aoqi@0: /*
aoqi@0:  * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.
aoqi@0:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
aoqi@0:  *
aoqi@0:  * This code is free software; you can redistribute it and/or modify it
aoqi@0:  * under the terms of the GNU General Public License version 2 only, as
aoqi@0:  * published by the Free Software Foundation.
aoqi@0:  *
aoqi@0:  * This code is distributed in the hope that it will be useful, but WITHOUT
aoqi@0:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
aoqi@0:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
aoqi@0:  * version 2 for more details (a copy is included in the LICENSE file that
aoqi@0:  * accompanied this code).
aoqi@0:  *
aoqi@0:  * You should have received a copy of the GNU General Public License version
aoqi@0:  * 2 along with this work; if not, write to the Free Software Foundation,
aoqi@0:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
aoqi@0:  *
aoqi@0:  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
aoqi@0:  * or visit www.oracle.com if you need additional information or have any
aoqi@0:  * questions.
aoqi@0:  */
aoqi@0: import java.security.*;
aoqi@0: import java.lang.instrument.*;
aoqi@0: import java.lang.reflect.*;
aoqi@0: 
aoqi@0: public class Agent implements ClassFileTransformer {
aoqi@0:     public synchronized byte[] transform(final ClassLoader classLoader,
aoqi@0:                                          final String className,
aoqi@0:                                          Class<?> classBeingRedefined,
aoqi@0:                                          ProtectionDomain protectionDomain,
aoqi@0:                                          byte[] classfileBuffer) {
aoqi@0:         System.out.println("Transforming class " + className);
aoqi@0:         return classfileBuffer;
aoqi@0:     }
aoqi@0: 
aoqi@0:     public static void redefine(String agentArgs, Instrumentation instrumentation, Class to_redefine) {
aoqi@0: 
aoqi@0:         try {
aoqi@0:             instrumentation.retransformClasses(to_redefine);
aoqi@0:         } catch (Exception e) {
aoqi@0:             e.printStackTrace();
aoqi@0:         }
aoqi@0: 
aoqi@0:     }
aoqi@0: 
aoqi@0:     public static void premain(String agentArgs, Instrumentation instrumentation) {
aoqi@0:         Agent transformer = new Agent();
aoqi@0:         instrumentation.addTransformer(transformer, true);
aoqi@0: 
aoqi@0:         // Redefine java/lang/Object and java/lang/reflect/Method.invoke and
aoqi@0:         // java/lang/ClassLoader
aoqi@0:         Class object_class = Object.class;
aoqi@0:         redefine(agentArgs, instrumentation, object_class);
aoqi@0: 
aoqi@0:         Class method_class = Method.class;
aoqi@0:         redefine(agentArgs, instrumentation, method_class);
aoqi@0: 
aoqi@0:         Class loader_class = ClassLoader.class;
aoqi@0:         redefine(agentArgs, instrumentation, loader_class);
aoqi@0: 
aoqi@0:         instrumentation.removeTransformer(transformer);
aoqi@0:     }
aoqi@0: 
aoqi@0:     public static void main(String[] args) {
aoqi@0:         byte[] ba = new byte[0];
aoqi@0: 
aoqi@0:         // If it survives 1000 GC's, it's good.
aoqi@0:         for (int i = 0; i < 1000 ; i++) {
aoqi@0:             System.gc();
aoqi@0:             ba.clone();
aoqi@0:         }
aoqi@0:         try {
aoqi@0:             // Use java/lang/reflect/Method.invoke to call
aoqi@0:             WalkThroughInvoke a = new WalkThroughInvoke();
aoqi@0:             Class aclass = WalkThroughInvoke.class;
aoqi@0:             Method m = aclass.getMethod("stackWalk");
aoqi@0:             m.invoke(a);
aoqi@0:         } catch (Exception x) {
aoqi@0:             x.printStackTrace();
aoqi@0:         }
aoqi@0:     }
aoqi@0: }