Re: Re: OJB not returning the correct child types.

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 ? Wouldn't this be illegal in SQL ?

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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