1 /***
2 * Redistribution and use of this software and associated documentation
3 * ("Software"), with or without modification, are permitted provided
4 * that the following conditions are met:
5 *
6 * 1. Redistributions of source code must retain copyright
7 * statements and notices. Redistributions must also contain a
8 * copy of this document.
9 *
10 * 2. Redistributions in binary form must reproduce the
11 * above copyright notice, this list of conditions and the
12 * following disclaimer in the documentation and/or other
13 * materials provided with the distribution.
14 *
15 * 3. The name "Exolab" must not be used to endorse or promote
16 * products derived from this Software without prior written
17 * permission of Exoffice Technologies. For written permission,
18 * please contact info@exolab.org.
19 *
20 * 4. Products derived from this Software may not be called "Exolab"
21 * nor may "Exolab" appear in their names without prior written
22 * permission of Exoffice Technologies. Exolab is a registered
23 * trademark of Exoffice Technologies.
24 *
25 * 5. Due credit should be given to the Exolab Project
26 * (http://www.exolab.org/).
27 *
28 * THIS SOFTWARE IS PROVIDED BY EXOFFICE TECHNOLOGIES AND CONTRIBUTORS
29 * ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT
30 * NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
31 * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
32 * EXOFFICE TECHNOLOGIES OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
33 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
34 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
35 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
36 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
37 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
38 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
39 * OF THE POSSIBILITY OF SUCH DAMAGE.
40 *
41 * Copyright 2000 (C) Exoffice Technologies Inc. All Rights Reserved.
42 *
43 * $Id: BlockingWorkerQueue.java,v 1.4 2003/08/07 13:33:12 tanderson Exp $
44 *
45 * Date Author Changes
46 * 5/15/2001 jima Created
47 */
48
49
50 package org.exolab.jms.util;
51
52 import java.util.LinkedList;
53
54
55 /***
56 * A BlockingWorkerQueue is attached to a QueueWorker. Any thread can add
57 * work to the queue. The BlockingWorkerQueue, which extends Thread, blocks
58 * waiting for work to arrive. When work arrives it will be dequeued and
59 * passed down to the QueueWorker for processing.
60 * <p>
61 * The owner can use <code>close</code> to gracefully shutdown the thread.
62 *
63 * @version $Revision: 1.4 $ $Date: 2003/08/07 13:33:12 $
64 * @author <a href="mailto:jima@exolab.org">Jim Alateras</a>
65 */
66 public class BlockingWorkerQueue
67 extends Thread {
68
69 /***
70 * This is the runnable that will perform the work
71 */
72 private QueueWorker _worker = null;
73
74 /***
75 * The list is used to queue work
76 */
77 private LinkedList _queue = new LinkedList();
78
79 /***
80 * If this is set to true then we must close the worker queue
81 */
82 private boolean _closed = false;
83
84
85 /***
86 * Construct a blocking worker queue and attahc to the specified
87 * queue worker. Make the thread a deamon thread.
88 *
89 * @param name - the name of the thread
90 * @param worker - the queue worker attached to this queue
91 */
92 public BlockingWorkerQueue(String name, QueueWorker worker) {
93 super("BWQ:" + name);
94 _worker = worker;
95 this.setDaemon(true);
96 }
97
98 /***
99 * Add some work to the end of the queue
100 *
101 * @param work - add this piece of work
102 */
103 public void add(Object object) {
104 synchronized (_queue) {
105 _queue.addLast(object);
106 _queue.notifyAll();
107 }
108 }
109
110 /***
111 * This method is called once the thread has started. It basically loops
112 * forever removing work from the queue and passing it to the runnable.
113 * <p>
114 * Calling <code>close</code> on this object will terminate it.
115 */
116 public void run() {
117 while (!_closed) {
118 Object work = null;
119
120 synchronized (_queue) {
121 // if there are no messages in the queue then block
122 if (_queue.size() == 0) {
123 try {
124 _queue.wait();
125 } catch (InterruptedException exception) {
126 // ignore the exception;
127 }
128 continue;
129 }
130
131 // if we get this far then there is something in the queue.
132 // Remove it and hand it to the worker
133 work = _queue.removeFirst();
134 }
135
136 if (work != null) {
137 _worker.execute(work);
138 }
139 }
140 }
141
142 /***
143 * Return the number of entries still on the queue
144 *
145 * @size int
146 */
147 public int size() {
148 return _queue.size();
149 }
150
151 /***
152 * Close this worker queue
153 */
154 public void close() {
155 _closed = true;
156 interrupt();
157 }
158
159 }
160
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