JavaServer Faces (JSF) is a framework for building web-based user interfaces in Java. Like Swing, it provides a set of standard widgets (buttons, hyperlinks, checkboxes, and so on), a model for creating custom widgets, a way to process client-generated events (like changing the value of a text box or clicking on a button), and excellent tool support.

Since web-based applications, unlike their Swing cousins, must often appease multiple clients (desktop browsers, phones, PDAs, and so on), JSF has a powerful architecture for displaying components in different ways. However, most JSF applications are built for desktop browsers, and JSF widgets (commonly called user interface components, or UI components) can provide integrated, dynamic Ajax support without requiring knowledge of JavaScript.

JSF also has extensible facilities for validating input (like the length of a field) and converting objects to and from strings for display. The framework can also automatically keep your user interface components in sync with your business model objects, and has basic dependency injection facilities for creating and initializing objects.