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This error occurs because an implementation class is cast to an incompatible interface. Several questions can be made in this situation:

  • are there any overlapping jars, with different versions of the same class?
  • Are the multiple versions of the same class all identical or not ?
  • where are the different versions of a given class located ?
  • which class loader is loading which version of a given class ?
  • What does the chain of classloaders look like, how are the class loaders configured ?