I don't think that gets you around the lazy initialization problem
though, does it? If the session closes when the servlet returns, then it's
no longer available in subsequent interactions to load lazy collections.
Likewise, globally rolling back the transaction isn't necessarily
the right approach either (yet another gripe I have about how hibernate and
the web fight one another).
This is a slightly contrived example, but for purposes of
explanation it should work:
Lets say I need to log every user interaction to the DB (not that
weird actually, I've had to do this on some security conscious apps).
So whenever A user presses "save" on a web form I have to:
Log an "interaction begun" datum with the IP address, session ID,
etc.
Do the transaction.
Log an "interaction complete" datum with the UP address, session ID,
etc.
If I roll back globally, I lose not only the user's personal update
(which I want to roll back), but also the interaction records, which I
*don't* want to roll back.
It's gotten so aggravating I'm seriously considering using two
parallel session. One for "system" data that I have control of and one for
"user" updates that I might have to roll back. That way I can always flush
my system session and selectively flush the user session. Of course that
means twice the number of DB connections, dogs and cats living together,
etc, etc, etc.
It's frustrating, as you can doubtless discern from my aggravated
tone :(.
--- Pat
> -----Original Message-----
> From: Paul Cantrell [mailto:[EMAIL PROTECTED]
> Sent: Tuesday, August 30, 2005 3:23 PM
> To: Tapestry users
> Subject: Re: Transaction handling. Where?
>
> If you open & close your ThreadLocal session from a *servlet filter*
> instead of trying to finagle it into the tapestry lifecycle,
> everything is peachy -- at least in my limited experience.
>
> For rollbacks, implement a preventCommit() method your code can call
> on error. In the filter, you either commit or roll back depending on
> whether preventCommit() was called.
>
> Cheers,
>
> Paul
>
> On Aug 30, 2005, at 4:22 PM, Patrick Casey wrote:
>
> >
> > Yah, I'm familiar with a large variety of ways to initialize
> > collections. The problem with pre-initializing everything though is
> > that
> > most of the time, you *don't* need the whole object graph. So if I
> > have to
> > fill out every object graph every time I load a root object on the off
> > chance that somewhere, someday, someone might reference a child
> > object, I
> > end up wasting a lot of memory and database labour.
> >
> > As for long sessions being a bad idea; they *definitely* have
> > their
> > risks, especially if you aren't careful about evicting things when
> > they
> > aren't needed anymore. For web applications though, they really
> > seem like
> > the only practical approach in my experience. The threadlocal
> > pattern can't
> > solve the initialization problem, and the session-per-transaction
> > pattern
> > has performance problems *and* the lazy initialization problem.
> >
> > I really think the whole "we refuse to automatically reconnect to
> > lazy-load a connection and instead insist on throwing and
> > exception" is
> > database-purist-arrogance on the part of the Hibernate team. Most
> > of their
> > library is great, but this behavior is just *not* web friendly, and
> > their
> > smug assurance that it's "not a big deal to workaround" turns out
> > not to be
> > true in practice.
> >
> > --- Pat
> >
> >
> >> -----Original Message-----
> >> From: Tomáš Drenčák [mailto:[EMAIL PROTECTED]
> >> Sent: Tuesday, August 30, 2005 2:16 PM
> >> To: Tapestry users
> >> Subject: Re: Transaction handling. Where?
> >>
> >> You can initialize collections with Hibernate.initialize(collection),
> >> or in query with left join fetch and than use detached objects in
> >> further requests. And btw I've read that long open sessions aren't
> >> good idea at all...
> >>
> >> 2005/8/30, Patrick Casey <[EMAIL PROTECTED]>:
> >>
> >>>
> >>> As I understand it though, with this approach the session
> >>> has a
> >>> lifespan that doesn't span multiple requests (in fact, its
> >>> granularity
> >>>
> >> is <
> >>
> >>> 1 request). This raises problems in practice with use cases like:
> >>>
> >>> User has a set of roles (lazy collection)
> >>>
> >>> I bring up the User page. It loads from Session #1 which
> >>> is then
> >>> closed.
