1 /*

     2  * Copyright (c) 2018, 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  */

    24 

    25 import java.lang.instrument.ClassFileTransformer;

    26 import java.lang.instrument.Instrumentation;

    27 import java.lang.instrument.IllegalClassFormatException;

    28 import java.security.ProtectionDomain;

    29 

    30 public class AnonVmClassesDuringDumpTransformer implements ClassFileTransformer {

    31     public byte[] transform(ClassLoader loader, String name, Class<?> classBeingRedefined,

    32                             ProtectionDomain pd, byte[] buffer) throws IllegalClassFormatException {

    33         return null;

    34     }

    35 

    36     private static Instrumentation savedInstrumentation;

    37 

    38     public static void premain(String agentArguments, Instrumentation instrumentation) {

    39         System.out.println("ClassFileTransformer.premain() is called");

    40         instrumentation.addTransformer(new AnonVmClassesDuringDumpTransformer(), /*canRetransform=*/true);

    41         savedInstrumentation = instrumentation;

    42 

    43         // This will create a Lambda, which will result in some Anonymous VM Classes

    44         // being generated.

    45         //

    46         // Look for something like these in the STDOUT:

    47         // ----------------

    48         // ClassFileTransformer.premain() is called

    49         // Dumping class files to DUMP_CLASS_FILES/...

    50         // dump: DUMP_CLASS_FILES/java/lang/invoke/LambdaForm$MH000.class

    51         // dump: DUMP_CLASS_FILES/java/lang/invoke/LambdaForm$MH001.class

    52         // Invoked inside a Lambda

    53         // ----------------

    54         Runnable r = () -> {

    55             System.out.println("Invoked inside a Lambda");

    56         };

    57         r.run();

    58     }

    59 

    60     public static Instrumentation getInstrumentation() {

    61         return savedInstrumentation;

    62     }

    63 

    64     public static void agentmain(String args, Instrumentation inst) throws Exception {

    65         premain(args, inst);

    66     }

    67 }