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 2001-2004 (C) Exoffice Technologies Inc. All Rights Reserved.
42 *
43 * $Id: WaitingListener.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 org.apache.log4j.Category;
51
52 import EDU.oswego.cs.dl.util.concurrent.Semaphore;
53
54
55 /***
56 * This class implements the {@link MessageListener} interface and enables
57 * clients to synchronize behaviour with the {@link #onMessage} method.
58 *
59 * @author <a href="mailto:tma@netspace.net.au">Tim Anderson</a>
60 * @version $Revision: 1.3 $
61 */
62 public class WaitingListener extends DelegatingListener {
63
64 /***
65 * The message listener to delegate to
66 */
67 private MessageListener _listener = null;
68
69 /***
70 * The number of times that {@link #onMessage} is expected to be invoked.
71 * If set to -1, then {@link #onMessage} can be invoked any number of
72 * times.
73 */
74 private int _count = -1;
75
76 /***
77 * The number of times that {@link #onMessage} has been invoked.
78 */
79 private int _invoked = 0;
80
81 /***
82 * Semaphore used to synchronize on message receipt
83 */
84 private Semaphore _receiptLock = new Semaphore(0);
85
86 /***
87 * Semaphore used to synchronize message processing
88 */
89 private Semaphore _processLock = new Semaphore(0);
90
91 /***
92 * Semaphore used to synchronize process completion
93 */
94 private Semaphore _completedLock = new Semaphore(0);
95
96 /***
97 * The logger
98 */
99 private static final Category _log =
100 Category.getInstance(WaitingListener.class);
101
102
103 /***
104 * Construct an instance with the listener to delegate messages.
105 * The {@link #onMessage} method may be called any number of times.
106 *
107 * @param listener the message listener that messages will be delegated to
108 */
109 public WaitingListener(MessageListener listener) {
110 this(listener, -1);
111 }
112
113 /***
114 * Construct an instance with the listener to delegate messages, and
115 * the expected number of times that {@link #onMessage} will be invoked.
116 *
117 * @param listener the message listener that messages will be delegated to
118 * @param count the expected number of times that the {@link #onMessage}
119 * will be called
120 */
121 public WaitingListener(MessageListener listener, int count) {
122 super(listener);
123 _count = count;
124 }
125
126 /***
127 * Wait for the listener to receive a message
128 *
129 * @throws InterruptedException if interrupted
130 */
131 public void waitForReceipt() throws InterruptedException {
132 _receiptLock.acquire();
133 }
134
135 /***
136 * Notify the listener that it may continue processing
137 */
138 public void notifyContinue() {
139 _processLock.release();
140 }
141
142 /***
143 * Wait for the listener to complete processing
144 *
145 * @throws InterruptedException if interrupted
146 */
147 public void waitForCompletion() throws InterruptedException {
148 _completedLock.acquire();
149 }
150
151 /***
152 * Invoked when the consumer asynchronously receives a message.
153 * On entry, it notifies the client blocked on {@link #waitForReceipt}.
154 * It then waits for the client to invoke {@link #notifyContinue},
155 * before invoking the listener passed at construction.
156 * This enables clients to synchronize their behaviour with the listener.
157 * <br>
158 * On completion of the listener, it notifies the client blocked on
159 * {@link #waitForCompletion}
160 * <p>
161 * If an invocation count was specified at construction, and
162 * {@link #onMessage} is invoked more than the specified count, an error
163 * is logged, and the method returns immediately.
164 *
165 * @param message the received message
166 */
167 public void onMessage(Message message) {
168 _log.debug("WaitingListener.onMessage() - begin");
169 boolean fail = false;
170 synchronized (this) {
171 // notify the client that a message has been received
172 _receiptLock.release();
173 if (_count != -1) {
174 if (++_invoked > _count) {
175 _log.error(
176 "WaitingListener.onMessage() has been invoked too "
177 + "many times. Expected invocation=" + _count
178 + ", current invocation=" + _invoked);
179 fail = true;
180 }
181 }
182 if (!fail) {
183 try {
184 _log.debug("WaitingListener.onMessage() - waiting");
185 _processLock.acquire();
186 _log.debug(
187 "WaitingListener.onMessage() - done waiting");
188 } catch (InterruptedException ignore) {
189 _log.debug(
190 "WaitingListener.onMessage() - interrupted");
191 }
192 }
193 }
194
195 try {
196 if (!fail) {
197 // delegate behaviour to the listener
198 super.onMessage(message);
199 }
200 } catch (RuntimeException exception) {
201 _log.error(exception, exception);
202 throw exception;
203 } finally {
204 _completedLock.release();
205 _log.debug("WaitingListener.onMessage() - end");
206 }
207 }
208
209 }
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