2.4 Conclusion

This chapter described the various Web service standards and the J2EE 1.4 platform technologies that support those standards in a portable and interoperable manner. It explained why such standards--including XML, SOAP, WSDL, and UDDI--are beneficial to developers, and briefly described each standard. It showed how the platform integrates existing Java and Web service/XML technologies to allow existing and new applications to be exposed as Web services.

In addition, this chapter described the different J2EE platform XML-related APIs, including JAXP, JAXR, JAX-RPC, and SAAJ. It described these technologies from a high-level architectural point of view, and, where appropriate, illustrated their use with sample code. It also showed how to implement a Web service on a J2EE platform using either a JAX-RPC or EJB service endpoint.

Table 2.1 summarizes the standards supported by the different J2EE platform technologies.

J2EE Platform Web Service Support 

Technology Name	Supporting Standard	Purpose
JAXP	XML schema	Enables processing of XML documents in a vendor neutral way; supports SAX and DOM models
JAX-RPC	SOAP	Enables exchange of SOAP requests and responses through an API that hides the complex SOAP details from the developers
JAXR	UDDI, ebXML	Enables accessing business registries with an API that supports any type of registry specification
SAAJ	SOAP with -Attachments	Enables exchange of document--oriented XML messages using Java APIs
J2EE for Web Services	Integrates Java XML technologies into the J2EE platform; supports WS-I Basic -Profile	Enables development and deployment of portable and interoperable Web services on the J2EE platform
JAXB (optional)	Standard in-memory representation of an XML document	Provides an XML data-binding facility for the J2EE platform

Now that you have a good grasp of the Web services technologies, you are ready to proceed with specific design and implementation issues. Chapter 3 describes how to design and implement an endpoint so that your application can make its functionality available as a Web service.