public class DerbyMaxValueIncrementer extends AbstractColumnMaxValueIncrementer
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!
Modifier and Type | Field and Description |
---|---|
private static java.lang.String |
DEFAULT_DUMMY_NAME
The default for dummy name
|
private java.lang.String |
dummyName
The name of the dummy column used for inserts
|
private int |
nextValueIndex
The next id to serve from the value cache
|
private long[] |
valueCache
The current cache of values
|
paddingLength
Constructor and Description |
---|
DerbyMaxValueIncrementer()
Default constructor for bean property style usage.
|
DerbyMaxValueIncrementer(javax.sql.DataSource dataSource,
java.lang.String incrementerName,
java.lang.String columnName)
Convenience constructor.
|
DerbyMaxValueIncrementer(javax.sql.DataSource dataSource,
java.lang.String incrementerName,
java.lang.String columnName,
java.lang.String dummyName)
Convenience constructor.
|
Modifier and Type | Method and Description |
---|---|
java.lang.String |
getDummyName()
Return the name of the dummy column.
|
protected long |
getNextKey()
Determine the next key to use, as a long.
|
void |
setDummyName(java.lang.String dummyName)
Set the name of the dummy column.
|
afterPropertiesSet, getCacheSize, getColumnName, setCacheSize, setColumnName
getDataSource, getIncrementerName, getPaddingLength, nextIntValue, nextLongValue, nextStringValue, setDataSource, setIncrementerName, setPaddingLength
private static final java.lang.String DEFAULT_DUMMY_NAME
private java.lang.String dummyName
private long[] valueCache
private int nextValueIndex
public DerbyMaxValueIncrementer()
public DerbyMaxValueIncrementer(javax.sql.DataSource dataSource, java.lang.String incrementerName, java.lang.String columnName)
dataSource
- the DataSource to useincrementerName
- the name of the sequence/table to usecolumnName
- the name of the column in the sequence table to usepublic DerbyMaxValueIncrementer(javax.sql.DataSource dataSource, java.lang.String incrementerName, java.lang.String columnName, java.lang.String dummyName)
dataSource
- the DataSource to useincrementerName
- the name of the sequence/table to usecolumnName
- the name of the column in the sequence table to usedummyName
- the name of the dummy column used for insertspublic void setDummyName(java.lang.String dummyName)
public java.lang.String getDummyName()
protected long getNextKey() throws DataAccessException
AbstractDataFieldMaxValueIncrementer
getNextKey
in class AbstractDataFieldMaxValueIncrementer
DataAccessException