where the operations are not
known until run time, require JDBC. However, in typical applications, this represents a
minority of the SQL operations.
SQLJ
SQLJ offers an industry-standard way to embed any static SQL operation directly into
the Java source code in one simple step, without requiring the multiple steps of JDBC.
Oracle SQLJ complies with the X3H2-98-320 American National Standards Institute
(ANSI) standard.
SQLJ consists of a translator, which is a precompiler that supports standard SQLJ
programming syntax, and a run-time component. After creating your SQLJ source
code in a .sqlj file, you process it with the translator. The translator translates the
SQLJ source code to standard Java source code, with SQL operations converted to calls
to the SQLJ run time. In Oracle Database SQLJ implementation, the translator calls a
Java compiler to compile the Java source code. When your SQLJ application runs, the
SQLJ run time calls JDBC to communicate with the database.
SQLJ also enables you to catch errors in your SQL statements before run time. JDBC
code, being pure Java, is compiled directly. The compiler cannot detect SQL errors. On
the other hand, when you translate SQLJ code, the translator analyzes the embedded
SQL statements semantically and syntactically, catching SQL errors during
development, instead of allowing an end user to catch them when running the
application.
3-4 Oracle Database Java Developer’s Guide
Invoking Java Methods
Example Comparing JDBC and SQLJ
The following is an example of a JDBC code and a SQLJ code that perform a simple
operation:
JDBC:
// Assume you already have a JDBC Connection object conn
// Define Java variables
String name;
int id=37115;
float salary=20000;
// Set up JDBC prepared statement.
PreparedStatement pstmt = conn.prepareStatement
("SELECT ename FROM emp WHERE empno=? AND sal>?");
pstmt.setInt(1, id);
pstmt.setFloat(2, salary);
// Execute query; retrieve name and assign it to Java variable.
ResultSet rs = pstmt.executeQuery();
while (rs.next())
{
name=rs.getString(1);
System.out.println("Name is: " + name);
}
// Close result set and statement objects.
rs.close()
pstmt.close();
Assume that you have established a JDBC connection, conn. Next, you need to do the
following:
1.
Define the Java variables, name, id, and salary.
2.
Create a PreparedStatement instance.
You can use a prepared statement whenever values in the SQL statement must be
dynamically set. You can use the same prepared statement repeatedly with
different variable values. The question marks (?) in the prepared statement are
placeholders for Java variables. In the preceding example, these variables are
assigned values using the pstmt.setInt() and pstmt.setFloat() methods.
The first ? refers to the int variable id and is set to a value of 37115. The second
? refers to the float variable salary and is set to a value of 20000.
3.
Run the query and return the data into a ResultSet object.
4.
Retrieve the data of interest from the ResultSet object and display it. In this
case, the ename column. A result set usually contains multiple rows of data,
although this example has only one row.
SQLJ:
String name;
int id=37115;
float salary=20000;
#sql {SELECT ename INTO :name FROM emp WHERE empno=:id AND sal>:salary};
System.out.println("Name is: " + name);
In addition to allowing SQL statements to be directly embedded in Java code, SQLJ
supports Java host expressions, also known as bind expressions, to be used directly in
Calling Java Methods in Oracle Database 3-5
Invoking Java Methods
the SQL statements. In the simplest case, a host expression is a simple variable, as in
this example. However, more complex expressions are allowed as well. Each host
expression is preceded by colon (:). This example uses Java host expressions, name, id,
and salary. In SQLJ, because of its host expression support, you do not need a result
set or equivalent when you are returning only a single row of data.
All SQLJ statements, including declarations, start with the
#sql token.
Note:
Complete SQLJ Example
This section presents a complete example of a simple SQLJ program:
import java.sql.*;
import sqlj.runtime.ref.DefaultContext;
import oracle.sqlj.runtime.Oracle;
#sql ITERATOR MyIter (String ename, int empno, float sal);
public class MyExample
{
public static void main (String args[]) throws SQLException
{
Oracle.connect("jdbc:oracle:thin:@oow11:5521:sol2", "scott", "tiger");
#sql { INSERT INTO emp (ename, empno, sal) VALUES ('SALMAN', 32, 20000) };
MyIter iter;
#sql iter={ SELECT ename, empno, sal FROM emp };
while (iter.next())
{
System.out.println(iter.ename()+" "+iter.empno()+" "+iter.sal());
}
}
}
In the preceding example, you do the following:
1.
Declare your iterators.
SQLJ uses a strongly-typed version of JDBC result sets, known as iterators. An
iterator has a specific number of columns of specific data types. You must define
your iterator types before using them, as in this example.
#sql ITERATOR MyIter (String ename, int empno, float sal);
This declaration results in SQLJ creating an iterator class, MyIter. Iterators of type
MyIter can store results whose first column maps to a Java String, second
column maps to a Java int, and third column maps to a Java float. This
definition also names the three columns as ename, empno, and sal, to match the
column names of the referenced table in the database. MyIter is a named iterator.
2.
Connect to the database.
Oracle.connect("jdbc:oracle:thin:@oow11:5521:sol2","scott", "tiger");
SQLJ provides the Oracle class and its connect() method accomplishes the
following important tasks:
a.
Registers the Oracle JDBC drivers that SQLJ uses to access the database, in this
case, the JDBC Thin driver.
3-6 Oracle Database Java Developer’s Guide
Invoking Java Methods
3.
b.
Opens a database connection for the specified schema, in this case, user scott
with password tiger, at the specified URL. In this case, the URL points to
host oow11, port 5521, and SID so12.
c.
Establishes this connection as the default connection for the SQLJ statements.
Although each JDBC statement must explicitly specify a connection object, a
SQLJ statement can either implicitly use a default connection or optionally
specify a different connection.
Process a SQL statement. The following is accomplished:
a.
Insert a row into the emp table:
#sql {INSERT INTO emp (ename, empno, sal) VALUES ('SALMAN', 32, 20000)};
b.
Instantiate and populate the iterator:
MyIter iter;
#sql iter={SELECT ename, empno, sal FROM emp};
4.
Access the data that was populated within the iterator.
while (iter.next())
{
System.out.println(iter.ename()+" "+iter.empno()+" "+iter.sal());
}
The next() method is common to all iterators and plays the same role as the
next() method of a JDBC result set, returning true and moving to the next row
of data, if any rows remain. You can access the data in each row by calling iterator
accessor methods whose names match the column names. This is a characteristic
of all named iterators. In this example, you access the data using the methods
ename(), empno(), and sal().
SQLJ Strong Typing Paradigm
SQLJ uses strong typing, such as iterators, instead of result sets. This enables the SQL
instructions to be checked against the database during translation. For example, SQLJ
can connect to a database and check your iterators against the database tables that will
be queried. The translator will verify that they match, enabling you to catch SQL errors
during translation that would otherwise not be caught until a user runs your
application. Furthermore, if changes are subsequently made to the schema, then you
can determine if these changes affect the application by rerunning the translator.
Translating a SQLJ Program
Integrated development environments (IDEs), such as Oracle JDeveloper, can
translate, compile, and customize your SQLJ program as you build it. Oracle
JDeveloper is a Microsoft Windows-based visual development environment for Java
programming. If you are not using an IDE, then use the front-end SQLJ utility, sqlj.
You can run it as follows:
%sqlj MyExample.sqlj
The SQLJ translator checks the syntax and semantics of your SQL operations. You can
enable online checking to check your operations against the database. If you choose to
do this, then you must specify an example database schema in your translator option
settings. It is not necessary for the schema to have data identical to the one that the
program will eventually run against. However, the tables must have columns with
corresponding names and data types. Use the user option to enable online checking
Calling Java Methods in Oracle Database 3-7
Invoking Java Methods
and specify the user name, password, and URL of your schema, as in the following
example:
%sqlj -user=scott@jdbc:oracle:thin:@oow11:5521:sol2 MyExample.sqlj
Password: password
Running a SQLJ Program in the Server
Many SQLJ applications run on a client. However, SQLJ offers an advantage in
programming stored procedures, which are usually SQL-intensive, to run on the
server.
There is almost no difference between writing a client-side SQLJ program and a
server-side SQLJ program. The SQLJ run-time packages are automatically available on
the server. However, you need to consider the following:
■
■
■
There are no explicit database connections for code running on the server. There is
only a single implicit connection. You do not need the usual connection code. If
you are porting an existing client-side application, then you do not have to remove
the connection code, because it will be ignored.
The JDBC server-side internal driver does not support auto-commit functionality.
Use SQLJ syntax for manual commits and rollbacks of your transactions.
On the server, the default output device is a trace file, not the user screen. This is,
normally, an issue only for development, because you would not write to
System.out in a deployed server application.
To run a SQLJ program on the server, presuming you developed the code on a client,
you have two options:
■
■
Translate your SQLJ source code on the client and load the individual components,
such as the Java classes and resources, on the server. In this case, it is easy to
bundle them into a .jar file first and then load them on the server.
Load your SQLJ source code on the server for the embedded translator to
translate.
In either case, use the loadjava tool to load the file or files to the server.
Converting a Client Application to Run on the Server
To convert an existing SQLJ client-side application to run on the server, after the
application has already been translated on the client, perform the following steps:
1.
Create a .jar file for your application components.
2.
Use the loadjava tool to load the .jar file on the server.
3.
Create a SQL wrapper in the server for your application. For example, to run the
preceding MyExample application on the server, run the following statement:
CREATE OR REPLACE PROCEDURE sqlj_myexample AS LANGUAGE JAVA NAME
`MyExample.main(java.lang.String[])';
You can then run sqlj_myexample, similar to any other stored procedure.
Interacting with PL/SQL
All the Oracle JDBC drivers communicate seamlessly with Oracle SQL and PL/SQL,
and it is important to note that SQLJ interoperates with PL/SQL. You can start using
SQLJ without having to rewrite any PL/SQL stored procedures. Oracle SQLJ includes
3-8 Oracle Database Java Developer’s Guide
Invoking Java Methods
syntax for calling PL/SQL stored procedures and also lets you embed anonymous
PL/SQL blocks in SQLJ statements.
Using Command-Line Interface
The command-line interface to Oracle JVM is analogous to using the JDK or JRE shell
commands. You can:
■
Use the standard -classpath syntax to indicate where to find the classes to load
■
Set the system properties by using the standard -D syntax
The interface is a PL/SQL function that takes a string (VARCHAR2) argument, parses it
as a command-line input and if it is properly formed, runs the indicated Java method
in Oracle JVM. To do this, PL/SQL package DBMS_JAVA provides the following
functions:
■
runjava
■
runjava_in_current_session
runjava
This function takes the Java command line as its only argument and runs it in Oracle
JVM. The return value is null on successful completion, otherwise an error message.
The format of the command line is the same as that taken by the JDK shell command,
that is:
[option switches] name_of_class_to_execute [arg1 arg2 ... argn]
You can use the option switches -classpath, -D, -Xbootclasspath, and
-jar. This function differs from the runjava_in_current_session function in
that it clears any Java state remaining from previous use of Java in the session, prior to
running the current command. This is necessary, in particular, to guarantee that static
variable values derived at class initialization time from -classpath and -D
arguments reflect the values of those switches in the current command line.
FUNCTION runjava(cmdline VARCHAR2) RETURN VARCHAR2;
runjava_in_current_session
This function is the same as the runjava function, except that it does not clear Java
state remaining from previous use of Java in the session, prior to executing the current
command line.
FUNCTION runjava_in_current_session(cmdline VARCHAR2) RETURN VARCHAR2;
Syntax
The syntax of the command line is of the following form:
[-options] classname [arguments...]
[-options] -jar jarfile [arguments...]
Options
-classpath
-D
-Xbootclasspath
-Xbootclasspath/a
-Xbootclasspath/p
Calling Java Methods in Oracle Database 3-9
Invoking Java Methods
-cp
The effect of the first form is to run the main method of the
class identified by classname with the arguments. The effect of the
second form is to run the main method of the class identified by the
Main-Class attribute in the manifest of the JAR file identified by
JAR. This is analogous to how the JDK/JRE interprets this syntax.
Note:
Argument Summary
Table 3–1 summarizes the command-line arguments.
Table 3–1
Command Line Argument Summary
Argument
Description
classpath
Accepts a colon (:) separated list of directories, JAR archives, and ZIP
archives to search for class files. In general, the value of -classpath
or similar arguments refer to file system locations as they would in a
standard Java runtime. You also have an extension to this syntax to
allow for terms that refer to database resident Java objects and sets of
bytes. Refer to Appendix B, "Classpath Extensions and User
Classloaded Metadata" for more information about -classpath
extensions.
D
Establishes values for system properties that you use only when the
Java session is first initialized. The default behavior of the command
line interface is to terminate any existing Java session prior to running
the new command, so that session initialization occurs each time the
command line interface is used.
Xbootclasspath
Accepts a colon (:) separated list of directories, JAR archives, and ZIP
archives. This option is used to set search path for bootstrap classes
and resources.
Xbootclasspath/a
Accepts a colon (:) separated list of directories, JAR archives, and ZIP
archives. This is appended to the end of bootstrap class path.
Xbootclasspath/p
Accepts a colon (:) separated list of directories, JAR archives, and ZIP
archives. This is added in front of bootstrap class path.
cp
Acts as a synonym of -classpath.
Note: System classes created by create java system are always
used before using any file or folder that are found using the
-Xbootclasspath option.
Using the Client-Side Stub
Oracle Database 10g introduced the client-side stub, formerly known as native Java
interface, for calls to server-side Java code. It is a simplified application integration.
Client-side and middle-tier Java applications can directly call Java in the database
without defining a PL/SQL wrapper. The client-side stub uses the server-side Java
class reflection capability.
In previous releases, calling Java stored procedures and functions from a database
client required Java Database Connectivity (JDBC) calls to the associated PL/SQL
wrappers. Each wrapper had to be manually published with a SQL signature and a
Java implementation. This had the following disadvantages:
3-10 Oracle Database Java Developer’s Guide
Invoking Java Methods
■
The signatures permitted only Java types that had direct SQL equivalents
■
Exceptions issued in Java were not properly returned
The JPublisher -java option provides functionality to overcome these disadvantages.
To remedy the deficiencies of JDBC calls to associated PL/SQL wrappers, the -java
option uses an API for direct invocation of static Java methods. This functionality is
also useful for Web services.
The functionality of the -java option mirrors that of the -sql option, creating a
client-side Java stub class to access a server-side Java class, as opposed to creating a
client-side Java class to access a server-side SQL object or PL/SQL package. The
client-side stub class uses JPublisher code that mirrors the server-side class and
includes the following features:
■
■
Methods corresponding to the public static methods of the server class
Two constructors, one that takes a JDBC connection and one that takes the
JPublisher default connection context instance
At run time, the stub class is instantiated with a JDBC connection. Calls to the methods
of the stub class result in calls to the corresponding methods of the server-side class.
Any Java types used in these published methods must be primitive or serializable.
Figure 3–1 demonstrates a client-side stub API for direct invocation of static
server-side Java methods. JPublisher transparently takes care of stub generation.
Figure 3–1 Client-Side Stub Interface
Oracle Fusion Middleware
Oracle
Database
Decoding
End point implicity
specifies the type
of service provided
by the server
JPub
Generated
Java
Classes
OC4J
Web Services
Servlet
Encoding
PL/SQL
Query
Java
DML
SOAP response
per WSDL
Soap
Libraries
XML
Parser
You can use the -java option to publish a server-side Java class, as follows:
-java=className
Consider the oracle.sqlj.checker.JdbcVersion server-side Java class, with the
following APIs:
public class oracle.sqlj.checker.JdbcVersion
{
...
public java.lang.String toString();
public static java.lang.String to_string();
...
}
As an example, assume that you want to call the following method on the server:
public String oracle.sqlj.checker.JdbcVersion.to_string();
Calling Java Methods in Oracle Database
3-11
Invoking Java Methods
Use the following command to publish JdbcVersion for client-side invocation, using
JPublisher:
% jpub -sql=scott/password -java=oracle.sqlj.checker.JdbcVersion:JdbcVersion
Client
This command generates the client-side Java class, JdbcVersionClient, which
contains the following APIs:
public class JdbcVersionClient
{
...
public java.lang.String toString(long _handle);
public java.lang.String to_string();
...
}
All static methods are mapped to instance methods in the client-side code. A instance
method in the server-side class, toString() for example, is mapped to a method
with an extra handle. A handle represents an instance of
oracle.sqlj.checker.JdbcVersion in the server. The handle is used to call the
instance method on the server-side.
See Also:
Oracle Database JPublisher User's Guide
Using the Default Service Feature
Starting from Oracle Database 11g release 1 (11.1), Oracle Database client provides a
new default connection feature. If you install Oracle Database client, then you need
not specify all the details of the database server in the connection URL. Under certain
conditions, Oracle Database connection adapter requires only the host name of the
computer where the database is installed.
For example, in the JDBC connection URL syntax, that is:
jdbc:oracle:driver_type:[username/password]@[//]host_name[:port][:ORCL]
,the following have become optional:
■
// is optional.
■
:port is optional.
You need to specify a port only if the default Oracle Net listener port (1521) is not
used.
■
:ORCL or the service name is optional.
The connection adapter for Oracle Database Client connects to the default
service on the host. On the host, this is set to ORCL in the listener.ora file.
Testing the Default Service with a Basic Configuration
The following code snippet shows a basic configuration of the listener.ora file,
where the default service is defined.
Example 3–1 Basic Configuration of listener.ora with the Default Service Defined
MYLISTENER = (ADDRESS_LIST=(ADDRESS=(PROTOCOL=tcp)(HOST=testserver1)(PORT=1521)))
DEFAULT_SERVICE_MYLISTENER=dbjf.app.myserver.com
SID_LIST_MYLISTENER = (SID_LIST=(SID_DESC=(SID_NAME=dbjf)
(GLOBAL_DBNAME=dbjf.app.myserver.com)(ORACLE_HOME=/test/oracle))
3-12 Oracle Database Java Developer’s Guide
How To Tell You Are Running on the Server
)
After defining the listener.ora file, restart the listener with the following
command:
lsnrctl start mylistener
Now, any of the following URLs should work with this configuration of the
listener.ora file:
■
jdbc:oracle:thin:@//testserver1.myserver.com.com
■
jdbc:oracle:thin:@//testserver1.myserver.com:1521
■
jdbc:oracle:thin:@testserver1.myserver.com
■
jdbc:oracle:thin:@testserver1.myserver.com:1521
■
jdbc:oracle:thin:@(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=tes
tserver1.myserver.com)(PORT=1521)))
■
jdbc:oracle:thin:@(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=tes
tserver1.myserver.com)))
■
jdbc:oracle:thin:@(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=tes
tserver1.myserver.com)(PORT=1521))(CONNECT_DATA=(SERVICE_NAME
=)))
Note: Default service is a new feature in Oracle Database 11g Release
1 (11.1). If you use any other version of Oracle Database Client to
connect to the database, then you must specify the SID.
Debugging Server Applications
Oracle Database furnishes a debugging capability that is useful for developers who
use the jdb debugger. The interface that is provided is the Java Debug Wire
Protocol (JDWP), which is supported by Java Development Kit (JDK) 1.4 and later
versions.
Some of the new features that the JDWP protocol supports are:
■
Listening for connections
■
Changing the values of variables while debugging
■
Evaluating arbitrary Java expressions, including method evaluation
Oracle JDeveloper provides a user-friendly integration with these debugging features.
Other independent IDE vendors will be able to integrate their own debuggers with
Oracle Database.
See Also: Oracle Database PL/SQL Packages and Types Reference and
Oracle Database Advanced Application Developer's Guide
How To Tell You Are Running on the Server
You may want to write Java code that runs in a certain way on the server and in
another way on the client. In general, Oracle does not recommend this. In fact, JDBC
and SQLJ enable you to write portable code that avoids this problem, even though the
drivers used in the server and client are different.
Calling Java Methods in Oracle Database
3-13
Redirecting Output on the Server
If you want to determine whether your code is running on the server, then use the
System.getProperty() method, as follows:
System.getProperty ("oracle.jserver.version")
The getProperty() method returns the following:
■
A String that represents Oracle Database release, if running on the server
■
null, if running on the client
Redirecting Output on the Server
You can pass Java output to SQL statements to provide more extensive control over
the destination of output from Oracle JVM. The PL/SQL package DBMS_JAVA has
been enhanced by adding the following new functions, which provide extended
functionality to what was previously available only with the
DBMS_JAVA.SET_OUTPUT procedure:
■
set_output_to_sql
■
remove_output_to_sql
■
enable_output_to_sql
■
disable_output_to_sql
■
query_output_to_sql
set_output_to_sql
set_output_to_sql defines a named output specification that constitutes an
instruction for executing a SQL statement, whenever output to the default
System.out and System.err streams occurs. The specification is defined either for
the duration of the current session, or till the remove_output_to_sql function is
called with its ID. The SQL actions prescribed by the specification occur whenever
there is Java output. This can be stopped and started by calling the
disable_output_to_sql and enable_output_to_sql functions respectively.
The return value of this function is null on success, otherwise an error message.
FUNCTION set_output_to_sql (id VARCHAR2,
stmt VARCHAR2,
bindings VARCHAR2,
no_newline_stmt VARCHAR2 default null,
no_newline_bindings VARCHAR2 default null,
newline_only_stmt VARCHAR2 default null,
newline_only_bindings VARCHAR2 default null,
maximum_line_segment_length NUMBER default 0,
allow_replace NUMBER default 1,
from_stdout NUMBER default 1,
from_stderr NUMBER default 1,
include_newlines NUMBER default 0,
eager NUMBER default 0) return VARCHAR2;
Table 3–2 describes the arguments the set_output_to_sql function takes.
3-14 Oracle Database Java Developer’s Guide
Redirecting Output on the Server
Table 3–2
set_output_to_sql Argument Summary
Argument
Description
id
The name of the specification. Multiple specifications may exist in the
same session, but each must have a distinct ID. The ID is used to
identify the specification in the functions remove_output_to_sql,
enable_output_to_sql, disable_output_to_sql, and
query_output_to_sql.
stmt
The default SQL statement to execute when Java output occurs.
bindings
A string containing tokens from the set ID, TEXT, LENGTH, LINENO,
SEGNO, NL, and ERROUT. This string defines how the SQL statement
stmt is bound. The position of a token in the bindings string
corresponds to the bind position in the SQL statement. The meanings
of the tokens are:
■
ID is the ID of the specification. It is bound as a VARCHAR2.
■
TEXT is the text being output. It is bound as a VARCHAR2.
■
LENGTH is the length of the text. It is bound as a NUMBER.
■
■
■
■
LINENO is the line number since the beginning of session
output. It is bound as a NUMBER.
SEGNO is the segment number within a line that is being output
in more than one piece. It is bound as a NUMBER.
NL is a boolean indicating whether the text is to be regarded as
newline terminated. It is bound as a NUMBER. The newline may
or may not actually be included in the text, depending on the
value of the include_newlines argument.
ERROUT is a boolean indicating whether the output came from
System.out or System.err. It is bound as a NUMBER. The
value is 0, if the output came from System.out.
no_newline_stmt
An optional alternate SQL statement to execute, when the output is
not newline terminated.
no_newline_bindings
A string with the same syntax as for the bindings argument discussed
previously, describing how the no_newline_stmt is bound.
newline_only_stmt
An optional alternate SQL statement to execute when the output is a
single newline.
newline_only_binding
s
A string with the same syntax as for the bindings argument discussed
previously, describing how the newline_only_stmt is bound.
maximum_line_segme The maximum number of characters that is bound in a given
nt_length
execution of the SQL statement. Longer output sequences are broken
up into separate calls with distinct SEGNO values. A value of 0 means
no maximum.
allow_replace
Controls behavior when a previously defined specification with the
same ID exists. A value of 1 means replacing the old specification. 0
means returning an error message without modifying the old
specification.
from_stdout
Controls whether output from System.out causes execution of the
SQL statement prescribed by the specification. A value of 0 means
that if the output came from System.out, then the statement is not
executed, even if the specification is otherwise enabled.
from_stderr
Controls whether output from System.err causes execution of the
SQL statement prescribed by the specification. A value of 0 means
that if the output came from System.err, then the statement is not
executed, even if the specification is otherwise enabled.
Calling Java Methods in Oracle Database
3-15
Redirecting Output on the Server
Table 3–2 (Cont.) set_output_to_sql Argument Summary
Argument
Description
include_newlines
Controls whether newline characters are left in the output when they
are bound to text. A value of 0 means newlines are not included. But
the presence of the newline is still indicated by the NL binding and
the use of no_newline_stmt.
eager
Controls whether output not terminated by a newline causes
execution of the SQL statement every time it is received, or
accumulates such output until a newline is received. A value of 0
means that unterminated output is accumulated.
remove_output_to_sql
remove_output_to_sql deletes a specification created by set_output_to_sql.
If no such specification exists, an error message is returned.
FUNCTION remove_output_to_sql (id VARCHAR2) return VARCHAR2;
enable_output_to_sql
enable_output_to_sql reenables a specification created by set_output_to_sql
and subsequently disabled by disable_output_to_sql. If no such specification
exists, an error message is returned. If the specification is not currently disabled, there
is no change.
FUNCTION enable_output_to_sql (id VARCHAR2) return VARCHAR2;
disable_output_to_sql
disable_output_to_sql disables a specification created by
set_output_to_sql. You can enable the specification by calling
enable_output_to_sql. While disabled, the SQL statement prescribed by the
specification is not executed. If no such specification exists, an error message is
returned. If the specification is already disabled, there is no change.
FUNCTION disable_output_to_sql (id VARCHAR2) return VARCHAR2;
query_output_to_sql
query_output_to_sql returns a message describing a specification created by
set_output_to_sql. If no such specification exists, then an error message is
returned. Passing null to this function causes all existing specifications to be
displayed.
FUNCTION query_output_to_sql (id VARCHAR2) return VARCHAR2;
Another way of achieving control over the destination of output from Oracle JVM is to
pass your Java output to an autonomous Java session. This provides a very general
mechanism for propagating the output to various kinds of targets, such as disk files,
sockets, and URLS. But, you need to keep in mind that the Java session that processes
the output is logically distinct from the main session, so that there are no other,
unwanted interactions between them. To do this, PL/SQL package DBMS_JAVA
provides the following functions:
■
set_output_to_java
■
remove_output_to_java
3-16 Oracle Database Java Developer’s Guide
Redirecting Output on the Server
■
enable_output_to_java
■
disable_output_to_java
■
query_output_to_java
■
set_output_to_file
■
remove_output_to_file
■
enable_output_to_file
■
disable_output_to_file
■
query_output_to_file
set_output_to_java
set_output_to_java defines a named output specification that gives an instruction
for executing a Java method whenever output to the default System.out and
System.err streams occurs. The Java method prescribed by the specification is
executed in a separate VM context with separate Java session state from the rest of the
session.
FUNCTION set_output_to_java (id VARCHAR2,
class_name VARCHAR2,
class_schema VARCHAR2,
method VARCHAR2,
bindings VARCHAR2,
no_newline_method VARCHAR2 default null,
no_newline_bindings VARCHAR2 default null,
newline_only_method VARCHAR2 default null,
newline_only_bindings VARCHAR2 default null,
maximum_line_segment_length NUMBER default 0,
allow_replace NUMBER default 1,
from_stdout NUMBER default 1,
from_stderr NUMBER default 1,
include_newlines NUMBER default 0,
eager NUMBER default 0,
initialization_statement VARCHAR2 default null,
finalization_statement VARCHAR2 default null)return VARCHAR2;
Table 3–3 describes the aguments the set_output_to_java method takes.
Table 3–3
set_output_to_java Argument Summary
Argument
Description
class_name
The name of the class defining one or more methods.
class_schema
The schema in which the class is defined. A null value means the class
is defined in the current schema, or PUBLIC.
method
The name of the method.
bindings
A string that defines how the arguments to the method are bound.
This is a string of tokens with the same syntax as
set_output_to_sql. The position of a token in the string
determines the position of the argument it describes. All arguments
must be of type INT, except for those corresponding to the tokens ID
or TEXT, which must be of type java.lang.String.
no_newline_method
An optional alternate method to execute when the output is not
newline terminated.
newline_only_method
An optional alternate method to execute when the output is a single
newline.
Calling Java Methods in Oracle Database
3-17
Redirecting Output on the Server
Table 3–3 (Cont.) set_output_to_java Argument Summary
Argument
Description
initialization_statemen An optional SQL statement that is executed once per Java session
t
prior to the first time the methods that receive output are executed.
This statement is executed in same Java VM context as the output
methods are executed. Typically such a statement is used to run a
Java stored procedure that initializes conditions in the separate VM
context so that the methods that receive output can function as
intended. For example, such a procedure might open a stream that the
output methods write to.
finalization_statement
An optional SQL statement that is executed once when the output
specification is about to be removed or the session is ending. Like the
initialization_statement, this runs in the same JVM context
as the methods that receive output. It runs only if the initialization
method has run, or if there is no initialization method.
remove_output_to_java
remove_output_to_java deletes a specification created by
set_output_to_java. If no such specification exists, an error message is returned
FUNCTION remove_output_to_java (id VARCHAR2) return VARCHAR2;
enable_output_to_java
enable_output_to_java reenables a specification created by
set_output_to_java and subsequently disabled by disable_output_to_java.
If no such specification exists, an error message is returned. If the specification is not
currently disabled, there is no change.
FUNCTION enable_output_to_java (id VARCHAR2) return VARCHAR2;
disable_output_to_java
disable_output_to_java disables a specification created by
set_output_to_java. The specification may be reenabled by
enable_output_to_java. While disabled, the SQL statement prescribed by the
specification is not executed. If no such specification exists, an error message is
returned. If the specification is already disabled, there is no change.
FUNCTION disable_output_to_java (id VARCHAR2) return VARCHAR2;
query_output_to_java
query_output_to_java returns a message describing a specification created by
set_output_to_java. If no such specification exists, an error message is returned.
Passing null to this function causes all existing specifications to be displayed.
FUNCTION query_output_to_java (id VARCHAR2) return VARCHAR2;
set_output_to_file
set_output_to_file defines a named output specification that constitutes an
instruction to capture any output sent to the default System.out and System.err
streams and append it to a specified file. This is implemented using a special case of
set_output_to_java. The argument file_path specifies the path to the file to
which to append the output. The arguments allow_replace, from_stdout, and
3-18 Oracle Database Java Developer’s Guide
Redirecting Output on the Server
from_stderr are all analogous to the arguments having the same name as in
set_output_to_sql.
FUNCTION set_output_to_file (id VARCHAR2,
file_path VARCHAR2,
allow_replace NUMBER default 1,
from_stdout NUMBER default 1,
from_stderr NUMBER default 1) return VARCHAR2;
remove_output_to_file
This function is analogous to remove_output_to_java.
FUNCTION remove_output_to_file (id VARCHAR2) return VARCHAR2;
enable_output_to_file
This function is analogous to enable_output_to_java.
FUNCTION enable_output_to_file (id VARCHAR2) return VARCHAR2;
disable_output_to_file
This function is analogous to disable_output_to_java.
FUNCTION disable_output_to_file (id VARCHAR2) return VARCHAR2;
query_output_to_file
This function is analogous to query_output_to_java.
FUNCTION query_output_to_file (id VARCHAR2) return VARCHAR2;
The following DBMS_JAVA functions control whether Java output appears in the .trc
file:
■
PROCEDURE enable_output_to_trc;
■
PROCEDURE disable_output_to_trc;
■
FUNCTION query_output_to_trc return VARCHAR2;
Prior to 11g release 1 (11.1), the fact that Java output appeared
in the .trc file was not modifiable.
Note:
Redirecting the output to SQL*Plus Text Buffer
As in previous releases, you can use the DBMS_JAVA package procedure SET_OUTPUT
to redirect output to the SQL*Plus text buffer:
SQL> SET SERVEROUTPUT ON
SQL> CALL dbms_java.set_output(2000);
The minimum and default buffer size is 2,000 bytes and the maximum size is 1,000,000
bytes. In the following example, the buffer size is increased to 5,000 bytes:
SQL> SET SERVEROUTPUT ON SIZE 5000
SQL> CALL dbms_java.set_output(5000);
The output is displayed at the end of the call.
Calling Java Methods in Oracle Database
3-19
Calling Java in the Database Directly
Calling Java in the Database Directly
Oracle Database 10g introduces new features for calling Java stored procedures and
functions. In releases prior to Oracle Database 10g, calling Java stored procedures and
functions from a database client required JDBC calls to the associated PL/SQL
wrappers. Each wrapper had to be manually published with a SQL signature and a
Java implementation. This had the following disadvantages:
■
A separate step was required for publishing the SQL signatures for Java methods.
■
The signatures permitted only Java types with SQL equivalents.
■
Exceptions issued in Java were not properly returned.
■
Only a single method invocation could be performed for each database round trip.
To remedy these deficiencies, a simple API has been implemented to directly call
static Java stored procedures and functions. This new functionality is useful for
general applications, but is particularly useful for Web services.
Classes for the simple API are located in the oracle.jpub.reflect package.
Import this package into the client-side code.
The following is the Java interface for the API:
public class Client
{
public static String getSignature(Class[]);
public static Object invoke(Connection, String, String, String, Object[]);
public static Object invoke(Connection, String, String, Class[], Object[]);
}
As an example, consider a call to the following method in the server:
public String oracle.sqlj.checker.JdbcVersion.to_string();
You can call the method, as follows:
Connection conn = ...;
String serverSqljVersion = (String)
Client.invoke(conn, "oracle.sqlj.checker.JdbcVersion","to_string", new Class[]{},
new Object[]{});
The Class[] array is for the method parameter types and the Object[] array is for
the parameter values. In this case, because to_string has no parameters, the arrays
are empty.
Note the following:
■
■
Any serializable type, such as int[] and String[], can be passed as an
argument.
As an optimization, parameter values can be represented as String:
String sig = oracle.jpub.reflect.Client.getSignature(new Class[]{});
...
Client.invoke(conn, "oracle.sqlj.checker.JdbcVersion", "to_string",sig, new
Object[]{});
■
The semantics of this API are different from the semantics for calling stored
procedures or functions through a PL/SQL wrapper, in the following ways:
–
Arguments cannot be OUT or IN OUT. Returned values must all be part of the
function result.
3-20 Oracle Database Java Developer’s Guide
Calling Java in the Database Directly
–
Exceptions are properly returned.
–
The method invocation uses invoker's rights. There is no tuning to obtain the
definer's rights.
Calling Java Methods in Oracle Database
3-21
Calling Java in the Database Directly
3-22 Oracle Database Java Developer’s Guide
4
Java Installation and Configuration
This chapter describes how to install and configure of Oracle JVM. It also describes
how to enable the Java client. This chapter covers the following topics:
■
Initializing a Java-Enabled Database
■
Configuring Oracle JVM
■
Using The DBMS_JAVA Package
■
Enabling the Java Client
■
Two-Tier Duration for Java Session State
■
Setting System Properties
Initializing a Java-Enabled Database
If you install Oracle Database with Oracle JVM option, then the database is
Java-enabled. That is, it is ready to run Java stored procedures, Java Database
Connectivity (JDBC), and SQLJ.
This section contains the following topics:
■
Configuring with Oracle Database Template
■
Modifying an Existing Oracle Database to Include Oracle JVM
Configuring with Oracle Database Template
Configure Oracle JVM option within the database template. This is the recommended
method for Java installation.
The Database Configuration Assistant enables you to create database templates for
defining what each database instance installation will contain. Choose Oracle JVM
option to have the Java platform installed within your database.
Modifying an Existing Oracle Database to Include Oracle JVM
If you have already installed Oracle Database without Oracle JVM, then you can add
Java to your database through the modify mode of the Database Configuration
Assistant of Oracle Database 10g. The modify mode enables you to choose the features,
such as Oracle JVM, that you would like to install on top of an existing Oracle
Database instance.
Java Installation and Configuration 4-1
Configuring Oracle JVM
Configuring Oracle JVM
Before you install Oracle JVM as part of your normal Oracle Database installation, you
need to ensure that the configuration requirements for Oracle JVM are fulfilled. The
main configuration for Java classes within Oracle Database includes configuring the:
■
Java memory requirements
You must have at least 50 MB of JAVA_POOL_SIZE and 96 MB of
SHARED_POOL_SIZE.
