Answer : JSF
JSF is new standard framework, developed through Java Community Process (JCP),
that makes it easy to build user interfaces for java web applications by assembling reusable
components in a page.
Uses of JSF :
JSF provides standard, reusable components for creating user interfaces for web applications.
JSF provides many tag libraries for accessing and manipulating the components.
It automatically saves the form data and repopulates the form when it is displayed at client side.
JSF encapsulates the event handling and component rendering logic from programmers, programmers just use the custom components.
JSF is a specification and vendors can develop the implementations for JSF.
There are many GUIs available these days to simplify the development of web based application based on JSF framework.
Best site for JSF http://www.roseindia.net/jsf/