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 1.3 2005/12/20 20:31:59 tanderson Exp $
44 */
45
46 package org.exolab.jms.messagemgr;
47
48 import javax.jms.JMSException;
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: 1.3 $ $Date: 2005/12/20 20:31:59 $
56 */
57 abstract class AbstractMessageRef implements MessageRef {
58
59 /***
60 * The message identifier.
61 */
62 private String _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>, with a zero reference
77 * count.
78 *
79 * @param messageId the message identifier
80 * @param persistent determines if the message is persistent
81 */
82 public AbstractMessageRef(String messageId, boolean persistent) {
83 _messageId = messageId;
84 _persistent = persistent;
85 _count = 0;
86 }
87
88 /***
89 * Returns the message identifier.
90 *
91 * @return the message identifier
92 */
93 public String getMessageId() {
94 return _messageId;
95 }
96
97 /***
98 * Determines if the underlying message is persistent.
99 *
100 * @return <code>true</code> if the message is persistent; otherwise
101 * <code>false</code>
102 */
103 public boolean isPersistent() {
104 return _persistent;
105 }
106
107 /***
108 * Increment the reference.
109 *
110 * @throws JMSException if the handle has been destroyed
111 */
112 public synchronized void reference() throws JMSException {
113 if (isDestroyed()) {
114 throw new JMSException("Cannot reference message, JMSMessageID="
115 + _messageId
116 + ". Message has been destroyed");
117 }
118 ++_count;
119 }
120
121 /***
122 * Decrement the reference. If there are no references to the message, it
123 * will be destroyed.
124 *
125 * @throws JMSException for any error
126 */
127 public synchronized void dereference() throws JMSException {
128 if (!isDestroyed()) {
129 if (--_count <= 0) {
130 destroy();
131 setDestroyed();
132 }
133 }
134 }
135
136 /***
137 * Determines if this has been destroyed.
138 *
139 * @return <code>true</code> if this has been destroyed
140 */
141 protected boolean isDestroyed() {
142 return (_count < 0);
143 }
144
145 /***
146 * Mark this as being destroyed.
147 */
148 protected void setDestroyed() {
149 _count = -1;
150 }
151
152 }