001    /*
002     * Copyright (c) 2007-2014 Concurrent, Inc. All Rights Reserved.
003     *
004     * Project and contact information: http://www.cascading.org/
005     *
006     * This file is part of the Cascading project.
007     *
008     * Licensed under the Apache License, Version 2.0 (the "License");
009     * you may not use this file except in compliance with the License.
010     * You may obtain a copy of the License at
011     *
012     *     http://www.apache.org/licenses/LICENSE-2.0
013     *
014     * Unless required by applicable law or agreed to in writing, software
015     * distributed under the License is distributed on an "AS IS" BASIS,
016     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
017     * See the License for the specific language governing permissions and
018     * limitations under the License.
019     */
020    
021    package cascading.cascade;
022    
023    /**
024     * Interface CascadeListener provides hooks for receiving events on various stages of a {@link cascading.cascade.Cascade} execution.
025     * <p/>
026     * Any {@link RuntimeException} thrown from any of the listener methods will force the given {@code cascade} to
027     * stop by calling {@link cascading.cascade.Cascade#stop()}.
028     */
029    public interface CascadeListener
030      {
031      /**
032       * The onStarting event is fired when a Cascade instance receives the start() message.
033       *
034       * @param cascade the current Cascade
035       */
036      void onStarting( Cascade cascade );
037    
038      /**
039       * The onStopping event is fired when a Cascade instance receives the stop() message.
040       *
041       * @param cascade the current Cascade
042       */
043      void onStopping( Cascade cascade );
044    
045      /**
046       * The onCompleted event is fired when a Cascade instance has completed all work whether if was success or failed. If
047       * there was a thrown exception, onThrowable will be fired before this event.
048       *
049       * @param cascade the current Cascade
050       */
051      void onCompleted( Cascade cascade );
052    
053      /**
054       * The onThrowable event is fired if any child {@link cascading.flow.Flow} throws a Throwable type. This throwable is passed
055       * as an argument to the event. This event method should return true if the given throwable was handled and should
056       * not be rethrown from the {@link cascading.cascade.Cascade#complete()} method.
057       *
058       * @param cascade   the current Cascade
059       * @param throwable the current error
060       * @return returns true if this listener has handled the given throwable
061       */
062      boolean onThrowable( Cascade cascade, Throwable throwable );
063      }