鉴别器

<!--鉴别器-->

<discrimimator>相当于if判断

<resultMap id="findas" type="com.qf.bean.Student">
      <id column="userid" property="userid"></id>
      <result column="username" property="username"></result>
      <result column="sex" property="sex"></result>
      <!--鉴别器-->
      <discriminator javaType="string" column="sex">
          <case value="男" resultMap="boyh"></case>
          <case value="女" resultMap="girlh"></case>
      </discriminator>
  </resultMap>

     <resultMap id="boyh" type="com.qf.bean.BoyHealth" extends="findas">
          <collection property="boyhealths"  select="findboyid" column="userid" ></collection>
     </resultMap>
     <resultMap id="girlh" type="com.qf.bean.GirlHealth"  extends="findas">
         <collection property="girlHealths" select="findgirkid" column="userid"></collection>
     </resultMap>

    <select id="findboyid" resultType="com.qf.bean.Boy">
        select * from boy where bid=#{id}
    </select>
    <select id="findgirkid" resultType="com.qf.bean.Gril">
        select * from girl where gid=#{id}
    </select>

    <select id="findallstudent" resultMap="findas">
        select * from student
    </select>