本文实例讲述了C#基于正则表达式实现获取网页中所有信息的网页抓取类。分享给大家供大家参考，具体如下：
类的代码：
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using System;using System.Data;using System.Configuration;using System.Net;using System.IO;using System.Text;using System.Collections.Generic;using System.Text.RegularExpressions;using System.Threading;using System.Web;using System.Web.UI.MobileControls;/// <summary>/// 网页类/// </summary>public class WebPage{ #region 私有成员 private Uri m_uri; //url private List<Link> m_links; //此网页上的链接 private string m_title; //标题 private string m_html; //HTML代码 private string m_outstr; //网页可输出的纯文本 private bool m_good; //网页是否可用 private int m_pagesize; //网页的大小 private static Dictionary<string, CookieContainer> webcookies = new Dictionary<string, CookieContainer>();//存放所有网页的Cookie #endregion #region 属性 /// <summary> /// 通过此属性可获得本网页的网址，只读 /// </summary> public string URL { get { return m_uri.AbsoluteUri; } } /// <summary> /// 通过此属性可获得本网页的标题，只读 /// </summary> public string Title { get { if (m_title == "") { Regex reg = new Regex(@"(?m)<title[^>]*>(?<title>(?:\w|\W)*?)</title[^>]*>", RegexOptions.Multiline | RegexOptions.IgnoreCase); Match mc = reg.Match(m_html); if (mc.Success) m_title = mc.Groups["title"].Value.Trim(); } return m_title; } } public string M_html { get { if (m_html == null) { m_html = ""; } return m_html; } } /// <summary> /// 此属性获得本网页的所有链接信息，只读 /// </summary> public List<Link> Links { get { if (m_links.Count == 0) getLinks(); return m_links; } } /// <summary> /// 此属性返回本网页的全部纯文本信息，只读 /// </summary> public string Context { get { if (m_outstr == "") getContext(Int16.MaxValue); return m_outstr; } } /// <summary> /// 此属性获得本网页的大小 /// </summary> public int PageSize { get { return m_pagesize; } } /// <summary> /// 此属性获得本网页的所有站内链接 /// </summary> public List<Link> InsiteLinks { get { return getSpecialLinksByUrl("^http://" + m_uri.Host, Int16.MaxValue); } } /// <summary> /// 此属性表示本网页是否可用 /// </summary> public bool IsGood { get { return m_good; } } /// <summary> /// 此属性表示网页的所在的网站 /// </summary> public string Host { get { return m_uri.Host; } } #endregion /// <summary> /// 从HTML代码中分析出链接信息 /// </summary> /// <returns>List<Link></returns> private List<Link> getLinks() { if (m_links.Count == 0) { Regex[] regex = new Regex[2]; regex[0] = new Regex(@"<a\shref\s*=""(?<URL>[^""]*).*?>(?<title>[^<]*)</a>", RegexOptions.IgnoreCase | RegexOptions.Singleline); regex[1] = new Regex("<[i]*frame[^><]+src=(\"|')?(?<url>([^>\"'\\s)])+)(\"|')?[^>]*>", RegexOptions.IgnoreCase); for (int i = 0; i < 2; i++) { Match match = regex[i].Match(m_html); while (match.Success) { try { string url = HttpUtility.UrlDecode(new Uri(m_uri, match.Groups["URL"].Value).AbsoluteUri); string text = ""; if (i == 0) text = new Regex("(<[^>]+>)|(\\s)|( )|&|\"", RegexOptions.Multiline | RegexOptions.IgnoreCase).Replace(match.Groups["text"].Value, ""); Link link = new Link(); link.Text = text; link.NavigateUrl = url; m_links.Add(link); } catch (Exception ex) { Console.WriteLine(ex.Message); }; match = match.NextMatch(); } } } return m_links; } /// <summary> /// 此私有方法从一段HTML文本中提取出一定字数的纯文本 /// </summary> /// <param name="instr">HTML代码</param> /// <param name="firstN">提取从头数多少个字</param> /// <param name="withLink">是否要链接里面的字</param> /// <returns>纯文本</returns> private string getFirstNchar(string instr, int firstN, bool withLink) { if (m_outstr == "") { m_outstr = instr.Clone() as string; m_outstr = new Regex(@"(?m)<script[^>]*>(\w|\W)*?</script[^>]*>", RegexOptions.Multiline | RegexOptions.IgnoreCase).Replace(m_outstr, ""); m_outstr = new Regex(@"(?m)<style[^>]*>(\w|\W)*?</style[^>]*>", RegexOptions.Multiline | RegexOptions.IgnoreCase).Replace(m_outstr, ""); m_outstr = new Regex(@"(?m)<select[^>]*>(\w|\W)*?</select[^>]*>", RegexOptions.Multiline | RegexOptions.IgnoreCase).Replace(m_outstr, ""); if (!withLink) m_outstr = new Regex(@"(?m)<a[^>]*>(\w|\W)*?</a[^>]*>", RegexOptions.Multiline | RegexOptions.IgnoreCase).Replace(m_outstr, ""); Regex objReg = new System.Text.RegularExpressions.Regex("(<[^>]+?