Trying to figure out how to use Proxies - I've read all the information I can find but I'm still abit clueless. I get they are ways of lazy-loading so I don't have to instantiate my objects with every attribute (i.e. save sql calls).

Here's the scenario I'm trying to optimize:

I'm making a call to viewObject?id=5 where the id is the uid of the ClassA in the db (classA.getId() = 5).

I want to do something along the lines of:
ClassA classA = session.load ( ClassA.class, id );
Set attachments = classA.getAttachments();

I don't care to retrieve *any* of the actual properties for ClassA - just want to use the known Id to retrieve the attachments.

I could obviously do this in SQL as :
select * from tbAttachments where classId=5
but that's not very Hibernaty.

Now this would be easy if it wasn't for the fact that ClassA is extended by ClassB, ClassC, and ClassD. I frequently need to cast between these classes throughout the application. The combination of needing to be able to cast and wanting to use Proxies seems to be giving me a time.

Hibernate version: 2.x

I think you have 2 options.

One being to set lazy=true in the class hbm.xml. This is when the proxy is the class itself.

I believe then you'd need to call Hibernate.getClass() to retrieve the actual class. I can't recall how this affects the casting though.

If you need to do casting, for each class you want to proxy, specify lazy=true and the proxy interface to be a interface matching all the methods of the class itself. I just extracted interfaces using Eclipse. I believe this will work for casting.

I couldn't tell from the Documentation rather the Interface solution proxy="IClassA" fixes both the inability to cast subclassed proxies and the ability to compare class references

http://www.hibernate.org/hib_docs/refer ... ce-proxies

**Casting example where Proxy is the class itself
----------------------------------------------------------
Cat cat = (Cat) session.load(Cat.class, id); // instantiate a proxy (does not hit the db)
if ( cat.isDomesticCat() ) { // hit the db to initialize the proxy
DomesticCat dc = (DomesticCat) cat; // Error!
....
}

**Interface Casting example
----------------------------------------------------------
ICat cat = (ICat) session.load(Cat.class, catid);
Iterator iter = session.iterate("from cat in class eg.Cat where cat.name='fritz'");
ICat fritz = (ICat) iter.next();

Anyone have any ideas if I will be able to cast the ICat to an IAnimal and back and forth with the interfaces?