I wanted to instrument some methods/classes in Java. For that purpose I wrote an Java agent that instruments only a few classes that I choose.
I use the following code to get the loaded classes and filter some of them:
instrumentation.addTransformer(myTransformer,true);
Class[] loadedClasses=instrumentation.getAllLoadedClasses();
Class[] modifiableClasses=ModifiableClasses(loadedClasses,instrumentation);
Class[] filteredClasses=filterClasses(modifiableClasses);
if(instrumentation.isRetransformClassesSupported()){
System.out.println("retransformation is Supported");
instrumentation.retransformClasses(filteredClasses);
}
this should not create any problem filterClasses returns some classes that I want to be instrumented normally I want to instrument these Classes:
- Ljava/nio/Buffer;
- Ljava/util/HashMap$Entry;
- Ljava/nio/HeapCharBuffer;
- Ljava/nio/CharBuffer;
- Ljava/lang/ClassLoader;
- Ljava/lang/Class;
- Ljava/util/HashMap;
- Ljava/nio/ByteBuffer;
- Ljava/lang/System;
- Ljava/io/BufferedWriter;
- Ljava/lang/String;
- Ljava/io/OutputStreamWriter;
- Ljava/io/BufferedOutputStream;
- Ljava/nio/charset/CoderResult;
- Ljava/io/Writer;
- Ljava/util/HashSet;
- Ljava/nio/charset/CharsetEncoder;
- Ljava/io/FileOutputStream;
- Ljava/io/PrintStream;
everything works fine I print the instrumented and unistrumented classes in specific folders for debug. I use the asm CoreAPI to add some instructions at the beginning and the end of methods I dont instrument Constructors,native methods, abstract methods and static variables. When I just instrument the new classes that are being loaded everything works fine. I guess I dont understand something with the ClassLoader or something specific here is what I get on the Console:
Exception in thread "main" java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at sun.instrument.InstrumentationImpl.loadClassAndStartAgent(Unknown Source)
at sun.instrument.InstrumentationImpl.loadClassAndCallPremain(Unknown Source)
Caused by: java.lang.InternalError
at sun.instrument.InstrumentationImpl.retransformClasses0(Native Method)
at sun.instrument.InstrumentationImpl.retransformClasses(Unknown Source)
at my.Agent.Watcher.premain(Watcher.java:88)
... 6 more
FATAL ERROR in native method: processing of -javaagent failed
I am thankful for any help I can get even a link or a hint in the right direction.
