ReplicationConflictHandler


1   /* Copyright (C) 2004 - 2006  db4objects Inc.  http://www.db4o.com
2   
3   This file is part of the db4o open source object database.
4   
5   db4o is free software; you can redistribute it and/or modify it under
6   the terms of version 2 of the GNU General Public License as published
7   by the Free Software Foundation and as clarified by db4objects' GPL 
8   interpretation policy, available at
9   http://www.db4o.com/about/company/legalpolicies/gplinterpretation/
10  Alternatively you can write to db4objects, Inc., 1900 S Norfolk Street,
11  Suite 350, San Mateo, CA 94403, USA.
12  
13  db4o is distributed in the hope that it will be useful, but WITHOUT ANY
14  WARRANTY; without even the implied warranty of MERCHANTABILITY or
15  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
16  for more details.
17  
18  You should have received a copy of the GNU General Public License along
19  with this program; if not, write to the Free Software Foundation, Inc.,
20  59 Temple Place - Suite 330, Boston, MA  02111-1307, USA. */
21  package com.db4o.replication;
22  
23  import com.db4o.*;
24  
25  /**
26   * will be called by a {@link com.db4o.replication.ReplicationProcess}upon
27   * replication conflicts. Conflicts occur whenever
28   * {@link ReplicationProcess#replicate(Object)}is called with an object that
29   * was modified in both ObjectContainers since the last replication run between
30   * the two.
31   */
32  public interface ReplicationConflictHandler {
33  
34      /**
35       * the callback method to be implemented to resolve a conflict. <br>
36       * <br>
37       * 
38       * @param replicationProcess
39       *            the {@link ReplicationProcess}for which this
40       *            ReplicationConflictHandler is registered
41       * @param a
42       *            the object modified in the peerA ObjectContainer
43       * @param b
44       *            the object modified in the peerB ObjectContainer
45       * @return the object (a or b) that should prevail in the conflict or null,
46       *         if no action is to be taken. If this would violate the direction
47       *         set with
48       *         {@link ReplicationProcess#setDirection(ObjectContainer, ObjectContainer)}
49       *         no action will be taken.
50       * @see ReplicationProcess#peerA()
51       * @see ReplicationProcess#peerB()
52       */
53      public Object   resolveConflict(ReplicationProcess replicationProcess,
54              Object   a, Object   b);
55  
56  }
57
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