Hello,
i work with these two tables : 
model (*modelId, acquisitionCost);
mobile (*mobilId , *modelId);
Here are my mapping files : 
Code:
<hibernate-mapping package="market.test.hibernate">
    <class name="Model" table="model" catalog="market">
        <id name="modelId" type="java.lang.Integer">
            <column name="modelId" />
            <generator class="identity" />
        </id>
        <property name="acquisitionCost" type="java.lang.Float">
            <column name="acquisitionCost" precision="12" scale="0" />
        </property>      
        <set name="mobiles" inverse="true" lazy="true" table="mobile" fetch="select">
            <key>
                <column name="modelId" not-null="true" />
            </key>
            <one-to-many class="Mobile" />
        </set>
    </class>
</hibernate-mapping>
and
Code:
<hibernate-mapping package="market.test.hibernate">
    <class name="Mobile" table="mobile" catalog="market">
        <id name="mobileId" type="int">
            <column name="mobileId" />
            <generator class="increment" />
        </id>
        <many-to-one name="model" class="Model" fetch="select">
            <column name="modelId" not-null="false" />
        </many-to-one>
        <property name="configId" type="string">
            <column name="configId" length="45" />
        </property>
        <set name="loadcapacities" inverse="true" lazy="true" table="loadcapacity" fetch="select">
            <key>
                <column name="mobileId" not-null="true" />
            </key>
            <one-to-many class="Loadcapacity" />
        </set>
    </class>
</hibernate-mapping>
I have an entry in my table model(modelId=1, acquisitionCost=3000),
and two in the table mobile (mobilId=1,modelId=null et mobilId=2, modelId=null).
I want to update mobile table by setting the field modelId of the two entries with the value 1.
This is my code : 
Code:
 private void addMobileToModel(int mobileId, int modelId) {
           Session session = HibernateUtil.getSessionFactory().getCurrentSession();
           session.beginTransaction();
           Mobile mobile = (Mobile) session.load(Mobile.class, mobileId);
           Model model = (Model) session.load(Model.class, modelId);            
           model.getMobiles().add(mobile);
           session.getTransaction().commit();
}
When I call this code, there is no error but my Data base is not updated.
Does anyone has an idea ?
Thanks.