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 2000-2004 (C) Exoffice Technologies Inc. All Rights Reserved.
42 */
43
44 package org.exolab.jms.persistence;
45
46
47 import java.sql.Connection;
48 import java.sql.PreparedStatement;
49 import java.sql.ResultSet;
50
51 import javax.sql.DataSource;
52
53
54 /***
55 * This class generates seeds
56 *
57 * @version $Revision: 1.6 $ $Date: 2004/01/11 02:35:45 $
58 * @author <a href="mailto:tima@intalio.com">Tim Anderson</a>
59 *
60 **/
61 public class SeedGenerator {
62
63 /***
64 * Caches the singleton instance of this class
65 */
66 private static SeedGenerator _instance;
67
68 /***
69 * Monitor used to synchronize the initialization of the
70 * singleton class instance
71 */
72 private static final Object _block = new Object();
73
74
75 /***
76 * Returns the singleton instance.
77 *
78 * Note that initialise() must have been invoked first for this
79 * to return a valid instance.
80 *
81 * @return SeedGenerator the singleton instance
82 */
83 public static SeedGenerator instance() {
84 return _instance;
85 }
86
87 /***
88 * Initialise the seed generator
89 *
90 * @return SeedGenerator the singleton instance
91 */
92 public static SeedGenerator initialise() {
93 if (_instance == null) {
94 synchronized (_block) {
95 if (_instance == null) {
96 _instance = new SeedGenerator();
97 }
98 }
99 }
100
101 return _instance;
102 }
103
104 /***
105 * Return the next seed value for the given name
106 *
107 * @param connection - the connection used
108 * @param seed - the name of the seed
109 * @return long - the next seed value
110 * @exception PersistenceException - if the seed cannot be retrieved
111 */
112 public synchronized long next(Connection connection, String name)
113 throws PersistenceException {
114
115 PreparedStatement select = null;
116 PreparedStatement update = null;
117 PreparedStatement insert = null;
118 ResultSet result = null;
119 long value = 0;
120
121 boolean successful = false;
122 try {
123 select = connection.prepareStatement(
124 "select * from seeds where name=?");
125 select.setString(1, name);
126
127 result = select.executeQuery();
128 if (result.next()) {
129 value = result.getLong("seed");
130 value++;
131 update = connection.prepareStatement(
132 "update seeds set seed=? where name=?");
133 update.setLong(1, value);
134 update.setString(2, name);
135 update.executeUpdate();
136 } else {
137 value = 1;
138 insert = connection.prepareStatement(
139 "insert into seeds values (?,?)");
140 insert.setString(1, name);
141 insert.setLong(2, value);
142 insert.executeUpdate();
143 }
144 } catch (Exception exception) {
145 throw new PersistenceException("next " + exception.getMessage());
146 } finally {
147 SQLHelper.close(select);
148 SQLHelper.close(update);
149 SQLHelper.close(insert);
150 SQLHelper.close(result);
151 }
152
153 return value;
154 }
155
156 /***
157 * Remove all seeds.
158 *
159 * @param connection - the connection to use
160 * @exception PersistenceException - is thrown if the request does not
161 * complete
162 */
163 public void removeAll(Connection connection)
164 throws PersistenceException {
165
166 PreparedStatement delete = null;
167 try {
168 delete = connection.prepareStatement("delete from seeds");
169 delete.executeUpdate();
170 } catch (Exception error) {
171 throw new PersistenceException("Failed in removeAll with " +
172 error.toString());
173 } finally {
174 SQLHelper.close(delete);
175 }
176 }
177
178 /***
179 * Issue a close, which in this case invalidates the singleton
180 * TODO: do we really need this
181 */
182 public void close() {
183 _instance = null;
184 }
185
186 /***
187 * Constructor
188 *
189 * @param connectionPool the connection pool
190 * @param manager the transaction manager
191 */
192 protected SeedGenerator() {
193 }
194 }