Re: Mapping question

[Armin Waibel]

Hi,
not sure that I understand the problem.
Each User has two Address attributes ('home' and 'work'), both are of 
the same type 'Address' (both 1:1 references), you don't use extension 
classes AddressHome and AddressWork objects. Address use a composite PK 
('login' and 'type').

In this case each reference has to use a composite FK key too.
in User (assume the 'login' datatype is INTEGER and User use an 
autoincrement PK, only show mapping for the 'home' reference, 'work' 
will be the same):

You need a FK field for each PK value of the referenced object, if you 
use 'anonymous' fields, you don't need a "real" fields in your 
persistent object class (User) - more info see docs.
http://db.apache.org/ojb/docu/guides/advanced-technique.html#How+do+

<field-descriptor
             name="fkLoginHome"
             column="FK_LOGIN_HOME"
             jdbc-type="INTEGER"
            access="anonymous"
        />
<field-descriptor
             name="fkTypeHome"
             column="FK_TYPE_HOME"
             jdbc-type="VARCHAR"
            access="anonymous"
        />
<reference-descriptor
   name="homeAddress"
   class-ref="Address"
   auto-retrieve="true"
   auto-update="true"
   auto-delete="true">
   <foreignkey field-ref="fkLoginHome" />
   <foreignkey field-ref="fkTypeHome" />
</reference-descriptor>
In Address you use the composite PK and both attributes has to be set by 
hand (no PK auto-generation was used) and the 'login' field is a FK from 
User table. This will make things complicated, because on insert OJB 
will first store the 1:1 references, but in your case we need the 
'login' PK first. So we need a workaround when insert User objects:

broker.beginTransaction();
User user = new User();
broker.store(user);
// now the PK ('login' field in User) is specified
Address home = new Address();
home.setLogin(user.getLogin());
home.setType("home");
user.setHome(home);
//
broker.store(user);
broker.commitTransaction();
Things will be easier when you use an single autoincremented PK field in 
Address. In this case all will be handled by OJB and you only need 
single FK field-descriptor in User:

broker.beginTransaction();
User user = new User();
Address home = new Address();
home.setType("home");
user.setHome(home);
broker.store(user);
broker.commitTransaction();
regards,
Armin
G�nther Wieser wrote:
hi,
as far as i understand this, you try to differentiate by the value of
"adress.type" whether an adress is a home wor work adress?
well, i have no solution for that, but i tried it here with a similair data
structur, and it didn't work either.
to be honest i'm not sure if this is the intended use for <attribute> in
<collection-descriptor> or <reference-descriptor>, because i didn't find
anything in the docs. all i found was an example in the ojb test cases in
repository_junit.xml, but the corresponding source code didn't tell me
anything i could understand.
so, long speach, short meaning: i'm also interested in a solution for that!
kr,
guenther
-----Original Message-----
From: Georg M�ller [mailto:[EMAIL PROTECTED] 
Sent: Wednesday, March 02, 2005 9:24 PM
To: ojb-user@db.apache.org
Subject: Mapping question

Hi,
I have an object "User" who has 2 addresses, home and work.
User is mapped to a table user (no problem here).
Both home and work address are mapped to a table address.
This table has a composite primary key: login and type
  - login from table user as a foreign key
  - type is a string (or enum) "home" and "work"
I have tried the following without success:
in User description:
<reference-descriptor
   name="homeAddress"
   class-ref="Address"
   auto-update="true"
   auto-delete="true">
   <attribute attribute-name="type" attribute-value="heimat"/>
   <foreignkey field-ref="login" />
</reference-descriptor>
and in Address description:
<field-descriptor
   name="login"
   column="login"
   primarykey="true" />
<field-descriptor
   name="type"
   column="type"
   primarykey="true" />
Is it possible to make it run anyhow?
Regards,
Georg
P.S.: Please CC me
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