Problem with Mapping Inheritance Hierarchies

[Bj�rn Voigt]

Hello OJB'lers,

I have a problem to map Inheritance Hierarchies, I'am the using the third
proposal of the tutoriala and mapping each class to a distinct table.
I have the following Classes:

1. A and B implements ABInterface
2. B extends A
public class A implements ABInterface{
  int id;
  int someValueFromA;
  public String toString() {
     return this.getClass() + " id:" +id +" a_value:" + someValueFromA;
  }
}
public class B extends A {
  int id;
  int someValueFromB;
  public String toString() {
     return super.toString() + " b_value:" + someValueFromB;
  }
}
My Mapping looks so:

<class-descriptor class="test.ABInterface">
  <extent-class class-ref="test.A"/>    
  <extent-class class-ref="test.B"/>    
</class-descriptor>
<class-descriptor class="test.A" table="a">
  <field-descriptor name="id" column="id" jdbc-type="INTEGER" 
primarykey="true" autoincrement="true" />
  <field-descriptor name="someValueFromA" column="some_value_from_a" 
jdbc-type="INTEGER" />
  <extent-class class-ref="test.B"/>	
</class-descriptor>

<class-descriptor class="test.B" table="b">
  <field-descriptor name="id" column="a_id" jdbc-type="INTEGER" 
primarykey="true" autoincrement="true" />
  <field-descriptor name="someValueFromB" column="some_value_from_b" 
jdbc-type="INTEGER" />
  <reference-descriptor name="super" class-ref="test.A">
	<foreignkey field-ref="id" />
  </reference-descriptor>
</class-descriptor>

And the table looks:

CREATE TABLE A ( ID   INT PRIMARY KEY, SOME_VALUE_FROM_A  INT)
CREATE TABLE B ( A_ID INT NOT NULL,    SOME_VALUE_FROM_B  INT)
Table A contains to rows:

 id | some_value_from_a
----+-------------------
  1 |              1000
  2 |              1000
Table B cointains a refenrence to the second row in B

 a_id | some_value_from_b
------+-------------------
  2   |              2000
Ok, what I want is to query the ABInterface and get two objects,
one instance of A and one of B (because id=2 and a_id=2) but what I get 
is one
instance of A (OK thats right), but two instaces of B. And the b instances
cointains no value for the some_value_from_a field. A query have 
following result:

	[...]

        Query q = QueryFactory.newQuery(ABInterface.class, c);
        Iterator iter = broker.getCollectionByQuery(q).iterator();
        while (iter.hasNext()) {
                ABInterface element = (ABInterface) iter.next();
                System.out.println(element.toString());
        }
	[...]

class test.B id:0 a_value:0 b_value:2000
class test.A id:1 a_value:1000
class test.B id:0 a_value:0 b_value:2000
What I want is:
class test.A id:1 a_value:1000
class test.B id:2 a_value:1000 b_value:2000
Could anyone tell what I do wrong or is it possible what want to do? ;-)

Thank you for help

Bj�rn Voigt



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