>)| ", RegexOptions.Multiline | RegexOptions.IgnoreCase); m_outstr = objReg.Replace(m_outstr, ""); Regex objReg2 = new System.Text.RegularExpressions.Regex("(\\s)+", RegexOptions.Multiline | RegexOptions.IgnoreCase); m_outstr = objReg2.Replace(m_outstr, " "); } return m_outstr.Length > firstN ? m_outstr.Substring(0, firstN) : m_outstr; } #region 公有文法 /// <summary> /// 此公有方法提取网页中一定字数的纯文本，包括链接文字 /// </summary> /// <param name="firstN">字数</param> /// <returns></returns> public string getContext(int firstN) { return getFirstNchar(m_html, firstN, true); } /// <summary> /// 此公有方法从本网页的链接中提取一定数量的链接，该链接的URL满足某正则式 /// </summary> /// <param name="pattern">正则式</param> /// <param name="count">返回的链接的个数</param> /// <returns>List<Link></returns> public List<Link> getSpecialLinksByUrl(string pattern, int count) { if (m_links.Count == 0) getLinks(); List<Link> SpecialLinks = new List<Link>(); List<Link>.Enumerator i; i = m_links.GetEnumerator(); int cnt = 0; while (i.MoveNext() && cnt < count) { if (new Regex(pattern, RegexOptions.Multiline | RegexOptions.IgnoreCase).Match(i.Current.NavigateUrl).Success) { SpecialLinks.Add(i.Current); cnt++; } } return SpecialLinks; } /// <summary> /// 此公有方法从本网页的链接中提取一定数量的链接，该链接的文字满足某正则式 /// </summary> /// <param name="pattern">正则式</param> /// <param name="count">返回的链接的个数</param> /// <returns>List<Link></returns> public List<Link> getSpecialLinksByText(string pattern, int count) { if (m_links.Count == 0) getLinks(); List<Link> SpecialLinks = new List<Link>(); List<Link>.Enumerator i; i = m_links.GetEnumerator(); int cnt = 0; while (i.MoveNext() && cnt < count) { if (new Regex(pattern, RegexOptions.Multiline | RegexOptions.IgnoreCase).Match(i.Current.Text).Success) { SpecialLinks.Add(i.Current); cnt++; } } return SpecialLinks; } /// <summary> /// 这公有方法提取本网页的纯文本中满足某正则式的文字 by 何问起 /// </summary> /// <param name="pattern">正则式</param> /// <returns>返回文字</returns> public string getSpecialWords(string pattern) { if (m_outstr == "") getContext(Int16.MaxValue); Regex regex = new Regex(pattern, RegexOptions.Multiline | RegexOptions.IgnoreCase); Match mc = regex.Match(m_outstr); if (mc.Success) return mc.Groups[1].Value; return string.Empty; } #endregion #region 构造函数 private void Init(string _url) { try { m_uri = new Uri(_url); m_links = new List<Link>(); m_html = ""; m_outstr = ""; m_title = ""; m_good = true; if (_url.EndsWith(".rar") || _url.EndsWith(".dat") || _url.EndsWith(".msi")) { m_good = false; return; } HttpWebRequest rqst = (HttpWebRequest)WebRequest.Create(m_uri); rqst.AllowAutoRedirect = true; rqst.MaximumAutomaticRedirections = 3; rqst.UserAgent = "Mozilla/4.0 (compatible; MSIE 5.01; Windows NT 5.0)"; rqst.KeepAlive = true; rqst.Timeout = 10000; lock (WebPage.webcookies) { if (WebPage.webcookies.ContainsKey(m_uri.Host)) rqst.CookieContainer = WebPage.webcookies[m_uri.Host]; else { CookieContainer cc = new CookieContainer(); WebPage.webcookies[m_uri.Host] = cc; rqst.CookieContainer = cc; } } HttpWebResponse rsps = (HttpWebResponse)rqst.GetResponse(); Stream sm = rsps.GetResponseStream(); if (!rsps.ContentType.ToLower().StartsWith("text/") || rsps.ContentLength > 1 << 22) { rsps.Close(); m_good = false; return; } Encoding cding = System.Text.Encoding.Default; string contenttype = rsps.ContentType.ToLower(); int ix = contenttype.IndexOf("charset="); if (ix != -1) { try { cding = System.Text.Encoding.GetEncoding(rsps.ContentType.Substring(ix + "charset".Length + 1)); } catch { cding = Encoding.Default; } //该处视情况而定 有的需要解码 //m_html = HttpUtility.HtmlDecode(new StreamReader(sm, cding).ReadToEnd()); m_html = new StreamReader(sm, cding).ReadToEnd(); } else { //该处视情况而定 有的需要解码 //m_html = HttpUtility.HtmlDecode(new StreamReader(sm, cding).ReadToEnd()); m_html = new StreamReader(sm, cding).ReadToEnd(); Regex regex = new Regex("charset=(?<cding>[^=]+)?\"", RegexOptions.IgnoreCase); string strcding = regex.Match(m_html).Groups["cding"].Value; try { cding = Encoding.GetEncoding(strcding); } catch { cding = Encoding.Default; } byte[] bytes = Encoding.Default.GetBytes(m_html.ToCharArray()); m_html = cding.GetString(bytes); if (m_html.Split('?').Length > 100) { m_html = Encoding.Default.GetString(bytes); } } m_pagesize = m_html.Length; m_uri = rsps.ResponseUri; rsps.Close(); } catch (Exception ex) { } } public WebPage(string _url) { string uurl = ""; try { uurl = Uri.UnescapeDataString(_url); _url = uurl; } catch { }; Init(_url); } #endregion} |
调用：
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WebPage webInfo = new WebPage("http://hovertree.net/");webInfo.Context;//不包含html标签的所有内容webInfo.M_html;//包含html标签的内容 by 何问起 |
希望本文所述对大家C#程序设计有所帮助。
