Just want a column of a child table included in a class.

snorkled · **Joined:** Tue Sep 14, 2004 6:24 pm **Posts:** 1

Given a Device, I want to include the device_type_name property (from a foreign table) in the Device object: I do NOT want a reference to the entire DEVICE_TYPE row or an entire Device_type object (composition).

The relational DB tables are (pseudo code to keep it short)

Code:

DEVICE
    device_id     bigint
    device_name varchar
    device_type_fk bigint   references DEVICE_TYPE
    ...

and

DEVICE_TYPE
    device_type_id  bigint
    device_type_name varchar
    ...

For context, lets asssume that a device_type object is a hugely unwieldy thing that I'd rather not have in this particular application.

The Java Object I do want looks like:

Code:

class Device
    long device_id
    String deviceName
    String deviceTypeName

Note that this class has a device_type_name, NOT a device_type_fk or device_type object.

A typical SQL select to achive what I want would be:

Code:

select device_id, device_name, device_type_name from DEVICE d, DEVICE_TYPE dt 
where d.device_type_fk = dt.device_type_id

HOW DO I CREATE A MAPPING TO EXPRESS THE Device CLASS, GIVEN THE DEVICE AND DEVICE_TYPE TABLES?

Code:

<hibernate-mapping>
  <class name="Device" table="DEVICE">
     <id name="deviceID" column="device_id" type="long" />
        <property name="deviceName" column="device_name" type="string"/>
        <!-- THIS IS CERTAINLY WRONG: -->
        <property name="deviceTypeName" column="?????device_type.device_type_name" type="string"/>
  </class>
</hibernate-mapping>

anthony · **Posted:** Wed Sep 15, 2004 1:54 am

you can use a formula, but you can't update this property then...