Until recently, web service interactions were solely synchronous and request-response in nature. However, it soon became clear that the synchronous request-response type of interaction is a very small subset of messaging scenarios. Messaging is very important in constructing loosely coupled systems, and as a result, this limitation is critical. Web service specifications, such as WS-addressing and WSDL, have incorporated the concepts of messaging, and lay the foundation to cover a wider range of messaging scenarios. The Apache Axis2 architecture assumes neither one message exchange pattern, nor synchronous/asynchronous behavior. This article explains messaging concepts and how Axis2 can be used to implement several well-known messaging scenarios.
