Mybatis结果集映射一对多简单入门教程

 DROP TABLE IF EXISTS `student_2`; CREATE TABLE `student_2`  ( `id` int(10) NOT NULL, `name` varchar(30) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL, `tid` int(10) NULL DEFAULT NULL, PRIMARY KEY (`id`) USING BTREE, INDEX `fktid`(`tid`) USING BTREE, CONSTRAINT `fktid` FOREIGN KEY (`tid`) REFERENCES `teacher` (`id`) ON DELETE RESTRICT ON UPDATE RESTRICT ) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic; INSERT INTO `student_2` VALUES (1, '小明', 1); INSERT INTO `student_2` VALUES (2, '邱ss', 2); INSERT INTO `student_2` VALUES (3, '邱大哥', 3); INSERT INTO `student_2` VALUES (4, '杨大哥', 1); INSERT INTO `student_2` VALUES (5, '杨ss', 2);

 DROP TABLE IF EXISTS `teacher`; CREATE TABLE `teacher`  ( `id` int(10) NOT NULL AUTO_INCREMENT, `name` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL, PRIMARY KEY (`id`) USING BTREE ) ENGINE = InnoDB AUTO_INCREMENT = 4 CHARACTER SET = latin1 COLLATE = latin1_swedish_ci ROW_FORMAT = Dynamic; -- ---------------------------- -- Records of teacher -- ---------------------------- INSERT INTO `teacher` VALUES (1, '小王老师'); INSERT INTO `teacher` VALUES (2, '小李老师'); INSERT INTO `teacher` VALUES (3, '小黑老师');

   mysqlmysql-connector-java5.1.48 org.projectlomboklombok1.18.20 org.mybatismybatis3.5.6 junitjunit4.11test

 jdbc.driver=com.mysql.jdbc.Driver jdbc.url=jdbc:mysql://localhost:3306/ssm-study?useSSL=false jdbc.username=root jdbc.password=123456

 /** * @Author: crush * @Date: 2021-06-17 18:23 * version 1.0 */ public class Student { /** * 学生id */ private Integer id; /** * xueshneg xingming */ private String name; /** * 老师id */ private Integer tid; }

 /** * @Author: crush * @Date: 2021-06-17 18:23 * version 1.0 */ public class Teacher { /** * 老师id */ private Integer id; /** * 老师的姓名 */ private String name; /** * 每个老师是不是有很多学生 */ private List students; }

 /** * @author crush */ public class MybatisUtil { private static SqlSessionFactory sqlSessionFactory; static { try { String resource="mybatis-config.xml"; InputStream inputStream= Resources.getResourceAsStream(resource); sqlSessionFactory=new SqlSessionFactoryBuilder().build(inputStream); } catch (IOException e) { e.printStackTrace(); } } public static SqlSession getSession(){ return sqlSessionFactory.openSession(true); } }

 import com.crush.pojo.Teacher; import org.apache.ibatis.annotations.Param; import java.util.List; public interface TeacherMapper { // 获取老师 List getTeacher(); //获取指定老师下的所有学生及老师的信息 Teacher getTeacher2(@Param("tid") Integer id); //获取指定老师下的所有学生及老师的信息 Teacher getTeacher3(@Param("tid") Integer id); }

    select * from teacher  select s.id sid,s.name sname,t.name tname, t.id tid from student_2 s,teacher t where s.tid=t.id and t.id=#{tid}    select * from teacher where id=#{tid}   select  * from  student_2 where tid=#{tid} 

 /** * @Author: crush * @Date: 2021-06-17 18:22 * version 1.0 */ public class MyTest { @Test public void getTeacher(){ SqlSession session = MybatisUtil.getSession(); TeacherMapper mapper = session.getMapper(TeacherMapper.class); List teacher = mapper.getTeacher(); System.out.println(teacher); session.close(); } @Test public  void getTeacher2(){ SqlSession session = MybatisUtil.getSession(); TeacherMapper mapper = session.getMapper(TeacherMapper.class); Teacher teacher2 = mapper.getTeacher2(1); System.out.println(teacher2); session.close(); } @Test public  void getTeacher3(){ SqlSession session = MybatisUtil.getSession(); TeacherMapper mapper = session.getMapper(TeacherMapper.class); Teacher teacher2 = mapper.getTeacher3(1); System.out.println(teacher2); session.close(); } }