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.
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.
Jean-Pierre Pawlak, Thomas Risberg, Juergen Hoeller
public MySQLMaxValueIncrementer(javax.sql.DataSource dataSource,
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
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.