NHibernate with Autofac within ASP.NET (MVC): ITransaction - asp.net-mvc

Question

What is the best approach to managing NHibernate transaction using Autofac within web application?
My approach to session is
builder.Register(c => c.Resolve<ISessionFactory>().OpenSession())
.ContainerScoped();
For ITransaction, I have found an example on Google Code, but it relies on HttpContext.Current.Error when deciding whether to rollback.
Is there a better solution? And what scope NHibernate transaction should have?

Answer 1

I posted this a while ago:
http://groups.google.com/group/autofac/browse_thread/thread/f10badba5fe0d546/e64f2e757df94e61?lnk=gst&q=transaction#e64f2e757df94e61
Modified, so that the interceptor has logging capability and [Transaction] attribute can also be used on a class.
[global::System.AttributeUsage(AttributeTargets.Method | AttributeTargets.Class)]
public class TransactionAttribute : Attribute
{
}
public class ServicesInterceptor : Castle.Core.Interceptor.IInterceptor
{
private readonly ISession db;
private ITransaction transaction = null;
public ServicesInterceptor(ISession db)
{
this.db = db;
}
public void Intercept(IInvocation invocation)
{
ILog log = LogManager.GetLogger(string.Format("{0}.{1}", invocation.Method.DeclaringType.FullName, invocation.Method.Name));
bool isTransactional = IsTransactional(invocation.Method);
bool iAmTheFirst = false;
if (transaction == null && isTransactional)
{
transaction = db.BeginTransaction();
iAmTheFirst = true;
}
try
{
invocation.Proceed();
if (iAmTheFirst)
{
iAmTheFirst = false;
transaction.Commit();
transaction = null;
}
}
catch (Exception ex)
{
if (iAmTheFirst)
{
iAmTheFirst = false;
transaction.Rollback();
db.Clear();
transaction = null;
}
log.Error(ex);
throw ex;
}
}
private bool IsTransactional(MethodInfo mi)
{
var atrClass = mi.DeclaringType.GetCustomAttributes(false);
foreach (var a in atrClass)
if (a is TransactionAttribute)
return true;
var atrMethod = mi.GetCustomAttributes(false);
foreach (var a in atrMethod)
if (a is TransactionAttribute)
return true;
return false;
}
}

Answer 2

When I use autofac I use the same container scoped method but instead of passing the same session to my Repository/DAO objects I pass an UnitOfWork that is container scoped. The Unit of work has this in the constructor.
private readonly ISession _session;
private ITransaction _transaction;
public UnitOfWork(ISession session)
{
_session = session;
_transaction = session.BeginTransaction();
}
And the dispose is:
public void Dispose()
{
try
{
if (_transaction != null &&
!_transaction.WasCommitted &&
!_transaction.WasRolledBack)
_transaction.Commit();
_transaction = null;
}
catch (Exception)
{
Rollback();
throw;
}
}
I am (ab)using the deterministic disposal stuff in autofac in order to manage this, and well I sort of like it.
The other thing is that I am basically only targeting an ASPNet environment and made a conscious decision that a transaction is tied to a web request. So a transaction per web request pattern.
Because of that I can do this error handling code in an IHttpModule:
void context_Error(object sender, System.EventArgs e)
{
_containerProvider.RequestContainer.Resolve<IUnitOfWork>().Rollback();
}
I haven't taken a look at NHibernate.Burrow too closely but I'm sure there is something there that does most of this.

Answer 3

I usually manage the transaction myself..
public ActionResult Edit(Question q){
try {
using (var t = repo.BeginTransaction()){
repo.Save(q);
t.Commit();
return View();
}
catch (Exception e){
...
}
}