I think the failure on my part was misunderstanding the separation between session and transaction. You can keep a session open, but only invoke a transaction for the scope of an update. I missed this somehow in my reading of the documentation and examples.
On Jan 26, 11:09 am, Fabio Maulo <[email protected]> wrote: > Maintain a transaction open during thinking-time is not a good idea, take > care with it > > 2010/1/26 Dietrich <[email protected]> > > > > > > > Fabio, thank you for the links. I appreciate you taking some of your > > valuable time to consider my issues. I've read them and I think they > > would have been very useful in the initial design stage of my > > application, but at this juncture altering the application > > infrastructure to line up with the recommended structures there would > > be a massive undertaking which I hope is not necessary. I feel like I > > should explain more fully how I'm doing things in my application to > > add this this conversation because it doesn't seem like anyone else > > uses patterns similar to what we've ended up with. I apologize in > > advance for the length of this post. Hopefully people will find it > > interesting. > > > I've got three projects- .Core, .Data, and .UI > > > .Core is exactly what you would expect it to be- nothing but the > > domain model and business logic. I don't think I need to elaborate in > > detail on how this is set up. It has no dependencies. > > .UI is just the code required to present the user interface. No > > business logic exists here. I'm attempting to minimize the NHibernate > > specific code in here as well. It is dependant on .Core and .Data. > > > .Data's design is what is somewhat unique. > > It has 4 major areas of code. > > -It contains the hbm.xml mappings for the .core objects that have > > persistence. > > > -It contains a definition for two kinds of Sessions which can be > > thought to represent a unit of work- ReadSession and WriteSession. > > These inherit from DBSession which is just an IDisposable wrapper for > > the ISession. WriteSession is used by forms that can edit data, > > ReadSession is for read-only forms. WriteSession contains methods to > > Delete and Save. All sessions contain methods to evict and re-attach > > POCOs, and one question I have is if I'm using the appropriate > > NHibernate methods to do this. Whenever HibernateExceptions are > > experienced, the Session will rollback the transaction as recommended > > by the documentation. > > > -It contains a Generic Database<T> class which can be used to query > > any persisted table for single objects. Each query in here, for > > example, GetByID, takes a DBSession in addition to whatever other > > parameters are required. > > > -Finally it contains a collection of Query classes which perform more > > advanced or optimized queries for specific domain objects or maps of > > objects. These also take a DBSession and perform the query using the > > ISession that is wrapped in the DBSession. > > > So your standard editing form will open, declare a WriteSession, then > > either use the generic database class or a query class to grab the > > objects it's interested in. For the life of the form, the DBSession > > remains open, and the DBSession maintains an open transaction with > > ReadUncommited isolation level. > > The user edits the object data via the form, then either clicks a save > > button (which commits changes, then disposes the active transaction > > and starts a new transaction) or goes to close the form. > > When closing the form asks the DBSession if it is dirty. If it is, it > > asks the user if they want to commit or discard their changes. > > > So here are my /big/ questions. > > 1- Which NHibernate session methods should I be using to attach/ > > reattach POCO objects to a session? I'm using ISession.Update, because > > these objects could change between sessions. I see Lock- but the > > documentation of how this works in its various modes is somewhat > > confusing. I'm game for moving to a different transaction model, but > > I'll (obviously) need a better understanding of this functionality in > > order to successfully implement it > > > 2- Is this transaction model appropriate? I see a lot of advocacy for > > keeping transactions open only as long as there is data being queried > > or updated. One aspect of my transaction model that I do appreciate is > > that it allows me to be sloppy with pre-loading data, and when the > > user's action requires an object wrapped in a proxy, the transaction > > is always up and ready to handle the proxy without me needing to keep > > track of which objects would be proxies and which would be domain > > objects based on the initial query. I'm OK with changing this design, > > I just need to know that what I'm doing is something that is not > > supposed to be supported- or to be more specific, that NHibernate does > > not contain the functionality that would be required to support this > > transaction model without unintended consequences- such as the full > > map save I'm seeing now. > > > 3- I see a lot of discussion about the repository design for > > NHibernate applications, and I've attempted to emulate the best parts > > of this between the class specific queries and the generic Database<T> > > class. However, am I missing the best part of this by not fully > > integrating the transaction management in a strongly typed repository > > class? > > > Thank you for your time. > > > On Jan 26, 9:34 am, Fabio Maulo <[email protected]> wrote: > > > Have a look to the ChinoOk series on this bloghttp:// > > jfromaniello.blogspot.com/2009/08/introducing-nhiberate-and-wp... > > > > <http://jfromaniello.blogspot.com/2009/08/introducing-nhiberate-and-wp.. > > .