change of subclasse causes error

[ruud1]

I have a baseclasse and several subclasses (A,B,C) all of them are saved in one table.

I need to convert from one to another subclasse. Lets say from A to B.

I have tried several things:

1 : create a new instance of B, read A from the database and perform a merge. I got the error :
A unexpected error : [javax.ejb.EJBException:null; CausedByException is:
Object with id: null was not of the specified subclass: com.hollandhouse.unispool.entity.beans.LPRDevice (class of the given object did not match class of persistent copy)].

2 : create a new instance of B, test whether the class of A and B are instanciated from different classes. If so : set B.id equal to A.id and persist. This also goes wrong.

I dont like the solution : read A, copy every attribute to B, delete A, create B with the id of A. This has consequences for every relationship and several processes.

Has anybody a suggestion ?

With kind regards
Ruud van Kersbergen

[epbernard]

this is not doable in Java (ie to change one class into another one), hence it's not possible in EJB3.

[ruud1]

i agree, but the problem is not creating the right subclasse in java (done by copying every attribute and/or using a special constructor).

Suppose baseclasse X and subclasse A and B.

I have a persistent object A, i create an object B with the SAME ID in A.

The problem is that i can not persist object B without deleting A first.

If i delete A and persist B in 1 transaction on what moment is the consistency checked by the application server (at the moment of delete of A or at the end of the transaction ?)

[epbernard]

I don't really understand your question, but your domain could probably be refactored (and benefit from it) wo using inheritance