/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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.apache.s4.util;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.Random;
import org.apache.bcel.Constants;
import org.apache.bcel.classfile.JavaClass;
import org.apache.bcel.generic.BranchInstruction;
import org.apache.bcel.generic.ClassGen;
import org.apache.bcel.generic.ConstantPoolGen;
import org.apache.bcel.generic.INSTANCEOF;
import org.apache.bcel.generic.InstructionConstants;
import org.apache.bcel.generic.InstructionFactory;
import org.apache.bcel.generic.InstructionHandle;
import org.apache.bcel.generic.InstructionList;
import org.apache.bcel.generic.MethodGen;
import org.apache.bcel.generic.ObjectType;
import org.apache.bcel.generic.PUSH;
import org.apache.bcel.generic.Type;
public class ClonerGenerator {
public Class generate(Class clazz) {
String className = clazz.getName();
Random rand = new Random(System.currentTimeMillis());
String clonerClassname = "Cloner" + (Math.abs(rand.nextInt() % 3256));
ClassGen cg = new ClassGen(clonerClassname,
"java.lang.Object",
clonerClassname + ".java",
Constants.ACC_PUBLIC | Constants.ACC_SUPER,
new String[] { "org.apache.s4.util.Cloner" });
ConstantPoolGen cp = cg.getConstantPool();
InstructionFactory instFactory = new InstructionFactory(cg, cp);
InstructionList il = new InstructionList();
// build constructor method for new class
MethodGen constructor = new MethodGen(Constants.ACC_PUBLIC,
Type.VOID,
Type.NO_ARGS,
new String[] {},
"<init>",
clonerClassname,
il,
cp);
il.append(InstructionFactory.createLoad(Type.OBJECT, 0));
il.append(instFactory.createInvoke("java.lang.Object",
"<init>",
Type.VOID,
Type.NO_ARGS,
Constants.INVOKESPECIAL));
il.append(InstructionFactory.createReturn(Type.VOID));
constructor.setMaxStack();
constructor.setMaxLocals();
cg.addMethod(constructor.getMethod());
il.dispose();
// build clone method
il = new InstructionList();
MethodGen method = new MethodGen(Constants.ACC_PUBLIC,
Type.OBJECT,
new Type[] { Type.OBJECT },
new String[] { "arg0" },
"clone",
clonerClassname,
il,
cp);
il.append(InstructionConstants.ACONST_NULL);
il.append(InstructionFactory.createStore(Type.OBJECT, 2));
il.append(InstructionFactory.createLoad(Type.OBJECT, 1));
il.append(new INSTANCEOF(cp.addClass(new ObjectType(className))));
BranchInstruction ifeq_6 = InstructionFactory.createBranchInstruction(Constants.IFEQ,
null);
il.append(ifeq_6);
il.append(InstructionFactory.createLoad(Type.OBJECT, 1));
il.append(instFactory.createCheckCast(new ObjectType(className)));
il.append(InstructionFactory.createStore(Type.OBJECT, 2));
InstructionHandle ih_14 = il.append(InstructionFactory.createLoad(Type.OBJECT,
2));
il.append(new INSTANCEOF(cp.addClass(new ObjectType("java.lang.Cloneable"))));
BranchInstruction ifne_18 = InstructionFactory.createBranchInstruction(Constants.IFNE,
null);
il.append(ifne_18);
il.append(instFactory.createFieldAccess("java.lang.System",
"out",
new ObjectType("java.io.PrintStream"),
Constants.GETSTATIC));
il.append(new PUSH(cp, "Not cloneable!"));
il.append(instFactory.createInvoke("java.io.PrintStream",
"println",
Type.VOID,
new Type[] { Type.STRING },
Constants.INVOKEVIRTUAL));
il.append(InstructionConstants.ACONST_NULL);
il.append(InstructionFactory.createReturn(Type.OBJECT));
InstructionHandle ih_31 = il.append(InstructionFactory.createLoad(Type.OBJECT,
2));
il.append(instFactory.createInvoke(className,
"clone",
Type.OBJECT,
Type.NO_ARGS,
Constants.INVOKEVIRTUAL));
il.append(InstructionFactory.createReturn(Type.OBJECT));
ifeq_6.setTarget(ih_14);
ifne_18.setTarget(ih_31);
method.setMaxStack();
method.setMaxLocals();
cg.addMethod(method.getMethod());
il.dispose();
JavaClass jc = cg.getJavaClass();
ClonerClassLoader cl = new ClonerClassLoader();
return cl.loadClassFromBytes(clonerClassname, jc.getBytes());
}
public static class ClonerClassLoader extends URLClassLoader {
public ClonerClassLoader() {
super(new URL[] {});
}
public Class loadClassFromBytes(String name, byte[] bytes) {
try {
return this.loadClass(name);
} catch (ClassNotFoundException cnfe) {
// expected
}
return this.defineClass(name, bytes, 0, bytes.length);
}
}
}