/**
     * Register the given listener which will receive all events.
     *
     * @param listener the listener to register
     * @throws NullPointerException if {@code listener} is null
     */
    void registerListener(@Nonnull Listener listener);

    /**
     * Unregisters a previously registered listener.
     *
     * @param listener the listener to unregister

            configurator = container.lookup(ComponentConfigurator.class, configuratorId);

            ConfigurationListener listener = new DebugConfigurationListener(logger);

            ValidatingConfigurationListener validator =
                    new ValidatingConfigurationListener(mojo, mojoDescriptor, listener);

            if (logger.isDebugEnabled()) {

        ModelBuildingListener listener = getModelBuildingListener(request);

        if (listener != null) {
            AtomicReference<Model> m = new AtomicReference<>(model);

            ModelBuildingEvent event = new DefaultModelBuildingEvent(model, m::set, request, problems);

            catapult.accept(listener, event);

            return m.get();
        }

            this.modelCache = modelCache;
            return this;
        }

        public ModelBuilderRequestBuilder listener(Object listener) {
            this.listener = listener;
            return this;
        }

        public ModelBuilderRequestBuilder interimResult(ModelBuilderResult interimResult) {
            this.interimResult = interimResult;

                            .source(modelSource)
                            .projectBuild(true)
                            .locationTracking(true)
                            .listener(listener)
                            .build();

                    if (pomFile != null) {
                        project.setRootDirectory(rootLocator.findRoot(pomFile.getParent()));
                    }

        void run(AbstractMavenLifecycleParticipant listener, MavenSession session) throws MavenExecutionException;
    }

    private void callListeners(MavenSession session, ListenerMethod method) throws MavenExecutionException {
        ClassLoader originalClassLoader = Thread.currentThread().getContextClassLoader();
        try {
            for (AbstractMavenLifecycleParticipant listener :

        for (ProjectExecutionListener listener : listeners) {
            listener.beforeProjectExecution(event);
        }
    }

    @Override
    public void beforeProjectLifecycleExecution(ProjectExecutionEvent event) throws LifecycleExecutionException {
        for (ProjectExecutionListener listener : listeners) {
            listener.beforeProjectLifecycleExecution(event);
        }
    }

                    InternalMavenSession.from(ee.getSession().getSession());
            Collection<Listener> listeners = session.getListeners();
            if (!listeners.isEmpty()) {
                Event event = new DefaultEvent(session, ee);
                for (Listener listener : listeners) {
                    listener.onEvent(event);
                }
            }
        }
    }

    @Override

    }

    @Override
    public void registerListener(@Nonnull Listener listener) {
        listeners.add(nonNull(listener));
    }

    @Override
    public void unregisterListener(@Nonnull Listener listener) {
        listeners.remove(nonNull(listener));
    }

    @Nonnull
    @Override
    public Collection<Listener> getListeners() {
        return Collections.unmodifiableCollection(listeners);

                    listener.sessionStarted(event);
                    break;
                case SessionEnded:
                    listener.sessionEnded(event);
                    break;

                case ProjectSkipped:
                    listener.projectSkipped(event);
                    break;
                case ProjectStarted:
                    listener.projectStarted(event);
                    break;