Javassist version 3

Copyright (C) 1999-2010 by Shigeru Chiba, All rights reserved.


Javassist (JAVA programming ASSISTant) makes Java bytecode manipulation simple. It is a class library for editing bytecodes in Java; it enables Java programs to define a new class at runtime and to modify a class file when the JVM loads it. Unlike other similar bytecode editors, Javassist provides two levels of API: source level and bytecode level. If the users use the source-level API, they can edit a class file without knowledge of the specifications of the Java bytecode. The whole API is designed with only the vocabulary of the Java language. You can even specify inserted bytecode in the form of source text; Javassist compiles it on the fly. On the other hand, the bytecode-level API allows the users to directly edit a class file as other editors.


Files


How to run sample programs

JDK 1.4 or later is needed.

0. If you have Apache Ant

Run the sample-all task. Otherwise, follow the instructions below.

1. Move to the directory where this Readme.html file is located.

In the following instructions, we assume that the javassist.jar file is included in the class path. For example, the javac and java commands must receive the following classpath option:

If the operating system is Windows, the path separator must be not : (colon) but ; (semicolon). The java command can receive the -cp option as well as -classpath.

If you don't want to use the class-path option, you can make javassist.jar included in the CLASSPATH environment:

or if the operating system is Windows:

Otherwise, you can copy javassist.jar to the directory

<java-home> depends on the system. It is usually /usr/local/java, c:\j2sdk1.4\, etc.

2. sample/Test.java

This is a very simple program using Javassist.

To run, type the commands:

For more details, see sample/Test.java

3. sample/reflect/*.java

This is the "verbose metaobject" example well known in reflective programming. This program dynamically attaches a metaobject to a Person object. The metaobject prints a message if a method is called on the Person object.

To run, type the commands:

Compare this result with that of the regular execution without reflection:

For more details, see sample/reflect/Main.java

Furthermore, the Person class can be statically modified so that all the Person objects become reflective without sample.reflect.Main. To do this, type the commands:

Then,

4. sample/duplicate/*.java

This is another example of reflective programming.

To run, type the commands:

Compare this result with that of the regular execution without reflection:

For more details, see sample/duplicate/Main.java

5. sample/vector/*.java

This example shows the use of Javassit for producing a class representing a vector of a given type at compile time.

To run, type the commands:

Note: javassist.jar is unnecessary to compile and execute sample/vector/Test.java. For more details, see sample/vector/Test.j and sample/vector/VectorAssistant.java

6. sample/rmi/*.java

This demonstrates the javassist.rmi package.

To run, type the commands:

The second line starts a web server listening to port 5001.

Then, open sample/rmi/webdemo.html with a web browser running on the local host. (webdemo.html trys to fetch an applet from http://localhost:5001/, which is the web server we started above.)

Otherwise, run sample.rmi.CountApplet as an application:

7. sample/evolve/*.java

This is a demonstration of the class evolution mechanism implemented with Javassist. This mechanism enables a Java program to reload an existing class file under some restriction.

To run, type the commands:

The second line starts a class loader DemoLoader, which runs a web server DemoServer listening to port 5003.

Then, open http://localhost:5003/demo.html with a web browser running on the local host. (Or, see sample/evolve/start.html.)

8. sample/hotswap/*.java

This shows dynamic class reloading by the JPDA. It needs JDK 1.4 or later. To run, first type the following commands:

If your Java is 1.4, then type:

If you are using Java 5, then type:

Note that the class path must include JAVA_HOME/lib/tools.jar.

Hints

To know the version number, type this command:

Javassist provides a class file viewer for debugging. For more details, see javassist.Dump.


Changes

-version 3.14 on October 5, 2010

-version 3.13 on July 19, 2010

-version 3.12.1 on June 10, 2010

-version 3.12 on April 16, 2010

-version 3.11 on July 3, 2009

-version 3.10 on March 5, 2009

-version 3.9 on October 9, 2008

-version 3.8.1 on July 17, 2008

-version 3.8.0 on June 13, 2008

-version 3.7.1 on March 10, 2008

-version 3.7 on January 20, 2008

-version 3.6.0 on September 13, 2007

-version 3.6.0.CR1 on July 27, 2007

-version 3.5 on April 29, 2007

-version 3.4 on November 17, 2006

-version 3.3 on August 17, 2006

-version 3.2 on June 21, 2006

- version 3.2.0.CR2 on May 9, 2006

- version 3.2.0.CR1 on March 18, 2006

- version 3.1 on February 23, 2006

- version 3.1 RC2 on September 7, 2005

- version 3.1 RC1 on August 29, 2005

- version 3.0 on January 18, 2005

- version 3.0 RC1 on September 13, 2004.

