Convert class into a JSONObject

Question

I have several classes like this. I want to convert the classes into JSONObject format.

import java.io.Serializable;

import com.google.gson.annotations.SerializedName;

public class User implements Serializable {
    private static final long serialVersionUID = 1L;
    @SerializedName("id")
    private Integer mId;
    @SerializedName("name")
    private String mName = "";
    @SerializedName("email")
    private String mEmail;

    public Integer getId() {
        return mId;
    }
    public void setId(Integer id) {
        mId = id;
    }

    public String getName() {
        return mName;
    }
    public void setName(String name) {
        mName = name;
    }

    public String getEmail() {
        return mEmail;
    }
    public void setEmail(String email) {
        mEmail = email;
    }
}

I know that I can convert these classes to JSONObject format as follows:

    User user = new User();
    JSONObject jsonObj = new JSONObject();
    try {
        jsonObj.put("id", user.getId());
        jsonObj.put("name", user.getName());
        jsonObj.put("email", user.getEmail());
    } catch (JSONException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

The problem is that I need to do this for a lot of different classes that are much longer than this across a lot of files. Can I use GSON to fill the JSONObject from myClass so that I don't need to edit every time the class structure changes?

The following returns a JSON string but I need it as an Object as when I send it to the system that sends the requests via a REST API it sends with unwanted quotation marks.

User user = new User();
Gson gson = new Gson();
Object request = gson.toJson(user);

When I use this in another JSON builder that asks for an Object I get

{"request":"{"id":"100","name":"Test Name","email":"test@example.com"}"}

When I want

{"request":{"id":"100","name":"Test Name","email":"test@example.com"}}

Answer 1

I found that the following works with GSON:

    User = new User();
    Gson gson = new Gson();
    String jsonString = gson.toJson(user);
    try {
        JSONObject request = new JSONObject(jsonString);
    } catch (JSONException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

This is not type safe, however.

Answer 2

Here is a crude example you can use to use Reflection to build the JSONObject..

Warning it's not pretty and does not contain really type-safety.

public static JSONObject quickParse(Object obj) throws IllegalArgumentException, IllegalAccessException, JSONException{
    JSONObject object = new JSONObject();

    Class<?> objClass = obj.getClass();
    Field[] fields = objClass.getDeclaredFields();
    for(Field field : fields) {
        field.setAccessible(true);
        Annotation[] annotations = field.getDeclaredAnnotations();
        for(Annotation annotation : annotations){
            if(annotation instanceof SerializedName){
               SerializedName myAnnotation = (SerializedName) annotation;
               String name = myAnnotation.value();
               Object value = field.get(obj);

               if(value == null)
                  value = new String("");

               object.put(name, value);
            }
        }
    }   

    return object;
}

Here is an example usage:

User user = new User();
JSONObject obj = quickParse(user);
System.out.println(obj.toString(3));

Output

{
   "id": "",
   "name": "",
   "email": ""
}