[OJB-developers] n:m-Mapping with Extent

[<Joa...@tp...>]

Hy,

it's me again. I've finally hunted down the bug. Let me explain the
scenario:

I've got a class OneSide. Each object can have one or more ManySide
objects. This is implemented via a List with coresponding
CollectionDescriptor using a association-table (non-decomposed N:M-Mapping
in OJB-speak). Additionally there is a class named ManySideExtent, that
extends ManySide and is mapped to another table.

When I enable debugging in SqlGenerator I'll find the following messages
(after many others)  when loading a OneSide object:

[ojb.broker.accesslayer.SqlGenerator] DEBUG: SQL: SELECT
manyside.id,manyside.value FROM manyside, oneside_manyside WHERE
(oneside_id= ? )  AND oneside_manyside.manyside_id=manyside.id

this one looks quite correct and gets me the correct results (all ManySide
objects that belong to the one OneSide object), but the next one (which
tries to load the ManySideExtent objects) fails:

[ojb.broker.accesslayer.SqlGenerator] DEBUG: SQL: SELECT
manyside_extent.id,manyside_extent.value,manyside_extent.another_value FROM
manyside, oneside_manyside WHERE (oneside_id= ? )  AND
oneside_manyside.manyside_id=manyside.id

the problem here obviously is, that the wrong table is used in the
FROM-clause and the WHERE-clause. These come from the Query object, that is
created by the PersistenceBrokerImpl in getMtoNQuery. I think calling
getMtoNQuery with the ClassDescriptor of ManySideExtent for the second
query would solve the problem, the problem is, that the query is not built
in the function that decides wether we need to query for extents ...

Maybe a correct solution would be somewhere else altogether, but I don't
know enough about the system to see where.

regards
Joachim Sauer