Hi,

I am trying to get a simple one-many mapping working in the following use-case.

---- Find Team/Players
- Open Session
- Find Team (loading the players collection (bag) )
- Close Session.


---- Update Team/Players in a later session
- Open Session
- Remove all children (players). I dont maintain the ids for the existing children and want to do bulk delete and re-insert as I only have <10 children at most.
- Add new Players (bag). using team.setPlayers(List players)
- team.update.
- close session.

Problem is that I can't get the delete-children to work. I am not sure if its possible without having ids. I also tried session.delete but that gave an exception too (stack trace below).

with session.delete() commented out, I just get the children always added and it keeps adding without deleting the existing children (players).

HIBERNATE VERSION: 2.0.2
MAPPING SNIPPET:
<bag name="Players" inverse="true" cascade="all-delete-orphan" lazy="false">
<key column="team"/>
<one-to-many class="Players"/>
</bag>

JAVA CODE:
Transaction tx = null;
Session session = Persistance.getInstance();
try {
//team.getPlayers().clear(); // DIDN'T DELETE ANY
session.delete("from players in class players where players.team = xx");
team.setPlayers(players); // set players and their team to "this"
session.update(team);
tx.commit();
} catch (HibernateException e) {
if (null != tx)
tx.rollback();
log.error("Error in update",e);
throw e;
} finally {
session.close();
}

STACK TRACE:
Error Flush during cascade is dangerous - this might occur if an object was deleted and then re-saved by cascade
net.sf.hibernate.HibernateException: Flush during cascade is dangerous - this might occur if an object was deleted and then re-saved by cascade
at net.sf.hibernate.impl.SessionImpl.flush(SessionImpl.java:2001)
at net.sf.hibernate.impl.SessionImpl.save(SessionImpl.java:589)
at net.sf.hibernate.impl.SessionImpl.saveOrUpdate(SessionImpl.java:1187)
at net.sf.hibernate.engine.Cascades$3.cascade(Cascades.java:88)
at net.sf.hibernate.engine.Cascades.cascade(Cascades.java:258)
at net.sf.hibernate.engine.Cascades.cascade(Cascades.java:298)
at net.sf.hibernate.engine.Cascades.cascade(Cascades.java:341)
at net.sf.hibernate.impl.SessionImpl.preFlushEntities(SessionImpl.java:2285)
at net.sf.hibernate.impl.SessionImpl.flushEverything(SessionImpl.java:2015)
at net.sf.hibernate.impl.SessionImpl.autoFlushIfRequired(SessionImpl.java:1560)
at net.sf.hibernate.impl.SessionImpl.getQueries(SessionImpl.java:1372)
at net.sf.hibernate.impl.SessionImpl.find(SessionImpl.java:1332)
at net.sf.hibernate.impl.SessionImpl.find(SessionImpl.java:1322)
at net.sf.hibernate.impl.SessionImpl.delete(SessionImpl.java:1457)
at updateTeam(TeamMgmt.java:72)

DATABASE: MySql 4.0.14


I will appreciate your help.

Thanks,
Tahir

I have already read these tips and tried all.

I am not updating the identifier of the object but only one of two other attributes and still getting the exception.

I still tried to use session.evict() just before the update but without any luck.

any other ideas??

Where players colelction come from ?

The player collection comes from the Swing GUI and passed in as the method parameter.
The team.setPlayers(players) loops through the collection (List) and assign the team as player.setTeam(thisTeam).

Only thing different here is that I dont keep the ids for players from the previously loaded data and hence just want to delete the existing players and add new players during the update.

Can you tell me how the one-shot-delete work with all-delete-orphan setting so I can try that.

try to flush() after the delete.

I actually had it earlier and removed it because docs say that you should only flush once.

Anyway, I put it back. The exception is gone but now its not adding any children to the DB (I can't see any SQL for insert children from p6spy).


Can you tell me if this is NOT a standard practice to discard existing children and add new ones without worrying about comparing ids to find new/update etc?

All I want to do is delete-existing-children and save team with dependent object graph containing new children.

Please help.

Tahir

You should not explicitly flush(), because it may be less performant (no SQL factoring of Hibernate), but you can do if you need to.

No this is not standard. Hibernate is lost, you asked it to remove them and after that to link them.

I am lost too. I am not removing and then adding the same objects to the collection. But I want to do collection.clear() (or remove one by one) and then add the current children objects (or do a setChildren() if possible).
As the unsaved-value is zero and these are NEW object instances so hibernate should be able to insert these objects.

Show the player mapping.
I suspect you set a many-to-one to team.
If true then read that http://www.hibernate.org/155.html