Java example source code file (RedefineAgent.java)

This example Java source code file (RedefineAgent.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

class, classdefinition, classfiletransformer, error, exception, inetsocketaddress, instrumentation, net, network, protectiondomain, redefineagent, redefinedummy, security, socket, string, test, util

The RedefineAgent.java Java example source code

/*
 * Copyright (c) 2006, 2013, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

/*
 *
 *
 * @bug 6439234 6446941
 *
 * Test attach used in concert with transformers and redefineClasses.
 *
 * 6439234 java.lang.instrument: 8 JCK JPLIS tests fail when running in Live phase (no transform events)
 * 6446941 java.lang.instrument: multiple agent attach fails (first agent chooses capabilities)
 */
import java.net.Socket;
import java.net.InetSocketAddress;
import java.io.IOException;
import java.util.Arrays;
import java.security.ProtectionDomain;
import java.lang.instrument.ClassFileTransformer;
import java.lang.instrument.Instrumentation;
import java.lang.instrument.ClassDefinition;

public class RedefineAgent implements ClassFileTransformer {

    static byte[] classfilebytes;
    static final String targetName = "RedefineDummy";
    static final String targetNameSlashes = "RedefineDummy";
    static boolean gotRedefineTransform = false;

    // test transform and capture class bytes for redefine
    public byte[] transform(ClassLoader loader,
                            String className,
                            Class<?> classBeingRedefined,
                            ProtectionDomain  protectionDomain,
                            byte[] classfileBuffer) {
        if (className.equals(targetNameSlashes)) {
            if (classBeingRedefined == null) {
                System.out.println("Got bytes for: " + className);
                classfilebytes = Arrays.copyOf(classfileBuffer, classfileBuffer.length);
            } else {
                gotRedefineTransform = true;
            }
        }
        return null;
    }

    // test transform and redefine for an attached agent
    public static void testRedefine(Instrumentation inst) throws Exception {
        Class[] classes = inst.getAllLoadedClasses();
        for (Class k : classes) {
            if (k.getName().equals(targetName)) {
                throw new Exception("RedefineAgent Test error: class " + targetName + " has already been loaded.");
            }
        }
        inst.addTransformer(new RedefineAgent());
        ClassLoader.getSystemClassLoader().loadClass(targetName);
        classes = inst.getAllLoadedClasses();
        Class targetClass = null;
        for (Class k : classes) {
            if (k.getName().equals(targetName)) {
                targetClass = k;
                break;
            }
        }
        if (targetClass == null) {
            throw new Exception("RedefineAgent Test error: class " + targetName + " not loaded.");
        }
        if (classfilebytes == null) {
            throw new Exception("RedefineAgent Error(6439234): no transform call for class " + targetName);
        }
        ClassDefinition cd = new ClassDefinition(targetClass, classfilebytes);
        inst.redefineClasses(cd);
        System.out.println("RedefineAgent did redefine.");
        if (gotRedefineTransform) {
            System.out.println("RedefineAgent got redefine transform.");
        } else {
            throw new Exception("RedefineAgent Error(6439234): no transform call for redefine " + targetName);
        }
    }

    public static void agentmain(String args, Instrumentation inst) throws Exception {
        System.out.println("RedefineAgent running...");
        System.out.println("RedefineAgent redefine supported: " + inst.isRedefineClassesSupported());
        int port = Integer.parseInt(args);
        System.out.println("RedefineAgent connecting back to Tool....");
        Socket s = new Socket();
        s.connect( new InetSocketAddress(port) );
        System.out.println("RedefineAgent connected to Tool.");

        testRedefine(inst);

        s.close();
    }

}