Sequencing


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21  // Copyright (c) 1998, 2005, Oracle. All rights reserved.  
22  package oracle.toplink.essentials.internal.sequencing;
23  
24  
25  /**
26   * <p>
27   * <b>Purpose</b>: Define interface to use sequencing.
28   * <p>
29   * <b>Description</b>: This interface accessed through Session.getSequencing() method.
30   * Used by TopLink internals to obtain sequencing values.
31   * <p>
32   * <b>Responsibilities</b>:
33   * <ul>
34   * <li> Provides sequencing objects and supporting APIs.
35   * </ul>
36   */
37  public interface Sequencing {
38      // Possible return values for whenShouldAcquireValueForAll() method:
39      // all classes should acquire sequencing value before insert;
40      public static final int BEFORE_INSERT = -1;
41  
42      // some classes should acquire sequencing value before insert, some after;
43      public static final int UNDEFINED = 0;
44  
45      // all classes should acquire sequencing value after insert;
46      public static final int AFTER_INSERT = 1;
47  
48      /**
49      * INTERNAL:
50      * Indicates when sequencing value should be acqiured for all classes.
51      * There are just three possible return values:
52      * BEFORE_INSERT, UNDEFINED, AFTER_INSERT.
53      * Used as a shortcut to avoid individual checks for each class:
54      * shouldAcquireValueAfterInsert(Class cls).
55      * Currently UNDEFINED only happens in a case of a SessionBroker:
56      * session1 - BEFORE_INSERT, session2 - AFTER_INSERT
57      */
58      public int whenShouldAcquireValueForAll();
59  
60      /**
61      * INTERNAL:
62      * Indicates whether sequencing value should be acqiured
63      * before or after INSERT
64      */
65      public boolean shouldAcquireValueAfterInsert(Class   cls);
66  
67      /**
68      * INTERNAL:
69      * Indicates whether existing attribute value should be overridden.
70      * This method is called in case an attribute mapped to PK of sequencing-using
71      * descriptor contains non-null value.
72      * @param seqName String is sequencing number field name
73      * @param existingValue Object is a non-null value of PK-mapped attribute.
74      */
75      public boolean shouldOverrideExistingValue(Class   cls, Object   existingValue);
76  
77      /**
78      * INTERNAL:
79      * Return the newly-generated sequencing value.
80      * @param cls Class for which the sequencing value is generated.
81      */
82      public Object   getNextValue(Class   cls);
83  }
84
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