See Also:
■
"Java Memory Usage" on page 9-4
Database processes
You must decide whether to use dedicated server processes or shared server
processes for your database server.
Using The DBMS_JAVA Package
Installing Oracle JVM creates the DBMS_JAVA PL/SQL package. Some entry points of
DBMS_JAVA are for external use. That is, these entry points are used by developers.
Other entry points are only for internal use. The corresponding Java class, DbmsJava,
provides methods for accessing database functionality from Java.
See Also:
Appendix A, "DBMS_JAVA Package"
Enabling the Java Client
To run Java between the client and server, your must perform the following:
1.
Install J2SE on the Client
2.
Set Up Environment Variables
3.
Test Install with Samples
Install J2SE on the Client
The client requires Java Development Kit (JDK) 1.5.2 or later. To confirm the version of
JDK you are using, run the following commands on the command line:
$ which java
/usr/local/j2se1.5.2/bin/java
$ which javac
/usr/local/j2se1.5.2/bin/javac
$ java -version
java version "1.5.2"
Set Up Environment Variables
After installing JDK on your client, add the directory path to the following
environment variables:
■
$JAVA_HOME
This variable must be set to the top directory of the installed JDK base.
4-2 Oracle Database Java Developer’s Guide
Enabling the Java Client
■
$PATH
This variable must include $JAVA_HOME/bin.
■
$LD_LIBRARY_PATH
This variable must include $JAVA_HOME/lib.
JAR Files Necessary for Java2 Clients
To ensure that the Java client successfully communicates with the server, include the
following files in the CLASSPATH:
■
For JDK 1.5.2, include $JAVA_HOME/lib/dt.jar
■
For JRE 1.5.2, include $JAVA_HOME/lib/rt.jar
■
■
■
■
■
For any interaction with JDBC, include
$ORACLE_HOME/jdbc/lib/classes12.zip
For any client that uses SSL, include $ORACLE_HOME/jlib/jssl-1_2.jar and
$ORACLE_HOME/jlib/javax-ssl-1_2.jar
For any client that uses the Java Transaction API (JTA) functionality, include
$ORACLE_HOME/jlib/jta.jar
For any client that uses the Java Naming and Directory Interface (JNDI)
functionality, include $ORACLE_HOME/jlib/jndi.jar
If you are using the accelerator for native compilation, include
$JAVA_HOME/lib/tools.jar
JAR Files Included for Clients that use SQLJ
You must include the $ORACLE_HOME/sqlj/lib/translator.zip file for SQLJ.
In addition to this file, add the appropriate runtimeX.zip file, as follows:
■
■
■
For a Java client using the current release of JDBC, include
$ORACLE_HOME/sqlj/lib/runtime12.zip
For a Java2 Platform, Enterprise Edition (J2EE) client using the current release of
JDBC, include $ORACLE_HOME/sqlj/lib/runtime12ee.zip
For any JDK client using JDBC 8.1.7 or earlier version, include
$ORACLE_HOME/sqlj/lib/runtime.zip
Server Application Development on the Client
If you develop and compile your server applications on the client and want to use the
same Java Archive (JAR) files that are loaded on the server, then include
$ORACLE_HOME/lib/aurora.zip in CLASSPATH. This is not required for running
Java clients.
Test Install with Samples
When you install Oracle Database with Oracle JVM option, a set of samples is also
installed and available in the $ORACLE_HOME/javavm/demo directory. These
samples can be compiled and run as a test of your installation.
If these samples do not compile or run, then the environment may be incorrectly set.
Similarly, if these samples compile and run, but a code written by you does not, then a
problem exists within the build environment or code.
Java Installation and Configuration 4-3
Two-Tier Duration for Java Session State
When verifying your installation, it is important that you run
these examples using the supplied makefiles.
Note:
Verify that the samples work before using more complex build environments, such as
Visual Cafe, JDeveloper, or VisualAge.
Two-Tier Duration for Java Session State
Prior to 11g release 1 (11.1), Java session state was single-tier, which included all
values associated with running Java, such as System property values and static
variable values, the set of classes loaded during the session and so on. The duration of
this state used to start with the first invocation of a Java method in the RDBMS session
and it used to last till JVM exited, either due to a call to java.lang.System.exit or
similar OracleRuntime methods, an uncaught exception, a fatal error, or the end of
the RDBMS session. This required modifying Java code and also failed to fully
complete the termination of the session before the end of the RDBMS call. This made it
impossible to start a new Java session within the same call.
Starting with 11g release 1 (11.1), Java session state is split into two tiers. One tier has a
longer duration and it encompasses the duration of the other tier. The duration of the
shorter tier is the same as before, that is, it starts when a Java method is invoked and
ends when JVM exits. The duration of the longer tier starts when a Java method is
invoked in the RDBMS session for the first time. This session lasts until the RDBMS
session ends or the session is explicitly terminated by a call to the function
dbms_java.endsession_and_related_state. This is addressed by the addition
of the following two PL/SQL functions to the DBMS_JAVA package, which account for
the two kinds of Java session duration:
■
FUNCTION endsession RETURN VARCHAR2;
This function clears any Java session state remaining from previous execution of
Java in the current RDBMS session. The return value is a message indicating the
action taken.
■
FUNCTION endsession_and_related_state RETURN VARCHAR2;
This function clears any Java session state remaining from previous execution of
Java in the current RDBMS session and all supporting data related to running
Java, such as property settings and output specifications. The return value is a
message indicating the action taken.
Most of the values associated with running Java remain in the shorter tier. The values
that can be useful for multiple invocations of JVM have been moved to the longer tier.
For example, the system property values established by dbms_java.set_property
and the output redirection specifications.
See Also: "Setting System Properties" on page 4-4 and "Redirecting
Output on the Server" on page 3-14.
Setting System Properties
Within an RDBMS session you can maintain a set of values that are added to the
system properties whenever a Java session is started in the RDBMS session. This set of
values remains valid for the duration of the longer tier of Java session state, which is
typically the same as the duration the RDBMS session.
4-4 Oracle Database Java Developer’s Guide
Setting System Properties
See Also:
"Two-Tier Duration for Java Session State" on page 4-4
There is a set of PL/SQL functions in the DBMS_JAVA package for setting, retrieving,
removing and displaying key value pairs in an internal, RDBMS session duration
table, where both elements of a pair are strings (VARCHAR2) and there is at most one
pair for a given key. These functions are as follows:
■
set_property
■
get_property
■
remove_property
■
show_property
set_property
This function enables you to establish a value for a system property that is then used
for the duration of the current RDBMS session, whenever a Java session is initialized.
The first argument is the name of the property and the second is the value to be
established for it. The return value for set_property is null unless there is some
error. For example, if an attempt is made to set a value for a prescribed property, then
an error message is returned.
FUNCTION set_property(name VARCHAR2, value VARCHAR2) RETURN VARCHAR2;
get_property
This function returns any value previously established by set_property. It returns
null if there is no such value.
FUNCTION get_property(name VARCHAR2) RETURN VARCHAR2;
remove_property
This function removes any value previously established by set_property. The
return value is null unless an error occurred, in which case an error message is
returned.
FUNCTION remove_property(name VARCHAR2) RETURN VARCHAR2;
show_property
This function displays a message of the form name = value for the input name, or
for all established property bindings, if name is null. The return value for this function
is null on successful completion, otherwise it is an error message. The output is
displayed to wherever you have currently directed your Java output.
FUNCTION show_property(name VARCHAR2) RETURN VARCHAR2;
Before initializing the Java session, the values from this table are added to the set of
default system property values already maintained by Oracle JVM. When you run a
Java method by using the command-line interface, the values determined by the -D
option, if present, override the values set in the table. As soon as you terminate the
Java session, the values established by the -D option become obsolete and the keys are
set to the original values as present in the table.
Java Installation and Configuration 4-5
Setting System Properties
4-6 Oracle Database Java Developer’s Guide
5
Developing Java Stored Procedures
Oracle JVM has all the features you need to build a new generation of enterprise-wide
applications at a low cost. The most important feature is the support for stored
procedures. Using stored procedures, you can implement business logic at the server
level, thereby improving application performance, scalability, and security.
This chapter contains the following sections:
■
Stored Procedures and Run-Time Contexts
■
Advantages of Stored Procedures
■
Java Stored Procedures Steps
Stored Procedures and Run-Time Contexts
Stored procedures are Java methods published to SQL and stored in the database for
general use. To publish Java methods, you write call specifications, which map Java
method names, parameter types, and return types to their SQL counterparts.
Unlike a wrapper, which adds another layer of execution, a call specification publishes
the existence of a Java method. As a result, when you call the method through its call
specification, the run-time system dispatches the call with minimal overhead.
When called by client applications, a stored procedure can accept arguments, reference
Java classes, and return Java result values.
Figure 5–1 shows a stored procedure being called by various applications.
Figure 5–1 Calling a Stored Procedure
Applications
Oracle Database
hire_emp(...);
Stored Procedure
hire_emp(...);
hire_emp(...)
hire_emp(...);
Except for graphical user interface (GUI) methods, Oracle JVM can run any Java
method as a stored procedure. The run-time contexts are:
■
Functions and Procedures
Developing Java Stored Procedures
5-1
Stored Procedures and Run-Time Contexts
■
Database Triggers
■
Object-Relational Methods
Functions and Procedures
Functions and procedures are named blocks that encapsulate a sequence of statements.
They are building blocks that you can use to construct modular, maintainable
applications.
Generally, you use a procedure to perform an action and a function to compute a
value. Therefore, you use procedure call specifications for void Java methods and
function call specifications for value-returning methods.
Only top-level and package-level PL/SQL functions and procedures can be used as
call specifications. When you define them using the SQL CREATE FUNCTION, CREATE
PROCEDURE, or CREATE PACKAGE statement, they are stored in the database, where
they are available for general use.
Java methods published as functions and procedures must be invoked explicitly. They
can accept arguments and are callable from:
■
SQL data manipulation language (DML) statements
■
SQL CALL statements
■
PL/SQL blocks, subprograms, and packages
Database Triggers
A database trigger is a stored procedure that is associated with a specific table or view.
Oracle Database calls the trigger automatically whenever a given DML operation
modifies the table or view.
A trigger has the following parts:
■
A triggering event, which is generally a DML operation
■
An optional trigger constraint
■
A trigger action
When the event occurs, the trigger is called. A CALL statement in the trigger calls a
Java method through the call specification of the method, to perform the action.
Database triggers are used to enforce complex business rules, derive column values
automatically, prevent invalid transactions, log events transparently, audit
transactions, and gather statistics.
Object-Relational Methods
A SQL object type is a user-defined composite data type that encapsulates a set of
variables, called attributes, with a set of operations, called methods, which can be
written in Java. The data structure formed by the set of attributes is public. However,
as a good programming practice, you must ensure that your application does not
manipulate these attributes directly and uses the set of methods provided.
You can create an abstract template for some real-world object as a SQL object type.
The template specifies only those attributes and methods that the object will need in
the application environment. At run time, when you fill the data structure with values,
you create an instance of the object type. You can create as many instances as required.
5-2 Oracle Database Java Developer’s Guide
Advantages of Stored Procedures
Typically, an object type corresponds to some business entity, such as a purchase order.
To accommodate a variable number of items, object types can use a VARRAY, a nested
table, or both.
For example, the purchase order object type can contain a variable number of line
items.
Advantages of Stored Procedures
Stored procedures offer several advantages. The following advantages are covered in
this section:
■
Performance
■
Productivity and Ease of Use
■
Scalability
■
Maintainability
■
Interoperability
■
Replication
■
Security
Performance
Stored procedures are compiled once and stored in an executable form. As a result,
procedure calls are quick and efficient. Executable code is automatically cached and
shared among users. This lowers memory requirements and invocation overhead.
By grouping SQL statements, a stored procedure allows the statements to be processed
with a single call. This reduces network traffic and improves round-trip response time.
Additionally, stored procedures enable you to take advantage of the computing
resources of the server. For example, you can move computation-bound procedures
from client to server, where they will run faster. Stored functions enhance performance
by running application logic within the server.
Productivity and Ease of Use
By designing applications around a common set of stored procedures, you can avoid
redundant coding and increase the productivity. Moreover, stored procedures let you
extend the functionality of the database.
You can use the Java integrated development environment (IDE) of your choice to
create stored procedures. They can be called by standard Java interfaces, such as Java
Database Connectivity (JDBC), and by programmatic interfaces and development
tools, such as SQLJ, Oracle Call Interface (OCI), Pro*C/C++, and JDeveloper.
This broad access to stored procedures lets you share business logic across
applications. For example, a stored procedure that implements a business rule can be
called from various client-side applications, all of which can share that business rule.
In addition, you can leverage the Java facilities of the server while continuing to write
applications for a preferred programmatic interface.
Note:
Refer to "Ease-of-Use Interface" for more information.
Developing Java Stored Procedures
5-3
Advantages of Stored Procedures
Scalability
Java in the database inherits the scalable session model of Oracle Database. Stored
procedures increase scalability by isolating application processing on the server. In
addition, automatic dependency tracking for stored procedures helps in developing
scalable applications.
Maintainability
After a stored procedure is validated, you can use it with confidence in any number of
applications. If its definition changes, then only the procedure is affected, not the
applications that call it. This simplifies maintenance and enhancement. Also,
maintaining a procedure on the server is easier than maintaining copies on different
client computers.
Interoperability
Java in Oracle Database fully conforms to the Java Language Specification (JLS) and
furnishes all the advantages of a general-purpose, object-oriented programming
language. Also, as with PL/SQL, Java provides full access to Oracle data. As a result,
any procedure that is written in PL/SQL can also be written in Java.
PL/SQL stored procedures complement Java stored procedures. Typically, SQL
programmers who want procedural extensions favor PL/SQL, and Java programmers
who want easy access to Oracle data favor Java.
Oracle Database allows a high degree of interoperability between Java and PL/SQL.
Java applications can call PL/SQL stored procedures using an embedded JDBC driver.
Conversely, PL/SQL applications can call Java stored procedures directly.
Replication
With Oracle Advanced Replication, you can replicate stored procedures from one
Oracle Database instance to another. This enables you to use stored procedures to
implement a central set of business rules. Once you write the procedures, you can
replicate and distribute them to work groups and branch offices throughout the
company. In this way, you can revise policies on a central server rather than on
individual servers.
Security
Security is a large arena that includes:
■
■
■
Network security for the connection
Access and execution control of operating system resources or of JVM and
user-defined classes
Bytecode verification of JAR files imported from an external source.
In Oracle Database, all classes are loaded into a secure database and, therefore, are
untrusted. A user requires the appropriate permissions to access classes and operating
system resources. Likewise, all stored procedures are secured against other users. You
can grant the EXECUTE database privilege to users who need to access the stored
procedures.
You can restrict access to Oracle data by allowing users to manipulate the data only
through stored procedures that run with their definer's privileges. For example, you
5-4 Oracle Database Java Developer’s Guide
Java Stored Procedures Steps
can allow access to a procedure that updates a database table, but deny access to the
table itself.
See Also: Chapter 10, "Security for Oracle Database Java
Applications"
Java Stored Procedures Steps
You can run Java stored procedures in the same way as PL/SQL stored procedures.
Normally, a call to a Java stored procedure is a result of database manipulation,
because it is usually the result of a trigger or SQL DML call. To call a Java stored
procedure, you must publish it through a call specification.
Before you can call Java stored procedures, you must load them into Oracle Database
instance and publish them to SQL. Loading and publishing are separate tasks. Many
Java classes, which are referenced only by other Java classes, are never published.
To load Java stored procedures automatically, you can use the loadjava
command-line tool. It loads Java source, class, and resource files into a
system-generated database table, and then uses the SQL CREATE JAVA {SOURCE |
CLASS | RESOURCE} statement to load the Java files into Oracle Database instance.
You can upload Java files from file systems, popular Java IDEs, intranets, or the
Internet.
The following steps are involved in creating, loading, and calling Java stored
procedures:
■
Step 1: Create or Reuse the Java Classes
■
Step 2: Load and Resolve the Java Classes
■
Step 3: Publish the Java Classes
■
Step 4: Call the Stored Procedures
■
Step 5: Debug the Stored Procedures, if Necessary
Note: To load Java stored procedures manually, you can use the
CREATE JAVA statements. For example, in SQL*Plus, you can use the
CREATE JAVA CLASS statement to load Java class files from local
BFILE and LOB columns into Oracle Database.
Step 1: Create or Reuse the Java Classes
Use a preferred Java IDE to create classes, or reuse existing classes that meet your
requirements. Oracle Database supports many Java development tools and client-side
programmatic interfaces. For example, Oracle JVM accepts programs developed in
popular Java IDEs, such as Oracle JDeveloper, Symantec Visual Cafe, and Borland
JBuilder.
In the following example, you create the public class Oscar. It has a single method
named quote(), which returns a quotation from Oscar Wilde.
public class Oscar
{
// return a quotation from Oscar Wilde
public static String quote()
{
return "I can resist everything except temptation.";
}
Developing Java Stored Procedures
5-5
Java Stored Procedures Steps
}
Save the class as Oscar.java. Using a Java compiler, compile the .java file on your
client system, as follows:
javac Oscar.java
The compiler outputs a Java binary file, in this case, Oscar.class.
Step 2: Load and Resolve the Java Classes
Using the loadjava tool, you can load Java source, class, and resource files into
Oracle Database instance, where they are stored as Java schema objects. You can run
loadjava from the command line or from an application, and you can specify several
options including a resolver.
In the following example, loadjava connects to the database using the default JDBC
OCI driver. You must specify the user name and password. By default, the Oscar class
is loaded into the schema of the user you log in as, in this case, scott.
$ loadjava -user scott Oscar.class
Password: password
When you call the quote() method, the server uses a resolver to search for
supporting classes, such as String. In this case, the default resolver is used. The
default resolver first searches the current schema and then the SYS schema, where all
the core Java class libraries reside. If necessary, you can specify different resolvers.
Step 3: Publish the Java Classes
For each Java method that can be called from SQL or JDBC, you must write a call
specification, which exposes the top-level entry point of the method to Oracle
Database. Typically, only a few call specifications are needed. If preferred, you can
generate these call specifications using Oracle JDeveloper.
In the following example, from SQL*Plus, you connect to the database and then define
a top-level call specification for the quote() method:
SQL> connect scott
Enter password: password
SQL> CREATE FUNCTION oscar_quote RETURN VARCHAR2
2 AS LANGUAGE JAVA
3 NAME 'Oscar.quote() return java.lang.String';
See Also: Chapter 6, "Publishing Java Classes With Call
Specifications"
Step 4: Call the Stored Procedures
You can call Java stored procedures from JDBC, SQLJ, and all third party languages
that can access the call specification. Using the SQL CALL statement, you can also call
the stored procedures from the top level, for example, from SQL*Plus. Stored
procedures can also be called from database triggers.
In the following example, you declare a SQL*Plus host variable:
SQL> VARIABLE theQuote VARCHAR2(50);
5-6 Oracle Database Java Developer’s Guide
Java Stored Procedures Steps
Then, you call the function oscar_quote(), as follows:
SQL> CALL oscar_quote() INTO :theQuote;
SQL> PRINT theQuote;
THEQUOTE
-------------------------------------------------I can resist everything except temptation.
See Also:
Chapter 7, "Calling Stored Procedures"
You can also call the Java class using the ojvmjava tool.
See Also:
"The ojvmjava Tool" on page 11-19
Step 5: Debug the Stored Procedures, if Necessary
Debugging the stored procedures is mandatory. Your Java stored procedures run
remotely on a server that resides on a separate computer. However, the JDK debugger,
jdb, cannot debug remote Java programs. As a result, you need to debug your stored
procedures on your client computer before you load them on to the database.
See Also:
"Debugging Server Applications" on page 3-13
Developing Java Stored Procedures
5-7
Java Stored Procedures Steps
5-8 Oracle Database Java Developer’s Guide
6
Publishing Java Classes With Call
Specifications
When you load a Java class into the database, its methods are not published
automatically, because Oracle Database does not know which methods are safe entry
points for calls from SQL. To publish the methods, you must write call specifications,
which map Java method names, parameter types, and return types to their SQL
counterparts. This chapter describes how to publish Java classes with call
specifications.
This chapter contains the following sections:
■
Understanding Call Specifications
■
Defining Call Specifications
■
Writing Top-Level Call Specifications
■
Writing Packaged Call Specifications
■
Writing Object Type Call Specifications
Understanding Call Specifications
To publish Java methods, you write call specifications. For a given Java method, you
declare a function or procedure call specification using the SQL CREATE FUNCTION or
CREATE PROCEDURE statement. Inside a PL/SQL package or SQL object type, you use
similar declarations.
You publish Java methods that return a value as functions or procedures and void
Java methods as procedures. The function or procedure body contains the LANGUAGE
JAVA clause. This clause records information about the Java method including its full
name, its parameter types, and its return type. Mismatches are detected only at run
time.
Figure 6–1 shows applications calling the Java method through its call specification,
that is, by referencing the name of the call specification. The run-time system looks up
the call specification definition in the Oracle data dictionary and runs the
corresponding Java method.
Publishing Java Classes With Call Specifications
6-1
Defining Call Specifications
Figure 6–1 Calling a Java Method
Oracle Database
Application
Call
Spec
Java
method
Data
Dictionary
As an alternative, you can use the native Java interface to directly call Java methods in
the database from a Java client.
See Also:
"Using the Client-Side Stub" on page 3-10
Defining Call Specifications
A call specification and the Java method it publishes must reside in the same schema,
unless the Java method has a PUBLIC synonym. You can declare the call specification
as a:
■
Standalone PL/SQL function or procedure
■
Packaged PL/SQL function or procedure
■
Member method of a SQL object type
A call specification exposes the top-level entry point of a Java method to Oracle
Database. As a result, you can publish only public static methods. However, there
is an exception. You can publish instance methods as member methods of a SQL object
type.
Packaged call specifications perform as well as top-level call specifications. As a result,
to ease maintenance, you may want to place call specifications in a package body. This
will help you to modify call specifications without invalidating other schema objects.
Also, you can overload the call specifications.
This section covers the following topics:
■
Setting Parameter Modes
■
Mapping Data Types
■
Using the Server-Side Internal JDBC Driver
Setting Parameter Modes
In Java and other object-oriented languages, a method cannot assign values to objects
passed as arguments. When calling a method from SQL or PL/SQL, to change the
value of an argument, you must declare it as an OUT or IN OUT parameter in the call
specification. The corresponding Java parameter must be an array with only one
element.
6-2 Oracle Database Java Developer’s Guide
Defining Call Specifications
You can replace the element value with another Java object of the appropriate type, or
you can modify the value if the Java type permits. Either way, the new value
propagates back to the caller. For example, you map a call specification OUT parameter
of the NUMBER type to a Java parameter declared as float[] p, and then assign a
new value to p[0].
A function that declares OUT or IN OUT parameters cannot be
called from SQL data manipulation language (DML) statements.
Note:
Mapping Data Types
In a call specification, the corresponding SQL and Java parameters and function results
must have compatible data types.
Table 6–1 lists the legal data type mappings. Oracle Database converts between the
SQL types and Java classes automatically.
Table 6–1
Legal Data Type Mappings
SQL Type
Java Class
CHAR, LONG, VARCHAR2
oracle.sql.CHAR
java.lang.String
java.sql.Date
java.sql.Time
java.sql.Timestamp
java.lang.Byte
java.lang.Short
java.lang.Integer
java.lang.Long
java.lang.Float
java.lang.Double
java.math.BigDecimal
byte, short, int, long, float, double
DATE
oracle.sql.DATE
java.sql.Date
java.sql.Time
java.sql.Timestamp
java.lang.String
NUMBER
oracle.sql.NUMBER
java.lang.Byte
java.lang.Short
java.lang.Integer
java.lang.Long
java.lang.Float
java.lang.Double
java.math.BigDecimal
byte, short, int, long, float, double
OPAQUE
oracle.sql.OPAQUE
Publishing Java Classes With Call Specifications
6-3
Defining Call Specifications
Table 6–1 (Cont.) Legal Data Type Mappings
SQL Type
Java Class
RAW, LONG RAW
oracle.sql.RAW
byte[]
ROWID
oracle.sql.CHAR
oracle.sql.ROWID
java.lang.String
BFILE
oracle.sql.BFILE
BLOB
oracle.sql.BLOB
oracle.jdbc2.Blob
CLOB, NCLOB
oracle.sql.CLOB
oracle.jdbc2.Clob
OBJECT
oracle.sql.STRUCT
Object types
java.sql.Struct
java.sql.SqlData
oracle.sql.ORAData
REF
oracle.sql.REF
Reference types
java.sql.Ref
oracle.sql.ORAData
TABLE, VARRAY
oracle.sql.ARRAY
Nested table types and
VARRAY types
java.sql.Array
any of the preceding SQL
types
oracle.sql.CustomDatum
oracle.sql.ORAData
oracle.sql.Datum
You also need to consider the following:
■
■
■
■
The UROWID type and the NUMBER subtypes, such as INTEGER and REAL, are not
supported.
A value larger than 32 KB cannot be retrieved from a LONG or LONG RAW column
into a Java stored procedure.
Java wrapper classes, such as java.lang.Byte and java.lang.Short, are
useful for returning NULL from SQL.
The following member must be defined when using the
oracle.sql.CustomDatum class to declare parameters:
public static oracle.sql.CustomDatumFactory.getFactory();
■
■
oracle.sql.Datum is an abstract class. The value passed to a parameter of type
oracle.sql.Datum must belong to a Java class compatible with the SQL type.
Similarly, the value returned by a method with the return type
oracle.sql.Datum must belong to a Java class compatible with the SQL type.
The mappings to oracle.sql classes are optimal, because they preserve data
formats and do not require any character set conversions, apart from the usual
network conversions. These classes are especially useful in applications that move
data between SQL and Java.
6-4 Oracle Database Java Developer’s Guide
Defining Call Specifications
Using the Server-Side Internal JDBC Driver
Java Database Connectivity (JDBC) enables you establish a connection to the database
using the DriverManager class, which manages a set of JDBC drivers. You can use
the getConnection() method after loading the JDBC drivers. When the
getConnection() method finds the right driver, it returns a Connection object
that represents a database session. All SQL statements are run within the context of
that session.
However, the server-side internal JDBC driver runs within a default session and a
default transaction context. As a result, you are already connected to the database, and
all your SQL operations are part of the default transaction. You need not register the
driver because it comes preregistered. To get a Connection object, run the following
line of code:
Connection conn = DriverManager.getConnection("jdbc:default:connection:");
Use the Statement class for SQL statements that do not take IN parameters and are
run only once. When called on a Connection object, the createStatement()
method returns a new Statement object, as follows:
String sql = "DROP " + object_type + " " + object_name;
Statement stmt = conn.createStatement();
stmt.executeUpdate(sql);
Use the PreparedStatement class for SQL statements that take IN parameters or are
run more than once. The SQL statement, which can contain one or more parameter
placeholders, is precompiled. A question mark (?) serves as a placeholder. When called
on a Connection object, the prepareStatement() method returns a new
PreparedStatement object, which contains the precompiled SQL statement. For
example:
String sql = "DELETE FROM dept WHERE deptno = ?";
PreparedStatement pstmt = conn.prepareStatement(sql);
pstmt.setInt(1, deptID);
pstmt.executeUpdate();
A ResultSet object contains SQL query results, that is, the rows that meet the search
condition. You can use the next() method to move to the next row, which then
becomes the current row. You can use the getXXX() methods to retrieve column
values from the current row. For example:
String sql = "SELECT COUNT(*) FROM " + tabName;
int rows = 0;
Statement stmt = conn.createStatement();
ResultSet rset = stmt.executeQuery(sql);
while (rset.next())
{
rows = rset.getInt(1);
}
A CallableStatement object lets you call stored procedures. It contains the call
text, which can include a return parameter and any number of IN, OUT, and IN OUT
parameters. The call is written using an escape clause, which is delimited by braces
({}). As the following examples show, the escape syntax has three forms:
// parameterless stored procedure
CallableStatement cstmt = conn.prepareCall("{CALL proc}");
// stored procedure
CallableStatement cstmt = conn.prepareCall("{CALL proc(?,?)}");
Publishing Java Classes With Call Specifications
6-5
Writing Top-Level Call Specifications
// stored function
CallableStatement cstmt = conn.prepareCall("{? = CALL func(?,?)}");
Important Points
When developing JDBC applications that access stored procedures, you need to
consider the following:
■
■
■
■
■
The server-side internal JDBC driver runs within a default session and default
transaction context. You are already connected to the database, and all your SQL
operations are part of the default transaction. Note that this transaction is a local
transaction and not part of a global transaction, such as that implemented by Java
Transaction API (JTA) or Java Transaction Service (JTS).
Statements and result sets persist across calls and their finalizers do not release
database cursors. To avoid running out of cursors, close all statements and result
sets after you have finished using them. Alternatively, you can ask your DBA to
raise the limit set by the initialization parameter, OPEN_CURSORS.
The server-side internal JDBC driver does not support auto-commits. As a result,
your application must explicitly commit or roll back database changes.
You cannot connect to a remote database using the server-side internal JDBC
driver. You can connect only to the server running your Java program. For
server-to-server connections, use the server-side JDBC Thin driver. For
client/server connections, use the client-side JDBC Thin or JDBC Oracle Call
Interface (OCI) driver.
You cannot close the physical connection to the database established by the
server-side internal JDBC driver. However, if you call the close() method on the
default connection, all connection instances that reference the same object are
cleaned up and closed. To get a new connection object, you must call
getConnection() again.
See Also:
Oracle Database JDBC Developer's Guide and Reference
Writing Top-Level Call Specifications
In SQL*Plus, you can define top-level call specifications interactively, using the
following syntax:
CREATE [OR REPLACE]
{ PROCEDURE procedure_name [(param[, param]...)]
| FUNCTION function_name [(param[, param]...)] RETURN sql_type}
[AUTHID {DEFINER | CURRENT_USER}]
[PARALLEL_ENABLE]
[DETERMINISTIC]
{IS | AS} LANGUAGE JAVA
NAME 'method_fullname (java_type_fullname[, java_type_fullname]...)
[return java_type_fullname]';
where param is represented by the following syntax:
parameter_name [IN | OUT | IN OUT] sql_type
The AUTHID clause determines whether a stored procedure runs with the privileges of
its definer or invoker, which is the default, and whether its unqualified references to
schema objects are resolved in the schema of the definer or invoker. You can override
6-6 Oracle Database Java Developer’s Guide
Writing Top-Level Call Specifications
the default behavior by specifying DEFINER. However, you cannot override the
loadjava option -definer by specifying CURRENT_USER.
The PARALLEL_ENABLE option declares that a stored function can be used safely in
the slave sessions of parallel DML evaluations. The state of a main session is never
shared with slave sessions. Each slave session has its own state, which is initialized
when the session begins. The function result should not depend on the state of session
variables. Otherwise, results might vary across sessions.
The DETERMINISTIC option helps the optimizer avoid redundant function calls. If a
stored function was called previously with the same arguments, then the optimizer
can decide to use the previous result. The function result should not depend on the
state of session variables or schema objects. Otherwise, results can vary across calls.
Only DETERMINISTIC functions can be called from a function-based index or a
materialized view that has query-rewrite enabled.
The string in the NAME clause uniquely identifies the Java method. The fully-qualified
Java names and the call specification parameters, which are mapped by position, must
correspond. However, this rule does not apply to the main() method. If the Java
method does not take any arguments, then write an empty parameter list for it, but not
for the function or procedure.
Write fully-qualified Java names using the dot notation. The following example shows
that the fully-qualified names can be broken across lines at dot boundaries:
artificialIntelligence.neuralNetworks.patternClassification.
RadarSignatureClassifier.computeRange()
This section provides the following examples:
■
Example 6–1, "Publishing a Simple JDBC Stored Procedure"
■
Example 6–2, "Publishing the main() Method"
■
Example 6–3, "Publishing a Method That Returns an Integer Value"
■
Example 6–4, "Publishing a Method That Switches the Values of Its Arguments"
Example 6–1 Publishing a Simple JDBC Stored Procedure
Assume that the executable for the following Java class has been loaded into the
database:
import java.sql.*;
import java.io.*;
import oracle.jdbc.*;
public class GenericDrop
{
public static void dropIt(String object_type, String object_name)
throws SQLException
{
// Connect to Oracle using JDBC driver
Connection conn = DriverManager.getConnection("jdbc:default:connection:");
// Build SQL statement
String sql = "DROP " + object_type + " " + object_name;
try
{
Statement stmt = conn.createStatement();
stmt.executeUpdate(sql);
stmt.close();
}
catch (SQLException e)
Publishing Java Classes With Call Specifications
6-7
Writing Top-Level Call Specifications
{
System.err.println(e.getMessage());
}
}
}
The GenericDrop class has one method, dropIt(), which drops any kind of schema
object. For example, if you pass the table and emp arguments to dropIt(), then the
method drops the database table emp from your schema.
The call specification for the dropIt() method is as follows:
CREATE OR REPLACE PROCEDURE drop_it (obj_type VARCHAR2, obj_name VARCHAR2)
AS LANGUAGE JAVA
NAME 'GenericDrop.dropIt(java.lang.String, java.lang.String)';
Note that you must fully qualify the reference to String. The java.lang package is
automatically available to Java programs, but must be named explicitly in the call
specifications.
Example 6–2 Publishing the main() Method
As a rule, Java names and call specification parameters must correspond. However,
that rule does not apply to the main() method. Its String[] parameter can be
mapped to multiple CHAR or VARCHAR2 call specification parameters. Consider the
main() method in the following class, which displays its arguments:
public class EchoInput
{
public static void main (String[] args)
{
for (int i = 0; i < args.length; i++)
System.out.println(args[i]);
}
}
To publish main(), write the following call specification:
CREATE OR REPLACE PROCEDURE echo_input(s1 VARCHAR2, s2 VARCHAR2, s3 VARCHAR2)
AS LANGUAGE JAVA
NAME 'EchoInput.main(java.lang.String[])';
You cannot impose constraints, such as precision, size, and NOT NULL, on the call
specification parameters. As a result, you cannot specify a maximum size for the
VARCHAR2 parameters. However, you must do so for VARCHAR2 variables, as in:
DECLARE last_name VARCHAR2(20); -- size constraint required
Example 6–3 Publishing a Method That Returns an Integer Value
In the following example, the rowCount() method, which returns the number of
rows in a given database table, is published:
import java.sql.*;
import java.io.*;
import oracle.jdbc.*;
public class RowCounter
{
public static int rowCount (String tabName) throws SQLException
{
6-8 Oracle Database Java Developer’s Guide
Writing Top-Level Call Specifications
Connection conn = DriverManager.getConnection("jdbc:default:connection:");
String sql = "SELECT COUNT(*) FROM " + tabName;
int rows = 0;
try
{
Statement stmt = conn.createStatement();
ResultSet rset = stmt.executeQuery(sql);
while (rset.next())
{
rows = rset.getInt(1);
}
rset.close();
stmt.close();
}
catch (SQLException e)
{
System.err.println(e.getMessage());
}
return rows;
}
}
NUMBER subtypes, such as INTEGER, REAL, and POSITIVE, are not allowed in a call
specification. As a result, in the following call specification, the return type is NUMBER
and not INTEGER:
CREATE FUNCTION row_count (tab_name VARCHAR2) RETURN NUMBER
AS LANGUAGE JAVA
NAME 'RowCounter.rowCount(java.lang.String) return int';
Example 6–4 Publishing a Method That Switches the Values of Its Arguments
Consider the swap() method in the following Swapper class, which switches the
values of its arguments:
public class Swapper
{
public static void swap (int[] x, int[] y)
{
int hold = x[0];
x[0] = y[0];
y[0] = hold;
}
}
The call specification publishes the swap() method as a call specification, swap().
The call specification declares IN OUT formal parameters, because values must be
passed in and out. All call specification OUT and IN OUT parameters must map to Java
array parameters.
CREATE PROCEDURE swap (x IN OUT NUMBER, y IN OUT NUMBER)
AS LANGUAGE JAVA
NAME 'Swapper.swap(int[], int[])';
Note:
A Java method and its call specification can have the same
name.
