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Hibernate version: 3.1.3

Mapping documents:
<class name="WheelManufacturer">
<id name="ID" type="long">
<generator class="native"/>
</id>
<property name="Name"></property>
</class>

<class name="WheelInstance">
<id name="ID" type="long">
<generator class="native"/>
</id>
<many-to-one name="WheelManufacturer" not-null="true" lazy="false" fetch="select"/>
<joined-subclass name="SixteenWheelManufacturer" table="SixteenWheelManufacturer">
<key column="ID"/>
<property name="StringValue"></property>
</joined-subclass>
</class>

<class name="CarMaker">
<id name="ID" type="long">
<generator class="native"/>
</id>
<property name="Name"></property>
<list lazy="false" fetch="select" name="WheelManufacturers">
<key column="cm_id"/>
<index column="idx"/>
<many-to-many column="wm_id" class="WheelManufacturer"/>
</list>
</class>

<class name="CompactCar">
<id name="ID" type="long">
<generator class="native"/>
</id>
<list lazy="false" fetch="select" name="CarMakers">
<key column="c_id"/>
<index column="idx"/>
<many-to-many column="cm_id" class="CarMaker"/>
</list>
<list lazy="false" fetch="select" name="WheelInstances">
<key column="c_id"/>
<index column="idx"/>
<many-to-many column="wm_id" class="WheelInstance"/>
</list>
</class>


Code between sessionFactory.openSession() and session.close():
Session session = sessionFactory.getCurrentSession();
Transaction transaction = null ;
try{
transaction = session.beginTransaction();
session.load(o, l);
transaction.commit();
}
catch( Exception e ) {
if(transaction != null)
transaction.rollback() ;
throw e ;
}
finally {
if(session.isOpen())
session.close();
}


Name and version of the database you are using: MySQL 5

The generated SQL (show_sql=true):

select, select, select, select, delete




My problem is the following. When I am loading an object, with 2 collections inside it, at the end, one of the collections related table gets a delete statement at the end. Now, to my understanding, there is no way, in a basic setup, a load should do a delete, right? More precisely, I am trying to load a compactCar, with 3 car makers in it, and no WheelInstances. The CarMakers table is the one who gets the delete statement at the end of the load, which leads to the CompactCar not having anything associated to it in the many-to-many table at the end of the load operation.

As additionnal information, if I remove the unused collection WheelInstance, for one thing, the problem still happens. If I change the fetch mode to join, the problem still happens. If I go through criteria query instead, it still happens.

What baffles me is that the object is correctly persisted in the bd, but after the load operation, its collection is just gone from the DB. This leads me to believe the error is not a mapping one.

I searched the forums, and all I could find was comeone having a more or less similar problem in Hibernate 2, but no one ever anwsered him.

Some additionnal info:

-Collection set to lazy loading: still gets a delete statement
-The delete statement does not happen when the load is executed, but then the transaction.commit is executed.

In case anybody else ever has this problem, here is the solution:

The error was there was a bug in one of my setters. So, when hibernate would set the value, it would do so incorrectly, hence set nothing at all. Then, just before closing the session, hibernate, seeing the state of the object would not be what it should be in the database, would proceed to update the database with the 'modified' version, and delete the collection that was not set properly.

Evict would prevent hibernate from saving the object after it had loaded, as would
<property name="hibernate.connection.autocommit">false</property>