利用过滤器对hibernate的session管理,实现session在线程范围内的共享

hibernate中的Session关系到对数据库的增删查改等基本的数据存取操作.对Session进行有效的维护,就像是在jdbc编程中对JDBC collection的维护.
     在struts+hibernate的方案中,常常利用过滤器(Filter)对session进行管理,以实现session在线程范围内的共享.为什么仅仅实现线程内的共享,是因为,不能把session用于多线程,否则会出现意外.在线程范围内实现sesion的共享.避免了session的频繁的创建和销毁.我看到有的程序中,在单个方法内,打开session,执行.关闭session.这显然没有在一次会话中有效的利用session
     下面的方案是.通过建立一个过滤器,以实现对sesion的共享:

package com.cs_oj.filter;

import java.io.IOException;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.hibernate.Session;
import org.hibernate.Transaction;


import com.cs_oj.data.dao.HibernateSessionFactory;

public class HibernateSessionFilter implements Filter {
    private static final Log log = LogFactory.getLog(HibernateSessionFilter.class);
    public void destroy() {
        // TODO Auto-generated method stub

    }

    public void doFilter(ServletRequest arg0, ServletResponse arg1,
            FilterChain chain) throws IOException, ServletException {
        log.debug("HibernateSessionFilter start");
        Date date=new Date();
        DateFormat df=new SimpleDateFormat("yyyy-MM-dd '时间--'HH:mm:ss");
        System.out.println("----当前时间:"+df.format(date)+"----");
        System.out.println("----------HibernateSessionFilter start-----------");

//利用HibernateSessionFactory, 得到当 前线程中的session对象..HibernateSessionFactory的代码利用了ThreadLocal模式..详见..HibernateSessionFactory
        Session session=HibernateSessionFactory.getSession(); 
        log.info("HibernateSessionFilter begin transaction");
        System.out.println("HibernateSessionFilter begin transaction");
       Transaction tx=session.beginTransaction();   //开始事务
        
        log.debug("HibernateSessionFilter begin doChain");
        HttpServletResponse response=(HttpServletResponse)arg1;
        try{
            chain.doFilter(arg0, arg1);
            
            log.debug("HibernateSessionFilter begin commit");
            //没有异常,则提交
            try{
                
                System.out.println("HibernateSessionFilter begin commit");
                tx.commit();
                System.out.println("HibernateSessionFilter commit success");
                
            }
            catch(Exception e){
                
                System.out.println("HibernateSessionFilter commit failed");
                System.out.println("HibernateSessionFilter begin rollback() ");
                try{
                    System.out.println("HibernateSessionFilter begin rollback() ");
                    tx.rollback();
                    System.out.println("HibernateSessionFilter rollback() success ");
                }catch(RuntimeException ex){
                    System.out.println("HibernateSessionFilter   rollback() failed");
                }
            }
        }catch (Exception e) {
            e.printStackTrace();
            System.out.println("chain.doFilter(arg0, arg1) exception accurs ");
            System.out.println("HibernateSessionFilter begin rollback() ");
            tx.rollback();   //出现异常,回滚
            //response.sendRedirect("error.jsp");
        }
        finally{
            log.debug("HibernateSessionFilter end doChain");
            System.out.println("HibernateSessionFilter begin close session");
           HibernateSessionFactory.closeSession();
            System.out.println("*********HibernateSessionFilter close session success*********");
            log.debug("HibernateSessionFilter begin close session");
            //System.out.println("session.isOpen()="+session.isOpen());
        }

    }

}

 

 

 

在web.xml文件中对上面的过滤器进行配置.

<filter>
    <filter-name>hibernateSession</filter-name>
    <filter-class>com.cs_oj.filter.HibernateSessionFilter</filter-class>
</filter>
<filter-mapping>
    <filter-name>hibernateSession</filter-name>
    <servlet-name>action</servlet-name>
   
</filter-mapping>
<servlet>
    <servlet-name>action</servlet-name>
    <servlet-class>org.apache.struts.action.ActionServlet</servlet-class>
    <init-param>.
    <init-param>
      <param-name>config</param-name>
      <param-value>/WEB-INF/struts-config.xml</param-value>
    </init-param>
    <init-param>
      <param-name>debug</param-name>
      <param-value>3</param-value>
    </init-param>
    <init-param>
      <param-name>detail</param-name>
      <param-value>3</param-value>
    </init-param>
    <load-on-startup>0</load-on-startup>
</servlet>
<servlet-mapping>
    <servlet-name>action</servlet-name>
    <url-pattern>*.do</url-pattern>
</servlet-mapping>

 

 

则对所有以.do作为后缀名的url,都会被过滤器过滤.在被过滤器过滤的action中,和业务层的方法内,只需要调用HibernateSessionFactory 的getSession()方法,得到当前线程内的session对象.用完session后,不要关闭session,而且,每次在用session进行添加和修改操作时,也不需要启动事务.

 

 

HibernateSessionFactory.java

 

package com.cs_oj.data.dao;

import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.cfg.Configuration;


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 String CONFIG_FILE_LOCATION = "/hibernate.cfg.xml";
    private static final ThreadLocal<Session> threadLocal = new ThreadLocal<Session>();
    private static Configuration configuration = new Configuration().configure();
    private static org.hibernate.SessionFactory sessionFactory;
    private static String configFile = CONFIG_FILE_LOCATION;

    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 = 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();
            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 = 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;
    }

}