Re: OJB not returning the correct child types.

Hi Gautam,

Virgo Smart wrote:
> Hello Armin,
> 
> Apologies for posting a repeat of a similar problem as mentioned in an earlier post. 
> I had already posted this one before I recieved the reply to the earlier one.
> 
> Looking at the modified class descriptor, I see that the extent-class and anonymous 
> fields are being dropped. 
> I think this is ok. However I am not sure if the "super" reference descriptor can point 
> to the primary key field descriptor of the parent class.
> Wouldn't this mean that the PK in the BOOKS / TOYS table would also need to be a 
> FK pointing to the PK of the THINGS table ? 

OJB doesn't handle a "super"-reference like a normal 1:1 reference. It 
is not possible to delete or insert only "one part of a super-reference 
hierarchy" of a Books/Toys object. Thus the referential integrity of the 
DB tables is always guaranteed.


> Wouldn't this be illegal in SQL ?
>

I don't know. Isn't it a special case of a 1:1 reference (the FK is used 
as PK)? I use constraints in my test tables and don't have problem with 
any DB I use in tests.

regards,
Armin

> Thanks and Regards,
> Gautam  
> 
> 
> On Wed, 22 Nov 2006 Armin Waibel wrote :
>> Hi Gautam,
>>
>> as said in my previous post in thread "OJB: Identity equals method impl." you should use the "normal" TPS inheritance without a FK field and without "extent-class" declaration within TPS (and don't override fields in the sub-classes):
>>
>> <class-descriptor
>>     class="Thing"
>>     table="THINGS">
>>
>>     <field-descriptor
>>         name="id"
>>         column="ID"
>>         jdbc-type="INTEGER"
>>         primarykey="true"
>>         autoincrement="true"
>>         />
>>
>>     <field-descriptor
>>         name="name"
>>         column="NAME"
>>         jdbc-type="VARCHAR"
>>         size="255"
>>         />
>>
>>     <field-descriptor
>>         name="drawerId"
>>         column="DRAWER_ID"
>>         jdbc-type="INTEGER"
>>         access="anonymous"
>>         />
>>
>> </class-descriptor>
>>
>> <class-descriptor
>>     class="Toy"
>>     table="TOYS">
>>
>>     <field-descriptor
>>         name="id"
>>         column="ID"
>>         jdbc-type="INTEGER"
>>         primarykey="true"
>>         autoincrement="false"
>>         />
>>
>>     <field-descriptor
>>         name="category"
>>         column="CATEGORY"
>>         jdbc-type="VARCHAR"
>>         size="255"
>>         />
>>     </field-descriptor>
>>
>>     <reference-descriptor
>>         name="super"
>>         class-ref="Thing"
>>     >
>>         <foreignkey field-ref="id"/>
>>     </reference-descriptor>
>>
>> </class-descriptor>
>>
>> <class-descriptor
>>     class="Book"
>>     table="BOOKS">
>>
>>     <field-descriptor
>>         name="id"
>>         column="ID"
>>         jdbc-type="INTEGER"
>>         primarykey="true"
>>         autoincrement="false"
>>         />
>>
>>     <field-descriptor
>>         name="author"
>>         column="AUTHOR"
>>         jdbc-type="VARCHAR"
>>         size="255"
>>         />
>>
>>     <field-descriptor
>>         name="isbnCode"
>>         column="ISBN_CODE"
>>         jdbc-type="VARCHAR"
>>         size="255"
>>         />
>>
>>     </field-descriptor>
>>
>>     <reference-descriptor
>>         name="super"
>>         class-ref="Thing"
>>     >
>>         <foreignkey field-ref="id"/>
>>     </reference-descriptor>
>>
>> </class-descriptor>
>>
>>
>> <class-descriptor
>>     class="Drawer"
>>     table="DRAWER">
>>
>>     <field-descriptor
>>         name="id"
>>         column="id"
>>         jdbc-type="INTEGER"
>>         primarykey="true"
>>         autoincrement="true"
>>         />
>>
>>     <collection-descriptor
>>         name="stuffInDrawer"
>>         element-class-ref="Thing"
>>         >
>>         <inverse-foreignkey field-ref="drawerId"/>
>>     </collection-descriptor>
>> </class-descriptor>
>>
>>
>> The FK field "drawerId" in class Thing (of the 1:n reference in Drawer) is declared as anonymous. Please read carefully the section about how anonymous keys work to avoid problems
