java - hibernate session 和 DAO 的最佳实践是什么

Question

实际上，我正在寻找为 hibernate 4.2.x 使用 session 和 DAO 的最佳实践

第一种方法:

public class AccountDAOImpl implements AccountDAO {

    Session session=HibernateSessionFactoryUtil.getSession();
    Transaction transaction =null;
    @Override
    public void saveAccnt(Account account) {
        // TODO Auto-generated method stub
        try
        {
            transaction=session.beginTransaction();
            session.save(account);

            transaction.commit();

        }
        catch(RuntimeException re)
        {
            if(transaction!=null)
                transaction.rollback();
            throw re;
        }
        finally
        {
            session.close();
        }

    }
}

或者我们采用第二种方法:

public class AccountDAOImpl implements AccountDAO {

    Session session=HibernateSessionFactoryUtil.getSession();
    Transaction transaction =null;
    @Override
    public void saveAccnt(Account account) {
        // TODO Auto-generated method stub
        try
        {
            transaction=session.beginTransaction();
            session.save(account);

            transaction.commit();

        }
        catch(RuntimeException re)
        {
            if(transaction!=null)
                transaction.rollback();
            throw re;
        }


    }
}

close session的实际区别是每次需要执行DAO的时候都需要在工作完成的时候关闭session。

更新:

public class HibernateSessionFactoryUtil {

private static SessionFactory sessionFactory=null;
public static Session getSession() {

    if(sessionFactory==null)
    {
        createSessionFactory();
    }


    return sessionFactory.openSession();
}


public static SessionFactory getSessionFactory() {
    if(sessionFactory==null)
    {
        createSessionFactory();
    }
    return sessionFactory;
}


private static void createSessionFactory() {
    Configuration configuration = new Configuration();
    configuration.configure("/hibernate.cfg.xml");

    ServiceRegistry serviceRegistry = new ServiceRegistryBuilder().applySettings(configuration.getProperties()).buildServiceRegistry();
     sessionFactory = configuration.buildSessionFactory(serviceRegistry);
}

Answer 1

你不应该在你的方法中关闭 session :你没有在那里打开它。

执行您的第二种方法，或执行此操作:

public class AccountDAOImpl implements AccountDAO {

    @Override
    public void saveAccnt(Account account) {
        Transaction transaction =null;
        Session session=HibernateSessionFactoryUtil.getSession();
        try
        {
            transaction=session.beginTransaction();
            session.save(account);

            transaction.commit();

        }
        catch(RuntimeException re)
        {
            if(transaction!=null)
                transaction.rollback();
            throw re;
        }
        finally
        {
            session.close();
        }

    }
}