Yes, that's what I am doing. I will then store the objects in the session and later add support for storing them in a temp table if needded.
In case the objects are to be saved in the database, what would be the best approach? I the same table as the actual object (needs one more field to indicate if it is an original clone or an actual object)? Or in a separate table (needs to double the number of tables)? Pierre-Yves Igor Vaynberg a écrit : > if you keep a clone of the object before the change in your session > (which sounds like you do) then there wont be any issues. you have all 3 > states needed to merge correctly. > > -Igor > > > On 9/13/06, *Pierre-Yves Saumont* <[EMAIL PROTECTED] <mailto:[EMAIL > PROTECTED]>> > wrote: > > I eventually implemented something very close to what you describe. > Basically it is a sort of optimistic locking with field merging so that > update fails only for those fields that are found different at update > time than at read time. In such case, fields that can be updated are > and > those that can't are left unchanged. The form is redisplayed so the user > can see the two versions. If he saves a second time, all fields are > updated. > > However, to achieve this, I need to implement pessimistic locking for a > short time, between the time the form is redisplayed and the time the > user saves again or cancel. (Pessimistic locking is also implemented > between a delete request and its confirmation or cancellation.) > > The problem is that the user can make a third choice and go to have a > coffe break. So, the lock that the user (in fact the session) has > acquire will expire after some configurable time. It works by writing > the session id, the lock time and the maximum delay into the database. > That way, if another user comes, he can see if there is a lock and if > this lock is active, and act accordingly. This is supposed to solve the > problem of the user not releasing a lock. > > There is still a problem: in the optimistic/merge scenario, I must have > a copy of the field values at read time to compare with the modified > fields and the actual fields. For this, I keep a reference to the > hibernate object. The modified fields are in a value object. > > Not holding a reference to the original object would not be relevant if > I would still hold a reference to the value object. It makes little > sense to throw one away and keep the other. But there is no hibernate > related problem, since the object is never used to persist or merge the > data. > > Now, it could be possible to keep only the ids of the objects. For > this, > I would have to store the two objects in the database. But I do not > think this would be rewarding. I would need to create special tables for > this, write the two objects, read them, and eventually delete them. I > prefer to have small objects (in case of big entities, just break them > in smaller parts) and store them for the duration of the pseudo > transaction. At worst, they will be thrown away when the session expires > and the locks in the database will have themsevles expired much longer > before. > > The real question is "which potential problem is hidden in this scenario > and will suddenly jump out when the app will be in production ? :-(" > > Pierre-Yves > > Johan Compagner a écrit : > > you really shouldn't lock objects over request.. > > Because you don't controll anything. He can close the browser or > go away > > In a swing app where you have a connection to you can at least do > > something about it > > (and show that to the user that he looses it and take it again on a > > focus of a field) > > > > But long transactions or locks over request is in my eyes bad > praktisch > > that shouldn't be done in a webapp. > > > > Maybe with full use of ajax you can get to the behaviour a bit that a > > fat client would have.. > > > > But i prefer other way. Just let it change it and if it did > change (does > > that really happen a lot? i can't believe that) > > then report that first back to the user that a save couldn't happen > > because another person did change it already > > and do show those changes (try to merge it) > > > > johan > > > > > > On 9/12/06, *Pierre-Yves Saumont* <[EMAIL PROTECTED] > <mailto:[EMAIL PROTECTED]> <mailto:[EMAIL PROTECTED] <mailto:[EMAIL > PROTECTED]>>> > > wrote: > > > > Hi, > > > > Is there a Wicket (ie really smart) way to detext when the > user switch > > to another page? > > > > The use case is to release locks that a user might have put > on database > > records with pessimistic locking when the user switch to > another page. > > > > Pierre-Yves > > > > > > > ------------------------------------------------------------------------- > > > > Using Tomcat but need to do more? Need to support web services, > > security? > > Get stuff done quickly with pre-integrated technology to make > your > > job easier > > Download IBM WebSphere Application Server v.1.0.1 based on Apache > > Geronimo > > > http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 > <http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642> > > > <http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 > > <http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642>> > > _______________________________________________ > > Wicket-user mailing list > > Wicket-user@lists.sourceforge.net > <mailto:Wicket-user@lists.sourceforge.net> > > <mailto: Wicket-user@lists.sourceforge.net > <mailto:Wicket-user@lists.sourceforge.net>> > > https://lists.sourceforge.net/lists/listinfo/wicket-user > <https://lists.sourceforge.net/lists/listinfo/wicket-user> > > <https://lists.sourceforge.net/lists/listinfo/wicket-user> > > > > > > > ------------------------------------------------------------------------- > > Using Tomcat but need to do more? Need to support web services, > security? > Get stuff done quickly with pre-integrated technology to make your > job easier > Download IBM WebSphere Application Server v.1.0.1 based on Apache > Geronimo > http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 > <http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642> > _______________________________________________ > Wicket-user mailing list > Wicket-user@lists.sourceforge.net > <mailto:Wicket-user@lists.sourceforge.net> > https://lists.sourceforge.net/lists/listinfo/wicket-user > <https://lists.sourceforge.net/lists/listinfo/wicket-user> > > ------------------------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 _______________________________________________ Wicket-user mailing list Wicket-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/wicket-user
