[爬虫]抓取百万知乎用户信息之HttpHelper的迭代

             点击我前往Github查看源代码 

本项目github地址：https://github.com/wangqifan/ZhiHu

什么是Httphelper？

    httpelpers是一个封装好拿来获取网络上资源的工具类。因为是用http协议，故取名httphelper。

httphelper出现的背景

  使用WebClient可以很方便获取网络上的资源，例如

              WebClient client = new WebClient();
            string html=   client.DownloadString("https://www.baidu.com/");

这样就可以拿到百度首页的的源代码，由于WebClient封装性太强，有时候不大灵活，需要对底层有更细致的把控，这个时候就需要打造自己的网络资源获取工具了；

HttpHelper初级

  现在着手打造自己的下载工具，刚开始时候长这样

public class HttpHelp
  {
        public static string DownLoadString(string url)
        {

               string Source = string.Empty;

         HttpWebRequest request= (HttpWebRequest)WebRequest.Create(url);
         using (HttpWebResponse response = (HttpWebResponse)request.GetResponse()) 
        { 
            using (Stream stream = response.GetResponseStream())
            {
                using (StreamReader reader = new StreamReader(stream, Encoding.UTF8))
                       {
                          Source = reader.ReadToEnd(); 
                        } 
             } 
        }
        return  Source;
      }
 }
程序总会出现各种异常的，这个时候加个Try catch语句

public class HttpHelp
  {
        public static string DownLoadString(string url)
        {

           string Source = string.Empty;
           try{
                HttpWebRequest request= (HttpWebRequest)WebRequest.Create(url);
                using (HttpWebResponse response = (HttpWebResponse)request.GetResponse()) 
                { 
                    using (Stream stream = response.GetResponseStream())
                     {
                        using (StreamReader reader = new StreamReader(stream, Encoding.UTF8))
                       {
                          Source = reader.ReadToEnd(); 
                       } 
                    } 
                }
           }
          catch
          {
              Console.WriteLine("出错了，请求的URL为{0}", url);
          }
        return  Source;
      }
 }

请求资源是I/O密集型，特别耗时，这个时候需要异步

 public static async Task<string> DownLoadString(string url)
        {
            return await Task<string>.Run(() =>
            {
                string Source = string.Empty;
                try
                {
                    HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
                    using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
                    {
                        using (Stream stream = response.GetResponseStream())
                        {
                            using (StreamReader reader = new StreamReader(stream, Encoding.UTF8))
                            {
                                Source = reader.ReadToEnd();
                            }
                        }
                    }
                }
                catch
                {
                    Console.WriteLine("出错了，请求的URL为{0}", url);
                }
                return Source;
            });
           
        }

 HttpHelper完善       
为了欺骗服务器，让服务器认为这个请求是浏览器发出的

   request.UserAgent = "Mozilla/5.0 (Windows NT 10.0; WOW64; rv:49.0) Gecko/20100101 Firefox/49.0";

 有些资源是需要权限的，这个时候要伪装成某个用户，http协议是无状态的，标记信息都在cookie上面，给请求加上cookie

    request.Headers.Add("Cookie", "这里填cookie，从浏览器上面拷贝")

 再完善下，设定个超时吧

   request.Timeout = 5000;

有些网站提供资源是GZIP压缩，这样可以节省带宽，所以请求头再加个

     request.Headers.Add("Accept-Encoding", " gzip, deflate, br");

相应的得到相应流要有相对应的解压，这个时候httphelper变成这样了

           public static string DownLoadString(string url)
            {
                 string Source = string.Empty;
                 try{    
                 HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
                request.UserAgent = "Mozilla/5.0 (Windows NT 10.0; WOW64; rv:49.0) Gecko/20100101 Firefox/49.0";
       
                request.Headers.Add("Cookie", "这里是Cookie");
         
                request.Headers.Add("Accept-Encoding", " gzip, deflate, br");
                request.KeepAlive = true;//启用长连接
         
                using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
                {

                    using (Stream dataStream = response.GetResponseStream())
                    {

                        if (response.ContentEncoding.ToLower().Contains("gzip"))//解压
                        {
                            using (GZipStream stream = new GZipStream(response.GetResponseStream(), CompressionMode.Decompress))
                            {
                                using (StreamReader reader = new StreamReader(stream, Encoding.UTF8))
                                {
                                    Source = reader.ReadToEnd();
                                }
                            }
                        }
                        else if (response.ContentEncoding.ToLower().Contains("deflate"))//解压
                        {
                            using (DeflateStream stream = new DeflateStream(response.GetResponseStream(), CompressionMode.Decompress))
                            {
                                using (StreamReader reader = new StreamReader(stream, Encoding.UTF8))
                                {
                                    Source = reader.ReadToEnd();
                                }

                            }
                        }
                        else
                        {
                            using (Stream stream = response.GetResponseStream())//原始
                            {
                                using (StreamReader reader = new StreamReader(stream, Encoding.UTF8))
                                {

                                    Source = reader.ReadToEnd();
                                }
                            }
                        }

                    }
                }
                request.Abort();
            }
            catch
            {
                Console.WriteLine("出错了，请求的URL为{0}", url);

