The MessageCracker expects an invoker to be registered for the specific actual Message type being processed. If an invoker exists for a supertype of the received Message, the invoker won't be called.

For those extending MessageCracker, the onMessage(quickfix.Message message, SessionID sessionID) method can be overridden to allow implementers to handle the most general quickfix.Message type (but not, for example, only quickfix.fix44.Message messages).

However, for those providing a delegate object to the MessageCracker, there is no option to provide a handler for a more general Message type to provide custom fallback logic.

The crack(..) method should look for invokers registered for the received Message's superclass(es), as well as its actual type, before resorting to the fallback onMessage call in MessageCracker.