I have a set of classes structured as follows:

public class A implements Serializable {
    String prop1;
    String prop2;
    B prop3;
}

public class B implements Serializable {
    String nestedProp4;
    String nestedProp5;
    C nestedProp6;
}

public class C implements Serializable {
    String nestedProp7;
}

I need to serialize an instance of class A. Here is the code I’m using:

A obj = new A();
ObjectMapper mapper = new ObjectMapper();
JsonNode node = mapper.valueToTree(obj);

The actual result of the serialization is:

{
    "prop1": null,
    "prop2": null,
    "prop3": null
}

However, I need the result to include the nested structure with null values for the properties, like this:

{
    "prop1": null,
    "prop2": null,
    "prop3": {
        "nestedProp4": null,
        "nestedProp5": null,
        "nestedProp6": {
            "nestedProp7": null
        }
    }
}

Is there an automatic way or configuration annotation to achieve this serialization without using reflection or setting default values?

Additionally, I have many properties in these classes, so I prefer not to add annotations to each property. Annotations at the top of the classes are allowed.