Entity primary key and sequence - oracle

Question

i use oracle and openjpa.
i have an primary key and i want to use a sequence for its value
CREATE TABLE LOG (
ID NUMBER(10) not null,
TIMESTAMP TIMESTAMP DEFAULT (SYSDATE),
constraint PK_ID PRIMARY KEY (ID)
);
CREATE SEQUENCE ID_SEQ
START WITH 1
INCREMENT BY 1
NOCACHE
NOCYCLE;
#Entity
#Table(name="Log")
public class Log implements Serializable {
#Id
#SequenceGenerator(name="SEQ_GEN", sequenceName="ID_SEQ", allocationSize=1)
#GeneratedValue(strategy=GenerationType.SEQUENCE, generator="SEQ_GEN" )
#Column(name="id",nullable=false)
private long id;
#Column(name="timestamp",nullable=false)
private Timestamp timestamp;
public Log(){
}
public Log(Timestamp timestamp){
this.timestamp = timestamp;
}
..
}
#Stateless
public class LogDAO {
#PersistenceContext(unitName="logEntityPU")
private EntityManager em ;
#TransactionAttribute(TransactionAttributeType.REQUIRED)
public boolean insert(Log log){
em.persist(log);
return true;
}
...
...
}
when i check my Log object, id=0 and the timestamp is ok
but i get this error
ORA-01400: integrity constraint violation: NOT NULL check constraint.Insertion of null value not allowed
it's like jpa don't do the link with the sequence.
when i debug more, i see this error: javax.persistence.TransactionRequiredException: No active transaction for PuId=
any idea?

Answer 1

A trigger like this will insert the primary key if one is not provided by the app
CREATE OR REPLACE TRIGGER YOUR_SCHEMA.TRG_YOUR_TABLE
BEFORE INSERT
ON YOUR_SCHEMA.YOUR_TABLE
REFERENCING OLD AS OLD NEW AS NEW
FOR EACH ROW
DECLARE
PrimaryKeyId NUMBER;
BEGIN
IF :NEW.PRIMARY_KEY_ID IS NULL THEN
SELECT your_schema.seq_your_table.nextval
INTO :NEW.PRIMARY_KEY_ID
FROM dual;
END IF;
END YOUR_SCHEMA.TRG_YOUR_TABLE;
Then do a
Select YOUR_SCHEMA.seq_your_table.currval from dual;
to get the value