新版本中spring與hibernate整合dao層調用session的方法

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

在spring和hibernate整合架構中，session factory被配置為一個spring
bean，以前版本會利用HibernateDaoSupport和HibernateTemplate這兩個類，在新版本中可直接利用方法
session factory的getCurrentSession()返回當前事務的session。

如：

1. public List<Paper> getAll() {<br /> 2. Session session = this.sessionFactory.getCurrentSession();<br /> 3. List<Paper> papers = (List<Paper>)session.createQuery("from Paper").list();<br /> 4. return papers;<br /> 5. } Hibernate 3.0.1開始具有有contextual sessions特性，這樣hibernate為每個交易管理一個當前session。之前都是spring的相關支援類來實現這個功能。我們推薦使用這種方式。優點：只依賴於hibernate，不再需要spring相關類。減小入侵性。（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為其事務策略 支援Hibernate的
SessionFactory.getCurrentSession() 方法, 返回當前spring管理的事務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() {<br />Session session = this.sessionFactory.getCurrentSession();<br />List<Paper> papers = (List<Paper>)session.createQuery("from Paper").list();<br />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.