mybatis--01重复使用resultmap，便于在association中自动映射。

便于在association中自动映射。需要加一个columnPrefix。

columnPrefix： 在resultMap的元素中加自动加前缀，便于重用resultmap。

例：

1.在每个字段上加author_

<resultMap id="authorResult" type="Author">
  <id property="id" column="author_id"/>
  <result property="username" column="author_username"/>
  <result property="password" column="author_password"/>
  <result property="email" column="author_email"/>
  <result property="bio" column="author_bio"/>
</resultMap>

2.association中使用

<resultMap id="blogResult" type="Blog">
  <id property="id" column="blog_id" />
  <result property="title" column="blog_title"/>
  <association property="author"
    resultMap="authorResult" />
  <association property="coAuthor"
    resultMap="authorResult"
    columnPrefix="co_" />
</resultMap>

 3.执行sql

<select id="selectBlog" resultMap="blogResult">
  select
    B.id            as blog_id,
    B.title         as blog_title,
    A.id            as author_id,
    A.username      as author_username,
    A.password      as author_password,
    A.email         as author_email,
    A.bio           as author_bio,
    CA.id           as co_author_id,
    CA.username     as co_author_username,
    CA.password     as co_author_password,
    CA.email        as co_author_email,
    CA.bio          as co_author_bio
  from Blog B
  left outer join Author A on B.author_id = A.id
  left outer join Author CA on B.co_author_id = CA.id
  where B.id = #{id}
</select>

改造结果：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.ruoyi.ruoyiwx.mapper.WxMassMapper">

    <resultMap id="MassandsendResult" type="WxMass" autoMapping="true" >
<!--        <id property="id" column="id"/>-->
<!--        <result property="sysUnitId" column="sys_unit_id" />-->
<!--        <result property="name" column="name" />-->
<!--        <result property="type" column="type" />-->
<!--        <result property="mediaId" column="media_id" />-->
<!--        <result property="picurl" column="picurl" />-->
<!--        <result property="scope" column="scope" />-->
<!--        <result property="content" column="content" />-->
<!--        <result property="status" column="status" />-->
<!--        <result property="wxid" column="wxid" />-->
<!--        <result property="opBy" column="opBy" />-->
<!--        <result property="opAt" column="opAt" />-->
<!--        <result property="delFlag" column="delFlag" />-->
        <association property="massSend" resultMap="wxMassSendResult" columnPrefix="ms_" >
        </association>
    </resultMap>

    <resultMap id="wxMassSendResult" type="WxMassSend" >
        <id property="id" column="ms_id" />
        <result property="sysUnitId" column="sys_unit_id" />
        <result property="massId" column="massId" />
        <result property="receivers" column="receivers" />
        <result property="status" column="status" />
        <result property="msgId" column="msgId" />
        <result property="errCode" column="errCode" />
        <result property="errMsg" column="errMsg" />
        <result property="wxid" column="wxid" />
        <result property="opBy" column="opBy" />
        <result property="opAt" column="opAt" />
        <result property="delFlag" column="delFlag" />
    </resultMap>

    <select id="getWxMassandsend" resultMap="MassandsendResult" >
        select
            m.*,
            ms.id ms_id,
            ms.sys_unit_id ms_sys_unit_id,
            ms.massId ms_massId,
            ms.receivers ms_receivers,
            ms.status ms_status,
            ms.msgId ms_msgId,
            ms.errCode ms_errCode,
            ms.errMsg ms_errMsg,
            ms.wxid ms_wxid,
            ms.opBy ms_opBy,
            ms.wxid ms_wxid,
            ms.opAt ms_opAt,
            ms.delFlag ms_delFlag
        from wx_mass m,wx_mass_send ms
        where m.id=ms.massId and m.wxid=ms.wxid and m.wxid=#{1}
    </select>
</mapper>

参考：

关联的嵌套结果映射   https://mybatis.org/mybatis-3/zh/sqlmap-xml.html#Result_Maps