How to implement a PhaseListener which runs at end of lifecycle?

You need to implement the PhaseListener interface and hook on beforePhase() of the PhaseId_RENDER_RESPONSE. The render response is the last phase of the JSF lifecycle.

public class MyPhaseListener implements PhaseListener {

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

    @Override
    public void beforePhase(PhaseEvent event) {
        // Do your job here which should run right before the RENDER_RESPONSE.
    }

    @Override
    public void afterPhase(PhaseEvent event) {
        // Do your job here which should run right after the RENDER_RESPONSE.
    }

}

To get it to run, register it as follows in faces-config.xml:

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

---

Update the above phase listener is indeed applicaiton-wide. To have a phase listener for a specific view, use the beforePhase and/or afterPhase attributes of the <f:view>.

E.g.

<f:view beforePhase="#{bean.beforePhase}">
    ...
</f:view>

with

public void beforePhase(PhaseEvent event) {
    if (event.getPhaseId() == PhaseId.RENDER_RESPONSE) {
        // Do here your job which should run right before the RENDER_RESPONSE.
    }
}

A more JSF 2.0 way is by the way using the <f:event type="preRenderView">:

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

with

public void preRenderView() {
    // Do here your job which should run right before the RENDER_RESPONSE.
}