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.
During the maintenance cycle for JSR 67, it was decided to unbundle the low-level SOAP message creation features into a separate specification, thus creating SAAJ 1.1, leaving the higher-level features to form JAXM Version 1.1. At the same time, minor modifications were made to the API to remove a dependency that would otherwise have had the undesirable effect of making SAAJ 1.1 dependent on JAXM 1.1. The result is that it is possible to use SAAJ as a lightweight library for building and exchanging SOAP messages, without requiring the inclusion of JAXM 1.1, which provides facilities that go beyond the requirements of many web service clients. JAX-RPC, in particular, uses SAAJ to construct and decode SOAP messages, but it does not require reliable messaging and therefore is not dependent on the presence of a JAXM implementation.
The formal specifications for both SAAJ 1.1 and JAXM 1.1 can be downloaded from http://jcp.org/jsr/detail/67.jsp. This chapter looks only at SAAJ and uses it as a convenient means of introducing SOAP messages; the more advanced messaging facilities provided by JAXM are covered in Chapter 4.
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