> >>> I click on the "show roles" button. We go back to Tapestry
> >>> which
> >>> merrily does a user.getRoles().iterator() and promptly blows up
> >>> with a
> >>>
> >> lazy
> >>
> >>> initialization exception because Session #1 (the one which
> >>> produced the
> >>> user) no longer exists.
> >>>
> >>> That and creating a fresh session for each database
> >>> interaction,
> >>> while not quite as bad a plan as creating a new JDBC connection
> >>> for each
> >>> query, is still not a great performance idea :(.
> >>>
> >>> --- Pat
> >>>
> >>>
> >>>> -----Original Message-----
> >>>> From: Tomáš Drenčák [mailto:[EMAIL PROTECTED]
> >>>> Sent: Tuesday, August 30, 2005 1:58 PM
> >>>> To: Tapestry users
> >>>> Subject: Re: Transaction handling. Where?
> >>>>
> >>>> I use classes described in
> >>>>
> >>>>
> >> http://www.theserverside.com/articles/content/HivemindBuzz/
> >> article.html.
> >>
> >>>> This is perfect approach for DAO pattern. Just declare DAO
> >>>> object as
> >>>> service with implementation and property of type
> >>>> org.hibernate.Session
> >>>> and setter setSession(Session). Session is then created uppon your
> >>>> request to service and always initialized and closed through
> >>>> ApplicationServlet which cleanups hivemind. There's also
> >>>> transaction
> >>>> interceptor...
> >>>>
> >>>> 2005/8/30, Chris Chiappone <[EMAIL PROTECTED]>:
> >>>>
> >>>>> Thanks, if I were to use this helperclass would I still go about
> >>>>> getting the session before a save or update and closing the
> >>>>> session
> >>>>> after complete, as i was before?
> >>>>>
> >>>>> Also have you thought about using something like HiveTrans to do
> >>>>>
> >> this
> >>
> >>>>> for you? I have been thinking about moving to tap 4 and using
> >>>>> hivemind with hivetrans to deal with the hibernate session
> >>>>>
> >> management.
> >>
> >>>>> Any thoughts??
> >>>>>
> >>>>> On 8/30/05, Patrick Casey <[EMAIL PROTECTED]> wrote:
> >>>>>
> >>>>>>
> >>>>>> To be honest, I *haven't* completely gotten around this
> >>>>>>
> >>>> problem.
> >>>>
> >>>>>> I've *sort of* gotten around it by going to a long-session
> >>>>>> pattern
> >>>>>>
> >> so
> >>
> >>>> that
> >>>>
> >>>>>> the Hibernate session virtually never flushes. If you want though
> >>>>>>
> >> I'll
> >>
> >>>>>> attach my HibHelper class so you can get a feel for what I did.
> >>>>>>
> >>>>>> Honestly though, it's not a magic bullet and I'm still
> >>>>>>
> >>>> struggling to
> >>>>
> >>>>>> find one. Still, if it gets you partway there, you're welcome to
> >>>>>>
> >> use
> >>
> >>>> it,
> >>>>
> >>>>>> modify it, whatever.
> >>>>>>
> >>>>>> To use it effectively you'll need a combination of the
> >>>>>>
> >>>> HibHelper
> >>>>
> >>>>>> class (above) and the subclassed engine I provided earlier which
> >>>>>>
> >>>> stores and
> >>>>
> >>>>>> retrieves the Hibernate session from the user session.
> >>>>>>
> >>>>>> --- Pat
> >>>>>>
> >>>>>>
> >>>>>>> -----Original Message-----
> >>>>>>> From: Chris Chiappone [mailto:[EMAIL PROTECTED]
> >>>>>>> Sent: Tuesday, August 30, 2005 1:40 PM
> >>>>>>> To: Tapestry users
> >>>>>>> Subject: Re: Transaction handling. Where?
> >>>>>>>
> >>>>>>> I was search back some threads and noticed your HibHelper class.
