Java Reference
In-Depth Information
2 SOAP
Objectives
After reading this chapter, you should:
1. Possess a basic understanding of SOAP
2. Be able to describe the structure of a SOAP message
3. Understand how to process a SOAP message
4. Be able to map a SOAP to a transport protocol
5. Be able to write a simple SOAP client using SOAP with Attachment for Java
(SAAJ)
SOAP was an improvement of XML-RPC (Remote Procedure Call) that made it possible
to use XML to represent data between two systems. Initially, SOAP message structure was
relatively simple. Since SOAP used HTTP protocol, it was tunneled through firewall using
the Internet infrastructure. According to World Wide Web Consortium (W3C), SOAP is
defined as follows (
http://www.w3.org/ TR/2007/REC-
soap12-part1-20070427/
):
…a lightweight protocol intended for exchanging structured information in
a decentralized, distributed environment. It uses XML technologies to define
an extensible messaging framework providing a message construct that can
be exchanged over a variety of underlying protocols. The framework has
been designed to be independent of any particular programming model and
other implementation specific semantics.
SOAP was implemented as a plug-in to many middleware platforms and enabled data
exchange over the Internet in addition to intranet. The initial emphasis on RPC thus allowed
SOAP to become widely implemented as a wire-protocol over the Internet. Eventually, the
need for interactions other than RPC led to the Documentation type of exchange. Protocols
other than HTTP have also emerged over the years (e.g., SMTP and JMS).
SOAP Version 1.2 is a lightweight protocol intended for exchanging structured information
in a decentralized, distributed environment (
http
://w
ww.w3.org/TR/soap12-part
1/#in
tro
).
