Hibernate-一对多双向.doc

此文档收集于网络，如有侵权，请联系网站删除Classes.javaprivate int id;private String name;private Set students; Student.javaprivate int id;private String name;private Classes classes;public class One2ManyTest extends TestCase public void testSave1() Session session = null;try session = HibernateUtils.getSession();session.beginTransaction();Student student1 = new Student();student1.setName(10);session.save(student1);Student student2 = new Student();student2.setName(祖儿);session.save(student2);Set students = new HashSet();students.add(student1);students.add(student2);Classes classes = new Classes();classes.setName(2012A);classes.setStudents(students);/可以正确保存session.save(classes);session.getTransaction().commit();catch(Exception e) e.printStackTrace();session.getTransaction().rollback();finally HibernateUtils.closeSession(session);public void testSave2() Session session = null;try session = HibernateUtils.getSession();session.beginTransaction();Classes classes = new Classes();classes.setName(2012A);session.save(classes);Student student1 = new Student();student1.setName(飞飞);student1.setClasses(classes);session.save(student1);Student student2 = new Student();student2.setName(菲菲);student2.setClasses(classes);session.save(student2);session.getTransaction().commit();catch(Exception e) e.printStackTrace();session.getTransaction().rollback();finally HibernateUtils.closeSession(session);public void testSave3() Session session = null;try session = HibernateUtils.getSession();session.beginTransaction();Classes classes = new Classes();classes.setName(2012A);Student student1 = new Student();student1.setName(飞飞);student1.setClasses(classes);Student student2 = new Student();student2.setName(菲菲);student2.setClasses(classes);Set students = new HashSet();students.add(student1);students.add(student2);classes.setStudents(students);/可以正确保存session.save(classes);session.getTransaction().commit();catch(Exception e) e.printStackTrace();session.getTransaction().rollback();finally HibernateUtils.closeSession(session);public void testLoad1() Session session = null;try session = HibernateUtils.getSession();session.beginTransaction();Classes classes = (Classes)session.load(Classes.class, 1);System.out.println(= + classes.getName();Set students = classes.getStudents();for (Iterator iter=students.iterator(); iter.hasNext();) Student student = (Student)iter.next();System.out.println(= + student.getName();session.getTransaction().commit();catch(Exception e) e.printStackTrace();session.getTransaction().rollback();finally HibernateUtils.closeSession(session);public void testLoad2() Session session = null;try session = HibernateUtils.getSession();session.beginTransaction();Student student = (Student)session.load(Student.class, 1);System.out.println(= + student.getName();System.out.println(= + student.getClasses().getName();session.getTransaction().commit();catch(Exception e) e.printStackTrace();session.getTransaction().rollback();finally HibernateUtils.closeSession(session);hihernate一对多关联映射（双向ClassesStudent）一对多双向关联映射：* 在一一端的集合上使用，在对方表中加入一个外键指向一一端* 在多一端采用注意：标签指定的外键字段必须和指定的外键字段一致，否则引用字段的错误如果在”一“一端维护一对多关联关系，hibernate会发出多余的udpate语句，所以我们一般在多的一端来维护关联关系关于inverse属性：inverse主要用在一对多和多对多双向关联上，inverse可以被设置到集合标签上，默认inverse为false，所以我们可以从”一“一端和”多“一端维护关联关系，如果设置成inverse为true，则我们只能从多一端来维护关联关系注意：inverse属性，只影响数据的存储，也就是持久化在设置了inverse为true 以后，数据时可以insert 进入对应的表，但是，hibernate不会再发出update 更新操作，因此插入数据库中的数据无效，对应的关系没有办法维护，