As you probably know, JAX-RS 2/Java EE 7 now includes a brand new standard client API. If you don't know about it yet, you should check out this excellent blog entry by Mohamed Sanaulla now :-). The standard client API uses the factory/builder patterns and not injection. This makes it very well suited for Java SE based environments such as JUnit tests and JavaFX UIs. However Jersey, the JAX-RS 2 reference implemention included in GlassFish 4 goes much further by providing a managed JAX-RS client that makes full use of injection. This is ideal for server-side mash-ups and system-to-system/machine-to-machine communication.
Michal Gajdos of the Jersey team does an excellent job of explaining the API details in this code-driven blog entry. You can also check out the code on GitHub and running example on Heroku!