Hello Markus,
This customization is both in TopLink and TopLink Essentials. It does require use of TopLink API directly and is not exposed through the JPA. It is the user's responsibility to either treat the class as readonly or mark all of the mappings read-only (updatable, insertable = false in JPA).
The best way to map this relationship is as a OneToOne.
--Gordon
-----Original Message-----
From: Markus.Fuchs_at_Sun.COM [mailto:Markus.Fuchs_at_Sun.COM]On Behalf Of
Markus Fuchs
Sent: Thursday, August 03, 2006 2:14 PM
To: Gordon Yorke
Cc: persistence_at_glassfish.dev.java.net
Subject: Re: Outer joins for secondary tables?
[including a broader audience]
Hi Gordon,
Thanks for your information! I have a couple of further questions:
Gordon Yorke wrote:
> Hello Markus,
> In TopLink a user can customize the MultipleTableJoinExpression in
> the DescriptorQueryManager. TopLink uses this expression when
> joining, updating this expression to use outer joins will cause
> TopLink to use outerjoins for secondary tables.
>
>
>
Is this customization a TopLink product feature? I understand it is not
part of TopLink-Essentials.
> This method, however, will only work for read-only objects as
> TopLink will be unable to update any secondary fields for objects that
> did not have a row in the secondary table. TopLink has no way of
> determining if the row was there once the object was built. Having
> this functionality would be a very large undertaking and would
> proportionally be of little value.
>
>
>
Does customizing the MultipleTableJoinExpression make the entity
read-only automatically or is it the user's responsibility to treat that
class as read-only? If the class is read-only automatically, would it be
possible to treat only the fields actually mapped to the secondary table
as read-only? In a JPA context, would it be sufficient to mark the
secondary table fields "updatable=false"?
Thanks!
-- markus.
>This sort of relationship should be mapped as an OneToOne.
>
>--Gordon
>
>-----Original Message-----
>From: Markus.Fuchs_at_Sun.COM [mailto:Markus.Fuchs_at_Sun.COM]On Behalf Of
>Markus Fuchs
>Sent: Wednesday, August 02, 2006 7:27 PM
>To: Tom Ware; Gordon Yorke
>Subject: Outer joins for secondary tables?
>
>
>Hi Tom, Gordon,
>
>I remember from one telephone meeting that TopLink can be switched
>from generating inner joins for secondary tables to outer
>joins.
>
>Looking into the code, I couldn't find such option. What am I missing?
>I couldn't even find an indicator in ClassDescriptor like
>"hasSecondaryTableMapping()". Is it possible to assume that the class
>has secondary table mappings, that if
>ClassDescriptor#additionalTablePrimaryKeyField != null?
>
>Thanks so much,
>
>-- markus.
>
>
>
>