viewAction (OmniFaces VDL Documentation - Generated Documentation)

Description:
The <o:viewAction> is a component that extends the standard <f:viewAction> and changes the if attribute to be evaluated during INVOKE_APPLICATION phase instead of the APPLY_REQUEST_VALUES phase. This allows developers to let the if attribute check the converted and validated model values before performing the view action, which results in much more intuitive behavior.
In below example, the FooConverter may convert a non-null parameter to null without causing a validation or conversion error, and the intent is to redirect the current page to otherpage.xhtml when the converted result is null.
```
					<f:viewParam name="foo" value="#{bean.foo}" converter="fooConverter" />
					<f:viewAction action="otherpage" if="#{bean.foo eq null}" />
					
```
This is however not possible with standard <f:viewAction> as it evaluates the if attribute already before the conversion has taken place. This component solves that by postponing the evaluation of the if attribute to the INVOKE_APPLICATION phase.
```
					<f:viewParam name="foo" value="#{bean.foo}" converter="fooConverter" />
					<o:viewAction action="otherpage" if="#{bean.foo eq null}" />
					
					Only when you set immediate="true", then it will behave the same as the standard
					<f:viewAction>.
 				
		
```

Component Information
Info	Value
Component Type	`org.omnifaces.component.input.ViewAction`
Handler Class	None
Renderer Type	None
Description	None

Attributes
Name	Required	Type	Description
`action`	`false`	`javax.el.MethodExpression` (signature must match `java.lang.Object action()`)	`MethodExpression` representing the application action to invoke when this component is activated by the user. The expression must evaluate to a public method that takes no parameters, and returns an `Object` (the `toString()` of which is called to derive the logical outcome) which is passed to the `NavigationHandler` for this application.
`actionListener`	`false`	`javax.el.MethodExpression` (signature must match `void actionListener(javax.faces.event.ActionEvent)`)	`MethodExpression` representing an action listener method that will be notified when this component is activated by the user. The expression must evaluate to a public method that takes an `ActionEvent` parameter, with a return type of void, or to a public method that takes no arguments with a return type of void. In the latter case, the method has no way of easily knowing where the event came from, but this can be useful in cases where a notification is needed that "some action happened".
`phase`	`false`	`javax.el.ValueExpression` (must evaluate to `java.lang.String`)	Specifies the phase in which the action invocation should occur using the name of the phase constant in the PhaseId class (the case does not matter). The value must be one of APPLY_REQUEST_VALUES, PROCESS_VALIDATIONS, UPDATE_MODEL_VALUES, or INVOKE_APPLICATION. The default is INVOKE_APPLICATION.
`if`	`false`	`javax.el.ValueExpression` (must evaluate to `boolean`)	Invoke the application action only when this attribute evaluates true during the specified phase. The default is true.
`onPostback`	`false`	`javax.el.ValueExpression` (must evaluate to `boolean`)	View actions are most commonly used on the initial view request. Therefore, view actions do not operate on postback, by default. This attribute enables a view action to operate on postback.
`immediate`	`false`	`javax.el.ValueExpression` (must evaluate to `boolean`)	Flag indicating that, if this component is activated by the user, notifications should be delivered to interested listeners and actions immediately (that is, during Apply Request Values phase) rather than waiting until Invoke Application phase.

o

Tag viewAction