Class MySQLMaxValueIncrementer

java.lang.Object

org.springframework.jdbc.support.incrementer.AbstractDataFieldMaxValueIncrementer

org.springframework.jdbc.support.incrementer.AbstractColumnMaxValueIncrementer

org.springframework.jdbc.support.incrementer.MySQLMaxValueIncrementer

All Implemented Interfaces:

org.springframework.beans.factory.InitializingBean, DataFieldMaxValueIncrementer

public class MySQLMaxValueIncrementer
extends AbstractColumnMaxValueIncrementer

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.

Note that MySQLMaxValueIncrementer is compatible with MySQL safe updates mode.

Author:

Jean-Pierre Pawlak, Thomas Risberg, Juergen Hoeller, Sam Brannen

Field Summary

Fields inherited from class AbstractDataFieldMaxValueIncrementer

paddingLength

Constructor Summary

Constructors

Constructor	Description
MySQLMaxValueIncrementer()	Default constructor for bean property style usage.
MySQLMaxValueIncrementer(DataSource dataSource, String incrementerName, String columnName)	Convenience constructor.

Method Summary

Modifier and Type	Method	Description
protected long	getNextKey()	Determine the next key to use, as a long.
void	setUseNewConnection(boolean useNewConnection)	Set whether to use a new connection for the incrementer.

Methods inherited from class AbstractColumnMaxValueIncrementer

afterPropertiesSet, getCacheSize, getColumnName, setCacheSize, setColumnName

Methods inherited from class AbstractDataFieldMaxValueIncrementer

getDataSource, getIncrementerName, getPaddingLength, nextIntValue, nextLongValue, nextStringValue, setDataSource, setIncrementerName, setPaddingLength

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

MySQLMaxValueIncrementer

public MySQLMaxValueIncrementer()

Default constructor for bean property style usage.

See Also:

• AbstractDataFieldMaxValueIncrementer.setDataSource(DataSource)
• AbstractDataFieldMaxValueIncrementer.setIncrementerName(String)
• AbstractColumnMaxValueIncrementer.setColumnName(String)

MySQLMaxValueIncrementer

public MySQLMaxValueIncrementer(DataSource dataSource,
 String incrementerName,
 String columnName)

Convenience constructor.

Parameters:

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

Method Details

setUseNewConnection

public void setUseNewConnection(boolean useNewConnection)

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:

4.3.6

See Also:

• DataSource.getConnection()

getNextKey

protected long getNextKey()
                   throws org.springframework.dao.DataAccessException

Description copied from class: AbstractDataFieldMaxValueIncrementer

Determine the next key to use, as a long.

Specified by:

getNextKey in class AbstractDataFieldMaxValueIncrementer

Returns:

the key to use as a long. It will eventually be converted later in another format by the public concrete methods of this class.

Throws:

org.springframework.dao.DataAccessException