Jumping in late, but its germane to what I'm working on. So, if I read what everyone
is saying correctly, the following:
<class-descriptor class="polymorphtest.InterfaceA">
<extent-class class-ref="polymorphtest.A" />
<extent-class class-ref="polymorphtest.B" />
<extent-class class-ref="polymorphtest.C" />
</class-descriptor>
<class-descriptor class="polymorphtest.A" table="A_TABLE">
<extent-class class-ref="polymorphtest.B" />
<field-descriptor name="id" column="ID" jdbc-type="INTEGER"
primarykey="true" autoincrement="true" />
<field-descriptor name="someValueFromA" column="VALUE_"
jdbc-type="INTEGER" />
</class-descriptor>
<class-descriptor class="polymorphtest.B" table="B_TABLE">
<field-descriptor name="id" column="ID" jdbc-type="INTEGER"
primarykey="true" autoincrement="true" />
<field-descriptor name="someValueFromB" column="VALUE_"
jdbc-type="INTEGER" />
<reference-descriptor name="super" class-ref="polymorphtest.A">
<foreignkey field-ref="id" />
</reference-descriptor>
</class-descriptor>
<class-descriptor class="polymorphtest.C" table="C_TABLE">
<field-descriptor name="id" column="ID" jdbc-type="INTEGER"
primarykey="true" autoincrement="true" />
<field-descriptor name="someValueFromC" column="VALUE_"
jdbc-type="INTEGER" />
</class-descriptor>
does not do what I would expect? :
1. Queries for collections of InterfaceA would give me all the A's, B's, and C's.
2. Queries for collections of A's would give me A's and B's, but the A's would be only
those rows in A_TABLE that did not have matching keys in B_TABLE.
3. If I queried for an A, but there is a B that matches, I'd get a B and not just an A.
4. Anytime B's are materialized, they would have their inherited properties from the
super class A populated.
Sorry if this is a re-hash, but I'm getting a little confused ATM. Thanks for any
clarifications.
> -----Original Message-----
> From: Jakob Braeuchi [mailto:[EMAIL PROTECTED]
> Sent: Friday, October 17, 2003 12:09 PM
> To: OJB Users List; Thomas Mahler; Armin Waibel
> Subject: Re: Wrong class materialized when selecting from an extent
> mapped to a multi-table join
>
>
> hi justis, wallace,
>
> this problem is caused by Identity#equals noch checking
> objectsRealClass
> . consider the following situation: a select for InterfaceA
> fires 2 selects
> SELECT A0.VALUE_,A0.ID FROM A_TABLE A0
> retrieving Table_A objects with ids 1 and 2
> SELECT A0.VALUE_,A0.ID FROM B_TABLE A0 INNER JOIN A_TABLE A1
> ON A0.ID=A1.ID
> retrieving Table_B object with id 1
>
> when building the objects from the resultset in
> RsIterator#getObjectFromResultSet an identity is built from
> the row and
> looked up in the cache. the object (id = 1) from table_B is
> considered
> to be in the cache because the topLevelClass (InterfaceA) and
> the pk (1)
> matches !
>
> this problem could be solved by also checking the objectsRealClass in
> Identity#equals. i remember there was quite a big discussion about
> Identity, so i'm not sure if this is a correct soluion ??
>
> another solution could be to use a dedicated column to refer to the
> super-class in the reference-descriptor. this would avoid the
> pk-clash
> in the cache.
>
> another way is to completly avoid using extents and
> super-references ;)
>
>
> <class-descriptor class="polymorphtest.InterfaceA">
> <extent-class class-ref="polymorphtest.A" />
> <extent-class class-ref="polymorphtest.B" />
> </class-descriptor>
>
> <class-descriptor class="polymorphtest.A" table="A_TABLE">
> <field-descriptor name="id" column="ID" jdbc-type="INTEGER"
> primarykey="true" autoincrement="true" />
> <field-descriptor name="someValueFromA" column="VALUE_"
> jdbc-type="INTEGER" />
> </class-descriptor>
>
> <class-descriptor class="polymorphtest.B" table="B_TABLE">
> <field-descriptor name="id" column="ID" jdbc-type="INTEGER"
> primarykey="true" autoincrement="true" />
> <field-descriptor name="someValueFromB" column="VALUE_"
> jdbc-type="INTEGER" />
> <reference-descriptor name="super" class-ref="polymorphtest.A">
> <foreignkey field-ref="id" />
> </reference-descriptor>
> </class-descriptor>
>
> jakob
>
> Justis Peters wrote:
>
> > Hi All!
> >
> > Just a couple weeks ago I started using OJB, and I am
> extremely impressed. My gratitude goes to all who put in the
> work to make it possible.
> >
> > Upon converting some of the more complicated parts of my
> object model, I encountered a strange issue. Here is the bug
> I attempted to submit to scarab. Apparently, scarab is
> having problems. At first, it assigned an ID to my issue
> that was already assigned to another issue, so I can't
> retrieve it. Now, it won't let me enter new issues and keeps
> directing me to the query page isntead.
> >
> > Anyhow, here is the summary of the bug. Any help would be
> appreciated:
> >
> >
> ==============================================================
> ============
> > When selecting an entire extent from a parent class, the
> behavior varies depending on whether you are using
> multi-table joins or distinct tables for each class.
> Everything seems to work correctly if you use distinct tables
> for each class. If you are using multi-table joins, however,
> your objects are not always materialized as the class you
> would expect. Here is the scenario for the test case I made:
> >
> > Object model
> > ------------
> > - public interface InterfaceA
> > - public class A implements InterfaceA
> > - public class B extends A implements InterfaceA
> >
> > Test case 1
> > -----------
> > - start with a new JVM
> > - select all from extent InterfaceA.class, loop through and
> display the class for each
> > - select all from extent A.class, loop through and display
> the class for each
> > - select all from extent B.class, loop through and display
> the class for each
> >
> > Test case 2
> > -----------
> > - restart with a new JVM
> > - select all from extent B.class, loop through and display
> the class for each
> > - select all from extent A.class, loop through and display
> the class for each
> > - select all from extent InterfaceA.class, loop through and
> display the class for each
> >
> > Results
> > -------
> > - If using distinct tables for each class (see schema1.sql
> and repository_user1.xml), both test cases materialize all
> objects as the correct subclass and returns the expected
> instances with the appropriate queries.
> > - If using multi-table joins (see schema2.sql and
> repository_user2.xml), test case 1 displays everything as
> being class "A", even if it was a "B". Instances of "B" are
> retrieved and displayed twice in the queries for "InstanceA".
> Once you get to querying for "B", it turns up absolutely no
> instances. I imagine this is because it is cached. Test
> case 2 correctly materializes the objects a "B" and "A",
> depending on which table they appear in; when you query
> against InterfaceA.class, however, it still displays the
> duplicates for instances of "B".
> >
> >
> > For convenience in debugging, I have written a command-line
> test that lets you choose the order in which the extents are
> retrieved and displayed. You can run it by doing:
> > java polymorphtest.PolymorphTest 0 1 2 (test case 1)
> > OR
> > java polymorphtest.PolymorphTest 2 1 0 (test case 2)
> >
> >
> > All the related classes, schemas, and O/R mappings are
> attached to this bug. Please contact me if you need help
> reproducing the errors.
> >
> > ================================================================
> >
> > I don't want to send the attachments to the whole list, but
> I will be glad to email the tarball to whomever requests it.
> Thanks in advance for your help!
> >
> > Sincerely,
> > Justis Peters
> > Oculan Corp.
> > [EMAIL PROTECTED]
> >
> >
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> >
> >
>
>
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