Re: ojb and interface driven design

[Maksimenko Alexander]

thanks for idea but its unfortunately doesn't fit to me :(
because i'm need using proxies for perfomance reasons
of cause user a 1-m to group - but i created this example to simplify 
understanding by problem - in real project my classes are big enough and 
ojb descriptor is huge ;)

Gelhar, Wallace Joseph wrote:
I've ran into this before.  I think the solution I found was to map the
reference / collection descriptor classes to the implementing descriptor
as follows:
<class-descriptor 
	class="test.ojb.datamodel.User">
	<extent-class class-ref="test.ojb.datamodel.impl.UserImpl"/>
</class-descriptor><class-descriptor
class="test.ojb.datamodel.impl.UserImpl" 
	table="USER" 
	factory-class="test.ojb.datamodel.impl.FactoryImpl"
	factory-method="createUser">
	<field-descriptor 
...
	<reference-descriptor
		name="group"
		class-ref="test.ojb.datamodel.GroupImpl"
		proxy="true"
	>
		<foreignkey field-ref="groupId"/>
	</reference-descriptor>	
</class-descriptor>

<class-descriptor 
	class="test.ojb.datamodel.Group">
	<extent-class class-ref="test.ojb.datamodel.impl.GroupImpl"/>
</class-descriptor>
<class-descriptor 
	class="test.ojb.datamodel.impl.GroupImpl" 
	table="GROUP1" 
	factory-class="test.ojb.datamodel.impl.FactoryImpl"
	factory-method="createGroup">
	<field-descriptor 
...
	<reference-descriptor
		name="manager"
		class-ref="test.ojb.datamodel.UserImpl"
		proxy="true"
	>
		<foreignkey field-ref="managerId"/>
	</reference-descriptor>	
</class-descriptor>

Also just note that it usually doesn't pay to proxy reference
descriptors since these can often be retrieved effeciently with one
query to the database.  Although it might make sense if you have a lot
of 1-1 relations that are not routinely used.  I usually proxy
collection descriptors though.
The query for the interface class is perfectly fine.
BTW is user really a 1-1 with group?  I would normally make this a 1-m
relation.
Hope this helps.
Wally
-----Original Message-----
From: Maksimenko Alexander [mailto:[EMAIL PROTECTED] 
Sent: Thursday, March 03, 2005 10:25 AM
To: OJB Users List
Subject: ojb and interface driven design

hi!
it's wondering but I found out that  its difficult to use interface 
driven design with ojb ;(
lets consider a simple 2-table example:

interface User{Integer getId(),Group getGroup()},
class UserImpl implements User{private Integer id; private Group group; 
access methods}

interface Group{Integer getId(),User getManager()},
class GroupImpl implements Group{private Integer id;privarte User 
manager; access methods}

What repository descriptor should be to get correct results with the 
following query:

QueryByCriteria query = QueryFactory.newQuery(User.class,new
Criteria());
query.getCriteria().addEqualTo("group.manager.id",new Integer(4));
Collection users = broker.getCollectionByQuery(query);
Standard approach in mapping is not working ;(
<class-descriptor 
	class="test.ojb.datamodel.User">
	<extent-class class-ref="test.ojb.datamodel.impl.UserImpl"/>
</class-descriptor>
<class-descriptor 
	class="test.ojb.datamodel.impl.UserImpl" 
	table="USER" 
	factory-class="test.ojb.datamodel.impl.FactoryImpl"
	factory-method="createUser">
	<field-descriptor 
		name="id" 
		column="ID" 
		jdbc-type="INTEGER"
		primarykey="true"
		nullable="false"
		autoincrement="true"
		access="readonly"/>	
	<field-descriptor 
		name="groupId"
		column="GROUP_ID"
		jdbc-type="INTEGER"
		access="anonymous"
	/>	
	<reference-descriptor
		name="group"
		class-ref="test.ojb.datamodel.Group"
		proxy="true"
	>
		<foreignkey field-ref="groupId"/>
	</reference-descriptor>	
</class-descriptor>

<class-descriptor 
	class="test.ojb.datamodel.Group">
	<extent-class class-ref="test.ojb.datamodel.impl.GroupImpl"/>
</class-descriptor>
<class-descriptor 
	class="test.ojb.datamodel.impl.GroupImpl" 
	table="GROUP1" 
	factory-class="test.ojb.datamodel.impl.FactoryImpl"
	factory-method="createGroup">
	<field-descriptor 
		name="id" 
		column="ID" 
		jdbc-type="INTEGER"
		primarykey="true"
		nullable="false"
		autoincrement="true"
		access="readonly"/>	
	<field-descriptor 
		name="managerId"
		column="MANAGER_ID"
		jdbc-type="INTEGER"
		access="anonymous"
	/>	
	<reference-descriptor
		name="manager"
		class-ref="test.ojb.datamodel.User"
		proxy="true"
	>
		<foreignkey field-ref="managerId"/>
	</reference-descriptor>	
</class-descriptor>


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