hibernate08--OpenSessionInView

Posted 2020-09-28 丿少女梦丶

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<Session> threadLocal = new ThreadLocal<Session>();
    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 <code>SessionFactory</code> 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<Street> 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

  <filter>
    <filter-name>openSession</filter-name>
    <filter-class>cn.bdqn.filter.OpenSessionInViewFilter</filter-class>
  </filter>
  
  
    <filter-mapping>
     <filter-name>openSession</filter-name>
     <url-pattern>/*</url-pattern>
    </filter-mapping>

 

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" %>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">
    
    <title>My JSP ‘index.jsp‘ starting page</title>
    <meta http-equiv="pragma" content="no-cache">
    <meta http-equiv="cache-control" content="no-cache">
    <meta http-equiv="expires" content="0">    
    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
    <meta http-equiv="description" content="This is my page">
    <!--
    <link rel="stylesheet" type="text/css" href="styles.css">
    -->
  </head>
  
  <body>
    <c:forEach items="${streets}" var="s">
       ${s.id }
       ${s.name } <br/>
    </c:forEach>
  </body>
</html>