/*
* Copyright 2002-2008 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.jdbc.support.incrementer;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import javax.sql.DataSource;
import org.springframework.dao.DataAccessException;
import org.springframework.dao.DataAccessResourceFailureException;
import org.springframework.jdbc.datasource.DataSourceUtils;
import org.springframework.jdbc.support.JdbcUtils;
/**
* {@link DataFieldMaxValueIncrementer} that increments the maximum value of a given MySQL table
* with the equivalent of an auto-increment column. Note: If you use this class, your MySQL
* key column should <i>NOT</i> be auto-increment, as the sequence table does the job.
*
* <p>The sequence is kept in a table; there should be one sequence table per
* table that needs an auto-generated key. The table type of the sequence table
* should be MyISAM so the sequences are allocated without regard to any
* transactions that might be in progress.
*
* <p>Example:
*
* <pre class="code">create table tab (id int unsigned not null primary key, text varchar(100));
* create table tab_sequence (value int not null) type=MYISAM;
* insert into tab_sequence values(0);</pre>
*
* If "cacheSize" is set, the intermediate values are served without querying the
* database. If the server or your application is stopped or crashes or a transaction
* is rolled back, the unused values will never be served. The maximum hole size in
* numbering is consequently the value of cacheSize.
*
* @author Jean-Pierre Pawlak
* @author Thomas Risberg
* @author Juergen Hoeller
*/
public class MySQLMaxValueIncrementer extends AbstractColumnMaxValueIncrementer {
/** The SQL string for retrieving the new sequence value */
private static final String VALUE_SQL = "select last_insert_id()";
/** The next id to serve */
private long nextId = 0;
/** The max id to serve */
private long maxId = 0;
/**
* Default constructor for bean property style usage.
* @see #setDataSource
* @see #setIncrementerName
* @see #setColumnName
*/
public MySQLMaxValueIncrementer() {
}
/**
* Convenience constructor.
* @param dataSource the DataSource to use
* @param incrementerName the name of the sequence/table to use
* @param columnName the name of the column in the sequence table to use
*/
public MySQLMaxValueIncrementer(DataSource dataSource, String incrementerName, String columnName) {
super(dataSource, incrementerName, columnName);
}
@Override
protected synchronized long getNextKey() throws DataAccessException {
if (this.maxId == this.nextId) {
/*
* Need to use straight JDBC code because we need to make sure that the insert and select
* are performed on the same connection (otherwise we can't be sure that last_insert_id()
* returned the correct value)
*/
Connection con = DataSourceUtils.getConnection(getDataSource());
Statement stmt = null;
try {
stmt = con.createStatement();
DataSourceUtils.applyTransactionTimeout(stmt, getDataSource());
// Increment the sequence column...
String columnName = getColumnName();
stmt.executeUpdate("update "+ getIncrementerName() + " set " + columnName +
" = last_insert_id(" + columnName + " + " + getCacheSize() + ")");
// Retrieve the new max of the sequence column...
ResultSet rs = stmt.executeQuery(VALUE_SQL);
try {
if (!rs.next()) {
throw new DataAccessResourceFailureException("last_insert_id() failed after executing an update");
}
this.maxId = rs.getLong(1);
}
finally {
JdbcUtils.closeResultSet(rs);
}
this.nextId = this.maxId - getCacheSize() + 1;
}
catch (SQLException ex) {
throw new DataAccessResourceFailureException("Could not obtain last_insert_id()", ex);
}
finally {
JdbcUtils.closeStatement(stmt);
DataSourceUtils.releaseConnection(con, getDataSource());
}
}
else {
this.nextId++;
}
return this.nextId;
}
}
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