Java Server Faces seems to have a lot to offer in Java EE 5, one would really question the existing Web Frameworks – traditional Struts or Web Works – seem antiquated immediately.
Backing Beans – deferred evaluation, bound listeners, validators and convertors provide powerful flexibility.
JSF has a powerful lifecycle, with events, renderers, components orchestrated prior to the response going out.
Renderer Kit provides output in any format, if none is provided you get HTML rendering by default.
JSF must be compliant with at least Servlet Specifications 1.3 or later. JSP 1.2 or later, and packaged in a standard war file.