Hello, I tried out the problem again by making changes to the class-descriptors and schema as per Armin's suggestions and the "Advanced O/R Mapping Technique" tutorial (Apache OJB site). However the persistence broker still returns instances of Thing class instead of the Book and Toy in the stuffInDrawer collection of the Drawer class.
If there are any aspects that I might have over-looked, please point them out. Note that Thing is a concrete class in my case. I am thinking about modifying the OJB source code to fix this extent-awareness problem satisfactorily. However I would need some guidance in helping me understand how OJB creates SQLs in context of repository.xml (descriptors) and how RowReader and RsIterator is used in creating instances of concrete classes. Could any please help me understand the concepts related to SQL building, RowReader and RsIterator and how the current implementation behaves ? Does anyone have a sequence-diagram / activity diagram to illustrate the logic involved ? I am thinking on the lines of using the class-descriptor to look out of extent-class definitions for the class whose data in being read and in the process of being materialized. If I find an extent-class, I would then look in to the table mapped to this extent class for row-entry (using PK or PK/FK as the search criteria) and then decide which object instance to materialize. I am not sure if this is the right way to go. Any advise or help on this is highly appreciated. Thank you for all the support. Regards, Gautam. On Wed, 22 Nov 2006 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 ? 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. > >> > >> > >> > > > >--------------------------------------------------------------------- > >To unsubscribe, e-mail: [EMAIL PROTECTED] > >For additional commands, e-mail: [EMAIL PROTECTED] > > > > >
