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Question:
The LogOrRethrowExceptionHandler doesn't do anything with an Exception that is not classified as DEBUG,WARN,ERROR or RETHROW. Is there a reason why this class doesn't rethrow exceptions by default?

Reply:
LogOrRethrowExceptionHandler relies on ExceptionClassifier to classify the exception, so I think it is expected invariant that the exception always falls into one of the predefined categories. Adding an else clause that would throw an IllegalStateException if the exception has not been classified would make sense then.

Reply:
An IllegalStateException would indeed make sense.
Yesterday the LogOrRethrowExceptionHandler swallowed some ClassNotFoundExceptions that were being thrown. I would expect that any unexpected exception would stop the batch processing.