Publishing Java Classes With Call Specifications
6-9
Writing Packaged Call Specifications
Writing Packaged Call Specifications
A PL/SQL package is a schema object that groups logically related types, items, and
subprograms. Usually, packages have two parts, a specification and a body. The
specification is the interface to your applications and declares the types, constants,
variables, exceptions, cursors, and subprograms available for use. The body defines
the cursors and subprograms.
In SQL*Plus, you can define PL/SQL packages interactively, using the following
syntax:
CREATE [OR REPLACE] PACKAGE package_name
[AUTHID {CURRENT_USER | DEFINER}] {IS | AS}
[type_definition [type_definition] ...]
[cursor_spec [cursor_spec] ...]
[item_declaration [item_declaration] ...]
[{subprogram_spec | call_spec} [{subprogram_spec | call_spec}]...]
END [package_name];
[CREATE [OR REPLACE] PACKAGE BODY package_name {IS | AS}
[type_definition [type_definition] ...]
[cursor_body [cursor_body] ...]
[item_declaration [item_declaration] ...]
[{subprogram_spec | call_spec} [{subprogram_spec | call_spec}]...]
[BEGIN
sequence_of_statements]
END [package_name];]
The specification holds public declarations, which are visible to your application. The
body contains implementation details and private declarations, which are hidden from
your application. Following the declarative part of the package is the body, which is
the optional initialization part. It holds statements that initialize package variables. It
is run only once, the first time you reference the package.
A call specification declared in a package specification cannot have the same signature,
that is, the name and parameter list, as a subprogram in the package body. If you
declare all the subprograms in a package specification as call specifications, then the
package body is not required, unless you want to define a cursor or use the
initialization part.
The AUTHID clause determines whether all the packaged subprograms run with the
privileges of their definer, which is the default, or invoker. It also determines whether
unqualified references to schema objects are resolved in the schema of the definer or
invoker.
Example 6–5 provides an example of packaged call specification.
Example 6–5 Packaged Call Specification
Consider a Java class, DeptManager, which consists of methods for adding a new
department, dropping a department, and changing the location of a department. Note
that the addDept() method uses a database sequence to get the next department
number. The three methods are logically related, and therefore, you may want to
group their call specifications in a PL/SQL package.
import java.sql.*;
import java.io.*;
import oracle.jdbc.*;
public class DeptManager
{
6-10 Oracle Database Java Developer’s Guide
Writing Packaged Call Specifications
public static void addDept (String deptName, String deptLoc) throws SQLException
{
Connection conn = DriverManager.getConnection("jdbc:default:connection:");
String sql = "SELECT deptnos.NEXTVAL FROM dual";
String sql2 = "INSERT INTO dept VALUES (?, ?, ?)";
int deptID = 0;
try
{
PreparedStatement pstmt = conn.prepareStatement(sql);
ResultSet rset = pstmt.executeQuery();
while (rset.next())
{
deptID = rset.getInt(1);
}
pstmt = conn.prepareStatement(sql2);
pstmt.setInt(1, deptID);
pstmt.setString(2, deptName);
pstmt.setString(3, deptLoc);
pstmt.executeUpdate();
rset.close();
pstmt.close();
}
catch (SQLException e)
{
System.err.println(e.getMessage());
}
}
public static void dropDept (int deptID) throws SQLException
{
Connection conn = DriverManager.getConnection("jdbc:default:connection:");
String sql = "DELETE FROM dept WHERE deptno = ?";
try
{
PreparedStatement pstmt = conn.prepareStatement(sql);
pstmt.setInt(1, deptID);
pstmt.executeUpdate();
pstmt.close();
}
catch (SQLException e)
{
System.err.println(e.getMessage());
}
}
public static void changeLoc (int deptID, String newLoc) throws SQLException
{
Connection conn = DriverManager.getConnection("jdbc:default:connection:");
String sql = "UPDATE dept SET loc = ? WHERE deptno = ?";
try
{
PreparedStatement pstmt = conn.prepareStatement(sql);
pstmt.setString(1, newLoc);
pstmt.setInt(2, deptID);
pstmt.executeUpdate();
pstmt.close();
}
catch (SQLException e)
{
System.err.println(e.getMessage());
Publishing Java Classes With Call Specifications
6-11
Writing Object Type Call Specifications
}
}
}
Suppose you want to package the methods addDept(), dropDept(), and
changeLoc(). First, you must create the package specification, as follows:
CREATE OR REPLACE PACKAGE dept_mgmt AS
PROCEDURE add_dept (dept_name VARCHAR2, dept_loc VARCHAR2);
PROCEDURE drop_dept (dept_id NUMBER);
PROCEDURE change_loc (dept_id NUMBER, new_loc VARCHAR2);
END dept_mgmt;
Then, you must create the package body by writing the call specifications for the Java
methods, as follows:
CREATE OR REPLACE PACKAGE BODY dept_mgmt AS
PROCEDURE add_dept (dept_name VARCHAR2, dept_loc VARCHAR2)
AS LANGUAGE JAVA
NAME 'DeptManager.addDept(java.lang.String, java.lang.String)';
PROCEDURE drop_dept (dept_id NUMBER)
AS LANGUAGE JAVA
NAME 'DeptManager.dropDept(int)';
PROCEDURE change_loc (dept_id NUMBER, new_loc VARCHAR2)
AS LANGUAGE JAVA
NAME 'DeptManager.changeLoc(int, java.lang.String)';
END dept_mgmt;
To reference the stored procedures in the dept_mgmt package, use the dot notation, as
follows:
CALL dept_mgmt.add_dept('PUBLICITY', 'DALLAS');
Writing Object Type Call Specifications
In SQL, object-oriented programming is based on object types, which are user-defined
composite data types that encapsulate a data structure along with the functions and
procedures required to manipulate the data. The variables that form the data structure
are known as attributes. The functions and procedures that characterize the behavior
of the object type are known as methods, which can be written in Java.
As with a package, an object type has two parts: a specification and a body. The
specification is the interface to your applications and declares a data structure, which
is a set of attributes, along with the operations or methods required to manipulate the
data. The body implements the specification by defining PL/SQL subprogram bodies
or call specifications.
If the specification declares only attributes or call specifications, then the body is not
required. If you implement all your methods in Java, then you can place their call
specifications in the specification part of the object type and omit the body part.
In SQL*Plus, you can define SQL object types interactively, using the following syntax:
CREATE [OR REPLACE] TYPE type_name
[AUTHID {CURRENT_USER | DEFINER}] {IS | AS} OBJECT (
attribute_name data_type[, attribute_name data_type]...
[{MAP | ORDER} MEMBER {function_spec | call_spec},]
[{MEMBER | STATIC} {subprogram_spec | call_spec}
6-12 Oracle Database Java Developer’s Guide
Writing Object Type Call Specifications
[, {MEMBER | STATIC} {subprogram_spec | call_spec}]...]
);
[CREATE [OR REPLACE] TYPE BODY type_name {IS | AS}
{ {MAP | ORDER} MEMBER function_body;
| {MEMBER | STATIC} {subprogram_body | call_spec};}
[{MEMBER | STATIC} {subprogram_body | call_spec};]...
END;]
The AUTHID clause determines whether all member methods run with the current user
privileges, which determines the invoker's or definer's rights.
This section covers the following topics:
■
Declaring Attributes
■
Declaring Methods
Declaring Attributes
In an object type specification, all attributes must be declared before any methods are.
In addition, you must declare at least one attribute. The maximum number of
attributes that can be declared is 1000. Methods are optional.
As with a Java variable, you declare an attribute with a name and data type. The name
must be unique within the object type, but can be reused in other object types. The
data type can be any SQL type, except LONG, LONG RAW, NCHAR, NVARCHAR2, NCLOB,
ROWID, and UROWID.
You cannot initialize an attribute in its declaration using the assignment operator or
DEFAULT clause. Furthermore, you cannot impose the NOT NULL constraint on an
attribute. However, objects can be stored in database tables on which you can impose
constraints.
Declaring Methods
After declaring attributes, you can declare methods. MEMBER methods accept a built-in
parameter known as SELF, which is an instance of the object type. Whether declared
implicitly or explicitly, it is always the first parameter passed to a MEMBER method. In
the method body, SELF denotes the object whose method was called. MEMBER methods
are called on instances, as follows:
instance_expression.method()
STATIC methods, which cannot accept or reference SELF, are invoked on the object
type and not its instances, as follows:
object_type_name.method()
If you want to call a Java method that is not static, then you must specify the
keyword MEMBER in its call specification. Similarly, if you want to call a static Java
method, then you must specify the keyword STATIC in its call specification.
This section contains the following topics:
■
Map and Order Methods
■
Constructor Methods
■
Examples
Publishing Java Classes With Call Specifications
6-13
Writing Object Type Call Specifications
Map and Order Methods
The values of a SQL scalar data type, such as CHAR, have a predefined order and,
therefore, can be compared with other values. However, instances of an object type
have no predefined order. To put them in order, SQL calls a user-defined map method.
SQL uses the ordering to evaluate boolean expressions, such as x > y, and to make
comparisons implied by the DISTINCT, GROUP BY, and ORDER BY clauses. A map
method returns the relative position of an object in the ordering of all such objects. An
object type can contain only one map method, which must be a function without any
parameters and with one of the following return types: DATE, NUMBER, or VARCHAR2.
Alternatively, you can supply SQL with an order method, which compares two
objects. An order method takes only two parameters: the built-in parameter, SELF,
and another object of the same type. If o1 and o2 are objects, then a comparison, such
as o1 > o2, calls the order method automatically. The method returns a negative
number, zero, or a positive number signifying that SELF is less than, equal to, or
greater than the other parameter, respectively. An object type can contain only one
order method, which must be a function that returns a numeric result.
You can declare a map method or an order method, but not both. If you declare either
method, then you can compare objects in SQL and PL/SQL. However, if you declare
neither method, then you can compare objects only in SQL and solely for equality or
inequality.
Note: Two objects of the same type are equal if the values of their
corresponding attributes are equal.
Constructor Methods
Every object type has a constructor, which is a system-defined function with the same
name as the object type. The constructor initializes and returns an instance of that
object type.
Oracle Database generates a default constructor for every object type. The formal
parameters of the constructor match the attributes of the object type. That is, the
parameters and attributes are declared in the same order and have the same names
and data types. SQL never calls a constructor implicitly. As a result, you must call it
explicitly. Constructor calls are allowed wherever function calls are allowed.
To invoke a Java constructor from SQL, you must wrap calls to
it in a static method and declare the corresponding call
specification as a STATIC member of the object type.
Note:
Examples
In this section, each example builds on the previous one. To begin, you create two SQL
object types to represent departments and employees. First, you write the specification
for the object type Department. The body is not required, because the specification
declares only attributes. The specification is as follows:
CREATE TYPE Department AS OBJECT (
deptno NUMBER(2),
dname VARCHAR2(14),
loc VARCHAR2(13)
);
6-14 Oracle Database Java Developer’s Guide
Writing Object Type Call Specifications
Then, you create the object type Employee. The deptno attribute stores a handle,
called a REF, to objects of the type Department. A REF indicates the location of an
object in an object table, which is a database table that stores instances of an object
type. The REF does not point to a specific instance copy in memory. To declare a REF,
you specify the data type REF and the object type that the REF targets. The Employee
type is created as follows:
CREATE TYPE Employee AS OBJECT (
empno NUMBER(4),
ename VARCHAR2(10),
job VARCHAR2(9),
mgr NUMBER(4),
hiredate DATE,
sal NUMBER(7,2),
comm NUMBER(7,2),
deptno REF Department
);
Next, you create the SQL object tables to hold objects of type Department and
Employee. Create the depts object table, which will hold objects of the Department
type. Populate the object table by selecting data from the dept relational table and
passing it to a constructor, which is a system-defined function with the same name as
the object type. Use the constructor to initialize and return an instance of that object
type. The depts table is created as follows:
CREATE TABLE depts OF Department AS
SELECT Department(deptno, dname, loc) FROM dept;
Create the emps object table, which will hold objects of type Employee. The last
column in the emps object table, which corresponds to the last attribute of the
Employee object type, holds references to objects of type Department. To fetch the
references into this column, use the operator REF, which takes a table alias associated
with a row in an object table as its argument. The emps table is created as follows:
CREATE TABLE emps OF Employee AS
SELECT Employee(e.empno, e.ename, e.job, e.mgr, e.hiredate, e.sal, e.comm,
(SELECT REF(d) FROM depts d WHERE d.deptno = e.deptno))
FROM emp e;
Selecting a REF returns a handle to an object. It does not materialize the object itself. To
do that, you can use methods in the oracle.sql.REF class, which supports Oracle
object references. This class, which is a subclass of oracle.sql.Datum, extends the
standard JDBC interface, oracle.jdbc2.Ref.
Using Class oracle.sql.STRUCT
To continue, you write a Java stored procedure. The Paymaster class has one method,
which computes an employee's wages. The getAttributes() method defined in the
oracle.sql.STRUCT class uses the default JDBC mappings for the attribute types.
For example, NUMBER maps to BigDecimal. The Paymaster class is created as
follows:
import
import
import
import
import
import
import
java.sql.*;
java.io.*;
oracle.sql.*;
oracle.jdbc.*;
oracle.oracore.*;
oracle.jdbc2.*;
java.math.*;
Publishing Java Classes With Call Specifications
6-15
Writing Object Type Call Specifications
public class Paymaster
{
public static BigDecimal wages(STRUCT e) throws java.sql.SQLException
{
// Get the attributes of the Employee object.
Object[] attribs = e.getAttributes();
// Must use numeric indexes into the array of attributes.
BigDecimal sal = (BigDecimal)(attribs[5]); // [5] = sal
BigDecimal comm = (BigDecimal)(attribs[6]); // [6] = comm
BigDecimal pay = sal;
if (comm != null)
pay = pay.add(comm);
return pay;
}
}
Because the wages() method returns a value, you write a function call specification
for it, as follows:
CREATE OR REPLACE FUNCTION wages (e Employee) RETURN NUMBER AS
LANGUAGE JAVA
NAME 'Paymaster.wages(oracle.sql.STRUCT) return BigDecimal';
This is a top-level call specification, because it is not defined inside a package or object
type.
Implementing the SQLData Interface
To make access to object attributes more natural, create a Java class that implements
the SQLData interface. To do so, you must provide the readSQL() and writeSQL()
methods as defined by the SQLData interface. The JDBC driver calls the readSQL()
method to read a stream of database values and populate an instance of your Java
class. In the following example, you revise Paymaster by adding a second method,
raiseSal():
import
import
import
import
import
import
import
java.sql.*;
java.io.*;
oracle.sql.*;
oracle.jdbc.*;
oracle.oracore.*;
oracle.jdbc2.*;
java.math.*;
public class Paymaster implements SQLData
{
// Implement the attributes and operations for this type.
private BigDecimal empno;
private String ename;
private String job;
private BigDecimal mgr;
private Date hiredate;
private BigDecimal sal;
private BigDecimal comm;
private Ref dept;
public static BigDecimal wages(Paymaster e)
{
BigDecimal pay = e.sal;
if (e.comm != null)
pay = pay.add(e.comm);
return pay;
6-16 Oracle Database Java Developer’s Guide
Writing Object Type Call Specifications
}
public static void raiseSal(Paymaster[] e, BigDecimal amount)
{
e[0].sal = // IN OUT passes [0]
e[0].sal.add(amount); // increase salary by given amount
}
// Implement SQLData interface.
private String sql_type;
public String getSQLTypeName() throws SQLException
{
return sql_type;
}
public void readSQL(SQLInput stream, String typeName) throws SQLException
{
sql_type = typeName;
empno = stream.readBigDecimal();
ename = stream.readString();
job = stream.readString();
mgr = stream.readBigDecimal();
hiredate = stream.readDate();
sal = stream.readBigDecimal();
comm = stream.readBigDecimal();
dept = stream.readRef();
}
public void writeSQL(SQLOutput stream) throws SQLException
{
stream.writeBigDecimal(empno);
stream.writeString(ename);
stream.writeString(job);
stream.writeBigDecimal(mgr);
stream.writeDate(hiredate);
stream.writeBigDecimal(sal);
stream.writeBigDecimal(comm);
stream.writeRef(dept);
}
}
You must revise the call specification for wages(), as follows, because its parameter
has changed from oralce.sql.STRUCT to Paymaster:
CREATE OR REPLACE FUNCTION wages (e Employee) RETURN NUMBER AS
LANGUAGE JAVA
NAME 'Paymaster.wages(Paymaster) return BigDecimal';
Because the new method, raiseSal(), is void, write a procedure call specification
for it, as follows:
CREATE OR REPLACE PROCEDURE raise_sal (e IN OUT Employee, r NUMBER)
AS LANGUAGE JAVA
NAME 'Paymaster.raiseSal(Paymaster[], java.math.BigDecimal)';
Again, this is a top-level call specification.
Publishing Java Classes With Call Specifications
6-17
Writing Object Type Call Specifications
Implementing Object Type Methods
Assume you decide to drop the top-level call specifications wages and raise_sal
and redeclare them as methods of the object type Employee. In an object type
specification, all methods must be declared after the attributes. The body of the object
type is not required, because the specification declares only attributes and call
specifications. The Employee object type can be re-created as follows:
CREATE TYPE Employee AS OBJECT (
empno NUMBER(4),
ename VARCHAR2(10),
job VARCHAR2(9),
mgr NUMBER(4),
hiredate DATE,
sal NUMBER(7,2),
comm NUMBER(7,2),
deptno REF Department
MEMBER FUNCTION wages RETURN NUMBER
AS LANGUAGE JAVA
NAME 'Paymaster.wages() return java.math.BigDecimal',
MEMBER PROCEDURE raise_sal (r NUMBER)
AS LANGUAGE JAVA
NAME 'Paymaster.raiseSal(java.math.BigDecimal)'
);
Then, you revise Paymaster accordingly. You need not pass an array to raiseSal(),
because the SQL parameter SELF corresponds directly to the Java parameter this,
even when SELF is declared as IN OUT, which is the default for procedures.
import
import
import
import
import
import
import
java.sql.*;
java.io.*;
oracle.sql.*;
oracle.jdbc.*;
oracle.oracore.*;
oracle.jdbc2.*;
java.math.*;
public class Paymaster implements SQLData
{
// Implement the attributes and operations for this type.
private BigDecimal empno;
private String ename;
private String job;
private BigDecimal mgr;
private Date hiredate;
private BigDecimal sal;
private BigDecimal comm;
private Ref dept;
public BigDecimal wages()
{
BigDecimal pay = sal;
if (comm != null)
pay = pay.add(comm);
return pay;
}
public void raiseSal(BigDecimal amount)
{
// For SELF/this, even when IN OUT, no array is needed.
6-18 Oracle Database Java Developer’s Guide
Writing Object Type Call Specifications
sal = sal.add(amount);
}
// Implement SQLData interface.
String sql_type;
public String getSQLTypeName() throws SQLException
{
return sql_type;
}
public void readSQL(SQLInput stream, String typeName) throws SQLException
{
sql_type = typeName;
empno = stream.readBigDecimal();
ename = stream.readString();
job = stream.readString();
mgr = stream.readBigDecimal();
hiredate = stream.readDate();
sal = stream.readBigDecimal();
comm = stream.readBigDecimal();
dept = stream.readRef();
}
public void writeSQL(SQLOutput stream) throws SQLException
{
stream.writeBigDecimal(empno);
stream.writeString(ename);
stream.writeString(job);
stream.writeBigDecimal(mgr);
stream.writeDate(hiredate);
stream.writeBigDecimal(sal);
stream.writeBigDecimal(comm);
stream.writeRef(dept);
}
}
Publishing Java Classes With Call Specifications
6-19
Writing Object Type Call Specifications
6-20 Oracle Database Java Developer’s Guide
7
Calling Stored Procedures
After you load and publish a Java stored procedure, you can call it. This chapter
describes the procedure for calling Java stored procedures in various contexts. It also
describes how Oracle JVM handles SQL exceptions.
This chapter contains the following sections:
■
Calling Java from the Top Level
■
Calling Java from Database Triggers
■
Calling Java from SQL DML
■
Calling Java from PL/SQL
■
Calling PL/SQL from Java
■
How Oracle JVM Handles Exceptions
Calling Java from the Top Level
The SQL CALL statement lets you call Java methods, which are published at the top
level, in PL/SQL packages, or in SQL object types. In SQL*Plus, you can run the CALL
statement interactively using the following syntax:
CALL [schema_name.][{package_name | object_type_name}][@dblink_name]
{ procedure_name ([param[, param]...])
| function_name ([param[, param]...]) INTO :host_variable};
where param is represented by the following syntax:
{literal | :host_variable}
Host variables are variables that are declared in a host environment. They must be
prefixed with a colon. The following examples show that a host variable cannot appear
twice in the same CALL statement and that a subprogram without parameters must be
called with an empty parameter list:
CALL swap(:x, :x); -- illegal, duplicate host variables
CALL balance() INTO :current_balance; -- () required
This section covers the following topics:
■
Redirecting Output
■
Examples of Calling Java Stored Procedures From the Top Level
Calling Stored Procedures
7-1
Calling Java from the Top Level
Redirecting Output
On the server, the default output device is a trace file and not the user screen. As a
result, System.out and System.err print output to the current trace files. To
redirect output to the SQL*Plus text buffer, you must call the set_output()
procedure in the DBMS_JAVA package, as follows:
SQL> SET SERVEROUTPUT ON
SQL> CALL dbms_java.set_output(2000);
The minimum buffer size is 2,000 bytes, which is also the default size, and the
maximum buffer size is 1,000,000 bytes. In the following example, the buffer size is
increased to 5,000 bytes:
SQL> SET SERVEROUTPUT ON SIZE 5000
SQL> CALL dbms_java.set_output(5000);
The output is displayed when the stored procedure exits.
Examples of Calling Java Stored Procedures From the Top Level
This section provides the following examples
■
Example 7–1, "A Simple JDBC Stored Procedure"
■
Example 7–2, "Fibonacci Sequence"
Example 7–1 A Simple JDBC Stored Procedure
In the following example, the main() method accepts the name of a database table,
such as emp, and an optional WHERE clause specifying a condition, such as sal >
1500. If you omit the condition, then the method deletes all rows from the table, else it
deletes only those rows that meet the condition.
import java.sql.*;
import oracle.jdbc.*;
public class Deleter
{
public static void main (String[] args) throws SQLException
{
Connection conn = DriverManager.getConnection("jdbc:default:connection:");
String sql = "DELETE FROM " + args[0];
if (args.length > 1)
sql += " WHERE " + args[1];
try
{
Statement stmt = conn.createStatement();
stmt.executeUpdate(sql);
stmt.close();
}
catch (SQLException e)
{
System.err.println(e.getMessage());
}
}
}
The main() method can take either one or two arguments. Normally, the DEFAULT
clause is used to vary the number of arguments passed to a PL/SQL subprogram.
7-2 Oracle Database Java Developer’s Guide
Calling Java from the Top Level
However, this clause is not allowed in a call specification. As a result, you must
overload two packaged procedures, as follows:
CREATE OR REPLACE PACKAGE pkg AS
PROCEDURE delete_rows (table_name VARCHAR2);
PROCEDURE delete_rows (table_name VARCHAR2, condition VARCHAR2);
END;
CREATE OR REPLACE PACKAGE BODY pkg AS
PROCEDURE delete_rows (table_name VARCHAR2)
AS LANGUAGE JAVA
NAME 'Deleter.main(java.lang.String[])';
PROCEDURE delete_rows (table_name VARCHAR2, condition VARCHAR2)
AS LANGUAGE JAVA
NAME 'Deleter.main(java.lang.String[])';
END;
Now, you can call the delete_rows procedure, as follows:
SQL> CALL pkg.delete_rows('emp', 'sal > 1500');
Call completed.
SQL> SELECT ename, sal FROM emp;
ENAME
SAL
--------- -------SMITH
800
WARD
1250
MARTIN
1250
TURNER
1500
ADAMS
1100
JAMES
950
MILLER
1300
7 rows selected.
Note:
You cannot overload top-level procedures.
Example 7–2 Fibonacci Sequence
Assume that the executable for the following Java class is stored in Oracle Database:
public class Fibonacci
{
public static int fib (int n)
{
if (n == 1 || n == 2)
return 1;
else
return fib(n - 1) + fib(n - 2);
}
}
The Fibonacci class has a method, fib(), which returns the nth Fibonacci number.
The Fibonacci sequence, 1, 1, 2, 3, 5, 8, 13, 21, . . ., is recursive. Each term in the
sequence, after the second term, is the sum of the two terms that immediately precede
it. Because fib() returns a value, you must publish it as a function, as follows:
Calling Stored Procedures
7-3
Calling Java from Database Triggers
CREATE OR REPLACE FUNCTION fib (n NUMBER) RETURN NUMBER
AS LANGUAGE JAVA
NAME 'Fibonacci.fib(int) return int';
Next, you declare two SQL*Plus host variables and initialize the first one:
SQL> VARIABLE n NUMBER
SQL> VARIABLE f NUMBER
SQL> EXECUTE :n := 7;
PL/SQL procedure successfully completed.
Now, you can call the fib() function. In a CALL statement, host variables must be
prefixed with a colon. The function can be called, as follows:
SQL> CALL fib(:n) INTO :f;
Call completed.
SQL> PRINT f
F
---------13
Calling Java from Database Triggers
A database trigger is a stored program that is associated with a specific table or view.
Oracle Database runs the trigger automatically whenever a data manipulation
language (DML) operation affects the table or view.
When a triggering event occurs, the trigger runs and either a PL/SQL block or a CALL
statement performs the action. A statement trigger runs once, before or after the
triggering event. A row trigger runs once for each row affected by the triggering event.
In a database trigger, you can reference the new and old values of changing rows by
using the correlation names new and old. In the trigger-action block or CALL
statement, column names must be prefixed with :new or :old.
The following are examples of calling Java stored procedures from a database trigger:
■
Example 7–3, "Calling Java Stored Procedure from Database Trigger - I"
■
Example 7–4, "Calling Java Stored Procedure from Database Trigger - II"
Example 7–3 Calling Java Stored Procedure from Database Trigger - I
Assume you want to create a database trigger that uses the following Java class to log
out-of-range salary increases:
import java.sql.*;
import java.io.*;
import oracle.jdbc.*;
public class DBTrigger
{
public static void logSal (int empID, float oldSal, float newSal)
throws SQLException
{
Connection conn = DriverManager.getConnection("jdbc:default:connection:");
String sql = "INSERT INTO sal_audit VALUES (?, ?, ?)";
7-4 Oracle Database Java Developer’s Guide
Calling Java from Database Triggers
try
{
PreparedStatement pstmt = conn.prepareStatement(sql);
pstmt.setInt(1, empID);
pstmt.setFloat(2, oldSal);
pstmt.setFloat(3, newSal);
pstmt.executeUpdate();
pstmt.close();
}
catch (SQLException e)
{
System.err.println(e.getMessage());
}
}
}
The DBTrigger class has one method, logSal(), which inserts a row into the
sal_audit table. Because logSal() is a void method, you must publish it as a
procedure:
CREATE OR REPLACE PROCEDURE log_sal (
emp_id NUMBER,
old_sal NUMBER,
new_sal NUMBER
)
AS LANGUAGE JAVA
NAME 'DBTrigger.logSal(int, float, float)';
Next, create the sal_audit table, as follows:
CREATE TABLE sal_audit (
empno NUMBER,
oldsal NUMBER,
newsal NUMBER
);
Finally, create the database trigger, which fires when a salary increase exceeds 20
percent:
CREATE OR REPLACE TRIGGER sal_trig
AFTER UPDATE OF sal ON emp
FOR EACH ROW
WHEN (new.sal > 1.2 * old.sal)
CALL log_sal(:new.empno, :old.sal, :new.sal);
When you run the following UPDATE statement, it updates all rows in the emp table:
SQL> UPDATE emp SET sal = sal + 300;
For each row that meets the condition set in the WHEN clause of the trigger, the trigger
runs and the Java method inserts a row into the sal_audit table.
SQL> SELECT * FROM sal_audit;
EMPNO
OLDSAL
NEWSAL
---------- ---------- ---------7369
800
1100
7521
1250
1550
7654
1250
1550
7876
1100
1400
7900
950
1250
7934
1300
1600
Calling Stored Procedures
7-5
Calling Java from Database Triggers
6 rows selected.
Example 7–4 Calling Java Stored Procedure from Database Trigger - II
Assume you want to create a trigger that inserts rows into a database view, which is
defined as follows:
CREATE VIEW emps AS
SELECT empno, ename, 'Sales' AS dname FROM sales
UNION ALL
SELECT empno, ename, 'Marketing' AS dname FROM mktg;
The sales and mktg database tables are defined as:
CREATE TABLE sales (empno NUMBER(4), ename VARCHAR2(10));
CREATE TABLE mktg (empno NUMBER(4), ename VARCHAR2(10));
You must write an INSTEAD OF trigger, because rows cannot be inserted into a view
that uses set operators, such as UNION ALL. Instead, the trigger will insert rows into
the base tables.
First, add the following Java method to the DBTrigger class, which is defined in
Example 7–3:
public static void addEmp (int empNo, String empName, String deptName)
throws SQLException
{
Connection conn = DriverManager.getConnection("jdbc:default:connection:");
String tabName = (deptName.equals("Sales") ? "sales" : "mktg");
String sql = "INSERT INTO " + tabName + " VALUES (?, ?)";
try
{
PreparedStatement pstmt = conn.prepareStatement(sql);
pstmt.setInt(1, empNo);
pstmt.setString(2, empName);
pstmt.executeUpdate();
pstmt.close();
}
catch (SQLException e)
{
System.err.println(e.getMessage());
}
}
The addEmp() method inserts a row into the sales or mktg table depending on the
value of the deptName parameter. Write the call specification for this method, as
follows:
CREATE OR REPLACE PROCEDURE add_emp (
emp_no NUMBER,
emp_name VARCHAR2,
dept_name VARCHAR2
)
AS LANGUAGE JAVA
NAME 'DBTrigger.addEmp(int, java.lang.String, java.lang.String)';
Next, create the INSTEAD OF trigger, as follows:
CREATE OR REPLACE TRIGGER emps_trig
INSTEAD OF INSERT ON emps
7-6 Oracle Database Java Developer’s Guide
Calling Java from SQL DML
FOR EACH ROW
CALL add_emp(:new.empno, :new.ename, :new.dname);
When you run each of the following INSERT statements, the trigger runs and the Java
method inserts a row into the appropriate base table:
SQL>
SQL>
SQL>
SQL>
SQL>
SQL>
INSERT
INSERT
INSERT
INSERT
INSERT
INSERT
INTO
INTO
INTO
INTO
INTO
INTO
emps
emps
emps
emps
emps
emps
VALUES
VALUES
VALUES
VALUES
VALUES
VALUES
(8001,
(8002,
(8003,
(8004,
(8005,
(8006,
'Chand', 'Sales');
'Van Horn', 'Sales');
'Waters', 'Sales');
'Bellock', 'Marketing');
'Perez', 'Marketing');
'Foucault', 'Marketing');
SQL> SELECT * FROM sales;
EMPNO
---------8001
8002
8003
ENAME
---------Chand
Van Horn
Waters
SQL> SELECT * FROM mktg;
EMPNO
---------8004
8005
8006
ENAME
---------Bellock
Perez
Foucault
SQL> SELECT * FROM emps;
EMPNO
---------8001
8002
8003
8004
8005
8006
ENAME
---------Chand
Van Horn
Waters
Bellock
Perez
Foucault
DNAME
--------Sales
Sales
Sales
Marketing
Marketing
Marketing
Calling Java from SQL DML
If you publish Java methods as functions, then you can call them from SQL SELECT,
INSERT, UPDATE, DELETE, CALL, EXPLAIN PLAN, LOCK TABLE, and MERGE
statements. For example, assume that the executable for the following Java class is
stored in Oracle Database:
public class Formatter
{
public static String formatEmp (String empName, String jobTitle)
{
empName = empName.substring(0,1).toUpperCase() +
empName.substring(1).toLowerCase();
jobTitle = jobTitle.toLowerCase();
if (jobTitle.equals("analyst"))
return (new String(empName + " is an exempt analyst"));
else
return (new String(empName + " is a non-exempt " + jobTitle));
}
Calling Stored Procedures
7-7
Calling Java from PL/SQL
}
The Formatter class has the formatEmp() method, which returns a formatted
string containing a staffer's name and job status. Write the call specification for this
method, as follows:
CREATE OR REPLACE FUNCTION format_emp (ename VARCHAR2, job VARCHAR2)
RETURN VARCHAR2
AS LANGUAGE JAVA
NAME 'Formatter.formatEmp (java.lang.String, java.lang.String)
return java.lang.String';
Now, call the format_emp function to format a list of employees:
SQL> SELECT format_emp(ename, job) AS "Employees" FROM emp
2
WHERE job NOT IN ('MANAGER', 'PRESIDENT') ORDER BY ename;
Employees
-------------------------------------------Adams is a non-exempt clerk
Allen is a non-exempt salesman
Ford is an exempt analyst
James is a non-exempt clerk
Martin is a non-exempt salesman
Miller is a non-exempt clerk
Scott is an exempt analyst
Smith is a non-exempt clerk
Turner is a non-exempt salesman
Ward is a non-exempt salesman
Restrictions
A Java method must adhere to the following rules, which are meant to control side
effects:
■
■
■
When you call a method from a SELECT statement or parallel INSERT, UPDATE, or
DELETE statements, the method cannot modify any database tables.
When you call a method from an INSERT, UPDATE, or DELETE statement, the
method cannot query or modify any database tables modified by that statement.
When you call a method from a SELECT, INSERT, UPDATE, or DELETE statement,
the method cannot run SQL transaction control statements, such as COMMIT,
session control statements, such as SET ROLE, or system control statements, such
as ALTER SYSTEM. In addition, the method cannot run data definition language
(DDL) statements, such as CREATE, because they are followed by an automatic
commit.
If any SQL statement inside the method violates any of the preceding rules, then you
get an error at run time.
Calling Java from PL/SQL
You can call Java stored procedures from any PL/SQL block, subprogram, or package.
For example, assume that the executable for the following Java class is stored in Oracle
Database:
import java.sql.*;
import oracle.jdbc.*;
7-8 Oracle Database Java Developer’s Guide
Calling Java from PL/SQL
public class Adjuster
{
public static void raiseSalary (int empNo, float percent) throws SQLException
{
Connection conn = DriverManager.getConnection("jdbc:default:connection:");
String sql = "UPDATE emp SET sal = sal * ? WHERE empno = ?";
try
{
PreparedStatement pstmt = conn.prepareStatement(sql);
pstmt.setFloat(1, (1 + percent / 100));
pstmt.setInt(2, empNo);
pstmt.executeUpdate();
pstmt.close();
}
catch (SQLException e)
{
System.err.println(e.getMessage());
}
}
}
The Adjuster class has one method, which raises the salary of an employee by a
given percentage. Because raiseSalary() is a void method, you must publish it as
a procedure, as follows:
CREATE OR REPLACE PROCEDURE raise_salary (empno NUMBER, pct NUMBER)
AS LANGUAGE JAVA
NAME 'Adjuster.raiseSalary(int, float)';
In the following example, you call the raise_salary procedure from an anonymous
PL/SQL block:
DECLARE
emp_id NUMBER;
percent NUMBER;
BEGIN
-- get values for emp_id and percent
raise_salary(emp_id, percent);
...
END;
In the following example, you call the row_count function, which defined in
Example 6–3 on page 6-9, from a standalone PL/SQL stored procedure:
CREATE PROCEDURE calc_bonus (emp_id NUMBER, bonus OUT NUMBER) AS
emp_count NUMBER;
...
BEGIN
emp_count := row_count('emp');
...
END;
In the following example, you call the raise_sal method of the Employee object
type, which is defined in "Implementing Object Type Methods" on page 6-18, from an
anonymous PL/SQL block:
DECLARE
emp_id NUMBER(4);
v emp_type;
BEGIN
-- assign a value to emp_id
Calling Stored Procedures
7-9
Calling PL/SQL from Java
SELECT VALUE(e) INTO v FROM emps e WHERE empno = emp_id;
v.raise_sal(500);
UPDATE emps e SET e = v WHERE empno = emp_id;
...
