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【CSharp】反向代理，可以缓存
作者:foxidea / 发布于2013/1/8/ 971
<%@ WebHandler Language="C#" Class="proxy" %>

using System;
using System.Web;
using System.Net;
using System.Text;
using System.IO;
using System.Collections.Generic;
using System.Configuration;



/// <summary>
/// 把http headers 和 http 响应的内容 分别存储在 /proxy/header/ 和 /proxy/body/ 中
/// 分层次创建目录
/// </summary>
public class proxy : IHttpHandler
{

    HttpResponse Response;
    HttpRequest Request;
    HttpApplicationState Application;
    HttpServerUtility Server;

    static string proxyCacheFolder = ConfigurationManager.AppSettings["proxyCacheFolder"];
    static string proxyDomain = ConfigurationManager.AppSettings["proxyDomain"];
    static string proxyReferer = ConfigurationManager.AppSettings["proxyReferer"];
    bool proxyCacheDirectAccess = ConfigurationManager.AppSettings["proxyCacheDirectAccess"] == "true";
    int proxyCacheSeconds = int.Parse(ConfigurationManager.AppSettings["proxyCacheSeconds"]);



    public void ProcessRequest(HttpContext context)
    {
        Response = context.Response;
        Request = context.Request;
        Application = context.Application;
        Server = context.Server;

        string path = context.Request.RawUrl;
        bool delCache = path.IndexOf("?del") > 0;
        if (delCache)
        {
            path = path.Replace("?del", string.Empty);
            DeleteCacheFile(path);
            return;
        }


        bool allowCache = Request.QueryString["cache"] == "true";
        string seconds = Request.QueryString["seconds"] ?? string.Empty;
        if (!int.TryParse(seconds, out proxyCacheSeconds))
        {
            proxyCacheSeconds = 3600;
        }

        if (allowCache)
        {

            EchoData(path);
        }
        else
        {

            WebClient wc = new WebClient();
            wc.Headers.Set("Referer", proxyReferer);
            byte[] buffer = wc.DownloadData(proxyDomain + path);
            Response.ContentType = wc.ResponseHeaders["Content-Type"];
            foreach (string key in wc.ResponseHeaders.AllKeys)
            {

                Response.Headers.Set(key, wc.ResponseHeaders[key]);
            }
            wc.Dispose();
            Response.OutputStream.Write(buffer, 0, buffer.Length);
        }



    }


    /// <summary>
    /// 清理失效的缓存
    /// </summary>
    /// <param name="d"></param>
    void ClearTimeoutCache(DirectoryInfo d)
    {
        if (d.Exists)
        {
            FileInfo[] files = d.GetFiles();
            foreach (FileInfo file in files)
            {
                TimeSpan timeSpan = DateTime.Now - file.LastAccessTime;
                if (timeSpan.TotalSeconds > proxyCacheSeconds)
                {
                    file.Delete();
                }
            }
        }
    }

    string GetCacheFolderPath(string hash)
    {
        string s = string.Empty;
        for (int i = 0; i <= 2; i++)
        {
            s += hash[i] + "/";
        }

        return s;
    }

    /// <summary>
    /// 读取缓存的header 并输出
    /// </summary>
    /// <param name="cacheHeaderPath"></param>
    void EchoCacheHeader(string cacheHeaderPath)
    {
        string[] headers = File.ReadAllLines(cacheHeaderPath);
        for (int i = 0; i < headers.Length; i++)
        {
            string[] headerKeyValue = headers[i].Split(':');
            if (headerKeyValue.Length == 2)
            {
                if (headerKeyValue[0] == "Content-Type")
                {
                    Response.ContentType = headerKeyValue[1];
                }
                Response.Headers.Set(headerKeyValue[0], headerKeyValue[1]);
            }

        }

    }



    void DeleteCacheFile(string path)
    {
        string absFolder = Server.MapPath(proxyCacheFolder);
        string hash = GetHashString(path);

        string folder = GetCacheFolderPath(hash);

        string cacheBodyPath = absFolder + "/body/" + folder + hash;
        string cacheHeaderPath = absFolder + "/header/" + folder + hash;

        FileInfo cacheBody = new FileInfo(cacheBodyPath);
        FileInfo cacheHeader = new FileInfo(cacheHeaderPath);

        if (cacheBody.Exists)
        {
            cacheBody.Delete();
        }

        if (cacheHeader.Exists)
        {
            cacheHeader.Delete();
        }

        Response.Write("delete cache file Success!\r\n" + path);
    }

    /// <summary>
    /// 输出缓存
    /// </summary>
    /// <param name="cacheHeaderPath">缓存header 的文件路径</param>
    /// <param name="cacheBodyPath">缓存 body 的文件路径</param>
    /// <param name="ifTimeout">是否进行判断文件过期</param>
    /// <returns>是否输出成功</returns>
    bool EchoCacheFile(string cacheHeaderPath, string cacheBodyPath, bool ifTimeout)
    {
        FileInfo cacheBody = new FileInfo(cacheBodyPath);
        FileInfo cacheHeader = new FileInfo(cacheHeaderPath);

