/* * Javassist, a Java-bytecode translator toolkit. * Copyright (C) 1999-2004 Shigeru Chiba. All Rights Reserved. * * The contents of this file are subject to the Mozilla Public License Version * 1.1 (the "License"); you may not use this file except in compliance with * the License. Alternatively, the contents of this file may be used under * the terms of the GNU Lesser General Public License Version 2.1 or later. * * 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. */ package javassist.reflect; import javassist.CannotCompileException; import javassist.NotFoundException; import javassist.ClassPool; /** * A class loader for reflection. * *
To run a program, say MyApp
,
* including a reflective class,
* you must write a start-up program as follows:
*
*
* public class Main { * public static void main(String[] args) throws Throwable { * javassist.reflect.Loader cl * = (javassist.reflect.Loader)Main.class.getClassLoader(); * cl.makeReflective("Person", "MyMetaobject", * "javassist.reflect.ClassMetaobject"); * cl.run("MyApp", args); * } * } ** *
Then run this program as follows: * *
% java javassist.reflect.Loader Main arg1, ...* *
This command runs Main.main()
with arg1
, ...
* and Main.main()
runs MyApp.main()
with
* arg1
, ...
* The Person
class is modified
* to be a reflective class. Method calls on a Person
* object are intercepted by an instance of MyMetaobject
.
*
*
Also, you can run MyApp
in a slightly different way:
*
*
* public class Main2 { * public static void main(String[] args) throws Throwable { * javassist.reflect.Loader cl = new javassist.reflect.Loader(); * cl.makeReflective("Person", "MyMetaobject", * "javassist.reflect.ClassMetaobject"); * cl.run("MyApp", args); * } * } ** *
This program is run as follows: * *
% java Main2 arg1, ...* *
The difference from the former one is that the class Main
* is loaded by javassist.reflect.Loader
whereas the class
* Main2
is not. Thus, Main
belongs
* to the same name space (security domain) as MyApp
* whereas Main2
does not; Main2
belongs
* to the same name space as javassist.reflect.Loader
.
* For more details,
* see the notes in the manual page of javassist.Loader
.
*
*
The class Main2
is equivalent to this class:
*
*
* public class Main3 { * public static void main(String[] args) throws Throwable { * Reflection reflection = new Reflection(); * javassist.Loader cl * = new javassist.Loader(ClassPool.getDefault(reflection)); * reflection.makeReflective("Person", "MyMetaobject", * "javassist.reflect.ClassMetaobject"); * cl.run("MyApp", args); * } * } ** *
Note: * *
javassist.reflect.Loader
does not make a class reflective
* if that class is in a java.*
or
* javax.*
pacakge because of the specifications
* on the class loading algorithm of Java. The JVM does not allow to
* load such a system class with a user class loader.
*
*
To avoid this limitation, those classes should be statically
* modified with javassist.reflect.Compiler
and the original
* class files should be replaced.
*
* @see javassist.reflect.Reflection
* @see javassist.reflect.Compiler
* @see javassist.Loader
*/
public class Loader extends javassist.Loader {
protected Reflection reflection;
/**
* Loads a class with an instance of Loader
* and calls main()
in that class.
*
* @param args command line parameters.
*
args[0]
is the class name to be loaded.
* args[1..n]
are parameters passed
* to the target main()
.
* Metaobject
.
* @param metaclass the class of the class metaobject.
* It must be a subclass of
* ClassMetaobject
.
* @return false
if the class is already reflective.
*
* @see javassist.reflect.Metaobject
* @see javassist.reflect.ClassMetaobject
*/
public boolean makeReflective(String clazz,
String metaobject, String metaclass)
throws CannotCompileException, NotFoundException
{
return reflection.makeReflective(clazz, metaobject, metaclass);
}
}