/// <summary>
/// 功能简介：asp.net的下载业务的服务端基类(支持客户端显示下载百分比进度，支持并发数控制，支持限速)
/// 创建时间：2015-11-20
/// 创建人：pcw
/// 博客：https://www.cnblogs.com/taohuadaozhu
/// 备注：如果针对大文件下载，则还需要考虑操作系统或iis上最大下载字节数限制。
/// </summary>
public abstract class DownLoadAbs : IHttpHandler
{
private static StatusDataDict currStatuDataDict = new StatusDataDict(300);
protected object lockObj = new object();
public virtual void ProcessRequest(HttpContext context)
{
string sDiplayFileName = this.GetDisplayFileName(context);
string sServerFileFullPath = this.GetServerFileFullPath(context);
int iDownload = 0;
iDownload = this.ResponseFile(context.Request, context.Response, sDiplayFileName, sServerFileFullPath, this.BytesCountPerSecond);
if (iDownload != 1)
{
Utils.SaveErrorLog(string.Format("下载文件【{0}】失败(2015-12-15v1)，返回值={1}", sServerFileFullPath, iDownload));
if (iDownload == -202)
{
context.Response.Write(RuntimeContext.GetResponseJson("系统检测到重复的并发下载请求，请稍后再点击下载", -1, null));
}
else if (iDownload == -203)
{
context.Response.Write(RuntimeContext.GetResponseJson("并发下载人数超过最大连接数，请稍后再点击下载", -2, null));
}
context.Response.End();
}
}
protected abstract string GetDisplayFileName(HttpContext hcontext);
protected abstract string GetServerFileFullPath(HttpContext hcontext);
protected virtual int GetMaxConnectCount()
{
return 3;
}
protected virtual long BytesCountPerSecond
{
get
{
return 1024000;
}
}
public bool IsReusable
{
get
{
return false;
}
}
/// <summary>
/// 输入参数 _Request: Page.Request对象， _Response: Page.Response对象， _fileName: 下载文件名， _fullPath: 带文件名下载路径， _speed 每秒允许下载的字节数(默认:1024000 B,类似1M/秒)
/// </summary>
/// <param name="_Request"></param>
/// <param name="_Response"></param>
/// <param name="_displayFileName"></param>
/// <param name="_serverFilefullPath"></param>
/// <param name="_speed"></param>
/// <returns></returns>
protected int ResponseFile(HttpRequest _Request, HttpResponse _Response, string _displayFileName, string _serverFilefullPath, long _speed)
{
return this.ResponseForDownloadFile(_Request, _Response, _displayFileName, _serverFilefullPath, _speed);
}
/// <summary>
/// 输入参数 _Request: Page.Request对象， _Response: Page.Response对象， _fileName: 下载文件名， _fullPath: 带文件名下载路径， _speed 每秒允许下载的字节数(默认:1024000 B,类似1M/秒)
/// </summary>
/// <param name="_Request"></param>
/// <param name="_Response"></param>
/// <param name="_displayFileName"></param>
/// <param name="_serverFilefullPath"></param>
/// <param name="_speed"></param>
/// <returns></returns>
protected virtual int ResponseForDownloadFile(HttpRequest _Request, HttpResponse _Response, string _displayFileName, string _serverFilefullPath, long _speed)
{
bool bSuccess = true;
if (string.IsNullOrEmpty(_serverFilefullPath))
return -101;
if (string.IsNullOrEmpty(_displayFileName))
return -102;
if (_speed < 1)
return -103;
if (_Request == null)
return -104;
if (_Response == null)
return -105;
if (File.Exists(_serverFilefullPath) == false)
return -201;
if (currStatuDataDict.ExistsStatus(_serverFilefullPath))
{
return -202;
}
if (currStatuDataDict.GetStatusCount() >= this.GetMaxConnectCount())
{
return -203;
}
currStatuDataDict.AddStatusData(_serverFilefullPath);
FileStream targetFile = new FileStream(_serverFilefullPath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
BinaryReader br = new BinaryReader(targetFile);
try
{
_Response.AddHeader("Accept-Ranges", "bytes");
_Response.Buffer = false;
long fileTotalLength = targetFile.Length;
long startBytes = 0;
int packForBlock = 10240; //10K bytes
//int sleep = 200; //每秒5次 即5*10K bytes每秒
decimal dSleep = Convert.ToDecimal(1000 * packForBlock / _speed);
decimal dMaxCount = 0;
int sleep = (int)Math.Floor(dSleep) + 1;
if (_Request.Headers["Range"] != null) //这里是客户端返回来的，已下载的进度
{
_Response.StatusCode = 206;
string[] range = _Request.Headers["Range"].Split(new char[] { '=', '-' });
startBytes = Convert.ToInt64(range[1]);
}
_Response.AddHeader("Content-Length", (fileTotalLength - startBytes).ToString());//这是此次下载文件的总字节长度
if (startBytes != 0)//如果客户端支持，否则不会添加进度相关的信息
{
_Response.AddHeader("Content-Range", string.Format(" bytes {0}-{1}/{2}", startBytes, fileTotalLength - 1, fileTotalLength));//这是本次下载后重新定位的进度
}
/*
_Response.AddHeader("Connection", "Keep-Alive");
_Response.AddHeader("Keep-Alive", "timeout=600, max=4");
*/
_Response.ContentType = "application/octet-stream";
_Response.AddHeader("Content-Disposition", "attachment;filename=" + HttpUtility.UrlEncode(_displayFileName, System.Text.Encoding.UTF8));
br.BaseStream.Seek(startBytes, SeekOrigin.Begin);
dMaxCount = (fileTotalLength - startBytes) / packForBlock;
int maxCount = (int)Math.Floor(dMaxCount) + 1;
byte[] bytesRead = new byte[packForBlock];
for (int i = 0; i < maxCount; i++)
{
if (_Response != null && _Response.IsClientConnected)
{
if (File.Exists(_serverFilefullPath))
{
bytesRead = br.ReadBytes(packForBlock);
if (bytesRead != null)
{
_Response.BinaryWrite(bytesRead);
//_Response.Flush();//add by pcw
Thread.Sleep(sleep);//需要注意响应的最大时间设置
}
}
}
else
{
i = maxCount;
}
}
}
catch (Exception error)
{
bSuccess = false;
Utils.SaveErrorLog(string
.Format("输出文件【{0}】的文件流过程出现异常：{1},调试信息：{2}", _serverFilefullPath, error.Message, error.StackTrace));
}
finally
{
currStatuDataDict.RemoveStatuData(_serverFilefullPath);
if (br != null)
{
br.Close();
br.Dispose();
br = null;
}
if (targetFile != null)
{
targetFile.Close();
targetFile.Dispose();
targetFile = null;
}
if (_Response != null)
{
if (bSuccess)
{
Utils.SaveLog(string.Format("已成功提供客户端下载文件【{0}】", _serverFilefullPath));
}
//_Response.End();
HttpContext.Current.Response.SuppressContent = true; // Gets or sets a value indicating whether to send HTTP content to the client.
HttpContext.Current.ApplicationInstance.CompleteRequest(); // Causes ASP.NET to bypass all events and filtering in the HTTP pipeline chain of execution and directly execute the EndRequest event.
}
}
return 1;
}
}
