TupleSerialKeyCreator


1   /*-
2    * See the file LICENSE for redistribution information.
3    *
4    * Copyright (c) 2000,2006 Oracle.  All rights reserved.
5    *
6    * $Id: TupleSerialKeyCreator.java,v 1.30 2006/10/30 21:14:07 bostic Exp $
7    */
8   
9   package com.sleepycat.bind.serial;
10  
11  import com.sleepycat.bind.tuple.TupleBase;
12  import com.sleepycat.bind.tuple.TupleInput;
13  import com.sleepycat.bind.tuple.TupleOutput;
14  import com.sleepycat.je.DatabaseEntry;
15  import com.sleepycat.je.DatabaseException;
16  import com.sleepycat.je.ForeignKeyNullifier;
17  import com.sleepycat.je.SecondaryDatabase;
18  import com.sleepycat.je.SecondaryKeyCreator;
19  
20  /**
21   * A abstract key creator that uses a tuple key and a serial data entry. This
22   * class takes care of serializing and deserializing the data entry, and
23   * converting the key entry to/from {@link TupleInput} and {@link TupleOutput}
24   * objects.
25   * The following abstract method must be implemented by a concrete subclass
26   * to create the index key using these objects
27   * <ul>
28   * <li> {@link #createSecondaryKey(TupleInput,Object,TupleOutput)} </li>
29   * </ul>
30   * <!-- begin JE only -->
31   * <p>If {@link com.sleepycat.je.ForeignKeyDeleteAction#NULLIFY} was
32   * specified when opening the secondary database, the following method must be
33   * overridden to nullify the foreign index key.  If NULLIFY was not specified,
34   * this method need not be overridden.</p>
35   * <ul>
36   * <li> {@link #nullifyForeignKey(Object)} </li>
37   * </ul>
38   * <!-- end JE only -->
39   *
40   * @author Mark Hayes
41   */
42  public abstract class TupleSerialKeyCreator extends TupleBase
43      implements SecondaryKeyCreator, ForeignKeyNullifier {
44  
45      protected SerialBinding dataBinding;
46  
47      /**
48       * Creates a tuple-serial key creator.
49       *
50       * @param classCatalog is the catalog to hold shared class information and
51       * for a database should be a {@link StoredClassCatalog}.
52       *
53       * @param dataClass is the data base class.
54       */
55      public TupleSerialKeyCreator(ClassCatalog classCatalog, Class   dataClass) {
56  
57          this(new SerialBinding(classCatalog, dataClass));
58      }
59  
60      /**
61       * Creates a tuple-serial key creator.
62       *
63       * @param dataBinding is the data binding.
64       */
65      public TupleSerialKeyCreator(SerialBinding dataBinding) {
66  
67          this.dataBinding = dataBinding;
68      }
69  
70      // javadoc is inherited
71      public boolean createSecondaryKey(SecondaryDatabase db,
72                                        DatabaseEntry primaryKeyEntry,
73                                        DatabaseEntry dataEntry,
74                                        DatabaseEntry indexKeyEntry)
75          throws DatabaseException {
76  
77          TupleOutput output = getTupleOutput(null);
78          TupleInput primaryKeyInput = entryToInput(primaryKeyEntry);
79          Object   dataInput = dataBinding.entryToObject(dataEntry);
80          if (createSecondaryKey(primaryKeyInput, dataInput, output)) {
81              outputToEntry(output, indexKeyEntry);
82              return true;
83          } else {
84              return false;
85          }
86      }
87  
88      // javadoc is inherited
89      public boolean nullifyForeignKey(SecondaryDatabase db,
90                                       DatabaseEntry dataEntry)
91          throws DatabaseException {
92  
93          Object   data = dataBinding.entryToObject(dataEntry);
94          data = nullifyForeignKey(data);
95          if (data != null) {
96              dataBinding.objectToEntry(data, dataEntry);
97              return true;
98          } else {
99              return false;
100         }
101     }
102 
103     /**
104      * Creates the index key entry from primary key tuple entry and
105      * deserialized data entry.
106      *
107      * @param primaryKeyInput is the {@link TupleInput} for the primary key
108      * entry, or null if no primary key entry is used to construct the index
109      * key.
110      *
111      * @param dataInput is the deserialized data entry, or null if no data
112      * entry is used to construct the index key.
113      *
114      * @param indexKeyOutput is the destination index key tuple.  For index
115      * keys which are optionally present, no tuple entry should be output to
116      * indicate that the key is not present or null.
117      *
118      * @return true if a key was created, or false to indicate that the key is
119      * not present.
120      */
121     public abstract boolean createSecondaryKey(TupleInput primaryKeyInput,
122                                                Object   dataInput,
123                                                TupleOutput indexKeyOutput);
124 
125     /**
126      * Clears the index key in the deserialized data entry.
127      *
128      * <p>On entry the data parameter contains the index key to be cleared.  It
129      * should be changed by this method such that {@link #createSecondaryKey}
130      * will return false.  Other fields in the data object should remain
131      * unchanged.</p>
132      *
133      * @param data is the source and destination deserialized data
134      * entry.
135      *
136      * @return the destination data object, or null to indicate that the
137      * key is not present and no change is necessary.  The data returned may
138      * be the same object passed as the data parameter or a newly created
139      * object.
140      */
141     public Object   nullifyForeignKey(Object   data) {
142 
143         return null;
144     }
145 }
146
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