Java and XML, Second Edition

Chapter 13. Web Services

In the last chapter, I focused on SOAP as a standalone technology; your application was a SOAP client talking to a SOAP server, based on nothing but Java and a servlet engine. While this is a perfectly good solution for applications in which you write all the clients and all the services, it is fairly limited for interoperating with other applications. If you’ve heard anything about SOAP, it’s the interoperability aspect that has gotten it such good press lately. The last chapter was incomplete; it did not teach you how to do true servicing of other applications using SOAP as a transport mechanism. This chapter fills in the rest of the picture, and solves the remaining problems in interoperability.

To get you started, I apply some simple definitions to the overused term “web services.” Although it’s hard to quantify this term right now, since everyone is using it for their own particular flavor of software and architecture, some general principles apply. In almost every definition of web services, you’ll find that there is a need for an exchange of information with other applications. This exchange needs a set of standards, and the two that are the most important (at least right now) are UDDI and WSDL. I cover both and show you how they fit in with SOAP. Finally, I’ll try and pull all these various acronyms and technologies together into one concrete example to finish off the chapter.

Web Services

Web services seems to have become the next big thing in computing ...