mybatis 一对多查询

Student 实体类

package com.tanghong.pojo;

import lombok.Data;

@Data
public class Student {
    private  int id;
    private  String name;

    private Teacher teacher;
}

package com.tanghong.dao;

import com.tanghong.pojo.Student;

import java.util.List;

public interface StudentMapper {

    List<Student>  getStudent();
    
    List<Student>  getStudent2();
}

Mapper.XML  

 子查询

<select id="getStudent"  resultMap="StudentTeacher">
    select * from student
</select>
<resultMap id="StudentTeacher" type="com.tanghong.pojo.Student">
    <result property="id" column="id"/>
    <result property="name" column="name"/>
    <association property="teacher" column="tid" javaType="com.tanghong.pojo.Teacher" select="getTeacher"/>
</resultMap>
<select id="getTeacher" resultType="com.tanghong.pojo.Teacher">
    select * from teacher where id= #{id}
</select>

联表查询

<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>
　　

<!--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！
    集合中的泛型信息 我们使用ofType获取
-->

<resultMap id="StudentTeacher2" type="com.tanghong.pojo.Student">
    <result property="id" column="sid"/>
    <result property="name" column="sname"/>
    <association property="teacher" javaType="com.tanghong.pojo.Teacher">
        <result property="name" column="tname"/>
    </association>
</resultMap>