Ian/Cedric,
Perhaps I am missing something, but it is fairly straghtforward to define
multiple entity beans that map to the same table. So these 'view' objects
can simply be entity beans that define only the needed fields. The only
thing that could conceivably get in the way of this is if your container
insists on calling ejbStore even when you haven't changed any of the
field values.
Ian McCallion wrote:
>
> Cedric Beust wrote:
> >
> > Hi Myles,
> >
> > > A problem with CMP is that it is an all or nothing approach regarding
> > > data access from the database. Ie. If you want to process a series of
> > > single fields from a selection of CMP entity beans you have no choice
> > > but to query for them and let the container load in all their data -
> > > even though you are interested in only the one field per entity bean.
> > >
> > > The spec should introduce data containers (I suppose 'value objects')
> > > that are views of a CMP entity bean. When defining a finder method,
> > > rather than it always returning a single CMP bean or a collection of CMP
> > > beans you can elect to return one of your data containers instead. The
> > > data container will simply be a subset of the fields of your CMP entity
> > > bean.
> >
> > I agree that this might be sometimes useful,
>
> Actually this is quite often useful - as anyone who has to implement a fuzzy
> search can tell you - the idea is to filter out as many of the instances as you
> can based on the search parameters, then present the users with a list of
> possibles to pick from. A list of PKs is not usually much use as a list of
> possibles - the users usually needs some data to corroborate with, hence the
> view.
>
> > but you don't need to amend the
> > specification to do that. What stops you from putting the intelligence
> > regarding these "view fields" into a Stateless Session Bean that would issue
> > the queries and pack the results into a value object before returning them
> > to you?
>
> A better approach than putting the intelligence into a SLSB is to put it into a
> Home Method of the Entity Bean. That way all the code needed to access that
> table is in the same EJB.
>
> ><SNIP>
>
> Ian McCallion
> Alexis Systems Limited
> Romsey, UK
>
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