What Is Facelets?

Facelets is a powerful but lightweight page declaration language that is used to build JavaServer Faces views using HTML style templates and to build component trees. Facelets features include the following:

• Use of XHTML for creating web pages

• Support for Facelets tag libraries in addition to JavaServer Faces and JSTL tag libraries

• Support for the Expression Language (EL)

• Templating for components and pages

Advantages of Facelets for large-scale development projects include the following:

• Support for code reuse through templating and composite components

• Functional extensibility of components and other server-side objects through customization

• Faster compilation time

• Compile-time EL validation

• High-performance rendering

In short, the use of Facelets reduces the time and effort that needs to be spent on development and deployment.

Facelets views are usually created as XHTML pages. JavaServer Faces implementations support XHTML pages created in conformance with the XHTML Transitional Document Type Definition (DTD), as listed at http://www.w3.org/TR/xhtml1/#a_dtd_XHTML-1.0-Transitional. By convention, web pages built with XHTML have an .xhtml extension.

JavaServer Faces technology supports various tag libraries to add components to a web page. To support the JavaServer Faces tag library mechanism, Facelets uses XML namespace declarations. Table 5–1 lists the tag libraries supported by Facelets.

Table 5–1 Tag Libraries Supported by Facelets

Tag Library	URI	Prefix	Example	Contents
JavaServer Faces Facelets Tag Library	http://java.sun.com/jsf/facelets	ui:	ui:component ui:insert	Tags for templating
JavaServer Faces HTML Tag Library	http://java.sun.com/jsf/html	h:	h:head h:body h:outputText h:inputText	JavaServer Faces component tags for all UIComponents
JavaServer Faces Core Tag Library	http://java.sun.com/jsf/core	f:	f:actionListener f:attribute	Tags for JavaServer Faces custom actions that are independent of any particular RenderKit
JSTL Core Tag Library	http://java.sun.com/jsp/jstl/core	c:	c:forEach c:catch	JSTL 1.1 Core Tags
JSTL Functions Tag Library	http://java.sun.com/jsp/jstl/functions	fn:	fn:toUpperCase fn:toLowerCase	JSTL 1.1 Functions Tags

In addition, Facelets supports tags for composite components for which you can declare custom prefixes. For more information on composite components, see Composite Components.

Based on the JavaServer Faces support for Expression Language (EL) syntax defined by JSP 2.1, Facelets uses EL expressions to reference properties and methods of backing beans. EL expressions can be used to bind component objects or values to methods or properties of managed beans. For more information on using EL expressions, see Using the EL to Reference Backing Beans.