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Java > Open Source Codes > org > exolab > jms > messagemgr > MessageQueue


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: MessageQueue.java,v 1.2 2005/03/18 03:58:39 tanderson Exp $
44  */
45 package org.exolab.jms.messagemgr;
46
47 import java.util.Collections JavaDoc;
48 import java.util.SortedMap JavaDoc;
49 import java.util.TreeMap JavaDoc;
50 import java.util.Map JavaDoc;
51 import java.util.HashMap JavaDoc;
52
53
54 /**
55  * <code>MessageQueue</code> implements a synchronized queue of
56  * {@link MessageHandle} instances.
57  * .<p/>
58  * Message handles are ordered using {@link MessageHandleComparator}
59  *
60  * @version $Revision: 1.2 $ $Date: 2005/03/18 03:58:39 $
61  * @author <a HREF="mailto:jima@intalio.com">Jim Alateras</a>
62  * @author <a HREF="mailto:tma@netspace.net.au">Tim Anderson</a>
63  */
64 class MessageQueue {
65
66     /**
67      * The message handle queue.
68      */
69     private final SortedMap JavaDoc _queue = Collections.synchronizedSortedMap(
70             new TreeMap JavaDoc(new MessageHandleComparator()));
71
72     /**
73      * The set of handles, keyed on message identifier.
74      */
75     private final Map JavaDoc _handles = Collections.synchronizedMap(new HashMap JavaDoc());
76
77
78     /**
79      * Add a message handle.
80      *
81      * @param handle the message handle
82      * @return <code>true</code> if queue set did not already contain the handle
83      */
84     public boolean add(MessageHandle handle) {
85         boolean added = false;
86         if (_queue.put(handle, handle) == null) {
87             _handles.put(handle.getMessageId(), handle);
88             added = true;
89         }
90         return added;
91     }
92
93     /**
94      * Determines if a message handle exists.
95      *
96      * @param handle the message handle
97      * @return <code>true</code> if it exists
98      */
99     public boolean contains(MessageHandle handle) {
100         return _queue.containsKey(handle);
101     }
102
103     /**
104      * Return all elements in the queue.
105      *
106      * @return a list of message handles
107      */
108     public MessageHandle[] toArray() {
109         return (MessageHandle[]) _queue.keySet().toArray(new MessageHandle[0]);
110     }
111
112     /**
113      * Removes a message handle from the queue.
114      *
115      * @param handle the message handle to remove
116      * @return the removed handle, or <code>null</code> if it wasn't present
117      */
118     public MessageHandle remove(MessageHandle handle) {
119         MessageHandle result = (MessageHandle) _queue.remove(handle);
120         if (result != null) {
121             _handles.remove(handle.getMessageId());
122         }
123         return result;
124     }
125
126     /**
127      * Removes a message handle from the queue.
128      *
129      * @param messageId the message identifier of the handle to remove
130      * @return the removed handle, or <code>null</code> if it wasn't present
131      */
132     public MessageHandle remove(String JavaDoc messageId) {
133         MessageHandle result = (MessageHandle) _handles.remove(messageId);
134         if (result != null) {
135             _queue.remove(result);
136         }
137         return result;
138     }
139
140     /**
141      * Removes all the elements from the queue.
142      */
143     public void clear() {
144         _queue.clear();
145         _handles.clear();
146     }
147
148     /**
149      * Returns the number of message handles in the queue.
150      *
151      * @return the number message handles in the queue
152      */
153     public int size() {
154         return _queue.size();
155     }
156
157     /**
158      * Removes and returns the first message handle in the queue.
159      *
160      * @return the first message handle in the queue, or <code>null</code>,
161      * if the queue is empty
162      */
163     public MessageHandle removeFirst() {
164         MessageHandle first = null;
165         synchronized (_queue) {
166             if (_queue.size() > 0) {
167                 first = (MessageHandle) _queue.firstKey();
168                 _queue.remove(first);
169                 _handles.remove(first.getMessageId());
170             }
171         }
172         return first;
173     }
174
175 }
176
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