Implementing REST resources with JAX-RS

REST stands for Representational State Transfer and is an architectural style for distributed systems. In REST, data and functionality are represented as 'resources' which can be accessed using a Uniform Resource Identifier (URI/URL) and acted upon using a simple set of well-defined actions, namely the HTTP verbs GET, POST, PUT and DELETE.

JAX-RS is the Java API for RESTful web services. A RESTful web service in JAX-RS is a plain old Java object (POJO) which has been annotated with JAX-RS annotations. These annotations define how the resource is to be contacted: the URL segment the resource services, which HTTP method it responds to, what parameters it accepts and what it returns as shown in the example below.

Why RESTful Services?

Easy to implement: With JAX-RS, RESTful services are easy to create and deploy. With a few annotations, you are up and running.
Loose coupling: Any client that wishes to utilize a RESTful service only requires three pieces of information about it - the URL, the parameters and the format of the response. Once these are established, the client and service can be implemented more or less independently.
Easy to integrate: RESTful services are easily consumed by a variety of clients, including modern JavaScript frameworks like Ext JS.