By default, JSF 1.2 uses JSP as its view technology, however JSF was designed to be very modular, allowing defaults to be swapped out for alternative technologies.
Facelets, by Jacob Hookom, is an alternate view technology for JSF. The main advantage of Facelets is that pages are written using standard XHTML, which allows web designers to freely design the pages, using design tools such as Dreamweaver. Using Facelets allows a true separation of concerns, with web designers designing the user interface of the system, and Java developers implementing the functionality.
Another advantage of Facelets is that it provides templating for JSF. Facelets templating is similar in functionality to tools such as Sitemesh and Apache Tiles. Using Facelets templates, common areas of all pages in the application, such as headers, footers and navigation menus, can be placed in in separate files, and they are "included" by all pages in the application. Templating allows us to make changes to these common areas in a single file, and they are "inherited" by all pages in the application, greatly simplifying maintenance.
Until now, in order to take advantage of Facelets additional dependencies had to be added to our project, since Facelets was non standard. Well, according to Arun Gupta and Ed Burns, Facelets will become the default JSF technology as of JSF 2.0. This will be a great step in simplifying JSF application development.
Arun Gupta has a very nice tutorial explaining how to get started developing JSF 2.0 applications under GlassFish today.
