web server - Borland Technical Publications

Implementing primary key generation by the CMP engine
JDataStore JDBC3: using useGetGeneratedKeys
Borland's JDataStore supports the new JDBC3 method
java.sql.Statement.getGeneratedKeys(). This method is used to obtain primary key
values from newly inserted rows. No additional coding is necessary, but note that this
method is unsupported in other databases and is recommended for use only with
Borland JDataStore. To use this method, set the boolean property useGetGeneratedKeys
to True.
Automatic primary key generation using named sequence tables
Note
A named sequence table is used to support auto primary key generation when the
underlying database (such as Oracle SEQUENCE) and the JDBC driver (AUTOINCREMENT in
JDBC 3.0) do not support key generation. The named sequence table allows you to
specify a table that holds a key to use for primary key generation. The container uses
this table to generate the keys.
The table must contain a single row with a single column
To use the name sequence table your table must have a single row with a single
column that is an integer (for the sequence values). You must create a table with one
column named “SEQUENCE” with any initial value. For example:
CREATE TABLE TAB_A_SEQ (SEQUENCE int);
INSERT into TAB_A_SEQ values (10);
In this example key generation starts from value 10.
To enable this feature, set it in in ejb-borland.xml:
TABLE_A
ID
autoPkGenerator
java.lang.String
NAMEDSEQUENCETABLE
namedSequenceTableName
java.lang.String
TAB_A_SEQ
keyCacheSize
java.lang.Integer
2
......
Note that “ID” is the primary key column, which is marked for auto Pk Generation using
NAMEDSEQUENCETABLE. The table used is TAB_A_SEQ.
Set the ejb.CacheCreate property to false while using getPrimaryKeyAfterInsert or
useGetGeneratedKeys. The container needs to know the primary key to dispatch calls to
the bean instance. Therefore, it needs to know the primary key at the same time the
Create method returns.
Chapter 18: Generating Entity Bean Primary Keys 165