[Hibernate] RE: session.filter(Collection, Predicate)?

[Anton v. S. <an...@ap...>]

I realized in the cold light of day that what I was asking about below can't
possibly work unless the object being filtered has already been fully
loaded, which I presume would defeat the purpose of the filter.  Is that
correct?


> -----Original Message-----
> From: Anton van Straaten [mailto:an...@ap...]
> Sent: Friday, September 13, 2002 1:45 AM
> To: hibernate list
> Subject: session.filter(Collection, Predicate)?
>
>
> > Accordingly Ive added filtering
> > methods to the Session interface like:
> >
> >   filteredCollection = session.filter(collection, query)
> >
> > A filter is just a query where you can refer to "this", the collection
> > element. So, for example:
> >
> >   blackCats = session.filter( cat.getKittens(), "where
> this.color='black'
> > order by this.name" );
>
> Slightly tangential question about this: how straightforward (or
> not) would it be to support an object as the filter parameter?  I
> use a Predicate interface in my own code:
>
> public interface Predicate {
> 	// Apply predicate to a specified object and return boolean result
> 	boolean apply(Object o);
> }
>
> This can be used to create arbitrary objects to filter on any
> condition - I use it for filtering Java collections and arrays.
> You can also use it inline, e.g.:
>
> 	blackCats = session.filter( cat.getKittens(), new Predicate() {
> 		public boolean apply(Object o) {
> 			return o.color.equals("black");
> 		}
> 	});
>
> I don't know anything about what Hibernate is doing when it's
> retrieving & filtering a query - if something like this wouldn't
> require too much internal rearranging, I might take a stab at it,
> since it would fit in with some of the other code I'm using.  In
> fact it came up in some code which I've just installed for
> testing, and I ended up building a query string to do it instead.
>  In some cases, I prefer the approach I've described since it's
> subject to static checking, supports refactoring, etc.
>
> Anton
>