A component tag has a set of attributes for referencing backing bean methods that can perform certain functions for the component associated with the tag. These attributes are summarized in Table 8–4.
Table 8–4 Component Tag Attributes That Reference Backing Bean Methods
Attribute |
Function |
---|---|
Refers to a backing bean method that performs navigation processing for the component and returns a logical outcome String |
|
Refers to a backing bean method that handles action events |
|
Refers to a backing bean method that performs validation on the component’s value |
|
Refers to a backing bean method that handles value-change events |
Only components that implement ActionSource can use the action and actionListener attributes. Only components that implement EditableValueHolder can use the validator or valueChangeListener attributes.
The component tag refers to a backing bean method using a method expression as a value of one of the attributes. The method referenced by an attribute must follow a particular signature, which is defined by the tag attribute’s definition in the TLD. For example, the definition of the validator attribute of the inputText tag in html_basic.tld is the following:
void validate(javax.faces.context.FacesContext, javax.faces.component.UIComponent, java.lang.Object)
The following sections give examples of how to use the four different attributes.
If your page includes a component (such as a button or hyperlink) that causes the application to navigate to another page when the component is activated, the tag corresponding to this component must include an action attribute. This attribute does one of the following:
Specifies a logical outcome String that tells the application which page to access next
References a backing bean method that performs some processing and returns a logical outcome String
The following examples shows how to reference a navigation method:
<h:commandButton value="#{bundle.Submit}" action="#{cashier.submit}" />
If a component on your page generates an action event, and if that event is handled by a backing bean method, you refer to the method by using the component’s actionListener attribute.
The following example shows how the method is referenced:
<h:commandLink id="NAmerica" action="bookstore" actionListener="#{localeBean.chooseLocaleFromLink}">
The actionListener attribute of this component tag references the chooseLocaleFromLink method using a method expression. The chooseLocaleFromLink method handles the event when user clicks the hyperlink rendered by this component.
If the input of one of the components on your page is validated by a backing bean method, refer to the method from the component’s tag using the validator attribute.
The following example shows how to reference a method that performs validation on email, an input component:
<h:inputText id="email" value="#{checkoutFormBean.email}" size="25" maxlength="125" validator="#{checkoutFormBean.validateEmail}"/>
If you want a component on your page to generate a value-change event and you want that event to be handled by a backing bean method, you refer to the method using the component’s valueChangeListener attribute.
The following example shows how a component references a ValueChangeListener implementation that handles the event when a user enters a name in the name input filed:
<h:inputText id="name" size="50" value="#{cashier.name}" required="true"> <f:valueChangeListener type="listeners.NameChanged" /> </h:inputText>
To refer to this backing bean method, the tag uses the valueChangeListener attribute:
<h:inputText id="name" size="50" value="#{cashier.name}" required="true" valueChangeListener="#{cashier.processValueChange}" /> </h:inputText>
The valueChangeListener attribute of this component tag references the processValueChange method of CashierBean using a method expression. The processValueChange method handles the event of a user entering a name in the input field rendered by this component.