FireByMonthPOJO fireByMonth = new FireByMonthPOJO();

fireByMonth.setUnitNumber(unitNumber);

fireByMonth.setYearMonth(date);

fireByMonth = this.fireByMonthService.getFireByMonth(fireByMonth);

public FireByMonthPOJO getFireByMonth(FireByMonthPOJO fireByMonth);

如果mapper.xml里面对应的查询结果为空。这个会返回NULL吗？事实上返回的不为NULL,而是每个属性都为NULL的对象。