END;
Calling PL/SQL from Java
Java Database Connectivity (JDBC) and SQLJ enable you to call PL/SQL stored
functions and procedures. For example, you want to call the following stored function,
which returns the balance of a specified bank account:
FUNCTION balance (acct_id NUMBER) RETURN NUMBER IS
acct_bal NUMBER;
BEGIN
SELECT bal INTO acct_bal FROM accts
WHERE acct_no = acct_id;
RETURN acct_bal;
END;
In a JDBC program, a call to the balance function can be written as follows:
...
CallableStatement cstmt = conn.prepareCall("{? = CALL balance(?)}");
cstmt.registerOutParameter(1, Types.FLOAT);
cstmt.setInt(2, acctNo);
cstmt.executeUpdate();
float acctBal = cstmt.getFloat(1);
...
In a SQLJ program, the call can be written as follows:
...
#sql acctBal = {VALUES(balance(:IN acctNo))};
...
How Oracle JVM Handles Exceptions
Java exceptions are objects and have a naming and inheritance hierarchy. As a result,
you can substitute a subexception, that is, a subclass of an exception class, for its
superexception, that is, the superclass of an exception class.
All Java exception objects support the toString() method, which returns the fully
qualified name of the exception class concatenated to an optional string. Typically, the
string contains data-dependent information about the exceptional condition. Usually,
the code that constructs the exception associates the string with it.
When a Java stored procedure runs a SQL statement, any exception thrown is
materialized to the procedure as a subclass of java.sql.SQLException. This class
has the getErrorCode() and getMessage() methods, which return the Oracle
error code and message, respectively.
If a stored procedure called from SQL or PL/SQL throws an exception and is not
caught by Java, then the following error message appears:
ORA-29532 Java call terminated by uncaught Java exception
This is how all uncaught exceptions, including non-SQL exceptions, are reported.
7-10 Oracle Database Java Developer’s Guide
8
Java Stored Procedures Application
Example
This chapter describes how to build a Java application with stored procedures. By
following the steps mentioned in this chapter from the design phase to the actual
implementation, you can write your own applications.
This chapter contains the followings sections:
■
Drawing the Entity-Relationship Diagram
■
Planning the Database Schema
■
Creating the Database Tables
■
Writing the Java Classes
■
Loading the Java Classes
■
Publishing the Java Classes
■
Calling the Java Stored Procedures
Drawing the Entity-Relationship Diagram
The objective is to develop a simple system for managing customer purchase orders.
First, you must identify the business entities involved and their relationships. To do
this, you must draw an entity-relationship (E-R) diagram by following the rules and
examples given in Figure 8–1.
Java Stored Procedures Application Example 8-1
Drawing the Entity-Relationship Diagram
Figure 8–1 Rule for Drawing an E-R Diagram
As Figure 8–2 illustrates, the basic entities in this example are customers, purchase
orders, line items, and stock items.
8-2 Oracle Database Java Developer’s Guide
Drawing the Entity-Relationship Diagram
Figure 8–2 E-R Diagram for Purchase Order Application
Customer has a one-to-many relationship with Purchase Order because a
customer can place one or many orders, but a given purchase order can be placed by
only one customer. The relationship is optional because zero customers may place a
given order. For example, an order may be placed by someone previously not defined
as a customer.
Purchase Order has a many-to-many relationship with Stock Item because a
purchase order can refer to many stock items, and a stock item can be referred to by
many purchase orders. However, you do not know which purchase orders refer to
which stock items. As a result, you introduce the notion of a line item. Purchase
Order has a one-to-many relationship with Line Item because a purchase order can
list many line items, but a given line item can be listed by only one purchase order.
Line Item has a many-to-one relationship with Stock Item because a line item can
refer to only one stock item, but a given stock item can be referred to by many line
items. The relationship is optional because zero line items may refer to a given stock
item.
Java Stored Procedures Application Example 8-3
Planning the Database Schema
Planning the Database Schema
After drawing the E-R diagram, you must devise a schema plan. To do this, you
decompose the E-R diagram into the following database tables:
■
Customers
■
Orders
■
LineItems
■
StockItems
For example, you can assign the attributes of the Customer entity to columns in the
Customers table.
Figure 8–3 depicts the relationships between tables. The E-R diagram showed that a
line item has a relationship with a purchase order and with a stock item. In the schema
plan, you establish these relationships using primary and foreign keys.
A primary key is a column or combination of columns whose values uniquely identify
each row in a table. A foreign key is a column or combination of columns whose
values match the primary key in some other table. For example, the PONo column in
the LineItems table is a foreign key matching the primary key in the Orders table.
Every purchase order number in the LineItems.PONo column must also appear in
the Orders.PONo column.
Figure 8–3 Schema Plan for Purchase Order Application
Creating the Database Tables
After planning the database schema, create the database tables required by the schema
plan. You begin by defining the Customers table, as follows:
CREATE TABLE Customers (
CustNo NUMBER(3) NOT NULL,
CustName VARCHAR2(30) NOT NULL,
Street VARCHAR2(20) NOT NULL,
City VARCHAR2(20) NOT NULL,
State CHAR(2) NOT NULL,
Zip VARCHAR2(10) NOT NULL,
Phone VARCHAR2(12),
PRIMARY KEY (CustNo)
);
8-4 Oracle Database Java Developer’s Guide
Writing the Java Classes
The Customers table stores information about customers. Essential information is
defined as NOT NULL. For example, every customer must have a shipping address.
However, the Customers table does not manage the relationship between a customer
and his or her purchase order. As a result, this relationship must be managed by the
Orders table, which you can define as follows:
CREATE TABLE Orders (
PONo NUMBER(5),
Custno NUMBER(3) REFERENCES Customers,
OrderDate DATE,
ShipDate DATE,
ToStreet VARCHAR2(20),
ToCity VARCHAR2(20),
ToState CHAR(2),
ToZip VARCHAR2(10),
PRIMARY KEY (PONo)
);
The E-R diagram in Figure 8–2 showed that line items have a relationship with
purchase orders and stock items. The LineItems table manages these relationships
using foreign keys. For example, the StockNo foreign key column in LineItems
references the StockNo primary key column in StockItems, which you can define as
follows:
CREATE TABLE StockItems (
StockNo NUMBER(4) PRIMARY KEY,
Description VARCHAR2(20),
Price NUMBER(6,2))
);
The Orders table manages the relationship between a customer and purchase order
using the CustNo foreign key column, which references the CustNo primary key
column in Customers. However, Orders does not manage the relationship between
a purchase order and its line items. As a result, this relationship must be managed by
LineItems, which you can define as follows:
CREATE TABLE LineItems (
LineNo NUMBER(2),
PONo NUMBER(5) REFERENCES Orders,
StockNo NUMBER(4) REFERENCES StockItems,
Quantity NUMBER(2),
Discount NUMBER(4,2),
PRIMARY KEY (LineNo, PONo)
);
Writing the Java Classes
After creating the database tables, you consider the operations required in a purchase
order system and write the appropriate Java methods. In a simple system based on the
tables defined in the preceding examples, you need methods for registering customers,
stocking parts, entering orders, and so on. You can implement these methods in a Java
class, POManager, as follows:
import java.sql.*;
import java.io.*;
import oracle.jdbc.*;
public class POManager
{
Java Stored Procedures Application Example 8-5
Writing the Java Classes
public static void addCustomer (int custNo, String custName, String street,
String city, String state, String zipCode, String phoneNo) throws SQLException
{
String sql = "INSERT INTO Customers VALUES (?,?,?,?,?,?,?)";
try
{
Connection conn = DriverManager.getConnection("jdbc:default:connection:");
PreparedStatement pstmt = conn.prepareStatement(sql);
pstmt.setInt(1, custNo);
pstmt.setString(2, custName);
pstmt.setString(3, street);
pstmt.setString(4, city);
pstmt.setString(5, state);
pstmt.setString(6, zipCode);
pstmt.setString(7, phoneNo);
pstmt.executeUpdate();
pstmt.close();
}
catch (SQLException e)
{
System.err.println(e.getMessage());
}
}
public static void addStockItem (int stockNo, String description, float price)
throws SQLException
{
String sql = "INSERT INTO StockItems VALUES (?,?,?)";
try
{
Connection conn = DriverManager.getConnection("jdbc:default:connection:");
PreparedStatement pstmt = conn.prepareStatement(sql);
pstmt.setInt(1, stockNo);
pstmt.setString(2, description);
pstmt.setFloat(3, price);
pstmt.executeUpdate();
pstmt.close();
}
catch (SQLException e)
{
System.err.println(e.getMessage());
}
}
public static void enterOrder (int orderNo, int custNo, String orderDate,
String shipDate, String toStreet, String toCity, String toState,
String toZipCode) throws SQLException
{
String sql = "INSERT INTO Orders VALUES (?,?,?,?,?,?,?,?)";
try
{
Connection conn = DriverManager.getConnection("jdbc:default:connection:");
PreparedStatement pstmt = conn.prepareStatement(sql);
pstmt.setInt(1, orderNo);
pstmt.setInt(2, custNo);
pstmt.setString(3, orderDate);
pstmt.setString(4, shipDate);
pstmt.setString(5, toStreet);
pstmt.setString(6, toCity);
pstmt.setString(7, toState);
8-6 Oracle Database Java Developer’s Guide
Writing the Java Classes
pstmt.setString(8, toZipCode);
pstmt.executeUpdate();
pstmt.close();
}
catch (SQLException e)
{
System.err.println(e.getMessage());
}
}
public static void addLineItem (int lineNo, int orderNo, int stockNo,
int quantity, float discount) throws SQLException
{
String sql = "INSERT INTO LineItems VALUES (?,?,?,?,?)";
try
{
Connection conn = DriverManager.getConnection("jdbc:default:connection:");
PreparedStatement pstmt = conn.prepareStatement(sql);
pstmt.setInt(1, lineNo);
pstmt.setInt(2, orderNo);
pstmt.setInt(3, stockNo);
pstmt.setInt(4, quantity);
pstmt.setFloat(5, discount);
pstmt.executeUpdate();
pstmt.close();
}
catch (SQLException e)
{
System.err.println(e.getMessage());
}
}
public static void totalOrders () throws SQLException
{
String sql = "SELECT O.PONo, ROUND(SUM(S.Price * L.Quantity)) AS TOTAL " +
"FROM Orders O, LineItems L, StockItems S " +
"WHERE O.PONo = L.PONo AND L.StockNo = S.StockNo " +
"GROUP BY O.PONo";
try
{
Connection conn = DriverManager.getConnection("jdbc:default:connection:");
PreparedStatement pstmt = conn.prepareStatement(sql);
ResultSet rset = pstmt.executeQuery();
printResults(rset);
rset.close();
pstmt.close();
}
catch (SQLException e)
{
System.err.println(e.getMessage());
}
}
static void printResults (ResultSet rset) throws SQLException
{
String buffer = "";
try
{
ResultSetMetaData meta = rset.getMetaData();
int cols = meta.getColumnCount(), rows = 0;
Java Stored Procedures Application Example 8-7
Writing the Java Classes
for (int i = 1; i <= cols; i++)
{
int size = meta.getPrecision(i);
String label = meta.getColumnLabel(i);
if (label.length() > size)
size = label.length();
while (label.length() < size)
label += " ";
buffer = buffer + label + " ";
}
buffer = buffer + "\n";
while (rset.next())
{
rows++;
for (int i = 1; i <= cols; i++)
{
int size = meta.getPrecision(i);
String label = meta.getColumnLabel(i);
String value = rset.getString(i);
if (label.length() > size)
size = label.length();
while (value.length() < size)
value += " ";
buffer = buffer + value + " ";
}
buffer = buffer + "\n";
}
if (rows == 0)
buffer = "No data found!\n";
System.out.println(buffer);
}
catch (SQLException e)
{
System.err.println(e.getMessage());
}
}
public static void checkStockItem (int stockNo) throws SQLException
{
String sql = "SELECT O.PONo, O.CustNo, L.StockNo, " +
"L.LineNo, L.Quantity, L.Discount " +
"FROM Orders O, LineItems L " +
"WHERE O.PONo = L.PONo AND L.StockNo = ?";
try
{
Connection conn = DriverManager.getConnection("jdbc:default:connection:");
PreparedStatement pstmt = conn.prepareStatement(sql);
pstmt.setInt(1, stockNo);
ResultSet rset = pstmt.executeQuery();
printResults(rset);
rset.close();
pstmt.close();
}
catch (SQLException e)
{
System.err.println(e.getMessage());
}
}
public static void changeQuantity (int newQty, int orderNo, int stockNo)
8-8 Oracle Database Java Developer’s Guide
Loading the Java Classes
throws SQLException
{
String sql = "UPDATE LineItems SET Quantity = ? " +
"WHERE PONo = ? AND StockNo = ?";
try
{
Connection conn = DriverManager.getConnection("jdbc:default:connection:");
PreparedStatement pstmt = conn.prepareStatement(sql);
pstmt.setInt(1, newQty);
pstmt.setInt(2, orderNo);
pstmt.setInt(3, stockNo);
pstmt.executeUpdate();
pstmt.close();
}
catch (SQLException e)
{
System.err.println(e.getMessage());
}
}
public static void deleteOrder (int orderNo) throws SQLException
{
String sql = "DELETE FROM LineItems WHERE PONo = ?";
try
{
Connection conn = DriverManager.getConnection("jdbc:default:connection:");
PreparedStatement pstmt = conn.prepareStatement(sql);
pstmt.setInt(1, orderNo);
pstmt.executeUpdate();
sql = "DELETE FROM Orders WHERE PONo = ?";
pstmt = conn.prepareStatement(sql);
pstmt.setInt(1, orderNo);
pstmt.executeUpdate();
pstmt.close();
}
catch (SQLException e)
{
System.err.println(e.getMessage());
}
}
}
Loading the Java Classes
After writing the Java classes, use the loadjava command-line utility to upload your
Java stored procedures into Oracle Database, as follows:
> loadjava -u scott@myPC:1521:orcl -v -r -t POManager.java
Password: password
initialization complete
loading : POManager
creating : POManager
resolver : resolver ( ("*" scott) ("*" public) ("*" -) )
resolving: POManager
The -v option enables the verbose mode, the -r option compiles uploaded Java source
files and resolves external references in the classes, and the -t option tells loadjava
to connect to the database using the client-side JDBC Thin driver.
Java Stored Procedures Application Example 8-9
Publishing the Java Classes
Publishing the Java Classes
After loading the Java classes, publish your Java stored procedures in the Oracle data
dictionary. To do this, you must write call specifications that map Java method names,
parameter types, and return types to their SQL counterparts.
The methods in the POManager Java class are logically related. You can group their
call specifications in a PL/SQL package. To do this, first, create the package
specification, as follows:
CREATE OR REPLACE PACKAGE po_mgr AS
PROCEDURE add_customer (cust_no NUMBER, cust_name VARCHAR2,
street VARCHAR2, city VARCHAR2, state CHAR, zip_code VARCHAR2,
phone_no VARCHAR2);
PROCEDURE add_stock_item (stock_no NUMBER, description VARCHAR2,
price NUMBER);
PROCEDURE enter_order (order_no NUMBER, cust_no NUMBER,
order_date VARCHAR2, ship_date VARCHAR2, to_street VARCHAR2,
to_city VARCHAR2, to_state CHAR, to_zip_code VARCHAR2);
PROCEDURE add_line_item (line_no NUMBER, order_no NUMBER,
stock_no NUMBER, quantity NUMBER, discount NUMBER);
PROCEDURE total_orders;
PROCEDURE check_stock_item (stock_no NUMBER);
PROCEDURE change_quantity (new_qty NUMBER, order_no NUMBER,
stock_no NUMBER);
PROCEDURE delete_order (order_no NUMBER);
END po_mgr;
Then, create the package body by writing call specifications for the Java methods, as
follows:
CREATE OR REPLACE PACKAGE BODY po_mgr AS
PROCEDURE add_customer (cust_no NUMBER, cust_name VARCHAR2,
street VARCHAR2, city VARCHAR2, state CHAR, zip_code VARCHAR2,
phone_no VARCHAR2) AS LANGUAGE JAVA
NAME 'POManager.addCustomer(int, java.lang.String,
java.lang.String, java.lang.String, java.lang.String,
java.lang.String, java.lang.String)';
PROCEDURE add_stock_item (stock_no NUMBER, description VARCHAR2,
price NUMBER) AS LANGUAGE JAVA
NAME 'POManager.addStockItem(int, java.lang.String, float)';
PROCEDURE enter_order (order_no NUMBER, cust_no NUMBER,
order_date VARCHAR2, ship_date VARCHAR2, to_street VARCHAR2,
to_city VARCHAR2, to_state CHAR, to_zip_code VARCHAR2)
AS LANGUAGE JAVA
NAME 'POManager.enterOrder(int, int, java.lang.String,
java.lang.String, java.lang.String, java.lang.String,
java.lang.String, java.lang.String)';
PROCEDURE add_line_item (line_no NUMBER, order_no NUMBER,
stock_no NUMBER, quantity NUMBER, discount NUMBER)
AS LANGUAGE JAVA
NAME 'POManager.addLineItem(int, int, int, int, float)';
PROCEDURE total_orders
AS LANGUAGE JAVA
NAME 'POManager.totalOrders()';
PROCEDURE check_stock_item (stock_no NUMBER)
8-10 Oracle Database Java Developer’s Guide
Calling the Java Stored Procedures
AS LANGUAGE JAVA
NAME 'POManager.checkStockItem(int)';
PROCEDURE change_quantity (new_qty NUMBER, order_no NUMBER,
stock_no NUMBER) AS LANGUAGE JAVA
NAME 'POManager.changeQuantity(int, int, int)';
PROCEDURE delete_order (order_no NUMBER)
AS LANGUAGE JAVA
NAME 'POManager.deleteOrder(int)';
END po_mgr;
Calling the Java Stored Procedures
After publishing the Java classes, call your Java stored procedures from the top level
and from database triggers, SQL data manipulation language (DML) statements, and
PL/SQL blocks. Use the dot notation to reference these stored procedures in the
po_mgr package.
From an anonymous PL/SQL block, you may start the new purchase order system by
stocking parts, as follows:
BEGIN
po_mgr.add_stock_item(2010,
po_mgr.add_stock_item(2011,
po_mgr.add_stock_item(2012,
po_mgr.add_stock_item(2013,
po_mgr.add_stock_item(2014,
po_mgr.add_stock_item(2015,
po_mgr.add_stock_item(2016,
po_mgr.add_stock_item(2017,
po_mgr.add_stock_item(2018,
po_mgr.add_stock_item(2019,
po_mgr.add_stock_item(2020,
po_mgr.add_stock_item(2021,
po_mgr.add_stock_item(2022,
po_mgr.add_stock_item(2023,
po_mgr.add_stock_item(2024,
po_mgr.add_stock_item(2025,
po_mgr.add_stock_item(2026,
po_mgr.add_stock_item(2027,
COMMIT;
END;
'camshaft', 245.00);
'connecting rod', 122.50);
'crankshaft', 388.25);
'cylinder head', 201.75);
'cylinder sleeve', 73.50);
'engine bearning', 43.85);
'flywheel', 155.00);
'freeze plug', 17.95);
'head gasket', 36.75);
'lifter', 96.25);
'oil pump', 207.95);
'piston', 137.75);
'piston ring', 21.35);
'pushrod', 110.00);
'rocker arm', 186.50);
'valve', 68.50);
'valve spring', 13.25);
'water pump', 144.50);
Register your customers, as follows:
BEGIN
po_mgr.add_customer(101, 'A-1 Automotive', '4490 Stevens Blvd',
'San Jose', 'CA', '95129', '408-555-1212');
po_mgr.add_customer(102, 'AutoQuest', '2032 America Ave',
'Hayward', 'CA', '94545', '510-555-1212');
po_mgr.add_customer(103, 'Bell Auto Supply', '305 Cheyenne Ave',
'Richardson', 'TX', '75080', '972-555-1212');
po_mgr.add_customer(104, 'CarTech Auto Parts', '910 LBJ Freeway',
'Dallas', 'TX', '75234', '214-555-1212');
COMMIT;
END;
Enter the purchase orders placed by various customers, as follows:
Java Stored Procedures Application Example 8-11
Calling the Java Stored Procedures
BEGIN
po_mgr.enter_order(30501, 103, '14-SEP-1998', '21-SEP-1998',
'305 Cheyenne Ave', 'Richardson', 'TX', '75080');
po_mgr.add_line_item(01, 30501, 2011, 5, 0.02);
po_mgr.add_line_item(02, 30501, 2018, 25, 0.10);
po_mgr.add_line_item(03, 30501, 2026, 10, 0.05);
po_mgr.enter_order(30502, 102, '15-SEP-1998', '22-SEP-1998',
'2032 America Ave', 'Hayward', 'CA', '94545');
po_mgr.add_line_item(01, 30502, 2013, 1, 0.00);
po_mgr.add_line_item(02, 30502, 2014, 1, 0.00);
po_mgr.enter_order(30503, 104, '15-SEP-1998', '23-SEP-1998',
'910 LBJ Freeway', 'Dallas', 'TX', '75234');
po_mgr.add_line_item(01, 30503, 2020, 5, 0.02);
po_mgr.add_line_item(02, 30503, 2027, 5, 0.02);
po_mgr.add_line_item(03, 30503, 2021, 15, 0.05);
po_mgr.add_line_item(04, 30503, 2022, 15, 0.05);
po_mgr.enter_order(30504, 101, '16-SEP-1998', '23-SEP-1998',
'4490 Stevens Blvd', 'San Jose', 'CA', '95129');
po_mgr.add_line_item(01, 30504, 2025, 20, 0.10);
po_mgr.add_line_item(02, 30504, 2026, 20, 0.10);
COMMIT;
END;
In SQL*Plus, after redirecting output to the SQL*Plus text buffer, you can call the
totalOrders() method, as follows:
SQL> SET SERVEROUTPUT ON
SQL> CALL dbms_java.set_output(2000);
...
SQL> CALL po_mgr.total_orders();
PONO
TOTAL
30501 1664
30502 275
30503 4149
30504 1635
Call completed.
8-12 Oracle Database Java Developer’s Guide
9
Oracle Database Java Application
Performance
You can enhance the performance of your Java application using the following:
■
Oracle JVM Just-in-Time Compiler (JIT)
■
Java Memory Usage
Oracle JVM Just-in-Time Compiler (JIT)
This section describes the just-in-time (JIT) compiler introduced in Oracle Database
11g release 1 (11.1). This section covers the following topics:
■
Overview of Oracle JVM JIT
■
Advantages of JIT Compilation
■
Methods Introduced in Oracle Database 11g
The JIT compiler is a replacement of the compilers that were
used in the earlier versions of Oracle Database.
Note:
Overview of Oracle JVM JIT
Starting with Oracle 11g release 1 (11.1), there is a just-in-time(JIT) compiler for Oracle
JVM environment. A JIT compiler for Oracle JVM enables much faster execution
because, it manages the invalidation, recompilation, and storage of code without an
external mechanism. Based on dynamically gathered profiling data, this compiler
transparently selects Java methods to compile the native machine code and
dynamically makes them available to running Java sessions. Additionally, the
compiler can take advantage of Oracle JVM's class resolution model to optionally
persist compiled Java methods across database calls, sessions, or instances. Such
persistence avoids the overhead of unnecessary recompilations across sessions or
instances, when it is known that semantically the Java code has not changed.
The JIT compiler is controlled by a new boolean-valued initialization parameter called
java_jit_enabled. When running heavily used Java methods with
java_jit_enabled parameter value as true, the Java methods are automatically
compiled to native code by the JIT compiler and made available for use by all sessions
in the instance. The VM automatically recompiles native code for Java methods when
necessary, such as following reresolution of the containing Java class.
The JIT compiler runs as an MMON slave, in a single background process for the
instance. So, while the JIT compiler is running and actively compiling methods, you
Oracle Database Java Application Performance 9-1
Oracle JVM Just-in-Time Compiler (JIT)
may see this background process consuming CPU and memory resources on par with
an active user Java session.
Advantages of JIT Compilation
The following are the advantages of using JIT compilation over the compilation
techniques used in earlier versions of Oracle database:
■
JIT compilation works transparently
■
JIT compilation speeds up the performance of Java classes
■
■
JIT stored compiled code avoids recompilation of Java programs across sessions or
instances when it is known that semantically the Java code has not changed.
JIT compilation does not require a C compiler
Methods Introduced in Oracle Database 11g
In 11g release 1 (11.1), the DBMS_JAVA package has been enhanced with the following
new public methods to provide Java entrypoints for controlling synchronous method
compilation and reverting to interpreted method execution:
set_native_compiler_option
This procedure sets a native-compiler option to the specified value for the current
schema. If the option given by optionName is not allowed to have duplicate values,
then the value is ignored.
PROCEDURE set_native_compiler_option(optionName VARCHAR2,
value VARCHAR2);
unset_native_compiler_option
This procedure unsets a native-compiler option/value pair for the current schema. If
the option given by optionName is not allowed to have duplicate values, then the value
is ignored.
PROCEDURE unset_native_compiler_option(optionName VARCHAR2,
value VARCHAR2);
compile_class
This function compiles all methods defined by the class that is identified by classname
in the current schema. It returns the number of methods successfully compiled. If the
class does not exist, then an ORA-29532 (Uncaught Java exception) occurs.
FUNCTION compile_class(classname VARCHAR2) return NUMBER;
compile_class
This function compiles all methods defined by the class that is identified by classname
in the supplied schema. It returns the number of methods successfully compiled. If the
class does not exist in the schema or the schema does not exist, then an ORA-29532
(Uncaught Java exception) occurs.
FUNCTION compile_class(schema VARCHAR2,
classname VARCHAR2) return NUMBER;
9-2 Oracle Database Java Developer’s Guide
Oracle JVM Just-in-Time Compiler (JIT)
uncompile_class
This function uncompiles all methods defined by the class that is identified by
classname in the current schema. It returns the number of methods successfully
uncompiled. If the value of the argument permanentp is nonzero, then mark these
methods as permanently dynamically uncompilable. Otherwise, they are eligible for
future dynamic recompilation. If the class does not exist, then an ORA-29532
(Uncaught Java exception) occurs.
FUNCTION uncompile_class(classname VARCHAR2,
permanentp NUMBER default 0) return NUMBER;
uncompile_class
This function uncompiles all methods defined by the class that is identified by
classname in the supplied schema. It returns the number of methods successfully
uncompiled. If the value of the argument permanentp is nonzero, then mark these
methods as permanently dynamically uncompilable. Otherwise, they are eligible for
future dynamic recompilation. If the class does not exist in the schema or the schema
does not exist, then an ORA-29532 (Uncaught Java exception) occurs.
FUNCTION uncompile_class(schema VARCHAR2,
classname VARCHAR2,
permanentp NUMBER default 0) return NUMBER;
compile_method
This function compiles the method specified by name and Java type signatures defined
by the class, which is identified by classname in the current schema. It returns the
number of methods successfully compiled. If the class does not exist, then an
ORA-29532 (Uncaught Java exception) occurs.
FUNCTION compile_method(classname VARCHAR2,
methodname VARCHAR2,
methodsig VARCHAR2) return NUMBER;
compile_method
This function compiles the method specified by name and Java type signatures defined
by the class that is identified by classname in the supplied schema. It returns the
number of methods successfully compiled. If the class does not exist in the schema or
the schema does not exist, then an ORA-29532 (Uncaught Java exception)
occurs.
FUNCTION compile_method(schema VARCHAR2,
classname VARCHAR2,
methodname VARCHAR2,
methodsig VARCHAR2) return NUMBER;
uncompile_method
This function uncompiles the method specified by the name and Java type signatures
defined by the class that is identified by classname in the current schema. It returns the
number of methods successfully uncompiled. If the value of the argument permanentp
is nonzero, then mark the method as permanently dynamically uncompilable.
Otherwise, it is eligible for future dynamic recompilation. If the class does not exist,
then an ORA-29532 (Uncaught Java exception) occurs.
FUNCTION uncompile_method(classname
VARCHAR2,
Oracle Database Java Application Performance 9-3
Java Memory Usage
methodname VARCHAR2,
methodsig VARCHAR2,
permanentp NUMBER default 0) return NUMBER;
uncompile_method
This function uncompiles the method specified by the name and Java type signatures
defined by the class that is identified by classname in the supplied schema. It returns
the number of methods successfully uncompiled. If the value of the argument
permanentp is nonzero, then mark the method as permanently dynamically
uncompilable. Otherwise, it is eligible for future dynamic recompilation. If the class
does not exist in the schema or the schema does not exist, then an ORA-29532
(Uncaught Java exception) occurs.
FUNCTION uncompile_method(schema VARCHAR2,
classname VARCHAR2,
methodname VARCHAR2,
methodsig VARCHAR2,
permanentp NUMBER default 0) return NUMBER;
Java Memory Usage
The typical and custom database installation process furnishes a database that has
been configured for reasonable Java usage during development. However, run-time
use of Java should be determined by the usage of system resources for a given
deployed application. Resources you use during development can vary widely,
depending on your activity. The following sections describe how you can configure
memory, how to tell how much System Global Area (SGA) memory you are using,
and what errors denote a Java memory issue:
■
Configuring Memory Initialization Parameters
■
Java Pool Memory
■
Displaying Used Amounts of Java Pool Memory
■
Correcting Out of Memory Errors
Configuring Memory Initialization Parameters
You can modify the following database initialization parameters to tune your memory
usage to reflect your application needs more accurately:
■
SHARED_POOL_SIZE
Shared pool memory is used by the class loader within the JVM. The class loader,
on an average, uses about 8 KB of memory for each loaded class. Shared pool
memory is used when loading and resolving classes into the database. It is also
used when compiling the source in the database or when using Java resource
objects in the database.
The memory specified in SHARED_POOL_SIZE is consumed transiently when you
use loadjava. The database initialization process requires SHARED_POOL_SIZE
to be set to 96 MB because it loads the Java binaries for approximately 8,000 classes
and resolves them. The SHARED_POOL_SIZE resource is also consumed when you
create call specifications and as the system tracks dynamically loaded Java classes
at run time.
■
JAVA_POOL_SIZE
9-4 Oracle Database Java Developer’s Guide
Java Memory Usage
Oracle JVM memory manager uses JAVA_POOL_SIZE mainly for in-memory
representation of Java method and class definitions, and static Java states that are
migrated to session space at end-of-call in shared server mode. In the first case,
you will be sharing the memory cost with all Java users. In the second case, the
value of JAVA_POOL_SIZE varies according to the actual amount of state held in
static variables for each session. But, Oracle recommends the minimum value as 50
MB.
■
JAVA_SOFT_SESSIONSPACE_LIMIT
This parameter lets you specify a soft limit on Java memory usage in a session,
which will warn you if you must increase your Java memory limits. Every time
memory is allocated, the total memory allocated is checked against this limit.
When a user's session Java state exceeds this size, Oracle JVM generates a warning
that is written into the trace files. Although this warning is an informational
message and has no impact on your application, you should understand and
manage the memory requirements of your deployed classes, especially as they
relate to usage of session space.
■
JAVA_MAX_SESSIONSPACE_SIZE
If a Java program, which can be called by a user, running in the server can be used
in a way that is not self-limiting in its memory usage, then this setting may be
useful to place a hard limit on the amount of session space made available to it.
The default is 4 GB. This limit is purposely set extremely high to be normally
invisible.
When a user's session Java state attempts to exceeds this size, the application can
receive an out-of-memory failure.
Initializing Pool Sizes within Database Templates
You can set the defaults for JAVA_POOL_SIZE and SHARED_POOL_SIZE in the
database installation template.
Figure 9–1 illustrates how the Database Configuration Assistant enables you to modify
these values in the Memory section.
Oracle Database Java Application Performance 9-5
Java Memory Usage
Figure 9–1 Configuring Oracle JVM Memory Parameters
Java Pool Memory
Java pool memory is used in server memory for all session-specific Java code and data
within the JVM. Java pool memory is used in different ways, depending on what
mode Oracle Database server is running in.
Java Pool Memory Used within a Dedicated Server
The following is what constitutes the Java pool memory used within a dedicated
server:
■
The shared part of each Java class used per session.
This includes read-only memory, such as code vectors, and methods. In total, this
can average about 4 KB to 8 KB for each class.
■
None of the per-session Java state of each session.
For a dedicated server, this is stored in the User Global Area (UGA) within the
Program Global Area (PGA), and not within the SGA.
Under dedicated servers, the total required Java pool memory depends on the
applications running and may range between 10 and 50 MB.
Java Pool Memory Used within a Shared Server
The following is what constitutes the Java pool memory used within a shared server:
■
The shared part of each Java class that is used per session.
This includes read-only memory, such as vectors, and methods. In total, this can
average about 4 KB to 8 KB for each class.
■
Some of the UGA used for per-session state of each session is allocated from the
Java pool memory within the SGA
9-6 Oracle Database Java Developer’s Guide
Java Memory Usage
Because the Java pool memory size is fixed, you must estimate the total
requirement for your applications and multiply by the number of concurrent
sessions the applications want to create, to calculate the total amount of necessary
Java pool memory. Each UGA grows and shrinks as necessary. However, all
UGAs combined must be able to fit within the entire fixed Java pool space.
Under shared servers, this figure could be large. Java-intensive, multiuser benchmarks
could require more than 100 MB.
If you are compiling code on the server, rather than compiling
on the client and loading to the server, then you might need a bigger
JAVA_POOL_SIZE than the default 20 MB.
Note:
Displaying Used Amounts of Java Pool Memory
You can find out how much of Java pool memory is being used by viewing the
V$SGASTAT table. Its rows include pool, name, and bytes. Specifically, the last two
rows show the amount of Java pool memory used and how much is free. The total of
these two items equals the number of bytes that you configured in the database
initialization file.
SVRMGR> select * from v$sgastat;
POOL
NAME
BYTES
----------- -------------------------- ---------fixed_sga
69424
db_block_buffers
2048000
log_buffer
524288
shared pool free memory
22887532
shared pool miscellaneous
559420
shared pool character set object
64080
shared pool State objects
98504
shared pool message pool freequeue
231152
shared pool PL/SQL DIANA
2275264
shared pool db_files
72496
shared pool session heap
59492
shared pool joxlod: init P
7108
shared pool PLS non-lib hp
2096
shared pool joxlod: in ehe
4367524
shared pool VIRTUAL CIRCUITS
162576
shared pool joxlod: in phe
2726452
shared pool long op statistics array
44000
shared pool table definiti
160
shared pool KGK heap
4372
shared pool table columns
148336
shared pool db_block_hash_buckets
48792
shared pool dictionary cache
1948756
shared pool fixed allocation callback
320
shared pool SYSTEM PARAMETERS
63392
shared pool joxlod: init s
7020
shared pool KQLS heap
1570992
shared pool library cache
6201988
shared pool trigger inform
32876
shared pool sql area
7015432
shared pool sessions
211200
shared pool KGFF heap
1320
shared pool joxs heap init
4248
shared pool PL/SQL MPCODE
405388
shared pool event statistics per sess
339200
Oracle Database Java Application Performance 9-7
Java Memory Usage
shared pool db_block_buffers
java pool
free memory
java pool
memory in use
37 rows selected.
136000
30261248
19742720
Correcting Out of Memory Errors
If you run out of memory while loading classes, then it can fail silently, leaving invalid
classes in the database. Later, if you try to call or resolve any invalid classes, then a
ClassNotFoundException or NoClassDefFoundException instance will be
thrown at run time. You would get the same exceptions if you were to load corrupted
class files. You should perform the following:
■
■
■
■
Verify that the class was actually included in the set you are loading to the server.
Use the loadjava -force option to force the new class being loaded to replace
the class already resident in the server.
Use the loadjava -resolve option to attempt resolution of a class during the
load process. This enables you to catch missing classes at load time, rather than at
run time.
Double check the status of the newly loaded class by connecting to the database in
the schema containing the class, and run the following:
SELECT * FROM user_objects WHERE object_name = dbms_java.shortname('');
The STATUS field should be VALID. If loadjava complains about memory
problems or failures, such as lost connection, then increase SHARED_POOL_SIZE
and JAVA_POOL_SIZE, and try again.
