SequenceIdAllocator


1   /**
2    * Copyright (C) 2004 France Telecom R&D
3    *
4    * This library is free software; you can redistribute it and/or
5    * modify it under the terms of the GNU Lesser General Public
6    * License as published by the Free Software Foundation; either
7    * version 2 of the License, or (at your option) any later version.
8    *
9    * This library is distributed in the hope that it will be useful,
10   * but WITHOUT ANY WARRANTY; without even the implied warranty of
11   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
12   * Lesser General Public License for more details.
13   *
14   * You should have received a copy of the GNU Lesser General Public
15   * License along with this library; if not, write to the Free Software
16   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
17   */
18  package org.objectweb.jorm.facility.naming.rdbsequence;
19  
20  /**
21   * Defines an identifier allocator based on a SQL sequence. This permits to
22   * support the inheritance with the use of a SQL sequence. Indeed, an identifier
23   * value MUST permit to find the class type of the persistent object. Then a way
24   * respect this constraint and to have an identifier allocation based on a
25   * sequence, is to modify the long value provided by the sequence in order to
26   * code the class identifier into the object identifier. This can be done by
27   * using one or several bits of the long value (in low or high position) for
28   * example.
29   *
30   * @author S.Chassande-Barrioz
31   */
32  public interface SequenceIdAllocator {
33  
34      /**
35       * Allocate an identifier from a new computed sequence value, and the naming
36       * key of the persistant class.
37       * @param key is the value that you have put in the 'inheritance-key'
38       * extension.
39       */
40      long allocateId(long seqValue, Object   key);
41  
42  }
43

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