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 tma@netspace.net.au.
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 2003-2004 (C) Exoffice Technologies Inc. All Rights Reserved.
42 *
43 * $Id: CountingListener.java,v 1.3 2004/01/31 13:44:24 tanderson Exp $
44 */
45 package org.exolab.jmscts.core;
46
47 import javax.jms.Message;
48 import javax.jms.MessageListener;
49
50 import EDU.oswego.cs.dl.util.concurrent.Semaphore;
51
52
53 /***
54 * Helper class for counting the number of messages received.
55 * Clients waiting on this will be notified when the expected number of
56 * messages are received.
57 *
58 * @version $Revision: 1.3 $ $Date: 2004/01/31 13:44:24 $
59 * @author <a href="mailto:tma@netspace.net.au">Tim Anderson</a>
60 */
61 public class CountingListener implements MessageListener {
62
63 /***
64 * The number of expected messages
65 */
66 private final int _expected;
67
68 /***
69 * The actual number of messages received
70 */
71 private volatile int _count = 0;
72
73 /***
74 * Semaphore used to synchronize process completion
75 */
76 private Semaphore _completedLock = new Semaphore(0);
77
78
79 /***
80 * Construct an instance of the listener, with the number of messages
81 * expected to be received. When this count is reached, the listener
82 * notifies the waiting client (if any)
83 *
84 * @param expected the number of messages expected
85 */
86 public CountingListener(int expected) {
87 _expected = expected;
88 }
89
90 /***
91 * This method is asynchronously invoked by the message consumer when
92 * a message becomes available.
93 * If the number of expected messages are received, it notifies
94 * the waiting client (if any)
95 *
96 * @param message the received message
97 */
98 public void onMessage(Message message) {
99 if (++_count >= _expected) {
100 _completedLock.release();
101 }
102 }
103
104 /***
105 * Returns the no. of messages expected
106 *
107 * @return the no. of messages expected
108 */
109 public int getExpected() {
110 return _expected;
111 }
112
113 /***
114 * Returns the count of received messages
115 *
116 * @return the number of messages received
117 */
118 public int getReceived() {
119 return _count;
120 }
121
122 /***
123 * Wait for the listener to complete processing
124 *
125 * @param timeout the number of milleseconds to wait. An argument less
126 * than or equal to zero means not to wait at all
127 * @throws InterruptedException if interrupted while waiting
128 * @return <code>true</code> if the listener completed in the given time
129 * frame
130 */
131 public boolean waitForCompletion(long timeout)
132 throws InterruptedException {
133 boolean completed = _completedLock.attempt(timeout);
134 if (completed) {
135 _completedLock.release();
136 }
137 return completed;
138 }
139
140 /***
141 * Wait indefinitely for the listener to complete processing
142 *
143 * @throws InterruptedException if interrupted while waiting
144 */
145 public void waitForCompletion() throws InterruptedException {
146 _completedLock.acquire();
147 _completedLock.release();
148 }
149
150 }
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