found a config file at \WEB-INF\classes\META-INF\CustomWorkItemHandlers.conf ,thus we could set our own workItem handler.
furthermore ,I want to extends an asynchronous workitem.
So try in this way.
1.implements an workitem with executeWorkItem function sending some parameters and workitemId ,deploymentunitid and processinstanceid to other asynchronous system,like camel or spring integration.here ,take this workitem as a Producer.
2.implement Receiver ,witch will be called by other asynchronous system.