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 }