记一次对象序列化不打印value值为null的属性问题

背景：

　　开发时遇到问题，看日志的入参的busiData中没有intRate这个属性，后面转成map时，有个判断

if（map.containsKey("intRate")）｛
   BigDecimal amt = new BigDecimal(datas.get("intRate")); 
｝

一直报空指针异常，很郁闷这个参数是怎么添加进去的，而且值是null

测试代码如下：

@Test
    public void test() {
        String json = "{"busiData":{"intRate1":null,"intRate2":"","overdueFlag":"N","firstDue":"51.594","loanPeriod":"12"},"loanAmt":6000.00,"loanDays":30,"productCode":"360JINXIAO","refundMethod":"03"}";
        CouponExchangeInput couponExchangeInput = JSONObject.parseObject(json, CouponExchangeInput.class);
        System.out.println(couponExchangeInput);
        logger.info("couponExchangeInput：{}", couponExchangeInput);

        System.out.println("---------");

        Map<Object, Object> map = new HashMap<>();
        map.put("intRate1",null);
        map.put("intRate2","");
        map.put("intRate3","aaa");
        System.out.println(map);
        logger.info("map：{}", map);
    }

结果：

{"busiData":{"overdueFlag":"N","firstDue":"51.594","loanPeriod":"12","intRate2":""},"loanAmt":6000.00,"loanDays":30,"productCode":"360JINXIAO","refundMethod":"03"}
INFO  [main] [TestCoupon:301] - couponExchangeInput：{"busiData":{"overdueFlag":"N","firstDue":"51.594","loanPeriod":"12","intRate2":""},"loanAmt":6000.00,"loanDays":30,"productCode":"360JINXIAO","refundMethod":"03"}
---------
{intRate3=aaa, intRate1=null, intRate2=}
INFO  [main] [TestCoupon:308] - map：{intRate3=aaa, intRate1=null, intRate2=}

结论：

　　对象的属性值为null，那么日志中不会打印该属性；属性值为空字符串，日志中会打印该属性

　　map中，不论value值为null还是为空字符串，日志中都会打印所有的键值对；