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 }