Can't keep faces message after navigation from preRender

Question

in my preRender code for a page i add faces message then make navigation to another page as follows:

if(error){
addMessageToComponent(null,\"AN ERROR HAS OCC         


        

Answer 1

The preRenderView event runs in the very beginning of the RENDER_RESPONSE phase. It's too late to instruct the Flash scope to keep the messages. You can do this at the latest during the INVOKE_APPLICATION phase.

Since there's no standard JSF component system event for this, you'd need to homebrew one:

@NamedEvent(shortName="postInvokeAction")
public class PostInvokeActionEvent extends ComponentSystemEvent {

    public PostInvokeActionEvent(UIComponent component) {
        super(component);
    }

}

To publish this, you need a PhaseListener:

public class PostInvokeActionListener implements PhaseListener {

    @Override
    public PhaseId getPhaseId() {
        return PhaseId.INVOKE_APPLICATION;
    }

    @Override
    public void beforePhase(PhaseEvent event) {
        // NOOP.
    }

    @Override
    public void afterPhase(PhaseEvent event) {
        FacesContext context = FacesContext.getCurrentInstance();
        context.getApplication().publishEvent(context, PostInvokeActionEvent.class, context.getViewRoot());
    }

}

After registering it as follows in faces-config.xml:

<lifecycle>
    <phase-listener>com.example.PostInvokeActionListener</phase-listener>
</lifecycle>

You'll be able to use the new event as follows:

<f:event type="postInvokeAction" listener="#{bean.init}" />

You only need to make sure that you've at least a <f:viewParam>, otherwise JSF won't enter the invoked phase at all.

The JSF utility library OmniFaces already supports this event and the preInvokeAction event out the box. See also the showcase page which also demonstrates setting a facesmessage for redirect.