JSF

JSF (JavaServer Faces) — now maintained as Jakarta Faces — is a Java specification for building component-based, server-side user interfaces for web applications. Rather than assembling HTML by hand, developers compose pages from reusable UI components whose state, events, and rendering are managed by a well-defined request-processing lifecycle. It is a server-centric approach to the web, rooted in the Java EE / Jakarta EE stack.

• A component model - Reusable, stateful UI components render to HTML and handle their own input and events.
• A defined request lifecycle - Phases for restoring view, applying values, validation, model update, and rendering govern each interaction.
• Managed beans and expression language - Backing beans bind UI components to application data and logic.
• Server-side state management - The framework tracks view state across requests rather than pushing it all to the client.

In API operations, JSF represents the older, server-rendered style of building web front-ends — the model many enterprises are moving away from as they decouple their user interfaces from their backends. That decoupling is exactly where APIs come in: as teams retire monolithic JSF applications, they tend to re-expose the underlying business logic as clean OpenAPI-described services that single-page apps, mobile clients, and now agents can consume directly. Understanding a legacy JSF surface is often the first step in mapping what an organization’s real API footprint should be.