Hibernate - Force foreign key lookup on insert

[Ally Cavs]

Hello

These are the mappings of my SQL DB:

USERACCOUNT
-------------
Userid (PK) --autoincrement



USERACCOUNTInvoice
-------------
Userid (PK) –-Foreign Key to the above
Invoics(PK) --autoincrement


In my app I create a new UserAccountInvocie object which I persist by doing a session,save(useraccount) I get an error saying

Cannot intert null into UserAccountInvoiceTable for field UserID

NOTE: there are a number of USERACCOUNTInvoice objects in a SET in the USERACCOUNT object. So ideally saving parent will cascade down to child changes

Is there a way of mapping the relationship in the XML so Hibernate knows to use the userID of the parent UserAccount object. I don’t think I should set the userID in USERACCOUNTInvoice manually as I think Hibernate will get very confused if I partially set the composite key. And I don’t want to loop through a the child set and save new USERACCOUNTInvoice either. Unless I have too?

  
<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-mapping
   PUBLIC "-//Hibernate/Hibernate Mapping DTD//EN"
   "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>

<class name="ie.admin.details.UserAccount" table="user_account" lazy="false">
        <id name="userID" column="userId" type="string" >
            <generator class="identity"/>
        </id>
        
        <property name="userName" column="USERNAME" type="string"/>
        ...
        ...
        
        <set name="userAccountInvoices" inverse="true" lazy="false"  >
            <key column="USERID"   not-null="true" update="true"/><!--foreign-key="user_account_invocies_ibfk1"-->
            <one-to-many class="ie.admin.details.UserAccountInvoices"/>
        </set>
    </class>
</hibernate-mapping>

<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-mapping
   PUBLIC "-//Hibernate/Hibernate Mapping DTD//EN"
   "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>


    <class name="ie.admin.details.UserAccountInvoices" table="user_account_invoices" lazy="false">
        <composite-id>
            <key-property name="userID" column="USERID">

            </key-property>    
            <key-property name="invoiceID" column="invoice_ID" >
            </key-property>
        </composite-id>

      <many-to-one  column="USERID" insert="false" update="false" name="userAccount" class="ie.admin.details.UserAccount"/> 
      <many-to-one  not-null="true" insert="false" update="false"  name="invoice" class="ie.admin.details.Invoice" column="invocieID" lazy="false"/>

    </class>
</hibernate-mapping>