Hibernate version:
3.0

Mapping Strategy Question
I'm converting a legacy application to Hibernate and got a single table in the database which is pretty wide [30+ columns]. The Java classes which this table maps to has a class hierarchy like this:

SearchModel
|
V
DetailModel

The SearchModel has about 10 columns from the table. The DetailModel extends the SearchModel class and has fields for the rest of the columns.

I tried using the "Table per Class Hierarchy" strategy and a single mapping file which holds the hibernate mappings for both SearchModel and DetailModel. I get this exception when I try to use the mapping file:

org.hibernate.MappingException: No discriminator found for [...]DetailModel. Discriminator is needed when 'single-table-per-hiearchy' is used and a class has subclasses.

The table actually has no column I can map the descriminator to, any row in the table could be mapped to either the SearchModel or the DetailModel.

My questions are these:

Is "Table per Class Hierarchy" the right strategy to use in this case? If it is, then how do I get around the discriminator requirement hibernate is complaining about?

Table per class hierarchy does require a discriminator column. You may have to go with table per concrete class. Check out this article for further info:

http://www.agiledata.org/essays/mappingObjects.html

Could this be accomplished using the following?

<class name="Cat"
polymorphic="explicit"
discriminator-value="not null"
>
<discriminator column="cat_id"> <!-- never null -->
...

<subclass name="DomesticCat"
discriminator-value="not null"
>
...
<property name="domesticCatHome" column="home_addr"/>

</subclass>


</class>


In this case all rows will match both the Cat class and DomesticCat class, yet the returned type must be declared by the hql (polymorphic='explicit').

Am I mistaken in the meaning of the discriminator attributes? I'm trying to achieve a similar objective of the original post. I need the ability to return only a subset of the columns (due to security) and all columns programmatically.

Thanks!
PT