[FIXED] Returning a message for the client in json format along with data - Java/Spring/REST

Issue

I would like to return a custom message along with data that my endpoint is supposed to return in json format. E.g:

{
 "id": "1",
 "name": "John",
 "surname": "Jackson",
 "city": "Los Angeles"
 "message": "There was only 1 person in chosen category"
}  

So my POJO class of person has fields: id, name, surname, city. However I would like to return message too, so the client application can display the message on the front-end. I was looking for a solution. By default Controller endpoint can return the object as json no problem. But that just gives me data, 200 status and that's it. I found about returning ResponseEntity, but this doesn't solve the problem either since in response body it takes a POJO so I still can't send a custom message along with data. I need to send custom message, data and a proper status code.

Solution

You can create a generic class that you will return from your controllers which will enrich your models with message property :

public class ServerResponse {
    @JsonUnwrapped
    private final Object wrapped;
    private final String message;

    public ServerResponse(Object wrapped, String message) {
        this.wrapped = wrapped;
        this.message = message;
    }
    //getters
}

and then you can pass any object to this class in the constructor and let Jackson handle the serialization for you. This way you do not have to create a new class per your model :

User user = new User("1", "John", "Jackson", "Los Angeles");
ServerResponse serverResponse = new ServerResponse(user, "There was only 1 person in chosen category");

and when you return ServerResponse from the controller it will be serialized to :

{
   "id":"1",
   "name":"John",
   "surname":"Jackson",
   "city":"Los Angeles",
   "message":"message"
}

Answered By - Michał Krzywański
Answer Checked By - David Marino (JavaFixing Volunteer)