alibaba.fastjson允許輸出NULL並且把字串輸出為“”__js

使用JSON.toJSONString(str,SerializerFeature... serial);

SerializerFeature

QuoteFieldNames———-輸出key時是否使用雙引號,預設為true 
WriteMapNullValue——–是否輸出值為null的欄位,預設為false 
WriteNullNumberAsZero—-數值欄位如果為null,輸出為0,而非null 
WriteNullListAsEmpty—–List欄位如果為null,輸出為[],而非null 
WriteNullStringAsEmpty—字元類型欄位如果為null,輸出為”“,而非null 

WriteNullBooleanAsFalse–Boolean欄位如果為null,輸出為false,而非null

import com.alibaba.fastjson.JSON;import com.alibaba.fastjson.serializer.SerializerFeature;public class JavaToJson {    public static void main(String[] args) {        Class<?> c;        Object o;        try {            c = Class.forName("com.free.User");            o = c.newInstance();            String json = JSON.toJSONString(o,SerializerFeature.WriteMapNullValue,SerializerFeature.WriteNullStringAsEmpty);            System.out.println(json);        } catch (Exception e) {        }                   }}