9-8 Oracle Database Java Developer’s Guide
10
Security for Oracle Database Java
Applications
Security is a large arena that includes network security for the connection, access, and
execution control of operating system resources or of Java virtual machine
(JVM)-defined and user-defined classes. Security also includes bytecode verification of
Java Archive (JAR) files imported from an external source. The following sections
describe the various security support available for Java applications within Oracle
Database:
■
Network Connection Security
■
Database Contents and Oracle JVM Security
■
Database Authentication Mechanisms
Network Connection Security
The two major aspects to network security are authentication and data confidentiality.
The type of authentication and data confidentiality is dependent on how you connect
to the database, either through Oracle Net or Java Database Connectivity (JDBC)
connection. The following table provides the security description for Oracle Net and
JDBC connections:
Connection Security
Description
Oracle Net
The database can require both authentication and authorization
before allowing a user to connect to it. Oracle Net database
connection security can require one or more of the following:
■
■
■
JDBC
A user name and password for client verification. For each
connection request, a user name and password configured
within Oracle Net has to be provided.
Advanced Networking Option for encryption, kerberos, or
secureId.
SSL for certificate authentication.
The JDBC connection security that is required is similar to the
constraints required on an Oracle Net database connection.
See Also:
■
Oracle Database Net Services Administrator's Guide
■
Oracle Database Advanced Security Administrator's Guide
■
Oracle Database JDBC Developer's Guide and Reference
Security for Oracle Database Java Applications 10-1
Database Contents and Oracle JVM Security
Database Contents and Oracle JVM Security
Once you are connected to the database, you must have the appropriate Java2 security
permissions and database privileges to access the resources stored within the database.
These resources include:
■
Database resources, such as tables and PL/SQL packages
■
Operating system resources, such as files and sockets
■
Oracle JVM classes
■
User-loaded classes
These resources can be protected by the following methods:
Resource Security
Description
Database Resource
Security
Authorization for database resources requires that database privileges,
which are not the same as the Java2 security permissions, are granted
to resources. For example, database resources include tables, classes,
and PL/SQL packages.
All user-defined classes are secured against users from other schemas.
You can grant execution permission to other users or schemas through
an option on the loadjava command.
JVM Security
Oracle JVM uses Java2 security, which uses Permission objects to
protect operating system resources. Java2 security is automatically
installed upon startup and protects all operating system resources and
Oracle JVM classes from all users, except JAVA_ADMIN. The
JAVA_ADMIN user can grant permission to other users to access these
classes.
This section covers the following topics:
■
Java2 Security
■
Setting Permissions
■
Debugging Permissions
■
Permission for Loading Classes
See Also:
■
Oracle Database Advanced Application Developer's Guide
■
Chapter 11, "Schema Objects and Oracle JVM Utilities"
Java2 Security
Each user or schema must be assigned the proper permissions to access operating
system resources, such as sockets, files, and system properties.
Java2 security provides a flexible and configurable security for Java applications. With
Java2 security, you can define exactly what permissions on each loaded object that a
schema or role will have. In Oracle8i Database release 8.1.5, the following secure roles
are available:
■
JAVAUSERPRIV
Few permissions, including examining properties
■
JAVASYSPRIV
Major permissions, including updating Oracle JVM-protected packages
10-2 Oracle Database Java Developer’s Guide
Database Contents and Oracle JVM Security
Both roles still exist within this release for backward
compatibility. However, Oracle recommends that you specify each
permission explicitly, rather than utilize these roles.
Note:
Because Oracle JVM security is based on Java2 security, you assign permissions on a
class-by-class basis. These permissions are assigned through database management
tools. Each permission is encapsulated in a Permission object and is stored within a
Permission table. Permission contains the target and action attributes, which
take String values.
Java2 security was created for the non-database world. When you apply the Java2
security model within the database, certain differences manifest themselves. For
example, Java2 security defines that all applets are implicitly untrusted and all classes
within the CLASSPATH are trusted. In Oracle Database, all classes are loaded within a
secure database. As a result, no classes are trusted.
The following table describes the differences between the Sun Microsystems Java2
security and Oracle Database security implementation:
Java2 Security Standard
Oracle Database Security Implementation
Java classes located within the CLASSPATH
are trusted.
All Java classes are loaded within the database.
Classes are trusted on a class-by-class basis
according to the permission granted.
You can specify the policy using the
-usepolicy flag on the java command.
You must specify the policy within
PolicyTable.
You can write your own SecurityManager You can write your own SecurityManager.
or use the Launcher.
However, Oracle recommends that you use
only Oracle Database SecurityManager or
that you extend it. If you want to modify the
behavior, then you should not define a
SecurityManager. Instead, you should
extend oracle.aurora.rdbms.
SecurityManagerImpl and override specific
methods.
SecurityManager is not initialized by
default. You must initialize
SecurityManager.
Oracle JVM always initializes
SecurityManager at startup.
Permissions are determined by the location
or the URL, where the application or applet
is loaded, or keycode, that is, signed code.
Permissions are determined by the schema in
which the class is loaded. Oracle Database does
not support signed code.
The security policy is defined in a file.
The PolicyTable definition is contained in a
secure database table.
You can update the security policy file using You can update PolicyTable through
DBMS_JAVA procedures. After initialization,
a text editor or a tool, if you have the
only JAVA_ADMIN has permission to modify
appropriate permissions.
PolicyTable. JAVA_ADMIN must grant you
the right to modify PolicyTable so that you
can grant permissions to others.
Permissions are assigned to a protection
domain, which classes can belong to.
All classes within the same schema are in the
same protection domain.
Security for Oracle Database Java Applications 10-3
Database Contents and Oracle JVM Security
Java2 Security Standard
Oracle Database Security Implementation
You can use the CodeSource class for
identifying code.
You can use the CodeSource class for
identifying schema.
■
■
The equals() method returns true if
the URL and certificates are equal.
The implies() method returns true if
the first CodeSource is a generic
representation that includes the specific
CodeSource object.
Supports positive permissions only, that is,
grant.
■
■
The equals() method returns true if the
schemas are the same.
The implies() method returns true if
the schemas are the same.
Supports both positive and limitation
permissions, that is, grant and restrict.
Setting Permissions
As with Java2 security, Oracle Database supports the security classes. Normally, you
set the permissions for the code base either using a tool or by editing the security
policy file. In Oracle Database, you set the permissions dynamically using DBMS_JAVA
procedures, which modify a policy table in the database.
Two views have been created for you to view the policy table, USER_JAVA_POLICY
and DBA_JAVA_POLICY. Both views contain information about granted and limitation
permissions. The DBA_JAVA_POLICY view can see all rows within the policy table.
The USER_JAVA_POLICY view can see only permissions relevant to the current user.
The following is a description of the rows within each view:
Table Column
Description
Kind
GRANT or RESTRICT. Shows whether this permission is a positive or a
limitation permission.
Grantee
The name of the user, schema, or role to which the Permission object
is assigned.
Permission_schema
The schema in which the Permission object is loaded.
Permission_type
The Permission class type, which is designated by a string
containing the full class name, such as, java.io.FilePermission.
Permission_name
The target attribute of the Permission object. You use this when
defining the permission. When defining the target for a Permission
object of type PolicyTablePermission, the name can become quite
complicated.
See Also: "Acquiring Administrative Permission to Update Policy
Table" on page 10-8
Permission_action
The action attribute of the Permission object. Many permissions
expect a null value if no action is appropriate for the permission.
Status
ENABLED and DISABLED. After creating a row for a Permission
object, you can disable or reenable it. This column shows whether the
permission is enabled or disabled.
Key
Sequence number you use to identify this row. This number should be
supplied when disabling, enabling, or deleting a permission.
There are two ways to set permissions:
■
Fine-Grain Definition for Each Permission
■
General Permission Definition Assigned to Roles
10-4 Oracle Database Java Developer’s Guide
Database Contents and Oracle JVM Security
Note: For absolute certainty about the security settings, implement
the fine-grain definition. The general definition is easy to implement,
but you may not get the exact security settings you require.
Fine-Grain Definition for Each Permission
Using fine-grain definition, you can grant each permission individually to specific
users or roles. If you do not grant a permission for access, then the schema will be
denied access. To set individual permissions within the policy table, you must provide
the following information:
Parameter
Description
Grantee
The name of the user, schema, or role to which you want the grant to
apply. PUBLIC specifies that the row applies to all users.
Permission type
The Permission class on which you are granting permission. For
example, if you were defining access to a file, the permission type
would be FilePermission. This parameter requires a fully-qualified
name of a class that extends java.lang.security.Permission. If
the class is not within SYS, then the name should be prefixed by
schema:. For example, mySchema:myPackage.MyPermission is a
valid name for a user-generated permission.
Permission name
The meaning of the target attribute as defined by the Permission
class. Examine the appropriate Permission class for the relevant
name.
Permission action
The type of action that you can specify. This can vary according to the
permission type. For example, FilePermission can have the action,
read or write.
Key
Number returned from grant or limit to use on enable, disable, or
delete methods.
You can grant permissions using either SQL or Java. Each version returns a row key
identifier that identifies the row within the permission table. In the Java version of
DBMS_JAVA, each method returns the row key identifier, either as a returned
parameter or as an OUT variable in the parameter list. In the PL/SQL DBMS_JAVA
package, the row key is returned only in the procedure that defines the key OUT
parameter. This key is used to enable and disable specific permissions.
After running the grant, if a row already exists for the exact permission, then no
update occurs, but the key for that row is returned. If the row was disabled, then
running the grant enables the existing row.
If you are granting FilePermission, then you must provide
the physical name of the directory or file, such as /private/oracle.
You cannot provide either an environment variable, such as
$ORACLE_HOME, or a symbolic link. To denote all files within a
directory, provide the * symbol, as follows:
Note:
/private/oracle/*
To denote all directories and files within a directory, provide the symbol, as follows:
/private/oracle/-
Security for Oracle Database Java Applications 10-5
Database Contents and Oracle JVM Security
You can grant permissions using the DBMS_JAVA package, as follows:
procedure grant_permission ( grantee varchar2, permission_type varchar2,
permission_name varchar2, permission_action varchar2 )
procedure grant_permission ( grantee varchar2, permission_type varchar2,
permission_name varchar2, permission_action varchar2, key OUT number)
You can grant permissions using Java, as follows:
long oracle.aurora.rdbms.security.PolicyTableManager.grant ( java.lang.String
grantee, java.lang.String permission_type, java.lang.String permission_name,
java.lang.String permission_action);
void oracle.aurora.rdbms.security.PolicyTableManager.grant ( java.lang.String
grantee, java.lang.String permission_type, java.lang.String permission_name,
java.lang.String permission_action, long[] key);
You can limit permissions using the DBMS_JAVA package, as follows:
procedure restrict_permission ( grantee varchar2, permission_type varchar2,
permission_name varchar2, permission_action varchar2)
procedure restrict_permission ( grantee varchar2, permission_type varchar2,
permission_name varchar2, permission_action varchar2, key OUT number)
You can limit permissions using Java, as follows:
long oracle.aurora.rdbms.security.PolicyTableManager.restrict ( java.lang.String
grantee, java.lang.String permission_type, java.lang.String permission_name,
java.lang.String permission_action);
void oracle.aurora.rdbms.security.PolicyTableManager.restrict ( java.lang.String
grantee, java.lang.String permission_type, java.lang.String permission_name,
java.lang.String permission_action, long[] key);
Example 10–1 shows how to use the grant_permission() method to grant
permissions. Example 10–2 shows how to limit permissions using the restrict()
method.
Example 10–1
Granting Permissions
Assuming that you have appropriate permissions to modify the policy table, you can
use the grant_permission() method, which is in the DBMS_JAVA package, to
modify PolicyTable to allow user access to the indicated file. In this example, the
user, Larry, has modification permission on PolicyTable. Within a SQL package,
Larry can grant permission to Dave to read and write a file, as follows:
connect larry
Enter password: password
REM Grant DAVE permission to read and write the Test1 file.
call dbms_java.grant_permission('DAVE', 'java.io.FilePermission', '/test/Test1',
'read,write');
REM commit the changes to PolicyTable
commit;
10-6 Oracle Database Java Developer’s Guide
Database Contents and Oracle JVM Security
Example 10–2
Limiting Permissions
You can use the restrict() method to specify a limitation or exception to general
rules. A general rule is a rule where, in most cases, the permission is true or granted.
However, there may be exceptions to this rule. For these exceptions, you specify a
limitation permission.
If you have defined a general rule that no one can read or write an entire directory,
then you can define a limitation on an aspect of this rule through the restrict()
method. For example, if you want to allow access to all files within the /tmp directory,
except for your password file that exists in that directory, then you would grant
permission for read and write to all files within /tmp and limit read and write access
to the password file.
If you want to specify an exception to the limitation, then you need to create an
explicit grant permission to override the limitation permission. In the previously
mentioned scenario, if you want the file owner to still be able to modify the password
file, then you can grant a more explicit permission to allow access to one user, which
will override the limitation. Oracle JVM security combines all rules to understand who
really has access to the password file. This is demonstrated in the following diagram:
Grant PUBLIC permission to /tmp/*
/tmp % ls -al
.
..
...
password
test
myCode.java
myCode.class
updSQL.sqlj
Makefile
limitation permission to PUBLIC
grant permission assigned to owner that
overrides the above limitation
The explicit rule is as follows:
If the limitation permission implies the request, then for a grant permission to be
effective, the limitation permission must also imply the grant.
The following code implements this example:
connect larry
Enter password: password
REM Grant permission to all users (PUBLIC) to be able to read and write
REM all files in /tmp.
call dbms_java.grant_permission('PUBLIC', 'java.io.FilePermission', '/tmp/*',
'read,write');
REM Limit permission to all users (PUBLIC) from reading or writing the
REM password file in /tmp.
call dbms_java.restrict_permission('PUBLIC', 'java.io.FilePermission',
'/tmp/password', 'read,write');
REM By providing a more specific rule that overrides the limitation,
REM Larry can read and write /tmp/password.
call dbms_java.grant_permission('LARRY', 'java.io.FilePermission',
'/tmp/password', 'read,write');
commit;
The preceding code performs the following actions:
1.
Grants everyone read and write permission to all files in /tmp.
2.
Limits everyone from reading or writing only the password file in /tmp.
Security for Oracle Database Java Applications 10-7
Database Contents and Oracle JVM Security
3.
Grants only Larry explicit permission to read and write the password file.
Acquiring Administrative Permission to Update Policy Table
All permissions are rows in PolicyTable. Because it is a table in the database, you
need appropriate permissions to modify it. Specifically, the
PolicyTablePermission object is required to modify the table. After initializing
Oracle JVM, only a single role, JAVA_ADMIN, is granted PolicyTablePermission
to modify PolicyTable. The JAVA_ADMIN role is immediately assigned to the
database administrator (DBA). Therefore, if you are assigned to the DBA group, then
you will automatically take on all JAVA_ADMIN permissions.
If you need to add permissions as rows to this table, JAVA_ADMIN must grant your
schema update rights using PolicyTablePermission. This permission defines that
your schema can add rows to the table. Each PolicyTablePermission is for a
specific type of permission. For example, to add a permission that controls access to a
file, you must have PolicyTablePermission that lets you grant or limit a
permission on FilePermission. Once this occurs, you have administrative
permission for FilePermission.
An administrator can grant and limit PolicyTablePermission in the same manner
as other permissions, but the syntax is complicated. For ease of use, you can use the
grant_policy_permission() or grantPolicyPermission() method to grant
administrative permissions.
You can grant policy table administrative permission using DBMS_JAVA, as follows:
procedure grant_policy_permission ( grantee varchar2, permission_schema varchar2,
permission_type varchar2, permission_name varchar2 )
procedure grant_policy_permission ( grantee varchar2, permission_schema varchar2,
permission_type varchar2, permission_name varchar2, key OUT number )
You can grant policy table administrative permission using Java, as follows:
long oracle.aurora.rdbms.security.PolicyTableManager.grantPolicyPermission (
java.lang.String grantee, java.lang.String permission_type, java.lang.String
permission_name);
void oracle.aurora.rdbms.security.PolicyTableManager.grantPolicyPermission (
java.lang.String grantee, java.lang.String permission_type, java.lang.String
permission_name, long[] key);
Parameter
Description
Grantee
The name of the user, schema, or role to which you want the grant to
apply. PUBLIC specifies that the row applies to all users.
Permission_schema The schema where the Permission class is loaded.
Permission_type
The Permission class on which you are granting permission. For
example, if you were defining access to a file, the permission type would
be FilePermission. This parameter requires a fully-qualified name of
a class that extends java.lang.security.Permission. If the class
is not within SYS, the name should be prefixed by schema:. For
example, mySchema:myPackage.MyPermission is a valid name for a
user-generated permission.
Permission_name
The meaning of the target attribute as defined by the Permission
class. Examine the appropriate Permission class for the relevant name.
10-8 Oracle Database Java Developer’s Guide
Database Contents and Oracle JVM Security
Parameter
Description
Row_ number
Number returned from grant or limitation to use on enable, disable, or
delete methods.
When looking at the policy table, the name in the
PolicyTablePermission rows contains both the permission type
and the permission name, which are separated by a #. For example, to
grant a user administrative rights for reading a file, the name in the
row contains java.io.FilePermission#read. The # separates the
Permission class from the permission name.
Note:
Example 10–3 shows how you can modify PolicyTable.
Example 10–3
Granting PolicyTable Permission
This example shows SYS, which has the JAVA_ADMIN role assigned, giving Larry
permission to update PolicyTable for FilePermission. Once this permission is
granted, Larry can grant permissions to other users for reading, writing, and deleting
files.
REM Connect as SYS, which is assigned JAVA_ADMIN role, to give Larry permission
REM to modify the PolicyTable
connect SYS as SYSDBA
Enter password: password
REM SYS grants Larry the right to administer permissions for
REM FilePermission
call dbms_java.grant_policy_permission('LARRY', 'SYS', 'java.io.FilePermission',
'*');
Creating Permissions
You can create your own permission type by performing the following steps:
1.
Create and load the user permission
Create your own permission by extending the java.security.Permission
class. Any user-defined permission must extend Permission. The following
example creates MyPermission, which extends BasicPermission, which, in
turn, extends Permission.
package test.larry;
import java.security.Permission;
import java.security.BasicPermission;
public class MyPermission extends BasicPermission
{
public MyPermission(String name)
{
super(name);
}
public boolean implies(Permission p)
{
boolean result = super.implies(p);
return result;
Security for Oracle Database Java Applications 10-9
Database Contents and Oracle JVM Security
}
}
2.
Grant administrative and action permissions to specified users
When you create a permission, you are designated as the owner of that
permission. The owner is implicitly granted administrative permission. This
means that the owner can be an administrator for this permission and can run
grant_policy_permission(). Administrative permission enable the user to
update the policy table for the user-defined permission.
For example, if LARRY creates a permission, MyPermission, then only he can call
grant_policy_permission() for himself or another user. This method
updates PolicyTable on who can grant rights to MyPermission. The following
code demonstrates this:
REM Since Larry is the user that owns MyPermission, Larry connects to
REW the database to assign permissions for MyPermission.
connect larry
Enter password: password
REM As the owner of MyPermission, Larry grants himself the right to
REM administer permissions for test.larry.MyPermission within the JVM
REM security PolicyTable. Only the owner of the user-defined permission
REM can grant administrative rights.
call dbms_java.grant_policy_permission ('LARRY', 'LARRY',
'test.larry.MyPermission', '*');
REM commit the changes to PolicyTable
commit;
Once you have granted administrative rights, you can grant action permissions for
the created permission. For example, the following SQL statements grant LARRY
the permission to run anything within MyPermission and DAVE the permission
to run only actions that start with "act.".
REM Since Larry is the user that creates MyPermission, Larry connects to
REW the database to assign permissions for MyPermission.
connect larry
Enter password: password
REM Once able to modify PolicyTable for MyPermission, Larry grants himself
REM full permission for MyPermission. Notice that the Permission is prefixed
REM with its owner schema.
call dbms_java.grant_permission( 'LARRY', 'LARRY:test.larry.MyPermission', '*',
null);
REM Larry grants Dave permission to do any actions that start with 'act.*'.
call dbms_java.grant_permission
('DAVE', 'LARRY:test.larry.MyPermission', 'act.*', null);
REM commit the changes to PolicyTable
commit;
3.
Implement security checks using the permission
Once you have created, loaded, and assigned permissions for MyPermission,
you must implement the call to SecurityManager to have the permission
checked. There are four methods in the following example: sensitive(), act(),
print(), and hello(). Because of the permissions granted using SQL in the
preceding steps, the following users can run methods within the example class:
10-10 Oracle Database Java Developer’s Guide
Database Contents and Oracle JVM Security
■
LARRY can run any of the methods.
■
DAVE is given permission to run only the act() method.
■
Anyone can run the print() and hello() methods. The print() method
does not check any permissions. As a result, anyone can run it. The hello()
method runs AccessController.doPrivileged(), which means that the
method runs with the permissions assigned to LARRY. This is referred to as the
definer's rights.
package test.larry;
import java.security.AccessController;
import java.security.Permission;
import java.security.PrivilegedAction;
import java.sql.Connection;
import java.sql.SQLException;
/**
* MyActions is a class with a variety of public methods that
* have some security risks associated with them. We will rely
* on the Java security mechanisms to ensure that they are
* performed only by code that is authorized to do so.
*/
public class Larry {
private static String secret = "Larry's secret";
MyPermission sensitivePermission = new MyPermission("sensitive");
/**
* This is a security sensitive operation. That is it can
* compromise our security if it is executed by a "bad guy".
* Only larry has permission to execute sensitive.
*/
public void sensitive()
{
checkPermission(sensitivePermission);
print();
}
/**
* Will display a message from Larry. We need to be
* careful about who is allowed to do this
* because messages from Larry may have extra impact.
* Both larry and dave have permission to execute act.
*/
public void act(String message)
{
MyPermission p = new MyPermission("act." + message);
checkPermission(p);
System.out.println("Larry says: " + message);
}
/**
* display secret key
* No permission check is made; anyone can execute print.
*/
private void print()
{
System.out.println(secret);
Security for Oracle Database Java Applications 10-11
Database Contents and Oracle JVM Security
}
/**
* Display "Hello"
* This method invokes doPrivileged, which makes the method run
* under definer's rights. So, this method runs under Larry's
* rights, so anyone can execute hello. Only Larry can execute hello
*/
public void hello()
{
AccessController.doPrivileged(new PrivilegedAction() {
public Object run() { act("hello"); return null; }
});
}
/**
* If a security manager is installed ask it to check permission
* otherwise use the AccessController directly
*/
void checkPermission(Permission permission)
{
SecurityManager sm = System.getSecurityManager();
sm.checkPermission(permission);
}
}
Enabling or Disabling Permissions
Once you have created a row that defines a permission, you can disable it so that it no
longer applies. However, if you decide that you want the row action again, then you
can enable the row. You can delete the row from the table if you believe that it will
never be used again. To delete, you must first disable the row. If you do not disable the
row, then the deletion will not occur.
To disable rows, you can use either of the following methods:
■
revoke_permission()
This method accepts parameters similar to the grant() and restrict()
methods. It searches the entire policy table for all rows that match the parameters
provided.
■
disable_permission()
This method disables only a single row within the policy table. To do this, it
accepts the policy table key as parameter. This key is also necessary to enable or
delete a permission. To retrieve the permission key number, perform one of the
following:
–
Save the key when it is returned on the grant or limit calls. If you do not
foresee a need to ever enable or disable the permission, then you can use the
grant and limit calls that do not return the permission number.
–
Look up DBA_JAVA_POLICY or USER_JAVA_POLICY for the appropriate
permission key number.
You can disable permissions using DBMS_JAVA, as follows:
procedure revoke_permission (permission_schema varchar2, permission_type varchar2,
permission_name varchar2, permission_action varchar2)
procedure disable_permission (key number)
10-12 Oracle Database Java Developer’s Guide
Database Contents and Oracle JVM Security
You can disable permissions using Java, as follows:
void revoke (String schema, String type, String name, String action);
void oracle.aurora.rdbms.security.PolicyTableManager.disable (long number);
You can enable permissions using DBMS_JAVA, as follows:
procedure enable_permission (key number)
You can enable permissions using Java, as follows:
void oracle.aurora.rdbms.security.PolicyTableManager.enable (long number);
You can delete permissions using DBMS_JAVA, as follows:
procedure delete_permission (key number)
You can delete permissions using Java, as follows:
void oracle.aurora.rdbms.security.PolicyTableManager.delete (long number);
Permission Types
Whenever you want to grant or limit a permission, you must provide the permission
type. The permission types with which you control access are the following:
■
Java2 permission types
■
Oracle-specific permission types
■
User-defined permission types that extend java.security.Permission
Table 10–1 lists the installed permission types.
Table 10–1
Predefined Permissions
Type
Permissions
Java2
■
java.util.PropertyPermission
■
java.io.SerializablePermission
■
java.io.FilePermission
■
java.net.NetPermission
■
java.net.SocketPermission
■
java.lang.RuntimePermission
■
java.lang.reflect.ReflectPermission
■
java.security.SecurityPermission
■
oracle.aurora.rdbms.security.PolicyTablePermission
■
oracle.aurora.security.JServerPermission
Oracle specific
Note: SYS is granted permission to load libraries that come with
Oracle Database. However, Oracle JVM does not support other users
loading libraries, because loading C libraries within the database is
insecure. As a result, you are not allowed to grant
RuntimePermission for loadLibrary.*.
Security for Oracle Database Java Applications 10-13
Database Contents and Oracle JVM Security
The Oracle-specific permissions are:
■
oracle.aurora.rdbms.security.PolicyTablePermission
This permission controls who can update the policy table. Once granted the right
to update the policy table for a certain permission type, you can control the access
to few resources.
After the initialization of Oracle JVM, only the JAVA_ADMIN role can grant
administrative rights for the policy table through PolicyTablePermission.
Once it grants this right to other users, these users can, in turn, update the policy
table with their own grant and limitation permissions.
To grant policy table updates, you can use the grant_policy_permission()
method, which is in the DBMS_JAVA package. Once you have updated the table,
you can view either the DBA_JAVA_POLICY or USER_JAVA_POLICY view to see
who has been granted permissions.
■
oracle.aurora.security.JServerPermission
This permission is used to grant and limit access to Oracle JVM resources. The
JServerPermission extends BasicPermission. The following table lists the
permission names for which JServerPermission grants access:
Permission Name
Description
LoadClassInPackage.package_name Grants the ability to load a class within the
specified package
Verifier
Grants the ability to turn the bytecode verifier on
or off
Debug
Grants the ability for debuggers to connect to a
session
JRIExtensions
Grants the use of MEMSTAT
Memory.Call
Grants rights to call certain methods in
oracle.aurora.vm.OracleRuntime on call
settings
Memory.Stack
Grants rights to call certain methods in
oracle.aurora.vm.OracleRuntime on stack
settings
Memory.SGAIntern
Grants rights to call certain methods in
oracle.aurora.vm.OracleRuntime on SGA
settings
Memory.GC
Grants rights to call certain methods in
oracle.aurora.vm.OracleRuntime on
garbage collector settings
Initial Permission Grants
When you first initialize Oracle JVM, several roles are populated with certain
permission grants. The following tables show these roles and their initial Permissions:
■
Table 10–2, " SYS Initial Permissions"
■
Table 10–3, " PUBLIC Default Permissions"
■
Table 10–4, " JAVAUSERPRIV Permissions"
■
Table 10–5, " JAVASYSPRIV Permissions"
■
Table 10–6, " JAVADEBUGPRIV Permissions"
10-14 Oracle Database Java Developer’s Guide
Database Contents and Oracle JVM Security
The JAVA_ADMIN role is given access to modify the policy table for all permissions.
All DBAs, including SYS, are granted JAVA_ADMIN. Full administrative rights to
update the policy table are granted for the permissions listed in Table 10–1. In addition
to the JAVA_ADMIN permissions, SYS is granted some additional permissions.
Table 10–2 lists the additional permissions granted to SYS.
Table 10–2
SYS Initial Permissions
Permission Type
Permission Name
Action
oracle.aurora.rdbms.security.
PolicyTablePermission
*
Administrative rights to
modify the policy table
oracle.aurora.security.JServerPermission *
null
java.net.NetPermission
*
null
java.security.SecurityPermission
*
null
java.util.PropertyPermission
*
write
java.lang.reflect.ReflectPermission
*
null
java.lang.RuntimePermission
*
null
loadLibrary.xaNative
null
loadLibrary.corejava
null
loadLibrary.corejava_d
null
Table 10–3 lists permissions initially granted to all users.
Table 10–3
PUBLIC Default Permissions
Permission Type
Permission Name
Action
oracle.aurora.rdbms.security. java.lang.RuntimePermission.loadLibrary.*
PolicyTablePermission
null
java.util.PropertyPermission
*
read
user.language
write
_
null
exitVM
null
createSecurityManager
null
modifyThread
null
modifyThreadGroup
null
loadClassInPackage.* except for
loadClassInPackage.java.*,
loadClassInPackage.oracle.aurora.*, and
loadClassInPackage.jdbc.*
null
java.lang.RuntimePermission
oracle.aurora.security.
JServerPermission
Table 10–4 lists permissions initially granted to the JAVAUSERPRIV role.
Security for Oracle Database Java Applications 10-15
Database Contents and Oracle JVM Security
Table 10–4
JAVAUSERPRIV Permissions
Permission Type
Permission Name
Action
java.net.SocketPermission
*
connect,
resolve
java.io.FilePermission
<<ALL FILES>>
read
java.lang.RuntimePermission modifyThreadGroup, stopThread, getProtectionDomain, null
readFileDescriptor, accessClassInPackage.*, and
defineClassInPackage.*
Table 10–5 lists permissions initially granted to the JAVASYSPRIV role.
Table 10–5
JAVASYSPRIV Permissions
Permission Type
Permission Name
Action
java.io.SerializablePermission *
no applicable action
java.io.FilePermission
<<ALL FILES>>
read, write, execute, delete
java.net.SocketPermission
*
accept, connect, listen, resolve
java.lang.RuntimePermission
createClassLoader
null
getClassLoader
null
setContextClassLoader
null
setFactory
null
setIO
null
setFileDescriptor
null
readFileDescriptor
null
writeFileDescriptor
null
Table 10–6 lists permissions initially granted to the JAVADEBUGPRIV role.
Table 10–6
JAVADEBUGPRIV Permissions
Permission Type
Permission Name
Action
oracle.aurora.security.JServerPermission
Debug
null
java.net.SocketPermission
*
connect, resolve
General Permission Definition Assigned to Roles
In Oracle8i Database release 8.1.5, Oracle JVM security was controlled by granting the
JAVASYSPRIV, JAVAUSERPRIV, or JAVADEBUGPRIV role to schemas. In Oracle
Database 10g, these roles still exist as permission groups. You can set up and define
your own collection of permissions. Once defined, you can grant any collection of
permissions to any user or role. That user will then have the same permissions that
exist within the role. In addition, if you need additional permissions, then you can add
individual permissions to either your specified user or role. Permissions defined
within the policy table have a cumulative effect.
10-16 Oracle Database Java Developer’s Guide
Database Contents and Oracle JVM Security
The ability to write to properties, granted through the write
action on PropertyPermission, is no longer granted to all users.
Instead, you must have either JAVA_ADMIN grant this permission to
you or you can receive it by being granted the JAVASYSPRIV role.
Note:
The following example gives Larry and Dave the following permissions:
■
■
Larry receives JAVASYSPRIV permissions.
Dave receives JAVADEBUGPRIV permissions and the ability to read and write all
files on the system.
REM Granting Larry the same permissions as those existing within JAVASYSPRIV
grant javasyspriv to larry;
REM Granting Dave the ability to debug
grant javadebugpriv to dave;
commit;
REM I also want Dave to be able to read and write all files on the system
call dbms_java.grant_permission('DAVE', 'SYS:java.io.FilePermission',
'<<ALL FILES>>', 'read,write', null);
See Also:
"Fine-Grain Definition for Each Permission" on page 10-5.
Debugging Permissions
A debug role, JAVADEBUGPRIV, was created to grant permissions for running the
debugger. The permissions assigned to this role are listed in Table 10–6. To receive
permission to call the debug agent, the caller must have been granted
JAVADEBUGPRIV or the debug JServerPermission as follows:
REM Granting Dave the ability to debug
grant javadebugpriv to dave;
REM Larry grants himself permission to start the debug agent.
call dbms_java.grant_permission(
'LARRY', 'oracle.aurora.security.JServerPermission', 'Debug', null);
Although a debugger provides extensive access to both code and data on the server, its
use should be limited to development environments.
See Also:
"Debugging Server Applications" on page 3-13
Permission for Loading Classes
To load classes, you must have the following permission:
JServerPermission("LoadClassInPackage." + class_name)
where, class_name is the fully qualified name of the class that you are loading.
This excludes loading into system packages or replacing any system classes. Even if
you are granted permission to load a system class, Oracle Database prevents you from
performing the load. System classes are classes that are installed by Oracle Database
using the CREATE JAVA SYSTEM statement. The following error is thrown if you try
to replace a system class:
Security for Oracle Database Java Applications 10-17
Database Authentication Mechanisms
ORA-01031 "Insufficient privileges"
The following describes what each user can do after database installation:
■
■
SYS can load any class except for system classes.
Any user can load classes in its own schema that do not start with the following
patterns: java.*, oracle.aurora.*, and oracle.jdbc.*. If the user wants to
load such classes into another schema, then it must be granted the
JServerPermission(LoadClassInPackage.class) permission.
The following example shows how to grant SCOTT permission to load classes into
the oracle.aurora.* package:
dbms_java.grant_permission('SCOTT', 'SYS:oracle.aurora.tools.*', null)
Database Authentication Mechanisms
The following database authentication mechanisms are available:
■
Password authentication
■
Strong authentication
■
Proxy authentication
■
Single sign-on
10-18 Oracle Database Java Developer’s Guide
11
Schema Objects and Oracle JVM Utilities
This chapter describes the schema objects that you use in Oracle Database Java
environment and Oracle JVM utilities. You run these utilities from a UNIX shell or
from the Microsoft Windows DOS prompt.
All names supplied to these tools are case-sensitive. As a
result, the schema, user name, and password should not be changed
to uppercase.
Note:
This chapter contains the following sections:
■
Overview of Schema Objects
■
What and When to Load
■
Resolution of Schema Objects
■
Compilation of Schema Objects
■
The ojvmtc Tool
■
The loadjava Tool
■
The dropjava Tool
■
The ojvmjava Tool
Overview of Schema Objects
Unlike conventional Java virtual machine (JVM), which compiles and loads Java files,
Oracle JVM compiles and loads schema objects. The following kinds of Java schema
objects are loaded:
■
Java class schema objects, which correspond to Java class files.
■
Java source schema objects, which correspond to Java source files.
■
Java resource schema objects, which correspond to Java resource files.
To ensure that a class file can be run by Oracle JVM, you must use the loadjava tool
to create a Java class schema object from the class file or the source file and load it into
a schema. To make a resource file accessible to Oracle JVM, you must use loadjava
to create and load a Java resource schema object from the resource file.
The dropjava tool deletes schema objects that correspond to Java files. You should
always use dropjava to delete a Java schema object that was created with loadjava.
Dropping schema objects using SQL data definition language (DDL) commands will
not update auxiliary data maintained by loadjava and dropjava.
Schema Objects and Oracle JVM Utilities 11-1
What and When to Load
What and When to Load
You must load resource files using loadjava. If you create .class files outside the
database with a conventional compiler, then you must load them with loadjava. The
alternative to loading class files is to load source files and let Oracle Database compile
and manage the resulting class schema objects. In Oracle Database 10g, the most
productive approach is to compile and debug most of your code outside the database,
and then load the .class files. For a particular Java class, you can load either its
.class file or the corresponding .java file, but not both.
The loadjava tool accepts Java Archive (JAR) files that contain either source and
resource files or class and resource files. When you pass a JAR or ZIP file to
loadjava, it opens the archive and loads its members individually. There are no JAR
or ZIP schema objects.
When you load the contents of a JAR into the database, you
have the option of creating a database object representing the JAR
itself. For more information, refer to "Database Resident JARs" on
page 2-15.
