JSF

JavaServer Faces (JSF) is a Java specification for building component-based user interfaces for web applications. It provides a server-side framework that manages UI components, event handling, and the lifecycle of a user interface, enabling developers to build reusable UI elements and pages. JSF is part of the Java Platform, originally within Java EE and, since the transition to Jakarta EE, under the Jakarta namespace. A typical JSF application routes requests through a central FacesServlet, which creates and manages a component tree and a request lifecycle.

Key concepts in JSF include UI components, Facelets as the view declaration language, and Expression Language (EL) bindings that connect UI components to backing beans. Views are usually authored in XHTML using Facelets, and components are bound to properties of managed beans or CDI beans. Navigation between pages can be declared in configuration files or implemented through implicit rules. Render kits determine how the component tree is converted into the final markup, typically HTML, but other renderers are possible.

The JSF lifecycle consists of six phases: Restore View, Apply Request Values, Process Validations, Update Model Values, Invoke Application, and Render Response. This sequence allows validation, conversion, and business logic to be centralized in backing beans and controllers.

Over time, JSF has evolved to support AJAX out of the box, CDI integration, and improved tooling and component libraries, such as PrimeFaces and RichFaces, which provide rich widgets and client-side interactivity while maintaining a JSF-based backend. JSF remains a standardized option for server-side UI in Java web applications, valued for its component model, declarative navigation, and integration with the wider Java EE/Jakarta EE ecosystem.