Jackson polymorphism: How to map multiple subtypes to the same class

The bug has been resolved in the version 2.6.0, so you just have to update Jackson to version 2.6.0 or later. The additional information is here and here.

Perhaps not by using annotations. Problems comes from the fact that such mapping would not work for serialization, and existing mapping does expect one-to-one (bijection) relationship. But you may want to file an RFE at jackson-databind issue tracker; adding support may be possible.

I also faced the same issue and found out that the Subtype mapping expects unique classes.

What I did was to create two classes that extend the same base class. The extended classes are empty as they have the same properties as base class. Then added them to the Subtype map. For example, in your case, it will be -

@JsonTypeInfo(use = Id.NAME, include = As.PROPERTY, property = "type")
@JsonSubTypes({@JsonSubTypes.Type(value = Mammal.class, name = "Dog"),
            @JsonSubTypes.Type(value = Mammal.class, name = "Cat"),
            @JsonSubTypes.Type(value = BirdDodo.class, name = "Dodo"},
            @JsonSubTypes.Type(value = BirdCockatoo.class, name = "Cockatoo"})
public class Animal {

}

public class BirdCockatoo extends Cockatoo{}
public class BirdDodo extends Dodo{}

I understand it is the not the best approach but until the issue is not resolved, it could be the best way to fix this. I followed this approach for now.

Hope it helps you!

You may introduce a middle-level abstract classes.

You may also avoid listing the whole list of subtypes and use @JsonTypeName.
This solution is IMHO more ellegant, because

• the definitions are right next to the actual subtype,
• long list of subtypes makes the code less maintainable,
• you can "plug-in" classes on other places.

Howto

By default, Jackson does not traverse the type tree to find about nested subtypes. It would fail with:

Could not resolve type id 'Dodo' as a subtype of
ch.zizka.test.Animal: known type ids = [com.zizka.test.Bird, ... Mammal] ...
at [Source: (byte[])"{

You need to add @JsonSubTypes to the middle-level classes (Bird, Mammal).

The result

• Animal with @JsonTypeInfo(use=NAME)
  • Mammal with @JsonSubTypes(@Type(Dog.class, Cat.class))
    • Dog with @JsonTypeName("Dog")
    • Cat with @JsonTypeName("Cat")
  • Bird with @JsonSubTypes(@Type(Dodo.class, Cockatoo.class))
    • Dodo with @JsonTypeName("Dodo")
    • Cockatoo with @JsonTypeName("Cockatoo")

Just tested - #WORKSFORME. (Jackson 2.10.5)