How do I catch the read and writes in a java program?

I am trying to create a tool that can capture all the read and writes ma开发者_JS百科de by a java program. Also, I would like to know what fields of what object is access/modified.

I currently looked at:-

1) java.lang.instrument I could not do much with that. I could not understand how to write an agent that can get access to the a running program and create a watch on different objects/fields and anything related. I would appreciated if you have any idea or information on that.

2) jvmti I looked at jvmti and tried to create a jvmti tool, but I figured out that to get the objects, I would need the JVMTI_EVENT_OBJECT_ALLOC be a potential capability. But, I figured that, it is not. Moreover, I read that this event is not called for new command. Hence, at the moment, even this does not seem applicable.

So, I would like to know if you guys know any way to do what I want to do, either using the above mentioned methods or any other technique/tool that you may be aware of?

NOTE: I do not have access to the source code of the application. All, I have are the class files.

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Check these out:

http://download.oracle.com/javase/6/docs/technotes/guides/management/jconsole.html

http://java.sun.com/developer/technicalArticles/J2SE/jconsole.html

http://jamonapi.sourceforge.net/

http://www.manageengine.com/products/applications_manager/java-runtime-monitoring.html

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It's very easy to do with the ASM lib. Create a new Class Loader that instruments all classes before loading them and use it for loading the target classes. Create a new MethodAdapter and override the visitFieldInsn method. Then look for the PUTFIELD, PUTSTATIC, GETFIELD and GETSTATIC opcodes. Although this might look scary (as my explation is most likely gibberish), it's in fact pretty easy. Just download the ASM manual and you'll know how to do it in no time.

Edit: I was forgetting to tell that in order to be able to intercept the reads and writes of done by the JDK code you have to instrument those classes, save them to files and run the JVM with a modified bootstrap classpath, through command line argument -Xbootclasspath (java.* and some other packages; I believe that at least sun.* and javax.* also need this).

This may also be doable with AspectJ... but I'm not sure.