public class CallbackPhaseListener
extends Object
implements PhaseListener

This phase listener picks up phase listener instances from the request scope by addCallbackXxx() methods of the Events utility class and calls them back for each matching phase.

This differs in a few subtle ways from Events.addPhaseListener(PhaseListener). Namely, the phase listener registered here will be called via the global phase listener, which executes slightly earlier for its before phase and slightly later for its after phase as compared to phase listeners attached to the view root.

Additionally, a phase listener registered via this method will not become part of the view state, but will execute only once. Phase listeners attached to the view root will come back after each postback and have to be removed manually (in Mojarra this can be difficult due to the fact iterators over listeners are kept 'open' during each phase).