JdbcKeyGenerator


1   
2   /*
3    * Copyright (c) 1998 - 2005 Versant Corporation
4    * All rights reserved. This program and the accompanying materials
5    * are made available under the terms of the Eclipse Public License v1.0
6    * which accompanies this distribution, and is available at
7    * http://www.eclipse.org/legal/epl-v10.html
8    *
9    * Contributors:
10   * Versant Corporation - initial API and implementation
11   */
12  package com.versant.core.jdbc;
13  
14  import com.versant.core.jdbc.metadata.JdbcTable;
15  
16  import java.sql.Connection  ;
17  import java.sql.SQLException  ;
18  import java.sql.Statement  ;
19  import java.util.HashSet  ;
20  
21  /**
22   * These generate primary keys for new rows in tables. Instances must be
23   * thread safe.
24   */
25  public interface JdbcKeyGenerator {
26  
27      /**
28       * Add any JdbcTable instances that this key generator requires to the
29       * supplied set. This method is called once per key generator during meta
30       * data generation. Any tables returned will be added to the meta data and
31       * will get into SQL scripts and so on. If the same key generator
32       * instance is returned more than once by a factory then this method
33       * will still only be called once on the instance.
34       */
35      public void addKeyGenTables(HashSet   set, JdbcMetaDataBuilder mdb);
36  
37      /**
38       * If the new key can only be detirmined after the new row has been
39       * inserted (e.g. if using a database autoincrement column) then this
40       * should return true.
41       */
42      public boolean isPostInsertGenerator();
43  
44      /**
45       * Initialize this key generator. This is called when the JDO Genie
46       * server initializes before any keys are generated. Key
47       * generators should use this to avoid popular race conditions and
48       * deadlock opportunities (e.g. multiple 'select max(id) from table'
49       * statements executing at the same time). If the same key generator
50       * instance is used on more than one class this will be called once
51       * for each class.
52       *
53       * @param className  The name of the class
54       * @param classTable The table for the class
55       * @param con        Connection to the DataSource for the class
56       */
57      public void init(String   className, JdbcTable classTable,
58              Connection   con) throws SQLException  ;
59  
60      /**
61       * Does this key generator require its own connection? If it does then
62       * one will be obtained to generate the key and committed after the
63       * key has been generated. This is called prior to every key generation
64       * call.
65       */
66      public boolean isRequiresOwnConnection();
67  
68      /**
69       * Generate a new primary key value for a new instance of the supplied
70       * class prior to the row being inserted. The values generated will be used
71       * to populate a new OID and then set on a PreparedStatement for the
72       * insert. This is called if isPostInsertGenerator returns false.<p>
73       * <p/>
74       * The newObjectCount parameter indicates the number of new objects that
75       * will be inserted (including this one) in the same transaction using
76       * this key generator. This may be used to optimize the behavior of the
77       * key generator or be ignored. The highlow key generator uses this value
78       * instead of its grabSize to avoid executing redundant updates and
79       * selects.<p>
80       *
81       * @param className      The name of the class
82       * @param classTable     The table for the class
83       * @param newObjectCount The number of new objects being created
84       * @param data           The array to store the key values in.
85       * @param con            Connection to the DataSource for the class.
86       * @throws SQLException on errors
87       */
88      public void generatePrimaryKeyPre(String   className,
89              JdbcTable classTable, int newObjectCount, Object  [] data,
90              Connection   con) throws SQLException  ;
91  
92      /**
93       * Get extra SQL to be appended to the insert statement. This is only
94       * called for post insert key generators. Return null if no extra SQL
95       * is required. Key generators can use this as an alternative to running
96       * a separate query to get the primary key for the just inserted row.
97       */
98      public String   getPostInsertSQLSuffix(JdbcTable classTable);
99  
100     /**
101      * Generate a new primary key value for a new instance of the supplied
102      * class after the row has been inserted. The values generated will be used
103      * to populate a new OID and then set on a PreparedStatement for the
104      * insert.  This is called if isPostInsertGenerator returns true.
105      *
106      * @param className  The name of the class
107      * @param classTable The table for the class
108      * @param data       The array to store the key values in.
109      * @param con        Connection to the DataSource for the class.
110      * @param stat       Statement created from con. Do not close it. This will have
111      *                   just been used to insert the new row.
112      * @throws SQLException on errors
113      */
114     public void generatePrimaryKeyPost(String   className,
115             JdbcTable classTable, Object  [] data,
116             Connection   con, Statement   stat) throws SQLException  ;
117 
118 }
119
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