Trouble with <version>

stovesy · **Joined:** Tue Jun 06, 2006 4:47 am **Posts:** 25

I'm having a problem with using the <version> tag with NHibernate-1.2.1.GA-src.

The problem hovers around FlushEntities() in SessionImpl.cs:
The Version property of entry (EntityEntry entry = (EntityEntry) me.Value;) is null, and causes a NullReferenceException when the version is called to be incremented in:

Code:

object nextVersion = GetNextVersion(persister, values, entry, hasDirtyCollections, dirtyProperties);

I've got an int version property and have defined it in the mapping file as <version name="Version" column="version"/>

Any clues ?

Thanks

marcal · **Posted:** Wed Dec 26, 2007 5:50 pm

How is your version property null? There shouldn't be a problem if you allow it to default to 0.

stovesy · **Joined:** Tue Jun 06, 2006 4:47 am **Posts:** 25

My version property is not getting set.

NHibernate is causing an exception before returning a value to my version property.

marcal · **Posted:** Wed Jan 09, 2008 12:44 pm

Need more details. Could you post some mapping, class, and failing code? It sounds like some DDL for the table might be useful in this case, too. I have never had problems like this with <version>.

stovesy · **Joined:** Tue Jun 06, 2006 4:47 am **Posts:** 25

This has raised its head again. (In nHibernate 2.0.0.1)

The problem occurs when the version field in the (postgres) table (an integer field) has no value.
When this field is set to zero - everything works fine.

When the db field is left with no value - the 'EntityEntry.Version' field turns out to be null. But examining the propertyValues, the value of the id field is correct (not null).

This is weird, because in my business object, the version field is being set with a value of 0, and returning 0.

The mapping entry is:-

Code:

<version name="Version" column="version" unsaved-value="0" type="Int32" access="property"/>

But that has gone through many incarnations, and none of the options worked.

The only thing that has worked is to give the field a default value.
Is this how it should be ?

The problem shows itself in DefaultFlushEntityEventListener at line 320

Code:

               object nextVersion = isVersionIncrementRequired ? 
                  Versioning.Increment(entry.Version, persister.VersionType, @event.Session) : 
                  entry.Version; //use the current version

Thanks.

mabraham · **Joined:** Mon Mar 20, 2006 10:49 pm **Posts:** 59

I see a couple of potential sources of the problem. First, it seems that version in the DB should always have a value. Second, if version in the DB does not have a value, there is an inconsistency between the table definition and the mapping, where version is defined as Int32, a non-nullable type. I believe in these situations NH will convert the null to a zero when setting the property.

stovesy · **Joined:** Tue Jun 06, 2006 4:47 am **Posts:** 25

So maybe what is happening, is NHibernate is setting the version internally as null, which is correct as that's what is in the database. But it's being nice and converting the null to a zero when setting the version property in the business object.

All fair enough. The simple answer it to set a default value in the database table.
Just think that the exception should be handled better.