Sounds to me something related to the PreparedStatement cache. Do you
use c3po? If so did you specify hibernate.c3p0.max_statements?
Martijn
On Thu, 2008-07-24 at 23:26 -0400, Chris Lewis wrote:
> Ok, I've figured out what exactly is causing it and how to work around
> it. I can't say why, but perhaps a resident hibernate guru will know (it
> may even be a know issue or gotcha). First off, the quick fix. This
> query (and variations like load(), get(), and using the criteria api)
> cause the problem:
>
> Listing listing = (Listing)session.createQuery("from Listing lst
> where lst.id=:id")
> .setLong("id", Long.valueOf(sListingId)).uniqueResult();
>
> This works as expected:
>
> Listing listing = (Listing)session.createQuery("from Listing lst
> where lst.id=" + sListingId)
> .uniqueResult();
>
> It seems to come down to how hibernate handles the query results when
> the query is formed with a "raw" HQL string vs something like get(),
> load(), the criteria api, or using query parameters as I was initially
> doing. It also has something to do with the field being queried and
> seems to happen only on fields that exist in each of the tables. In my
> case the abstract super class Listing has the PK field "id", and the 2
> subclasses also have a PK field named "id." Querying by any method other
> than "constructed strings" leads to the issue, while querying on another
> field in the super class, whose name is unique to that class, works fine.
>
> So the BIG question is why in the world does it work the first time and
> continue to work until the value one queries by changes?
>
> I'd also like to know if anyone has seen this before, and/or if it's a
> known issue. I'm using a slightly outdated version of hibernate
> (3.2.2.ga) and for all I know this may be fixed in more recent versions.
> My wrists are shot so I'll try tomorrow. If anyone knows of this or gets
> interested/bored enough to try it, please let me know.
>
> Thanks tons for all of your input.
>
> Sincerely,
> Chris Lewis
>
> Chris Lewis wrote:
> > Hello,
> >
> > I have a dispatcher that uses a hibernate session. The dispatcher is
> > auto bound and receives the session in the constructor. I'm using
> > tapestry-hibernate so that session instance is a proxy that gets the
> > real session for the current thread (right?). Now in testing my
> > dispatcher, I give it a url like:
> >
> > /MyContext/?limg=2
> >
> > The dispatcher looks for "limg" and if found, queries the session
> > assuming that its value is the PK of a mapped entity. When I trigger the
> > dispatcher for the first time it works fine. If I refresh the page,
> > fine. If I change the value to something else, say 3, then it breaks
> > with a org.hibernate.InstantiationException:
> >
> > Cannot instantiate abstract class or interface: com.mypackage.data.Listing
> >
> > If I change the value back to 2, the same thing happens! "Listing" is an
> > abstract class mapped as a super class entity via:
> >
> > @Entity
> > @Inheritance(strategy = InheritanceType.JOINED)
> >
> > Any clue what's going on here? Two things are perplexing me:
> >
> > 1) Querying mapped super classes is legal, and I in fact the same thing
> > on my Index page with no problem.
> > 2) The query works the first time, but as soon as the id changes it is
> > forever broken until I restart the container.
> >
> > Thanks in advance!
> >
> > chris
> >
> >
>
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