Introduction JavaServer Faces solves many of the historical problems of Java Web development by providing a clean implementation of the Model-View-Controller design pattern while providing a productive, component-centric development without sacrificing development power and flexibility. Additionally since JSF is a Java standard, multiple software vendors will continue to provide evermore productive and efficient development environments which will no doubt rival and most probably surpass proprietary visual development environments. What is JSF? JavaServer Faces (JSF) is a new standard Java framework for building Web applications. It simplifies development by providing a component-centric approach to developing Java Web user interfaces. JavaServer Faces also appeals to a diverse audience of Java/Web developers. "Corporate developers" and Web designers will find that JSF development can be as simple as dragging and dropping user interface (UI) components onto a page, while "systems developers" will find that the rich and robust JSF API offers them unsurpassed power and programming flexibility. JSF also ensures that applications are well designed with greater maintainability by integrating the well established Model-View-Controller (MVC) design pattern into it's architecture. Finally, since JSF is a Java standard developed through Java Community Process (JCP), development tools vendors are fully empowered to provide easy to use, visual, and productive develop environments for JavaServer Faces. One of the key advantages of JSF is that it is both a Java Web user-interface standard as well as a framework that firmly follows the Model-View-Controller(MVC) design pattern. This makes JSF applications much more manageable because the user-interface code (View) is cleanly separated from the application data and logic (Model). To prepare the JSF context, which provides application data access to the pages, and to guard against unauthorized or improper access of the pages, all user interactions with the application are handled by a front-end "Faces" servlet (Controller). The JSF Lifecycle The Faces Controller servlet serves as the link between the user and the JSF application. It operates within the confines of a well defined JSF Lifecycle which dictates the entire flow of events between user requests. For example, upon an initial Web request to access a JSF application, the Faces controller servlet handles the request by first preparing the JSF context, which is a Java object that holds all application data. The controller then routes the user to the requested page. The page usually renders application data from the JSF context using a simple Expression Language. Upon subsequent requests, the controller updates any Model data, providing any new input has been entered. JSF developers have programmatic access to the entire JSF lifecycle at any time during its execution thus affording a high degree of control over the application's behavior at all times.
