How to check if all the variables in the object is empty?

Question

JSON response:

{
  "id": "",
  "status": "",
  "Date": "",
  "Name": ""
}

When I try to map it with the class using object mapper.
Name of class is Demo with the field same in json response.
It mapped like:

Demo(id=, status=, Date=, Name=)

There are around 10-15 variables in the response.
I want to know if all the variables of Demo object are empty.

Answer 1

by using

JsonNode node = mapper.readTree(jString);

node.isNull();

you will get node is null or not using

node.get("id").isNull();
node.get("id").isEmpty(); 

you can verify the content of JsonNode

Answer 2

A pure Java solution¹ could be using reflection. Here a very simple implementation, mostly to show the idea (not complete, assuming fields are String, poor (no) exception handling):

public static boolean isEmpty(Demo demo) throws IllegalArgumentException, IllegalAccessException {
    for (var field : Demo.class.getDeclaredFields()) {
        if (field.getType() == String.class) {
            var value = (String) field.get(demo);
            if (value != null && !value.isEmpty()) {
                return false;
            }
        }
    }
    return true;
}

It could be improved for example by adding more types, using annotation on fields, ...

^{1: question is only tagged java}
_{var was introduced in Java 10; use the concrete type (for (Field... or String value...) if using previous version of Java}