scouter.javassist.tools.Callback Maven / Gradle / Ivy
/*
* Javassist, a Java-bytecode translator toolkit.
* Copyright (C) 1999- 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,
* or the Apache License Version 2.0.
*
* 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 scouter.javassist.tools;
import java.util.HashMap;
import java.util.UUID;
import scouter.javassist.CannotCompileException;
import scouter.javassist.CtBehavior;
/**
* Creates bytecode that when executed calls back to the instance's result method.
*
* Example of how to create and insert a callback:
*
* ctMethod.insertAfter(new Callback("Thread.currentThread()") {
* public void result(Object... objects) {
* Thread thread = (Thread) objects[0];
* // do something with thread...
* }
* }.sourceCode());
*
* Contains utility methods for inserts callbacks in CtBehaviour, example:
*
* insertAfter(ctBehaviour, new Callback("Thread.currentThread(), dummyString") {
* public void result(Object... objects) {
* Thread thread = (Thread) objects[0];
* // do something with thread...
* }
* });
*
*
* @author Marten Hedborg
*/
public abstract class Callback {
public static HashMap callbacks = new HashMap();
private final String sourceCode;
/**
* Constructs a new Callback object.
*
* @param src The source code representing the inserted callback bytecode.
* Can be one or many single statements each returning one object.
* If many single statements are used they must be comma separated.
*/
public Callback(String src){
String uuid = UUID.randomUUID().toString();
callbacks.put(uuid, this);
sourceCode = "((javassist.tools.Callback) javassist.tools.Callback.callbacks.get(\""+uuid+"\")).result(new Object[]{"+src+"});";
}
/**
* Gets called when bytecode is executed
*
* @param objects Objects that the bytecode in callback returns
*/
public abstract void result(Object... objects);
@Override
public String toString(){
return sourceCode();
}
public String sourceCode(){
return sourceCode;
}
/**
* Utility method to insert callback at the beginning of the body.
*
* @param callback The callback
*
* @see CtBehavior#insertBefore(String)
*/
public static void insertBefore(CtBehavior behavior, Callback callback)
throws CannotCompileException
{
behavior.insertBefore(callback.toString());
}
/**
* Utility method to inserts callback at the end of the body.
* The callback is inserted just before every return instruction.
* It is not executed when an exception is thrown.
*
* @param behavior The behaviour to insert callback in
* @param callback The callback
*
* @see CtBehavior#insertAfter(String, boolean)
*/
public static void insertAfter(CtBehavior behavior,Callback callback)
throws CannotCompileException
{
behavior.insertAfter(callback.toString(), false);
}
/**
* Utility method to inserts callback at the end of the body.
* The callback is inserted just before every return instruction.
* It is not executed when an exception is thrown.
*
* @param behavior The behaviour to insert callback in
* @param callback The callback representing the inserted.
* @param asFinally True if the inserted is executed
* Not only when the control normally returns
* but also when an exception is thrown.
* If this parameter is true, the inserted code cannot
* access local variables.
*
* @see CtBehavior#insertAfter(String, boolean)
*/
public static void insertAfter(CtBehavior behavior, Callback callback, boolean asFinally)
throws CannotCompileException
{
behavior.insertAfter(callback.toString(), asFinally);
}
/**
* Utility method to inserts callback at the specified line in the body.
*
* @param behavior The behaviour to insert callback in
* @param callback The callback representing.
* @param lineNum The line number. The callback is inserted at the
* beginning of the code at the line specified by this
* line number.
*
* @return The line number at which the callback has been inserted.
*
* @see CtBehavior#insertAt(int, String)
*/
public static int insertAt(CtBehavior behavior, Callback callback, int lineNum)
throws CannotCompileException
{
return behavior.insertAt(lineNum, callback.toString());
}
}