Hi,

Am using hibernate 2 and am a new user.

I have two persistent classes Event.java and User.java. I have a - Set favouriteEvents defined in my User class. This keeps track of the users favourite events.

I have one event and 2 users in the database currently. I have one record in the favouriteEvents table that relates user 2 to event 1.

The Event.hbm.xml and User.hbm.xml files are listed below.

(I have added a favourite event to the second users).

I can persist everything fine. Problem is when i want to delete a favouriteEvent from one of the user. This is the java code i run to delete the favourite event:


events = instance.listEvents();
Event event = (Event) events.get(0);
User user = instance.getUser(new Long(2));
user.removeFavouriteEvents(event);
instance.updateUser(user);

I check my data in the database and the favouriteEvent record does not get deleted.????? There are no exceptions throwns. Does anybody have an idea what I am doing wrong?????

Thanks.

The listEvents and updateUser functions are listed here:

private List listEvents()
{
try
{
Session session = sessionFactory.openSession();
Transaction tx = session.beginTransaction();

List result = session.find("from Event");

tx.commit();
session.close();

return result;
}
catch (HibernateException e)
{
throw new RuntimeException(e.getMessage());
}
}

private void updateUser(User user)
{
try
{
Session session = sessionFactory.openSession();
Transaction tx = session.beginTransaction();

session.update(user);
session.flush();

tx.commit();
session.close();
}
catch (HibernateException e)
{
e.printStackTrace();
}
}


Listings:

Event.hbm.xml:

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 2.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd">

<hibernate-mapping>

<class name="med.allegro.events.Event" table="EVENT">
<id name="id" column="uid" type="long">
<generator class="increment"/>
</id>
<property name="date" type="timestamp"/>
<property name="title" column="eventtitle"/>

<set name="participatingUsers" table="participations">
<key column="event_uid"/>
<many-to-many column="user_uid" class="med.allegro.events.User"/>
</set>

</class>
</hibernate-mapping>


User.hbm.xml:

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 2.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd">

<hibernate-mapping>

<class name="med.allegro.events.User" table="USER">
<id name="id" column="uid" type="long">
<generator class="increment"/>
</id>
<property name="age"/>
<property name="firstName"/>
<property name="lastName"/>

<set name="favouriteEvents" table="favourite_events">
<key column="user_uid"/>
<many-to-many
column="event_uid"
class="med.allegro.events.Event"/>
</set>

<set name="emails" table="user_emails">
<key column="user_uid"/>
<element column="email" type="string"/>
</set>

<set name="eventsJoined" table="participations" inverse="true">
<key column="user_uid"/>
<many-to-many column="event_uid" class="med.allegro.events.Event"/>
</set>

</class>

</hibernate-mapping>

Just after I sent my previous post I found a way to accomplish what I was doing, by using the function listed below.

I have another question though, am trying to understand this. Users can have many favourite events and events could be a part of many users as their favourite events , therefore I define this:



Now, how do I tell hibernate to delete all associations from the favourite_events table when I delete a favourite event from the favouriteEvents Set in the User ?

i.e. If I were to do this:

User user1 = (User) users.get(0);

instance.deleteUser(user1);



QUESTION 1: I want the user1 and the associated records from the favourite_events table deleted. When I delete the user1. Is there a way to get this accomplished?

QUESTION 2: Have I written the removeFavouriteEvents function optimally or is there an easier way to do this?


Thanks.

Listing: