[nhibernate-issues] [NHJIRA] Commented: (NH-2568) Cannot Create Custom Persister for Collection Type

[Fabio M. (JIRA) <nh...@gm...>]

    [ http://216.121.112.228/browse/NH-2568?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=20683#action_20683 ] 

Fabio Maulo commented on NH-2568:
---------------------------------

btw Jeff, what we need is not the patch (that will be another), what we need is a little tests or at least needed classes and mappings (at least...).

> Cannot Create Custom Persister for Collection Type
> --------------------------------------------------
>
>                 Key: NH-2568
>                 URL: http://216.121.112.228/browse/NH-2568
>             Project:  NHibernate
>          Issue Type: Bug
>          Components: Core
>    Affects Versions: 3.0.0.GA
>            Reporter: Jeff Greenland
>            Priority: Major
>
> Encountered issue where setting a Persister Type on a collection property (specifically a type of List) would throw a NullPointerException when NHibernate initialized.  Our persister, called MyPersister as a test, extended OneToManyPersister and only had a constructor defined which matched the constructor in the base class (OneToManyPersister).  Here's our analysis as to why it looks like a bug:
> Tracing through the code revealed that a constructor was not found on MyPersister matching the expected arguments.  Those arguments are defined on line 34 of PersisterFactory.cs for CollectionPersister types and are Mapping.Collection, ICacheConcurrencyStrategy, and ISessionFactoryImplementor.
> In the CreateCollectionPersister() method (line 68), if there is no persister class defined, it calls the OneToManyPersister implementation of ICollectionPersister with Mapping.Collection, ICacheConcurrencyStrategy, Configuration, and ISessionFactoryImplementor parameters.  However, if a custom persister class is defined, it calls the Create() method (line 124) with the Configuration parameter missing, and consequently the Create() method does not invoke a matching constructor with that parameter.
> It seems to us that since the default persister class of OneToManyPersister accepts the 4 argument constructor, and if you specified a custom persister that extends OneToManyPersister, the custom persister should accept the same 4 arguments.  In other words, if I specify a custom persister on my class as OneToManyPersister (the same as the default), NHibernate would fail to initialize because it couldn't construct OneToManyPersister.
> Looks related to NH-1957, which appears to have been immediately closed.  I've included our diff below that seems to have fixed the issue.
> Diff:
> Index: PersisterFactory.cs
> ===================================================================
> --- PersisterFactory.cs	(revision 31412)
> +++ PersisterFactory.cs	(revision 31413)
> @@ -31,14 +31,15 @@
>  
>  		// TODO: is it really necessary to provide Configuration to CollectionPersisters ? Should it not be enough with associated class ?
>  		// or why does ClassPersister's not get access to configuration ?
> -		private static readonly System.Type[] CollectionPersisterConstructorArgs = new System.Type[]
> +        private static readonly System.Type[] CollectionPersisterConstructorArgs = new System.Type[]
>  			{
>  				typeof(Mapping.Collection),
>  				typeof(ICacheConcurrencyStrategy),
> +                typeof(Configuration),
>  				typeof(ISessionFactoryImplementor)
>  			};
>  
> -		/// <summary>
> +        /// <summary>
>  		/// Creates a built in Entity Persister or a custom Persister.
>  		/// </summary>
>  		public static IEntityPersister CreateClassPersister(PersistentClass model, ICacheConcurrencyStrategy cache,
> @@ -78,10 +79,11 @@
>  			}
>  			else
>  			{
> -				return Create(persisterClass, model, cache, factory);
> +                return (ICollectionPersister) Create(persisterClass, model, cache, cfg, factory);
>  			}
>  		}
>  
> +
>  		/// <summary>
>  		/// Creates a specific Persister - could be a built in or custom persister.
>  		/// </summary>
> @@ -122,7 +124,7 @@
>  		}
>  
>  		public static ICollectionPersister Create(System.Type persisterClass, Mapping.Collection model,
> -		                                          ICacheConcurrencyStrategy cache, ISessionFactoryImplementor factory)
> +                                                  ICacheConcurrencyStrategy cache, Configuration cfg, ISessionFactoryImplementor factory)
>  		{
>  			ConstructorInfo pc;
>  			try
> @@ -136,8 +138,8 @@
>  
>  			try
>  			{
> -				return (ICollectionPersister) pc.Invoke(new object[] {model, cache, factory});
> -			}
> +                return (ICollectionPersister)pc.Invoke(new object[] { model, cache, cfg, factory });
> +            }
>  			catch (TargetInvocationException tie)
>  			{
>  				Exception e = tie.InnerException;
> @@ -155,5 +157,6 @@
>  				throw new MappingException("Could not instantiate collection persister " + persisterClass.Name, e);
>  			}
>  		}
> +        
>  	}
>  }

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