1 /*

     2  * Copyright (c) 2013, 2014, Oracle and/or its affiliates. All rights reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.

     8  *

     9  * This code is distributed in the hope that it will be useful, but WITHOUT

    10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    12  * version 2 for more details (a copy is included in the LICENSE file that

    13  * accompanied this code).

    14  *

    15  * You should have received a copy of the GNU General Public License version

    16  * 2 along with this work; if not, write to the Free Software Foundation,

    17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    18  *

    19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    20  * or visit www.oracle.com if you need additional information or have any

    21  * questions.

    22  */

    23 import java.security.*;

    24 import java.lang.instrument.*;

    25 import java.lang.reflect.*;

    26 

    27 public class Agent implements ClassFileTransformer {

    28     public synchronized byte[] transform(final ClassLoader classLoader,

    29                                          final String className,

    30                                          Class<?> classBeingRedefined,

    31                                          ProtectionDomain protectionDomain,

    32                                          byte[] classfileBuffer) {

    33         System.out.println("Transforming class " + className);

    34         return classfileBuffer;

    35     }

    36 

    37     public static void redefine(String agentArgs, Instrumentation instrumentation, Class to_redefine) {

    38 

    39         try {

    40             instrumentation.retransformClasses(to_redefine);

    41         } catch (Exception e) {

    42             e.printStackTrace();

    43         }

    44 

    45     }

    46 

    47     public static void premain(String agentArgs, Instrumentation instrumentation) {

    48         Agent transformer = new Agent();

    49         instrumentation.addTransformer(transformer, true);

    50 

    51         // Redefine java/lang/Object and java/lang/reflect/Method.invoke and

    52         // java/lang/ClassLoader

    53         Class object_class = Object.class;

    54         redefine(agentArgs, instrumentation, object_class);

    55 

    56         Class method_class = Method.class;

    57         redefine(agentArgs, instrumentation, method_class);

    58 

    59         Class loader_class = ClassLoader.class;

    60         redefine(agentArgs, instrumentation, loader_class);

    61 

    62         instrumentation.removeTransformer(transformer);

    63     }

    64 

    65     public static void main(String[] args) {

    66         byte[] ba = new byte[0];

    67 

    68         // If it survives 100 GC's, it's good.

    69         for (int i = 0; i < 100 ; i++) {

    70             System.gc();

    71             ba.clone();

    72         }

    73         try {

    74             // Use java/lang/reflect/Method.invoke to call

    75             WalkThroughInvoke a = new WalkThroughInvoke();

    76             Class aclass = WalkThroughInvoke.class;

    77             Method m = aclass.getMethod("stackWalk");

    78             m.invoke(a);

    79         } catch (Exception x) {

    80             x.printStackTrace();

    81         }

    82     }

    83 }