Java API for RESTful Web Services (JAX-RS), is a set if APIs to developer REST service. JAX-RS is part of the Java EE6, and make developers to develop REST web application easily.
In this series of JAX-RS tutorials, we use both Jersey and RESTEasy, popular JAX-RS implementation.
Happy learning JAX-RS :)
JAX-RS Tutorial
http://www.mkyong.com/tutorials/jax-rs-tutorials/