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Using @DiscriminatorColumn for Inheritance

Heathcliff Della-Franca
Greenhorn

Joined: Jan 19, 2004
Posts: 2
Hi, I am wondering if anyone can help.

I have a set of classes Apple, Orange and Banana which all inherit from the Fruit class. I want to use the Single Table Strategy to persist all of the Fruit classes.

I understand I can use a @DiscriminatorColumn('FruitType') in the Fruit class and the @DiscriminatorValue('Apple'), @DiscriminatorValue('Orange') and @DiscriminatorValue('Banana') in the Apple, Orange and Banana classes, then make sure I have the FruitType column on the database set to either Apple, Orange or Banana.

What I would rather do if possible is have a FruitTypes table in the database to hold a list of valid @DiscriminatorValues, something like this:

Id Name
------------
1 Apple
2 Orange
3 Banana

Then I could set up FruitTypeId on the Fruit table as a foreign key to FruitTypes and instead of using 'Apple', 'Orange' or 'Banana' I could use 1, 2 or 3.

However I would still like to keep the meaningful @DiscriminatorValues in the Apple, Orange and Banana classes i.e. @DiscriminatorValue('Apple') instead of @DiscriminatorValue('1').

Is there a value for @DiscriminatorColumn that will achieve this? Something like:

@DiscriminatorColumn('SELECT FruitType.Name FROM FruitType, Fruit WHERE FruitType.Id = Fruit.FruitTypeId')
 
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subject: Using @DiscriminatorColumn for Inheritance