How to intercept update on entity object using bc4j

Question

Hi all,
I need to intercept a user from updating a particular entity object and create a new entity instead. I have a particular row in a database table that has a primary key with special meaning. If a user attempts to update this row, I want to automatically create a new row in the table with the information they entered and leave the original row unmodified. Any suggestions on how to do this at the entity layer?
Thanks
Mike

Answer 1

Hi Sung,
I've created 2 Entity Objects, named TestEo and OtherEo. The logic I've included is as follows: Before posting data for TestEo to the database (thus as part of the prepareForDML), I create a new instance of OtherEo, using the createBlankInstance method exposed on OtherEoDefImpl.
However, the instance thus created ends up in a STATUS_UNMODIFIED, regardless of locking mode (I've managed to eliminate the locking mode as an issue).
Could you give me an idea of where I'm going wrong? I've attached the prepareForDML() (with diagnostic msgs) and createBlankInstance() methods below.
TestEoImpl.prepareForDML()
protected void prepareForDML(int p0, TransactionEvent p1)
switch (this.getDBTransaction().getLockingMode())
case DBTransaction.LOCK_OPTIMISTIC:
System.out.println("Locking mode: LOCK_OPTIMISTIC");
break;
case DBTransaction.LOCK_PESSIMISTIC:
System.out.println("Locking mode: LOCK_PESSIMISTIC");
break;
// TODO: Override this oracle.jbo.server.EntityImpl method
super.prepareForDML(p0, p1);
OtherEoDefImpl otherEoDef = (OtherEoDefImpl) EntityDefImpl.findDefObject(
"testapp.OtherEo");
System.out.println("Entity Class: " + this.getClass().getName());
switch (this.getEntityState())
case EntityImpl.STATUS_DEAD:
System.out.println("Entity State: STATUS_DEAD");
break;
case EntityImpl.STATUS_DELETED:
System.out.println("Entity State: STATUS_DELETED");
break;
case EntityImpl.STATUS_INITIALIZED:
System.out.println("Entity State: STATUS_INITIALIZED");
break;
case EntityImpl.STATUS_MODIFIED:
System.out.println("Entity State: STATUS_MODIFIED");
break;
case EntityImpl.STATUS_NEW:
System.out.println("Entity State: STATUS_NEW");
break;
case EntityImpl.STATUS_UNMODIFIED:
System.out.println("Entity State: STATUS_UNMODIFIED");
break;
EntityImpl otherEo = otherEoDef.createBlankInstance(getDBTransaction());
System.out.println("Entity Class: " + otherEo.getClass().getName());
int state = otherEo.getEntityState();
switch (state)
case EntityImpl.STATUS_DEAD:
System.out.println("Entity State: STATUS_DEAD - " + state);
break;
case EntityImpl.STATUS_DELETED:
System.out.println("Entity State: STATUS_DELETED - " + state);
break;
case EntityImpl.STATUS_INITIALIZED:
System.out.println("Entity State: STATUS_INITIALIZED - " + state);
break;
case EntityImpl.STATUS_MODIFIED:
System.out.println("Entity State: STATUS_MODIFIED - " + state);
break;
case EntityImpl.STATUS_NEW:
System.out.println("Entity State: STATUS_NEW - " + state);
break;
case EntityImpl.STATUS_UNMODIFIED:
System.out.println("Entity State: STATUS_UNMODIFIED - " + state);
break;
OtherEoDefImpl.createBlankInstance()
public EntityImpl createBlankInstance(DBTransaction p0)
// TODO: Override this oracle.jbo.server.EntityDefImpl method
return super.createBlankInstance(p0);
Output - Test 1
Locking mode: LOCK_OPTIMISTIC
Entity Class: testapp.TestEoImpl
Entity State: STATUS_NEW
Entity Class: testapp.OtherEoImpl
Entity State: STATUS_UNMODIFIED - 1
Output - Test 2
Locking mode: LOCK_PESSIMISTIC
Entity Class: testapp.TestEoImpl
Entity State: STATUS_NEW
Entity Class: testapp.OtherEoImpl
Entity State: STATUS_UNMODIFIED - 1