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1   /*
2    * Copyright 2005 The Apache Software Foundation.
3    * 
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * You may obtain a copy of the License at 
7    * 
8    *     http://www.apache.org/licenses/LICENSE-2.0
9    * 
10   * Unless required by applicable law or agreed to in writing, software 
11   * distributed under the License is distributed on an "AS IS" BASIS, 
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
13   * See the License for the specific language governing permissions and 
14   * limitations under the License.
15   */
16  
17  /*
18   * InstanceCallbacks.java
19   *
20   */
21   
22  package javax.jdo;
23  
24  /*** A <code>PersistenceCapable</code> class that provides callback methods for life
25   * cycle events implements this interface.
26   *
27   * <P>For JDO 2.0, <code>InstanceCallbacks</code> has been refactored to extend 
28   * four other interfaces, without changing any of the methods or semantics. 
29   * This allows fine-grained control over callbacks, for
30   * example to allow a class to implement the load callback without
31   * implementing any of the other callbacks. For backward compatibility
32   * with JDO 1.0, the <code>InstanceCallbacks</code> interface is preserved.
33   *
34   * <P>Classes which include non-persistent fields whose values depend
35   * on the values of persistent fields require callbacks on specific
36   * JDO instance life cycle events in order to correctly populate the
37   * values in these fields.
38   *
39   * <P>The callbacks might also be used if the persistent instances
40   * need to be put into the runtime infrastructure of the application.
41   * For example, a persistent instance might notify other instances
42   * on changes to state.  The persistent instance might be in a list of
43   * managed instances. When the persistent instance is made hollow,
44   * it can no longer generate change events, and the persistent
45   * instance should be removed from the list of managed instances.
46   *
47   * <P>To implement this, the application programmer would implement
48   * <code>jdoPostLoad</code> to put itself into the list of managed
49   * instances, and implement <code>jdoPreClear</code> to remove itself from
50   * the list. With JDO 1.0, the domain class would be declared to implement
51   * <code>InstanceCallbacks</code>. With JDO 2.0, the domain class 
52   * would be declared to implement
53   * <code>javax.jdo.listener.LoadCallback</code> and 
54   * <code>javax.jdo.listener.ClearCallback</code>.
55   *
56   * <P>Note that JDO does not manage the state of non-persistent
57   * fields, and when a JDO instance transitions to hollow, JDO clears
58   * the persistent fields.  It is the programmer's responsibility to
59   * clear non-persistent fields so that garbage collection of
60   * referred instances can occur.
61   *
62   * @since 1.0
63   * @version 2.0
64   */
65  public interface InstanceCallbacks 
66      extends javax.jdo.listener.ClearCallback, 
67          javax.jdo.listener.DeleteCallback,
68          javax.jdo.listener.LoadCallback,
69          javax.jdo.listener.StoreCallback {
70  }