C#网络爬虫--多线程处理强化版

上次做了一个帮公司妹子做了爬虫，不是很精致，这次公司项目里要用到，于是有做了一番修改，功能添加了网址图片采集，下载，线程处理界面网址图片下载等。

说说思路：首相获取初始网址的所有内容在初始网址采集图片去初始网址采集链接把采集到的链接放入队列继续采集图片，然后继续采集链接，无限循环

还是上图片大家看一下，在上代码！

处理网页内容抓取跟网页网址爬取都做了改进，下面还是大家来看看代码，有不足之处，还请之处!

网页内容抓取HtmlCodeRequest,

网页网址爬取GetHttpLinks，用正则去筛选html中的Links

图片抓取GetHtmlImageUrlList，用正则去筛选html中的Img

都写进了一个封装类里面 HttpHelper

    /// <summary>   
        /// 取得HTML中所有图片的 URL。   
        /// </summary>   
        /// <param name="sHtmlText">HTML代码</param>   
        /// <returns>图片的URL列表</returns> 
public static string HtmlCodeRequest(string Url)
        {
            if (string.IsNullOrEmpty(Url))
            {
                return "";
            }
            try
            {
                //创建一个请求
                HttpWebRequest httprequst = (HttpWebRequest)WebRequest.Create(Url);
                //不建立持久性链接
                httprequst.KeepAlive = true;
                //设置请求的方法
                httprequst.Method = "GET";
                //设置标头值
                httprequst.UserAgent = "User-Agent:Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.2; .NET CLR 1.0.3705";
                httprequst.Accept = "*/*";
                httprequst.Headers.Add("Accept-Language", "zh-cn,en-us;q=0.5");
                httprequst.ServicePoint.Expect100Continue = false;
                httprequst.Timeout = 5000;
                httprequst.AllowAutoRedirect = true;//是否允许302
                ServicePointManager.DefaultConnectionLimit = 30;
                //获取响应
                HttpWebResponse webRes = (HttpWebResponse)httprequst.GetResponse();
                //获取响应的文本流
                string content = string.Empty;
                using (System.IO.Stream stream = webRes.GetResponseStream())
                {
                    using (System.IO.StreamReader reader = new StreamReader(stream, System.Text.Encoding.GetEncoding("utf-8")))
                    {
                        content = reader.ReadToEnd();
                    }
                }
                //取消请求
                httprequst.Abort();
                //返回数据内容
                return content;
            }
            catch (Exception)
            {

                return "";
            }
        }
/// <summary>
        /// 提取页面链接
        /// </summary>
        /// <param name="html"></param>
        /// <returns></returns>
public static List<string> GetHtmlImageUrlList(string url)
        {
            string html = HttpHelper.HtmlCodeRequest(url);
            if (string.IsNullOrEmpty(html))
            {
                return new List<string>();
            }
            // 定义正则表达式用来匹配 img 标签   
            Regex regImg = new Regex(@"<img\b[^<>]*?\bsrc[\s\t\r\n]*=[\s\t\r\n]*[""']?[\s\t\r\n]*(?<imgUrl>[^\s\t\r\n""'<>]*)[^<>]*?/?[\s\t\r\n]*>", RegexOptions.IgnoreCase);

            // 搜索匹配的字符串   
            MatchCollection matches = regImg.Matches(html);
            List<string> sUrlList = new List<string>();

            // 取得匹配项列表   
            foreach (Match match in matches)
                sUrlList.Add(match.Groups["imgUrl"].Value);
            return sUrlList;
        }


        /// <summary>
        /// 提取页面链接
        /// </summary>
        /// <param name="html"></param>
        /// <returns></returns>
        public static List<string> GetHttpLinks(string url)
        {
            //获取网址内容
            string html = HttpHelper.HtmlCodeRequest(url);
            if (string.IsNullOrEmpty(html))
            {
                return new List<string>();
            }
            //匹配http链接
            const string pattern2 = @"http(s)?://([\w-]+\.)+[\w-]+(/[\w- ./?%&=]*)?";
            Regex r2 = new Regex(pattern2, RegexOptions.IgnoreCase);
            //获得匹配结果
            MatchCollection m2 = r2.Matches(html);
            List<string> links = new List<string>();
            foreach (Match url2 in m2)
            {
                if (StringHelper.CheckUrlIsLegal(url2.ToString()) || !StringHelper.IsPureUrl(url2.ToString()) || links.Contains(url2.ToString()))
                    continue;
                links.Add(url2.ToString());
            }
            //匹配href里面的链接
            const string pattern = @"(?i)<a\s[^>]*?href=(['""]?)(?!javascript|__doPostBack)(?<url>[^'""\s*#<>]+)[^>]*>"; ;
            Regex r = new Regex(pattern, RegexOptions.IgnoreCase);
            //获得匹配结果
            MatchCollection m = r.Matches(html);
            foreach (Match url1 in m)
            {
                string href1 = url1.Groups["url"].Value;
                if (!href1.Contains("http"))
                {
                    href1 = Global.WebUrl + href1;
                }
                if (!StringHelper.IsPureUrl(href1) || links.Contains(href1)) continue;
                links.Add(href1);
            }
            return links;
        }

这边下载图片有个任务条数限制，限制是200条。如果超过的话线程等待5秒，这里下载图片是异步调用的委托

public string DownLoadimg(string url)
        {
            if (!string.IsNullOrEmpty(url))
            {
                try
                {
                    if (!url.Contains("http"))
                    {
                        url = Global.WebUrl + url;
                    }
                    HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
                    request.Timeout = 2000;
                    request.UserAgent = "User-Agent:Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.2; .NET CLR 1.0.3705";
                    //是否允许302
                    request.AllowAutoRedirect = true;
                    WebResponse response = request.GetResponse();
                    Stream reader = response.GetResponseStream();
                    //文件名
                    string aFirstName = Guid.NewGuid().ToString();
                    //扩展名
                    string aLastName = url.Substring(url.LastIndexOf(".") + 1, (url.Length - url.LastIndexOf(".") - 1));
                    FileStream writer = new FileStream(Global.FloderUrl + aFirstName + "." + aLastName, FileMode.OpenOrCreate, FileAccess.Write);
                    byte[] buff = new byte[512];
                    //实际读取的字节数
                    int c = 0;
                    while ((c = reader.Read(buff, 0, buff.Length)) > 0)
                    {
                        writer.Write(buff, 0, c);
                    }
                    writer.Close();
                    writer.Dispose();
                    reader.Close();
                    reader.Dispose();
                    response.Close();
                    return (aFirstName + "." + aLastName);
                }
                catch (Exception)
                {
                    return "错误：地址" + url;
                }
            }
            return "错误：地址为空";
        }