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Java > Open Source Codes > org > jboss > ejb > plugins > lock > JDBCOptimisticLock


1 /*
2 * JBoss, Home of Professional Open Source
3 * Copyright 2005, JBoss Inc., and individual contributors as indicated
4 * by the @authors tag. See the copyright.txt in the distribution for a
5 * full listing of individual contributors.
6 *
7 * This is free software; you can redistribute it and/or modify it
8 * under the terms of the GNU Lesser General Public License as
9 * published by the Free Software Foundation; either version 2.1 of
10 * the License, or (at your option) any later version.
11 *
12 * This software is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Lesser General Public License for more details.
16 *
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with this software; if not, write to the Free
19 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
20 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
21 */
22 package org.jboss.ejb.plugins.lock;
23
24
25 /**
26  * This class is an optmistic lock implementation.
27  * It locks tableFields and their values during transaction.
28  * Locked tableFields and their values are added to the WHERE clause of the
29  * UPDATE SQL statement when entity is stored.
30  * The following strategies are supported:
31  * - fixed group of tableFields
32  * Fixed group of tableFields is used for locking . The tableFields and their values are
33  * locked at the beginning of a transaction. The group name must match
34  * one of the entity's load-group-name.
35  * - modified strategy
36  * The tableFields that were modified during transaction are used as lock.
37  * All entity's field values are locked at the beginning of the transaction.
38  * The tableFields are locked only after its actual change.
39  * - read strategy
40  * The tableFields that were read/modified during transaction.
41  * All entity's field values are locked at the beginning of the transaction.
42  * The tableFields are locked only after they were accessed.
43  * - version-column strategy
44  * This adds additional version field of type java.lang.Long. Each update
45  * of the entity will increase the version value by 1.
46  * - timestamp-column strategy
47  * Adds additional timestamp column of type java.util.Date. Each update
48  * of the entity will set the field to the current time.
49  * - key-generator column strategy
50  * Adds additional column. The type is defined by user. The key generator
51  * is used to set the next value.
52  *
53  * Note: all optimistic locking related code should be rewritten when in the
54  * new CMP design.
55  *
56  * Note2: done.
57  *
58  * @author <a HREF="mailto:aloubyansky@hotmail.com">Alex Loubyansky</a>
59  * @version $Revision: 37459 $
60  */
61 public final class JDBCOptimisticLock
62    extends NoLock
63 {
64 }
65
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