JavaServer Faces

Specifying When to Fire an Event

So far, I’ve told you how to bind a component to an event handling method, but I haven’t let you in yet on the secret of how an ActionEvent can be made to fire either at the end of the Apply Request Value phase or in the Invoke Application phase.

There are different ways to solve this problem, but the specification group decided to go with an approach in which the source component decides when the event should be processed, with a little bit of help from the application developer. Here’s how it works. The FacesEvent class—which all JSF events must extend either directly or through one of the standard subclasses, such as ActionEvent—defines a property named phaseId:

package javax.faces.event;

import java.util.EventObject;
...
public abstract class FacesEvent extends EventObject {
    private PhaseId phaseId = PhaseId.ANY_PHASE;

    public PhaseId getPhaseId( ) {
        return phaseId;
    }

    public void setPhaseId(PhaseId phaseId) {
        this.phaseId = phaseId;
    }
    ...
}

The phaseId property data type is PhaseId, which is a type-safe enumeration containing one value per request processing lifecycle phase: PhaseId.APPLY_REQUEST_VALUES, PhaseId.PROCESS_VALIDATIONS, PhaseId.UPDATE_MODEL_VALUES, PhaseId.INVOKE_APPLICATION, PhaseId.RENDER_RESPONSE, or PhaseId.ANY_PHASE. The PhaseId.ANY_PHASE value means “process the event in the phase where it was queued,” and it’s the default value for the phaseId property.

So even though UICommand always queues an ActionEvent in the Apply Request ...