alibaba的JSON.toString会把值为null的字段去掉，谨记

alibaba的JSON.toString会把值为null的字段去掉，谨记

　　　　Map<String,Object> map = new HashMap<>();
        map.put("a", "1");
        map.put("b", "2");
        map.put("c", null);
        String jsonString = JSON.toJSONString(map);
        System.out.println(jsonString);

结果：{"a":"1","b":"2"}

　　　　Map<String,Object> map = new HashMap<>();
        map.put("a", "1");
        map.put("b", "2");
        map.put("c", "");
        String jsonString = JSON.toJSONString(map);
        System.out.println(jsonString);

　　结果：{"a":"1","b":"2","c":""}