Re: [eclipselink-users] Discriminator and Inheritance.strategy

["Guy Pelletier" <guy.pelletier@xxxxxxxxxx>]

Hi Michael,

Further to Chris' reply, in your case you may want to look at specifying a 
descriptor customizer and setting a class extractor which will avoid using 
the discriminator column.

More info here on building a customizer:

http://wiki.eclipse.org/Customizing_the_EclipseLink_Application_%28ELUG%29


Cheers,
Guy

----- Original Message ----- 
From: "Michael Simons" <michael.simons@xxxxxxxxxxx>
To: "Guy Pelletier" <guy.pelletier@xxxxxxxxxx>; "EclipseLink User 
Discussions" <eclipselink-users@xxxxxxxxxxx>
Sent: Friday, November 27, 2009 8:23 AM
Subject: Re: [eclipselink-users] Discriminator and Inheritance.strategy


> Hello Guy,
>
> unfortunately we have the Inheritance.JOIN strategy.
> I don't understand why there's a discriminator needed for this strategy 
> because which class an
> object is instance of is determined by the entry in the "sub"-table, isn't 
> it?
>
> kind regards,
> Michael
>
> Guy Pelletier schrieb:
> > A discriminator column is not needed for a TABLE_PER_CLASS strategy.
> >
> > The discriminator column is used to determine which class of object that
> > row represents.
> >
> > Cheers,
> > Guy
> >
> > ----- Original Message ----- From: "Michael Simons"
> > <michael.simons@xxxxxxxxxxx>
> > To: <eclipselink-users@xxxxxxxxxxx>
> > Sent: Friday, November 27, 2009 6:33 AM
> > Subject: [eclipselink-users] Discriminator and Inheritance.strategy
> >
> >
> > > Hello,
> > >
> > > I'm trying to port a client/server application first to JPA to enable
> > > the 3-tier migration.
> > > At the moment I try to use EclipseLink as JPA implementation.
> > > The first exception I fall over said "Unknown column 't2.DTYPE' in
> > > 'field list'"
> > >
> > > Seems like EclipseLink always needs a discriminator column even if the
> > > inheritance strategy is
> > > JOIN or TABLE_PER_CLASS.
> > > Is this correct?
> > > And if so, what is it good/needed for?
> > >
> > > [EclipseLink 1.2.0, database=MySQL 5]
> > >
> > > Kind Regards,
> > > Michael
> > > _______________________________________________
> > > eclipselink-users mailing list
> > > eclipselink-users@xxxxxxxxxxx
> > > https://dev.eclipse.org/mailman/listinfo/eclipselink-users
> >
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