Introduction


Now it's time to answer these questions: How can I advertise my Web service? What is the best searching mechanism that will produce the most precise and appropriate list of possible Web services that will meet my needs? This chapter briefly introduces the standard in Web service registries, Universal Description, Discovery, and Integration (UDDI), and what it has to offer. UDDI is an initiative conceived and sponsored by a private consortium of technology companies named uddi.org. This chapter then explains how WebLogic Server supports this technology. Prior knowledge of UDDI (the UDDI API and its data structures) is presumed and is necessary for comprehending the concepts in this chapter. More information on UDDI can be found at www.uddi.org.

The service-oriented architecture of Web services is shown in Figure 31.1.

Figure 31.1. Players in a Web service-oriented architecture.

graphics/31fig01.gif

A service provider offers some Web services, but these services are useless if no client knows about them. Hence, the provider publishes its services in a UDDI registry. A client can then search or browse a UDDI registry to discover Web services that meet its needs. When an appropriate service is found, the client then invokes the service from the provider.

Service discovery can occur at two possible junctures:

  • During client development ” When the client is being written, a UDDI registry can be manually browsed or searched for appropriate services. The client developer reads the service details and hard-codes the service invocations into the client. This is also known as static discovery .

  • During client execution ” The client is written such that, at runtime, it contacts a UDDI registry of choice and issues the necessary UDDI calls to find and then bind to a particular service. It then needs to comprehend the service details and formulate a service call in the format prescribed by the technical service interface. Although implementing this paradigm of dynamic discovery is obviously more complex, it does provide the ultimate in flexibility of service choice and provider choice. For reasons we won't describe here, this approach may not be practical at the current evolution of Web services. But there are many possibilities for static/dynamic hybrids, where certain service elements can be known and hard-coded at development time (such as a service interface) and some discovered dynamically (such as a service location/URL).

Again, it is not the intent of this chapter to provide a full treatise on UDDI. The goal is to provide a simplified and high-level discussion of the UDDI technology and to point out what WebLogic Server 7.0 features support UDDI.



BEA WebLogic Platform 7
BEA WebLogic Platform 7
ISBN: 0789727129
EAN: 2147483647
Year: 2003
Pages: 360

flylib.com © 2008-2017.
If you may any questions please contact us: flylib@qtcs.net