转载多线程下载(HTTPWebRequest)

下面是一个完整的多线程下载源码,我在写代码的时候遇到点问题也放在下面,希望大家别犯相同的错误。

问题1、线程偷懒?
在程序中我设置N个线程去下载时,然而有的线程却偷懒去了,当时非常奇怪,花了很多时间在代码上。
这其实是因为服务器不支持多线程下载造成的,大部分专业的下载站都禁止多线程下载,既然是服务器的原因那就没法了,在这里我想提一下在IIS7中启用和禁止多线程的方法。
应用程序池 -》 右击属性“高级设置” -》 进程模型 -》 最大工作进程数(这里便是设置允许多少线程)
至于IIS6也在应用程序池里设置,应用程序池- 》右击属性 -》 性能 -》 最大工作进程数。好了废话不说了,看下面的源码:

使用:
JhxzThreading mt = new JhxzThreading(5, “下载地址”, "本地保存路径");
mt.FileName = "wenjian"; //保存的文件名
mt.Start();

JhxzThreading公开了一些属性方便调用,如IsComplete表示这个下载任务是否完成,还有DownloadSize这个是实时下载了多少字节,通过这两个我们可以很容易实现进度条。如果有进度控件par:
pbar.Maximum = (int)mt.FileSize;
while (!mt.IsComplete)
{
    pbar.Value = mt.DownloadSize;
}

上面虽然实现进度条了,但是由于主线程一直在循环的工作,窗体可能会有假死现象,针对这个原因我们专门用一个线程来控制进度。于是有了下面的做法。
pbar.Maximum = (int)mt.FileSize;
Thread bar = new Thread(() => {
    while (!mt.IsComplete)
    {
        Thread.Sleep(50);
        this.SafeInvoke(() => { pbar.Value = mt.DownloadSize; });
    }
    MessageBox.Show("恭喜!文件已下载完成","提示",MessageBoxButtons.OK,MessageBoxIcon.Information);
});
bar.Start();

 

 

多线程下载类:

public class JhxzThreading
    {
        private int _threadNum;             //线程数量
        private long _fileSize;             //文件大小
        private string _extName;            //文件扩展名
        private string _fileUrl;            //文件地址
        private string _fileName;           //文件名
        private string _savePath;           //保存路径
        private short _threadCompleteNum;   //线程完成数量
        private bool _isComplete;           //是否完成
        private volatile int _downloadSize; //当前下载大小
        private Thread[] _thread;           //线程数组
        private List<string> _tempFiles = new List<string>();

        public string FileName
        {
            get
            {
                return _fileName;
            }
            set
            {
                _fileName = value;
            }
        }

        public long FileSize
        {
            get
            {
                return _fileSize;
            }
        }

        public int DownloadSize
        {
            get
            {
                return _downloadSize;
            }
        }

        public bool IsComplete
        {
            get
            {
                return _isComplete;
            }
            set
            {
                _isComplete = value;
            }
        }

        public int ThreadNum
        {
            get
            {
                return _threadNum;
            }
            set
            {
                _threadNum = value;
            }
        }

        public string SavePath
        {
            get
            {
                return _savePath;
            }
            set
            {
                _savePath = value;
            }
        }

        public JhxzThreading(int threahNum, string fileUrl,string savePath)
        {
            this._threadNum = threahNum;
            this._thread = new Thread[threahNum];
            this._fileUrl = fileUrl;
            this._savePath = savePath;
        }

        public void Start()
        {
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(_fileUrl);
            HttpWebResponse response = (HttpWebResponse)request.GetResponse();
            _extName = response.ResponseUri.ToString().Substring(response.ResponseUri.ToString().LastIndexOf('.'));//获取真实扩展名
            _fileSize = response.ContentLength;
            int singelNum = (int)(_fileSize / _threadNum);      //平均分配
            int remainder = (int)(_fileSize % _threadNum);      //获取剩余的
            request.Abort();
            response.Close();
            for (int i = 0; i < _threadNum; i++)
            {
                List<int> range = new List<int>();
                range.Add(i * singelNum);
                if (remainder != 0 && (_threadNum - 1) == i)    //剩余的交给最后一个线程
                    range.Add(i * singelNum + singelNum + remainder - 1);
                else
                    range.Add(i * singelNum + singelNum - 1);
                _thread[i] = new Thread(() => { Download(range[0], range[1]); });
                _thread[i].Name = "jhxz_{0}".Formart(i + 1);
                _thread[i].Start();
            }
        }

        private void Download(int from, int to)
        {
            Stream httpFileStream = null, localFileStram = null;
            try
            {
                string tmpFileBlock = @"{0}\{1}_{2}.dat".Formart(_savePath, _fileName, Thread.CurrentThread.Name);
                _tempFiles.Add(tmpFileBlock);
                HttpWebRequest httprequest = (HttpWebRequest)WebRequest.Create(_fileUrl);
                httprequest.AddRange(from, to);
                HttpWebResponse httpresponse = (HttpWebResponse)httprequest.GetResponse();
                httpFileStream = httpresponse.GetResponseStream();
                localFileStram = new FileStream(tmpFileBlock, FileMode.Create);
                byte[] by = new byte[5000];
                int getByteSize = httpFileStream.Read(by, 0, (int)by.Length);           //Read方法将返回读入by变量中的总字节数
                while (getByteSize > 0)
                {
                    Thread.Sleep(20);
                    _downloadSize += getByteSize;
                    localFileStram.Write(by, 0, getByteSize);
                    getByteSize = httpFileStream.Read(by, 0, (int)by.Length);
                }
                _threadCompleteNum++;
            }
            catch (Exception ex)
            {
                throw new Exception(ex.Message.ToString());
            }
            finally
            {
                if (httpFileStream != null) httpFileStream.Dispose();
                if (localFileStram != null) localFileStram.Dispose();
            }
            if (_threadCompleteNum == _threadNum)
            {
                _isComplete = true;
                Complete();
            }
        }

        private void Complete()
        {
            Stream mergeFile = new FileStream(@"{0}\{1}{2}".Formart(_savePath, _fileName, _extName), FileMode.Create);
            BinaryWriter AddWriter = new BinaryWriter(mergeFile);
            foreach (string file in _tempFiles)
            {
                using (FileStream fs = new FileStream(file, FileMode.Open))
                {
                    BinaryReader TempReader = new BinaryReader(fs);
                    AddWriter.Write(TempReader.ReadBytes((int)fs.Length));
                    TempReader.Close();
                }
                File.Delete(file);
            }
            AddWriter.Close();
        }
    }

 

posted @ 2010-04-21 18:07  nyzfl  阅读(1004)  评论(0编辑  收藏  举报