JSP中计算页面执行（处理）时间

package com.chinajavaworld.util;

import java.io.IOException;
import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;

public class TimerFilter
    implements Filter
{
    public static class Timer
    {

        long time;

        public void start()
        {
            time = System.currentTimeMillis();
        }

        public void stop()
        {
            time = System.currentTimeMillis() - time;
        }

        public long getTime()
        {
            return time;
        }

        public Timer()
        {
            time = 0L;
        }
    }


    public static final String DEFAULT_TIMER_ATTRIBUTE = "cjw.timer";
    private String key;

    public TimerFilter()
    {
        key = null;
    }

    public void init(FilterConfig filterConfig)
        throws ServletException
    {
        if(filterConfig.getInitParameter("key") != null)
            key = filterConfig.getInitParameter("key");
        else
            key = DEFAULT_TIMER_ATTRIBUTE;
    }

    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain)
        throws IOException, ServletException
    {
        HttpServletRequest request = (HttpServletRequest)servletRequest;
        Timer timer = new Timer();
        timer.start();
        request.setAttribute(key, timer);
        filterChain.doFilter(servletRequest, servletResponse);
        timer.stop();
        handleTimer(timer);
    }

    public void handleTimer(Timer timer1)
    {
    }

    public void destroy()
    {
    }
}

    <filter>
        <filter-name>Timer</filter-name>
        <filter-class>com.chinajavaworld.util.TimerFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>Timer</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

<%
    // Get the timer from the request as an attribute if it exists:
    TimerFilter.Timer timer
            = (TimerFilter.Timer)request.getAttribute(TimerFilter.DEFAULT_TIMER_ATTRIBUTE);
    if (timer != null) {
        timer.stop();
%>
    <p style="font-size:11px;">Processed in <b><%= timer.getTime() %></b> ms
<%}%>