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Editorial Team
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Asked: 2026-06-01T04:56:04+00:00

Consider a Transport table with 3 fields: Engine Wheels Wings If Engine and Wheels

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Consider a Transport table with 3 fields: Engine Wheels Wings

If Engine and Wheels are non-null and Wings is null then I wish to map this to a Vehicle class
If Engine and Wings are non-null and Wheels is null then I wish to map this to a Plane class

I have been reading about discriminators to differentiate between subclasses but in any of the examples that I’ve read, they always refer to a discriminator value. Therefore, I’m wondering how I can go about my above scenario?
Do I just implement separate mappings? I was hoping to find a neater way.

Thanks

Edit

Have just looked through the reference guide again and have noticed that null and not-null are valid values. So looks like this solves my problem. Will leave this open for a little while to confirm. Thanks!

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1 Answer

  1. Editorial Team

    You can create an abstract parent class for your Plane and Vehicle classes and use @DiscriminatorFormula, which you use to write a formula that generates a value that you can later annotate as the @DiscriminatorValue for the Plane and Vehicle subclasses.

    Take a look at this example in the Hibernate docs (though this example uses XML for the mapping, it’s basically the same thing for the annotation):

    http://docs.jboss.org/hibernate/core/3.6/reference/en-US/html/example-mappings.html#example-mappings-content-discrimination

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