code: public static String stringify(final JsonNode json) {
          try {
              return json != null ? createObjectMapper().writeValueAsString(json) : "{}";
          } catch (JsonProcessingException jpx) {
              throw new RuntimeException("A problem occurred while stringifying a JsonNode: " + jpx.getMessage(), jpx);
          }
      }
docs: Convert a JsonNode to its string representation. If given
  value is null an empty json object will returned.
  
  @param json The json object to toJsonString
  @return stringified version of given json object