The resource adapter is expected to know the endpoint message listener type (either by using the ActivationSpec JavaBean contents or based on the ActivationSpec JavaBean class) and deliver messages to the endpoint. The resource adapter may optionally pass an XAResource instance while creating a message endpoint in order to receive transactional notifications when a message delivery is transacted. Some options include javax.jms.MessageListener, javax.xml.messaging.OnewayListener, javax.xml.messaging.ReqRespListener.