            }
            return Source;
}

请求态度会被服务器拒绝，返回429。这个时候需要设置代理，我们的请求会提交到代理服务器，代理服务器会向目标服务器请求，得到的响应由代理服务器返回给我们。只要不断切换代理，服务器不会因为请求太频繁而拒绝掉程序的请求

   var proxy = new WebProxy(“Adress”,8080);//后面是端口号
   request.Proxy = proxy;//为httpwebrequest设置代理

 原理是

我使用的是一家叫阿布云的服务商，提供的服务比较稳定优质，就是有点贵，根据阿布云官网的示例代理，我将httphelp修改成了

   public static string DownLoadString(string url)
        {
            string Source = string.Empty;
            try
            {
                  string proxyHost = "http://proxy.abuyun.com";
                      string proxyPort = "9020";
            // 代理隧道验证信息
                       string proxyUser = "H71T6AMK7GREN0JD";
                        string proxyPass = "D3F01F3AEFE4E45A";
         


            var proxy = new WebProxy();
            proxy.Address = new Uri(string.Format("{0}:{1}", proxyHost, proxyPort));
            proxy.Credentials = new NetworkCredential(proxyUser, proxyPass);

            ServicePointManager.Expect100Continue = false;

                Stopwatch watch = new Stopwatch();
                watch.Start();
                HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
                request.UserAgent = "Mozilla/5.0 (Windows NT 10.0; WOW64; rv:49.0) Gecko/20100101 Firefox/49.0";
             
                request.Headers.Add("Cookie", "q_c1=17d0e600b6974387b1bc3a0117d21c50|1483348502000|1483348502000; l_cap_id="NjVhNGM1ODhmZWJlNDE4MDk1OTRlMDU0NTRmMmU3NzY=|1483348502|ce7951227c840cde8d8356526547cfeddece44a8"; cap_id="Y2QyODU3MTg0NTViNDIwZTk4YmRhMTk5YWI5MTY1MGQ=|1483348502|892544d61b1d04265cad1ad172a5911eaf47ebe2"; d_c0="AEAC7iaxFwuPToc2DY_goP_H5QnNPxMReuU=|1483348504"; r_cap_id="ODA5ZDI5YTQ1M2E2NDc1OWJlMjk0Nzk1ZWY4ZjQ1NTU=|1483348505|00d0a93219de27de0e9dfa2c2a6cbe0cbf7c0a36"; _zap=ea616f49-be5d-4f94-98d8-fdec8f7d277b; __utma=51854390.2059985006.1483348508.1483348508.1483416071.2; __utmz=51854390.1483416071.2.2.utmcsr=baidu|utmccn=(organic)|utmcmd=organic; __utmv=51854390.100-1|2=registration_date=20160110=1^3=entry_date=20160110=1; login="ZDczZTgyMmUzZjY1NDQ1YTkzMDk2MTk5MTNjMDIxMTM=|1483348523|f1e570e14ceed6b61720c413dd8663527aea78fc"; z_c0=Mi4wQUJCS0c2ZmVTUWtBUUFMdUpyRVhDeGNBQUFCaEFsVk5LNmVSV0FEc1hkcFV2YUdOaDExVjBTLU1KNVZ6OFRYcC1n|1483416083|3e5d60bef695bd722a95aea50f066c394cfcba9d; _xsrf=87b1049f227fe734a9577ec9f76342b3; __utmb=51854390.0.10.1483416071; __utmc=51854390");
                request.Headers.Add("Upgrade-Insecure-Requests", "1");
                request.Headers.Add("Cache-Control", "no-cach");
                request.Accept = "*/*";
                request.Method = "GET";
                request.Referer = "https://www.zhihu.com/";
                request.Headers.Add("Accept-Encoding", " gzip, deflate, br");
                request.KeepAlive = true;//启用长连接
                request.Proxy = proxy;
                using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
                {

                    using (Stream dataStream = response.GetResponseStream())
                    {

                        if (response.ContentEncoding.ToLower().Contains("gzip"))//解压
                        {
                            using (GZipStream stream = new GZipStream(response.GetResponseStream(), CompressionMode.Decompress))
                            {
                                using (StreamReader reader = new StreamReader(stream, Encoding.UTF8))
                                {
                                    Source = reader.ReadToEnd();
                                }
                            }
                        }
                        else if (response.ContentEncoding.ToLower().Contains("deflate"))//解压
                        {
                            using (DeflateStream stream = new DeflateStream(response.GetResponseStream(), CompressionMode.Decompress))
                            {
                                using (StreamReader reader = new StreamReader(stream, Encoding.UTF8))
                                {
                                    Source = reader.ReadToEnd();
                                }

                            }
                        }
                        else
                        {
                            using (Stream stream = response.GetResponseStream())//原始
                            {
                                using (StreamReader reader = new StreamReader(stream, Encoding.UTF8))
                                {

                                    Source = reader.ReadToEnd();
                                }
                            }
                        }

                    }
                }
                request.Abort();
                watch.Stop();
                Console.WriteLine("请求网页用了{0}毫秒", watch.ElapsedMilliseconds.ToString());
            }
            catch
            {
                Console.WriteLine("出错了，请求的URL为{0}", url);

            }
            return Source;
        }