mybatis总结

结果集 一对多的结果映射

<?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.mybatis.study.dao.TeacherMapper">
    <!--按结果嵌套查询-->
    <select id="getTeacher" resultMap="TeacherStudent">
        select s.id sid,s.name sname,t.name tname,t.id tid from student s ,teacher t where s.tid=t.id and t.id=#{tid}
    </select>
    <resultMap id="TeacherStudent" type="teacher">
        <result property="id" column="tid"/>
        <result property="name" column="tname"/>
        <!--复杂的属性，我们需要单独处理，对象：association 集合：collection
            javaType:指定属性的类型
            集合中的泛型我们使用ofType获取
        -->
        <collection property="students" ofType="Student">
            <result property="id" column="sid"/>
            <result property="name" column="sname"/>
            <result property="tid" column="tid"/>
        </collection>
    </resultMap>
    <!--=================================================================-->
    <select id="getTeacher2" resultMap="TeacherStudent2">
        select * from mybatis.teacher where id=#{tid}
    </select>
    <resultMap id="TeacherStudent2" type="Teacher">
        <result property="id" column="id"/>
        <collection property="students" javaType="ArrayList" ofType="Student" select="getStudentByTeacherId" column="id"/>
    </resultMap>
    <select id="getStudentByTeacherId" resultType="Student">
        select * from mybatis.student where tid=#{tid}
    </select>

</mapper>

多对一的结果映射配置

<?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.mybatis.study.dao.StudentMapper">
    <!--
    思路：1、查询所有的学生信息
         2、根据查询出来的学生tid,寻找对应的老师！ 子查询。
    -->
    <resultMap id="StudentTeacher" type="student">
        <result column="id" property="id"/>
        <result column="name" property="name"/>
        <!--复杂的属性需要单独处理
            对象：association
            集合：collection
        -->
        <association property="teacher" column="tid" javaType="Teacher" select="getTeacher"/>
    </resultMap>
    <select id="getStudent" resultMap="StudentTeacher">
        select * from student
    </select>
    <select id="getTeacher" resultType="Teacher">
        select * from teacher where id=#{id}
    </select>
    <!--======================================================-->
    <!--按照结果嵌套处理-->
    <resultMap id="StudentTeacher2" type="student">
        <result property="id" column="sid"/>
        <result property="name" column="sname"/>
        <association property="teacher" javaType="Teacher">
            <result property="name" column="tname"/>
        </association>
    </resultMap>
    <select id="getStudent2" resultMap="StudentTeacher2">
        select s.id sid,s.name sname,t.name tname from student s ,teacher t where s.tid=t.id;
    </select>

</mapper>