I've solved my problem temporarily by making a simple object wrapper class, but I've come across this problem that seems a little odd:

I have a class with a property of type java.lang.Object, I get the following exception:
org.hibernate.MappingException: property mapping has wrong number of columns: com.declivis.asc.dao.GenericStatus.objectWrapper type: object

Has anyone encountered this? I realize my workaround isn't really that painful, but I'm curious as to what the root of this problem is. Hibernate doesn't leave many clues in the log... it just throws this exception and shuts down.

More interesting to this point, is that I'm using the SchemaUpdate/Export mechanism(s) to build my tables in HSQLDB and it doesn't complain at all and builds the tables correctly. The failure comes once the attempt to build the session factory happens.

In case your curious - I'm using the subclasses to do the cast on this object to a type correct for the subclass.

Any thoughts or clues would be most appreciated.

Hibernate version: 3.0.5

Mapping documents:
<class name="com.declivis.asc.dao.GenericStatus" table="status">
<id name="id" type="int">
<column name="id" />
<generator class="identity" />
</id>
<discriminator column="type" type="string" length="3" />
<property name="key" type="string" >
<column name="key" length="64" index="IDX_GS_KEY"/>
</property>
<property name="state" type="int" >
<column name="state" length="3" />
</property>
<property name="objectWrapper" type="object" >
<column name="obj" sql-type="other" not-null="false" />
</property>
<subclass name="com.declivis.asc.dao.ProductStatus" discriminator-value="PFS" />
<subclass name="com.declivis.asc.dao.OrderStatus" discriminator-value="OFS" />
</class>

Code between sessionFactory.openSession() and session.close():
Session factory never gets running.

Full stack trace of any exception that occurs:
org.hibernate.MappingException: property mapping has wrong number of columns: com.declivis.asc.dao.GenericStatus.objectWrapper type: object

Name and version of the database you are using: HSQLDB 1.7.3

Debug level Hibernate log excerpt:
Jan 02 08:27:02 org.hibernate.tool.hbm2ddl.SchemaUpdate[INFO]: schema update complete
Jan 02 08:27:02 org.hibernate.cfg.Configuration[DEBUG]: Preparing to build session factory with filters : {}
Jan 02 08:27:02 org.hibernate.cfg.Configuration[INFO]: processing extends queue
Jan 02 08:27:02 org.hibernate.cfg.Configuration[INFO]: processing collection mappings
Jan 02 08:27:02 org.hibernate.cfg.Configuration[INFO]: processing association property references
Jan 02 08:27:02 org.hibernate.cfg.Configuration[INFO]: processing foreign key constraints
Jan 02 08:27:02 org.hibernate.cfg.Configuration[DEBUG]: resolving reference to class: com.declivis.asc.dao.InterimOrder
Jan 02 08:27:02 org.hibernate.cfg.Configuration[DEBUG]: resolving reference to class: com.declivis.asc.dao.Order
Jan 02 08:27:02 org.hibernate.impl.SessionFactoryImpl[INFO]: closing

I had this error, too.
However in my opinion it's never a good idea to map a property as "object".

Every data you save in the DB is either a String, a number, a date, some binary data etc. Why can't you map it as such?

If the predefined Hibernate-types don't meet your requisits, you can always write a user-type.