Java Web Services in a Nutshell

Chapter 3. SAAJ

In the last chapter, you saw how to use JAX-RPC to create web services based around the use of remote procedure calls. Even though JAX-RPC uses an XML-based protocol, there was hardly any XML in evidence in Chapter 2. For the most part, JAX-RPC does a very good job of hiding the details of messages that are exchanged between a web service and its client during a remote procedure call. However, most of the more advanced JAX-RPC features require an understanding of SOAP, the XML-based protocol on which JAX-RPC in particular, and web services in general, are based. This chapter paves the way for a more in-depth examination of JAX-RPC by introducing SOAP, together with SAAJ, which is a Java API for creating, sending, and receiving SOAP messages.

Introduction to SAAJ

SAAJ, which stands for SOAP with Attachments API for Java, provides a convenient API for constructing SOAP messages without having to directly create the XML yourself. SAAJ was originally part of the Java API for XML Messaging (JAXM), which was developed by the JSR 67 expert group. The final release of this specification (JAXM Version 1.0) provided two different but related facilities:

• Core functionality concerned with manipulating SOAP messages in a generic way, together with the ability to send a SOAP message from one entity to another.

• A higher-level messaging facility that included reliable delivery of messages and support for messaging profiles, which require SOAP messages to be constructed in specific ways. ...