Source code: javatools/db/DbSequence.java
1 /*
2 Javatools (modified version) - Some useful general classes.
3 Copyright (C) 2002-2003 Chris Bitmead (original) Antonio Petrelli (modified)
4
5 This program is free software; you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation; either version 2 of the License, or
8 (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
13 GNU General Public License for more details.
14
15 You should have received a copy of the GNU General Public License
16 along with this program; if not, write to the Free Software
17 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
18
19 Contact me at: brenmcguire@users.sourceforge.net
20 */
21 package javatools.db;
22 import java.sql.*;
23 import java.io.*;
24 import javatools.util.FileLog;
25 import javatools.util.Props;
26 import javatools.util.SubstituteVariable;
27
28 /**
29 * Generates unique values for use as keys. Constructor is not public. Use
30 * DbDatabase.getSequence().
31 *
32 * @author Chris
33 * @created December 13, 2001
34 * @version 0.7
35 * @commentedby Antonio Petrelli
36 */
37
38 public class DbSequence {
39 /** The database to be used.
40 */
41 DbDatabase db;
42 /** The name for this sequence.
43 */
44 String name;
45
46 /** Creates a new DbSequence.
47 * @param db The database to use.
48 * @param name The name of this sequence.
49 */
50 DbSequence(DbDatabase db, String name) {
51 this.db = db;
52 this.name = name;
53 }
54
55 /** Gets the next value.
56 * @throws DbException If something goes wrong.
57 * @return The requested value.
58 */
59 public int next() throws DbException {
60 return next(db.getThreadConnection());
61 }
62
63 /** Returns the next value, with a specific connection.
64 * @param dbcon The connection to use.
65 * @throws DbException If something goes wrong.
66 * @return The needed value.
67 */
68 public int next(DbConnection dbcon) throws DbException {
69 try {
70 Connection con = dbcon.getSqlConnection();
71 Props props = Props.singleton("dbvendor");
72 String sql = props.getProperty(db.getProperty("vendor") + ".nextSequenceSql");
73 sql = SubstituteVariable.substitute(sql, "${name}", name);
74 FileLog.singleton().error("DbSequence.next", sql);
75 PreparedStatement ps = con.prepareStatement(sql);
76 ResultSet rs = ps.executeQuery();
77 if (!rs.next()) {
78 throw new DbException("Can't read " + name + " sequence");
79 }
80 int rtn = rs.getInt(1);
81 ps.close();
82 return rtn;
83 } catch (SQLException e) {
84 throw new DbException(e);
85 } catch (IOException e) {
86 throw new DbException(e);
87 }
88 }
89 }