About the use of @ForceDiscriminator/@DiscriminatorOptions(force=true)

Question

Why is @ForceDiscriminator or its equivalent @DiscriminatorOptions(force=true) necessary in some cases of inheritance and polymorphic associations?

Answer 1

@yannisf ForceDiscriminator is not the only solution to solve this issue.

You can do instanceof tests for each child class. Though this will be like hardcoding your classes in your code but is a cleaner way to solve the problem if the discriminator column is not populated.

This also helps your code avoid mixing jpa and hibernate annotations.

As pointed out by yannisf, instanceOf is kind of an antipattern in the OO world.

Another solution could be changing your entity mapping. Suppose an entity A has a refernce to a superclass B and B has child classes of type C1 and C2, the instead of A pointing to B, you can have C1 and C2 have a foreign key pointing to A. It all comes down to changing the entity design so as not to mix annotations.

Thanks Vaibhav