> >>>>>>>
> >> Is
> >>
> >>>>>>> that basically the way you've gotten around this problem,
> >>>>>>>
> >> HibHelper
> >>
> >>>>>>> and the Servlet class you wrote?
> >>>>>>>
> >>>>>>> On 8/30/05, Patrick Casey <[EMAIL PROTECTED]> wrote:
> >>>>>>>
> >>>>>>>>
> >>>>>>>> Not necessarily, but it depends on how you want your
> >>>>>>>>
> >> system
> >>
> >>>> to
> >>>>
> >>>>>>>> manage transactions. One area where Hibernate and Tapestry
> >>>>>>>>
> >> don't
> >>
> >>>> "play
> >>>>
> >>>>>>> nice"
> >>>>>>>
> >>>>>>>> is with data binding.
> >>>>>>>>
> >>>>>>>> Let's say I have a "user" form that is bound to a
> >>>>>>>>
> >>>> persistent User
> >>>>
> >>>>>>>> object.
> >>>>>>>>
> >>>>>>>> Form gets rendered and goes out.
> >>>>>>>> User does some stuff and presses save.
> >>>>>>>> Form comes in, rewinds, and delta is pushed through
> >>>>>>>>
> >> into
> >>
> >>>> "user"
> >>>>
> >>>>>>>> object.
> >>>>>>>> *** At this point the user object is flagged by
> >>>>>>>>
> >> Hibernate
> >>
> >>>> as
> >>>>
> >>>>>>> dirty.
> >>>>>>>
> >>>>>>>> The next time the session flushes, it'll write through to the
> >>>>>>>>
> >>>> database,
> >>>>
> >>>>>>>> whether or not you call saveOrUpdate()!
> >>>>>>>>
> >>>>>>>> This is problematic if, for example, you want to cancel
> >>>>>>>>
> >> the
> >>
> >>>>>>> update
> >>>>>>>
> >>>>>>>> because of failed validations :(.
> >>>>>>>>
> >>>>>>>> One approach that can help is to evict everything from
> >>>>>>>>
> >> the
> >>
> >>>>>>> session
> >>>>>>>
> >>>>>>>> on load so that it doesn't auto-flush. If you do this though,
> >>>>>>>>
> >> you
> >>
> >>>> will
> >>>>
> >>>>>>>> likely have lazy initialization problems later on.
> >>>>>>>>
> >>>>>>>> Another approach is to not directly bind your page to
> >>>>>>>>
> >> your
> >>
> >>>>>>>> persistent object, but that adds a whole other level of work
> >>>>>>>>
> >> to
> >>
> >>>> the page
> >>>>
> >>>>>>>> class.
> >>>>>>>>
> >>>>>>>> All in all, I have not been happy with the interaction
> >>>>>>>>
> >>>> between
> >>>>
> >>>>>>>> Hibernate and Tapestry. With a classic servlet engine it's not
> >>>>>>>>
> >> a
> >>
> >>>> biggy
> >>>>
> >>>>>>>> because you can just not push invalid updates into the
> >>>>>>>>
> >> persistent
> >>
> >>>>>>> object.
> >>>>>>>
> >>>>>>>> With Tapestry though, the (normally helpful) behavior of
> >>>>>>>>
> >> directly
> >>
> >>>>>>> binding
> >>>>>>>
> >>>>>>>> user updates into the underlying persistent object doesn't
> >>>>>>>>
> >> allow
> >>
> >>>> the
> >>>>
> >>>>>>>> programmer any control over when updates go through.
> >>>>>>>>
> >>>>>>>> Basically it all comes down to Hibernate insisting that
> >>>>>>>>
> >> it
> >>
> >>>> knows
> >>>>
> >>>>>>>> better than the programmer when things ought to be saved to
> >>>>>>>>
> >> the DB
> >>
> >>>> :(.
