001/* 002 * Copyright (c) 2007-2017 Xplenty, 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 021package cascading.flow; 022 023/** 024 * Interface FlowListener provides hooks for receiving events on various stages of a {@link Flow} execution. 025 * <p/> 026 * Any {@link RuntimeException} thrown from any of the listener methods will force the given {@code flow} to 027 * stop by calling {@link Flow#stop()}. 028 */ 029public interface FlowListener 030 { 031 /** 032 * The onStarting event is fired when a Flow instance receives the start() message. 033 * 034 * @param flow 035 */ 036 void onStarting( Flow flow ); 037 038 /** 039 * The onStopping event is fired when a Flow instance receives the stop() message. 040 * 041 * @param flow 042 */ 043 void onStopping( Flow flow ); 044 045 /** 046 * The onCompleted event is fired when a Flow 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 flow 050 */ 051 void onCompleted( Flow flow ); 052 053 /** 054 * The onThrowable event is fired if any child {@link cascading.flow.FlowStep} 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 Flow#complete()} method. 057 * 058 * @param flow 059 * @param throwable 060 * @return returns true if this listener has handled the given throwable 061 */ 062 boolean onThrowable( Flow flow, Throwable throwable ); 063 }