Chapter 3. SOAP Essentials

SOAP is an XML-based protocol for exchanging information between computers. Although SOAP can be used in a variety of messaging systems and can be delivered via a variety of transport protocols, the initial focus of SOAP is remote procedure calls transported via HTTP. SOAP therefore enables client applications to easily connect to remote services and invoke remote methods. For example (as we shall soon see), a client application can immediately add language translation to its feature set by locating the correct SOAP service and invoking the correct method.

Other frameworks, including CORBA, DCOM, and Java RMI, provide similar functionality to SOAP, but SOAP messages are written entirely in XML and are therefore uniquely platform- and language-independent. For example, a SOAP Java client running on Linux or a Perl client running on Solaris can connect to a Microsoft SOAP server running on Windows 2000.

SOAP therefore represents a cornerstone of the web service architecture, enabling diverse applications to easily exchange services and data.

Although still in its infancy, SOAP has received widespread industry support. Dozens of SOAP implementations now exist, including implementations for Java, COM, Perl, C#, and Python. At the same time, hundreds of SOAP services are blossoming across the Web.

This chapter aims to provide you with the essentials of SOAP. The following topics are covered:

  • A quick overview of the SOAP protocol and a sample SOAP conversation ...

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