User Interface Component Classes

JavaServer Faces technology provides a set of UI component classes and associated behavioral interfaces that specify all the UI component functionality, such as holding component state, maintaining a reference to objects, and driving event handling and rendering for a set of standard components.

The component classes are completely extensible, allowing component writers to create their own custom components. See Chapter 13, Creating Custom UI Components for an example of a custom image map component.

All JavaServer Faces UI component classes extend UIComponentBase, which defines the default state and behavior of a UI component. The following set of UI component classes is included with JavaServer Faces technology:

• UIColumn: Represents a single column of data in a UIData component.

• UICommand: Represents a control that fires actions when activated.

• UIData: Represents a data binding to a collection of data represented by a DataModel instance.

• UIForm: Encapsulates a group of controls that submit data to the application. This component is analogous to the form tag in HTML.

• UIGraphic: Displays an image.

• UIInput: Takes data input from a user. This class is a subclass of UIOutput.

• UIMessage: Displays a localized message.

• UIMessages: Displays a set of localized messages.

• UIOutput: Displays data output on a page.

• UIPanel: Manages the layout of its child components.

• UIParameter: Represents substitution parameters.

• UISelectBoolean: Allows a user to set a boolean value on a control by selecting or deselecting it. This class is a subclass of UIInput.

• UISelectItem: Represents a single item in a set of items.

• UISelectItems: Represents an entire set of items.

• UISelectMany: Allows a user to select multiple items from a group of items. This class is a subclass of UIInput.

• UISelectOne: Allows a user to select one item from a group of items. This class is a subclass of UIInput.

• UIViewRoot: Represents the root of the component tree.

In addition to extending UIComponentBase, the component classes also implement one or more behavioral interfaces, each of which defines certain behavior for a set of components whose classes implement the interface.

These behavioral interfaces are as follows:

• ActionSource: Indicates that the component can fire an action event. This interface is intended for use with components based on JavaServer Faces technology 1.1_01 and earlier versions.

• ActionSource2: Extends ActionSource, and therefore provides the same functionality. However, it allows components to use the unified EL when referencing methods that handle action events.

• EditableValueHolder: Extends ValueHolder and specifies additional features for editable components, such as validation and emitting value-change events.

• NamingContainer: Mandates that each component rooted at this component have a unique ID.

• StateHolder: Denotes that a component has state that must be saved between requests.

• ValueHolder: Indicates that the component maintains a local value as well as the option of accessing data in the model tier.

UICommand implements ActionSource2 and StateHolder. UIOutput and component classes that extend UIOutput implement StateHolder and ValueHolder. UIInput and component classes that extend UIInput implement EditableValueHolder, StateHolder, and ValueHolder. UIComponentBase implements StateHolder. See the JavaServer Faces Technology 1.2 API Specification for more information on these interfaces.

Only component writers will need to use the component classes and behavioral interfaces directly. Page authors and application developers will use a standard UI component by including a tag that represents it on a JSP page. Most of the components can be rendered in different ways on a page. For example, a UICommand component can be rendered as a button or a hyperlink.

The next section explains how the rendering model works and how page authors choose how to render the components by selecting the appropriate tags.