--- Aapo Laakkonen <[EMAIL PROTECTED]>
wrote:
> > I'm crossposting this to xdoclet-devel...
>
> Ok, but wait! This is not so easy to solve as I
> first thought.
>
> I attached examples:
> - User.java (User Interface)
> - UserImpl.java (User implementation that Hibernate
> should use)
>
> What I'm after is that I should not have to know
> UserImpl in anywhere in
> my code, expect when I'm creating a new User to db.
Well, I follow a slightly different approach -
I have complete separation of interface /
implementation, and DAO class which manages
creation/maniupulation and whatever necessary.
I'm doing content management /redaction system ,
and like to be in complete control over what happens.
So I have interfaces like Information / Version /
Content / Attributed / Keyworded - which describe my
content, and implementation classes which are hidden
in
separate package and are not public at all.
Manager takes over creation and manipulation of
objects.
This way I'm not bound to talk with people developing
frontends about database representation.
Hey, they are not in position to see database
identifiers :)
So they can create "user" , but they do not care what
implementation if back there.
> As you see, I use User.class to load object. That
> doesn't work, because
> the mapping is written for UserImpl ('cause it's the
> only possibility).
>
Well, you map class, you shall call it by name :)
> Now I'm asking Gavin about why does Hibernate need
> concrete
> implementation class? Hibernate already can generate
> proxy classes based
> on interface, then would it be possible to provide
> this same support for
> persistent classes altogether and make hibernate
> only to care about
> interfaces (of course current concrete class support
> should also be
> provided).
Actually you are not asking gavin, because you send
email to me directly :)
HIbernate needs conncrete implementation classes,
because it got to instantiate them. OK, you could
rig up some mock up with BCEL on the fly, or use proxy
+ interface - but normally you will use your pojo not
only for data storage, but also some bit of business
logic ( say, lifecycle stuff, which clearly belongs
there )
> > What shall we do with subclasses?
>
> What do you mean?
You may have noticed, that hibernate supports
polymorphic mappings . I use them for content
Every information version has content ( 1-1 mapping ),
and content is of base class Content, and concreate
subclasses are TextContent , BinaryContent or whatever
- they all live in the same table.
Though not necessary 5th normal form, but way easier
to manage.
And version.getContent() alvays delivers correct
type...
To be mapped, such polymorphic subclasses shall be
actual subclasses of base class. It would be PITA to
do this with interfaces...
regards,
=====
----[ Konstantin Pribluda ( ko5tik ) ]----------------
Zu Verstärkung meines Teams suche ich ab Sofort einen
Softwareentwickler[In] für die Festanstellung.
Arbeitsort: Mainz
Skills: Programieren, Kentnisse in OpenSource-Bereich
----[ http://www.pribluda.de ]------------------------
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