java - JSON Jackson - exception when serializing a polymorphic class with custom serializer - Stack Overflow

java - JSON Jackson - exception when serializing a polymorphic class with custom serializer - Stack Overflow

You'll need to additionally override serializeWithType within you CustomPetSerializer because IPet is polymorphic. That's also the reason why serialize is not called. Check this related SO question that explains in detail when serializeWithType is called. For instance, your serializeWithType implementation might look something like this:

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