optimistic locking and decomposed M:N relationships

[Bonnie MacKellar <BM...@mobius.com>]

I am adding optimistic locking to my database, using integer version fields
in each table.
I notice that it does not seem to work with tables implementing M:N
relationships
(I am using the decomposed style). I get this error :
com.jnetdirect.jsql.w: Cannot insert the value NULL into column
'rowVersion', table 'ActiveBill.dbo.Custodian';

Custodian implements the M:N relationship between users and accounts.

Does this mean that I should omit the version fields in M:N relationship
tables?
How will locking be handled for such tables?

Here is the repository information for the tables in question :
<!-- Definitions for User table -->
   <class-descriptor
   	  class="com.mobius.activebill.persistentobjects.User"
   	  table="ActiveBillUser"
   >
      <field-descriptor
         name="userID"
         column="userID"
         jdbc-type="INTEGER"
         primarykey="true"
         autoincrement="true"
      />
      <field-descriptor 
         name="rowVersion" 
         column="rowVersion"
         jdbc-type="INTEGER" 
         locking="true"
      />
   ... stuff omitted...
      <collection-descriptor
      	  name="accounts"
 
element-class-ref="com.mobius.activebill.persistentobjects.Account"
      	  auto-retrieve="true"
      	  auto-update="false"
      	  indirection-table="Custodian"
        >
      	<fk-pointing-to-this-class column="userID" />
        <fk-pointing-to-element-class column="accountID" />
      	</collection-descriptor> 
   </class-descriptor>
!-- Definitions for Account table -->
   <class-descriptor
   	  class="com.mobius.activebill.persistentobjects.Account"
   	  table="Account"
   >
      <field-descriptor
         name="accountID"
         column="accountID"
         jdbc-type="INTEGER"
         primarykey="true"
         autoincrement="true"
      />
      <field-descriptor 
         name="rowVersion" 
         column="rowVersion"
         jdbc-type="INTEGER" 
         locking="true"
      />
      <field-descriptor
         name="accountNumber"
         column="accountNumber"
         jdbc-type="VARCHAR"
      />
      <field-descriptor
         name="customerID"
         column="customerID"
         jdbc-type="INTEGER"
      />
      <reference-descriptor
      	name="customer"
      	class-ref="com.mobius.activebill.persistentobjects.Customer"
      	proxy="true"
      	>
      	<foreignkey field-ref="customerID"/>
      </reference-descriptor>    
      <collection-descriptor
      	name="users"
      	element-class-ref="com.mobius.activebill.persistentobjects.User"
      	auto-retrieve="true"
      	auto-update="false"
      	indirection-table="Custodian"
      	>
      	<fk-pointing-to-this-class column="accountID" />
      	<fk-pointing-to-element-class column="userID" />
      </collection-descriptor>
      <collection-descriptor
         name="bills"
         element-class-ref="com.mobius.activebill.persistentobjects.Bill"
         proxy="true"
        >
        <inverse-foreignkey field-ref="accountID"/>
      	</collection-descriptor>
   </class-descriptor>
   <!-- Definitions for Custodian table -->
   <class-descriptor
   	  class="com.mobius.activebill.persistentobjects.Custodian"
   	  table="Custodian"
   >
      <field-descriptor
         name="accountID"
         column="accountID"
         jdbc-type="INTEGER"
         primarykey="true"
      />
      <field-descriptor 
         name="rowVersion" 
         column="rowVersion"
         jdbc-type="INTEGER" 
         locking="true"
      />
      <field-descriptor
         name="userID"
         column="userID"
         jdbc-type="INTEGER"
         primarykey="true"
      />
    <reference-descriptor
    	name="user"
    	class-ref="com.mobius.activebill.persistentobjects.User"
    	auto-retrieve="false"
    	>
    	<foreignkey field-ref="userID"/>
    </reference-descriptor>
    <reference-descriptor
    	name="account"
    	class-ref="com.mobius.activebill.persistentobjects.Account"
    	auto-retrieve="false"
    	>
    	<foreignkey field-ref="accountID"/>
    </reference-descriptor>
 </class-descriptor>

thanks,
Bonnie MacKellar
software engineer
Mobius Management Systems, Inc.
bmackell@mobius.com