And, btw, Orchestra is still useful then, but there is no need to attach it to the PersistenceContext then. It just acts as a "simple" conversation scope provider without any magic associated with the database layer. => easier spring configuration too.
Ciao, Mario -----Ursprüngliche Nachricht----- Von: Mario Ivankovits [mailto:ma...@ops.co.at] Gesendet: Freitag, 02. Juli 2010 10:27 An: 'MyFaces Discussion' Betreff: Re: Long transactions Hi! I know, I might sound like a broken record already ... But also consider using a JPA-like persistence provider like Ebean [1]. If you are going to deatach your objects, you can avoid the persistence context at all. Ebean just maintains a persistence context per transaction. So, if you are having "processes" which reads the same row from the database multiple times you'll get the same instance from the cache, but reads outside of a transaction result in immediately detached object. For sure, without the persistence context you have to call "ebean.save(instance)" on your entities instead of relying on a session.commit(), but this is a very low price to pay compared to all the hassle you have with a long running persistence context. Lazy loading is still possible with Ebean anyway! And not only this, it also "learns" (if configured) from your application which relations you use and which properties and next time will autotune the select to just fetch those properties and relation. No need to define a 1:n relation eager or lazy, it just learns that (optional for sure!). I can say, I am quite happy with this library! I even replaced Hibernate by it. Probably you have to put some effort into the transition, but for me it made things alot easier again. Ciao, Mario [1] www.avaje.org -----Ursprüngliche Nachricht----- Von: Mark Struberg [mailto:strub...@yahoo.de] Gesendet: Freitag, 02. Juli 2010 10:12 An: MyFaces Discussion Betreff: Re: Long transactions > Mike you left out the obvious one, simply use a conversation framework. Definitely true, but not always applicable. I would e.g. not recommend using long running transactions for public pages. This will increase the session footprint big times and you'll get more easily vulnerable for DOS attacks this way. Otoh, for intranet apps or pages with a limited reach, frameworks like Orchestra will really make your life way easier. FYI: we are currently working on getting Orchestra style conversations ported over to our MyFaces Extensions for CDI (EXTCDI / CODI). LieGrue, strub ----- Original Message ---- > From: Werner Punz <werner.p...@gmail.com> > To: users@myfaces.apache.org > Sent: Fri, July 2, 2010 9:39:05 AM > Subject: Re: Long transactions > > Mike you left out the obvious one, simply use a conversation framework. The > problem is not transactions but it is that the entity manger is dropped > along the way hence silently detaching all objects and running you into > detached error hell. (You still can either setup your jpa provider so that > lazy loading can happen outside of transaction barriers or prefetch > everything via fetch join) I personally found as soon as you go to a > conversation framework things become way easier (although not entirely > easy) Also what was the problem with holder objects. I personally am > thinking of moving that way especially since JPA allows to map it > transparently via queries like following select new FakeHolder( > target="_blank" href="http://entity.id";>entity.id, entity....) from > EntityClass entity). The downside is that you need more logic for pushing > the data back into the entity objects before writing. But the fake holder > pattern is exactly what iBatis enforces (although it has the write back > logic pushed into the configuration) and it works out well in a web centric > szenario. WErner Am 01.07.10 23:54, schrieb Mike > Kienenberger: > I am, sort of. > > You really can't leave the > transaction open beyond the request > response as it may never > complete. > > Some of the ways you can deal with it > are: > > 1) work with fake holder entities that get changed back > into real > entities at the final commit. Very ugly -- tried this > one at first, > but I don't use it anymore. > > 2) Work with > detached objects. Reattach them back right before the > final > commit. This is what I currently do. I basically invented > a > Unit-Of-Work framework that runs over the top of JPA. The > unit of > work has a separate persistence manager that loads an object, > then > immediately detaches it. Our framework requires each object > to call > save() to commit changes. When in the UoW, all save does > is add the > object to a change-tracker (inserts, deletes, updates). > Then when > the UoW is committed, the objects are persisted or > merged, then > committed all in one method call. > > But in > all honesty, this approach also has caused us a lot of hassles. > > We are most likely going to dump JPA and replace it with Apache > > Cayenne, which uses a real unit of work concept. > > Another option > for you might be to use an implementation-specific unit > of work provided > by your JPA implementation. However, I don't know > if you might > have other issues. I used Cayenne before I used JPA, > and I know > Cayenne does exactly what I need. > > A third option you could > consider if you want to risk leaving the > transaction > open. > > a) Catch the window onunload event, and mixed with ajax, > send an ajax > request when the user improperly attempts to leave the page > (closes > the window or browser, enters a url directly, back buttons, some > other > non-transaction-friendly link clicked). > > I got this > far with that approach, but didn't pursue it. Note that > this can > only detect when the user is about to leave the page. It > cannot do > anything at that point -- you'd have to do something about > it in some > other way. > > > window.onbeforeunload = confirmExit; > > function confirmExit() > > { > > if (needToConfirm) > > return "You have attempted to leave this page. If you > have > made any changes to the fields without clicking the Save button, > your > changes will be lost. Are you sure you want to exit this > page?"; > > } > > > b) Some other kind of client-side state tracking so > that you know when > the user has navigated away from the current > multi-request task. > We're sticking a taskGroupIdentifier field on every > form (ajax > included) so we know when the user does something to switch > to a new > task than the one we're currently working with. Doesn't > help if you > have some transaction left open and the user never hits the > web server > again, but a timeout could deal with > that. > > > In short, I think it's a difficult problem, and I > think JPA is > incapable of dealing with it correctly. The other > shortfall we have > is that JPA cannot rollback a transaction. You > have no way of > knowing what state your application is in once you roll > back the > transaction. Again Cayenne automatically puts everything > exactly > where it was at the start of your unit of work if you do a > rollback. > > On Thu, Jul 1, 2010 at 9:53 AM, Bruno Aranda< > ymailto="mailto:brunoara...@gmail.com"; > href="mailto:brunoara...@gmail.com";>brunoara...@gmail.com> > wrote: >> Hi, >> >> Is anyone here using long JPA > transactions in their applications >> (transactions that span more than > one request) but not using Orchestra?. How >> are you doing > it? >> >> Cheers, >> >> > Bruno >> >
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