7.7--SSH学习之Hibernate Session

the first picture:

the second picture:

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首先来两张图

第一张图：大概意思是one.jsp把数据提交到servlet，（这里已开启一个新的事务，也是一个新的session），然后调用servive层，再调用dao层，最后在数据库查询数据，然后把数据返回到dao层，service层，servlet，最后在two.jsp中显示查询结果。在servlet向two.jsp提交查询结果之前，先解析jsp，然后提交事务，这时session也就关闭了。
总结：一次请求开启一个新的session


第二张图：jsp页面向servlet,service,dao层提交请求，要先经过过滤器，最后到数据库；返回数据也是一样，最后也要经过过滤器才能在jsp页面中显示查询结果

举个例子：

HibernateUtil .java

public class HibernateUtil {    private static final SessionFactory sessionFactory = buildSessionFactory();    private static final ThreadLocal<Session> threadLocal = new ThreadLocal<Session>();    private static SessionFactory buildSessionFactory() {        try {            // Create the SessionFactory from hibernate.cfg.xml            Configuration cfg = new  Configuration().configure();            SessionFactory sf= cfg.buildSessionFactory(new StandardServiceRegistryBuilder()                                .applySettings(cfg.getProperties()).build());            return sf;        }        catch (Throwable ex) {            // Make sure you log the exception, as it might be swallowed            System.err.println("Initial SessionFactory creation failed." + ex);            throw new ExceptionInInitializerError(ex);        }    }    public static SessionFactory getSessionFactory() {        return sessionFactory;    }    public static Session getSession(){        Session session = threadLocal.get();        if(session == null || !session.isOpen()){   //判断session是否为空，或者没打开            session = getSessionFactory().getCurrentSession();            threadLocal.set(session);        }        return session;    }}

GenericDaoImpl .java//相当于baseDaoImpl,接口的 父类

public class GenericDaoImpl implements GenericDao {    private Class genericEntity;    public Class getGenericEntity() {        return genericEntity;    }    public void setGenericEntity(Class genericEntity) {        this.genericEntity = genericEntity;    }    @Override    public void addEntity(Object obj) {        // TODO Auto-generated method stub        try{            Session session = HibernateUtil.getSession();            //session.beginTransaction();            session.save(obj);            //session.getTransaction().commit();        }catch(Exception e){            e.printStackTrace();        }    }    @Override    public void deleteEntity(Object obj) {        // TODO Auto-generated method stub        try{            Session session = HibernateUtil.getSession();            //session.beginTransaction();            session.delete(obj);            //session.getTransaction().commit();        }catch(Exception e){            e.printStackTrace();        }    }    @Override    public void updateEntity(Object obj) {        // TODO Auto-generated method stub        try{            Session session = HibernateUtil.getSession();            //session.beginTransaction();            session.update(obj);            //session.getTransaction().commit();        }catch(Exception e){            e.printStackTrace();        }    }    @Override    public Object findById(Serializable entityId) {        // TODO Auto-generated method stub        Object obj = null;        try{            Session session = HibernateUtil.getSession();            //session.beginTransaction();            obj = session.load(genericEntity, entityId);            //session.getTransaction().commit();        }catch(Exception e){            e.printStackTrace();        }        return obj;    }    @Override    public List findAll() {        // TODO Auto-generated method stub        List list = new ArrayList();        try{            Session session = HibernateUtil.getSession();            //session.beginTransaction();            list = session.createQuery("from "+genericEntity.getName()).list();            //session.getTransaction().commit();        }catch(Exception e){            e.printStackTrace();        }        return list;    }}

过滤器OpenSessionInViewFilter .java

public class OpenSessionInViewFilter implements Filter {    @Override    public void destroy() {    }    @Override    public void doFilter(ServletRequest request, ServletResponse response,            FilterChain chain) throws IOException, ServletException {        System.out.println("客户端请求服务器执行代码");        Session session = HibernateUtil.getSession();        session.beginTransaction();        chain.doFilter(request,response);        System.out.println("服务器响应客户器执行代码");        session.getTransaction().commit();    }    @Override    public void init(FilterConfig arg0) throws ServletException {    }}

运行程序后台显示信息为：



可见请求页面先经过过滤器，最后返回结果集时也要经过过滤器。