04_hibernate三种状态的讲解

import java.text.SimpleDateFormat;import org.hibernate.Session;import org.junit.Test;import com.wang.ceit.model.User;import com.wang.ceit.util.HibernateUtil;public class TestStatus {private static final SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");@Testpublic void testTransient() {Session session = null;try {session = HibernateUtil.openSession();session.beginTransaction();User u = new User();u.setBorn(sdf.parse("1976-2-3"));u.setUsername("zxl");u.setNickname("赵晓六");u.setPassword("123");//以上u就是Transient（瞬时状态），表示没有被session管理并且数据库中没有//执行save之后，被session所管理，而且，数据库中已经存在，此时就是Persistent状态session.save(u);session.getTransaction().commit();} catch (Exception e) {e.printStackTrace();if(session!=null) session.getTransaction().rollback();} finally {HibernateUtil.close(session);}}@Testpublic void testPersistent01() {Session session = null;try {session = HibernateUtil.openSession();session.beginTransaction();User u = new User();u.setBorn(sdf.parse("1976-2-3"));u.setUsername("zxq");u.setNickname("赵晓七");u.setPassword("123");//以上u就是Transient（瞬时状态），表示没有被session管理并且数据库中没有//执行save之后，被session所管理，而且，数据库中已经存在，此时就是Persistent状态session.save(u);//此时u是持久化状态，已经被session所管理，当在提交时，会把session中的对象和目前的对象进行比较//如果两个对象中的值不一致就会继续发出相应的sql语句u.setNickname("赵晓其");//此时会发出2条sql，一条用户做插入，一条用来做更新session.getTransaction().commit();} catch (Exception e) {e.printStackTrace();if(session!=null) session.getTransaction().rollback();} finally {HibernateUtil.close(session);}}@Testpublic void testPersistent02() {Session session = null;try {session = HibernateUtil.openSession();session.beginTransaction();User u = new User();u.setBorn(sdf.parse("1976-2-3"));u.setUsername("zxq");u.setNickname("赵晓八");u.setPassword("123");session.save(u);u.setPassword("222");//该条语句没有意义session.save(u);u.setNickname("赵晓吧");//没有意义session.update(u);u.setBorn(sdf.parse("1988-12-22"));//没有意义session.update(u);session.getTransaction().commit();} catch (Exception e) {e.printStackTrace();if(session!=null) session.getTransaction().rollback();} finally {HibernateUtil.close(session);}}@Testpublic void testPersistent03() {Session session = null;try {session = HibernateUtil.openSession();session.beginTransaction();User u = new User();u.setBorn(sdf.parse("1976-2-3"));u.setUsername("zxq");u.setNickname("赵晓九");u.setPassword("123");session.save(u);/* * 以下三条语句没有任何意义 */session.save(u);session.update(u);session.update(u);u.setUsername("zxj");session.getTransaction().commit();} catch (Exception e) {e.printStackTrace();if(session!=null) session.getTransaction().rollback();} finally {HibernateUtil.close(session);}}@Testpublic void testPersistent04() {Session session = null;try {session = HibernateUtil.openSession();session.beginTransaction();//此时u是PersistentUser u = (User)session.load(User.class, 10);//由于u这个对象和session中的对象不一致，所以会发出sql完成更新u.setUsername("aaa");session.getTransaction().commit();} catch (Exception e) {e.printStackTrace();if(session!=null) session.getTransaction().rollback();} finally {HibernateUtil.close(session);}}@Testpublic void testPersistent05() {Session session = null;try {session = HibernateUtil.openSession();session.beginTransaction();//此时u是PersistentUser u = (User)session.load(User.class, 10);session.getTransaction().commit();session.beginTransaction();u.setUsername("123");session.getTransaction().commit();} catch (Exception e) {e.printStackTrace();if(session!=null) session.getTransaction().rollback();} finally {HibernateUtil.close(session);}}@Testpublic void testPersistent06() {Session session = null;try {session = HibernateUtil.openSession();session.beginTransaction();//此时u是PersistentUser u = (User)session.load(User.class, 11);u.setUsername("123");//清空sessionsession.clear();session.getTransaction().commit();} catch (Exception e) {e.printStackTrace();if(session!=null) session.getTransaction().rollback();} finally {HibernateUtil.close(session);}}@Testpublic void testDetach01() {Session session = null;try {session = HibernateUtil.openSession();session.beginTransaction();User u = new User();u.setId(10);u.setNickname("abc");//当执行save的时候总是会添加一条数据，此时id就会根据Hibernate所定义的规则来生成session.save(u);session.getTransaction().commit();} catch (Exception e) {e.printStackTrace();if(session!=null) session.getTransaction().rollback();} finally {HibernateUtil.close(session);}}@Testpublic void testDetach02() {Session session = null;try {session = HibernateUtil.openSession();session.beginTransaction();User u = new User();u.setId(10);//完成update之后也会变成持久化状态session.update(u);u.setBorn(sdf.parse("1998-12-22"));u.setNickname("aaa");u.setUsername("111");//会发出一条sqlsession.update(u);session.getTransaction().commit();} catch (Exception e) {e.printStackTrace();if(session!=null) session.getTransaction().rollback();} finally {HibernateUtil.close(session);}}@Testpublic void testDetach03() {Session session = null;try {session = HibernateUtil.openSession();session.beginTransaction();User u = new User();u.setId(10);//完成update之后也会变成持久化状态session.update(u);u.setBorn(sdf.parse("1998-12-22"));u.setNickname("aaa");u.setUsername("111");//会抛出异常u.setId(333);//会发出一条sqlsession.getTransaction().commit();} catch (Exception e) {e.printStackTrace();if(session!=null) session.getTransaction().rollback();} finally {HibernateUtil.close(session);}}@Testpublic void testDetach04() {Session session = null;try {session = HibernateUtil.openSession();session.beginTransaction();User u = new User();u.setId(10);//现在u就是transient对象session.delete(u);//此时u已经是瞬时对象，不会被session和数据库所管理u.setNickname("abc");session.getTransaction().commit();} catch (Exception e) {e.printStackTrace();if(session!=null) session.getTransaction().rollback();} finally {HibernateUtil.close(session);}}@Testpublic void testDetach05() {Session session = null;try {session = HibernateUtil.openSession();session.beginTransaction();User u = new User();//u.setId(110);u.setNickname("abc");//如果u是离线状态就执行update操作，如果是瞬时状态就执行Save操作//但是注意：该方法并不常用session.saveOrUpdate(u);session.getTransaction().commit();} catch (Exception e) {e.printStackTrace();if(session!=null) session.getTransaction().rollback();} finally {HibernateUtil.close(session);}}@Testpublic void testDetach06() {Session session = null;try {session = HibernateUtil.openSession();session.beginTransaction();//u1已经是持久化状态User u1 = (User)session.load(User.class, 11);System.out.println(u1.getNickname());//u2是离线状态User u2 = new User();u2.setId(11);u2.setPassword("12223");//此时u2将会变成持久化状态，在session的缓存中就存在了两份同样的对象,在session中不能存在两份拷贝，否则会抛出异常//session.saveOrUpdate(u2);//merge方法会判断session中是否已经存在同一个对象，如果存在就将两个对象合并session.merge(u2);//最佳实践：merge一般不用session.getTransaction().commit();} catch (Exception e) {e.printStackTrace();if(session!=null) session.getTransaction().rollback();} finally {HibernateUtil.close(session);}}}