Note:
A file, whose content has not changed since the last time it was loaded, is not reloaded.
As a result, there is little performance penalty for loading JAR files. Loading JAR files
is a simple, fool-proof way to use loadjava.
It is illegal for two schema objects in the same schema to define the same class. For
example, assume that a.java defines class x and you want to move the definition of
x to b.java. If a.java has already been loaded, then loadjava will reject an
attempt to load b.java. Instead, do either of the following:
■
■
Drop a.java, load b.java, and then load the new a.java, which does not
define x.
Load the new a.java, which does not define x, and then load b.java.
Resolution of Schema Objects
All Java classes contain references to other classes. A conventional JVM searches for
classes in the directories, ZIP files, and JAR files named in the CLASSPATH. In contrast,
Oracle JVM searches schemas for class schema objects. Each class in the database has a
resolver specification, which is Oracle Database counterpart to CLASSPATH. For
example, the resolver specification of a class, alpha, lists the schemas to search for
classes that alpha uses. Notice that resolver specifications are per-class, whereas in a
classic JVM, CLASSPATH is global to all classes.
In addition to a resolver specification, each class schema object has a list of interclass
reference bindings. Each reference list item contains a reference to another class and
one of the following:
■
■
The name of the class schema object to call when the class uses the reference
A code indicating whether the reference is unsatisfied, that is, whether the referent
schema object is known
Oracle Database facility known as resolver maintains reference lists. For each
interclass reference in a class, the resolver searches the schemas specified by the
resolver specification of the class for a valid class schema object that satisfies the
reference. If all references are resolved, then the resolver marks the class valid. A class
that has never been resolved, or has been resolved unsuccessfully, is marked invalid. A
11-2 Oracle Database Java Developer’s Guide
Resolution of Schema Objects
class that depends on a schema object that becomes invalid is also marked invalid at
the time the first class is marked invalid. In other words, invalidation cascades upward
from a class to the classes that use it and the classes that use these classes, and so on.
When resolving a class that depends on an invalid class, the resolver first tries to
resolve the referenced class, because it may be marked invalid only because it has
never been resolved. The resolver does not resolve classes that are marked valid.
A developer can direct loadjava to resolve classes or can defer resolution until run
time. The resolver runs automatically when a class tries to load a class that is marked
invalid. It is best to resolve before run time to learn of missing classes early.
Unsuccessful resolution at run time produces a ClassNotFound exception.
Furthermore, run-time resolution can fail for the following reasons:
■
Lack of database resources, if the tree of classes is very large
■
Deadlocks due to circular dependencies
The loadjava tool has two resolution modes:
■
Load-and-resolve
The -resolve option loads all classes you specify on the command line, marks
them invalid, and then resolves them. Use this mode when initially loading classes
that refer to each other, and, in general, when reloading isolated classes as well. By
loading all classes and then resolving them, this mode avoids the error message
that occurs if a class refers to a class that will be loaded later while the command is
being carried out.
■
Load-then-resolve
This mode resolves each class at run time. The -resolve option is not specified.
As with a Java compiler, loadjava resolves references to
classes but not to resources. Ensure that you correctly load the
resource files that your classes need.
Note:
If you can, defer resolution until all classes have been loaded. This avoids a situation
in which the resolver marks a class invalid because a class it uses has not yet been
loaded.
Schema Object Digest Table
The schema object digest table is an optimization that is usually invisible to
developers. The digest table enables loadjava to skip files that have not changed
since they were last loaded. This feature improves the performance of makefiles and
scripts that call loadjava for collections of files, some of which need to be reloaded.
A reloaded archive file might also contain some files that have changed since they
were last loaded and some that have not.
The loadjava tool detects unchanged files by maintaining a digest table in each
schema. The digest table relates a file name to a digest, which is a shorthand
representation or a hash, of the content of the file. Comparing digests computed for
the same file at different times is a fast way to detect a change in the content of the file.
This is much faster than comparing every byte in the file. For each file it processes,
loadjava computes a digest of the content of the file and then looks up the file name
in the digest table. If the digest table contains an entry for the file name that has an
identical digest, then loadjava does not load the file, because a corresponding
Schema Objects and Oracle JVM Utilities 11-3
Compilation of Schema Objects
schema object exists and is up to date. If you call loadjava with the -verbose
option, then it will show you the results of its digest table lookups.
Normally, the digest table is invisible to developers, because loadjava and
dropjava keep the table synchronized with schema object additions, changes, and
deletions. For this reason, always use dropjava to delete a schema object that was
created with loadjava, even if you know how to drop a schema object using DDL..
Compilation of Schema Objects
Loading a source file creates or updates a Java source schema object and invalidates
the class schema objects previously derived from the source. If the class schema objects
do not exist, then loadjava creates them. The loadjava tool invalidates the old
class schema objects because they were not compiled from the newly loaded source.
Compilation of a newly loaded source, for example, class A, is automatically triggered
by any of the following conditions:
■
■
■
The resolver, while working on class B, finds that class B refers to class A, but class
A is invalid.
The compiler, while compiling the source of class B, finds that class B refers to
class A, but class A is invalid.
The class loader, while trying to load class A for running it, finds that class A is
invalid.
To force compilation when you load a source file, use loadjava -resolve.
The compiler writes error messages to the predefined USER_ERRORS view. The
loadjava tool retrieves and displays the messages produced by its compiler
invocations.
The compiler recognizes some options. There are two ways to specify options to the
compiler. If you run loadjava with the -resolve option, then you can specify
compiler options on the command line. You can additionally specify persistent
compiler options in a per-schema database table, JAVA$OPTIONS. You can use the
JAVA$OPTIONS table for default compiler options, which you can override selectively
using a loadjava command-line option.
A command-line option overrides and clears the matching
entry in the JAVA$OPTIONS table.
Note:
A JAVA$OPTIONS row contains the names of source schema objects to which an
option setting applies. You can use multiple rows to set the options differently for
different source schema objects. The compiler looks up options in JAVA$OPTIONS
when it has been called by the class loader or when called from the command line
without specifying any options. When compiling a source schema object for which
there is neither a JAVA$OPTIONS entry nor a command-line value for an option, the
compiler assumes a default value, as follows:
■
encoding = System.getProperty("file.encoding");
■
online = true
This applies only to Java sources that contain SQLJ constructs.
■
debug = true
This option is equivalent to javac -g.
11-4 Oracle Database Java Developer’s Guide
The ojvmtc Tool
See Also:
"Compiler Options Specified in a Database Table" on
page 2-7
The ojvmtc Tool
The ojvmtc tool enables you to resolve all external references, prior to running
loadjava. ojvmtc allows the specification of a classpath that specifies the JARs,
classes, or directories to be used to resolve class references. When an external reference
cannot be resolved, this tool either produces a list of unresolved references or
generated stub classes to allow resolution of the references, depending on the options
specified. Generated stub classes throw a java.lang.ClassNotfoundException,
if it is referenced at runtime.
The syntax is:
ojvmtc [-help ] [-bootclasspath] [-server connect_string] [-jar jar_name] [-list]
-classpath jar1:path2:jar2 jars,...,classes
For example:
ojvmtc -bootclasspath $JAVA_HOME/jre/lib/rt.jar -classpath
classdir/lib1.jar:classdir/lib2.jar -jar set.jar app.jar
The preceding example uses rt.jar, classdir/lib1.jar, and
classdir/lib2.jar to resolve references in app.jar. All the classes examined
are added to set.jar, except for those found in rt.jar.
Another example is:
ojvmtc -server thin@scott:localhost:5521:orcl -classpath jar1:jar2 -list app2.jar
Password:password
The preceding example uses classes found in the server specified by the connect string
as well as jar1 and jar2 to resolve app2.jar. Any missing references are
displayed to stdout.
Table 11–1 summarizes the arguments of this command.
Table 11–1
ojvmtc Argument Summary
Argument
Description
-classpath
Uses the specified JARs and classes for the closure set.
-bootclasspath
Uses the specified classes for closure, but does not include them
in the closure set.
-server
connect_string
Connects to the server using visible classes in the same manner
as -bootclasspath.
connect_string
thin|OCI
Connects to the server using thin or Oracle Call Interface (OCI)
specific driver.
If you use thin driver, the syntax is as follows:
thin:user/passwd@host:port:sid
If you use OCI driver, the syntax is as follows:
oci:user/passwd@host:port:sid
oci:user/passwd@tnsname
oci:user/passwd@(connect descriptor)
Schema Objects and Oracle JVM Utilities 11-5
The loadjava Tool
Table 11–1 (Cont.) ojvmtc Argument Summary
Argument
Description
-jar jar_name
Writes each class of the closure set to a JAR and generates stubs
for missing classes
-list
Lists the missing classes.
The loadjava Tool
The loadjava tool creates schema objects from files and loads them into a schema.
Schema objects can be created from Java source, class, and data files. loadjava can
also create schema objects from SQLJ files.
You must have the following SQL database privileges to load classes:
■
■
■
CREATE PROCEDURE and CREATE TABLE privileges to load into your schema.
CREATE ANY PROCEDURE and CREATE ANY TABLE privileges to load into
another schema.
oracle.aurora.security.JServerPermission.loadLibraryInClass.cla
ssname.
You can run the loadjava tool either from the command line or by using the
loadjava method contained in the DBMS_JAVA class. To run the tool from within
your Java application, do the following:
call dbms_java.loadjava('... options...');
The options are the same as those that can be specified on the command line with the
loadjava tool. Separate each option with a space. Do not separate the options with a
comma. The only exception for this is the -resolver option, which contains spaces.
For -resolver, specify all other options in the first input parameter and the
-resolver options in the second parameter, as follows:
call dbms_java.loadjava('..options...', 'resolver_options');
Do not specify the -thin, -oci, -user, and -password options, because they relate
to the database connection for the loadjava command-line tool. The output is
directed to stderr. Set serveroutput on, and call dbms_java.set_output, as
appropriate.
The loadjava tool is located in the bin directory under
$ORACLE_HOME.
Note:
Just before the loadjava tool exits, it checks whether the processing was successful.
All failures are summarized preceded by the following header:
The following operations failed
Some conditions, such as losing the connection to the database, cause loadjava to
terminate prematurely. These errors are displayed with the following syntax:
exiting: error_reason
This section covers the following:
■
Syntax
■
Argument Summary
11-6 Oracle Database Java Developer’s Guide
The loadjava Tool
■
Argument Details
Syntax
The syntax of the loadjava command is as follows:
loadjava {-user | -u} user/[password][@database] [options]
file.java | file.class | file.jar | file.zip |
file.sqlj | resourcefile | URL...
[-casesensitivepub]
[-cleargrants]
[-debug]
[-d | -definer]
[-dirprefix prefix]
[-e | -encoding encoding_scheme]
[-fileout file]
[-f | -force]
[-genmissing]
[-genmissingjar jar_file]
[-g | -grant user [, user]...]
[-help]
[-jarasresource]
[-noaction]
[-norecursivejars]
[-nosynonym]
[-nousage]
[-noverify]
[-o | -oci | oci8]
[-optiontable table_name]
[-publish package]
[-pubmain number]
[-recursivejars]
[-r | -resolve]
[-R | -resolver "resolver_spec"]
[-resolveonly]
[-S | -schema schema]
[-stdout]
[-stoponerror]
[-s | -synonym]
[-tableschema schema]
[-t | -thin]
[-unresolvedok]
[-v | -verbose]
[-jarsasdbobjects]
[-prependjarnames]
[-nativecompile]
Argument Summary
Table 11–2 summarizes the loadjava arguments. If you run loadjava multiple
times specifying the same files and different options, then the options specified in the
most recent invocation hold. However, there are two exceptions to this, as follows:
■
If loadjava does not load a file because it matches a digest table entry, then most
options on the command line have no effect on the schema object. The exceptions
are -grant and -resolve, which always take effect. You must use the -force
option to direct loadjava to skip the digest table lookup.
Schema Objects and Oracle JVM Utilities 11-7
The loadjava Tool
■
The -grant option is cumulative. Every user specified in every loadjava
invocation for a given class in a given schema has the EXECUTE privilege.
Table 11–2
loadjava Argument Summary
Argument
Description
filenames
You can specify any number and combination of .java, .class,
.sqlj, .ser, .jar, .zip, and resource file name arguments.
-proxy host:port
If you do not have physical access to the server host or the
loadjava client for loading classes, resources, and Java source,
then you can use an HTTP URL with loadjava to specify the JAR,
class file, or resource and load the class from a remote server. host
is the host name or address and port is the port the proxy server is
using. The URL implementation must be such that loadjava can
determine the type of file to load, that is, JAR, class, resource, or
Java source. For example:
loadjava –u scott –r –v –proxy proxy_server:1020
http://my.server.com/this/is /the/path/my.jar
Password: password
When the URL support is used inside the server, you should have
proper Java permissions to access to the remote source. The URL
support also includes ftp: and file: URLs.
-casesensitivepub
Publishing will create case-sensitive names. Unless the names are
already all uppercase, it will usually require quoting the names in
PL/SQL.
-cleargrants
The -grant option causes loadjava to grant EXECUTE privileges
to classes, sources, and resources. However, it does not cause it to
revoke any privileges. If -cleargrants is specified, then
loadjava will revoke any existing grants of execute privilege
before it grants execute privilege to the users and roles specified by
the -grant operand. For example, if the intent is to have execute
privilege granted to only SCOTT, then the proper options are:
-grant SCOTT -cleargrants
-debug
Turns on SQL logging.
-definer
By default, class schema objects run with the privileges of their
invoker. This option confers definer privileges upon classes instead.
This option is conceptually similar to the UNIX setuid facility.
-dirprefix prefix
For any files or JAR entries that start with prefix, this prefix will
be deleted from the name before the name of the schema object is
determined. For classes and sources, the name of the schema object
is determined by their contents. Therefore, this option will only
have an effect for resources.
-encoding
Identifies the source file encoding for the compiler, overriding the
matching value, if any, in JAVA$OPTIONS. Values are the same as
for the javac -encoding option. If you do not specify an
encoding on the command line or in JAVA$OPTIONS, then the
encoding is assumed to be the value returned by:
System.getProperty("file.encoding");
This option is relevant only when loading a source file.
-fileout file
Displays all message to the designated file.
-force
Forces files to be loaded, even if they match digest table entries.
11-8 Oracle Database Java Developer’s Guide
The loadjava Tool
Table 11–2 (Cont.) loadjava Argument Summary
Argument
Description
-genmissing
Determines what classes and methods are referred to by the classes
that loadjava is asked to process. Any classes not found in the
database or file arguments are called missing classes. This option
generates dummy definitions for missing classes containing all the
referred methods. It then loads the generated classes into the
database. This processing happens before the class resolution.
Because detecting references from source is more difficult than
detecting references from class files, and because source is not
generally used for distributing libraries, loadjava will not attempt
to do this processing for source files.
The schema in which the missing classes are loaded will be the one
specified by the -user option, even when referring classes are
created in some other schema. The created classes will be flagged so
that tools can recognize them. In particular, this is needed, so that
the verifier can recognize the generated classes.
-genmissingjar
jar_file
This option performs the same actions as -genmissing. In
addition, it creates a JAR file, jar_file, that contains the
definitions of any generated classes.
-grant
Grants the EXECUTE privilege on loaded classes to the listed users.
Any number and combination of user names can be specified,
separated by commas, but not spaces.
Granting the EXECUTE privilege on an object in another schema
requires that the original CREATE PROCEDURE privilege was
granted with the WITH GRANT options.
Note:
■
■
-grant is a cumulative option. Users are added to the list of
those with the EXECUTE privilege. To remove privileges, use
the -cleargrants option.
The schema name should be used in uppercase.
-help
Displays usage message on how to use loadjava and its options.
-jarasresource
Instead of unpacking the JAR file and loading each class within it,
loads the whole JAR file into the schema as a resource.
-noaction
Take no action on the files. Actions include creating the schema
objects, granting execute permissions, and so on. The normal use is
within an option file to suppress creation of specific classes in a JAR.
When used on the command line, unless overridden in the option
file, it will cause loadjava to ignore all files. Except that JAR files
will still be examined to determine if they contain a
META-INF/loadjava-options entry. If so, then the option file is
processed. The -action option in the option file will override the
-noaction option specified on the command line.
-norecursivejars
Treat JAR files contained in other JAR files as resources. This is the
default behavior. This option is used to override the
-recursivejars option.
-nosynonym
Do not create a public synonym for the classes. This is the default
behavior. This overrides the -synonym option.
-nousage
Suppresses the usage message that is given if either no option is
specified or if the -help option is specified.
-noverify
Causes the classes to be loaded without bytecode verification.
oracle.aurora.security.JServerPermission(Verifier)
must be granted to use this option. To be effective, this option
must be used in conjunction with -resolve.
Schema Objects and Oracle JVM Utilities 11-9
The loadjava Tool
Table 11–2 (Cont.) loadjava Argument Summary
Argument
Description
-oci | -oci8
Directs loadjava to communicate with the database using the
JDBC Oracle Call Interface (OCI) driver. -oci and -thin are
mutually exclusive. If neither is specified, then -oci is used by
default. Choosing -oci implies the syntax of the -user value. You
do not need to provide the URL.
-publish package
The package is created or replaced by loadjava. Wrappers for the
eligible methods will be defined in this package. Through the use of
option files, a single invocation of loadjava can be instructed to
create more than one package. Each package will undergo the same
name transformations as the methods.
-pubmain number
A special case applied to methods with a single argument, which is
of type java.lang.String. Multiple variants of the SQL
procedure or function will be created, each of which takes a
different number of arguments of type VARCHAR. In particular,
variants are created taking all arguments up to and including
number. The default value is 3. This option applies to main, as well
as any method that has exactly one argument of type
java.lang.String.
-recursivejars
Normally, if loadjava encounters an entry in a JAR with a .jar
extension, it will load the entry as a resource. If this option is
specified, then loadjava will process contained JAR files as if they
were top-level JAR files. That is, it will read their entries and load
classes, sources, and resources.
-resolve
Compiles, if necessary, and resolves external references in classes
after all classes on the command line have been loaded. If you do
not specify -resolve, loadjava loads files, but does not compile
or resolve them.
-resolver
Specifies an explicit resolver specification, which is bound to the
newly loaded classes. If -resolver is not specified, then the
default resolver specification, which includes current user's schema
and PUBLIC, is used.
-resolveonly
Causes loadjava to skip the initial creation step. It will still
perform grants, resolves, create synonyms, and so on.
-schema
Designates the schema where schema objects are created. If not
specified, then the -user schema is used. To create a schema object
in a schema that is not your own, you must have the CREATE
PROCEDURE or CREATE ANY PROCEDURE privilege. You must have
CREATE TABLE or CREATE ANY TABLE privilege. Finally, you
must have the JServerPermission loadLibraryInClass for
the class.
-stdout
Causes the output to be directed to stdout, rather than to stderr.
-stoponerror
Normally, if an error occurs while loadjava is processing files, it
will issue a message and continue to process other classes. This
option stops when an error occurs. In addition, it reports all errors
that apply to Java objects and are contained in the USER_ERROR
table of the schema in which classes are being loaded. Except that is
does not report ORA-29524 errors. These are errors that are
generated when a class cannot be resolved, because a referred class
could not be resolved. Therefore, these errors are a secondary effect
of whatever caused a referred class to be unresolved.
-synonym
Creates a PUBLIC synonym for loaded classes making them
accessible outside the schema into which they are loaded. To specify
this option, you must have the CREATE PUBLIC SYNONYM
privilege. If -synonym is specified for source files, then the classes
compiled from the source files are treated as if they had been loaded
with -synonym.
11-10 Oracle Database Java Developer’s Guide
The loadjava Tool
Table 11–2 (Cont.) loadjava Argument Summary
Argument
Description
-tableschema
schema
Creates the loadjava internal tables within the specified schema,
rather than in the Java file destination schema.
-thin
Directs loadjava to communicate with the database using the
JDBC Thin driver. Choosing -thin implies the syntax of the -user
value. You do need to specify the appropriate URL through the
-user option.
-unresolvedok
When combined with -resolve, will ignore unresolved errors.
-user
Specifies a user name, password, and database connect string. The
files will be loaded into this database instance.
-verbose
Directs loadjava to display detailed status messages while
running. Use -verbose to learn when loadjava does not load a
file, because it matches a digest table entry.
-jarsasdbobjects
Indicates that JARs processed by the current loadjava command
are to be stored in the database as database resident JARs.
-prependjarnames
Is used with the -jarsasdbobjects option. This option enables
classes with the same names coming from different JARs to coexist
in the same schema. It does this by prefixing a version of the name
of the JAR to the class name to produce a unique name for the
database object.
Argument Details
This section describes the details of some of the loadjava arguments whose behavior
is more complex than the summary descriptions contained in Table 11–2.
File Names
You can specify as many .class, .java, .sqlj, .jar, .zip, and resource files as
you want and in any order. If you specify a JAR or ZIP file, then loadjava processes
the files in the JAR or ZIP. There is no JAR or ZIP schema object. If a JAR or ZIP
contains another JAR or ZIP, loadjava does not process them.
The best way to load files is to put them in a JAR or ZIP and then load the archive.
Loading archives avoids the resource schema object naming complications. If you have
a JAR or ZIP that works with the Java Development Kit (JDK), then you can be sure
that loading it with loadjava will also work, without having to learn anything about
resource schema object naming.
Schema object names are different from file names, and loadjava names different
types of schema objects differently. Because class files are self-identifying, the mapping
of class file names to schema object names done by loadjava is invisible to
developers. Source file name mapping is also invisible to developers. loadjava gives
the schema object the fully qualified name of the first class defined in the file. JAR and
ZIP files also contain the names of their files.
However, resource files are not self identifying. loadjava generates Java resource
schema object names from the literal names you supply as arguments. Because classes
use resource schema objects and the correct specification of resources is not always
intuitive, it is important that you specify resource file names correctly on the command
line.
The perfect way to load individual resource files correctly is to run loadjava from
the top of the package tree and specify resource file names relative to that directory.
Schema Objects and Oracle JVM Utilities
11-11
The loadjava Tool
The top of the package tree is the directory you would name in
a CLASSPATH.
Note:
If you do not want to follow this rule, then observe the details of resource file naming
that follow. When you load a resource file, loadjava generates the resource schema
object name from the resource file name, as literally specified on the command line.
For example, if you type:
% cd /home/scott/javastuff
% loadjava options alpha/beta/x.properties
% loadjava options /home/scott/javastuff/alpha/beta/x.properties
Although you have specified the same file with a relative and an absolute path name,
loadjava creates two schema objects, alpha/beta/x.properties and
ROOT/home/scott/javastuff/alpha/beta/x.properties. The name of the
resource schema object is generated from the file name as entered.
Classes can refer to resource files relatively or absolutely. To ensure that loadjava
and the class loader use the same name for a schema object, enter the name on the
command line, which the class passes to getResource() or
getResourceAsString().
Instead of remembering whether classes use relative or absolute resource names and
changing directories so that you can enter the correct name on the command line, you
can load resource files in a JAR, as follows:
% cd /home/scott/javastuff
% jar -cf alpharesources.jar alpha/*.properties
% loadjava options alpharesources.jar
To simplify the process further, place both the class and resource files in a JAR, which
makes the following invocations equivalent:
% loadjava options alpha.jar
% loadjava options /home/scott/javastuff/alpha.jar
The preceding loadjava commands imply that you can use any path name to load
the contents of a JAR file. Even if you run the redundant commands, loadjava would
realize from the digest table that it need not load the files twice. This implies that
reloading JAR files is not as time-consuming as it might seem, even when few files
have changed between loadjava invocations.
definer
{-definer | -d}
This option is identical to the definer rights in stored procedures and is conceptually
similar to the UNIX setuid facility. However, you can apply the -definer option to
individual classes, in contrast to setuid, which applies to a complete program.
Moreover, different definers may have different privileges. Because an application can
consist of many classes, you must apply -definer with care to achieve the desired
results. That is, classes run with the privileges they need, but no more.
See Also:
"Controlling the Current User" on page 2-16
noverify
[-noverify]
11-12 Oracle Database Java Developer’s Guide
The loadjava Tool
This option causes the classes to be loaded without bytecode verification.
oracle.aurora.security.JServerPermission(Verifier) must be granted
to run this option. Also, this option must be used in conjunction with -resolve.
The verifier ensures that incorrectly formed Java binaries cannot be loaded for running
on the server. If you know that the JAR or classes you are loading are valid, then the
use of this option will speed up the loadjava process. Some Oracle Database-specific
optimizations for interpreted performance are put in place during the verification
process. Therefore, the interpreted performance of your application may be adversely
affected by using this option.
optionfile
[-optionfile <file>]
This option enables you to specify a file with loadjava options. This file is read and
processed by loadjava before any other loadjava options are processed. The file
can contain one or more lines, each of which contains a pattern and a sequence of
options. Each line must be terminated by a newline character (\n).
For each file or JAR entry that is processed by loadjava, the long name of the schema
object that is going to be created is checked against the patterns. Patterns can end in a
wildcard (*) to indicate an arbitrary sequence of characters, or they must match the
name exactly.
Options to be applied to matching Java schema objects are supplied on the rest of the
line. Options are appended to the command-line options, they do not replace them. In
case more than one line matches a name, the matching rows are sorted by length of
pattern, with the shortest first, and the options from each row are appended. In
general, loadjava options are not cumulative. Rather, later options override earlier
ones. This means that an option specified on a line with a longer pattern will override
a line with a shorter pattern.
This file is parsed by a java.io.StreamTokenizer.
You can use Java comments in this file. A line comment begins with a #. Empty lines
are ignored. The quote character is a double quote ("). That is, options containing
spaces should be surrounded by double quotes. Certain options, such as -user and
-verbose, affect the overall processing of loadjava and not the actions performed
for individual Java schema objects. Such options are ignored if they appear in an
option file.
To help package applications, loadjava looks for the
META-INF/loadjava-options entry in each JAR it processes. If it finds such an
entry, then it treats it as an options file that is applied for all other entries in the option
file. However, loadjava does some processing on entries in the order in which they
occur in the JAR.
If loadjava has partially processed entities before it processes
META-INF/loadjava-options, then it attempts to patch up the schema object to
conform to the applicable options. For example, loadjava alters classes that were
created with invoker rights when they should have been created with definer rights.
The fix for -noaction is to drop the created schema object. This yields the correct
effect, except that if a schema object existed before loadjava started, then it would
have been dropped.
publish
[-publish <package>]
[-pubmain <number>]
Schema Objects and Oracle JVM Utilities
11-13
The loadjava Tool
The publishing options cause loadjava to create PL/SQL wrappers for methods
contained in the processed classes. Typically, a user wants to publish wrappers for
only a few classes in a JAR. These options are most useful when specified in an option
file.
To be eligible for publication, the method must satisfy the following:
■
It must be a member of a public class.
■
It must be declared public and static.
■
The method signature should satisfy the following rules so that it can be mapped:
–
Java arithmetic types for arguments and return values are mapped to NUMBER.
–
char as an argument and return type is mapped to VARCHAR.
–
java.lang.String as an argument and return type is mapped to VARCHAR.
–
If the only argument of the method has type java.lang.String, special
rules apply, as listed in the -pubmain option description.
–
If the return type is void, then a procedure is created.
–
If the return type is an arithmetic, char, or java.lang.String type, then a
function is created.
Methods that take arguments or return types that are not covered by the preceding
rules are not eligible. No provision is made for OUT and IN OUT SQL arguments,
OBJECT types, and many other SQL features.
resolve
{-resolve | -r}
Use -resolve to force loadjava to compile and resolve a class that has previously
been loaded. It is not necessary to specify -force, because resolution is performed
after, and independent of, loading.
resolver
{-resolver | -R} resolver_specification
This option associates an explicit resolver specification with the class schema objects
that loadjava creates or replaces.
A resolver specification consists of one or more items, each of which consists of a name
specification and a schema specification expressed in the following syntax:
"((name_spec schema_spec) [(name_spec schema_spec)] ...)"
A name specification is similar to a name in an import statement. It can be a fully
qualified Java class name or a package name whose final element is the wildcard
character asterisk (*) or simply an asterisk (*). However, the elements of a name
specification must be separated by slashes (/), not periods (.). For example, the name
specification a/b/* matches all classes whose names begin with a.b. The special
name * matches all class names.
A schema specification can be a schema name or the wildcard character dash (-). The
wildcard does not identify a schema, but directs the resolve operation not to mark a
class invalid, because a reference to a matching name cannot be resolved. Use dash (-)
when you must test a class that refers to a class you cannot or do not want to load. For
11-14 Oracle Database Java Developer’s Guide
The loadjava Tool
example, GUI classes that a class refers to but does not call, because when run in the
server there is no GUI.
When looking for a schema object whose name matches the name specification, the
resolution operation looks in the schema named by the partner schema specification.
The resolution operation searches schemas in the order in which the resolver
specification lists them. For example,
-resolver '((* SCOTT) (* PUBLIC))'
This implies that search for any reference first in SCOTT and then in PUBLIC. If a
reference is not resolved, then mark the referring class invalid and display an error
message.
Consider the following example:
-resolver "((* SCOTT) (* PUBLIC) (my/gui/* -))"
This implies that search for any reference first in SCOTT and then in PUBLIC. If the
reference is to a class in the package my.gui and is not found, then mark the referring
class valid and do not display an error. If the reference is not to a class in my.gui and
is not found, then mark the referring class invalid and produce an error message.
user
{-user | -u} user/password[@database_url]
By default, loadjava loads into the logged in schema specified by the -user option.
You use the -schema option to specify a different schema to load into. This does not
require you to log in to that schema, but does require that you have sufficient
permissions to alter the schema.
The permissible forms of @database_url depend on whether you specify -oci or
-thin, as described:
■
■
-oci:@database_url is optional. If you do not specify, then loadjava uses
the user's default database. If specified, database_url can be a TNS name or an
Oracle Net Services name-value list.
-thin:@database_url is required. The format is host:lport:SID.
where:
–
host is the name of the computer running the database.
–
lport is the listener port that has been configured to listen for Oracle Net
Services connections. In a default installation, it is 5521.
–
SID is the database instance identifier. In a default installation, it is ORCL.
The following are examples of loadjava commands:
■
Connect to the default database with the default OCI driver, load the files in a JAR
into the TEST schema, and then resolve them:
loadjava -u joe -resolve -schema TEST ServerObjects.jar
Password: password
■
Connect with the JDBC Thin driver, load a class and a resource file, and resolve
each class:
loadjava -thin -u SCOTT@dbhost:5521:orcl \
-resolve alpha.class beta.props
Password: password
Schema Objects and Oracle JVM Utilities
11-15
The dropjava Tool
■
Add Betty and Bob to the users who can run alpha.class:
loadjava -thin -schema test -u SCOTT@localhost:5521:orcl \
-grant BETTY,BOB alpha.class
Password: password
jarsasdbobjects
This option indicates that JARs processed by the current loadjava command are to
be stored in the database along with the classes they contain, and knowledge of the
association between the classes and the JAR is to be retained in the database. In other
words, this argument indicates that the JARs processed by the current loadjava
command are to be stored in the database as database resident JARs.
prependjarnames
This option is used with the -jarsasdbobjects option. This option enables classes
with the same names coming from different JARs to coexist in the same schema.
The dropjava Tool
The dropjava tool is the converse of loadjava. It transforms command-line file
names and JAR or ZIP file contents to schema object names, drops the schema objects,
and deletes their corresponding digest table rows. You can enter .java, .class,
.sqlj, .ser, .zip, .jar, and resource file names on the command line and in any
order.
Alternatively, you can specify a schema object name directly to dropjava. A
command-line argument that does not end in .jar, .zip, .class, .java, or .sqlj
is presumed to be a schema object name. If you specify a schema object name that
applies to multiple schema objects, then all will be removed.
Dropping a class invalidates classes that depend on it, recursively cascading upwards.
Dropping a source drops classes derived from it.
You must remove Java schema objects in the same way that
you first loaded them. If you load a .sqlj source file and translate it
in the server, then you must run dropjava on the same source file. If
you translate on a client and load classes and resources directly, then
run dropjava on the same classes and resources.
Note:
You can run dropjava either from the command line or by using the dropjava
method in the DBMS_JAVA class. To run dropjava from within your Java application,
use the following command:
call dbms_java.dropjava('... options...');
The options are the same as specified on the command line. Separate each option with
a space. Do not separate the options using commas. The only exception to this is the
-resolver option. The connection is always made to the current session. Therefore,
you cannot specify another user name through the -user option.
For -resolver, you should specify all other options first, a comma (,), then the
-resolver option with its definition. Do not specify the -thin, -oci, -user, and
-password options, because they relate to the database connection for loadjava.
11-16 Oracle Database Java Developer’s Guide
The dropjava Tool
The output is directed to stderr. Set serveroutput on and call
dbms_java.set_output, as appropriate.
This section covers the following topics:
■
Syntax
■
Argument Summary
■
Argument Details
■
List Based Deletion
■
Dropping Resources
Syntax
The syntax of the dropjava command is:
dropjava [options] {file.java | file.class | file.sqlj |
file.jar | file.zip | resourcefile} ...
-u | -user user/[password][@database]
[-genmissingjar JARfile]
[-jarasresource]
[-o | -oci | -oci8]
[-optionfile file]
[-S | -schema schema]
[-stdout]
[-s | -synonym]
[-t | -thin]
[-v | -verbose]
Argument Summary
Table 11–3 summarizes the dropjava arguments.
Table 11–3
dropjava Argument Summary
Argument
Description
-user
Specifies a user name, password, and optional database connect
string. The files will be dropped from this database instance.
filenames
Specifies any number and combination of .java, .class, .sqlj,
.ser, .jar, .zip, and resource file names.
-genmissingjar
JARfile
Treats the operand of this option as a file to be processed.
-jarasresource
Drops the whole JAR file, which was previously loaded as a
resource.
-oci | -oci8
Directs dropjava to connect with the database using the OCI JDBC
driver. -oci and -thin are mutually exclusive. If neither is specified,
then -oci is used by default. Choosing -oci implies the form of the
-user value.
-optionfile file
Has the same usage as for loadjava.
-schema schema
Designates the schema from which schema objects are dropped. If
not specified, then the logon schema is used. To drop a schema
object from a schema that is not your own, you need the DROP ANY
PROCEDURE and UPDATE ANY TABLE privileges.
-stdout
Causes the output to be directed to stdout, rather than to stderr.
Schema Objects and Oracle JVM Utilities
11-17
The dropjava Tool
Table 11–3 (Cont.) dropjava Argument Summary
Argument
Description
-synonym
Drops a PUBLIC synonym that was created with loadjava.
-thin
Directs dropjava to communicate with the database using the
JDBC Thin driver. Choosing -thin implies the form of the -user
value.
-verbose
Directs dropjava to emit detailed status messages while running.
–list
Drops the classes, Java source, or resources listed on the command
line without them being present on the client machine or server
machine.
-listfile
Reads a file and drops the classes, Java source, or resources listed in
the file without them being present on the client machine or server
machine.The file contains the internal representation of the complete
class, Java source, or resource name one per line.
Argument Details
This section describes few of the dropjava argument, which are complex
File Names
dropjava interprets most file names as loadjava does:
■
.class files
Finds the class name in the file and drops the corresponding schema object.
■
.java and .sqlj files
Finds the first class name in the file and drops the corresponding schema object.
■
.jar and .zip files
Processes the archived file names as if they had been entered on the command
line.
If a file name has another extension or no extension, then dropjava interprets the file
name as a schema object name and drops all source, class, and resource objects that
match the name.
If dropjava encounters a file name that does not match a schema object, then it
displays a message and processes the remaining file names.
user
{-user | -u} user/password[@database]
The permissible forms of @database depend on whether you specify -oci or -thin:
■
■
-oci:@database is optional. If you do not specify, then dropjava uses the
user's default database. If specified, then database can be a TNS name or an
Oracle Net Services name-value list.
-thin:@database is required. The format is host:lport:SID.
where:
–
host is the name of the computer running the database.
–
lport is the listener port that has been configured to listen for Oracle Net
Services connections. In a default installation, it is 5521.
