学习HttpHandler和HttpModule

一个最最简单的HttpHandler和HttpModule的事例，

首先实现一个HttpHandler类

using System.Web;
using System.Collections;

namespace WhosOn
{
    public class WhosOnHandler:IHttpHandler
    {
        
        public void ProcessRequest(HttpContext objContext)
        {
            Queue colPageStats;
            colPageStats = ((Queue)objContext.Cache["whoson"]);
            if (!(colPageStats == null)) 
            {
                objContext.Response.Write("<table border=1 cellpadding=4>");
                objContext.Response.Write("<tr><td colspan=4 bgcolor=orange>");
                objContext.Response.Write("<b>Who's On</b>");
                objContext.Response.Write("</td></tr>");
                objContext.Response.Write("<tr colspan=4 bgcolor=#eeeeee>");
                objContext.Response.Write("<th>Timestamp</th>");
                objContext.Response.Write("<th>Browser Type</th>");
                objContext.Response.Write("<th>Remote Address</th>");
                objContext.Response.Write("<th>Referrer</th>");
                objContext.Response.Write("</td></tr>");
                
                foreach (StatsEntry objStatsEntry in colPageStats) 
                {
                    objContext.Response.Write("<tr>");
                    objContext.Response.Write("<td>" + objStatsEntry.TimeStamp + "&nbsp;</td>");
                    objContext.Response.Write("<td>" + objStatsEntry.BrowserType + "&nbsp;</td>");
                    objContext.Response.Write("<td>" + objStatsEntry.UserHostName + "&nbsp;</td>");
                    objContext.Response.Write("<td>" + objStatsEntry.Referrer + "&nbsp;</td>");
                }
                objContext.Response.Write("</table>");
            }
        }

        public bool IsReusable 
        {
            get 
            {
                return true;
            }
        }
    }
}

然后再实现一个HttpModule类

using System;
using System.Web;
using System.Collections;
using System.Configuration;

namespace WhosOn
{
    public class WhosOnModule:IHttpModule
    {

        public void Init(HttpApplication myApp)
        {
            myApp.BeginRequest += new EventHandler(this.OnEnter);
        }

        public void Dispose()
        {
        }

        public void OnEnter(object s, EventArgs e)
        {
            HttpApplication objApp;
            HttpContext objContext;
            string strPath;
            Queue colPageStats;
            StatsEntry objStatsEntry;
            int intMaxEntries;
            objApp = ((HttpApplication)s);
            objContext = objApp.Context;
            strPath = objContext.Request.Path.ToLower();
            if(strPath.EndsWith(".axd"))
            {
                goto exitMethodDeclaration0;
            }
            intMaxEntries = System.Convert.ToInt32(ConfigurationSettings.AppSettings["whoson"]);
            colPageStats = ((Queue)objContext.Cache["whoson"]);
            if (colPageStats == null) 
            {
                colPageStats = new Queue();
            }
            objStatsEntry = new StatsEntry(objContext.Timestamp, objContext.Request.Browser.Type, objContext.Request.UserHostName, objContext.Request.ServerVariables["HTTP_REFERER"]);
            colPageStats.Enqueue(objStatsEntry);
            if (intMaxEntries != 0) 
            {
                while (colPageStats.Count > intMaxEntries) 
                {
                    colPageStats.Dequeue();
                }
            }
            objContext.Cache["whoson"] = colPageStats;
            exitMethodDeclaration0: ;
        }
    }
    public class StatsEntry
    {
        public DateTime TimeStamp;
        public string BrowserType;
        public string UserHostName;
        public string Referrer;

        public StatsEntry(DateTime TimeStamp, string BrowserType, string UserHostName, string Referrer)
        {
            this.TimeStamp = TimeStamp;
            this.BrowserType = BrowserType;
            this.UserHostName = UserHostName;
            this.Referrer = Referrer;
        }
    }
}

将编译的两个WhosOnModule和WhosOnHandler两个dll 放到一个web application的bin目录里，并在这个web application的web.config中添加如下项目

<configuration>
  <system.web>
    <httpModules>
    <add name="WhosOnModule"
     type="WhosOn.WhosOnModule,WhosOnModule" />
    </httpModules>
    <httpHandlers>
      <add verb="*" path="*.axd"
      type="WhosOn.WhosOnHandler,WhosOnHandler" />
    </httpHandlers>
  </system.web>
</configuration>