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Java > Open Source Codes > ProductId


1 /*
2  * This file belongs to the XQuark distribution.
3  * Copyright (C) 2003 Universite de Versailles Saint-Quentin.
4  *
5  * This program is free software; you can redistribute it and/or
6  * modify it under the terms of the GNU Lesser General Public
7  * License as published by the Free Software Foundation; either
8  * version 2.1 of the License, or (at your option) any later version.
9  *
10  * This program is distributed in the hope that it will be useful,
11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13  * Lesser General Public License for more details.
14  *
15  * You should have received a copy of the GNU Lesser General Public
16  * License along with this program; if not, write to the Free Software
17  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307.
18  * You can also get it at http://www.gnu.org/licenses/lgpl.html
19  *
20  * For more information on this software, see http://www.xquark.org.
21  */
22
23 import org.xquark.mapping.*;
24 import java.sql.*;
25 import java.math.*;
26
27 /* SAMPLE NOTE:
28  *
29  * This example shows a generic method for primary/foreign key generation.
30  * This may not be the best method for your favourite database. For instance,
31  * with Oracle you may prefer using a sequence.
32  */
33
34 public class ProductId implements UserGenerator {
35     private static int counter = -1;
36
37     public String JavaDoc getXMLType() {
38         return "int";
39     }
40
41     public synchronized Object JavaDoc getValue(StorageContext context) {
42         if (counter < 0)
43             initCounter(context.getConnection());
44         return new BigDecimal(++counter);
45     }
46     
47     void initCounter(Connection connection) {
48         ResultSet rs = null;
49         Statement statement = null;
50         try {
51             statement = connection.createStatement();
52             try {
53                 rs = statement.executeQuery("select max(\"id\") from \"product\"");
54             } catch (SQLException ex) {
55                 rs = statement.executeQuery("select max(id) from product");
56             }
57             Object JavaDoc result = null;
58             while (rs.next()) {
59                 counter = rs.getInt(1);
60             }
61         }
62         catch (SQLException ex) {
63             ex.printStackTrace();
64         }
65         finally {
66             try {
67                 if (rs != null)
68                     rs.close();
69                 if (statement != null)
70                     statement.close();
71             }
72             catch (SQLException ex) {
73                 // no op
74 }
75         }
76     }
77 }
78
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