Reading such an information does not seem to be very interesting...
the framework does it for you and create the object accordin gto the value of this column !
it may be possible to consider this 'technical column' as a 'functional one' (not a good thing in my opinion), adding a property to map this column in your entity...
Why do you need the discriminator value? I use
instanceofto determine the class of object and not the discr. value.