one-to-one assoc.: class with 3 and 2 keys for composite?

noips · **Posted:** Tue Dec 09, 2003 9:05 am

Hi there:

Following situation:

Table ProductOrder has a PK that looks like this:
OrderID
CategoryID
ProductID

Table Product has a PK like this:
CategoryID
ProductID

I want to define a one-to-one association between them via the PKs "CategoryID" and "ProductID".
When I try to do so, I get the following error:

MappingException: invalid join columns for association: Product

The reason for this error is basicly clear: I have to tell hibernate which columns to join
with. But how can I do this?

Here my mapping files for the tables:

Code:

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

<hibernate-mapping>
  <class name="com.iag.ProductOrder"
         table="product_order" lazy="true">

    <composite-id>
        <key-property name="OrderId" column="order_id" type="integer"/>
        <key-property name="CategoryId" column="category_id" type="integer"/>
        <key-property name="ProductId" column="product_id" type="integer"/>
    </composite-id>

    <version name="modified"
             unsaved-value="undefined"/>

    <property name="Text" column="text" type="string" not-null="false"/>

    <many-to-one name="CustomerOrder" column="order_id" not-null="false"
                 insert="false" update="false"/>

    <one-to-one name="Product" class="com.iag.Product"/>
  </class>
</hibernate-mapping>

And for the Product:

Code:

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

<hibernate-mapping>
  <class name="com.iag.Product"
         table="product">

    <composite-id>
        <key-property name="CategoryId" column="category_id" type="integer"/>
        <key-property name="ProductId" column="product_id" type="integer"/>
    </composite-id>

    <version name="modified"
             unsaved-value="undefined"/>

    <property name="CategoryId" column="category_id" type="integer" not-null="true"
              insert="false" update="false"/>
    <property name="ProductId" column="product_id" type="integer" not-null="true"
              insert="false" update="false"/>
    <property name="Name" column="name" type="string" not-null="true"/>
    <property name="Price" column="price" type="double" not-null="false"/>
    <property name="Type" column="type" type="string" not-null="true"/>
  </class>
</hibernate-mapping>

Thx for any help.

Regards,
noips

emmanuel · **Posted:** Tue Dec 09, 2003 11:50 am

one-to-one linked classes must refer the same id value. It cannot be your case since ids are structurally incompatible.

Have a look at the property-ref attribute of one-to-one in hibernate 2.1. Might help.

noips · **Posted:** Wed Dec 10, 2003 3:18 am

epbernard wrote:

one-to-one linked classes must refer the same id value. It cannot be your case since ids are structurally incompatible.

They do refer to the same id value. The only difference is that is is an composite key in this case.
Nothing remarkable, don

gavin · **Posted:** Wed Dec 10, 2003 3:29 am

Quote:

They do refer to the same id value.

No they don't! One has three columns in the id, one has two. The ids can't possibly be the same.

noips · **Posted:** Wed Dec 10, 2003 3:44 am

gavin wrote:

Quote:

They do refer to the same id value.

No they don't! One has three columns in the id, one has two. The ids can't possibly be the same.

Yes, you are right. Viewed from the Product

gavin · **Posted:** Wed Dec 10, 2003 3:54 am

There are two approaches:

EITHER:

Code:

<many-to-one name="product" 
        class="Product"
        insert="false"
        update="false"
        constrained="true">
        <column name="category_id"/>
        <column name="product_id"/>
</many-to-one>

OR:

Code:

<composite-id>
        <key-property name="OrderId" column="order_id" type="integer"/>
        <key-many-to-one name="product" class="Product">
                <column name="category_id"/>
                <column name="product_id"/>
        </key-many-to-one>
</composite-id>

noips · **Posted:** Wed Dec 10, 2003 4:23 am

gavin wrote:

There are two approaches:

EITHER:

Code:

<many-to-one name="product" 
        class="Product"
        insert="false"
        update="false"
        constrained="true">
        <column name="category_id"/>
        <column name="product_id"/>
</many-to-one>

Only if I remove the

Code:

constrained="true"

entry, this approach works.
Do you know why?

gavin wrote:

OR:

Code:

<composite-id>
        <key-property name="OrderId" column="order_id" type="integer"/>
        <key-many-to-one name="product" class="Product">
                <column name="category_id"/>
                <column name="product_id"/>
        </key-many-to-one>
</composite-id>

So both approaches do work, thx a lot!!

Regards,
noips