Jackson excluding type information for containeirs (List, Map, Collection) during serialization

Question

In Jackson I want to include type-information for every custom objects. To accomplish this without annotation, I am using

OBJECT_MAPPER.enableDefaultTypingAsProperty(DefaultTyping.NON_FINAL, "@Ketan");

It is working but it is also including type-information for List , Map , Collection like container itself.

Let me give you a standard example of Animal , Dog , Cat and Zoo hierarchy.

class Zoo {

    List<Cat> cats;
    Dog dog;

    public Dog getDog() {
       return dog;
    }

    public void setDog(Dog dog) {
       this.dog = dog;
    }

    public List<Cat> getCats() {
       return cats;
    }

    public void setCats(List<Cat> cats) {
       this.cats = cats;
    }

}

Here, I have two custom objects, Cat and Dog . I just want to include type information for only those, but it is including for container – List in my case – as well.

Please see below the JSON string I got by serialization.

{
    "@Ketan": "com.csam.wsc.enabling.core.codec.json.test.Zoo1",
    "cats": [
        // This line contains the issue //
        "java.util.ArrayList",
        [
            {
                "@Ketan": "com.csam.wsc.enabling.core.codec.json.test.Cat",
                "name": "animalName",
                "likesCream": true,
                "lives": 10
            },
            {
                "@Ketan": "com.csam.wsc.enabling.core.codec.json.test.Cat",
                "name": "animalName",
                "likesCream": true,
                "lives": 10
            }
        ]
    ],
    "dog": {
        "@Ketan": "com.csam.wsc.enabling.core.codec.json.test.Dog",
        "name": "animalName",
        "barkVolume": 0.0
    }
}

Everything is fine to me except what I have highlighted – java.util.ArrayList in the JSON string. I do not want such a container type information.

Is there any easy support at above API level itself to achieve this without overriding TypeResolverBuilder or any customization?

Answer 1

If you extend the class ObjectMapper.DefaultTypeResolverBuilder , it becomes quite easy though:

OBJECT_MAPPER.setDefaultTyping(new ObjectMapper.DefaultTypeResolverBuilder(ObjectMapper.DefaultTyping.NON_FINAL) {
    {
        init(JsonTypeInfo.Id.CLASS, null);
        inclusion(JsonTypeInfo.As.PROPERTY);
        typeProperty("@Ketan");
    }

    @Override
    public boolean useForType(JavaType t) {
        return !t.isContainerType() && super.useForType(t);
    }
});

Answer 2

不可以，除非您声明集合为最终类型。