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.