org.springsource.loaded.agent.ClassVisitingConstructorAppender Maven / Gradle / Ivy
/*
* Copyright 2010-2012 VMware and contributors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springsource.loaded.agent;
import org.objectweb.asm.ClassVisitor;
import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.MethodVisitor;
import org.springsource.loaded.Constants;
/**
*
* @author Andy Clement
* @since 0.5.0
*/
public class ClassVisitingConstructorAppender extends ClassVisitor implements Constants {
private String calleeOwner;
private String calleeName;
/**
* This ClassAdapter will visit a class and within the constructors it will add a call to the specified method (assumed static)
* just before each constructor returns. The target of the call should be a collecting method that will likely do something with
* the instances later on class reload.
*
* @param owner the owning class of the method to call
* @param name the method to call
*/
public ClassVisitingConstructorAppender(String owner, String name) {
super(ASM5,new ClassWriter(0)); // TODO review 0 here
this.calleeOwner = owner;
this.calleeName = name;
}
public byte[] getBytes() {
return ((ClassWriter) cv).toByteArray();
}
public MethodVisitor visitMethod(int access, String name, String desc, String signature, String[] exceptions) {
if (name.equals("")) {
MethodVisitor mv = super.visitMethod(access, name, desc, signature, exceptions);
return new ConstructorAppender(mv);
} else {
return super.visitMethod(access, name, desc, signature, exceptions);
}
}
/**
* This constructor appender includes a couple of instructions at the end of each constructor it is asked to visit. It
* recognizes the end by observing a RETURN instruction. The instructions are inserted just before the RETURN.
*/
class ConstructorAppender extends MethodVisitor implements Constants {
public ConstructorAppender(MethodVisitor mv) {
super(ASM5,mv);
}
@Override
public void visitInsn(int opcode) {
if (opcode == RETURN) {
mv.visitVarInsn(ALOAD, 0);
mv.visitMethodInsn(INVOKESTATIC, calleeOwner, calleeName, "(Ljava/lang/Object;)V");
}
super.visitInsn(opcode);
}
}
}