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1   /* Copyright 2004, 2005 Acegi Technology Pty Limited
2    *
3    * Licensed under the Apache License, Version 2.0 (the "License");
4    * you may not use this file except in compliance with the License.
5    * You may obtain a copy of the License at
6    *
7    *     http://www.apache.org/licenses/LICENSE-2.0
8    *
9    * Unless required by applicable law or agreed to in writing, software
10   * distributed under the License is distributed on an "AS IS" BASIS,
11   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12   * See the License for the specific language governing permissions and
13   * limitations under the License.
14   */
15  
16  package org.acegisecurity.domain;
17  
18  import java.io.Serializable;
19  
20  
21  /***
22   * An interface that indicates an object is a <i>persistable entity</i>.
23   * 
24   * <p>
25   * A persistable entity is any object that is capable of being persisted,
26   * typically via a {@link org.acegisecurity.domain.dao.Dao} implementation.
27   * </p>
28   *
29   * @author Ben Alex
30   * @version $Id: PersistableEntity.java,v 1.2 2005/11/17 00:56:47 benalex Exp $
31   */
32  public interface PersistableEntity {
33      //~ Methods ================================================================
34  
35      /***
36       * Provides a common getter for the persistence layer to obtain an
37       * identity, irrespective of the actual type of identity used.
38       * 
39       * <p>
40       * Typically a subclass will delegate to a <code>public
41       * SomePrimitiveWrapper getId()</code> method. The necessity for the
42       * <code>getInternalId()</code> abstract method is solely  because the
43       * persistence layer needs a way of obtaining the identity irrespective of
44       * the actual identity implementation choice.
45       * </p>
46       * 
47       * <p>
48       * Returning <code>null</code> from this method will indicate the object
49       * has never been saved. This will likely be relied on by some
50       * <code>Dao</code> implementations.
51       * </p>
52       *
53       * @return the persistence identity of this instance
54       */
55      abstract Serializable getInternalId();
56  }