Hibernate version:All versions

I've been working a lot with some fat objects recently and it has really got me thinking about a really cool feature that hibernate could do with ...

A flyweight upcasting filter.

Ok an example ....

IdAndTitleInterface {
Integer id;
String title;
}

MyFatClass implements IdAndTitleInterface {
Integer id;
String title;
100 other methods and variables.
}

IdAndTitleInterface idat = session.findWithInterfaceFilter("from MyFatClass",IdAndTitleInterface.class ) ......

So then hibernate wouldn't load up everything, just those 2 properties.

My idea is that this would only be used for read only objects.

The advantages would be ...

1) Faster for remote clients

2) Reduction of extraneous loading and would be simpler than lazy loading

3) Simpify stuff

4) You could have a couple of diffferent interfaces for the different users of your service/class

I'm not that experienced with hibernate but the only other way i could think
of doing it was something like this ....

select propertyimage.id,propertyimage.title from PropertyImage as
propertyimage where propertyimage.associatedProperty.id = ?
ORDER BY propertyimage.index ASC

Then iterating through the results and adding them into some DTO
class ... but that strikes me as not as elegant.

or I could do this ...

select propertyimage from PropertyImage as propertyimage where propertyimage.associatedProperty.id = ? ORDER BY propertyimage.index ASC

Then cast them to the shorter interface but this still hits the database a
lot where it isn't strictly necessary.

Perhaps I'm missing something but this seems like a good idea to me.

--b

This is how I currently do it. This would be tedious to replicate in a
hundred or so functions.

public List getIImageIdAndTitleAssociatedWithProperty(Long propertyId) {

List list = getHibernateTemplate().findByNamedQuery("ImageIdIndexAndTitlesAssociatedWithAProperty",propertyId);
List propList = new ArrayList();
Iterator iterator = list.iterator();
while (iterator.hasNext()) {
Object object[] = (Object[]) iterator.next();
Long id = (Long) object[0];
String title = (String) object[1];
Integer index = (Integer) object[2];

ImageIndexAndTitlePropertyImageDTO obj = new ImageIndexAndTitlePropertyImageDTO(id,title,index);
propList.add(obj);
}
return propList;
}

Not one comment ... I guess my idea sucked !

--b

"SELECT new ImageIndexAndTitlePropertyImageDTO(id,title,index) ... "

Wait a second , your telling me that works with hibernate 2.16 ?

--b

of course - read the docs

It does !!!!!! Hibernate is even better than i thought !!! You guys are the
best !!!!

--b

Ok been playing arround with this and it doesn't seem to understand
construtor args that are collections.

Doesn't work ( descriptions is a map )
select property.descriptions from Property as property

Works
select elements(property.descriptions ),indices(property.descriptions ) from Property as property

Doesn't work
select new ie.jestate.bo.property.PropertySummaryDTO(property.id, property.descriptions ,property.summaryDescriptions ) from Property as property

Generates this error message

net.sf.hibernate.QueryException: expecting 'elements' or 'indices' after: id [select new ie.jestate.bo.property.PropertySummaryDTO(property.id, property.descriptions ,property.summaryDescriptions ) from ie.jestate.bo.property.Property as property]

Am I missing something or is this normal behaviour, are there any plans
to implement this ?

It strikes me as a neat feature.

--b

This is normal, afaik it is not planned to implement this.

I've been checking the hibernate 3.0 source code and there is no
reference to this.

It is a shame there is no plans to support this as I have tried to
design my application for easy internationalization and as a result
I am storing almost all my descriptions as java.util.Maps.

If I was to send the full object out to the web tier it would be far to
fat and cause scalablity issues.

I guess I'm back to square one on this one.

Thanks for your help anyhows.

--b

This would be very, very difficult to implement.

Gavin,

Ok I've been thinking about this but it's 3am over here so just in case my
reply comes out as complete nonsense I'm going to read it in the morning
before sending it.

I'm impressed that you think it would be difficult to implement though as
by all accounts you seem to be a top notch coder.

I dont really understand the internals of hibernate all that clearly but I
think I will try to learn a little more about them.

From a performance standpoint I think that this would make things
a lot more performant as you would not need to wrap each
map in a persistant class.

If you think of the possibilities it would be so cool if you could
custom wrap query results so that you never need to pass back
a class which is one variable larger than necessary without
going through the tedium of wrapping it yourself.

Although I'm a big fan of object mapping I've still got the old school
mentality of every byte counts and I need to come up with a plan to
lighten up my session storage requirements.

Thanks for taking the time to look at this.

--b

Perhaps I misunderstood what you want, it's not clear.

Does the last argument of PropertySummaryDTO() constructor take a collection, or a single summaryDescription?

P.S. Flattery will get you everywhere - it's such an underrated tool :-)

descriptions and summaryDescriptions are both maps.

I'm gonna wrap them in pojo's though, they will work that way
wont they ?

I do have the utmost respect for your work though, I don't know if
your a unix guy as well but I notice one of your compatriots
( Tridgell ) seems to be fairly busy with samba4 right now, another
great project might I add.

Anyhow I really am gonna have to crash now, have a good weekend
and thanks for taking the time to check this out.

--b