用HttpCombiner来减少js和css的请问次数

HttpCombiner也不记得是谁写的了，功能是把多个js文件或css文件合并到一块，压缩一下一起发给客户端来优化网站。
用法是这样的：
 
<script type="text/javascript" src="/Part/Handle/HttpCombiner.ashx?t=js&s=a.js,b.js,dialog/c.js,dialog/d.js"></script> 
 
  但这样又不利于找错，所以在中间又加了一个方法，可随时控制是如上引用还是，如下一般引用：
 
<script type="text/javascript" src="/RES/JS/a.js"></script>
<script type="text/javascript" src="/RES/JS/b.js"></script>
<script type="text/javascript" src="/RES/JS/dialog/c.js"></script>
<script type="text/javascript" src="/RES/JS/dialog/d.js"></script>
 
 修改后引用文件时：
 
<%= HttpCombiner.Requires(true,"js","a.js", "b.js", "dialog/c.js", "dialog/d.js")%> 
 
第一个参数来控制合并 。
 
 一般处理程序cs源码：
 
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using System;
using System.Web;
using System.Net;
using System.IO;
using System.IO.Compression;
using System.Text;
using System.Web.Caching;
 
public class HttpCombiner : IHttpHandler
{
    #region Config
    private const bool DO_GZIP = true;
    private readonly static TimeSpan CACHE_DURATION = TimeSpan.FromDays();
    private const string JSPathPre = "~/RES/JS/";
    private const string CSSPathPre = "~/RES/CSS/";
    private const string CombinerUrl = "/Part/Handle/HttpCombiner.ashx";//些handler路径
 
    private const string JSAbsPathPre = "/RES/JS/";
    private const string CSSAbsPathPre = "/RES/CSS/";
    #endregion
 
    #region Requires 默认combin
    public static string Requires(bool combin, string type, params string[] files)
    {
        if (combin)
        {
            if (type == "js")
            {
                return string.Format("<script type=\"text/javascript\" src=\"{0}?t=js&s={1}\"></script>", CombinerUrl, string.Join(",", files));
            }
            else if (type == "css")
            {
                return string.Format("<link rel=\"stylesheet\" type=\"text/css\" href=\"{0}?t=css&s={1}\"  />", CombinerUrl, string.Join(",", files));
            }
            else
            {
                return string.Empty;
            }
        }
        else
        {
            if (type == "js")
            {
                StringBuilder sb = new StringBuilder();
                foreach (var file in files)
                {
                    sb.AppendFormat("<script type=\"text/javascript\" src=\"{0}{1}\"></script>", JSAbsPathPre, file);
                    sb.AppendLine();
                }
                return sb.ToString();
            }
            else if (type == "css")
            {
                StringBuilder sb = new StringBuilder();
                foreach (var file in files)
                {
                    sb.AppendFormat("<link rel=\"stylesheet\" type=\"text/css\" href=\"{0}{1}\" />", CSSAbsPathPre, file);
                    sb.AppendLine();
                }
                return sb.ToString();
            }
            else
            {
                return string.Empty;
            }
        }
    }
    public static string Requires(string type, params string[] files)
    {
        return Requires(true, type, files);
    }
    #endregion
 
    #region Process
    public void ProcessRequest(HttpContext context)
    {
 
        HttpRequest request = context.Request;
 
        string setName = request["s"] ?? string.Empty;
        string contentType = request["t"] ?? string.Empty;
        if (string.IsNullOrEmpty(contentType))
        {
            contentType = "type/javascript";
        }
        else
        {
            if (contentType == "js")
            {
                contentType = "type/javascript";
            }
            else if (contentType == "css")
            {
                contentType = "text/css";
            }
            else
            {
                contentType = "text/plain";
            }
        }
        bool isCompressed = DO_GZIP && CanGZip(context.Request);
 
        UTF8Encoding encoding = new UTF8Encoding(false);
 
        if (!WriteFromCache(context, setName, isCompressed, contentType))
        {
            System.Collections.Generic.List<string> dependencyFiles = new System.Collections.Generic.List<string>();
            using (MemoryStream memoryStream = new MemoryStream())
            {
                using (Stream writer = isCompressed ?
                    (Stream)(new GZipStream(memoryStream, CompressionMode.Compress)) :
                    memoryStream)
                {
                    string[] fileNames = setName.Split(new char[] { ',' }, StringSplitOptions.RemoveEmptyEntries);
                    foreach (string fileName in fileNames)
                    {
                        byte[] fileBytes = GetFileBytes(contentType, context, fileName.Trim(), encoding, dependencyFiles);
                        writer.Write(fileBytes, , fileBytes.Length);
                    }
                    writer.Close();
                }
                byte[] responseBytes = memoryStream.ToArray();
                context.Cache.Insert(GetCacheKey(setName, isCompressed), responseBytes, new CacheDependency(dependencyFiles.ToArray()), System.Web.Caching.Cache.NoAbsoluteExpiration, CACHE_DURATION);
                WriteBytes(responseBytes, context, isCompressed, contentType);
            }
        }
    }
 
    private static byte[] GetFileBytes(string contentType, HttpContext context, string virtualPath, Encoding encoding, System.Collections.Generic.List<string> depencesFile)
    {
        if (virtualPath.StartsWith("http://", StringComparison.InvariantCultureIgnoreCase))
        {
            using (WebClient client = new WebClient())
            {
                return client.DownloadData(virtualPath);
            }
        }
        else
        {
            if (!virtualPath.StartsWith("~/", StringComparison.InvariantCultureIgnoreCase))
            {
                if (contentType == "text/css")
                {
                    virtualPath = CSSPathPre + virtualPath;
                }
                else if (contentType == "type/javascript")
                {
                    virtualPath = JSPathPre + virtualPath;
                }
            }
            string physicalPath = context.Server.MapPath(virtualPath);
            depencesFile.Add(physicalPath);
            byte[] bytes = File.ReadAllBytes(physicalPath);
            return bytes;
        }
    }
 
    private static bool WriteFromCache(HttpContext context, string setName,bool isCompressed, string contentType)
    {
        byte[] responseBytes = context.Cache[GetCacheKey(setName, isCompressed)] as byte[];
        if (null == responseBytes ||  == responseBytes.Length) return false;
        WriteBytes(responseBytes, context, isCompressed, contentType);
        return true;
    }
 
    private static void WriteBytes(byte[] bytes, HttpContext context,bool isCompressed, string contentType)
    {
        HttpResponse response = context.Response;
        response.AppendHeader("Content-Length", bytes.Length.ToString());
        response.ContentType = contentType;
        if (isCompressed) response.AppendHeader("Content-Encoding", "gzip");
        context.Response.Cache.SetCacheability(HttpCacheability.Public);
        context.Response.Cache.SetExpires(DateTime.Now.Add(CACHE_DURATION));
        context.Response.Cache.SetMaxAge(CACHE_DURATION);
        context.Response.Cache.AppendCacheExtension("must-revalidate, proxy-revalidate");
        response.OutputStream.Write(bytes, , bytes.Length);
        response.Flush();
    }
 
    private static bool CanGZip(HttpRequest request)
    {
        string acceptEncoding = request.Headers["Accept-Encoding"];
        if (!string.IsNullOrEmpty(acceptEncoding) && (acceptEncoding.Contains("gzip") || acceptEncoding.Contains("deflate")))
            return true;
        return false;
    }
 
    private static string GetCacheKey(string setName, bool isCompressed)
    {
        return "HttpCombiner." + setName + "." + isCompressed;
    }
 
    public bool IsReusable
    {
        get
        {
            return true;
        }
    }
    #endregion
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}