11-18 Oracle Database Java Developer’s Guide
The ojvmjava Tool
–
SID is the database instance identifier. In a default installation, it is ORCL.
The following are examples of dropjava.
■
Drop all schema objects in the TEST schema in the default database that were
loaded from ServerObjects.jar:
dropjava -u SCOTT -schema TEST ServerObjects.jar
Password: password
■
Connect with the JDBC Thin driver, then drop a class and a resource file from the
user's schema:
dropjava -thin -u SCOTT@dbhost:5521:orcl alpha.class beta.props
Password: password
List Based Deletion
Earlier versions of dropjava required that the classes, JARs, source, and resources be
present on the machine, where the client or server side utility is running. The current
version of dropjava has an option that enables you to drop classes, resources, or
sources based on a list of classes, which may not exist on the client machine or the
server machine. This list can be either on the command line or in a text file. For
example:
dropjava –list –u scott –v this.is.my.class this.is.your.class
Password: password
The preceding command drops the classes this.is.my.class and
this.is.your.class listed on the command line without them being present on
the client machine or server machine.
dropjava –listfile my.list –u scott –s –v
Password: password
The preceding command drops classes, resources, or sources and their synonyms
based on a list of classes listed in my.list and displays verbosely.
Dropping Resources
Care must be taken if you are removing a resource that was loaded directly into the
server. This includes profiles, if you translated them on the client without using the
-ser2class option. When dropping source or class schema objects or resource
schema objects that were generated by the server-side SQLJ translator, the schema
objects will be found according to the package specification in the applicable .sqlj
source file. However, the fully qualified schema object name of a resource that was
generated on the client and loaded directly into the server depends on path
information in the .jar file or that specified on the command line at the time you
loaded it. If you use a .jar file to load resources and use the same .jar file to remove
resources, then there will be no problem. However, if you use the command line to
load resources, then you must be careful to specify the same path information when
you run dropjava to remove the resources.
The ojvmjava Tool
The ojvmjava tool is an interactive interface to the session namespace of a database
instance. You specify database connection arguments when you start ojvmjava. It
then presents you with a prompt to indicate that it is ready for commands.
Schema Objects and Oracle JVM Utilities
11-19
The ojvmjava Tool
The shell can launch an executable, that is, a class with a static main() method.
This is done either by using the command-line interface or by calling a database
resident class. If you call a database resident class, the executable must be loaded with
loadjava.
This section covers the following topics:
■
Syntax
■
Argument Summary
■
Example
■
Functionality
Syntax
The syntax of the ojvmjava command is:
ojvmjava {-user user[/password@database ] [options]
[@filename]
[-batch]
[-c | -command command args]
[-debug]
[-d | -database conn_string]
[-fileout filename]
[-o | -oci | -oci8]
[-oschema schema]
[-t | -thin]
[-version | -v]
-runjava [server_file_system]
-jdwp port [host]
-verbose
Argument Summary
Table 11–4 summarizes the ojvmjava arguments.
Table 11–4
ojvmjava Argument Summary
Argument
Description
-user | -u
Specifies user name for connecting to the database. This name is
not case-sensitive. The name will always be converted to
uppercase. If you provide the database information, then the
default syntax used is OCI. You can also specify the default
database.
-password | -p
Specifies the password for connecting to the database. This is not
case-sensitive and will always be converted to uppercase.
@filename
Specifies a script file that contains the ojvmjava commands to
be run.
-batch
Disables all messages displayed to the screen. No help messages
or prompts will be displayed. Only responses to commands
entered are displayed.
-command
Runs the desired command. If you do not want to run
ojvmjava in interpretive mode, but only want to run a single
command, then run it with this option followed by a string that
contains the command and the arguments. Once the command
runs, ojvmjava exits.
11-20 Oracle Database Java Developer’s Guide
The ojvmjava Tool
Table 11–4 (Cont.) ojvmjava Argument Summary
Argument
Description
-debug
Displays debugging information.
-d | -database
conn_string
Provide a database connection string.
-fileout file
Redirect output to the provided file.
-o | -oci | -oci8
Uses the JDBC OCI driver. The OCI driver is the default. This
flag specifies the syntax used in either the @database or
-database option.
-o schema schema
Uses this schema for class lookup.
-t | -thin
Specifies that the database syntax used is for the JDBC Thin
driver. The database connection string must be of the form
host:port:SID or an Oracle Net Services name-value list.
-verbose
Displays the connection information.
-version
Shows the version.
-runjava
Uses DBMS_JAVA.runjava when executing Java commands.
With no argument, interprets -classpath as referring to the
client file system. With argument server_file_system
interprets -classpath as referring to the file system on which
the Oracle server is running, as DBMS_JAVA.runjava normally
does.
-jdwp
Makes the connection listen for a debugger connection on the
indicated port and host. The default value of host is
localhost.
Example
Open a shell on the session namespace of the database orcl on listener port 2481 on
the host dbserver, as follows:
ojvmjava -thin -user SCOTT@dbserver:2481:orcl
Password: password
Functionality
The ojvmjava commands span several different types of functionality, which are
grouped as follows:
■
ojvmjava Options
■
Shell Commands
ojvmjava Options
This section describes the options for the ojvmjava command-line tool
The ojvmjava Tool Output Redirection
You can direct any output generated by the ojvmjava tool to a file by appending
&>filename at the end of the command options. The following command directs all
output to the listDir file:
ls -lR &>/tmp/listDir
Schema Objects and Oracle JVM Utilities
11-21
The ojvmjava Tool
Scripting ojvmjava Commands in the @filename Option
This @filename option designates a script file that contains one or more ojvmjava
commands. The script file specified is located on the client. The ojvmjava tool reads
the file and runs all commands on the designated server. In addition, because the
script file is run on the server, any interaction with the operating system in the script
file, such as redirecting output to a file or running another script, will occur on the
server. If you direct ojvmjava to run another script file, then this file must exist in
$ORACLE_HOME on the server.
Enter the ojvmjava command followed by any options and any expected input
arguments.
The script file contains the ojvmjava command followed by options and input
parameters. The input parameters can be passed to ojvmjava on the command line.
ojvmjava processes all known options and passes on any other options and
arguments to the script file.
To access arguments within the commands in the script file, use &1...&n to denote
the arguments. If all input parameters are passed to a single command, then you can
type &* to denote that all input parameters are to be passed to this command.
The following shows the contents of the script file, execShell:
chmod +x SCOTT nancy /alpha/beta/gamma
chown SCOTT /alpha/beta/gamma
java hello.World &*
Because only two input arguments are expected, you can implement the Java
command input parameters, as follows:
java hello.World &1 &2
You can also supply arguments to the -command option in the
same manner. The following shows an example:
Note:
ojvmjava ... -command "cd &1" contexts
After processing all other options, ojvmjava passes contexts as
argument to the cd command.
To run this file, do the following:
ojvmjava -user SCOTT -thin -database dbserver:2481:orcl \
@execShell alpha beta
Password: password
ojvmjava processes all options that it knows about and passes along any other input
parameters to be used by the commands that exist within the script file. In this
example, the parameters, alpha and beta, are passed to the java command in the
script file. The actual command is run as follows:
java hello.World alpha beta
You can add any comments in your script file using hash (#). Comments are ignored
by ojvmjava. For example:
#this whole line is ignored by ojvmjava
11-22 Oracle Database Java Developer’s Guide
The ojvmjava Tool
-runjava
This option controls whether or not the ojvmjava shell command Java runs
executable classes using the command-line interface or database resident classes.
When the -runjava option is present the command-line interface is used. Otherwise,
the executable must be a database resident class that was previously loaded with
loadjava. Using the optional argument server_file_system means that the
-classpath terms are on the file system of the machine running the Oracle server.
Otherwise, they are interpreted as being on the file system of the machine running
ojvmjava.
See Also:
"Using Command-Line Interface" on page 3-9
-jdwp
This option specifies a debugger connection to listen for when the shell command
java is used to run an executable. This allows for debugging the executable. The
arguments specify the port and host. The default value of the host argument is
localhost. These are used to execute a call to DBMS_DEBUG_JDWP.CONNECT_TCP
from the RDBMS session, in which the executable is run.
Running sess_sh Within Applications
You can run sess_sh commands from within a Java or PL/SQL application using the
following commands:
Application Type
Command and Description
PL/SQL applications dbms_namespace.shell(in command VARCHAR2)
Your application can run individual commands on a unique session
instance. The state of the shell is preserved between different calls of
sess_sh within the same session. The following examples run the cd
command of the sess_sh tool within a PL/SQL application:
dbms_namespace.shell('cd /webdomains');
dbms_namespace.shell('ls &> /tmp/test');
To reset the state of the shell instance, run the exit command, as
follows:
dbms_namespace.shell('exit');
Schema Objects and Oracle JVM Utilities
11-23
The ojvmjava Tool
Application Type
Command and Description
Java applications
Instantiates oracle.aurora.namespace.shell.Shell within a
Java server object. After creation, you must initialize the Shell object
using its initialize method. Once initialized, you can run sess_sh
commands, as follows:
String commands="cd /webdomains\nls -l";
StringReader commandReader = new StringReader(commands);
Shell sh = new oracle.aurora.namespace.shell.Shell();
try
{
sh.initialize();
sh.invoke(new BufferedReader(commandReader), false);
}
catch (ToolsException te)
{
//Error executing the commands
}
Shell Commands
This section describes the following commands available within the ojvmjava shell:
■
echo
■
exit
■
help
■
java
■
version
■
whoami
■
connect
■
runjava
■
jdwp
Note:
An error is reported if you enter an unsupported command.
Table 11–5 summarizes the commands that share one or more common options, which
are summarized in Table 11–5:
Table 11–5
ojvmjava Command Common Options
Option
Description
-describe | -d
Summarizes the operation of the tool.
-help | -h
Summarizes the syntax of the tool.
-version
Shows the version.
echo
This command displays to stdout exactly what is indicated. This is used mostly in
script files.
11-24 Oracle Database Java Developer’s Guide
The ojvmjava Tool
The syntax is as follows:
echo [echo_string] [args]
echo_string is a string that contains the text you want written to the screen during
the shell script invocation and args are input arguments from the user. For example,
the following command displays out a notification:
echo "Adding an owner to the schema" &1
If the input argument is SCOTT, then the output would be:
Adding an owner to the schema SCOTT
exit
This command terminates ojvmjava. The syntax is as follows:
exit
For example, to leave a shell, use the following command:
$ exit
%
help
This command summarizes the syntax of the shell commands. You can also use the
help command to summarize the options for a particular command. The syntax is as
follows:
help [command]
java
This command is analogous to the JDK java command. It calls the static main()
method of a class. It does this either by using the command-line interface or using a
database resident class, depending on the setting of the runjava mode. In the latter
case, the class must have been previously loaded with loadjava. The command
provides a convenient way to test Java code that runs in the database. In particular, the
command catches exceptions and redirects the standard output and standard error of
the class to the shell, which displays them as with any other command output. The
destination of standard out and standard error for Java classes that run in the database
is one or more database server process trace files, which are inconvenient and may
require DBA privileges to read.
See Also:
"Using Command-Line Interface" on page 3-9
The syntax of the command with runjava mode off is:
java [-schema schema] class [arg1 ... argn]
The syntax of the command with runjava mode on is:
java [command-line options] class [arg1 ... argn]
where, command-line options can be any of those mentioned in Table 3–1.
Table 11–6 summarizes the arguments of this command.
Schema Objects and Oracle JVM Utilities
11-25
The ojvmjava Tool
Table 11–6
java Argument Summary
Argument
Description
class
Names the Java class schema object that is to be run.
-schema
Names the schema containing the class to be run. The default is
the invoker's schema. The schema name is case-sensitive.
arg1 ... argn
Arguments to the static main() method of the class.
Consider the following Java file, World.java:
package hello;
public class World
{
public World()
{
super();
}
public static void main(String[] argv)
{
System.out.println("Hello from Oracle Database");
if (argv.length != 0)
System.out.println("You supplied " + argv.length + " arguments: ");
for (int i = 0; i < argv.length; i++)
System.out.println(" arg[" + i + "] : " + argv[i]);
}
}
You can compile, load, publish, and run the class, as follows:
% javac hello/World.java
% loadjava -r -user SCOTT@localhost:2481:orcl hello/World.class
Password: password
% ojvmjava -user SCOTT -database localhost:2481:orcl
Password: password
$ java hello.World alpha beta
Hello from Oracle Database
You supplied 2 arguments:
arg[0] : alpha
arg[1] : beta
version
This command shows the version of the ojvmjava tool. You can also show the
version of a specified command. The syntax of this command is:
version [options] [command]
For example, you can display the version of the shell, as follows:
$ version
1.0
whoami
This command displays the user name of the user who logged in to the current
session. The syntax of the command is:
11-26 Oracle Database Java Developer’s Guide
The ojvmjava Tool
whoami
connect
This command enables the client to drop the current connection and connect to
different databases without having to reinvoke ojvmjava with a different connection
description.
The syntax of this command is:
connect [-service service] [-user user][-password password]
You can use this command as shown in the following examples:
connect -s thin@locahost:5521:orcl -u scott/tiger
connect -s oci@locahost:5521:orcl -u scott -p tiger
Table 11–7 summarizes the arguments of this command.
Table 11–7
connect Argument Summary
Argument
Description
-service | -s
Any valid JDBC driver URLS, namely, oci @<connection
descriptor> and thin@<host:port:db>
-user | -u
User to connect as
-password | -p
Password to connect with
runjava
This command queries or modifies the runjava mode. The runjava mode
determines whether or not the java command uses the command-line interface to run
executables. The java command:
■
Uses the command-like interface when runjava mode is on
■
Uses database resident executables when runjava mode is off
See Also:
"Using Command-Line Interface" on page 3-9
Using the runjava command with no arguments displays the current setting of
runjava mode.
Table 11–8 summarizes the arguments of this command.
Table 11–8
runjava Argument Summary
Argument
Description
off
Turns runjava mode off.
on
Turns runjava mode on.
server_file_system
Turns runjava mode on. Using this option means that
-classpath terms are on the file system of the machine
running the Oracle server. Otherwise, they are interpreted as
being on the file system of the machine running ojvmjava.
jdwp
This command queries or modifies whether and how a debugger connection is
listened for when an executable is run by the Java command.
Schema Objects and Oracle JVM Utilities
11-27
The ojvmjava Tool
The RDBMS session, prior to starting the executable, executes
a DBMS_DEBUG_JDWP.CONNECT_TCP call with the specified port and
host. This is called Listening.
Note:
Using this command with no arguments displays the current setting.
Table 11–9 summarizes the arguments of this command.
Table 11–9
jdwp Argument Summary
Argument
Description
off
Stops listening in future executables.
port
Enables listening and specifies the port to be used.
host
Enables listening and specifies the host to be used. The default
value for this argument is localhost.
11-28 Oracle Database Java Developer’s Guide
12
Database Web Services
This chapter provides an overview of database Web services and discusses how to call
existing Web services. This chapter contains the following sections:
■
Overview of Database Web Services
■
Using Oracle Database as Web Services Provider
■
Using Oracle Database as Web Services Consumer
Overview of Database Web Services
Web services enable application-to-application interaction over the Web, regardless of
platform, language, or data formats. The key ingredients, including Extensible Markup
Language (XML), Simple Object Access Protocol (SOAP), Web Services Description
Language (WSDL), and Universal Description, Discovery, and Integration (UDDI),
have been adopted across the entire software industry. Web services usually refer to
services implemented and deployed in middle-tier application servers. However, in
heterogeneous and disconnected environments, there is an increasing need to access
stored procedures, as well as data and metadata, through Web services interfaces.
The Database Web services technology is a database approach to Web services. It
works in the following two directions:
■
Accessing database resources as a Web service
■
Consuming external Web services from the database
Oracle Database can access Web services through PL/SQL packages and Java classes
deployed within the database. Turning Oracle Database into a Web service provider
leverages investment in Java stored procedures, PL/SQL packages, predefined SQL
queries, and data manipulation language (DML). Conversely, consuming external Web
services from the database, together with integration with the SQL engine, enables
Enterprise Information Integration.
Using Oracle Database as Web Services Provider
Web Services use industry-standard mechanisms to provide easy access to remote
content and applications, regardless of the platform and location of the provider and
implementation and data format. Client applications can query and retrieve data from
Oracle Database and call stored procedures using standard Web service protocols.
There is no dependency on Oracle-specific database connectivity protocols. This
approach is highly beneficial in heterogeneous, distributed, and disconnected
environments.
Database Web Services 12-1
Using Oracle Database as Web Services Provider
You can call into the database from a Web service, using the database as a service
provider. This enables you to leverage existing or new SQL, PL/SQL, Java stored
procedures, or Java classes within Oracle Database. You can access and manipulate
database tables from a Web service client.
This section covers the following topics:
■
How to Use JPublisher for Web Services Call-Ins
■
Features of Oracle Database as a Web Service Provider
■
JPublisher Support for Web Services Call-Ins to Oracle Database
How to Use JPublisher for Web Services Call-Ins
You can use JPublisher to generate Java wrappers that correspond to database
operations and deploy the wrappers as Web services in Oracle Application Server.
Figure 12–1 illustrates how you use JPublisher to publish PL/SQL packages, SQL
objects, collections, and packages as Java classes. Once published, these classes can be
accessed by any Web service through an Oracle Application Server Containers for
J2EE (OC4J) Web services servlet.
Figure 12–1 Web Services Call-In to the Database
Oracle Fusion Middleware
Oracle
Database
Decoding
End point implicity
specifies the type
of service provided
by the server
JPub
Generated
Java
Classes
OC4J
Web Services
Servlet
PL/SQL
Query
Java
DML
Encoding
SOAP response
per WSDL
Soap
Libraries
See Also:
XML
Parser
Oracle Database JPublisher User's Guide
Features of Oracle Database as a Web Service Provider
Using Oracle Database as a Web service provider offers the following features:
■
Enhances PL/SQL Web services
Improves PL/SQL Web services by extending the Web services support for
additional PL/SQL types, including CLOB, BLOB, XMLTYPE, REF CURSOR, and
PL/SQL records and tables. This enables you to use most of your existing PL/SQL
packages as Web services.
■
Exposes Java in the database as Web services
Exposes existing Java classes deployed in Oracle Database as Web services. Java
classes implementing data-related services can be migrated between the middle
tier and the database. Java portability results in database independence.
■
Provides SQL query Web services
12-2 Oracle Database Java Developer’s Guide
Using Oracle Database as Web Services Consumer
Leverages warehousing or business intelligence queries, data monitoring queries,
and any predefined SQL statements as Web services.
■
Enables DML Web services
Offers secure, persistent, transactional, and scalable logging, auditing, and
tracking operations implemented through SQL DML, as Web services. DML Web
services are implemented as atomic or group, or batch, INSERT, UPDATE, and
DELETE operations.
Using Web Services with Oracle XML DB
The Simple Object Access Protocol (SOAP) provides a standard way for applications to
use the internet to exchange information and access services that implement the
business logic. One available Oracle XML DB service lets you issue SQL and XQuery
queries and receive results as XML data. Another service provides access to all
PL/SQL stored functions and procedures, where you can customize the input and
output document formats without using a predefined Oracle XML DB WSDL when
accessing stored procedures and functions.
SOAP 1.1 is the version supported by Oracle XML DB. Applications use the HTTP
POST method to submit XML documents to the Oracle XML DB Web services. You can
configure the locations of all Oracle XML DB Web services, WSDL documents, and
security settings for the Web services using the Oracle XML DB configuration file.
See Also:
Oracle XML DB Developer's Guide
JPublisher Support for Web Services Call-Ins to Oracle Database
The following JPublisher features support Web services call-ins to the code running in
Oracle Database:
■
Generation of Java interfaces
■
JPublisher styles and style files
■
REF CURSOR returning and result set mapping
■
Options to filter what JPublisher publishes
■
Support for calling Java classes in the database without PL/SQL call specifications
■
Support for publishing SQL queries or DML statements
■
Support for unique method names
■
Support for Oracle Streams AQ
See Also:
Oracle Database JPublisher User's Guide
Using Oracle Database as Web Services Consumer
You can extend the storage, indexing, and searching capabilities of a relational
database to include semistructured and nonstructured data, including Web services, in
addition to enabling federated data. By calling Web services, the database can track,
aggregate, refresh, and query dynamic data produced on-demand, such as stock
prices, currency exchange rates, and weather information.
An example of using Oracle Database as a service consumer would be to call external
Web services from a predefined database job to retrieve inventory information from
multiple suppliers, and then update your local inventory database. Another example
Database Web Services 12-3
Using Oracle Database as Web Services Consumer
is that of a Web crawler, where a database job can be scheduled to collate product and
price information from a number of sources.
This section covers the following topics:
■
How to Use Oracle Database for Web Services Call-Outs
■
Web Service Data Sources (Virtual Table Support)
■
Features of Oracle Database as a Web Service Consumer
■
Overview of JPublisher Generation
■
Adjusting the Mapping of SQL Types
How to Use Oracle Database for Web Services Call-Outs
The Web services client code is written in SQL, PL/SQL, or Java to run inside Oracle
Database, which then calls the external Web service. You can call a Web service from a
Java client within the database, using one of the following methods:
■
SQL and PL/SQL call specifications
Start a Web service through a user-defined function call, which is generated
through JPublisher, either directly within a SQL statement or view or through a
variable.
■
Pure Java static proxy class
Use JPublisher to generate a client proxy class, which uses Java API for
XML-based remote procedure call (JAX-RPC). This method simplifies the Web
service invocation because the location of the service is already known without
needing to look up the service in the UDDI registry. The client proxy class does all
the work required to construct the SOAP request, including marshalling and
unmarshalling parameters.
■
Pure Java using dynamic invocation interface (DII) over JAX-RPC
Dynamic invocation provides the ability to construct the SOAP request and access
the service without the client proxy.
For Web services call-outs using PL/SQL, use the UTL_DBWS PL/SQL package. This
package essentially uses the same application programming interfaces (APIs) as the
DII classes.
You can use a Web services data source to process the results from any Web service
request.
Figure 12–2 illustrates how you can call a Web service from a Java client within the
database.
12-4 Oracle Database Java Developer’s Guide
Using Oracle Database as Web Services Consumer
Figure 12–2 Calling Web Services From Within the Database
Oracle Database
Web Services
JVM
WDSL
DII
SOAP
Static Java
PL/SQL
Call Spec
Java
Proxy Class
Database
module
as a Web
Service
Requestor
Web Service Data Sources (Virtual Table Support)
To access data that is returned from single or multiple Web service invocations, create
a virtual table using a Web service data source. This table lets you query a set of
returned rows as though it were a table.
The client calls a Web service and the results are stored in a virtual table in the
database. You can pass result sets from function to function. This enables you to set up
a sequence of transformation without a table holding intermediate results. To reduce
memory usage, you can return the result set rows, a few at a time, within a function.
By using Web services with the table function, you can manipulate a range of input
values from single or multiple Web services as a real table. In the following example,
the inner SELECT statement creates rows whose columns are used as arguments for
calling the CALL_WS Web service call-out.
SELECT column1, cloumn2, ...
FROM TABLE(WS_TABFUN(CURSOR(SELECT s FROM table_name)))
WHERE ...
The table expression in the preceding example can be used in other SQL queries, for
constructing views, and so on.
Figure 12–3 illustrates the support for virtual table.
Figure 12–3 Storing Results from Request in a Virtual Table
Oracle Database
Web Services
JVM
SOAP
Call out
to Web
Service
Virtual
database
table
Database
module
as a Web
Service
Requestor
Features of Oracle Database as a Web Service Consumer
Using Oracle Database as a Web service consumer provides the following features:
■
Consuming Web services form Java
Database Web Services 12-5
Using Oracle Database as Web Services Consumer
Provides an easy-to-use interface for Web services call-outs, thereby insulating
developers from low-level SOAP programming. Java classes running in the
database can directly call external Web services by using the previously loaded
Java proxy class or through dynamic invocation.
■
Consuming Web services from SQL and PL/SQL
Enables any SQL-enabled tool or application to transparently and easily consume
dynamic data from external Web services. After exposing Web services methods as
Java stored procedures, a PL/SQL wrapper on top of a Java stored procedure
hides all Java and SOAP programming details from the SQL client.
■
Using Web services data source
Enables application and data integration by turning external Web service into a
SQL data source, making the external Web service appear as regular SQL table.
This table function represents the output of calling external Web services and can
be used in a SQL query.
Overview of JPublisher Generation
JPublisher can receive the WSDL file from a Web service and create the static Java,
proxy class, or PL/SQL call specification.
Figure 12–4 illustrates creating Web Services Call-Out Stubs.
Figure 12–4 Creating Web Services Call-Out Stubs
Web Services
Static Java
WSDL
JPublisher
Proxy Class
PL/SQL Call Spec
This support is created through the following JPublisher key options:
■
-proxywsdl=url
Use this option to generate JAX-RPC static client proxies, given the WSDL
document at the specified URL. This option generates additional wrapper classes
to expose instance methods as static methods and generates PL/SQL wrappers.
It performs the following steps:
1.
Generates JAX-RPC client proxy classes.
2.
Generates wrapper classes to publish instance methods as static methods.
3.
Generates PL/SQL wrappers for classes that must be accessible from PL/SQL.
4.
Loads generated code into the database.
Note: The -proxywsdl option uses the -proxyclasses option
behind the scenes for steps 2 and 3, and takes the -proxyopts setting
as input.
Once generated, your database client can access the Web service through PL/SQL
using the call specifications or through the JAX-RPC client proxy classes. The
12-6 Oracle Database Java Developer’s Guide
Using Oracle Database as Web Services Consumer
PL/SQL wrappers use the static methods. A client would not normally access
any Web service using the static method directly.
■
-httpproxy=proxy_url
Where WSDL is accessed through a firewall, use this option to specify a proxy
URL to use in resolving the URL of the WSDL document.
■
-proxyclasses=class_list
For Web services, this option is used behind the scenes by the -proxywsdl option
and is set automatically, as appropriate. In addition, you can use this option
directly, for general purposes, any time you want to create PL/SQL wrappers for
Java classes with static methods, and optionally to produce wrapper classes to
expose instance methods as static methods.
The -proxyclasses option accepts the -proxyopts setting as input.
■
-proxyopts=wrapper_specifications
This option specifies JPublisher behavior in generating wrapper classes and
PL/SQL wrappers, usually, but not necessarily, for Web services. For typical usage
of the -proxywsdl option, the -proxyopts default setting is sufficient. In
situations where you use the -proxyclasses option directly, you may want to
use the special -proxyopts settings.
■
-endpoint=Web_services_endpoint
Use this option in conjunction with the -proxywsdl option to specify the Web
services endpoint.
■
-sysuser=superuser_name/superuser_password
Use this option to specify the name and password for the superuser account used
to grant permissions for the client proxy classes to access Web services using
HTTP.
Adjusting the Mapping of SQL Types
Although Oracle Application Server does not currently support LOB types, XMLTYPE,
REF CURSORS, and OUT and IN OUT arguments, you can use an alternative approach
to expose PL/SQL methods and SQL types as Web services.
You can change the default action of JPublisher to generate code that uses a
user-provided subclass. For example, if you have a PL/SQL method that returns a REF
CURSOR, then JPublisher automatically maps the return type to
java.sql.ResultSet. However, this ResultSet type cannot be published as a
Web service. To solve this, create a new method that can return the result set in a Web
service-supported format, as follows:
public String [] readRefCursorArray(String arg1, Integer arg2)
{
java.sql.ResultSet rs = getRefCursor(arg1,arg2);
...
//create a String[] from rs and return it
...
}
After creating a method, create an interface that contains the exact methods to publish.
You can use JPublisher to easily accomplish this mapping by using the following
command:
jpub -sql=MYAPP:MyAppBase:MyApp#MyAppInterf...
Database Web Services 12-7
Using Oracle Database as Web Services Consumer
In the preceding command:
■
MyApp contains the method to return the result set.
■
MyAppInterf is the interface that contains the method to publish.
After translating the code for your application, archive all the class files into a single
Java Archive (JAR) file and use the Web Services Assembler to create a deployable Web
service Enterprise Archive (EAR) file.
See Also:
Oracle Database JPublisher User's Guide
12-8 Oracle Database Java Developer’s Guide
A
DBMS_JAVA Package
This chapter provides a description of the DBMS_JAVA package. The functions and
procedures in this package provide an entry point for accessing RDBMS functionality
from Java.
longname
FUNCTION longname (shortname VARCHAR2) RETURN VARCHAR2
The function returns the fully qualified name of the specified Java schema object.
Because Java classes and methods can have names exceeding the maximum SQL
identifier length, Oracle JVM uses abbreviated names internally for SQL access. This
function returns the original Java name for any truncated name. An example of this
function is to display the fully qualified name of classes that are invalid:
SELECT dbms_java.longname (object_name) FROM user_objects
WHERE object_type = 'JAVA CLASS' AND status = 'INVALID';
shortname
FUNCTION shortname (longname VARCHAR2) RETURN VARCHAR2
You can specify a full name to the database by using the shortname() routine of the
DBMS_JAVA package, which takes a full name as input and returns the corresponding
short name. This is useful when verifying that your classes loaded by querying the
USER_OBJECTS view.
get_compiler_option
FUNCTION get_compiler_option(name VARCHAR2, optionName VARCHAR2) RETURN VARCHAR2
This function returns the value of the option specified through the optionName
parameter. It is one of the functions used to control the options of the Java and SQLJ
compiler supplied with Oracle Database.
See Also:
"Compiler Options Specified in a Database Table" on
page 2-7
set_compiler_option
PROCEDURE set_compiler_option(name VARCHAR2, optionName VARCHAR2, value VARCHAR2)
DBMS_JAVA Package A-1
reset_compiler_option
This procedure is used to set the options of the Java and SQLJ compiler supplied with
Oracle Database.
See Also:
"Compiler Options Specified in a Database Table" on
page 2-7
reset_compiler_option
PROCEDURE reset_compiler_option(name VARCHAR2, optionName VARCHAR2)
This procedure is used to reset the specified compiler option to the default value.
See Also:
"Compiler Options Specified in a Database Table" on
page 2-7
resolver
FUNCTION resolver (name VARCHAR2, owner VARCHAR2, type VARCHAR2) RETURN VARCHAR2
This function returns the resolver specification for the object specified in name and in
the schema specified in owner, where the object is of the type specified in type. The
caller must have EXECUTE privilege and have access to the given object to use this
function.
The name parameter is the short name of the object.
The value of type can be either SOURCE or CLASS.
If there is an error, then NULL is returned. If the underlying object has changed, then
ObjectTypeChangedException is thrown.
You can call this function as follows:
SELECT dbms_java.resolver('tst', 'SCOTT', 'CLASS') FROM DUAL;
This would return:
DBMS_JAVA.RESOLVER('TST','SCOTT','CLASS')
----------------------------------------((* SCOTT)(* PUBLIC))
derivedFrom
FUNCTION derivedFrom (name VARCHAR2, owner VARCHAR2, type VARCHAR2) RETURN
VARCHAR2
This function returns the source name of the object specified in name of the type
specified in type and in the schema specified in owner. The caller must have
EXECUTE privilege and have access to the given object to use this function.
The name parameter, as well as the returned source name, is the short name of the
object.
The value of type can be either SOURCE or CLASS.
If there is an error, then NULL is returned. If the underlying object has changed, then
ObjectTypeChangedException is thrown.
The returned value will be NULL if the object was not compiled in Oracle JVM.
A-2 Oracle Database Java Developer’s Guide
start_debugging
You can call this function as follows:
SELECT dbms_java.derivedFrom('tst', 'SCOTT', 'CLASS') FROM DUAL;
This would return:
DBMS_JAVA.DERIVEDFROM('TST','SCOTT','CLASS')
----------------------------------------tst
fixed_in_instance
FUNCTION fixed_in_instance (name VARCHAR2, owner VARCHAR2, type VARCHAR2) RETURN
NUMBER
This function returns the permanently kept status for object specified in name of the
type specified in type and in the schema specified in owner. The caller must have
EXECUTE privilege and have access to the given object to use this function.
The name parameter is the short name for the object.
The value of type can be either of RESOURCE, SOURCE, CLASS, or SHARED_DATA.
The number returned is either 0, indicating the status is not kept, or 1, indicating the
status is kept.
You can call this function as follows:
SELECT dbms_java.fixed_in_instance('tst', 'SCOTT', 'CLASS') FROM DUAL;
This would return:
DBMS_JAVA.FIXED_IN_INSTANCE('TST','SCOTT','CLASS')
----------------------------------------0
Consider the following statement:
SELECT dbms_java.fixed_in_instance('java/lang/String', 'SYS', 'CLASS') FROM DUAL;
This would return:
DBMS_JAVA.FIXED_IN_INSTANCE('JAVA/LANG/STRING','SYS','CLASS')
------------------------------------------------------------1
set_output
PROCEDURE set_output (buffersize NUMBER)
This procedure redirects the output of Java stored procedures and triggers to the
DBMS_OUTPUT package.
start_debugging
PROCEDURE start_debugging(host VARCHAR2, port NUMBER, timeout NUMBER)
This procedure is used to start the debug agent on the specified host at the specified
port
DBMS_JAVA Package A-3
stop_debugging
stop_debugging
PROCEDURE stop_debugging
This procedure is used to stop the debug agent
restart_debugging
PROCEDURE restart_debugging(timeout NUMBER)
This procedure is used to restart the debug agent.
export_source
PROCEDURE export_source(name VARCHAR2, schema VARCHAR2, blob BLOB)
PROCEDURE export_source(name VARCHAR2, blob BLOB)
PROCEDURE export_source(name VARCHAR2, clob CLOB)
These procedures are used to export the Java source as a Java source schema object to
Oracle Database. The source is specified through the name parameter. The source can
be exported into a BLOB or CLOB object. The internal representation of the source uses
the UTF8 format, so that format is used to store the source in the BLOB as well. The
source schema object is created in the specified schema. If the schema is not specified
then the current schema is used.
export_class
PROCEDURE export_class(name VARCHAR2, schema VARCHAR2, blob BLOB)
PROCEDURE export_class(name VARCHAR2, blob BLOB)
These procedures are used to export Java classes specified through the name
parameter as Java class schema objects to Oracle Database. You cannot export a class
into a CLOB object, only into a BLOB object. If the schema is specified, then the class
schema object is created in this schema, else in the current schema.
export_resource
PROCEDURE export_resource(name VARCHAR2, schema VARCHAR2, blob BLOB)
PROCEDURE export_resource(name VARCHAR2, blob BLOB)
PROCEDURE export_resource(name VARCHAR2, schema VARCHAR2, clob CLOB)
PROCEDURE export_resource(name VARCHAR2, clob CLOB)
The resource specified through the name parameter is exported to Oracle Database as
a resource schema object in the schema specified through the schema parameter. If the
schema is not specified then the current schema is used. The resource can be exported
into either a CLOB object or BLOB object.
loadjava
PROCEDURE loadjava(options VARCHAR2)
A-4 Oracle Database Java Developer’s Guide
grant_policy_permission
PROCEDURE loadjava(options VARCHAR2, resolver VARCHAR2)
These procedures enable you to load classes in to the database using a call, rather than
through the loadjava command-line tool. You can call this procedure within your
Java application as follows:
CALL dbms_java.loadjava('... options...');
The options are identical to those specified on the command line. Each option should
be separated by a space. Do not separate the options with a comma. The only
exception to this is the loadjava -resolver option, which contains spaces. For
-resolver, specify all other options first, separate these options by a comma, and
then specify the -resolver options, as follows:
CALL dbms_java.loadjava('... options...', 'resolver_options');
Do not specify the -thin, -oci, -user, and -password options, because they relate
to the database connection. The output is directed to System.err. The output
typically goes to a trace file, but can be redirected.
dropjava
PROCEDURE dropjava(options VARCHAR2)
This procedure enables you to drop classes within the database using a call, rather
than through the dropjava command-line tool. You can call this procedure within
your Java application as follows:
CALL dbms_java.dropjava('... options...');
grant_permission
PROCEDURE grant_permission(grantee VARCHAR2, permission_type VARCHAR2,
permission_name VARCHAR2, permission_action VARCHAR2)
This method is used to grant permission to specific users or roles.
