[Blama]

Isomorphic,

googleing for just "most likely cause is the class represents an abstract class" (with the quotes) I also found this thread of mine (same issue as in this thread) and this thread from claudiobosticco which again has another class throwing the exception. In the latter case you could find some bug introduced between these versions. I think that although this exact issue is most likely unrelated to my problem, perhaps the same type of coding used there does eventually trigger my issue?

In total I find it very confusing that the only search hits for this - which seems to be text from Java and not from the Framework code (this that true?) - are from this forum.

I know that this all seems a bit like reading coffee grounds, but I'm really confused here.

Best regards
Blama

[Isomorphic]

The error message is from our code, but we are reporting an Instantiation Exception returned from the Java Core Reflection API, and it makes no sense for Reflection to throw this exception in this circumstance. So again the cause appears to be:

This actually looks more like the JVM getting internally confused about types. This kind of thing can happen if you do something that causes on-the-fly application reloads, where the JVM is trying to garbage collect actual Java class definitions and then re-load them. If you are reloading your application without restarting the JVM, you might find that this happens only after a reload.

Whatever servlet engine you're using, or perhaps other frameworks your using (Spring maybe?), there appear to be bugs, probably related to class loading. It might be trying to reload classes on the fly. You might be triggering that by touching files that aren't meant to be changed (perhaps something touches .jar files and the servlet engine thinks it needs to reload them).

One thing you could try: turn on the (very verbose) JVM class loading logs. This may show you that basic classes (such as the commons-collection library) are being reloaded by the JVM for some reason. Then once this happens, sometime later, this exception might arise.