RE: [Hibernate] Lazy Collections

[Gavin K. <Gav...@ex...>]

Where are connections coming from? A Hibernate ConnectionProvider? Or an
application supplied connection?

What guarantees does Maverick make about when / wether discard() will be
called? Is it *guaranteed* to be called in the case of an exception,
etc?

> -----Original Message-----
> From: Aapo Laakkonen [mailto:aap...@pr...]=20
> Sent: Thursday, 5 December 2002 12:35 AM
> To: hib...@li...
> Subject: FW: [Hibernate] Lazy Collections
>=20
>=20
> > I had a *really* close look into the possibility
> > that Hibernate issues the unclosed session WARNing
> > when the session has in fact been closed and I've
> > concluded that it doesn't. I am quite certain that
> > the problem is that the user is not closing the
> > sessions. (In a couple of previous complaints about
> > this, that turned out to be the case.)
>=20
> Ok it might be my fault (and probably is). Do you see any strange in
> this:
>=20
> Background:
>=20
> - I have extended Maveric Dispatcher so that it loads=20
> Hibernate Session Factory from JNDI and places it in servlet=20
> context. Is that proper thing to do?
> - I have abstract controller that every of my maverick=20
> commands extends.
> - Abstract controller has 2 methods. getSession() that loads=20
> Session factory from Servlet context and then opens a new=20
> session (if user has already called this.getSession, then it=20
> returns previously opened
> session) and places it in class level variable and then=20
> returns it to user.
> - User then uses session.
> - User does not close session.
> - Session is closed in Abstract controller's discard() method=20
> that maverick calls automatically after it has served the=20
> client (e.g. gui is generated).
>=20
> The proces goes like this:
>=20
> 1. User makes request eg. grid.m that is a maveric command.
> 2. Maverick initializes NEW controller (the controller=20
> extends abstract
> controller) 3. Then maverick calls execute method. 4. execute=20
> method calls this.getSession.find("whatever") <- lazy=20
> collection 5. execute method returns a string (that is the=20
> view to be rended) 6. Maverick generates a view (view uses=20
> lazy collection) 7. Maverick calls discard (that closes a session)
>=20
> The generated HTML (in this case) contains many img tags like this
>=20
> <img src=3D"image.m?id=3Dnumber" />
>=20
> So every needed image gets loaded throught Maverick from=20
> database. image.m command opens session as above and after=20
> sending raw data with proper content-type session get's=20
> closed in execute method (Maveric calls discard, but it=20
> doesn't do anything cause session is already closed by=20
> execute command).
>=20
> The problem is that I have no idea why Hibernate's=20
> SessionImpl finalize method tries to close connections that I=20
> have already closed (I can output proper log messages when=20
> discard is called). What I have found is that if I don't=20
> close connections in execute method (prior view), then I=20
> sometimes leaves connections open. At least on load testing.=20
> If I don't use lazy collections I do not have this problem.
>=20
> > As to the use of finally, cleanup code that *must*
> > be executed is *exactly* the role of the finally
> > block, as per any Java textbook. And it is
> > completely predictable. Method exit cannot occur
> > without execution of the finally block. Are you
> > sure the redbook wasn't talking about finalize(),
> > which *is* unreliable?
>=20
> It's quite long time when I read that, and I could have read=20
> it wrong (I checked IBM docs and they all used finally)...=20
> and if I think about it, I agree with you. The errors I get=20
> about unclosed connections, I get them from SessionImpl=20
> finalize(). But problem is not there I think.
>=20
> Is it proper to place SessionFactory in servlet context, or=20
> should I always retrieve it from JNDI? I think that JNDI=20
> lookup causes some overhead, so I have put the Session=20
> factory in servlet context.
>=20
> When I should use Session.disconnect / reconnect instead open=20
> and close?
>=20
> Should I set session to null and should I also check if=20
> session.close returns an open connection? Do I need to close=20
> the connection then manually? Do i need to set connection =3D null?
>=20
> Kind Regards
> Aapo <b/>ungle Laakkonen
>=20
>=20
>=20
> -------------------------------------------------------
> This SF.net email is sponsored by: Microsoft Visual Studio.NET=20
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