Hibernate-hibernate一級緩存.doc

此文檔收集于網(wǎng)絡，如有侵權，請聯(lián)系網(wǎng)站刪除hibernate一級緩存一級緩存很短和session的生命周期一致，一級緩存也叫session級的緩存或事務級緩存那些方法支持一級緩存：* get()* load()* iterate()（查詢實體對象）如何管理一級緩存：* session.clear(),session.evict()如何避免一次性大量的實體數(shù)據(jù)入庫導致內(nèi)存溢出* 先flush，再clear如果數(shù)據(jù)量特別大，考慮采用jdbc實現(xiàn)，如果jdbc也不能滿足要求可以考慮采用數(shù)據(jù)本身的特定導入工具Student.javaprivate int id;private String name;private Classes classes;Classes.javaprivate int id;private String name;private Set students; 初始數(shù)據(jù)for(int i=0; i10; i+)Classes classes = new Classes();classes.setName(班級_+i);session.save(classes);for(int j=0; j10; j+)Student student = new Student();student.setName(班級+i+的學生+j);/在內(nèi)存中建立由student指向classes的引用student.setClasses(classes);session.save(student); /* * 在同一個session中發(fā)出兩次load查詢 */public void testCache1() Session session = null;try session = HibernateUtils.getSession();session.beginTransaction();Student student = (Student)session.load(Student.class, 1);System.out.println(= + student.getName();/*在第二次發(fā)出相同操作的時候，第二次不會發(fā)出sql，因為load使用緩存加載數(shù)據(jù)*/student = (Student)session.load(Student.class, 1);System.out.println(= + student.getName();session.getTransaction().commit();catch(Exception e) e.printStackTrace();session.getTransaction().rollback();finally HibernateUtils.closeSession(session);/* * 在同一個session中發(fā)出兩次get查詢 */public void testCache2() Session session = null;try session = HibernateUtils.getSession();session.beginTransaction();Student student = (Student)session.get(Student.class, 1);System.out.println(= + student.getName();/*在第二次發(fā)出相同操作的時候，第二次不會發(fā)出sql，因為get使用緩存加載數(shù)據(jù)*/student = (Student)session.get(Student.class, 1);System.out.println(= + student.getName();session.getTransaction().commit();catch(Exception e) e.printStackTrace();session.getTransaction().rollback();finally HibernateUtils.closeSession(session);/* * 在同一個session中發(fā)出兩次iterate查詢實體對象 */public void testCache3() Session session = null;try session = HibernateUtils.getSession();session.beginTransaction();Student student = (Student)session.createQuery(from Student s where s.id=1).iterate().next();System.out.println(= + student.getName();/會發(fā)出查詢id的sql，不會發(fā)出查詢實體對象的sql，因為iterate使用緩存student = (Student)session.createQuery(from Student s where s.id=1).iterate().next();System.out.println(= + student.getName();session.getTransaction().commit();catch(Exception e) e.printStackTrace();session.getTransaction().rollback();finally HibernateUtils.closeSession(session);/* * 在同一個session中發(fā)出兩次iterate查詢實體對象 */public void testCache4() Session session = null;try session = HibernateUtils.getSession();session.beginTransaction();String name = (String)session.createQuery(select from Student s where s.id=1).iterate().next();System.out.println(= + name);/iterate查詢普通屬性，一級緩存不會緩存，所以發(fā)出sql/一級緩存是緩存的實體對象name = (String)session.createQuery(select from Student s where s.id=1).iterate().next();System.out.println(= + name);session.getTransaction().commit();catch(Exception e) e.printStackTrace();session.getTransaction().rollback();finally HibernateUtils.closeSession(session);/* * 開啟兩個session中發(fā)出load查詢 */public void testCache5() Session session = null;try session = HibernateUtils.getSession();session.beginTransaction();Student student = (Student)session.load(Student.class, 1);System.out.println(= + student.getName();session.getTransaction().commit();catch(Exception e) e.printStackTrace();session.getTransaction().rollback();finally HibernateUtils.closeSession(session);try session = HibernateUtils.getSession();session.beginTransaction();/會發(fā)出查詢語句，session間不能共享一級緩存的數(shù)據(jù)/因為它會伴隨session的生命周期存在和消亡Student student = (Student)session.load(Student.class, 1);System.out.println(= + student.getName();session.getTransaction().commit();catch(Exception e) e.printStackTrace();session.getTransaction().rollback();finally HibernateUtils.closeSession(session);/* * 在同一個session中先save，在發(fā)出load查詢save過的數(shù)據(jù) */public void testCache6() Session session = null;try session = HibernateUtils.getSession();session.beginTransaction();Student stu = new Student();stu.setName(王五);Serializable id = session.save(stu);/不會發(fā)出sql，因為save是使用緩存的Student student = (Student)session.load(Student.class, id);System.out.println(= + student.getName();session.getTransaction().commit();catch(Exception e) e.printStackTrace();session.getTransaction().rollback();finally HibernateUtils.closeSession(session);/* * 向數(shù)據(jù)庫中批量加入1000條數(shù)據(jù) */public void testCache7() Session session = null;try session = HibernateUtils.getSession();session.beginTransaction();for (int i=0; i1000; i+) Student student = new Student();student.setName(s_ + i);session.save(student);/每20條數(shù)據(jù)就強制sess