why JSF?

Java Server Faces technology , developed by Java Community Process(JCP) ,simplifies the development of Java Based web applications.
Java Server Faces is a component oriented and event driven framework for web applications. JSF eases the development of GUI for web applications. JSF allows the programmers to work with extensible user interfaces like buttons, text boxes, check boxes etc... Programmer writes the code for particular event such as button clicked. This makes programming much easier and now the there is no need to write request and response processing logic.

Main feature of JSF is ease of use. Developing web applications is easier and faster than other frameworks like struts because JSF supports UI components and easy event handling.JSF is based on well established Model-View-Controller (MVC) design pattern. Applications developed using JSF frameworks are well designed and easy to maintain then any other applications developed in JSP and Servlets.

JSF includes mainly:
Set of APIs to represent and manage state of components that helps server side validation, event handling, page navigation, data conversion etc.
JSP custom tag library to create UI components in a view page.

The UI (user interface) created using JSF technology runs on server and output is shown to the client. Goal of JSF is to create web applications faster and easier. Developers can focus on UI components, events handling, backing beans and their interactions rather than request, response and markup. JSF hides complexities to enable developers to focus on their own specific work.