- version 3.0 beta on May 18th, 2004.

- version 2.6 in August, 2003.

- version 2.5.1 in May, 2003.
Simple changes for integration with JBoss AOP

- version 2.5 in May, 2003.
From this version, Javassist is part of the JBoss project.

- version 2.4 in February, 2003.

- version 2.3 in December, 2002.

- version 2.2 in October, 2002.

- version 2.1 in July, 2002.

- version 2.0 (major update) in November, 2001.

version 1.0 in July, 2001.

- version 0.8

- version 0.7

- version 0.6

- version 0.5

- version 0.4

- version 0.3

- version 0.2

-version 0.1 on April 16, 1999.


Bug reports etc.

Bug reports:
Post your reports at Forums or directly send an email to:
  chiba@acm.org or chiba@is.titech.ac.jp

The home page of Javassist:
Visit www.javassist.org and www.jboss.org


Copyright notices

Javassist, a Java-bytecode translator toolkit.
Copyright (C) 1999-2010 Shigeru Chiba. All Rights Reserved.

The contents of this software, Javassist, are subject to the Mozilla Public License Version 1.1 (the "License");
you may not use this software except in compliance with the License. You may obtain a copy of the License at
http://www.mozilla.org/MPL/

Software distributed under the License is distributed on an "AS IS" basis, WITHOUT WARRANTY OF
ANY KIND, either express or implied. See the License for the specific language governing rights and
limitations under the License.

The Original Code is Javassist.

The Initial Developer of the Original Code is Shigeru Chiba. Portions created by the Initial Developer are
  Copyright (C) 1999-2010 Shigeru Chiba. All Rights Reserved.

Contributor(s): ______________________________________.

Alternatively, the contents of this software may be used under the terms of the GNU Lesser General Public License Version 2.1 or later (the "LGPL"), in which case the provisions of the LGPL are applicable instead of those above. If you wish to allow use of your version of this software only under the terms of the LGPL, and not to allow others to use your version of this software under the terms of the MPL, indicate your decision by deleting the provisions above and replace them with the notice and other provisions required by the LGPL. If you do not delete the provisions above, a recipient may use your version of this software under the terms of either the MPL or the LGPL.

If you obtain this software as part of JBoss, the contents of this software may be used under only the terms of the LGPL. To use them under the MPL, you must obtain a separate package including only Javassist but not the other part of JBoss.

All the contributors to the original source tree must agree to the original license term described above.


Acknowledgments

The development of this software is sponsored in part by the PRESTO and CREST programs of Japan Science and Technology Corporation.

I'd like to thank Michiaki Tatsubori, Johan Cloetens, Philip Tomlinson, Alex Villazon, Pascal Rapicault, Dan HE, Eric Tanter, Michael Haupt, Toshiyuki Sasaki, Renaud Pawlak, Luc Bourlier, Eric Bui, Lewis Stiller, Susumu Yamazaki, Rodrigo Teruo Tomita, Marc Segura-Devillechaise, Jan Baudisch, Julien Blass, Yoshiki Sato, Fabian Crabus, Bo Norregaard Jorgensen, Bob Lee, Bill Burke, Remy Sanlaville, Muga Nishizawa, Alexey Loubyansky, Saori Oki, Andreas Salathe, Dante Torres estrada, S. Pam, Nuno Santos, Denis Taye, Colin Sampaleanu, Robert Bialek, Asato Shimotaki, Howard Lewis Ship, Richard Jones, Marjan Sterjev, Bruce McDonald, Mark Brennan, Vlad Skarzhevskyy, Brett Randall, Tsuyoshi Murakami, Nathan Meyers, Yoshiyuki Usui Yutaka Sunaga, Arjan van der Meer, Bruce Eckel, Guillaume Pothier, Kumar Matcha, Andreas Salathe, Renat Zubairov, Armin Haaf, Emmanuel Bernard and all other contributors for their contributions.



Shigeru Chiba (Email: chiba@acm.org)
Dept. of Math. and Computing Sciences, Tokyo Institute of Technology