I cross-asked the question on stackoverflow (
http://stackoverflow.com/questions/1045573/how-to-manage-a-multiple-level-class-hierarchy-in-nhibernate-with-table-per-class)
and they correctly pointed out that I needed to nest my subclass elements.
That worked for me, so I no longer have an issue.
Here is the corrected mapping file:
<?xml version="1.0" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
assembly="NHibernateTesting"
namespace="NHibernateTesting" >
<class name="IActivity"
lazy="false"
table="Activity"
discriminator-value="0"
abstract="true">
<id name="Id">
<generator class="guid" />
</id>
<discriminator column="Type" type="Int16" />
<subclass name="Activity"
discriminator-value="1"
abstract="true"
lazy="false"
extends="IActivity">
<property name="StartTime" />
<subclass name="Running"
discriminator-value="2"
lazy="false"
extends="Activity">
<property name="Where" />
</subclass>
<subclass name="Talking"
discriminator-value="3"
lazy="false"
extends="Activity">
<property name="ToWhom" />
</subclass>
</subclass>
</class>
</hibernate-mapping>
On Mon, Jun 29, 2009 at 9:14 AM, Michael Hedgpeth <[email protected]>wrote:
>
> In hopes that I can get a solution to my problem, I did some more
> research with the NHibernate codebase. The problem seems to be in
> SingleTableEntityPersister.cs, line 543, DiscriminatorFilterFragment
> (string alias) method which has this code:
>
> string[] subclasses = SubclassClosure;
> for (int i = 0; i < subclasses.Length; i++)
> {
> IQueryable queryable = (IQueryable)
> Factory.GetEntityPersister(subclasses[i]);
> if (!queryable.IsAbstract)
>
> frag.AddValue(queryable.DiscriminatorSQLValue);
> }
> StringBuilder buf = new
> StringBuilder(50).Append(" and ").Append
> (frag.ToFragmentString().ToString());
>
> When trying to create the discriminator filter fragment ("IN (2, 3,
> 4)") for IActivity, the system only sees "Activity" as the subclass
> (result of SubclassClosure). Which is fine; I'd expect that if it
> recursively added all discriminator values not only for subclasses but
> for subclasses of subclasses.
>
> Also, when I take the interface out of it, it seems to be ok with
> inheritance at multiple levels. The problem only occurs when I try to
> make an interface the base type.
>
> Finally, I saw that I made a mistake in my example here; Activity
> should have been coded as abstract but wasn't. The problem still
> remains when I make this correction.
>
> Is there something I need to do to provide more information beyond
> this?
>
> On Jun 25, 1:36 pm, Michael Hedgpeth <[email protected]> wrote:
> > I have an issue with NHibernate giving me the following error:
> >
> > System.NotSupportedException: Attempting to parse a null value into an
> > sql string (column:activity0_.Type).
> > at NHibernate.SqlCommand.InFragment.ToFragmentString() in
> > InFragment.cs: line 109
> > at
> >
> NHibernate.Persister.Entity.SingleTableEntityPersister.DiscriminatorFilterFragment
> > (String alias) in SingleTableEntityPersister.cs: line 551
> >
> > I set up a simple solution to reproduce the error. I have the
> > following domain classes:
> >
> > public interface IActivity
> > {
> > Guid Id { get; set; }
> > }
> >
> > public class Activity : IActivity
> > {
> > public DateTime StartTime { get; set; }
> > public Guid Id { get; set; }
> > }
> >
> > public class Running : Activity
> > {
> > public string Where { get; set; }
> > }
> >
> > public class Talking : Activity
> > {
> > public string ToWhom { get; set; }
> > }
> >
> > And the following mapping xml:
> >
> > <?xml version="1.0" ?>
> > <hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
> > assembly="NHibernateTesting"
> > namespace="NHibernateTesting" >
> > <class name="IActivity"
> > lazy="false"
> > table="Activity"
> > discriminator-value="0"
> > abstract="true">
> > <id name="Id">
> > <generator class="guid" />
> > </id>
> > <discriminator column="Type" type="Int16" />
> > <subclass name="Activity"
> > discriminator-value="1"
> > abstract="true"
> > lazy="false">
> > <property name="StartTime" />
> > </subclass>
> > <subclass name="Running"
> > discriminator-value="2"
> > lazy="false"
> > extends="Activity">
> > <property name="Where" />
> > </subclass>
> > <subclass name="Talking"
> > discriminator-value="3"
> > lazy="false"
> > extends="Activity">
> > <property name="ToWhom" />
> > </subclass>
> > </class>
> > </hibernate-mapping>
> >
> > Any idea what I am doing wrong?
> >
> > Thanks!
> > Michael Hedgpeth
> >
>
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