Learning Java, 4th Edition

Implementing Web Services

Now that we’ve covered servlets and web applications in detail, we’d like to return to the topic of web services. In the previous chapter, we introduced the concept of a web service as an extension of the basic HTTP web transaction, using XML content for application-to-application communication instead of consumption by a web browser client. In that chapter, we showed how easy it is to invoke an RPC-style web service, by using client-side classes generated from a WSDL description file. In this section, we’ll show the other side of that equation and demonstrate how to implement and deploy a web service.

The world of web services has evolved quickly, as have the APIs, buzzwords, and hype. The appeal of this style of interapplication communication using simple web protocols has, to some extent, been tarnished by the design-by-committee approach of many standards bodies and competitors adding features and layers to the web services concept. The truth is that web services were originally simple and elegant when compared to more elaborate protocols, largely because they did not support all of the same semantics—state management, callbacks, transactions, authentication, and security. As these features are added, the complexity returned. We will not cover all aspects of web services in detail but instead focus on the basic RPC style that is appealing for a wide variety of simple applications.

In Chapter 14, we walked through generating and running the client side ...