学步园

http://support.microsoft.com/kb/307023

/*
 * REVERSE PROXY SERVER - IIS HTTP HANDLER - C# .NET v2.0
 * 
 * FILE NAME    :    Program.cs
 * 
 * DATE CREATED :    March 26, 2007, 16:15:05
 * CREATED BY   :    Gunasekaran Paramesh
 * 
 * LAST UPDATED :    April 16, 2007, 3:10:09 PM
 * UPDATED BY   :    Gunasekaran Paramesh
 * 
 * DESCRIPTION  :    Implementation of Reverse Proxy Server through IIS HTTP 
                     handler in C# .NET v2.0
*/

using System;
using System.IO;
using System.Net;
using System.Web;
using System.Text;
using System.Web.Mail;
using System.Collections;
using System.Configuration;
using System.Web.SessionState;
using System.DirectoryServices;

namespace TryHTTPHandler
{
public class SyncHandler : IHttpHandler, IRequiresSessionState
{
    public bool IsReusable { get { return true; } }

    // Process incoming request
    public void ProcessRequest(HttpContext Context)
    {            
        string ServerURL = "";            

        try
        {
            // Parsing incoming URL and extracting original server URL
            char[] URL_Separator = { '/' };
            string[] URL_List = Context.Request.Url.AbsoluteUri.Remove(0, 
                7).Split(URL_Separator);
            ServerURL = "http://" + 
                URL_List[2].Remove(URL_List[2].Length - 5, 5) + @"/";
            string URLPrefix = @"/" + URL_List[1] + @"/" + 
                URL_List[2]; // Eg. "/handler/stg2web.sync";
            for ( int i = 3; i < URL_List.Length; i++ )
                ServerURL += URL_List[i] + @"/";
            ServerURL = ServerURL.Remove(ServerURL.Length -1, 1);
            WriteLog(ServerURL + " (" + 
                Context.Request.Url.ToString() + ")");

            // Extracting POST data from incoming request
            Stream RequestStream = Context.Request.InputStream;
            byte[] PostData = new byte[Context.Request.InputStream.Length];
            RequestStream.Read(PostData, 0,
                (int) Context.Request.InputStream.Length);

            // Creating proxy web request
            HttpWebRequest ProxyRequest = (
                HttpWebRequest) WebRequest.Create(ServerURL);
            if ( ConfigurationManager.AppSettings["UpchainProxy"] == 
                "true" )
                ProxyRequest.Proxy = new WebProxy(
                    ConfigurationManager.AppSettings["Proxy"], true);

            ProxyRequest.Method = Context.Request.HttpMethod;
            ProxyRequest.UserAgent = Context.Request.UserAgent;                
            CookieContainer ProxyCookieContainer = new CookieContainer();
            ProxyRequest.CookieContainer = new CookieContainer();
            ProxyRequest.CookieContainer.Add(
                ProxyCookieContainer.GetCookies(new Uri(ServerURL)));
            ProxyRequest.KeepAlive = true;

            //For POST, write the post data extracted from the incoming request
            if ( ProxyRequest.Method == "POST" )
            {
                ProxyRequest.ContentType = 
                    "application/x-www-form-urlencoded";
                ProxyRequest.ContentLength = PostData.Length;
                Stream ProxyRequestStream = ProxyRequest.GetRequestStream();
                ProxyRequestStream.Write(PostData, 0, PostData.Length);
                ProxyRequestStream.Close();
            }

            // Getting response from the proxy request                
            HttpWebResponse ProxyResponse = (
                HttpWebResponse) ProxyRequest.GetResponse();

            if (ProxyRequest.HaveResponse)
            {
                // Handle cookies
                foreach(Cookie ReturnCookie in ProxyResponse.Cookies)
                {
                    bool CookieFound = false;
                    foreach(Cookie OldCookie in 
                        ProxyCookieContainer.GetCookies(new Uri(ServerURL)))
                    {
                        if (ReturnCookie.Name.Equals(OldCookie.Name))
                        {
                            OldCookie.Value = ReturnCookie.Value;
                            CookieFound = true;
                        }
                    }
                    if (!CookieFound)
                        ProxyCookieContainer.Add(ReturnCookie);
                }
            }

            Stream StreamResponse = ProxyResponse.GetResponseStream();
            int ResponseReadBufferSize = 256;
            byte[] ResponseReadBuffer = new byte[ResponseReadBufferSize];
            MemoryStream MemoryStreamResponse = new MemoryStream();

            int ResponseCount = StreamResponse.Read(ResponseReadBuffer, 0, 
                ResponseReadBufferSize);
            while ( ResponseCount > 0 )
            {
                MemoryStreamResponse.Write(ResponseReadBuffer, 0, 
                    ResponseCount);
                ResponseCount = StreamResponse.Read(ResponseReadBuffer, 0, 
                    ResponseReadBufferSize);
            }

            byte[] ResponseData = MemoryStreamResponse.ToArray();
            string ResponseDataString = Encoding.ASCII.GetString(ResponseData);

            // While rendering HTML, parse and modify the URLs present
            if ( ProxyResponse.ContentType.StartsWith("text/html") )
            {
                HTML.ParseHTML Parser = new HTML.ParseHTML();
                Parser.Source = ResponseDataString;                    
                while( !Parser.Eof() )
                {
                    char ch = Parser.Parse();
                    if ( ch == 0 )
                    {
                        HTML.AttributeList Tag = Parser.GetTag();
                        if ( Tag["href"] != null )
                        {
                            if ( Tag["href"].Value.StartsWith(
                                @"/") )
                            {
                                WriteLog("URL " +  
                                    Tag["href"].Value + 
                                    " modified to " + URLPrefix + 
                                    Tag["href"].Value);
                                ResponseDataString = 
                                    ResponseDataString.Replace(
                                    "/"" + 
                                    Tag["href"].Value + 
                                    "/"", "/"" + 
                                    URLPrefix + Tag["href"].Value + 
                                    "/"");
                            }
                        }

                        if ( Tag["src"] != null )
                        {
                            if ( Tag["src"].Value.StartsWith(
                                @"/") )
                            {
                                WriteLog("URL " +  
                                    Tag["src"].Value + 
                                    " modified to " + 
                                    URLPrefix + Tag["src"].Value);
                                ResponseDataString = 
                                    ResponseDataString.Replace(
                                    "/"" + 
                                    Tag["src"].Value + 
                                    "/"", "/"" + 
                                    URLPrefix + Tag["src"].Value + 
                                    "/"");
                            }
                        }
                    }
                }
                Context.Response.Write(ResponseDataString);
            }
            else
                Context.Response.OutputStream.Write(ResponseData, 0, 
                    ResponseData.Length);

            MemoryStreamResponse.Close();
            StreamResponse.Close();
            ProxyResponse.Close();
        }
        catch ( Exception Ex )
        {
            Context.Response.Write(Ex.Message.ToString());
            WriteLog("An error has occurred while requesting the URL 
                " + ServerURL + "(" + 
                Context.Request.Url.ToString() + ")/n" + 
                Ex.ToString());
        }
    }        

    // Write debug log message
    private void WriteLog(string Message)
    {
        FileStream FS = new FileStream(ConfigurationManager.AppSettings[
            "Log"], FileMode.Append, FileAccess.Write);
        string DateTimeString = DateTime.Now.ToString();
        Message = "[" + DateTimeString + "] " + Message + 
            "/n";
        byte[] FileBuffer = Encoding.ASCII.GetBytes(Message);
        FS.Write(FileBuffer, 0, (int)FileBuffer.Length);
        FS.Flush(); FS.Close();
    }
}
}