package com.dy.entity;public class Course {private int id;private String name; private int deleteFlag;public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getDeleteFlag() {return deleteFlag;}public void setDeleteFlag(int deleteFlag) {this.deleteFlag = deleteFlag;}}

package com.dy.entity;import java.util.List;public class Student {private int id;private String idCard;private String name;private List<Course> courseList;private int deleteFlag;public Student(int id, String idCard, String name, List<Course> courseList, int deleteFlag) {this.id = id;this.idCard = idCard;this.name = name;this.courseList = courseList;this.deleteFlag = deleteFlag;}public int getId() {return id;}public void setId(int id) {this.id = id;}public String getIdCard() {return idCard;}public void setIdCard(String idCard) {this.idCard = idCard;}public String getName() {return name;}public void setName(String name) {this.name = name;}public List<Course> getCourseList() {return courseList;}public void setCourseList(List<Course> courseList) {this.courseList = courseList;}public int getDeleteFlag() {return deleteFlag;}public void setDeleteFlag(int deleteFlag) {this.deleteFlag = deleteFlag;}
}

package com.dy.dao;import com.dy.entity.Course;public interface CourseDao {public Course findCourseById(int courseId);}

package com.dy.dao;import com.dy.entity.Student;public interface StudentDao {public Student findStudentById(String idCard);
}

package com.dy.dao;import java.io.IOException;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 org.junit.Test;import com.dy.entity.Course;public class CourseDaoTest {@Testpublic void findCourseById() {SqlSessionFactory sqlSessionFactory = getSessionFactory();SqlSession sqlSession = sqlSessionFactory.openSession(); CourseDao courseDao = sqlSession.getMapper(CourseDao.class);Course course = courseDao.findCourseById(1);}//Mybatis 通过SqlSessionFactory获取SqlSession, 然后才能通过SqlSession与数据库进行交互private static SqlSessionFactory getSessionFactory() {  SqlSessionFactory sessionFactory = null;  String resource = "mybatis-conf.xml";  try {  sessionFactory = new SqlSessionFactoryBuilder().build(Resources  .getResourceAsReader(resource));} catch (IOException e) {  e.printStackTrace();  }  return sessionFactory;  }
}

<mapper namespace="com.dy.dao.StudentDao"><!-- 这儿定义一个resultMap --><resultMap type="student" id="studentMap"><!-- 数据库中主键是id, 但是我这儿却是指定idCard为主键，为什么？ 刚刚讲了，id用来表示唯一性， 我们可以认为只要idCard一样，那么他就是同一个学生。如果此处用数据库中id， 那么mybatis将会认为数据库中每条记录都是一个student, 这显然不符合逻辑--><id property="idCard" column="stu_id_card"/><result property="id" column="stu_id"/><result property="name" column="stu_name"/><result property="deleteFlag" column="stu_delete_flg"/><!-- 这儿就是实现一对多的关键。 在Student中，courseList为List<Course>, 因此，ofType也应该与之对应（当然，我用了别名，不然要蛋疼的写全名了）。collection的子标签是在指定Course的映射关系（由于Course的javabean的属性名与数据库的列名不一致）--><collection property="courseList" column="stu_course_id" ofType="Course"><id property="id" column="course_id"/><result property="name" column="course_name"/><result property="deleteFlag" column="course_delete_flg"/></collection></resultMap><!-- 这儿将返回类型设置成了上面指定的studentMap --><select id="findStudentById" resultMap="studentMap">SELECT s.*, c.* FROM t_student s LEFT JOIN t_course c ON s.stu_course_id=c.course_id WHERE s.stu_id_card=#{idCard}</select></mapper>

package com.dy.dao;import java.io.IOException;
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 org.junit.Test;import com.dy.entity.Course;
import com.dy.entity.Student;public class StudentDaoTest {@Testpublic void findCourseById() {SqlSessionFactory sqlSessionFactory = getSessionFactory();SqlSession sqlSession = sqlSessionFactory.openSession(); StudentDao studentDao = sqlSession.getMapper(StudentDao.class);Student student = studentDao.findStudentById("20140101");List<Course> courseList = student.getCourseList();for (Course course: courseList) {System.out.println(course.getId() + "   " + course.getName());}}//Mybatis 通过SqlSessionFactory获取SqlSession, 然后才能通过SqlSession与数据库进行交互private static SqlSessionFactory getSessionFactory() {  SqlSessionFactory sessionFactory = null;  String resource = "mybatis-conf.xml";  try {  sessionFactory = new SqlSessionFactoryBuilder().build(Resources  .getResourceAsReader(resource));} catch (IOException e) {  e.printStackTrace();  }  return sessionFactory;  }
}