• 解決方法
  • 解決方案
  • 修改程式碼

問題描述

表結構

t_employee表（員工表）

t_department表（部門表）

查詢的xml對映

EmployeeMapper.xml

<resultMap id="BaseAndDepartmentResultMap" type="cn.comman.crud.pojo.Employee">
   <id column="id" javaType="java.lang.Integer" jdbcType="INTEGER" property="id"/>
 

   <result column="name" javaType="java.lang.String" jdbcType="VARCHAR" property="name"/>
   <result column="gender" javaType="java.lang.String" jdbcType="CHAR" property="gender"/>
   <result column="email" javaType="java.lang.String" jdbcType="VARCHAR" property="email"/>
   <result
 
 column="dpt_id" javaType="java.lang.Integer" jdbcType="INTEGER" property="dptId" />
   <association property="department" javaType="cn.comman.crud.pojo.Department">
       <id column="id" property="id"/>
       <result column="name" property="name"/>
   </association>
</resultMap
 
>

<sql id="Base_And_Department_Column_List">
   e.id, e.name, e.gender, e.email, e.dpt_id, d.id, d.name
</sql>

<select id="selectByExampleWithDepartment" resultMap="BaseAndDepartmentResultMap">
   select
   <if test="distinct">
       distinct
   </if>
   <include refid="Base_And_Department_Column_List" />
   from t_employee e
   left join t_department d on e.dpt_id = d.id
   <if test="_parameter != null">
       <include refid="Example_Where_Clause" />
   </if>
   <if test="orderByClause != null">
       order by ${orderByClause}
   </if>
</select>

問題

因為t_employee表和t_department表中都有id和name欄位， 所以按照以上方法在查詢過程中， department的id和name不能正常賦值。

解決方法

解決方案

給查詢的衝突欄位賦予別名，再把resultMap中的column值改為賦予的別名

修改程式碼

<sql id="Base_And_Department_Column_List">
   e.id, e.name, e.gender, e.email, e.dpt_id, d.id, d.name
</sql>

改為

<sql id="Base_And_Department_Column_List">
   e.id, e.name, e.gender, e.email, e.dpt_id, d.id did, d.name dname
</sql>

   <association property="department" javaType="cn.comman.crud.pojo.Department">
       <id column="id" property="id"/>
       <result column="name" property="name"/>
   </association>

改為

   <association property="department" javaType="cn.comman.crud.pojo.Department">
       <id column="did" property="id"/>
       <result column="dname" property="name"/>
   </association>