AbstractEventHandlers can set this to true to stop all further event processing.
Used by EventBus.submit to determine what event sources to process and in what order. This default implementation returns the class hierarchy from the current class upto AbstractEvent. This means that subclasses (more specific) get processed before superclasses (more generic). Override this to customize processing behavior for specific events.
Extend this class to model your own events with any needed data (and behavior).