CREATE TABLE teacher(

    t_id INT PRIMARY KEY AUTO_INCREMENT,

    t_name VARCHAR(20)

);

CREATE TABLE class(

    c_id INT PRIMARY KEY AUTO_INCREMENT,

    c_name VARCHAR(20),

    teacher_id INT

);

ALTER TABLE class ADD CONSTRAINT fk_teacher_id FOREIGN KEY (teacher_id) REFERENCES teacher(t_id);    

INSERT INTO teacher(t_name) VALUES('LS1');

INSERT INTO teacher(t_name) VALUES('LS2');

INSERT INTO class(c_name, teacher_id) VALUES('bj_a', 1);

INSERT INTO class(c_name, teacher_id) VALUES('bj_b', 2);

public class Classes {

    private int id;

    private String name;

    private Teacher teacher;

}

public class Teacher {

    private int id;

    private String name;

}

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD  Config 3.0//EN"

"http://mybatis.org/dtd/mybatis-3-config.dtd">

<configuration>

    <properties resource="db.properties"/>

    <typeAliases>

        <typeAlias type="cn.bean.Classes" alias="Classes"/>

        <typeAlias type="cn.bean.Teacher" alias="Teacher"/>

    </typeAliases>

    <environments default="development">

        <environment id="development">

            <transactionManager type="JDBC" />

            <dataSource type="POOLED">

                <property name="driver" value="${driver}" />

                <property name="url" value="${url}" />

                <property name="username" value="${username}" />

                <property name="password" value="${password}" />

            </dataSource>

        </environment>

    </environments>

    <mappers>

        <mapper resource="cn/test5/ClassMapper.xml"/>

    </mappers>

</configuration>

driver=com.mysql.jdbc.Driver

url=jdbc:mysql://localhost:3306/mybatis

username=root

password=root

<?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="cn.test5.ClassMapper">

    <!-- 根据班级id查询班级信息(带老师的信息) -->

    <select id="getClass" parameterType="int" resultMap="classResultMap">

        SELECT * FROM class c ,teacher t WHERE c.c_id = t.t_id and c.c_id=#{id}

    </select>

    <resultMap type="Classes" id="classResultMap">

        <id property="id" column="c_id"/>

        <result property="name" column="c_name"/>

        <association property="teacher" javaType="Teacher">

            <id property="id" column="t_id"/>

            <result property="name" column="t_name"/>

        </association>

    </resultMap>

</mapper>

import java.io.InputStream;

import junit.framework.Test;

import org.apache.ibatis.session.SqlSessionFactory;

import org.apache.ibatis.session.SqlSessionFactoryBuilder;

public class MyBatisUtils {

    public static SqlSessionFactory getFactory(){

        String resource = "conf.xml";

        InputStream is = Test.class.getClassLoader().getResourceAsStream(resource);

        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(is);

        return factory;

    }

}

import org.apache.ibatis.session.SqlSession;

import org.apache.ibatis.session.SqlSessionFactory;

import org.junit.Test;

import cn.bean.Classes;

import cn.utils.MyBatisUtils;

public class Test5 {

    @Test

    public void selectTeacherByCid(){

        SqlSessionFactory factory = MyBatisUtils.getFactory();

        SqlSession session = factory.openSession(true);

        String statement = "cn.test5.ClassMapper.getClass";

        Classes c = session.selectOne(statement, 1);

        System.out.println(c);

    }

}