如何使用GSON只返回一个特定的空字段？

import com.google.gson.TypeAdapter;
import com.google.gson.stream.JsonReader;
import com.google.gson.stream.JsonWriter;

import java.io.IOException;

public class MyObjectAdapter extends TypeAdapter<MyObject> {

    @Override
    public void write(JsonWriter out, MyObject myObject) throws IOException {
        out.beginObject();
        if (myObject.getSpecialField() == null) {
            out.name("specialField").nullValue();
        } else {
            out.name("specialField").value(myObject.getSpecialField());
        }
        out.endObject();
    }

    @Override
    public MyObject read(JsonReader in) throws IOException {
        MyObject myObject = new MyObject();
        in.beginObject();
        while (in.hasNext()) {
            String name = in.nextName();
            if (name.equals("specialField")) {
                if (in.peek() == com.google.gson.stream.JsonToken.NULL) {
                    in.nextNull();
                    myObject.setSpecialField(null);
                } else {
                    myObject.setSpecialField(in.nextString());
                }
            } else {
                in.skipValue();
            }
        }
        in.endObject();
        return myObject;
    }
}

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;

public class Main {
    public static void main(String[] args) {
        Gson gson = new GsonBuilder()
                .registerTypeAdapter(MyObject.class, new MyObjectAdapter())
                .create();

        MyObject myObject = new MyObject();
        myObject.setSpecialField("Hello World");

        String json = gson.toJson(myObject);
        System.out.println(json);

        MyObject deserializedObject = gson.fromJson(json, MyObject.class);
        System.out.println(deserializedObject.getSpecialField());
    }
}