ExecutionEvent event = new DefaultExecutionEvent(eventType, session, mojoExecution, exception);

            switch (eventType) {
                case ProjectDiscoveryStarted:
                    listener.projectDiscoveryStarted(event);
                    break;

                case SessionStarted:
                    listener.sessionStarted(event);
                    break;

        this.dispatcher = dispatcher;
        this.delegate = delegate;
    }

    @Override
    public void projectDiscoveryStarted(ExecutionEvent event) {
        dispatcher.onEvent(event);
        delegate.projectDiscoveryStarted(event);
    }

    @Override
    public void sessionStarted(ExecutionEvent event) {
        dispatcher.onEvent(event);
        delegate.sessionStarted(event);

 * {@link AbstractExecutionListener} in order to avoid interoperability problems.
 *
 */
public interface ExecutionListener {

    void projectDiscoveryStarted(ExecutionEvent event);

    void sessionStarted(ExecutionEvent event);

    void sessionEnded(ExecutionEvent event);

    void projectSkipped(ExecutionEvent event);

/**
 * Provides a skeleton implementation for execution listeners. The methods of this class are empty.
 *
 */
public class AbstractExecutionListener implements ExecutionListener {

    public void projectDiscoveryStarted(ExecutionEvent event) {
        // default does nothing
    }

    public void sessionStarted(ExecutionEvent event) {
        // default does nothing
    }

/**
 * Holds data relevant for an execution event.
 *
 */
public interface ExecutionEvent {

    /**
     * The possible types of execution events.
     */
    enum Type {
        ProjectDiscoveryStarted,
        SessionStarted,
        SessionEnded,
        ProjectSkipped,
        ProjectStarted,
        ProjectSucceeded,
        ProjectFailed,
        MojoSkipped,
        MojoStarted,

        } catch (LookupException e) {
            return addExceptionToResult(result, e);
        }

        eventCatapult.fire(ExecutionEvent.Type.ProjectDiscoveryStarted, session, null);

        Result<? extends ProjectDependencyGraph> graphResult = buildGraph(session);

        if (graphResult.hasErrors()) {
            return addExceptionToResult(