Skip root element while deserializing json

Question

How should I deserialize following JSON to skip root element and parse just the inner part of this JSON. I'd like to avoid creating additional, 3rd class Root, which would include only MapWrapper field.

{
    "root": {
        "language": "en",
        "map": {
            "k1": {
                "name": "n1",
            },
            "k2": {
                "name": "n2",
            }
        }
    }
}

So I'd like to have only these two classes:

class MapWrapper {
    private String language;
    private Map<String, MyMapEntry> map;
}

class MyMapEntry {
    String name;
}

Answer 1

you can use GSON Library for this.

Below code will solve your problem.

public class ConvertJsonToObject {

    private static Gson gson = new GsonBuilder().create();

    public static final <T> T getFromJSON(String json, Class<T> clazz) {
        return gson.fromJson(json, clazz);
    }

    public static final <T> String toJSON(T clazz) {
        return gson.toJson(clazz);
    }
}

String json; // your jsonString
Map<String,Object> r = ConvertJsonToObject.getFromJSON(json,Map.class);
String innerJson = ConvertJsonToObject.toJson(r.get("root"));
MapWrapper _r = ConvertJsonToObject.getFromJSON(innerJson,MapWrapper.class);

Answer 2

Consider the following JSON:

{"authorization":{"username":"userabc", "password":"passabc"}}

The DTO for this JSON without the root element

public class Authorization {
    private String username;
    private String password;

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    // Add a container for the root element
    public static class Container {
        public Authorization authorization;
    }
}

Convert from/to JSON using the following methods (you can either keep this within DTO or some other help class)

public String toJson(Authorization authorization) {
    Gson gson = new Gson();
    Authorization.Container container = new Authorization.Container();
    container.authorization = authorization;
    return gson.toJson(container);
}

public Authorization fromJson(String json) {
    Gson gson = new Gson();
    Authorization.Container container = gson.fromJson(json, Authorization.Container.class);
    return container.authorization;
}