Add SubType information at runtime using Jackson for polymorphism

I ended up using Reflections library to find all subtype of Animal class, and register JsonSubTypes with mapper.registerSubtypes(Class<?>... classes) method.

Don't use @JsonSubTypes. Use @JsonTypeInfo#use with JsonTypeInfo.Id.CLASS to identify types for serialization and deserialization.

@JsonTypeInfo(use = JsonTypeInfo.Id.CLASS, include = JsonTypeInfo.As.PROPERTY, property = "type")
abstract class Animal { /* whatever */ }

Jackson will then store the fully qualified name to serialize the object and use it again to determine a target class for deserialization.

You'll have to make sure none of the subclasses have a property named type.

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It's possible to make this work with @JsonSubTypes but it involves mixins and is not a very maintainable solution.