> >>>>
> >>>>>>>>
> >>>>>>>> --- Pat
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>> -----Original Message-----
> >>>>>>>>> From: Chris Chiappone [mailto:[EMAIL PROTECTED]
> >>>>>>>>> Sent: Tuesday, August 30, 2005 1:07 PM
> >>>>>>>>> To: Tapestry users
> >>>>>>>>> Subject: Re: Transaction handling. Where?
> >>>>>>>>>
> >>>>>>>>> In my DOA i do the following...
> >>>>>>>>>
> >>>>>>>>> public void makePersistentUser(Users user)
> >>>>>>>>> throws InfrastructureException {
> >>>>>>>>>
> >>>>>>>>> try {
> >>>>>>>>> HibernateUtil.beginTransaction();
> >>>>>>>>>
> >>>>>>>>>
> >>>> HibernateUtil.getSession().saveOrUpdate(user);
> >>>>
> >>>>>>>>> HibernateUtil.commitTransaction();
> >>>>>>>>> HibernateUtil.closeSession();
> >>>>>>>>> } catch (HibernateException ex) {
> >>>>>>>>> throw new
> >>>>>>>>>
> >> InfrastructureException(ex);
> >>
> >>>>>>>>> }
> >>>>>>>>> }
> >>>>>>>>>
> >>>>>>>>> Is this the wrong way to do it??
> >>>>>>>>>
> >>>>>>>>> On 8/30/05, Patrick Casey <[EMAIL PROTECTED]> wrote:
> >>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>>> Have you tried subclassing BaseEngine and doing
> >>>>>>>>>>
> >> your
> >>
> >>>>>>> transaction
> >>>>>>>
> >>>>>>>>>> management in cleanupAfterRequest() and setupForRequest()
> >>>>>>>>>>
> >> e.g.
> >>
> >>>>>>>>>>
> >>>>>>>>>> public class CorinnaEngine extends BaseEngine {
> >>>>>>>>>> private static final long serialVersionUID =
> >>>>>>>>>>
> >>>>>>>>> 3257284742721648952L;
> >>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>>> protected void cleanupAfterRequest(IRequestCycle
> >>>>>>>>>>
> >> cycle)
> >>
> >>>> {
> >>>>
> >>>>>>>>>> HibHelper.cleanupSession();
> >>>>>>>>>>
> >>>>>>>>>> super.cleanupAfterRequest(cycle);
> >>>>>>>>>> }
> >>>>>>>>>>
> >>>>>>>>>> protected void setupForRequest(RequestContext
> >>>>>>>>>>
> >> context)
> >>
> >>>> {
> >>>>
> >>>>>>>>>> HttpSession hs =
> >>>>>>>>>>
> >> MyServlet.getCurrentSession();
> >>
> >>>>>>>>>> HibHelper.attachSession(hs);
> >>>>>>>>>> HibHelper.getSession();
> >>>>>>>>>> super.setupForRequest(context);
> >>>>>>>>>> }
> >>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>>> }
> >>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>>>> -----Original Message-----
> >>>>>>>>>>> From: Koka [mailto:[EMAIL PROTECTED]
> >>>>>>>>>>> Sent: Tuesday, August 30, 2005 12:00 PM
> >>>>>>>>>>> To: [email protected]
> >>>>>>>>>>> Subject: Transaction handling. Where?
