Mybatis多对一处理。 多对一：多个学生对应一个老师对于学生而言，关联 多个学生，关联一个老师【多对一】对于老师而言， 一个老师，有很多学生【一对多】数据库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, '庞老师'); 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=utf8; INSERT 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'); Student类 （省略了构造函数、Setter/Getter）public class Student { private int id; private String name; //学生需要关联一个老师 private Teacher teacher; } Teacher类 （省略了构造函数、Setter/Getter）public class Teacher { private int id; private String name; } 测试环境搭建新建实体类Teacher，Student建立Mapper接口建立Mapper.xml文件【在Resources目录下需要一级一级建立文件夹】在核心配置中绑定注册我们的Mapper接口或者文件测试查询是否能成功StudentMapper接口（interface）//查询所有学生信息，以及对于的老师的信息 public List<Student> getStudent(); // public List<Student> getStudent2(); 按照查询嵌套处理思路：1.查询所有的学生信息2.根据查询出来的学生的tid，寻找对应的老师 子查询<select id="getStudent" resultMap="StudentTeacher"> select * from student </select> <resultMap id="StudentTeacher" type="Student"> <result property="id" column="id"/> <result property="name" column="name"/> <!--复杂的属性 对象：association 集合：collection --> <association property="teacher" column="tid" javaType="Teacher" select="getTeacher"/> </resultMap> <select id="getTeacher" resultType="Teacher"> select * from teacher where id = #{id} </select> 按照结果嵌套处理<!--按照结果处理--> <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> <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> 测试代码@Test public void getStudent(){ SqlSession sqlSession = MybatisUtils.getSqlSession(); StudentMapper mapper = sqlSession.getMapper(StudentMapper.class); List<Student> studentList = mapper.getStudent(); for (Student student : studentList) { System.out.println(student); } sqlSession.close(); } @Test public void getStudent2(){ SqlSession sqlSession = MybatisUtils.getSqlSession(); StudentMapper mapper = sqlSession.getMapper(StudentMapper.class); List<Student> studentList = mapper.getStudent2(); for (Student student : studentList) { System.out.println(student); } sqlSession.close(); } 多对一掌握了？那么可以下一课了，来看看一对多吧！点击访问