Hibernate version: 2.1.6

Hello,

How do I change the value of discriminator field in Hibernate?
I have a hierarchy of classes:
UserVO <---- NewUser <---- IncompleteUser <------ ActiveUser

Where <---- means "extends", UserVO is an abstract class at the top of hierarchy. All these classes are mapped to the same 'user' table with discriminator field 'USER_TYPE'. Now if I have a record with 'NewUser' value in discriminator field and want to change it to 'IncompleteUser' (user status changes), how do I do that with Hibernate?

Thanks,
-Oleg.

I'm using table-per-hierarchy strategy

i'm not sure to understand but you can't change an object type, so you can't change the discriminator value.
It is more (java) oo to create a new object of type 2 and delete the object of type 1.

let me clarify my situation:

user can have different statuses:
1) "new" when he just registered
2) "incomplete" when he performs a certain action on the site
3) "active" when he does something else ,etc ...

With each successive status he has more data (more fields) associated with him.

We implement this by having a hierarchy of "user" objects, with abstract "UserVO" at the top, extended by NewUserVO, which in turn is extended by IncompleteUserVO, extended by ActiveUserVO, etc....

We do not need to change the type of an object at runtime, but we do need to change the value of the DISCRIMINATOR field from "new" to "incomplete" and later to "active" etc, so that when an object for this row is loaded NEXT time - it will be of a different type.

Here is the sequence of event:
1) Load NewUserVO from table 'user'.
2) Somehow (HOW?) update discriminator field from "new" to "incomplete"
3) some time later: load object corresponding to the same row in user table as in step 1). But this time the loaded object must be of type IncompleteUserVO (corresponding to discriminator value "incomplete".

It is possible to map a status property to the same column as the discriminator, using insert="false". You can do it that way.

If it were me, I would probably reconsider your object model. Use delegation instead of inheritance.

I've tried doing the update using the method you suggested with mapping another property to discriminator and settting insert=false, however I'm now getting an exception:

Exception building SessionFactory: Repeated column in mapping for class ActiveUserVO should be mapped with insert="false" update="false": userType

It looks like I have to set update=false too, but then the value of the property does not get updated in the database.

Could you suggest another solution?

Thanks,
-Oleg.

I agree with anthony. In your position, I would change your design to contain a UserVO object and have an enumerated field called status. You can check the "hibernate in action" book (sample chapter available for reading online) which shows you how to do the enumerated type. Subclassing in your case is not really good design.[/i]

I understand that the design is probably is not done properly for Hibernate model, but our project is in the phase were we cannot make such change (switch from inheritance to delegation). I'm just looking for anywork around for this problem (updating value of the userType field).

Someone has suggested using straight JDBC to update the field, but that would compromise cached objects in Hibernate cache. Could you suggest how to get around it? Do I need to invalidate the whole cache, or is there a way to invalidate only all objects mapped to the User table, or even to a particular record?

Thanks.

submit to JIRA, Hibernate should let you have the discriminator mapped to the same col as a property with insert=false

Do you really think this is practical? Making the discriminator-field updateable would mean a type-change of the object, which is not doable in Java. This will produce all kinds of nasty conflicts ...



The object should now be of type B, however there is still an old A instance with the same identifier around.

IMHO the only clean way to do this is to use JDBC and to manually flush the caches.

That is precisely what I'm trying to do now, straight JDBC - then flush the caches, but it looks like Session.evict(Object) and Session.getSessionFactory().evict(...) methods are not completely flushing caches, because I'm still getting the NonUniqueObjectException, with the message that there are two objects mapping to the same id.

I'm getting this error only when I'm trying to update the second object, of the updated type (IncompleteUserVO).

Here is the sequence:
1) Load NewUserVO from user table.
2) get its id and call JDBC to update the discriminator field 'userType' to 'incomplete'. Evict old object (NewUserVO) from Hibernate cache.
3) Load user object with the same id - now Hibernate loads an instance of IncompleteUserVO (which is good), with all data.. everything ok
4) When I'm changing value of one of the fields on IncompleteUserVO and trying to update it using Session.update(..) - I'm getting NonUniqueObjectException

Here is the code that does the JDBC update and cleans Hibernate cache. Is there anything wrong with it?

--------------------
NewUserVO user = ...
int id = user.getId();
Class clazz = user.getClass();
Connection conn = session.connection();
Statement stat = conn.createStatement();
session.flush();
session.getSessionFactory().evict(clazz, new Integer(id));
session.evict(user);
int result = stat.executeUpdate("update user set userType = 'incomplete' where id = " + id);
if (!conn.getAutoCommit())
conn.commit();
session.getSessionFactory().evict(clazz, new Integer(id));
session.evict(user);

IncompleteUserVO inuser = new IncompleteUserVO();
session.load(inuser, new Integer(id));
--------------------

As I said - the session.load method loads 'inuser' with valid data, but whenever I'm trying to do session.update(inuser) - I'm getting that exception.

Continuing to use a session which has an already committed connection is not a good idea anyways. Use a new session.

could you post a code sample of what I need to do? just session.close() ?

also, what if other thread's sessions are keeping a reference to that record through objects of type NewUserVO?