Chapter 10: XML Messaging

Overview

XML is a hot topic. It seems that every commercial software vendor is announcing support for the eXtensible Markup Language (XML) in one form or another. The technology began fairly simply as a means of describing documents, but people quickly realized it had wide application as a generalized way of describing any data. Now, many development organizations are beginning to look to this technology to solve their interoperability problems and provide them with a flexible model for deploying distributed applications. XML is also central to some of the most exciting areas of development on the Internet today, such as the emerging web services arena.

As with any new and rapidly evolving technology, there are a number of design tradeoffs to be made and pitfalls to avoid. The intent of this chapter is to guide newcomers by reviewing the basic concepts behind XML messaging using JMS, and in the process highlight some of the current issues that they should consider when designing JMS applications using XML.

This chapter is broken into four major subsections:

• What XML Brings to Messaging: Here, we will examine the XML value proposition, highlighting why XML is effective as a messaging format, and how it complements JMS by further achieving the goals of this technology.

• Parsing and Transformation: Presents the major parsing paradigms in XML, providing a simple Java example of each using the JAXP API.

• XML and JMS: Looks at the relationship between XML and JMS, and the special considerations that have to be made in bringing these two technologies together.

• An XML Router Example: The example section develops a simple content-based JMS router. This routes and transforms XML messages between queues, based on the value of attributes in an XML message.

Note 

XML is a diverse and complex topic, and we really cannot hope to do more than scratch its surface here. For further information on working with XML, we recommend you look at Professional XML ISBN 1-861003-11-0, also from Wrox Press.