Hibernate version: 2.1.6

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

<hibernate-mapping package="nl.test">
<class name="nl.test.Werknemer" table="werknemer">
<id
column="naam"
name="Naam"
type="string"
>
<generator class="assigned" />
</id>
<property
column="werknemerId"
length="10"
name="WerknemerId"
not-null="false"
type="string"
/>
<property
column="postcode"
length="7"
name="Postcode"
not-null="false"
type="string"
/>
<property
column="woonplaats"
length="50"
name="Woonplaats"
not-null="false"
type="string"
/>
</class>
</hibernate-mapping>

Code between sessionFactory.openSession() and session.close():
Session sess = sf.openSession();
try {
tx = sess.beginTransaction();
sess.save(werknemer);
tx.commit();
} catch (HibernateException e) {
if (tx!=null) tx.rollback();
throw e;
}
finally {
sess.flush();
sess.close();
}
Full stack trace of any exception that occurs:
no exceptions

Name and version of the database you are using:
mysql 4.0.18

I'am using JSF to make a werknemer in J2EE and hibernate to store it in mysql.
everything is working fine. I have just one little problem every time that i insert a [werknemer] he overwrite the other values in the table werknemer.

any suggestions or help would be appreciated.

Bart.