See Also:
"Fine-Grain Definition for Each Permission" on page 10-5
restrict_permission
PROCEDURE restrict_permission(grantee VARCHAR2, permission_type VARCHAR2,
permission_name VARCHAR2, permission_action VARCHAR2)
This method is used to specify limitations or exceptions to general rules.
See Also:
"Fine-Grain Definition for Each Permission" on page 10-5
grant_policy_permission
PROCEDURE grant_policy_permission(grantee VARCHAR2, permission_schema VARCHAR2,
permission_type VARCHAR2,
permission_name VARCHAR2)
This method is used to grant and limit PolicyTablePermission.
DBMS_JAVA Package A-5
revoke_permission
"Acquiring Administrative Permission to Update Policy
Table" on page 10-8
See Also:
revoke_permission
PROCEDURE revoke_permission(permission_schema VARCHAR2, permission_type VARCHAR2,
permission_name VARCHAR2,
permission_action VARCHAR2)
This method is used to disable a granted permission.
See Also:
"Enabling or Disabling Permissions" on page 10-12
disable_permission
PROCEDURE disable_permission(key NUMBER)
This method is used to disable a granted permission.
See Also:
"Enabling or Disabling Permissions" on page 10-12
enable_permission
PROCEDURE enable_permission(key NUMBER)
This method is used to enable a permission.
See Also:
"Enabling or Disabling Permissions" on page 10-12
delete_permission
PROCEDURE delete_permission(key NUMBER)
This method is used to delete a granted permission.
See Also:
"Enabling or Disabling Permissions" on page 10-12
set_preference
procedure set_preference(user VARCHAR2, type VARCHAR2, abspath VARCHAR2, key
VARCHAR2, value VARCHAR2)
This procedure inserts or updates a row in the SYS:java$prefs$ table as follows:
CALL dbms_java.set_preference('SCOTT', 'U', '/my/package/method/three',
'windowsize', '22:32');
The user parameter specifies the name of the schema to which the preference should
be attached. If the logged in schema is not SYS, then user must specify the current
logged in schema or the INSERT will fail. The type parameter can take either the
value U, indicating user preference, or S, indicating system preference. The abspath
parameter specifies the absolute path for the preference. key is the preference key
used for the lookup, and value is the value of the preference key.
runjava
FUNCTION runjava(cmdline VARCHAR2) RETURN VARCHAR2;
A-6 Oracle Database Java Developer’s Guide
remove_property
This function takes the Java command line as its only argument and runs it in Oracle
JVM.
See Also:
"Using Command-Line Interface" on page 3-9
runjava_in_current_session
FUNCTION runjava_in_current_session(cmdline VARCHAR2) RETURN VARCHAR2;
This function is the same as the runjava function, except that it does not clear Java
state remaining from previous use of Java in the session, prior to executing the current
command line.
See Also:
"Using Command-Line Interface" on page 3-9
set_property
FUNCTION set_property(name VARCHAR2, value VARCHAR2) RETURN VARCHAR2;
This function enables you to establish a value for a system property that is then used
for the duration of the current RDBMS session, whenever a Java session is initialized.
In order to execute the SET_PROPERTY function, a user must
have write permission on SYS:java.util.PropertyPermission
for the property name. You can grant this permission using the
following command:
Note:
call dbms_java.grant_permission( '<user_name>',
'SYS:java.util.PropertyPermission', '<property_name>', 'write' );
See Also:
"Setting System Properties" on page 4-4
get_property
FUNCTION get_property(name VARCHAR2) RETURN VARCHAR2;
This function returns any value previously established by set_property.
See Also:
"Setting System Properties" on page 4-4
remove_property
FUNCTION remove_property(name VARCHAR2) RETURN VARCHAR2;
This function removes any value previously established by set_property.
DBMS_JAVA Package A-7
show_property
In order to execute the remove_property function, a user
must have write permission on
SYS:java.util.PropertyPermission for the property name.
You can grant this permission using the following command:
Note:
call dbms_java.grant_permission( '<user_name>',
'SYS:java.util.PropertyPermission', '<property_name>', 'write' );
See Also:
"Setting System Properties" on page 4-4
show_property
FUNCTION show_property(name VARCHAR2) RETURN VARCHAR2;
This function displays a message of the form name = value for the input name, or
for all established property bindings, if name is null.
See Also:
"Setting System Properties" on page 4-4
set_output_to_sql
FUNCTION set_output_to_sql (id VARCHAR2,
stmt VARCHAR2,
bindings VARCHAR2,
no_newline_stmt VARCHAR2 default null,
no_newline_bindings VARCHAR2 default null,
newline_only_stmt VARCHAR2 default null,
newline_only_bindings VARCHAR2 default null,
maximum_line_segment_length NUMBER default 0,
allow_replace NUMBER default 1,
from_stdout NUMBER default 1,
from_stderr NUMBER default 1,
include_newlines NUMBER default 0,
eager NUMBER default 0) return VARCHAR2;
set_output_to_sql defines a named output specification that constitutes an
instruction for executing a SQL statement, whenever output to the default
System.out and System.err streams occurs.
See Also:
"Redirecting Output on the Server" on page 3-14
remove_output_to_sql
FUNCTION remove_output_to_sql (id VARCHAR2) return VARCHAR2;
remove_output_to_sql deletes a specification created by set_output_to_sql.
See Also:
"Redirecting Output on the Server" on page 3-14
enable_output_to_sql
FUNCTION enable_output_to_sql (id VARCHAR2) return VARCHAR2;
A-8 Oracle Database Java Developer’s Guide
remove_output_to_java
enable_output_to_sql reenables a specification created by set_output_to_sql
and subsequently disabled by disable_output_to_sql.
See Also:
"Redirecting Output on the Server" on page 3-14
disable_output_to_sql
FUNCTION disable_output_to_sql (id VARCHAR2) return VARCHAR2;
disable_output_to_sql disables a specification created by
set_output_to_sql.
See Also:
"Redirecting Output on the Server" on page 3-14
query_output_to_sql
FUNCTION query_output_to_sql (id VARCHAR2) return VARCHAR2;
query_output_to_sql returns a message describing a specification created by
set_output_to_sql.
See Also:
"Redirecting Output on the Server" on page 3-14
set_output_to_java
FUNCTION set_output_to_java (id VARCHAR2,
class_name VARCHAR2,
class_schema VARCHAR2,
method VARCHAR2,
bindings VARCHAR2,
no_newline_method VARCHAR2 default null,
no_newline_bindings VARCHAR2 default null,
newline_only_method VARCHAR2 default null,
newline_only_bindings VARCHAR2 default null,
maximum_line_segment_length NUMBER default 0,
allow_replace NUMBER default 1,
from_stdout NUMBER default 1,
from_stderr NUMBER default 1,
include_newlines NUMBER default 0,
eager NUMBER default 0,
initialization_statement VARCHAR2 default null,
finalization_statement VARCHAR2 default null)return VARCHAR2;
set_output_to_java defines a named output specification that gives an indication
for executing a Java method whenever output to the default System.out and
System.err streams occurs.
See Also:
"Redirecting Output on the Server" on page 3-14
remove_output_to_java
FUNCTION remove_output_to_java (id VARCHAR2) return VARCHAR2;
remove_output_to_java deletes a specification created by
set_output_to_java.
See Also:
"Redirecting Output on the Server" on page 3-14
DBMS_JAVA Package A-9
enable_output_to_java
enable_output_to_java
FUNCTION enable_output_to_java (id VARCHAR2) return VARCHAR2;
enable_output_to_java reenables a specification created by
set_output_to_java and subsequently disabled by disable_output_to_java.
See Also:
"Redirecting Output on the Server" on page 3-14
disable_output_to_java
FUNCTION disable_output_to_java (id VARCHAR2) return VARCHAR2;
disable_output_to_java disables a specification created by
set_output_to_java.
See Also:
"Redirecting Output on the Server" on page 3-14
query_output_to_java
FUNCTION query_output_to_java (id VARCHAR2) return VARCHAR2;
query_output_to_java returns a message describing a specification created by
set_output_to_java.
See Also:
"Redirecting Output on the Server" on page 3-14
set_output_to_file
FUNCTION set_output_to_file (id VARCHAR2,
file_path VARCHAR2,
allow_replace NUMBER default 1,
from_stdout NUMBER default 1,
from_stderr NUMBER default 1) return VARCHAR2;
set_output_to_file defines a named output specification that constitutes an
instruction to capture any output sent to the default System.out and
System.err streams and append it to a specified file.
See Also:
"Redirecting Output on the Server" on page 3-14
remove_output_to_file
FUNCTION remove_output_to_file (id VARCHAR2) return VARCHAR2;
remove_output_to_file deletes a specification created by
set_output_to_file.
See Also:
"Redirecting Output on the Server" on page 3-14
enable_output_to_file
FUNCTION enable_output_to_file (id VARCHAR2) return VARCHAR2;
enable_output_to_file reenables a specification created by
set_output_to_file and subsequently disabled by disable_output_to_file.
A-10 Oracle Database Java Developer’s Guide
endsession
See Also:
"Redirecting Output on the Server" on page 3-14
disable_output_to_file
FUNCTION disable_output_to_file (id VARCHAR2) return VARCHAR2;
disable_output_to_file disables a specification created by
set_output_to_file.
See Also:
"Redirecting Output on the Server" on page 3-14
query_output_to_file
FUNCTION query_output_to_file (id VARCHAR2) return VARCHAR2;
query_output_to_file returns a message describing a specification created by
set_output_to_file.
See Also:
"Redirecting Output on the Server" on page 3-14
enable_output_to_trc
PROCEDURE enable_output_to_trc;
This procedure prevents the output from going to the default location, that is, .trc
file.
See Also:
"Redirecting Output on the Server" on page 3-14
disable_output_to_trc
PROCEDURE disable_output_to_trc;
This procedure prevents the output from going to the default location, that is, .trc
file.
See Also:
"Redirecting Output on the Server" on page 3-14
query_output_to_trc
FUNCTION query_output_to_trc return VARCHAR2;
This function prevents the output from going to the default location, that is, .trc file.
See Also:
"Redirecting Output on the Server" on page 3-14
endsession
FUNCTION endsession RETURN VARCHAR2;
This function clears any Java session state remaining from previous execution of Java
in the current RDBMS session.
See Also:
"Two-Tier Duration for Java Session State" on page 4-4
DBMS_JAVA Package
A-11
endsession_and_related_state
endsession_and_related_state
FUNCTION endsession_and_related_state RETURN VARCHAR2;
This function clears any Java session state remaining from previous execution of Java
in the current RDBMS session and all supporting data related to running Java.
See Also:
"Two-Tier Duration for Java Session State" on page 4-4
set_native_compiler_option
PROCEDURE set_native_compiler_option(optionName VARCHAR2,
value VARCHAR2);
This procedure sets a native-compiler option to the specified value for the current
schema.
See Also:
"Oracle JVM Just-in-Time Compiler (JIT)" on page 9-1
unset_native_compiler_option
PROCEDURE unset_native_compiler_option(optionName VARCHAR2,
value VARCHAR2);
This procedure unsets a native-compiler option/value pair for the current schema.
See Also:
"Oracle JVM Just-in-Time Compiler (JIT)" on page 9-1
compile_class
FUNCTION compile_class(classname VARCHAR2) return NUMBER;
This function compiles all methods defined by the class that is identified by classname
in the current schema.
See Also:
"Oracle JVM Just-in-Time Compiler (JIT)" on page 9-1
compile_class
FUNCTION compile_class(schema VARCHAR2,
classname VARCHAR2) return NUMBER;
This function compiles all methods defined by the class that is identified by classname
in the supplied schema.
See Also:
"Oracle JVM Just-in-Time Compiler (JIT)" on page 9-1
uncompile_class
FUNCTION uncompile_class(classname VARCHAR2,
permanentp NUMBER default 0) return NUMBER;
This function uncompiles all methods defined by the class that is identified by
classname in the current schema.
See Also:
"Oracle JVM Just-in-Time Compiler (JIT)" on page 9-1
A-12 Oracle Database Java Developer’s Guide
uncompile_method
uncompile_class
FUNCTION uncompile_class(schema VARCHAR2,
classname VARCHAR2,
permanentp NUMBER default 0) return NUMBER;
This function uncompiles all methods defined by the class that is identified by
classname in the supplied schema.
See Also:
"Oracle JVM Just-in-Time Compiler (JIT)" on page 9-1
compile_method
FUNCTION compile_method(classname VARCHAR2,
methodname VARCHAR2,
methodsig VARCHAR2) return NUMBER;
This function compiles the method specified by name and Java type signatures defined
by the class, which is identified by classname in the current schema.
See Also:
"Oracle JVM Just-in-Time Compiler (JIT)" on page 9-1
compile_method
FUNCTION compile_method(schema VARCHAR2,
classname VARCHAR2,
methodname VARCHAR2,
methodsig VARCHAR2) return NUMBER;
This function compiles the method specified by name and Java type signatures defined
by the class that is identified by classname in the supplied schema.
See Also:
"Oracle JVM Just-in-Time Compiler (JIT)" on page 9-1
uncompile_method
FUNCTION uncompile_method(classname VARCHAR2,
methodname VARCHAR2,
methodsig VARCHAR2,
permanentp NUMBER default 0) return NUMBER;
This function uncompiles the method specified by the name and Java type signatures
defined by the class that is identified by classname in the current schema.
See Also:
"Oracle JVM Just-in-Time Compiler (JIT)" on page 9-1
uncompile_method
FUNCTION uncompile_method(schema VARCHAR2,
classname VARCHAR2,
methodname VARCHAR2,
methodsig VARCHAR2,
permanentp NUMBER default 0) return NUMBER;
This function uncompiles the method specified by the name and Java type signatures
defined by the class that is identified by classname in the supplied schema.
See Also:
"Oracle JVM Just-in-Time Compiler (JIT)" on page 9-1
DBMS_JAVA Package
A-13
uncompile_method
A-14 Oracle Database Java Developer’s Guide
B
Classpath Extensions and User Classloaded
Metadata
This section provides a description of the extensions to the -classpath search path
and User Classloaded Metadata.
B.1 Classpath Extensions
This section provides a description of the extensions to the -classpath search path
and jserver URL protocol syntaxes that allow specification of database resident
objects and byte sets in search paths used by the command-line interface.
B.1.1 jserverQuotedClassPathTermPrefix
When a classpath term begins with the jserverQuotedClassPathTermPrefix
string, it extends through the next occurrence of the string, regardless of the
File.pathSeparator characters it may contain. The actual value of this string is
given by the system property jserver.quoted.classpath.term.prefix. If this
property is not defined, the default value is ||.
B.1.2 jserverURLPrefix
When a dequoted classpath term begins with the jserverURLPrefix string, the rest
of the term is treated as a URL. The value of this string is given by the system property
jserver.url.in.classpath.prefix. If this value is null, any quoted term
that does not begin with one of the following three prefixes, is treated as a URL:
■
jserverSpecialTokenPrefix, if the value is set
■
JSERVER_CP
■
JSERVER_SCHEMAc
A quoted term is one that begins and ends with the string that
is the value of jserverQuotedClassPathTermPrefix. A
dequoted term is either the whole original term if it is not quoted, or
the part of a quoted term between the beginning and ending
occurrences of jserverQuotedClassPathTermPrefix.
Note:
B.1.3 jserverSpecialTokenPrefix
The value of the jserverSpecialTokenPrefix string is given by the system
property jserver.specialtoken.in.classpath.prefix. If this value is not
Classpath Extensions and User Classloaded Metadata
B-1
Classpath Extensions
null, then the prefixes JSERVER_CP and JSERVER_SCHEMAc are recognized only
when preceded by this string.
See Also:
"JSERVER_CP" on page B-2 and "JSERVER_SCHEMAc"
on page B-2
B.1.4 JSERVER_CP
A classpath term beginning with the literal substring "JSERVER_CP" is converted to a
URL by replacing JSERVER_CP with jserver:/CP.
B.1.5 JSERVER_SCHEMAc
A classpath term beginning with the literal substring "JSERVER_SCHEMAc" is
converted to a URL by replacing JSERVER_SCHEMAc with jserver:/CPcSCHEMAc.
Here c can be any character, but is typically /. This means that a term of the form
JSERVER_SCHEMAc + <remaining string> is treated as a prescription for
looking for shared system classloaded classes and resources in the schema identified
by <remaining string>. For example, the term JSERVER_SCHEMA/SCOTT is
equivalent to jserver:/CP/SCOTT and it instructs to look for shared classes and
resources in the schema named SCOTT.
B.1.6 jserver:/CP general syntax
A URL beginning with jserver:/CP is meaningful only as a classpath term. The first
character following jserver:/CP is used as the token separator for the remainder of
the string. This is typically the character /. The subsequent tokens are the following:
■
■
■
■
■
The possible values of the first token are JAR, RESOURCE, or SHARED_DATA,
where RESOURCE indicates a Java resource object, SHARED_DATA indicates a
Java shared data object, and JAR indicates a database resident JAR object. This
token is optional and all of the values are case-insensitive. If one of these is
present, the URL is called a JAR specifier. Otherwise, it is called a SCHEMA
specifier.
The value of the second token is PRIVATE. This is an optional token and is
case-insensitive.
The value of the third token is SCHEMA. This is a required token and is
case-insensitive.
The fourth token is a required token, which is interpreted as a schema name.
The fifth token is required for a JAR specifier and prohibited for a SCHEMA
specifier. It is interpreted as the name of an object in the schema identified by the
fourth token, if present.
Functionally, a classpath term is used to look for an object that matches a class or
resource name that is being searched for. In the case of a SCHEMA specifier, the object
is looked for in the indicated schema. In the case of a JAR specifier, a particular object
in the schema is identified by the fifth token in the URL. This object is treated as a JAR
and the searched for object is looked for by name, within that JAR. In the case of
looking for a class within a database resident JAR, this may mean finding the class as a
class object in the schema. Otherwise, it means finding the search object in the actual
bytes of the JAR object.
The searched for object is a database Java class object, if it meets the following
conditions:
■
The search name ends in .class
B-2 Oracle Database Java Developer’s Guide
User Classloaded Metadata
■
the URL is either a SCHEMA specifier or a JAR specifier for a database resident
JAR
Such a class object may be:
■
■
Loaded as a shared system classloaded class. This is done if the optional second
token PRIVATE is not present.
Interpreted as a set of bytecodes and loaded by the defineClass method as a
private user classloaded class. This is done if the optional second token PRIVATE
is present.
Note: Classes loaded from classpath terms not beginning with the
jserver URL marker are always private, user classloaded classes.
B.2 User Classloaded Metadata
Starting from 11g release 1 (11.1), there is a new system table created in the following
manner in javavm/install/initjvma.sql during database creation and upgrade:
create table java$jvm$runtime$parameters (owner# number not null,flags number);
create unique index java$jvm$runtime$parameters$i on
java$jvm$runtime$parameters(owner#);
This table is removed during downgrade by javavm/install/rmjvm.sql. If you
want to share private class metadata and have DBA privileges, then you can populate
this table manually. The rule is that if there is a row matching your owner ID, then the
flag value of this row is bitwise anded with the flag value from the row with owner# =
-1, if any. If none of these previously mentioned rows exist, then the bit set in the result
is -1, that is, all bits set. If bit 0 (1<<0) is set in the result, then your session attempts to
share existing shared private metadata. If bit 1 (1<<1) is set in the result, then the
session creates shared metadata when existing shared metadata is not found. By
default, there is no row in the table. So, all sessions both use and create shared private
metadata.
Classpath Extensions and User Classloaded Metadata
B-3
User Classloaded Metadata
B-4 Oracle Database Java Developer’s Guide
Index
A
act method, 2-36
application
compiling, 2-5
developing, 8-1
development, 2-1
executing in a session, 2-1
execution control, 2-3
execution rights, 2-15
invoking, 3-1
running on the server, 3-14
threading, 2-32
attributes, 5-2, 6-12
declaring, 6-13
definition, 1-2
types of, 1-2
authentication, 10-1
mechanisms, 10-18
AUTHID clause, 6-7, 6-10, 6-13
B
BasicPermission, 10-9
body
package, 6-10
SQL object type, 6-13
bytecode
defined, 1-6
definition, 1-18
verification, 2-11
verifier, 2-11
C
call
definition, 1-15
managing resources across calls, 2-39
static fields, 2-2
call memory, 2-3
call specification, 3-1
defining, 6-2
mapping data types, 6-3
object type, 6-12
packaged, 6-10
top-level, 6-6
understanding, 6-1
Callback class
act method, 2-36
calss
loader, 1-18
class
attributes, 1-2
auditing, 2-20
definition, 1-2
dynamic loading, 1-14
execution, 2-3
hierarchy, 1-7
inheritance, 1-7
interpretation, 2-3
loading, 2-3, 2-12
loading permission, 10-18
marking valid, 2-10
methods, 1-2
name, 2-22
publish, 2-19, 6-1
resolving dependencies, 2-9
resolving reference, 2-9
schema object, 2-3, 2-10, 2-12, 2-13
shortened name, 2-22
single inheritance, 1-3
.class files, 2-4, 2-12, 2-13
Class interface
forName method, 2-22
class schema object, 2-12, 2-13, 11-1, 11-2
ClassForName
lookupClass method, 2-23, 2-25
classForNameAndSchema method, 2-24
ClassNotFoundException, 2-22
CLASSPATH, 2-3, 2-22
client
install JDK, 4-2
set up environment variables, 4-2
setup, 4-2
CodeSource class, 10-4
equals method, 10-4
implies method, 10-4
compiling, 1-18, 2-5
error messages, 2-6, 11-4
options, 2-6, 11-4
run time, 2-5, 2-6
configuration, 4-1
Index-1
JVM, 4-2
performance, 9-4
connection
security, 10-1
constructor methods, 6-14
context
run-time, 5-1
stored procedures, 5-1
CREATE JAVA statement, 5-5
D
data confidentiality, 10-1
data types
mapping, 6-3
database
privileges, 10-2
schema plan, 8-4
trigger, 7-4
triggers, 5-2
database triggers
calling Java, 7-4
DBA_JAVA_POLICY view, 10-4, 10-13, 10-14
DBMS_JAVA package, 4-2, 7-2
compile_class, A-12
compile_method, A-13
delete_permission method, 10-13, A-6
derivedFrom method, A-2
disable_output_to_file, A-11
disable_output_to_java, A-10
disable_output_to_sql, A-9
disable_output_to_trc, A-11
disable_permission method, 10-13, A-6
dropjava method, A-5
enable_output_to_file, A-10
enable_output_to_java, A-10
enable_output_to_sql, A-8
enable_output_to_trc, A-11
enable_permission method, 10-13, A-6
endsession, A-11
endsession_and_related_state, A-12
export_class method, A-4
export_resource method, A-4
export_source method, A-4
fixed_in_instance method, A-3
get property, A-7
get_compiler_option method, A-1
grant_permission method, 10-6, A-5
grant_policy_permission method, 10-8, 10-10,
10-14, A-5
loadjava method, A-4
longname method, 2-18, 2-22, A-1
modifying permissions, 10-13
modifying PolicyTable permissions, 10-6, 10-8
query_output_to_file, A-11
query_output_to_sql, A-9
query_output_to_trc, A-11
remove property, A-7
remove_output_to_file, A-10
remove_output_to_java, A-9
Index-2
remove_output_to_sql, A-8
reset_compiler_option method, A-2
resolver method, A-2
restart_debugging method, A-4
restrict_permission method, 10-6, A-5
revoke_permission method, 10-13, A-6
runjava, A-6
runjava_in_current_session, A-7
set property, A-7
set_compiler_option method, A-1
set_native_compiler_option, A-12
set_output method, A-3
set_output_to_file, A-10
set_output_to_java, A-9
set_output_to_sql, A-8
set_preference method, A-6
setting permissions, 10-4
shortname method, 2-19, 2-22, A-1
show property, A-8
start_debugging method, A-3
stop_debugging method, A-4
uncompile_class, A-12, A-13
uncompile_method, A-13
unset_native_compiler_option, A-12
DBMS_JAVA query_output_to_java, A-10
DBMS_OUTPUT package, A-3
DbmsJava class seeDBMS_JAVA package
DbmsObjectInputStream class, 2-25
DbmsObjectOutputStream class, 2-25
deadlock, 2-32
DeadlockError exception, 2-32
debug
compiler option, 2-7, 11-4
stored procedures, 5-7
debugging
Java applications, 3-13
permissions, 10-17
definer rights, 2-16
delete method, 10-13
delete_permission method, A-6
derivedFrom method, A-2
DETERMINISTIC hint, 6-7
digest table, 11-3
disable method, 10-13
disable_permission method, A-6
dropjava method, A-5
dropjava tool, 2-13, 11-16
E
ease of use, 5-3
echo command, 11-24
enable method, 10-13
enable_permission method, A-6
encapsulation, 1-3
encoding
compiler option, 2-7, 11-4
end-of-call Migration, 2-35
EndOfCallRegistry class, 2-35
registerCallback method, 2-36
entity-relationship (ER) diagram, 8-1
drawing, 8-1
example, 8-3
equals method, 10-4
errors
compilation, 2-6
exception
ClassNotFoundException, 2-22
DeadlockError, 2-32
how Oracle JVM handles, 7-10
LimboError, 2-32
exit command, 11-25
exitCall method, 2-32
export_class method, A-4
export_resource method, A-4
export_source method, A-4
F
file names
dropjava tool, 11-18
loadjava tool, 11-11
FilePermission, 10-4, 10-5, 10-8, 10-13, 10-16
files, 2-27
lifetime, 2-39
finalizers, 2-28
fixed_in_instance method, A-3
footprint, 1-12, 2-2
foreign key, 8-4
forName method, 2-22
full name, Java, 2-5
functions, 5-2
G
garbage collection, 2-3
managing resources, 2-26
misuse, 2-27
garbage collectoion
purpose, 2-27
get_compiler_option method, 2-7, A-1
getCallerClass method, 2-24
getClassLoader method, 2-24
getProperty method, 3-14
grant method, 10-6
grant_permission method, 10-6, A-5
grant_policy_permission method, 10-8, 10-14, A-5
granting permissions, 10-4
grantPolicyPermission method, 10-8
graphical user interface see GUI
GUI, 1-16, 2-21
H
help command,
11-25
I
implies method, 10-4
inheritance, 1-3, 1-4
installation, 4-1
integrated development environment (IDE),
integrity, 10-1
interface, 1-3
internal JDBC driver, 1-18
interoperability, 5-4
interpreter, 1-18
IOException, 2-39
1-16
J
J2SE
install, 4-2
Java
applications, 2-1, 2-12
attributes, 1-2
calling from database triggers, 7-4
calling from PL/SQL, 7-8
calling from SQL DML, 7-7
calling from the top level, 7-1
calling restrictions, 7-8
checking loaded classes, 2-18
classes, 1-2
client setup, 4-2
compiling, 2-5
development environment, 2-3
development tools, 1-22
execution control, 2-3
execution in database, 5-1
execution rights, 2-15
full name, 2-5
in the database, 1-8, 2-1
invoking, 3-1
key features, 1-5
loading applications, 2-12
loading classes, 2-3
methods, 1-2
overview, 1-1
polymorphism, 1-4
publishing, 2-3, 6-1
resolving classes, 2-9
short name, 2-5
stored procedures see stored procedures
Java audit
object level, 2-20
statement level, 2-20
java command, 11-25
Java Compatibility Kit see JCK
Java Database Connectivity see JDBC
Java Development Kit see JDK
.java files, 2-4, 2-12, 2-13
java interpreter, 2-3
Java Language Specification seeJLS
Java Naming and Directory Interface see JNDI
Java Native Interface seeJNI
Java stored procedures see stored procedures
Java virtual machine see JVM
JAVA$OPTIONS table, 2-6
JAVA_ADMIN
granting permission, 10-2, 10-3, 10-8, 10-14
JAVA_ADMIN example, 10-9
Index-3
JAVA_ADMIN role
assigned permissions, 10-15
JAVA_MAX_SESSIONSPACE_SIZE parameter, 9-5
JAVA_POOL_SIZE parameter, 9-4
default, 4-2
JAVA_SOFT_SESSIONSPACE_LIMIT
parameter, 9-5
Java2
security, 10-2
Java2 Platform, Standard Edition see J2SE
JAVADEBUGPRIV role, 10-16, 10-17
JAVASYSPRIV role, 10-2, 10-16, 10-17
JAVAUSERPRIV role, 10-2, 10-16, 10-17
JCK, 1-7
JDBC, 1-6
accessing SQL, 1-21
defined, 3-3
driver, 1-17
driver types, 1-21, 3-4
drivers, 1-21
example, 3-5
security, 10-1
server-side internal driver, 1-18
JDeveloper
development environment, 1-22
JDK
install, 4-2
JLS, 1-2, 1-7
JNDI, 1-6
JNI
support, 3-3
JPublisher
overview, 12-6
JServerPermission, 10-14, 10-15, 10-16, 10-17
JVM, 1-6
bytecode, 1-6
configure, 4-1
defined, 1-1
garbage collection, 1-10
install, 4-1
multithreading, 1-10
responsibilities, 2-2
necessary privileges and permission, 2-14
reloading classes, 2-15
restrictions, 2-14
loadjava method, A-4
loadjava tool, 2-12 to 2-14, 11-6 to 11-16
compiling source, 2-6, 9-8
example, 3-2, 5-6
execution rights, 2-15, 10-2
loading class, 2-12
resolution modes, 11-3
using memory, 9-4
logging, 2-6
longname method, 2-18, 2-22, A-1
lookupClass method, 2-25
M
main method, 1-16, 2-3
maintainability, 5-4
map methods, 6-14
memory
across calls, 2-28
call, 2-3
Java pool, 9-6
leaks, 2-28
lifetime, 2-27, 2-39
performance configuration, 9-4
session, 2-3
methods, 1-2, 5-2, 6-12
constructor, 6-14
declaring, 6-13
map and order, 6-14
object-relational, 5-2
missing classes, 11-9
modes
parameter, 6-3
multiple inheritance, 1-3
multithreading, 1-10
N
key
foreign, 8-4
primary, 8-4
NAME clause, 6-7
namespace, 11-19
native compilation
methods, 1-13
performance, 1-12
native Java interface, 3-10
NetPermission, 10-13, 10-15
L
O
library manager, 1-18
LimboError exception, 2-32
loader, class, 1-18
loading, 2-12
checking results, 2-13, 2-18
class, 1-14, 2-3, 2-5, 2-12
compilation option, 2-5
granting execution, 2-15
JAR or ZIP Files, 2-14
object, 1-2
full to short name conversion, 2-18
lifetime, 2-39
schema, 2-3
serialization, 2-25
SQL type, 5-2
table, 6-15
writing call specifications, 6-12
ObjectInputStream class, 2-25
ObjectOutputStream class, 2-25
K
Index-4
object-relational methods, 5-2
ojvmjava tool, 11-19 to 11-27
online
compiler option, 2-7, 11-4
operating system
resources, 2-26
operating system resources
access, 2-27
across calls, 2-40
closing, 2-28
garbage collection, 2-27
lifetime, 2-27
managing, 2-26
overview, 2-27
performance, 9-4
Oracle JVM
class loader, 1-18
compiler, 1-18
configuration requirements, 4-2
interpreter, 1-18
JDBC internal driver, 1-18
library manager, 1-18
main components, 1-16
SQLJ translator, 1-19
verifier, 1-18
Oracle Net Services Connection Manager, 1-9
OracleRuntime class
exitCall method, 2-32, 2-33
getCallerClass method, 2-24
getClassLoader method, 2-24
order methods, 6-14
output
redirecting, 3-14, 7-2
P
package DBMS_JAVA, 4-2, 7-2
packaged call specifications, writing, 6-10
PARALLEL_ENABLE option, 6-7
parameter modes, 6-3
performance, 5-3, 9-1
native compilation, 1-12
permission
Oracle-specific, 10-14
types, 10-13
Permission class, 10-4, 10-5, 10-9, 10-13
permissions, 10-1 to 10-18
administrating, 10-8
assigning, 10-3, 10-4
creating, 10-9
debugging, 10-17
deleting, 10-13
disabling, 10-12
enabling, 10-12
granting, 10-4, 10-6
granting policy, 10-8
granting, example, 10-6
grouped into roles, 10-17
JAVA_ADMIN role, 10-15
JAVADEBUGPRIV role, 10-16
JAVASYSPRIV role, 10-16
JAVAUSERPRIV role, 10-16
limiting, 10-4, 10-6
limiting, example, 10-7
PUBLIC, 10-15
restricting, 10-4, 10-6
restricting, example, 10-7
specifying policy, 10-3
SYS permission, 10-15
types, 10-13
PL/SQL
calling Java from, 7-8
packages, 6-10
policy table
managing, 10-8
modifying, 10-4
setting permissions, 10-4
viewing, 10-4
PolicyTable class
specifying policy, 10-3
updating, 10-3, 10-10
PolicyTableManager class
delete method, 10-13
disable method, 10-13
enable method, 10-13
PolicyTablePermission, 10-4, 10-8, 10-14, 10-15
polymorphism, 1-4
primary key, 8-4
privileges
database, 10-2
procedures, 5-2
productivity, 5-3
.properties files, 2-4, 2-12, 2-13
PropertyPermission, 10-13, 10-15, 10-17
PUBLIC permissions, 10-15
publishing, 2-3, 2-5, 2-19
example, 3-2, 5-6
R
redirecting output, 3-14, 7-2
REF, 6-15
ReflectPermission, 10-13, 10-15
registerCallback method, 2-36
replication, 5-4
reset_compiler_option method, 2-7, A-2
resolver, 2-9 to 2-12, 11-2
default, 2-10
defined, 2-3, 2-5, 2-22
example, 3-2, 5-6
ignoring non-existent references, 2-10, 2-11
resolver method, A-2
resolver specification
definition, 2-9
resource schema object, 2-12, 2-13, 11-1
restart_debugging method, A-4
restrict method, 10-6
restrict_permission method, 10-6, 10-7, A-5
revoke method, 10-13
revoke_permission method, 10-13, A-6
Index-5
row trigger, 7-4
run-time contexts, stored procedures, 5-1
RuntimePermission, 10-13, 10-15, 10-16
S
scalability, 5-4
scavenging, 1-11
security, 5-4
SecurityPermission, 10-13, 10-15
.ser files, 2-4, 2-12, 2-13
SerializablePermission, 10-13, 10-16
session, 1-15
namespace, 11-19
session memory, 2-3
set_compiler_option method, 2-7, A-1
set_output method, A-3
set_preference method, A-6
SHARED_POOL_SIZE parameter, 9-4
default, 4-2
shell commands, 11-24
short name, Java, 2-5
shortname method, A-1
single inheritance, 1-4
SocketPermission, 10-13, 10-16
source schema object, 2-12, 2-13, 11-1
SQLJ
server-side translator, 1-19
tarnslator, 1-19
.sqlj files, 2-4, 2-12, 2-13
start_debugging method, A-3
statement trigger, 7-4
stop_debugging method, A-4
stored procedures
advantages, 5-3
calling, 7-1
defined, 1-20
developing, 5-1, 8-1
example, 8-1
introduction, 5-1
invoking, 3-1
publishing, 6-1
steps, 5-5
T
threading
model, 1-10, 2-32
threads
across calls, 2-42
life cycle, 2-32
Oracle JVM, 2-27
threading in Oracle Database, 2-32
top-level call specifications, writing, 6-6
triggers
calling Java from, 7-4
database, 5-2, 7-4
row, 7-4
statement, 7-4
using Java stored procedures, 3-1, 5-5
Index-6
U
user interface, 2-21
USER_ERRORS, 2-6
USER_JAVA_POLICY view, 10-4, 10-13, 10-14
USER_OBJECTS, 2-13, 2-18, A-1
accessing, example, 2-19
V
V$SGASTAT table, 9-7
variables
static, 2-3
verifier, 1-18
version
retrieving, 3-14
version command, 11-26
W
Web services
call-ins to database, 12-2
call-outs from database, 12-4, 12-5
JPublisher support for call-ins, 12-3
Oracle Database features, 12-2, 12-6
overview, 12-1
service consumer, 12-3
service provider, 12-1
using JPublisher for call-ins, 12-2
working directions, 12-1
whoami command, 11-26
Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Download PDF

advertising