Base class with both subclass and joined-subclass?

s.rottem · **Posted:** Sat Aug 13, 2005 6:05 pm

Hi,

I've got a situation where we have a base class with multiple subclasses, however some of the subclasses don't have any additional properties to the base class while others do. As a result, I want to provide an extra table only for the subclasses that need to express extra property values.

So, my base class mapping:

Code:

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.0" namespace="Framework.Core.Entities" assembly="Framework.Core">

   <class name="InputProfile" table="InputProfiles">
      
      <id name="id" column="InputProfileID" unsaved-value="0" access="field">
         <generator class="native" />
      </id>
      
      <discriminator column="InputInterface" type="System.Byte"/>
      
      <version name="version" column="Version"  access="field"/>
      
      <property name="created" column="Created" update="false" access="field"/>
      <property name="deleted" column="Deleted" access="field"/>
      <property name="inputInterface" column="InputInterface" access="field" />
      <property name="modified" column="Modified" update="false" access="field"/>
      <many-to-one name="parentUser" column="ParentUserID" class="User" access="field" cascade="all"/>
   
   </class>
   
</hibernate-mapping>

A subclass without additional properties (although they may come later):

Code:

<?xml version="1.0" encoding="utf-8" ?> 
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.0" namespace="Framework.Core.Entities" assembly="Framework.Core">

   <subclass name="SmtpInputProfile" extends="InputProfile" discriminator-value="1">
   
   </subclass>

</hibernate-mapping>

And a subclass with additional properties in it's own table:

Code:

<?xml version="1.0" encoding="utf-8" ?> 
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.0" namespace="Framework.Core.Entities" assembly="Framework.Core">
   
   <joined-subclass name="FtpInputProfile" extends="InputProfile" table="FtpInputProfiles">
   
      <key column="FtpInputProfileID" />
      
      <property name="welcomeMessage" column="WelcomeMessage" access="field" />
            
   </joined-subclass>
   
</hibernate-mapping>

Obviously these are only examples and the classes that use the table per joined subclass actually have many more additional properties.

When I try to do this I'm getting a mapping exception:

Code:

[MappingException: Could not format discriminator value 'Framework.Core.Entities.InputProfile' to sql string using the IType NHibernate.Type.ByteType]
   NHibernate.Persister.EntityPersister..ctor(PersistentClass model, ISessionFactoryImplementor factory) in C:\Documents and Settings\Symon\My Documents\Visual Studio Projects\Third Party Components\nhibernate-0.9.0.0\src\NHibernate\Persister\EntityPersister.cs:147
   NHibernate.Persister.PersisterFactory.Create(PersistentClass model, ISessionFactoryImplementor factory) in C:\Documents and Settings\Symon\My Documents\Visual Studio Projects\Third Party Components\nhibernate-0.9.0.0\src\NHibernate\Persister\PersisterFactory.cs:43
   NHibernate.Impl.SessionFactoryImpl..ctor(Configuration cfg, Settings settings) in C:\Documents and Settings\Symon\My Documents\Visual Studio Projects\Third Party Components\nhibernate-0.9.0.0\src\NHibernate\Impl\SessionFactoryImpl.cs:139
   NHibernate.Cfg.Configuration.BuildSessionFactory() in C:\Documents and Settings\Symon\My Documents\Visual Studio Projects\Third Party Components\nhibernate-0.9.0.0\src\NHibernate\Cfg\Configuration.cs:894

Is this a bug, or is what I'm trying to accomplish not possible?

Cheers,

Symon.

KPixel · **Posted:** Mon Aug 15, 2005 12:37 pm

NHibernate don't support mixing subclass and joined-subclass.

You should be able to solve this issue using only joined-subclass...