Java Web Services in a Nutshell

SAAJ Programming

Whereas JAX-RPC is concerned with allowing a client program to make a remote procedure call to a web service without exposing the underlying XML-based protocols that are used, SAAJ is a much lower-level API that is entirely concerned with the messages exchanged between the web service and its clients. Furthermore, while JAX-RPC applications look, for the most part, like ordinary Java applications making local method calls, an application that uses SAAJ needs to construct SOAP messages piece by piece and extract information from response messages. Using SAAJ requires much more work on the part of the developer than JAX-RPC, so why would you bother to use it? Here are some of the circumstances in which you might want to use SAAJ and its close relative JAXM instead of JAX-RPC:

• JAX-RPC is convenient for accessing web services that present an RPC-like interface. However, the RPC model is not suitable for all services. In many cases, it is more convenient to simply send an XML message to a service, which the service interprets and then generates an XML response. The most commonly quoted example of this is a business-to-business service where the client sends a purchase order in the form of an XML document to which the service responds with a confirmation and an invoice, also encoded as an XML document. A simple service like this does not require method calls or arguments — all that is necessary is to exchange fragments of XML. SAAJ represents a convenient way to encode ...