1 /** 2 * This file Copyright (c) 2003-2018 Magnolia International 3 * Ltd. (http://www.magnolia-cms.com). All rights reserved. 4 * 5 * 6 * This file is dual-licensed under both the Magnolia 7 * Network Agreement and the GNU General Public License. 8 * You may elect to use one or the other of these licenses. 9 * 10 * This file is distributed in the hope that it will be 11 * useful, but AS-IS and WITHOUT ANY WARRANTY; without even the 12 * implied warranty of MERCHANTABILITY or FITNESS FOR A 13 * PARTICULAR PURPOSE, TITLE, or NONINFRINGEMENT. 14 * Redistribution, except as permitted by whichever of the GPL 15 * or MNA you select, is prohibited. 16 * 17 * 1. For the GPL license (GPL), you can redistribute and/or 18 * modify this file under the terms of the GNU General 19 * Public License, Version 3, as published by the Free Software 20 * Foundation. You should have received a copy of the GNU 21 * General Public License, Version 3 along with this program; 22 * if not, write to the Free Software Foundation, Inc., 51 23 * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 24 * 25 * 2. For the Magnolia Network Agreement (MNA), this file 26 * and the accompanying materials are made available under the 27 * terms of the MNA which accompanies this distribution, and 28 * is available at http://www.magnolia-cms.com/mna.html 29 * 30 * Any modifications to this file must keep this entire header 31 * intact. 32 * 33 */ 34 package info.magnolia.cms.util; 35 36 import org.slf4j.Logger; 37 import org.slf4j.LoggerFactory; 38 39 import EDU.oswego.cs.dl.util.concurrent.ClockDaemon; 40 41 42 /** 43 * There are many places where we like to delay an execution (in case of a serie of fired events). But we want to ensure 44 * the the task is executed after a certain maximum delay. 45 */ 46 public class DelayedExecutor { 47 48 private static final Logger log = LoggerFactory.getLogger(DelayedExecutor.class); 49 50 protected ClockDaemon timer = new ClockDaemon(); 51 52 protected long delay; 53 54 protected long maxDelay; 55 56 protected long timestamp; 57 58 protected Runnable command; 59 60 /** 61 * The current taskId. 62 */ 63 protected Object taskId; 64 65 /** 66 * @param delay milliseconds 67 * @param maxDelay milliseconds 68 */ 69 public DelayedExecutor(final Runnable command, long delay, long maxDelay) { 70 this.command = new RunnableWrapper(command); 71 this.delay = delay; 72 this.maxDelay = maxDelay; 73 } 74 75 public synchronized void trigger() { 76 long now = System.currentTimeMillis(); 77 log.debug("execution triggered"); 78 79 if (timestamp == 0) { 80 timestamp = now; 81 } 82 if (taskId != null && (timestamp + maxDelay >= now)) { 83 log.debug("execution canceled"); 84 ClockDaemon.cancel(taskId); 85 } 86 taskId = timer.executeAfterDelay(delay, command); 87 } 88 89 /** 90 * Resets the timestamp after starting the execution. Synchronizes the execution. 91 */ 92 protected final class RunnableWrapper implements Runnable { 93 94 private final Runnable command; 95 96 protected RunnableWrapper(Runnable command) { 97 this.command = command; 98 } 99 100 @Override 101 public synchronized void run() { 102 timestamp = 0; 103 this.command.run(); 104 } 105 } 106 107 }