Java: Make Json output showing "null" explicitly instead of hiding the null field

Question

I have the following class, and I do output the objects of the class in Json string format:

public final class MyClass {

    private String field1 = null;
    private String field2 = null;

    @Override
    public final String toString() {
        return toJsonString();
    }

    public final String toJsonString() {
        return (new Gson()).toJson(this);
    }

    :
    :

    public static void main(String[] args) {

        MyClass a = new MyClass();
        a.field1 = "Hello";

        System.out.println(a);
    }

}

The above code, the main program output is below:

{"field1":"Hello"}

Is it possible to make it output:

{"field1":"Hello", "field2":null}

Thanks!

yshavit · Accepted Answer · 2016-03-02 22:01:25Z

1

The default configuration for Gson ignores nulls, but you can use GsonBuilder to change that:

Gson gson = new GsonBuilder().serializeNulls().create();
return gson.toString(this);

The user guide describes this, and the javadocs describe the other options GsonBuilder gives you.

answered Mar 2, 2016 at 22:01

yshavit

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