1 /*
2 * $Source$
3 * $Revision$
4 *
5 * Copyright (C) 2000 William Chesters
6 *
7 * Part of Melati (http://melati.org), a framework for the rapid
8 * development of clean, maintainable web applications.
9 *
10 * Melati is free software; Permission is granted to copy, distribute
11 * and/or modify this software under the terms either:
12 *
13 * a) the GNU General Public License as published by the Free Software
14 * Foundation; either version 2 of the License, or (at your option)
15 * any later version,
16 *
17 * or
18 *
19 * b) any version of the Melati Software License, as published
20 * at http://melati.org
21 *
22 * You should have received a copy of the GNU General Public License and
23 * the Melati Software License along with this program;
24 * if not, write to the Free Software Foundation, Inc.,
25 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA to obtain the
26 * GNU General Public License and visit http://melati.org to obtain the
27 * Melati Software License.
28 *
29 * Feel free to contact the Developers of Melati (http://melati.org),
30 * if you would like to work out a different arrangement than the options
31 * outlined here. It is our intention to allow Melati to be used by as
32 * wide an audience as possible.
33 *
34 * This program is distributed in the hope that it will be useful,
35 * but WITHOUT ANY WARRANTY; without even the implied warranty of
36 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
37 * GNU General Public License for more details.
38 *
39 * Contact details for copyright holder:
40 *
41 * William Chesters <williamc At paneris.org>
42 * http://paneris.org/~williamc
43 * Obrechtstraat 114, 2517VX Den Haag, The Netherlands
44 */
45
46 package org.melati.poem;
47
48 import java.sql.SQLException;
49 import java.sql.ResultSet;
50 import java.sql.PreparedStatement;
51 import java.sql.Connection;
52 import org.melati.poem.util.CachedIndexFactory;
53
54 /**
55 * Maintains a cache of <code>PreparedStatement</code>s for an SQL
56 * statement string.
57 * <p>
58 * The cached contents are discarded if the database structure has
59 * changed since the cache was created.
60 * <p>
61 * Execution of the statement in a transaction reflects uncommitted
62 * changes in that transaction.
63 * <p>
64 * The supertype dictates that connections can be identified
65 * by index, but this is slightly complicated and the additional
66 * methods rely on transactions instead.
67 */
68
69 public class PreparedStatementFactory extends CachedIndexFactory {
70
71
72 private Database database;
73 private long structureSerial;
74 private String sql;
75
76 /**
77 * Constructor.
78 * @param database the db we are working with
79 * @param sql the SQL statement
80 */
81 public PreparedStatementFactory(Database database, String sql) {
82 this.database = database;
83 this.structureSerial = database.structureSerial();
84 this.sql = sql;
85 }
86
87 /**
88 * Obtain a fresh <code>PreparedStatement</code> for a connection
89 * identified by an index.
90 * <p>
91 * The index is zero for the committed connection and the
92 * transaction index plus 1 for current transactions.
93 */
94 protected Object reallyGet(int index) {
95 try {
96 @SuppressWarnings("resource") // this is wrong, IMHO
97 Connection c =
98 index == 0 ? database.getCommittedConnection()
99 : database.poemTransaction(index - 1).getConnection();
100 return c.prepareStatement(sql);
101 } catch (SQLException e) {
102 throw new SQLPoemException(e);
103 }
104 }
105
106 /**
107 * {@inheritDoc}
108 * @see org.melati.poem.util.CachedIndexFactory#get(int)
109 */
110 public Object get(int index) {
111 if (structureSerial != database.structureSerial()) {
112 invalidate();
113 structureSerial = database.structureSerial();
114 }
115
116 return super.get(index);
117 }
118
119 /**
120 * Get a new or cached PreparedStatement.
121 * @param transaction the PoemTransaction, can be null
122 * @return a new or cached PreparedStatement
123 */
124 public PreparedStatement preparedStatement(PoemTransaction transaction) {
125 return (PreparedStatement)get(transaction == null ? 0 : transaction.index + 1);
126 }
127
128 /**
129 * @return a new or cached PreparedStatement for the current PoemThread's transaction.
130 */
131 public final PreparedStatement preparedStatement() {
132 return preparedStatement(PoemThread.transaction());
133 }
134
135 protected ResultSet resultSet(SessionToken token,
136 PreparedStatement statement) {
137 try {
138 if (database.logSQL())
139 database.log(new SQLLogEvent("PS about to:" + statement.toString() + "(" + sql + ")"));
140
141 token.transaction.writeDown();
142
143 ResultSet rs = null;
144 /*
145 if (database.getDbms().toString()
146 .equals("org.melati.poem.dbms.MSAccess")){
147 // This is due to some uncontrollable
148 // lazy write caching.
149 // On my machine it is taking 4s to
150 // sync
151 boolean notDone = true;
152 int failCount = 0;
153 while (notDone) {
154 try {
155 rs = statement.executeQuery();
156 notDone = false;
157 } catch (SQLException e) {
158 try {
159 System.err.println("Sleeping");
160 Thread.sleep(1000);
161 failCount++;
162 } catch (InterruptedException e1) {
163 throw new PoemBugPoemException("Sleep interrupted");
164 }
165 if (failCount > 8) {
166 throw new PreparedSQLSeriousPoemException(
167 statement, e);
168 }
169 }
170 }
171 } else
172 */
173 rs = statement.executeQuery();
174 token.toTidy().add(rs);
175 database.incrementQueryCount(statement.toString());
176 return rs;
177 } catch (SQLException e) {
178 throw new PreparedSQLSeriousPoemException(statement, e);
179 }
180 }
181
182 protected final ResultSet resultSet(SessionToken token) {
183 return resultSet(token, preparedStatement(token.transaction));
184 }
185
186 /**
187 * @return the ResultSet from the PreparedStatement of the PoemThread
188 */
189 public final ResultSet resultSet() {
190 return resultSet(PoemThread.sessionToken());
191 }
192
193 /**
194 * {@inheritDoc}
195 * @see java.lang.Object#toString()
196 */
197 public String toString() {
198
199 return super.toString() + " (SQL: " + sql + ")";
200 }
201
202 }