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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 2001-2005 (C) Exoffice Technologies Inc. All Rights Reserved.
42   *
43   * $Id: QueueBrowserEndpoint.java,v 1.3 2005/08/30 07:26:49 tanderson Exp $
44   */
45  package org.exolab.jms.messagemgr;
46  
47  import javax.jms.InvalidSelectorException;
48  import javax.jms.JMSException;
49  
50  import org.exolab.jms.message.MessageImpl;
51  
52  
53  /***
54   * A QueueBrowserEndpoint is a QueueListener to a QueueDestinationCache. This
55   * enables it to receive all the messages, which it then feeds down to the
56   * client side.
57   *
58   * @author <a href="mailto:jima@comware.com.au">Jim Alateras</a>
59   * @author <a href="mailto:tma@netspace.net.au">Tim Anderson
60   * @version $Revision: 1.3 $ $Date: 2005/08/30 07:26:49 $
61   */
62  public class QueueBrowserEndpoint extends AbstractConsumerEndpoint {
63  
64      /***
65       * Cache of all handles for this consumer.
66       */
67      private MessageQueue _handles = new MessageQueue();
68  
69      /***
70       * The destination that this consumer subscribes to.
71       */
72      private QueueDestinationCache _cache;
73  
74  
75      /***
76       * Create a new <code>QueueBrowserEndpoint</code>.
77       *
78       * @param consumerId the identity of this consumer
79       * @param cache      the destination cache
80       * @param selector   the message selector. May be <code>null</code>
81       * @throws InvalidSelectorException if <code>selector</code> is invalid
82       * @throws JMSException             if the destination cache can't be
83       *                                  created
84       */
85      public QueueBrowserEndpoint(long consumerId, QueueDestinationCache cache,
86                                  String selector)
87              throws InvalidSelectorException, JMSException {
88          super(consumerId, cache.getDestination(), selector, false);
89  
90          _cache = cache;
91  
92          // set up the message cache and register itself as a listener to the
93          // cache
94          _cache.addQueueListener(this);
95          _cache.playbackMessages(this);
96      }
97  
98      /***
99       * This event is called when a non-persistent message is added to a
100      * <code>DestinationCache</code>..
101      *
102      * @param handle  a handle to the added message
103      * @param message the added message
104      * @return <code>true</code> if the listener accepted the message; otherwise
105      *         <code>false</ode>
106      */
107     public boolean messageAdded(MessageHandle handle, MessageImpl message) {
108         _handles.add(handle);
109 
110         // notify the consumer
111         notifyMessageAvailable();
112         return true;
113     }
114 
115     /***
116      * This event is called when a persistent message is added to the
117      * <code>DestinationCache</code>.
118      *
119      * @param handle  a handle to the added message
120      * @param message the added message
121      * @return <code>true</code>
122      */
123     public boolean persistentMessageAdded(MessageHandle handle,
124                                           MessageImpl message) {
125         return messageAdded(handle, message);
126     }
127 
128     /***
129      * This event is called when a message is removed from the
130      * <code>DestinationCache</code>.
131      *
132      * @param messageId the identifier of the removed message
133      */
134     public void messageRemoved(String messageId) {
135         _handles.remove(messageId);
136     }
137 
138     /***
139      * This event is called when a message is removed from the
140      * <code>DestinationCache</code>.
141      *
142      * @param messageId a handle to the removed message
143      */
144     public void persistentMessageRemoved(String messageId) {
145         messageRemoved(messageId);
146     }
147 
148     /***
149      * Return the number of unsent messages in the cache for this consumer.
150      *
151      * @return the number of unsent messages
152      */
153     public int getMessageCount() {
154         return _handles.size();
155     }
156 
157     /***
158      * Return the next available message to the client.
159      *
160      * @param cancel
161      * @return the next message, or <code>null</code> if none is available
162      * @throws JMSException for any error
163      */
164     protected MessageHandle doReceive(Condition cancel) throws JMSException {
165         MessageHandle result = null;
166         MessageHandle handle;
167         while (!cancel.get() && (handle = _handles.removeFirst()) != null) {
168             // ensure the message still exists
169             MessageImpl message = handle.getMessage();
170             if (message != null) {
171                 if (selects(message)) {
172                     result = handle;
173                     // got a message which is applicable for the endpoint
174                     break;
175                 }
176             }
177         }
178         return result;
179     }
180 
181     /***
182      * Closes this endpoint.
183      */
184     protected void doClose() {
185         // unregister from the DestinationCache
186         _cache.removeQueueListener(this);
187     }
188 
189 }