Composite key mapping

rorostar · **Joined:** Thu Feb 05, 2009 4:17 pm **Posts:** 8

Hibernate 3

Hi, I'm trying to do the mapping for the following relationship:

CartTable
- ID (PK)
- HeatKitModel
- ProductID
HeatKitModel is foreign key to HeatKitTable.ItemNumber

ProductTable
- ID (PK)
- HeatKitTableName
HeatKitTableName is foreign key to HeatKitTable

HeatKitTable
- TableName
- ItemNumber
(TableName & ItemNumber are composite key for HKTable)

In my Cart class, I want to have a reference to the HK Object.
I was trying to do many-to-one mapping to the HeatKit Table, but I was unable to, since in CartTable, I only have one part of the composite key (HeatKitModel). The other part is in ProductTable (but I have ProductID and I could resolve it).
Could you please give me a suggestion on how I should map these?

rosswilliamdrew · **Posted:** Fri Feb 20, 2009 7:07 am

Are you just talking about mapping a composite key in your mapping file? like this?...

Code:

<class name="HeatKitTable" table="HEATKIT">  
  <composite-id>
    <key-property name="tableName"/>
    <key-property name="itemNumber"/>
  </composite-id>
</class>

rorostar · **Joined:** Thu Feb 05, 2009 4:17 pm **Posts:** 8

Thank you for your reply.
Yes, I have done that.
But now I'm trying to make cart to have a HeatKit.
The relationship is many to one.

Code:

<many-to-one name="heatKit" 
   class="com.mycompany.HeatKit" 
   insert="false" update="false" not-null="true"
   fetch="join" lazy="false">  
   <column name="HEATKITMODEL"/>
</many-to-one>

This mapping will complain that it's missing another key since HeatKit has composite key.

I was trying to put use the other foreign key, which is TableName, but cart doesnt have it. It needs to get it from ProductTable. Is it possible to do this in the mapping?

rosswilliamdrew · **Posted:** Fri Feb 20, 2009 12:03 pm

Why not just have a one-to-many FROM the HeatKit to the Kart..

Code:

<one-to-many name="kart" class="kart" />

Then the foreign key from the Kart is stored in all instances of HeatKit that reference it? Rather than having an intermediate table?

rorostar · **Joined:** Thu Feb 05, 2009 4:17 pm **Posts:** 8

Well, logically, I would want to get which HeatKit is for this Cart, not which Cart contains this HeatKit.
My use case would always start from Cart.