What is New in JAX-RS 2.0?

The major new features of JAX-RS 2.0 are as follows:
A client API was missing from JAX-RS 1.x so each implementation defined its own proprietary API. JAX-RS 2.0 fills this gap with a fluent, low-level, request building API.

Like SOAP handlers or Managed Bean interceptors, JAX-RS 2.0 now has filters and interceptors so you can intercept request and response and do some processing.

With the new asynchronous processing you can now implement long-polling interfaces or
server-side push.

Integration with Bean Validation has been achieved so you can constrain your RESTful web services.

JAX-RS Packages for REST
javax.ws.rs
High-level interfaces and annotations used to create RESTful web service

javax.ws.rs.client
Classes and interfaces of the new JAX-RS client API

javax.ws.rs.container
Container-specific JAX-RS API

javax.ws.rs.core
Low-level interfaces and annotations used to create RESTful web resources

javax.ws.rs.ext
APIs that provide extensions to the types supported by the JAX-RS API

Ref : Beginning of JavaEE 7