I'm not really sure why you don't use a regular java bean object to do this.
However, I believe you could create a DataMap for all of these objects
in a separate DataNode. You don't have to create a table for them in
the database.
You might even be able to get away with having them in the same
DataMap, provided you don't try to update/insert/delete them during a
commit. There's no requirement that you create an actual table on
the database unless you execute sql accessing that table.
On 5/19/08, Adrian Wiesmann <awiesman..omap.org> wrote:
> On Mon, 19 May 2008 09:19:26 +1000
> Aristedes Maniatis <ar..sh.com.au> wrote:
>
> > There should be something coming soon with inheritance, but there were
> > no plans to support persistent objects with no database backing at
> > all. There is going to be the opposite concept: abstract classes which
> > have a database table, but which can only be constructed in their
> > subclass.
> >
> > Tell us more about why it would be useful to have data objects which
> > cannot be persisted to the database.
>
>
> I guess my usage scenario is very specific to my environment. But let me
> introduce my environment and let you decide.
>
> I have written a UI renderer and data binding engine (Gozer). For that
> engine to work I introduced the Domain Model, Table Module and Record Set
> patterns and DataObjectKeys to Cayenne (at least to some extent). I did so
> with my own code generator which generates datarows, datarowkeys and table
> modules to every ObjEntity modeled with the Cayenne modeler.
>
> For the data binding I use then these table modules. Let's say I have a
> table with users. I can then bind that table to the UI like that:
>
> <list databinding=..ser">
> <list_field databinding="username" />
> </list>
>
> My UI engine is interpreting the binding information so that the UI
> renders a list of users with the only field in the list containing the
> username.
>
> Which means that whenever I display data on the UI, I am using the same
> databinding which makes use of my datatable and datarow objects.
>
> Now to the QueryTable problem: Many applications have some form of user
> input where a user can enter search criteria and then use that criteria to
> filter a list of records or search data in the database. Since my UI
> engine knows how to render my table modules and datarows, I would love to
> use the same mechanism for query interfaces (a huge time saver).
>
> To extend my example from above: I could introduce a UserQueryTable with a
> field UserName. I could then define a view which binds that table. The
> user enters a username and when clicking on the search button I could read
> the content from the UserQueryTable and construct the query from the
> content of that table. Side effect, all my queries would be
> "standardised" and whenever I need to search for users in my application
> I can use the same interface (UserQueryTable) which is then sent to the
> UserQuery Business Object which handles the querying in a central
> location (domain model pattern).
>
> Of course I could solve that problem in creating ObjEntity which have
> a corresponding table in the database (which is never used). But I find
> this to be very ugly...
>
> Hope this explained my scenario.
>
> Cheers,
>
> Adrian
>
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