Hibernate SessionFactory and Session

1. Hibernate 的主类是Session类，它提供查找，保存和删除映射对象的方法,必须来建立一个SessionFactory，来得到Session

SessionFactory 有三个重要的属性， datasource,mappingLocation,hibernateProperties

   <bena id="hibernateSessionFactory">
       <property name="dataSource" ref="dataSource"/>
       <property name="mappingLocations">
            <list>
                 <value>classpath*:/com/test/*.hbm.xml</value>
            </list>
       </property>
       <property name="hibernateProperties">
                 ......
       </property>
   </bean>

2. 直接使用Hibernate SessionFactory and Session

   ApplicationContext ac=new ClassPathXmlApplicationContext("application.xml");
   SessionFactory sessionFactory=(SessionFactory)ac.getBean("hibernateSessionFactory");
   Session session=sessionFactory.openSession();
   // do your work
   session.close();

3. 使用Hibernate session 应该从调用beginTransaction 开始， 到调用Transaction.commit()方法结束，如果抛出异常，我们可以回滚事务

   ApplicationContext ac=new ClassPathXmlApplicationContext("application.xml");
   SessionFactory sessionFactory=(SessionFactory)ac.getBean("hibernateSessionFactory");
   Session  session=null;
   Transaction transaction=null;
   try{
         session=sessionFactory.openSession();
         transaction=session.beginTransaction();

         // do your work
         tramsactopm.commit();
   }catch(Exception e){
         if(transaction!=null)transaction.rollback();
         throw e;
   }finally{
         if(session!=null) session.close();
   }

4. 两种得到Spring 实现的 HibernateTemplate 的方法

   ApplicationContext ac=new ClassPathXmlApplicationContext("application.xml");
   SessionFactory sessionFactory=(SessionFactory)ac.getBean("hibernateSessionFactory");
   HibernateTemplate template=new HibernateTemplate(sessionFactory)
   template.execute(new HibernateCallback(){
        public Object doInHibernate(Session session) throws HibernateException,SQLException{
           //do the work
           return null
        }
   })

在配置文件中

   <bean id="hibernateTemplate" class="org.springframework.orm.hibernate.HibernateTemplate">
        <property name="sessionFactory" ref="hibernateSessionFactory"/>
   </bean>
   HibernateTemplate template=(HibernateTemplate)at.getBean("hibernateTemplate");
   template.execute(new HibernateCallback(){
        public Object doInHibernate(Session session) throws HibernateException,SQLException{
           //do the work
           return null
        }
   })

5. Hibernate 不支持泛型，要对自己的代码进行单元测试和集成测试，保证返回了正确的对象

6. 如何简写DAO
省去了在每个DAO中写 sessionFactory 的麻烦

  <bean id="hibernateDaoSupport" abstract="true" class="org.springframework.orm.hibernate.support.HibernateDaoSupport">
       <property name="sessionFactory" ref="hibernateSessionFactory"/>
    </bean>
    <bean id="dao1" class="com.test.class1" parent="hibernateDaoSupport"/>
    <bean id="dao2" class="com.test.class2" parent="hibernateDaoSupport"/>
    <bean id="dao3" class="com.test.class3" parent="hibernateDaoSupport"/>