NHibernate will save, but won´t load an entity

Question

I´m receiving a very strange error with NHibernate 2.1.2.4000 GA and latest version of FluentNHibernate. I can save an entity but can´t load it back after a call to Flush() and Clear().

This is my entity:

public class Application
{
 public int Id { get; set; }
 public string Name { get; set; }
 public string KeyName { get; set; }
 public string Description { get; set; }
 public string Url { get; set; }

 public override bool Equals(object obj)
 {
  if (null != obj && obj is Application)
  {
   return ((Application)obj).Id == this.Id;
  }
  else
  {
   return base.Equals(obj);
  }
 }
}

My configuration Map:

public class ApplicationMap : ClassMap
{
 public ApplicationMap()
 {
  Table("[Application]");

  Not.LazyLoad();

  Id(x => x.Id, "ApplicationId")
   .GeneratedBy.Identity();
  Map(x => x.Name, "ApplicationName")
   .Nullable()
   .Length(50);
  Map(x => x.Description, "ApplicationDescription")
   .Nullable()
   .Length(200);
  Map(x => x.KeyName, "ApplicationKeyName")
   .Nullable()
   .Length(50);
  Map(x => x.Url, "ApplicationLink")
   .Nullable()
   .Length(50);
 }
}

How I create my ISession:

var _sessionFactory = Fluently.Configure()
 .Database(
  SQLiteConfiguration.Standard.InMemory()
  .ProxyFactoryFactory(typeof(ProxyFactoryFactory)))
 .Mappings(
  m => m.FluentMappings.AddFromAssemblyOf())
 .ExposeConfiguration(cfg => Config = cfg)
 .BuildSessionFactory(); 

var _session = _sessionFactory.OpenSession();

And this is the code that won´t work:

Application myApp = new Application()
{
 Id = 1,
 Description = "MyApp",
 KeyName = "MyApp",
 Name = "My App",
 Url = "http://www.myapp.com"
};

_session.Save(myApp);
var idMyApp = myApp.Id;
_session.Flush();
_session.Clear();
_session = NHibernateHelper.CreateSession();
var a = _session.Load(idMyApp);

The Exception I get at the moment I try to Load the object back from database is:

Test method HNI.Portal.Test.MappingTests.RoleMap.CanCorrectMapRole threw exception:  NHibernate.ObjectNotFoundException: No row with the given identifier exists[HNI.Portal.Core.Entities.Application#1].

and the StackTrace:

NHibernate.Impl.SessionFactoryImpl.DefaultEntityNotFoundDelegate.HandleEntityNotFound(String entityName, Object id)
NHibernate.Event.Default.DefaultLoadEventListener.Load(LoadEvent event, IEntityPersister persister, EntityKey keyToLoad, LoadType options)
NHibernate.Event.Default.DefaultLoadEventListener.ProxyOrLoad(LoadEvent event, IEntityPersister persister, EntityKey keyToLoad, LoadType options)
NHibernate.Event.Default.DefaultLoadEventListener.OnLoad(LoadEvent event, LoadType loadType)
NHibernate.Impl.SessionImpl.FireLoad(LoadEvent event, LoadType loadType)
NHibernate.Impl.SessionImpl.Load(String entityName, Object id)
NHibernate.Impl.SessionImpl.Load(Type entityClass, Object id)
NHibernate.Impl.SessionImpl.Load[T](Object id)

I´m not sure if I should call Flush() and Clear() (still doing research on it), but I´m getting this error while writing tests with PersistenceSpecification. This is how PersistenceSpecification does on CheckList() assert to verify if a list is being correctly saved, which is not for me. I stepped into the code and got to this repro.

The application row is correctly inserted in the database but it won´t load again. It happens both with SqlServer and Sqlite.

Hope you guys can help me.

Thanks a lot!

Did you breakpoint your code to see whether the value of your ID is correct compared to the value identitied by your DBMS? — Will Marcouiller
– Will Marcouiller, Commented Feb 8, 2010 at 16:07

pedro · Accepted Answer · 2010-02-02 22:55:03Z

2

You are setting the id but it's an Identity. You should not set it, SQL does that for you.

Instead of creating a new session use the same one, and retrieve using Get instead of Load.

On the difference between Load and Get: http://ayende.com/Blog/archive/2009/04/30/nhibernate-ndash-the-difference-between-get-load-and-querying-by.aspx

edited Feb 2, 2010 at 22:55

answered Feb 2, 2010 at 20:53

pedro

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5 Comments

tucaz Over a year ago

This is odd. It saved the object (like it was doing before), then gave me a "row not found" exception when I tried to Load it. The important point is that I could make my assertion work be doing what you said and adding Cascade to parent of this Application entity. I will do some more testing to make sure everything is working.

dotjoe Over a year ago

+1 about identity id. -1 about session.Clear() since it makes sense to clear session while testing to make sure you hit db and not cache.

tucaz Over a year ago

pedro, I have .Clear() in my example because PersistenceSpecification.VerifyTheMappings uses it so I needed it to repro the problem.

Will Marcouiller Over a year ago

@Pedro: Creating a new session asserts that the Load() method hits the database. Using the same session, NHibernate could return the cached entity. Anyhow, it is only adviseable to use the same session within one and only context, either a WinForm or a WebPage. After this context is no longer viable, the session should be released in favor of another new one. Using the same session for too long cause memory leaks from the ISession interface as it keeps tracks of the entities manipulated.

pedro Over a year ago

@Will: Clear will completely evict all objects from the session cache. It could still be retrieved from the second level cache, if you did set it up, but considering it's a test wouldn't you say that Clear is enough ?

David Rubin · Accepted Answer · 2010-02-08 17:51:44Z

1

I think you're grabbing Id out of myApp too early. Try doing _session.Flush() before looking up Id. Since you're using an Identity Generator, NHibernate bubbles the generated Id back up to your object, but that doesn't happen until the session is flushed (usually at transaction commit-time).

answered Feb 8, 2010 at 17:51

David Rubin

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Comments

MoJo2600 · Accepted Answer · 2010-02-03 13:25:40Z

0

Your using two differen ways to create the session?

NHibernateHelper.CreateSession();

and

_sessionFactory.OpenSession();

maybe you should try _sessionFactory.OpenSession(); to get a session for retrieval.

answered Feb 3, 2010 at 13:25

MoJo2600

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1 Comment

tucaz Over a year ago

_sessionFactory is static inside NHibernateHelper so they are using the same Factory to create the session.

Tim Mahy · Accepted Answer · 2010-02-07 14:30:04Z

0

you don't need to flush manually since the framework will notice that you perform a search on an entity of which there are still pending changes, those changes will be flushed before the get, in this I think that idMyApp will be 1 instead of the right generated id from the database....causing your get code to fail...

answered Feb 7, 2010 at 14:30

Tim Mahy

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1 Comment

user24359 Over a year ago

He's creating a new session, though, and that new session won't notice those unflushed changes.

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