-- Table structure for `t_student`

-- ----------------------------

DROP TABLE IF EXISTS `t_student`;

CREATE TABLE `t_student` (

  `id` int(11) NOT NULL AUTO_INCREMENT,

  `name` varchar(18) NOT NULL,

  `sex` varchar(3) NOT NULL,

  `age` int(11) NOT NULL,

  `cid` int(11) NOT NULL,

  PRIMARY KEY (`id`),

  KEY `cid` (`cid`),

  CONSTRAINT `cid` FOREIGN KEY (`cid`) REFERENCES `t_clazz` (`id`)

) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8;

-- ----------------------------

-- Records of t_student

-- ----------------------------

INSERT INTO `t_student` VALUES ('', '张三', '男', '', '');

INSERT INTO `t_student` VALUES ('', '李四', '男', '', '');

INSERT INTO `t_student` VALUES ('', '小红', '女', '', '');

-- ----------------------------

-- Table structure for `t_clazz`

-- ----------------------------

DROP TABLE IF EXISTS `t_clazz`;

CREATE TABLE `t_clazz` (

  `id` int(11) NOT NULL,

  `code` varchar(18) NOT NULL,

  PRIMARY KEY (`id`)

) ENGINE=InnoDB DEFAULT CHARSET=utf8;

-- ----------------------------

-- Records of t_clazz

-- ----------------------------

INSERT INTO `t_clazz` VALUES ('', '一班');

INSERT INTO `t_clazz` VALUES ('', '二班');

public class Student {

    private Integer id;

    private String name;

    private String sex;

    private Integer age;

    //关联的clazz对象

    private Clazz clazz;

        //省略get、set、toString方法

public class Clazz {

    private Integer id;

    private String code;

    //省略get、set、toString方法

<?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>

     <!-- 引入 外部db.properties文件-->

     <properties resource="db.properties"/>

     <!-- 指定 MyBatis 所用日志的具体实现-->

     <settings>

         <setting name="logImpl" value="log4j"/>

     </settings>

     <!-- 环境配置 -->

     <environments default="mysql">

         <environment id="mysql">

             <!-- 指定事务类型 -->

             <transactionManager type="JDBC"/>

                 <!--  dataSource指数据源配置，POOLED是JDBC连接对象的数据源连接池的实现。 -->

             <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>

     <!-- SQL映射文件位置 -->

     <mappers>

         <mapper resource="com/dj/mapper/StudentMapper.xml"/>

     </mappers>

 </configuration>

<?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">

<!-- namespace指用户自定义的命名空间 -->

<mapper namespace="com.dj.mapper.StudentMapper">

    <!-- 映射学生对象的resultMap -->

    <resultMap type="com.dj.domain.Student" id="studentResultMap">

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

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

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

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

        <!-- 关联映射

            property：表示返回类型student的属性名 clazz

            column：表示数据库的列名

            javaType：表示property属性对应的类型名称

            select：表示执行一条查询语句，将查询到的结果封装到property所代表的类型对象中。

         -->

        <association property="clazz" column="cid"

                javaType="com.dj.domain.Clazz" select="selectClazzById"/>

    </resultMap>

    <select id="selectClazzById" resultType="com.dj.domain.Clazz">

        select * from t_clazz where id=#{id}

    </select>

    <select id="selectStudent" resultMap="studentResultMap">

        select * from t_student

    </select>

</mapper>

package com.dj.test;

import java.io.IOException;

import java.io.InputStream;

import java.util.Iterator;

import java.util.List;

import org.apache.ibatis.io.Resources;

import org.apache.ibatis.session.SqlSession;

import org.apache.ibatis.session.SqlSessionFactory;

import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import com.dj.domain.Student;

public class StudentTest {

    public static void main(String[] args) throws IOException {

        InputStream inputStream = Resources.getResourceAsStream("mybatis-config.xml");

        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        SqlSession sqlSession = sqlSessionFactory.openSession();

        List<Student> list  = sqlSession.selectList("com.dj.mapper.StudentMapper.selectStudent");

        for (Student student : list) {

            System.out.println(student);

        }

        sqlSession.commit();

        sqlSession.close();

    }

}