In-Depth

Explaining Java and Web services

One of the biggest problems with Web services, said authors David Chappell and Tyler Jewell, is explaining it -- that is, pulling all the pieces together into a coherent and hype-free description of what Web services are and how developers can create and deploy them. Longtime developers Chappell and Jewell are most concerned with Java jocks, and their solution is a new book, Java Web Services (O'Reilly & Associates, Sebastopol, Calif., 2002).

Chappell and Jewell provide readers with a concise introduction that includes a detailed overview of Web services, XML-based interoperability technologies and the Java technologies designed to interact with them.

Readers can find working examples of how each Java-based API can be used in real-world, business-to-business communications environments. The authors explain how Java developers can use SOAP to perform remote method calls and message passing; how to use WSDL to describe the interface to a Web service or understand the interface of someone else's service; and how to use UDDI to advertise, or publish and look up, services in each local or global registry.

The key word in SOAP is simple. But it does mean different things to different people. And members of development teams, both within and without the organization, may come to view it from different, incompatible perspectives. In Java Web Services, Chappell and Jewell advise cross-project teams to share semantics in advance, standardize service definition methodologies, and to use the same or compatible versions of the SOAP spec.

'There have been a lot of interoperability efforts underway. SOAP is designed to provide platform-neutral interoperable communications,' said Chappell, who serves as vice president and chief technology evangelist at Sonic Software, in a recent visit to ADT's offices. 'However, it's still early enough in its stages that one implementer's view of what that means vs. another's might not exactly mesh.

'A lot of it has to do with serialization and deserialization of data as it goes across the wire,' added Chappell. In other words, systems package XML documents and send them over SOAP transports. When the receiving application gets the package, it must convert it correctly to the right data types.

'By leaps and bounds there's been a lot of progress made in that area,' enthused Chappell. He noted the online SOAPbuilders interoperability project  as a worthwhile endeavor in this regard.

For more information, please read the related articles 'Web services: Report from the field' and 'Starting with Web services.'

About the Authors

Jack Vaughan is former Editor-at-Large at Application Development Trends magazine.

John K. Waters is a freelance writer based in Silicon Valley. He can be reached at john@watersworks.com.

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