https://www.cnblogs.com/shoufeng/p/11196500.html
JSONObject object = JSONObject.parseObject(jsonString);
String pretty = JSON.toJSONString(object, SerializerFeature.PrettyFormat, SerializerFeature.WriteMapNullValue, SerializerFeature.WriteDateUseDateFormat);
原文：https://www.cnblogs.com/danhuai/p/12828733.html