>> http://db.apache.org/ojb/docu/guides/advanced-technique.html#How+do
>>
>> regards,
>> Armin
>>
>> Virgo Smart wrote:
>>> Hello,
>>>
>>> I am facing an issue when trying to retrieve the Drawer object.
>>> Instead of retrieving a collection of Toy and Book instances in the stuffInDrawer attribute, collection containing Thing instances is returned.
>>>
>>> Following is the class descriptor that is used.
>>>
>>> <class-descriptor
>>>     class="Thing"
>>>     table="THINGS">
>>>
>>>    <extent-class class-ref="Toy"/>
>>>    <extent-class class-ref="Book"/>
>>>
>>>     <field-descriptor
>>>         name="id"
>>>         column="ID"
>>>         jdbc-type="INTEGER"
>>>         primarykey="true"
>>>         autoincrement="true"
>>>         />
>>>
>>>     <field-descriptor
>>>         name="name"
>>>         column="NAME"
>>>         jdbc-type="VARCHAR"
>>>         size="255"
>>>         />
>>>
>>>     <field-descriptor
>>>         name="drawerId"
>>>         column="DRAWER_ID"
>>>         jdbc-type="INTEGER"
>>>         access="anonymous"
>>>         />
>>>
>>> </class-descriptor>
>>>
>>> <class-descriptor
>>>     class="Toy"
>>>     table="TOYS">
>>>
>>>     <field-descriptor
>>>         name="id"
>>>         column="ID"
>>>         jdbc-type="INTEGER"
>>>         primarykey="true"
>>>         autoincrement="true"
>>>         />
>>>
>>>     <field-descriptor
>>>         name="category"
>>>         column="CATEGORY"
>>>         jdbc-type="VARCHAR"
>>>         size="255"
>>>         />
>>>
>>>     <field-descriptor
>>>         name="parentThingId"
>>>         column="THING_ID"
>>>         jdbc-type="BIGINT"
>>>         access="anonymous"
>>>     >
>>>     </field-descriptor>
>>>
>>>     <reference-descriptor
>>>         name="super"
>>>         class-ref="Thing"
>>>     >
>>>         <foreignkey field-ref="parentThingId"/>
>>>     </reference-descriptor>
>>>
>>> </class-descriptor>
>>>
>>> <class-descriptor
>>>     class="Book"
>>>     table="BOOKS">
>>>
>>>     <field-descriptor
>>>         name="id"
>>>         column="ID"
>>>         jdbc-type="INTEGER"
>>>         primarykey="true"
>>>         autoincrement="true"
>>>         />
>>>
>>>     <field-descriptor
>>>         name="author"
>>>         column="AUTHOR"
>>>         jdbc-type="VARCHAR"
>>>         size="255"
>>>         />
>>>
>>>     <field-descriptor
>>>         name="isbnCode"
>>>         column="ISBN_CODE"
>>>         jdbc-type="VARCHAR"
>>>         size="255"
>>>         />
>>>
>>>     <field-descriptor
>>>         name="parentThingId"
>>>         column="THING_ID"
>>>         jdbc-type="BIGINT"
>>>         access="anonymous"
>>>     >
>>>     </field-descriptor>
>>>
>>>     <reference-descriptor
>>>         name="super"
>>>         class-ref="Thing"
>>>     >
>>>         <foreignkey field-ref="parentThingId"/>
>>>     </reference-descriptor>
>>>
>>> </class-descriptor>
>>>
>>>
>>> <class-descriptor
>>>     class="Drawer"
>>>     table="DRAWER">
>>>
>>>     <field-descriptor
>>>         name="id"
>>>         column="id"
>>>         jdbc-type="INTEGER"
>>>         primarykey="true"
>>>         autoincrement="true"
>>>         />
>>>         <collection-descriptor
>>>         name="stuffInDrawer"
>>>         element-class-ref="Thing"
>>>         >
>>>         <inverse-foreignkey field-ref="drawerId"/>
>>>     </collection-descriptor>
>>> </class-descriptor>
>>>
>>>
>>> I have used the table per subclass hierarchy strategy.
>>> I have used SequenceManagerHighLowImpl as the sequence manager. The ids (ID column) in the TOYS and BOOKS tables are unique when the Drawer object is stored. In the sense, when a Drawer containing 3 things (2 books and 1 toy) is stored, the ids stored in THINGS table are 1, 2, and 3, where as the ids stored in BOOKS table are 1 and 2 and id stored in the TOYS table is 3.
>>>
>>> I hope I have provided sufficient details to debug the issue. Could anyone please point me as to where am I going wrong or if there is any way to circumvent the problem ?
>>>  Thanks and Regards,
>>> Gautam.
>>>
>>>
>>>  
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> 
> 
>  
>