关于mybatis:练习mybatis多对一关系

对于老师而言，汇合，一个老师有很多学生【一对多】

SQL：

CREATE TABLE `teacher` (`id` INT(10) NOT NULL,
`name` VARCHAR(30) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=INNODB DEFAULT CHARSET=utf8

INSERT INTO teacher(`id`, `name`) VALUES (1, 计算机老师); 

CREATE TABLE `student` (`id` INT(10) NOT NULL,
`name` VARCHAR(30) DEFAULT NULL,
`tid` INT(10) DEFAULT NULL,
PRIMARY KEY (`id`),
KEY `fktid` (`tid`),
CONSTRAINT `fktid` FOREIGN KEY (`tid`) REFERENCES `teacher` (`id`)
) ENGINE=INNODB DEFAULT CHARSET=utf8INSERT INTO `student` (`id`, `name`, `tid`) VALUES (1, 小明, 1); 
INSERT INTO `student` (`id`, `name`, `tid`) VALUES (2, 小红, 1); 
INSERT INTO `student` (`id`, `name`, `tid`) VALUES (3, 小张, 1); 
INSERT INTO `student` (`id`, `name`, `tid`) VALUES (4, 小李, 1); 
INSERT INTO `student` (`id`, `name`, `tid`) VALUES (5, 小王, 1);

测试环境搭建
1. 导入 lombok
2. 新建实体类 Teacher，Student

@Data
public class Student{
  private int id;
  private String name;
  // 学生须要关联一个老师！private Teacher teacher;
}

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

}

3. 建设 Dao 接口 TeacherDao，StudentDao

public interface TeacherDao{@Select("select * from teacher where id=#{tid}")
  Teacher getTeacher(@Param("tid") int id);
}

public interface StudentDao{}

4. 建设 Mapper.xml 文件
在 resources 目录创立 com.jialidun.dao 包

<!DOCTYPE mapper
  PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
  "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.jialidun.dao.TeacherDao">
  
</mapper>

<!DOCTYPE mapper
  PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
  "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.jialidun.dao.StudentDao">
  
</mapper>

5. 在外围配置文件中绑定注册咱们的 Mapper 接口或者文件！

<mappers>
  <mapper resource="com/jialidun/dao/*.xml"/>
  <mapper class="com.jialidun.dao.*"/>
</mappers>

6. 测试查问胜利

public class TestDemo{
  @Test
  public void test01(){SqlSession sqlSession = MybatisUtils.getSqlSession();
      TeacherDap mapper = sqlSession.getBean(TeacherDao.class);
      Teacher teacher = mapper.getTeacher(1);
      System.out.println(teacher);
      sqlSession.close();}


}