Hi,

maybe it was asked before, but I can't find it.

My problem is, that I have 2 tables which are linked by a foreign key. Nothing special on it. Both tables have auto_increment enabled. The mapping files are generated by Middlegen (MiddlegenIDE and MyEclipse 3.0). But when I populate my model objects and try to save it, I get an error that the foreign key column is null. I thought that Hibernate will populate the value automatically ?

I'm using MySQL 4 and Hibernate 3.
Here are the mapping files:

-- table calendar --
<class
name="model.Calendar"
table="calendar"
>

<id
name="id"
type="java.lang.Integer"
column="id"
>

<generator class="native" />
</id>
<!-- Associations -->

<!-- bi-directional one-to-many association to Event -->
<set
name="events"
lazy="true"
inverse="true"
cascade="all"
>
<key>
<column name="calendar_id" />
</key>
<one-to-many
class="model.Event"
/>
</set>

-- table event (with the foreign to calendar)--
<class
name="model.Event"
table="event"
>

<id
name="id"
type="java.lang.Integer"
column="id"
>

<generator class="native" />
</id>
<!-- Associations -->

<!-- bi-directional many-to-one association to Calendar -->
<many-to-one
name="calendar"
class="model.Calendar"
not-null="true"
>
<column name="calendar_id" />
</many-to-one>

-- hibernate output --
DEBUG - could not insert: [model.Event] [insert into event ...
java.sql.SQLException: Column 'calendar_id' cannot be null

-- class CalendarService.java --

public void save (Calendar calendar) {
HibernateUtil.getSession().save(calendar) ;
}

Thanks for any help
Lothar

How did you add Event to Calendar? Something like this?

void add(Event evt) {
events.add(evt);
evt.setCalendar(this);
}

Check the docs on bi-directional mapping.

Thanks for your help.

But I can't get it working. I found an error in my database design so that I just have a simple onte-to-many relation. So now all seems to be ok, no errors, but the values aren't saved in the database.

What I'm doing wrong ? I've red the docu and some samples, but can't find the mistake.

Here the corrected mapping files:
-- class calendar --

<class
name="CalendarRO"
table="calendar"
>
<id
name="Id"
type="integer"
column="id"
unsaved-value="null"
>
<generator class="identity"/>
</id>

<set name="events" inverse="true">
<key column="id"/>
<one-to-many class="EventRO"/>
</set>
</class>

-- class Event--
<class
name="EventRO"
table="event"
>
<id
name="Id"
type="integer"
column="id"
unsaved-value="null"
>
<generator class="assigned"/>
</id>
<many-to-one
name="calendar"
column="calendar_id"
class="CalendarRO"
not-null="true"
>
</many-to-one>


My java code looks like:

CalendarRO calendarRO = new CalendarRO() ;
//calendarRO.setEvents(eventSet);
calendarRO.setEvents(new HashSet()) ;

for (getEvents().iterator) {

EventRO eventRO = new EventRO();
eventRO.setCalendar(calendarRO);
//eventSet.add(eventRO);
calendarRO.getEvents().add(eventRO) ;


}

HibernateUtil.getSession().saveOrUpdate(calendarRO)


It would be very nice if you can put me to the right direction.
Thanks, Lothar