Using Jackson with composition over inheritance

Question

I'm trying to use Jackson to manage the types for me, but instead of using inheritance for types creation I want to use composition and have a set of factory methods with some annotation that will instruct Jackson what types these are. Concrete example:

@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, property = "type")
public interface MyInterface {
    void doStuff();

    // Factories

    @JsonCreator
    @JsonSubTypes.Type(value = MyInterface.class, name = "impl1")
    static MyInterface impl1() {
        return new MyInterfaceWithComposition(() -> System.out.println("Impl1"));
    }

    @JsonCreator
    @JsonSubTypes.Type(value = MyInterface.class, name = "impl2")
    static MyInterface impl2() {
        return new MyInterfaceWithComposition(() -> System.out.println("Impl2"));
    }
}

public class MyInterfaceWithComposition implements MyInterface {
    private final Runnable task;

    public MyInterfaceWithComposition(Runnable task) {
        this.task = task;
    }

    @Override
    public void doStuff() {
        task.run();
    }
}

I know I can create a custom serializer/deserializer, but I was hoping there's a way to avoid it and make Jackson do all the work.

It feels to me like it shouldn't be this hard to do this. Am I missing some Jackson trick/annotation? I'd appreciate your help.

Answer 1

@JsonUnwrapped can be used for composition.

Serialization for Person

    public class Person {
      public int age;
      @JsonUnwrapped
      public Name name;
    }

produces the following JSON.

    {
      "age" : 18,
      "first" : "John",
      "last" : "Doe"
    }

References:

• https://github.com/FasterXML/jackson-databind/blob/jackson-databind-2.12.3/src/test/java/com/fasterxml/jackson/databind/struct/TestUnwrapped.java#L168