Hi,
i have a problem by saving a one-to-one association
I have two tables/classes: One and Two
One has the columns id and two_id (foreign key)
Two has the columns id and value

I want to save a object from One and the Two-object should be saved automaticly. It works, but the two_id in the table One is missing, after entrying.

One:
id two_id
1 NULL

Two
id value
1 First entry

I send my mapping files and the java files.
Can you detect what is wrong?


Hibernate version:
2.1.6

Mapping documents:

<class
name="hibernate.One"
table="one"
>

<id
name="id"
type="java.lang.Integer"
column="id"
>
<generator class="identity" />
</id>


<!-- Associations -->

<!-- bi-directional one-to-one association to Two -->
<one-to-one
name="two"
class="hibernate.Two"
cascade="all"
constrained="true"
/>


</class>
<class
name="hibernate.Two"
table="two"
>

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

<generator class="identity"/>

</id>

<property
name="value"
type="java.lang.String"
column="value"
length="255"
/>

<!-- Associations -->


</class>


Code between sessionFactory.openSession() and session.close():

SessionFactory sessionFactory =
new Configuration().configure().buildSessionFactory();

Session ses = sessionFactory.openSession();
Transaction trans = ses.beginTransaction();

Two two = new Two();
two.setValue( "First entry" );


One one = new One();
one.setTwo( two );

ses.save( one );
// ses.save( two );


trans.commit();
ses.close();


Full stack trace of any exception that occurs:

Name and version of the database you are using:
mysql 4.1


I think the property two_id in the One-mapping is missing, but i don`t know how to use it.

Thanks a lot

The doc says:
".. there are two varieties of one-to-one associations:
1. primary key association
2. unique foreign key association ..."

So, if your association is the first one (and this is what your mapping looks like), you don't need a foreign key (extra table column) at all, as the two rows share the same primary key value.

If it's the second one, i.e. if your class Two has a property that references One, then your mapping should look like:

<class name="hibernate.One" table="one">

<id name="id" type="java.lang.Integer" column="id">
<generator class="identity" />
</id>

<!-- Associations -->
<many-to-one name="two" class="hibernate.Two" column="two_id" unique="true" cascade="all"/>

</class>
<class name="hibernate.Two" table="two">

<id name="id" type="java.lang.Integer" column="id">
<generator class="identity"/>
</id>

<one-to-one name="whatever your property's name is" class="hibernate.One" property-ref="two"/>

<property name="value" type="java.lang.String" column="value" length="255" />

<!-- Associations -->

</class>

This should work.
Alice