>It > > > is based on CpBT (the series end here) > >http://fabiomaulo.blogspot.com/2009/01/aspect-conversation-per.html > > > > <http://fabiomaulo.blogspot.com/2009/01/aspect-conversation-per.html>If > > you > > > prefer something more easy to followhttp:// > > fabiomaulo.blogspot.com/2009/09/nhibernate-in-winform-coupled.... > > > > 2010/1/26 Dietrich <[email protected]> > > > > > Windows forms. > > > > > On Jan 25, 10:51 pm, Fabio Maulo <[email protected]> wrote: > > > > > Web or Win ? > > > > > > 2010/1/25 Dietrich <[email protected]> > > > > > > > I am attempting to generate a new usage pattern to avoid this > > problem > > > > > > where a session is not kept open for longer than a single procedure > > > > > > that requires data access. The save button works just fine, but now > > my > > > > > > dirty checking on form close has become a problem. > > > > > > On close, I create a new session, call .SaveOrUpdate with the > > primary > > > > > > object, and then check if it's dirty. It always is, even when the > > > > > > object has not changed from the database. I also tried .Lock(obj, > > > > > > ReadMode.Upgrade), and this always returns that it's not dirty, > > even > > > > > > when the object HAS changed from the database. > > > > > > > There are many methods that all seem designed to handle these kinds > > of > > > > > > circumstances. Which ones should I be using? > > > > > > > On Jan 24, 12:23 pm, Dietrich <[email protected]> wrote: > > > > > > > I've got a winforms production application that putting locks on > > > > three > > > > > > > tables in my SQL 2005 server almost all day long. I have many > > forms > > > > in > > > > > > > the system which use the same pattern, so what confuses me is > > that > > > > > > > only one specific form seems to be causing these locks. > > > > > > > > When the form is opened, it creates a session and loads the > > objects > > > > > > > that could be edited on that form. It keeps that session open for > > the > > > > > > > lifetime of the form and I use the session to perform a dirty > > check > > > > > > > when the form is closed to ask if the user wants to commit their > > > > > > > changes. > > > > > > > > The sessions are opened with a readuncommited isolation level. > > > > > > > > So question 1 - is this the right way to handle sessions? Should > > I > > > > use > > > > > > > one session to load the data for the form and another session to > > > > > > > commit the changes when they close a form? If so, how should I > > handle > > > > > > > dirty tracking? > > > > > > > > Question 2 - what specific kind of activity inside a session > > would > > > > > > > create table locks? Like I said, I use this same pattern on many > > > > > > > forms, but only one form seems to show this behavior. I'll be > > happy > > > > to > > > > > > > provide code, but this form hits a ton of code within my various > > > > > > > layers, and in the interest of brevity, I don't want to post a > > ton of > > > > > > > code that couldn't possibly have this impact. > > > > > > > > Thank you! > > > > > > > -- > > > > > > You received this message because you are subscribed to the Google > > > > Groups > > > > > > "nhusers" group. > > > > > > To post to this group, send email to [email protected]. > > > > > > To unsubscribe from this group, send email to > > > > > > [email protected]<nhusers%[email protected] > > > > > > > > > <nhusers%[email protected]<nhusers%252bunsubscr...@googlegroup > > s.com>> > > > > <nhusers%[email protected]<nhusers%252bunsubscr...@googlegroup > > > > s.com> > > <nhusers%252bunsubscr...@googlegroup s.com> > > > > > > > . > > > > > > For more options, visit this group at > > > > > >http://groups.google.com/group/nhusers?hl=en. > > > > > > -- > > > > > Fabio Maulo > > > > > -- > > > > You received this message because you are subscribed to the Google > > Groups > > > > "nhusers" group. > > > > To post to this group, send email to [email protected]. > > > > To unsubscribe from this group, send email to > > > > [email protected]<nhusers%[email protected] > > > > > > > <nhusers%[email protected]<nhusers%252bunsubscr...@googlegroup > > s.com>> > > > > . > > > > For more options, visit this group at > > > >http://groups.google.com/group/nhusers?hl=en. > > > > -- > > > Fabio Maulo > > > -- > > You received this message because you are subscribed to the Google Groups > > "nhusers" group. > > To post to this group, send email to [email protected]. > > To unsubscribe from this group, send email to > > [email protected]<nhusers%[email protected] > > > > > . > > For more options, visit this group at > >http://groups.google.com/group/nhusers?hl=en. > > -- > Fabio Maulo -- You received this message because you are subscribed to the Google Groups "nhusers" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/nhusers?hl=en.
