创建一个web项目，然后生成HibernateSessionFactory文件！

package cn.bdqn.util;import org.hibernate.HibernateException;import org.hibernate.Session;import org.hibernate.cfg.Configuration;/** * Configures and provides access to Hibernate sessions, tied to the * current thread of execution.  Follows the Thread Local Session * pattern, see {
    @link http://hibernate.org/42.html }. */public class HibernateSessionFactory {    /**      * Location of hibernate.cfg.xml file.     * Location should be on the classpath as Hibernate uses       * #resourceAsStream style lookup for its configuration file.      * The default classpath location of the hibernate config file is      * in the default package. Use #setConfigFile() to update      * the location of the configuration file for the current session.        */    private static final ThreadLocal
     
       threadLocal = new ThreadLocal
      
       ();    private static org.hibernate.SessionFactory sessionFactory;        private static Configuration configuration = new Configuration();    private static String CONFIG_FILE_LOCATION = "/hibernate.cfg.xml";    private static String configFile = CONFIG_FILE_LOCATION;    static {        try {            configuration.configure(configFile);            sessionFactory = configuration.buildSessionFactory();        } catch (Exception e) {            System.err.println("%%%% Error Creating SessionFactory %%%%");            e.printStackTrace();        }    }    private HibernateSessionFactory() {    }        /**     * Returns the ThreadLocal Session instance.  Lazy initialize     * the 
       SessionFactory if needed.     *     *  @return Session     *  @throws HibernateException     */    public static Session getSession() throws HibernateException {        Session session = (Session) threadLocal.get();        if (session == null || !session.isOpen()) {            if (sessionFactory == null) {                rebuildSessionFactory();            }            session = (sessionFactory != null) ? sessionFactory.openSession()                    : null;            threadLocal.set(session);        }        return session;    }    /**     *  Rebuild hibernate session factory     *     */    public static void rebuildSessionFactory() {        try {            configuration.configure(configFile);            sessionFactory = configuration.buildSessionFactory();        } catch (Exception e) {            System.err.println("%%%% Error Creating SessionFactory %%%%");            e.printStackTrace();        }    }    /**     *  Close the single hibernate session instance.     *     *  @throws HibernateException     */    public static void closeSession() throws HibernateException {        Session session = (Session) threadLocal.get();        threadLocal.set(null);        if (session != null) {            session.close();        }    }    /**     *  return session factory     *     */    public static org.hibernate.SessionFactory getSessionFactory() {        return sessionFactory;    }    /**     *  return session factory     *     *    session factory will be rebuilded in the next call     */    public static void setConfigFile(String configFile) {        HibernateSessionFactory.configFile = configFile;        sessionFactory = null;    }    /**     *  return hibernate configuration     *     */    public static Configuration getConfiguration() {        return configuration;    }}
      
     

在之前的基础上创建dao

public interface DistrictDao {    //根据制定的id查询区县信息     根据区县可以查询到街道    District   getDistrictById(Integer id);}

创建daoImpl

public class DistrictDaoImpl   implements  DistrictDao{    @Override    public District getDistrictById(Integer id) {        Session session = HibernateSessionFactory.getSession();         District district = (District) session.load(District.class, id);         System.out.println("daoImpl中的session=====>"+session.hashCode());        return district;    }    }

创建对应的servlet

public class DistrcitServlet extends HttpServlet {    public void doGet(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        doPost(request, response);    }    public void doPost(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        //实例化service层对象        DistrictDao dao=new DistrictDaoImpl();        //查询id是1001的区县下所有的街道        District district = dao.getDistrictById(1001);        List
     
       streets = district.getStreets();        //把街道放入指定的作用域        request.setAttribute("streets", streets);        request.getRequestDispatcher("index.jsp").forward(request, response);    }}
     

创建对应的Filter 并在web.xml文件中配置filter和filter-mapping

public class OpenSessionInViewFilter implements Filter {    @Override    public void destroy() {    }    //真正执行代码的地方    获取session  开启事务     @Override    public void doFilter(ServletRequest request, ServletResponse response,            FilterChain chain) throws IOException, ServletException {        Session session = HibernateSessionFactory.getSession();         System.out.println("filter中的session=====>"+session.hashCode());         chain.doFilter(request, response);         HibernateSessionFactory.closeSession();  //关闭session    }    @Override    public void init(FilterConfig arg0) throws ServletException {    }}

web.xml文件中新增

         
      
       openSession
          
      
       cn.bdqn.filter.OpenSessionInViewFilter
        
             
          
      
       openSession
           
      
       /*
          
     

之后创建页面

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%String path = request.getContextPath();String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";%><%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>                  
         
         
             
         
         
               
     
             ${s.id }       ${s.name }