Hibernate + oracle sequence + trigger - oracle

Question

I have a table with an index auto filled by a trigger that use a sequence (Oracle database)
CREATE TABLE A
(
IDS NUMBER(10) NOT NULL
)
CREATE OR REPLACE TRIGGER A_TRG
BEFORE INSERT
ON A REFERENCING NEW AS New OLD AS Old
FOR EACH ROW
BEGIN
:new.IDS := A_SEQ.nextval;
END A_TRG;
/
I have a matching Java class:
Class A {
#Id
#SequenceGenerator(name = "aSequence", sequenceName = "A_SEQ", allocationSize = 1)
#GeneratedValue(generator = "aSequence", strategy = GenerationType.SEQUENCE)
#Column(name = "IDS")
Long id;
...
}
When I try to persist an instance of A like this:
EntityTransaction transaction = entityManager.getTransaction();
transaction.begin();
A a = new A();
Long id = getHibernateTemplate().save(a);
transaction.commit();
I get this problem:
ID in code returned by the save call = "X"
ID in database = "X+1"
Is there a way to setup Hibernate to let the database trigger create the ID ?
Thanks

Answer 1

Reponse found at HIbernate issue with Oracle Trigger for generating id from a sequence
I need to adapt my trigger to run only if no ID is given:
CREATE OR REPLACE TRIGGER A_TRG
BEFORE INSERT
ON A REFERENCING NEW AS New OLD AS Old
FOR EACH ROW
WHEN (New.IDS is null) -- (1)
BEGIN
:new.IDS := A_SEQ.nextval;
END A_TRG;
/
(1) this line allow Hibernate to manually call A_SEQ.nextVal to set the ID and then bypass the trigger else Hibernate will get the nextval for uselessly because the trigger will always reset the ID calling nextval again

Answer 2

In your class B you have #GeneratedValue(generator = "preferenceSequence") which not defined in the example that you have, it should be #GeneratedValue(generator = "bSequence")
By default hibernate allocation size is 50 the B: IDS=50 seems to suggest the mapping is picking the wrong sequence.