httpHandlers文件下载

1:编写一个实现IHttpHandler的类。

 
 public class DownloadFileProcesser : IHttpHandler
    ...{
        private DownLoadData logdata = new DownLoadData();
        public DownloadFileProcesser()
         {

        }

        public void ProcessRequest(HttpContext context)
         {
                       string fileName = context.Request.Url.OriginalString;   //获取请求的url
               string ORIGINALURL = fileName;  //完整的请求路径
       int index = fileName.LastIndexOf("/");    //取最后一个/的未知
            fileName = fileName.Substring(index + 1);                 string filepath = fileName;
            int iBegin = fileName.LastIndexOf("_");  //取"_"之前和"."后面的，组成aaa.dd
            int iEnd = fileName.LastIndexOf(".");

            string localPath = System.Configuration.ConfigurationManager.AppSettings["downLoadPath"];  //下载文件的存放路径
            if (iBegin >= 0)
             {
                filepath = fileName.Substring(0, iBegin) + fileName.Substring(iEnd);
                filepath = context.Server.MapPath(localPath + filepath);
            }
            else
             {
                //  filepath = Path.Combine(localPath, fileName);
                filepath = context.Server.MapPath(localPath + fileName);
            }
            //  downLoadHandle aa = new downLoadHandle(outputBinary);
            if (File.Exists(filepath))  //文件是否存在。不存在的话按照真实文件名下载
             {
                outputBinary(fileName, filepath, context);
                sendState = 1;
            }
            else
             {
                context.Response.Status = "404 Not Found ";
                sendState = 0;
            }
            logdata.SENDSTATE = sendState;
           int indexLfn = filepath.LastIndexOf("\");
            string  localFileName = filepath.Substring(index1 + 1);
            logdata.LOCALFILENAME = localFileName;
            logdata.ORIGINALURL = ORIGINALURL;
            WriteDownLoadLog();
        }
   // 文件按照二进制流循环输出。其实没必要这么写。
        public void outputBinary(string fileName, string filepath, HttpContext context)
         {

            context.Response.ContentType = "application/octet-stream";
            context.Response.AppendHeader("Content-Disposition", "attachment; filename=" + fileName);
            using (System.IO.FileStream fs = new System.IO.FileStream(filepath, System.IO.FileMode.Open, System.IO.FileAccess.Read))
            {
                byte[] aLogData = new byte[1024];
                int len;
                //设定每次读取1024个字节。避免多人下载时过慢。
                while ((len = fs.Read(aLogData, 0, aLogData.Length)) > 0)
                   {
                    context.Response.BinaryWrite(_FixBuffer(aLogData, len));
                }
            }

        }
        /**//// <summary>
        /// 取指定长度的文件
        /// </summary>
        /// <param name="aLogData"></param>
        /// <param name="len"></param>
        /// <returns></returns>
        private byte[] _FixBuffer(byte[] aLogData, int len)
        {
            if (aLogData.Length == len)
                return aLogData;

            byte[] buffer = new byte[len];
            Array.Copy(aLogData, buffer, len);
            return buffer;
        }
        public bool IsReusable
        {
            get
            {
                return true;
            }
        }
}

 

2：配置webconfitg

<httpHandlers>

<!--当请求的后缀为.cab的时候，调用DownloadFileProcesser这个继承IHttpHandler接口的类-!>
   <add verb="GET,POST" path="*.cab" type="DownloadFileProcesser"/>
  </httpHandlers>

3：运行IIS服务管理器，右键点击默认Web站点，选择属性，移动到Home目录选项页，并点击配置按钮。应用程序配置对话框弹出来了。点击添加按钮并在可执行字段输入aspnet_isapi.dll文件路径，在扩展字段输入.kim
ps:如果你的操作系统是XP SP2的话，在输入aspnet_isapi.dll路径时需要手工输入，不能用复制粘贴的形式，否则保存按钮变灰。浏览时去掉check file exit选项。