如何调试JVM资源加载？

Question

要在JVM中调试类加载，我们可以使用param -verbose:class ，但是......任何人都知道如何调试资源加载（例如属性文件）？

Answer 1

I suppose you need to look at using a profiler. Or something that uses the instrumentation interface.

Not sure how stable it is, but there is BTrace , which is kind of a Java version of DTrace.

BTrace is a safe, dynamic tracing tool for the Java platform. BTrace can be used to dynamically trace a running Java program. BTrace dynamically instruments the classes of the target application to inject tracing code ("bytecode tracing"). Tracing code is expressed in Java programming language.

If you are doing this on a development machine, and the number of events (resources being loaded) is not too frequent, you could also just set a breakpoint in the debugger.

Answer 2

You could use InTrace to instrument the Classloader classes which do the loading.

For the Sun JVM, I would suggest using the following Include patterns to trace appropriate classes:

• ClassLoader
• URLClassPath
• Loader

Answer 3

Resources are provided as URL s. So, I guess to do it in "pure" Java: Install a custom ClassLoader that copies URL s into a version with a custom URLStreamHandler . Put your monitoring code in the stream handler and forward to the original.

Answer 4

There exist a couple of techniques to debug classloading problems . Here are good slides from the JRebel creators summarizing those techniques: Do you really get class loaders?

Answer 5

In a Linux environment you can try:

lsof -p <jvm pid>

It will give you a list with the descriptors used by the program associated with the specified pid.

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