org.springframework.jdbc.support.incrementer

Class DerbyMaxValueIncrementer

  • All Implemented Interfaces:
    InitializingBean, DataFieldMaxValueIncrementer


    public class DerbyMaxValueIncrementer
    extends AbstractIdentityColumnMaxValueIncrementer
    DataFieldMaxValueIncrementer that increments the maximum value of a given Derby table with the equivalent of an auto-increment column. Note: If you use this class, your Derby key column should NOT be defined as an IDENTITY column, 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.

    Derby requires an additional column to be used for the insert since it is impossible to insert a null into the identity column and have the value generated. This is solved by providing the name of a dummy column that also must be created in the sequence table.

    Example:

    create table tab (id int not null primary key, text varchar(100));
     create table tab_sequence (value int generated always as identity, dummy char(1));
     insert into tab_sequence (dummy) values(null);
    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. HINT: Since Derby supports the JDBC 3.0 getGeneratedKeys method, it is recommended to use IDENTITY columns directly in the tables and then utilizing a KeyHolder when calling the with the update(PreparedStatementCreator psc, KeyHolder generatedKeyHolder) method of the JdbcTemplate.

    Thanks to Endre Stolsvik for the suggestion!

    Since:
    2.5
    Author:
    Thomas Risberg, Juergen Hoeller