        ClearTimeoutCache(cacheBody.Directory);
        ClearTimeoutCache(cacheHeader.Directory);

        if (cacheBody.Exists && cacheHeader.Exists)
        {

            if (ifTimeout)
            {
                TimeSpan timeSpan = DateTime.Now - cacheBody.LastWriteTime;
                if (timeSpan.TotalSeconds < proxyCacheSeconds)
                {
                    EchoCacheHeader(cacheHeaderPath);

                    Response.TransmitFile(cacheBodyPath);
                    return true;
                }
            }
            else
            {
                EchoCacheHeader(cacheHeaderPath);

                Response.TransmitFile(cacheBodyPath);
                return true;
            }

        }

        return false;
    }

    void EchoData(string path)
    {

        string absFolder = Server.MapPath(proxyCacheFolder);
        string hash = GetHashString(path);

        string folder = GetCacheFolderPath(hash);

        string cacheBodyPath = absFolder + "/body/" + folder + hash;
        string cacheHeaderPath = absFolder + "/header/" + folder + hash;

        bool success;
        if (proxyCacheDirectAccess)
        {
            success = EchoCacheFile(cacheHeaderPath, cacheBodyPath, false);
            if (!success)
            {
                Response.Write("直接从缓存读取失败!");
            }
            return;
        }

        success = EchoCacheFile(cacheHeaderPath, cacheBodyPath, true);

        if (success)
        {
            return;
        }




        //更新Cache File
        string ApplicationKey = "CacheList";
        List<string> List = null;


        if (Application[ApplicationKey] == null)
        {            
            Application.Lock();
            Application[ApplicationKey] = List = new List<string>(1000);
            Application.UnLock();
        }
        else
        {

            List = (List<string>)Application[ApplicationKey];

        }


        //判断是否已有另一个进程正在更新Cache File
        if (List.Contains(hash))
        {
            success = EchoCacheFile(cacheHeaderPath, cacheBodyPath, false);
            if (success)
            {
                return;
            }
            else
            {

                WebClient wc = new WebClient();
                wc.Headers.Set("Referer", proxyReferer);
                //主体内容
                byte[] data = wc.DownloadData(proxyDomain + path);

                //处理header
                Response.ContentType = wc.ResponseHeaders["Content-Type"];
                foreach (string key in wc.ResponseHeaders.AllKeys)
                {
                    Response.Headers.Set(key, wc.ResponseHeaders[key]);
                }
                wc.Dispose();
                Response.BinaryWrite(data);
                
            }
        }
        else
        {

          
 

            WebClient wc = new WebClient();
            wc.Headers.Set("Referer", proxyReferer);
            StringBuilder headersb = new StringBuilder();

            List.Add(hash);
            //主体内容
            byte[] data = wc.DownloadData(proxyDomain + path);





            //处理header

            Response.ContentType = wc.ResponseHeaders["Content-Type"];
            foreach (string key in wc.ResponseHeaders.AllKeys)
            {
                headersb.Append(key);
                headersb.Append(":");
                headersb.Append(wc.ResponseHeaders[key]);
                headersb.Append("\r\n");
                Response.Headers.Set(key, wc.ResponseHeaders[key]);
            }
            wc.Dispose();

            string headers = headersb.ToString().Trim();
            if (!Directory.Exists(absFolder + "/header/" + folder))
            {
                Directory.CreateDirectory(absFolder + "/header/" + folder);
            }

            StreamWriter sw = File.CreateText(absFolder + "/header/" + folder + hash);
            sw.Write(headers);
            sw.Close();
            sw.Dispose();


            //处理缓存内容
            if (!Directory.Exists(absFolder + "/body/" + folder))
            {
                Directory.CreateDirectory(absFolder + "/body/" + folder);
            }

            FileStream fs = File.Create(absFolder + "/body/" + folder + hash);
            fs.Write(data, 0, data.Length);
            fs.Close();
            fs.Dispose();

            List.Remove(hash);
            
          

            Response.BinaryWrite(data);
        }
    }




    string GetHashString(string path)
    {
        string md5 = GetMd5Str(path);
        return md5;
    }


    static string GetMd5Str(string ConvertString)
    {
        System.Security.Cryptography.MD5CryptoServiceProvider md5 = new System.Security.Cryptography.MD5CryptoServiceProvider();
        string t2 = BitConverter.ToString(md5.ComputeHash(UTF8Encoding.Default.GetBytes(ConvertString)), 4, 8);
        t2 = t2.Replace("-", "");

        return t2;
    }


    public bool IsReusable
    {
        get
        {
            return false;
        }
    }

}
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