讨论：关于ThreadLocal用法的一点疑惑

/*
 * Created on 2004-11-25
 *
 */
package com.bupticet.append.hibernate.util;

import net.sf.hibernate.*;
import net.sf.hibernate.cfg.*;

/**
 * @author LJ-silver
 */
public class HibernateUtil {
    private static final SessionFactory sessionFactory;
    static {
        try {
            //Create the SessionFactory
            sessionFactory = new Configuration();.configure();
                    .buildSessionFactory();;
        } catch (HibernateException ex); {
            throw new RuntimeException("Configuration problem: "
                    + ex.getMessage();, ex);;
        }
    }

    public static final ThreadLocal session = new ThreadLocal();;

    public static Session currentSession(); throws HibernateException {
        Session s = (Session); session.get();;
        //Open a new Session, if this Thread has none yet
        if (s == null); {
            s = sessionFactory.openSession();;
            session.set(s);;
        }
        return s;
    }

    public static void closeSession(); throws HibernateException {
        Session s = (Session); session.get();;
        session.set(null);;
        if (s != null);
            s.close();;
    }
}

package com.bupticet.test;

import java.io.*;
import javax.servlet.*;

import net.sf.hibernate.HibernateException;
import net.sf.hibernate.Session;

import com.bupticet.append.hibernate.util.HibernateUtil;


public class HibernateFilter implements Filter {
    public HibernateFilter(); {
    }

    /**
     * destroy
     *
     * @todo Implement this javax.servlet.Filter method
     */
    public void destroy(); {
    }

    /**
     * doFilter
     *
     * @param servletRequest ServletRequest
     * @param servletResponse ServletResponse
     * @param filterChain FilterChain
     * @throws IOException
     * @throws ServletException
     * @todo Implement this javax.servlet.Filter method
     */
    public void doFilter(ServletRequest request,
                         ServletResponse response,
                         FilterChain chain); throws IOException,
            ServletException {
        try{
            request.setAttribute("HibernateSession",HibernateUtil.currentSession(););;
            chain.doFilter(request, response);; 
        }catch(HibernateException he);{
            he.printStackTrace();; 
        }finally{
            try{
                HibernateUtil.closeSession();;
            }catch(HibernateException he);{
                he.printStackTrace();; 
            }

        }
        
    }

    /**
     * init
     *
     * @param filterConfig FilterConfig
     * @throws ServletException
     * @todo Implement this javax.servlet.Filter method
     */
    public void init(FilterConfig filterConfig); throws ServletException {
    }
}

Session s = (Session);request.getAttribute("HibernateSession");;

package com.bupticet.test;

import java.io.*;
import javax.servlet.*;

import net.sf.hibernate.HibernateException;
import net.sf.hibernate.Session;

import com.bupticet.append.hibernate.util.HibernateUtil;


public class HibernateFilter implements Filter {
    public HibernateFilter(); {
    }

    /**
     * destroy
     *
     * @todo Implement this javax.servlet.Filter method
     */
    public void destroy(); {
    }

    /**
     * doFilter
     *
     * @param servletRequest ServletRequest
     * @param servletResponse ServletResponse
     * @param filterChain FilterChain
     * @throws IOException
     * @throws ServletException
     * @todo Implement this javax.servlet.Filter method
     */
    public void doFilter(ServletRequest request,
                         ServletResponse response,
                         FilterChain chain); throws IOException,
            ServletException {
        try{
            chain.doFilter(request, response);; 
        }catch(Exception he);{
            he.printStackTrace();; 
        }finally{
            try{
                HibernateUtil.closeSession();;
            }catch(HibernateException he);{
                he.printStackTrace();; 
            }

        }
        
    }

    /**
     * init
     *
     * @param filterConfig FilterConfig
     * @throws ServletException
     * @todo Implement this javax.servlet.Filter method
     */
    public void init(FilterConfig filterConfig); throws ServletException {
    }
}