[hibernate-dev] [OGM] Precedence of options specified on different levels

[Gunnar Morling]

2013/12/16 Emmanuel Bernard <emmanuel at hibernate.org>

> On Mon 2013-12-16 11:06, Gunnar Morling wrote:
> > 2013/12/13 Emmanuel Bernard <emmanuel at hibernate.org>
> >
> > > So currently in the pull request, we now have the following
> > >
> > > 1. property > entity > global
> > > 2. for each level in 1., programmatic API beats annotation
> > >
> > > These are simple rules to understand and all it good.
> > >
> > > Now Gunnar tried to handle class inheritance, ie superclasses and
> > > overridden methods.
> > > And we do differ in what we consider the natural rules (or what it
> > > should be).
> > >
> > > Here is how I think the rules should be:
> > >
> > > 1. property > entity > global
> > > 2. for each level in 1., subclass > superclass and overridden method >
> > > parent method
> > > 3. for each level (in 1 and 2), programmatic API beats annotation
> > >
> > > Here is how Gunnar thinks the rules should be:
> > >
> > > 1. metadata on a class > metadata on a superclass (whether it is on a
> > > property or the class)
> > > 2. for each hierarchy level, property > entity > global
> > > 3. for each level in 1 and 2, programmatic API beats annotation
> > >
> > > In more concrete words,
> > >
> > >     @Option(1)
> > >     class A {
> > >         @Option(2)
> > >         public String getMe() {return null;}
> > >     }
> > >
> > >     @Option(3)
> > >     class B extends A {
> > >         @Override
> > >         public String getMe() {return null;}
> > >     }
> > >
> > > In my world, B.getMe has Options(2).
> > > In Gunnar's world, B.getMe() has @Option(3).
> > >
> >
> > Thanks for the clear explanation and example for the issue.
> >
> >
> > > To me, a property level is always more specific than an entity, hence
> my
> > > interpretation. If someone has set a value on a given property, it
> would
> > > be dangerous to be "globally" overridden by a subclass.
> > >
> > > Thoughts?
> > >
> >
> > What would be "dangerous" in this case?
>
> Someone has clearly decided that A.getMe should behave in a specific way
> and differently than A.getOtherMe. Overriding that via B for all of A's
> properties is wrong IMO. Besides, why doesn't it override the settings
> for properties that are not overridden?
>
> >
> > I think for the author of B it's helpful to be able to change the
> defaults
> > for the entire class. Also for a reader of B its simpler to grasp the
> > applying configuration with my proposal, because the entire "truth" about
> > the annotation config can be found in B, you don't have to look into any
> > super-classes. So to me, that's more along the lines of the principle of
> > least surprise.
> >
>
> If you consider that the truth should be in the most specific entity, I
> think
> you should also consider that inheriting the settings from the
> superclass is against that principle and that inheritance should not be
> involved.
>

Ok, let's do it then the way you and Davide prefer. I'll update the
algorithm in the PR.


>
> Emmanuel
>