Hibernate里面的几个方法

1、save方法：

public void testSave() throws Exception {
        Session session = HibernateUtils.getInstance().getSession();
        session.beginTransaction();
        Teacher tac = new Teacher("哄哄",52);
        session.save(tac);
        session.getTransaction().commit();
        session.close();
    }

2、delete方法：

public void testDelete() throws Exception {
        Session session = HibernateUtils.getInstance().getSession();
        session.beginTransaction();
        Teacher tac = new Teacher(2L);
        session.delete(tac);
        session.getTransaction().commit();
        session.close();
    }

3、update方法：

public void testUpdate() throws Exception {
        Session session = HibernateUtils.getInstance().getSession();
        session.beginTransaction();
        Teacher tac = new Teacher(3L,"哄哄",52);
        session.update(tac);
        session.getTransaction().commit();
        session.close();
    }

4、list方法：

public void testList() throws Exception {
        Session session = HibernateUtils.getInstance().getSession();
        Query query = session.createQuery("select tec from Teacher tec");
        @SuppressWarnings("unchecked")
        List<Teacher> list = query.list();
        System.out.println(list);
        session.close();
    }

5、saveorupdate方法：

public void testSaveOrUpdate() throws Exception {
        /**
         * 利用saveOrUpdate添加对象，要使用的话，要么没有id，要么
         * 使用数据库中已有的id
         */
        Session session = HibernateUtils.getInstance().getSession();
        session.beginTransaction();
        
        /*Teacher tac = new Teacher("哈哈",21);
        session.saveOrUpdate(tac);*/
        Teacher tac = new Teacher(2l,"小小",21);
        session.saveOrUpdate(tac);
        
        session.getTransaction().commit();
        session.close();
    }

6、persist方法：

public void testPersist() throws Exception {
        //添加方法JPA规范里面的
        Session session = HibernateUtils.getInstance().getSession();
        session.beginTransaction();
        
        Teacher tac = new Teacher("大大",21);
        session.persist(tac);
        
        session.getTransaction().commit();
        session.close();
    }

7、merge方法：

public void testMerge() throws Exception {
        /**
         *    JPA规范里面的一个方法，相当与save
         *    1.如果里面没有对象里面没有id，相当于save方法；
         *    2.如果有id，但是数据库里面没有，相当于save方法，并且忽略对象里面的id
         *    3.如果有id，数据库里面也有，则就相当于update方法
         */
        Session session = HibernateUtils.getInstance().getSession();
        session.beginTransaction();
        
        //Teacher tac = new Teacher(20L,"啦啦啦",21);
        Teacher tac = new Teacher("啦啦啦",21);
        session.merge(tac);
        
        session.getTransaction().commit();
        session.close();
    }

8、get方法：

public void testGet() throws Exception {
        /**
         * 一级缓存：同时执行两个一模一样的操作，只打印一次数据库语句
         * Hibernate: select teacher0_.e_id as e1_0_0_,-
         * teacher0_.e_name as e2_0_0_, teacher0_.e_age as e3_0_0_ -
         * from t_teacher teacher0_ where teacher0_.e_id=?
         * Teacher [id=3, name=大大, age=21]
         * Teacher [id=3, name=大大, age=21]
         */
        Session session = HibernateUtils.getInstance().getSession();
        session.beginTransaction();
        
        Teacher tea = (Teacher) session.get(Teacher.class, 3L);
        System.out.println(tea);//一次操作
        Teacher tea1 = (Teacher) session.get(Teacher.class, 3L);
        System.out.println(tea1);//二次操作
        
        session.getTransaction().commit();
        session.close();
    }

9、load方法：

public void testLoad() throws Exception {
        Session session = HibernateUtils.getInstance().getSession();
        session.beginTransaction();
        /**
         * session.get在调用这个方法以后立马去数据库查询；
         * session.load在调用之后先不管用户的返回值，看下面的对象的非主键getter方法是否调用，
         * 如果调用，再去数据库查询，否则一直观望，直到session挂了，在使用load的时候一定要
         * 保证id在数据库中有对应的对象
         */
        /*Teacher tea = (Teacher) session.get(Teacher.class, 4L);
        System.out.println("~~~~~~~~~~~~~~~~~~~~");
        System.out.println(tea);*/
        /**控制台的输出结果：
         * Hibernate: select teacher0_.e_id as e1_0_0_, teacher0_.e_name as e2_0_0_, teacher0_.e_age as e3_0_0_ from t_teacher teacher0_ where teacher0_.e_id=?
         * ~~~~~~~~~~~~~~~~~~~~
         * Teacher [id=4, name=大大, age=21]
         */
        Teacher tea = (Teacher) session.load(Teacher.class, 4L);
        System.out.println("~~~~~~~~~~~~~~~~~~~~~");
        System.out.println(tea);
        /**控制台的输出结果：
         * ~~~~~~~~~~~~~~~~~~~~~
         * Hibernate: select teacher0_.e_id as e1_0_0_, teacher0_.e_name as e2_0_0_, teacher0_.e_age as e3_0_0_ from t_teacher teacher0_ where teacher0_.e_id=?
         * Teacher [id=4, name=大大, age=21]
         */
        session.getTransaction().commit();
        session.close();
    }