/*
* Copyright 2002-2018 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;
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 NOT be auto-increment, as the sequence table does the job.
The sequence is kept in a table; there should be one sequence table per
table that needs an auto-generated key. The storage engine used by the sequence table
can be MYISAM or INNODB since the sequences are allocated using a separate connection
without being affected by any other transactions that might be in progress.
Example:
create table tab (id int unsigned not null primary key, text varchar(100));
create table tab_sequence (value int not null);
insert into tab_sequence values(0);
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.
It is possible to avoid acquiring a new connection for the incrementer by setting the
"useNewConnection" property to false. In this case you MUST use a non-transactional
storage engine like MYISAM when defining the incrementer table.
Author: Jean-Pierre Pawlak, Thomas Risberg, Juergen Hoeller
/**
* {@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 storage engine used by the sequence table
* can be MYISAM or INNODB since the sequences are allocated using a separate connection
* without being affected by any other 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);
* 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.
*
* <p>It is possible to avoid acquiring a new connection for the incrementer by setting the
* "useNewConnection" property to false. In this case you <i>MUST</i> use a non-transactional
* storage engine like MYISAM when defining the incrementer table.
*
* @author Jean-Pierre Pawlak
* @author Thomas Risberg
* @author Juergen Hoeller
*/
public class MySQLMaxValueIncrementer extends AbstractColumnMaxValueIncrementer {
The SQL string for retrieving the new sequence value. /** The SQL string for retrieving the new sequence value. */
private static final String VALUE_SQL = "select last_insert_id()";
The next id to serve. /** The next id to serve. */
private long nextId = 0;
The max id to serve. /** The max id to serve. */
private long maxId = 0;
Whether or not to use a new connection for the incrementer. /** Whether or not to use a new connection for the incrementer. */
private boolean useNewConnection = true;
Default constructor for bean property style usage.
See Also:
/**
* Default constructor for bean property style usage.
* @see #setDataSource
* @see #setIncrementerName
* @see #setColumnName
*/
public MySQLMaxValueIncrementer() {
}
Convenience constructor.
Params: - dataSource – the DataSource to use
- incrementerName – the name of the sequence table to use
- columnName – the name of the column in the sequence table to use
/**
* 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);
}
Set whether to use a new connection for the incrementer.
true is necessary to support transactional storage engines, using an isolated separate transaction for the increment operation. false is sufficient if the storage engine of the sequence table is non-transactional (like MYISAM), avoiding the effort of acquiring an extra Connection for the increment operation.
Default is true since Spring Framework 5.0.
See Also: Since: 4.3.6
/**
* Set whether to use a new connection for the incrementer.
* <p>{@code true} is necessary to support transactional storage engines,
* using an isolated separate transaction for the increment operation.
* {@code false} is sufficient if the storage engine of the sequence table
* is non-transactional (like MYISAM), avoiding the effort of acquiring an
* extra {@code Connection} for the increment operation.
* <p>Default is {@code true} since Spring Framework 5.0.
* @since 4.3.6
* @see DataSource#getConnection()
*/
public void setUseNewConnection(boolean useNewConnection) {
this.useNewConnection = useNewConnection;
}
@Override
protected synchronized long getNextKey() throws DataAccessException {
if (this.maxId == this.nextId) {
/*
* If useNewConnection is true, then we obtain a non-managed connection so our modifications
* are handled in a separate transaction. If it is false, then we use the current transaction's
* connection relying on the use of a non-transactional storage engine like MYISAM for the
* incrementer table. We also 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 = null;
Statement stmt = null;
boolean mustRestoreAutoCommit = false;
try {
if (this.useNewConnection) {
con = getDataSource().getConnection();
if (con.getAutoCommit()) {
mustRestoreAutoCommit = true;
con.setAutoCommit(false);
}
}
else {
con = DataSourceUtils.getConnection(getDataSource());
}
stmt = con.createStatement();
if (!this.useNewConnection) {
DataSourceUtils.applyTransactionTimeout(stmt, getDataSource());
}
// Increment the sequence column...
String columnName = getColumnName();
try {
stmt.executeUpdate("update " + getIncrementerName() + " set " + columnName +
" = last_insert_id(" + columnName + " + " + getCacheSize() + ")");
}
catch (SQLException ex) {
throw new DataAccessResourceFailureException("Could not increment " + columnName + " for " +
getIncrementerName() + " sequence table", ex);
}
// 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);
if (con != null) {
if (this.useNewConnection) {
try {
con.commit();
if (mustRestoreAutoCommit) {
con.setAutoCommit(true);
}
}
catch (SQLException ignore) {
throw new DataAccessResourceFailureException(
"Unable to commit new sequence value changes for " + getIncrementerName());
}
JdbcUtils.closeConnection(con);
}
else {
DataSourceUtils.releaseConnection(con, getDataSource());
}
}
}
}
else {
this.nextId++;
}
return this.nextId;
}
}