[News.eclipse.technology.eclipselink] Re: Switching Maya to JPA / Eclips

[shaun.smith@xxxxxxxxxx (Shaun Smith)]

Timothy Webb wrote:

> > > In my use of TopLink Essentials in RCP I was using the internal connection 
> > > pooling without any problems but I didn't have long periods of idle time 
> > > so I never experienced any timeout problems.  Are you using the built in 
> > > connection pooling or are you using you're container's connection pool?
> >
> > We are using the internal connection pooling since currently not running 
> > within a container.

There was a similar question posted to the TopLink forum you might want to 
look at.  
http://forums.oracle.com/forums/thread.jspa?threadID=537599&tstart=0

> > This was a very helpful reference and following it I've been able to get 
the 
> > desired caching behavior.  One quirk I've noticed is that if I issue a 
native 
> > query bound to a particular object, and only request the primary key field, 
> > the object has all fields empty even if the object was already populated in 
> > the cache.  Is this the expected behavior?

Yes, it is if you're just selecting the id using a native query and 
getting objects back.  More below on this.

> >  Or asking it another way, what 
> > would you recommend if I wanted to get the current list of objects from the 
> > DB, but the objects were large so I would rather not load all of the fields 
on 
> > each request assuming the objects are already in the cache? 

I'd just select only those attributes of a set of objects you want and, 
for convenience sake, build an object to hold those attributes.  Take a 
look at section 4.8.2 of the JPA spec for an example.  This is useful in 
cases where you want to populate a drop down in the UI and don't want to 
load the entire object.


> > I've tried 
> > executing a native query with response time as Vector and then doing 
> > subsequent queries, or an IN clause, but this seems a bit ugly.

I find native queries very complicated and avoid them.  If you've mapped 
your classes you should be able to get what you want with JPQL.  We can 
take this offline if you like and you can email me your query?

--Shaun