Java Web Services: Up and Running, 2nd Edition

A RESTful Web Service as a JAX-RS Resource

The servlet API, the grizzled workhorse for producing Java websites, is still nimble enough to support RESTful web services as well. There are more recent APIs, among them JAX-RS (Java API for XML-RESTful Services). JAX-RS relies upon Java annotations to advertise the RESTful role that a class and its encapsulated methods play. Jersey is the reference implementation (RI) of JAX-RS. RESTEasy, a JBoss project; Apache Wink; and Apache CXF are other implementations. JAX-RS has APIs for programming RESTful services and clients against such services; the two APIs can be used independently. This section focuses on the service-side API. The first JAX-RS example supports only GET requests, but the second JAX-RS example supports all of the CRUD operations.

A First JAX-RS Web Service Using Jersey

JAX-RS web services are resources that can be published with the Tomcat and Jetty web servers. The first example has one resource, the class Adages, and two supporting Java classes: the deployment class RestfulApplication and the POJO class Adage. Exactly how these three classes interact is covered next.

The RestfulAdage class (see Example 2-5) extends the JAX-RS Application class (line 2), which implements a getClasses method that enumerates the individual resources deployed in the WAR file (line 3). In this example, there is but one such resource, Adages, but there could be arbitrarily many (line 4).

Example 2-5. The JAX-RS Application subclass that lists Adages.class ...