zoukankan      html  css  js  c++  java
  • mapper文件一次空指针异常记录

         一个简单的查询,mapper文件的配置如下:

    <select id="querySupplierAndDriverId" resultType="com.zhuanche.entity.mdbcarmanage.DriverInfoInterCity">
      select  driver_id ,city_id ,supplier_id  
      from driver_info_inter_city
      where driver_id IN
      <foreach collection="driverIds" open="(" close=")" separator="," item="driverId" >
        #{driverId}
      </foreach>
      AND  status = 1
    </select>

    结果在使用的时候,一直报空指针异常。但是看了下数据库里面也能查询到数据,怎么就空指针了呢?

     最后想了下,是这个查询 的结果和resultType的字段没有匹配一块导致的,没有查询出来,按照我的理解,应该是会new 一个对象的,但是应该是没有。先把问题改了

      <select id="querySupplierAndDriverId" resultType="com.zhuanche.entity.mdbcarmanage.DriverInfoInterCity">
        select  driver_id as driverId,city_id as cityId,supplier_id as supplierId
        from driver_info_inter_city
        where driver_id IN
        <foreach collection="driverIds" open="(" close=")" separator="," item="driverId" >
          #{driverId}
        </foreach>
        AND  status = 1
      </select>

    有空研究下源码

  • 相关阅读:
    LintCode A+B问题
    LintCode 斐波纳契数列
    LintCode 删除链表中的元素
    LintCode 整数排序
    c++ lower_bound upper_bound
    259. 3Sum Smaller
    86. Partition List
    209. Minimum Size Subarray Sum
    11. Container With Most Water
    360. Sort Transformed Array
  • 原文地址:https://www.cnblogs.com/thinkingandworkinghard/p/12119732.html
Copyright © 2011-2022 走看看