新版本中spring与hibernate整合dao层调用session的方法

（选自：《Beginning Hibernate》及《spring-framework-3.0.5.RELEASE reference》）

在spring和hibernate整合框架中，session factory被配置为一个spring
bean，以前版本会利用HibernateDaoSupport和HibernateTemplate这两个类，在新版本中可直接利用方法
session factory的getCurrentSession()返回当前事务的session。

如：

1. public List<Paper> getAll() {
2. Session session = this.sessionFactory.getCurrentSession();
3. List<Paper> papers = (List<Paper>)session.createQuery("from Paper").list();
4. return papers;
5. }

Hibernate 3.0.1开始具有有contextual sessions特性，这样hibernate为每个事务管理一个当前session。之前都是spring的相关支持类来实现这个功能。我们推荐使用这种方式。
优点：只依赖于hibernate，不再需要spring相关类。减小入侵性。

（Hibernate 3 has a feature called contextual sessions, wherein
Hibernate itself manages one current

Session

per transaction. This is roughly
equivalent to Spring's synchronization of one Hibernate

Session

per transaction. A corresponding
DAO implementation resembles the following example, based on the plain
Hibernate API:）
Spring的 LocalSessionFactoryBean为其事务策略 支持Hibernate的

SessionFactory.getCurrentSession() 方法, 返回当前spring管理的事务session，

（Spring's LocalSessionFactoryBean supports Hibernate's

SessionFactory.getCurrentSession() method for any Spring transaction strategy, returning

the current Spring-managed transactional Session even with HibernateTransactionManager.）

public List<Paper> getAll() {
Session session = this.sessionFactory.getCurrentSession();
List<Paper> papers = (List<Paper>)session.createQuery("from Paper").list();
return papers;

With your session factory configured as a Spring bean, you can now go on to create DAOs that take

advantage of Hibernate’s functionality. Previous versions of Spring and Hibernate required the use of

the HibernateDaoSupport class and/or HibernateTemplate class to form the basis of your DAOs; however,

recent versions of Spring and Hibernate have eliminated the need for these classes. Hibernate now

supports a getCurrentSession() method on the SessionFactory that returns a Session object that is

associated with the current transaction.