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Date: Sat, 15 Mar 2003 10:02:24 +0100
From: Thomas Mahler <thma32@web.de>
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To: OJB Developers List <ojb-dev@db.apache.org>
Subject: Re: inheritance, extent and cleaner reference
References: <4895C7C2076BE54AB2C2E7BCFC57B4D2583CA8@boussole>
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Hi Houar TINE,

All three feature sound like real improvements.
Especially 1. and 2. have been requested several times by users. It 
would be great to integrate your stuff into the codebase!

Just post it to the list, we will review it!

thanks for your contribution,
Thomas


TINE Houari (OBJECTIVA) wrote:
> Hi,
> 
> I finished ameliorations of OJB that consist of 
> 
> 1. eliminating fk from 1-1 reference between objects.
> 2. implement inheritance as 1-1 reference.
> 3. eliminating the obligation of declaring the attribute ojbConcreteClass in
> extent class.
> 
> The idea consists of introducing the concept of anonymous field descriptor
> and anonymous persitent field.
> 
> case1: A reference B through a 1-1 relation
> class A {
>   int id;
>   B refB;
> }
> 
> class B {
>   int id;
>   String attribute;
> }
> 
> Class descriptor for A will be declared like this:
> 
> <class-descriptor class="A" table="TABLE_A">
> 	<field-descriptor id="1" name="id" column="ID" jdbc-type="INTEGER"
> primarykey="true" autoincrement="true" />
> 	<field-descriptor id="2" name="" column="ID_B" jdbc-type="INTEGER"
> />
> 	<reference-descriptor name="refB" class-ref="B" auto-update="true">
> 		<foreignkey field-id-ref="2" />
> 	</reference-descriptor>
> </class-descriptor>
> 
> NOTICE that the name of field 2 is "".
> -----------------------------------
> 
> Amelioration allow to handle referenced object B without having a fk in A.
> 
> Case 2: X inherits from Y
> class Y {
>   int id;
>   String AttributeY;
> }
> 
> class X extends Y {
>   String AttributeX;
> }
> 
> Class descriptor for X will be declared like this:
> 
> <class-descriptor class="X" table="TABLE_X">
> 	<field-descriptor id="1" name="id" column="ID" jdbc-type="INTEGER"
> primarykey="true" autoincrement="true" />
> 	<field-descriptor id="2" name="" column="ID_Y" jdbc-type="INTEGER"
> />
> 	<reference-descriptor name="" class-ref="B" auto-update="true">
> 		<foreignkey field-id-ref="2" />
> 	</reference-descriptor>
> </class-descriptor>
> 
> NOTICE that the name of field 2 is "" and the name of reference-descriptor
> is ""
> ----------------------------------------------------------------------------
> ----
> 
> Amelioration allow to handle base object Y as a reference-descriptor.
> 
> 
> Case3: extent
> 
> abstract class U {
>   int id;
> }
> 
> class V extends U {
>   ...
> }
> 
> class W extends U {
>   ...
> }
> 
> The class descriptor is not changed but the amelioration don't need an
> attribute ojbConcreteClass to handle objects.
> 
> 
> How it works:
> I have introduced 
>   - AnonymousFieldDescriptor,
>   - AnonymousPersistendField,
>   - AnonymousPersistendFieldForInheritance,
>   - AnonymousObjectReferenceDescriptor,
>   - AnonymousFKValue and
>   - AnonymousObjConcreteClassValue
> 
> and some modifications in the class RepositoryXmlHandler. That's all.
> 
> What do you think.
> 
> Houar TINE
> 
> 
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