Introduction to the Solution

REpresentational State Transfer (REST) defines a set of architectural principles for distributed systems, in which Web Services are viewed as resources. Those resources are identified by URIs and can be addressed and transferred using the HTTP protocol. REST can be used with a number of technologies, including JPA. HTTP methods are used to access and perform operations on resources.

The Java API for RESTful Web Services (JAX-RS) is an API designed to make it easy to develop Java applications that use the REST architecture. With JAX-RS, you use annotations to define resources and the actions that can be performed on those resources.

While it is possible to use JAX-RS directly to interact with JPA persistence units in a RESTful application, RESTful Data Services provide an API that makes it easier to implement REST for JPA persistence,. You can use this API to interact with JPA persistence units without explicitly writing JAX-RS code, thus providing a simple way to expose persistence units through REST.

Note:

For an example that uses JAX-RS directly to implement JPA persistence in a RESTful application, see "RESTful Service Example" at http://wiki.eclipse.org/EclipseLink/Examples/REST/GettingStarted. For information about simplifying that process by using RESTful Data Services, continue reading this chapter.

RESTful Data Services are made available via a web fragment, which extends the capabilities of a web application. The REST functionality is made available by including the RESTful Data Services JAR file in the WEB-INF/lib folder of a web application.

The RESTful Data Services runtime provides access to all persistence units packaged in the application in which it is running, as well as any dynamic persistence units that are provisioned within it.