Hibernate实验二.doc

Hibernate实验二实验内容：1. 双向多对多关联映射2. Hibernate检索方式实验目的：1. 掌握多对多关联关系的配置2. 掌握cascade、inverse属性的使用3. 掌握HQL查询的使用步骤4. 掌握QBC查询的使用步骤一、 双向多对多关联映射以学生课程表为例，一个学生可以选修多门课程，一门课程也可以被多位学生选修。1. 建立数据库表学生表：create table student( sid int not null auto_increment primary key, sname varchar ( 16 ), sage varchar ( 16 );课程表：create table course( cid int not null auto_increment primary key, cname varchar ( 16 );关联表：create table student_course_link( sid int not null, cid int not null, primary key (sid,cid), foreign key (sid) references student (sid), foreign key (cid) references course (cid);2. 创建Java项目mtm，并添加Hibernate包创建many.to.many.bean包，产生的实体类和映射文件将放到此包下。3. 使用Hibernate逆向工程自动产生实体类和映射文件利用上次实验的方法，找到数据库下的表。使用Hibernate逆向工程产生实体类和映射文件。请选择“many-to-many”。选择双向多对多，出现三个表。产生的实体类和映射文件如下：学生类：public class Student implements java.io.Serializable / Fieldsprivate Integer sid;private String sname;private String sage;private Set courses = new HashSet(0);/省略setter和getter课程类：public class Course implements java.io.Serializable / Fieldsprivate Integer cid;private String cname;private Set students = new HashSet(0);/省略setter和getterStudent.hbm.xml映射文件 Course.hbm.xml映射文件 4. 编码测试，插入一组数据package many.to.many.test;import java.util.HashSet;import java.util.Set;import many.to.many.bean.Course;import many.to.many.bean.Student;import many.to.many.sf.HibernateSessionFactory;import org.hibernate.Session;import org.hibernate.Transaction;public class Test public static void main(String args) /学生对象Student s1=new Student();s1.setSname(Tom);s1.setSage(21);Student s2=new Student();s2.setSname(Jerry);s2.setSage(20);/课程对象Course c1=new Course();c1.setCname(C+);Course c2=new Course();c2.setCname(Java);Course c3=new Course();c3.setCname(C#);Set students=new HashSet();students.add(s1);students.add(s2);Set courses=new HashSet();courses.add(c1);courses.add(c2);courses.add(c3);/建立双向关联s1.setCourses(courses);s2.setCourses(courses);c1.setStudents(students);c2.setStudents(students);c3.setStudents(students);Session session=HibernateSessionFactory.getSession();Transaction tx=session.beginTransaction();/请将Student.hbm.xml中的set标签的cascade设置为true，这样保存Student对象的时候会级联保存Course，/否则在向关联表插入数据的时候，由于找不到参照的Course数据会报异常/Exception in thread main org.hibernate.TransientObjectException: /object references an unsaved transient instance /- save the transient instance before flushing: many.to.many.bean.Coursesession.save(s1);session.save(s2);mit();HibernateSessionFactory.closeSession();成功插入：二、 Hibernate检索在上面实验的数据基础之上，学习HQL与QBC检索的使用步骤。1.HQL：查询姓名以“T”开头的学生，所选择的课程package many.to.many.test;import java.util.Iterator;import java.util.List;import java.util.Set;import many.to.many.bean.Course;import many.to.many.bean.Student;import many.to.many.sf.HibernateSessionFactory;import org.hibernate.Query;import org.hibernate.Session;public class Test2 public static void main(String args) String queryString=from Student s where s.sname like T%;Session s=HibernateSessionFactory.getSession();Query q=s.createQuery(queryString);List l=q.list();Iterator i=l.iterator();while (i.hasNext() Student student = (Student) i.next();Set courses = student.getCourses();Iterator i2=courses.iterator();while (i2.hasNext() Course c = (Course) i2.next();System.out.println(student.getSname()+ +c.getCname();2.QBC：查询姓名以“T”开头的学生，所选择的课程package many.to.many.test;import java.util.Iterator;import java.util.List;import java.util.Set;import many.to.many.bean.Course;import many.to.many.bean.Student;import many.to.many.sf.HibernateSessionFactory;import org.hibernate.Criteria;import org.hibernate.Session;import org.hibernate.criterion.Restrictions;public class Test3 public static void main(String args) Session s=HibernateSessionFactory.getSession();Criteria criteria=s.createCriteria(Student.class);criteria.add(Restrictions.like(sname, T%);List l=criteria.list();Iterator i=l.iterator();while (i.hasNext() Stude