ClassLoader Leak - Are they worth solving?

Question

ClassLoader leaks usually result in java.lang.OutOfMemoryError: PermGen. In the instance of working on application servers you may see this as a result of

Answer 1

Those are one of the worst leaks... but any leak is evil. So, I, personally, resolve them. Profiling helps as well. There are no easy ways per se but:

• Threads go into threadGroups +starter thread for each module to ensure new Threads() have that group.
• Special care of the Thread.inheritedAccessControlContext (which holds a reference to the classloader)
• WeakReferences when you need to keep classes, actually use WeakReferences for listeners, so no one can skip de-registers (and use only annon. clasess). Having the framework for WeakListeners does help.
• Extra care for DB drives, java.security.Provider
• few more tricks (incl. dynamic enhance of class files but that's overkill usually)

bottom line:

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leaks are evil.