How to make a Random Json generator java function with feilds, nestedness of the JSON ,key and value types passed as parameters?

I have to create a Random Json to fill a column of a sql table. For this I need to create a function to create a random Json in Java which will be passed the number of fields, nestedness of the JSON(for now assuming 1 for simplicity), key and value type.

Eg:- I want to generate and return this from that function :-

{
  "abcd" : "wedcevef",
  "bshe" : "eyguhcve",
  "uehv" : "dchbjvnn",
  "ecue" : "gchbccwg",

}

For the above example the number of feilds=4, nestedness=1, keyType= string(4) , valueType=string(8).

For making the random JSON key and values I already have a function :-

 public String astring(int minimum_length, int maximum_length) {
        return randomString(minimum_length, maximum_length, 'a', 26);
    }

 private String randomString(int minimum_length, int maximum_length, char base, int numCharacters) {
        int length = number(minimum_length, maximum_length);
        byte baseByte = (byte) base;
        byte[] bytes = new byte[length];
        for (int i = 0; i < length; ++i) {
            bytes[i] = (byte) (baseByte + number(0, numCharacters - 1));
        }
        return new String(bytes);
    }

How should I design this function? keeping in mind the nestedness will increase later on?