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


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 2005 (C) Exoffice Technologies Inc. All Rights Reserved.
42  *
43  * $Id: AbstractMessageRef.java,v 1.1 2005/03/18 03:58:38 tanderson Exp $
44  */
45
46 package org.exolab.jms.messagemgr;
47
48 import javax.jms.JMSException JavaDoc;
49
50
51 /**
52  * Abstract implementation of the {@link MessageRef} interface
53  *
54  * @author <a HREF="mailto:tma@netspace.net.au">Tim Anderson</a>
55  * @version $Revision: 1.1 $ $Date: 2005/03/18 03:58:38 $
56  */
57 abstract class AbstractMessageRef implements MessageRef {
58
59     /**
60      * The message identifier.
61      */
62     private String JavaDoc _messageId;
63
64     /**
65      * Determines if the message is persistent.
66      */
67     private final boolean _persistent;
68
69     /**
70      * The message reference count.
71      */
72     private volatile int _count;
73
74
75     /**
76      * Construct a new <code>AbstractMessageRef</code>.
77      *
78      * @param messageId the message identifier
79      * @param persistent determines if the message is persistent
80      */
81     public AbstractMessageRef(String JavaDoc messageId, boolean persistent) {
82         _messageId = messageId;
83         _persistent = persistent;
84         _count = 0;
85     }
86
87     /**
88      * Returns the message identifier.
89      *
90      * @return the message identifier
91      */
92     public String JavaDoc getMessageId() {
93         return _messageId;
94     }
95
96     /**
97      * Determines if the underlying message is persistent.
98      *
99      * @return <code>true</code> if the message is persistent; otherwise
100      * <code>false</code>
101      */
102     public boolean isPersistent() {
103         return _persistent;
104     }
105
106     /**
107      * Increment the reference.
108      */
109     public void reference() {
110         ++_count;
111     }
112
113     /**
114      * Decrement the reference. If there are no references to the message, it
115      * will be destroyed.
116      *
117      * @throws JMSException for any error
118      */
119     public void dereference() throws JMSException JavaDoc {
120         if (!isDestroyed()) {
121             if (--_count <= 0) {
122                 destroy();
123                 setDestroyed();
124             }
125         }
126     }
127
128     /**
129      * Determines if this has been destroyed.
130      *
131      * @return <code>true</code> if this has been destroyed
132      */
133     protected boolean isDestroyed() {
134         return (_count < 0);
135     }
136
137     /**
138      * Mark this as being destroyed.
139      */
140     protected void setDestroyed() {
141         _count = -1;
142     }
143
144 }
145
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