阿里巴巴json包 --------fastjson

fastjson对null的处理----String str2 = JSONObject.toJSONString(jsonMap, SerializerFeature.WriteMapNullValue); 

https://blog.csdn.net/l253272670/article/details/54912230

对时间的处理------https://blog.csdn.net/john1337/article/details/76277617