> >>>>>>>>>>>
> >>>>>>>>>>> Well, I have pages that allow to edit some database
> >>>>>>>>>>>
> >> data, so
> >>
> >>>> I
> >>>>
> >>>>>>> have
> >>>>>>>
> >>>>>>>>> easy
> >>>>>>>>>
> >>>>>>>>>>> solution to start transaction at
> >>>>>>>>>>> public void pageBeginRender(PageEvent event)
> >>>>>>>>>>> {
> >>>>>>>>>>> if (event.getRequestCycle().isRewinding())
> >>>>>>>>>>>
> >>>>>>>>>>> // start transaction here
> >>>>>>>>>>> }
> >>>>>>>>>>>
> >>>>>>>>>>> and at
> >>>>>>>>>>> public void pageEndRender(PageEvent event)
> >>>>>>>>>>> {
> >>>>>>>>>>> if (event.getRequestCycle().isRewinding())
> >>>>>>>>>>> {
> >>>>>>>>>>> // Commit or rollback if errors found
> >>>>>>>>>>>
> >>>>>>>>>>> }
> >>>>>>>>>>> }
> >>>>>>>>>>>
> >>>>>>>>>>> Hmm, it WORKS fine but, hmmm, page render and
> >>>>>>>>>>>
> >>>> transactions...,
> >>>>
> >>>>>>> agrrr
> >>>>>>>
> >>>>>>>>> sure
> >>>>>>>>>
> >>>>>>>>>>> there's some other place to handle things.So the
> >>>>>>>>>>>
> >> question is
> >>
> >>>> what
> >>>>
> >>>>>>> is
> >>>>>>>
> >>>>>>>>> the
> >>>>>>>>>
> >>>>>>>>>>> right place to start/end transaction in Tap4
> >>>>>>>>>>> TYA
> >>>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>>> ----------------------------------------------------------
> >>>>>>>>>>
> >> ----
> >>
> >>>> ------
> >>>>
> >>>>>>> -
> >>>>>>>
> >>>>>>>>>> To unsubscribe, e-mail: tapestry-user-
> >>>>>>>>>>
> >>>> [EMAIL PROTECTED]
> >>>>
> >>>>>>>>>> For additional commands, e-mail: tapestry-user-
> >>>>>>>>>>
> >>>>>>> [EMAIL PROTECTED]
> >>>>>>>
> >>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>> --
> >>>>>>>>> ~chris
> >>>>>>>>>
> >>>>>>>>> ------------------------------------------------------------
> >>>>>>>>>
> >> ----
> >>
> >>>> -----
> >>>>
> >>>>>>>>> To unsubscribe, e-mail: tapestry-user-
> >>>>>>>>>
> >>>> [EMAIL PROTECTED]
> >>>>
> >>>>>>>>> For additional commands, e-mail: tapestry-user-
> >>>>>>>>>
> >>>> [EMAIL PROTECTED]
> >>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>> --------------------------------------------------------------
> >>>>>>>>
> >> ----
> >>
> >>>> ---
> >>>>
> >>>>>>>> To unsubscribe, e-mail: tapestry-user-
> >>>>>>>>
> >>>> [EMAIL PROTECTED]
> >>>>
> >>>>>>>> For additional commands, e-mail: tapestry-user-
> >>>>>>>>
> >>>> [EMAIL PROTECTED]
> >>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>> --
> >>>>>>> ~chris
> >>>>>>>
> >>>>>>> ----------------------------------------------------------------
> >>>>>>>
> >> ----
> >>
> >>>> -
> >>>>
> >>>>>>> To unsubscribe, e-mail: tapestry-user-
> >>>>>>>
> >> [EMAIL PROTECTED]
> >>
> >>>>>>> For additional commands, e-mail: tapestry-user-
> >>>>>>>
> >>>> [EMAIL PROTECTED]
> >>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>> -----------------------------------------------------------------
> >>>>>> -
> >>>>>>
> >> ---
> >>
> >>>>>> To unsubscribe, e-mail: tapestry-user-
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> >> [EMAIL PROTECTED]
> >>
> >>>>>> For additional commands, e-mail: tapestry-user-
> >>>>>>
> >> [EMAIL PROTECTED]
> >>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>
> >>>>>
> >>>>> --
> >>>>> ~chris
> >>>>>
> >>>>> ------------------------------------------------------------------
> >>>>> --
> >>>>>
> >> -
> >>
> >>>>> To unsubscribe, e-mail: tapestry-user-
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> >>>>> For additional commands, e-mail: tapestry-user-
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> >> [EMAIL PROTECTED]
> >>
> >>>>>
> >>>>>
> >>>>>
> >>>>
> >>>> -------------------------------------------------------------------
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> >>>
> >>>
> >>>
> >>>
> >>> --------------------------------------------------------------------
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> >
> >
> >
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