| 抓取網頁中的鏈接 |
| 作者：孟憲會 出自：【孟憲會之精彩世界】 發佈日期：2003年5月1日 7點4分24秒 |
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輸入一個地址，就可以把那個網頁中的鏈接提取出來，下面這段代碼可以輕鬆實現，主要的是用到了正則表達式。 GetUrl.aspx代碼如下： <%@ Page Language="vb" CodeBehind="GetUrl.aspx.vb" AutoEventWireup="false" Inherits="aspxWeb.GetUrl" %> <html> <head> <META http-equiv="content-type" content="text/html; charset=gb2312"> </head> <body> <form id="Form1" method="post" runat="server"> <P> <asp:Label id="Label1" runat="server"></asp:Label> <asp:TextBox id="urlTextBox" runat="server" Width="336px"> http://lucky_elove.www1.dotnetplayground.com/ </asp:TextBox> <asp:Button OnClick="scrapeButton_Click" id="scrapeButton" runat="server"></asp:Button> </P> <HR width="100%" SIZE="1"> <P> <asp:Label id="TipResult" runat="server"></asp:Label> <asp:TextBox id="resultLabel" runat="server" TextMode="MultiLine" Width="100%" Height="400"></asp:TextBox> </P> </form> </body> </html>後代碼GetUrl.aspx.vb如下： Imports System.IO Imports System.Net Imports System.Text Imports System.Text.RegularExpressions Imports System Public Class GetUrl Inherits System.Web.UI.Page Protected WithEvents Label1 As System.Web.UI.WebControls.Label Protected WithEvents urlTextBox As System.Web.UI.WebControls.TextBox Protected WithEvents scrapeButton As System.Web.UI.WebControls.Button Protected WithEvents TipResult As System.Web.UI.WebControls.Label Protected WithEvents resultLabel As System.Web.UI.WebControls.TextBox #Region " Web 窗體設計器生成的代碼 " '該調用是 Web 窗體設計器所必需的。 <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent() End Sub Private Sub Page_Init(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Init 'CODEGEN: 此方法調用是 Web 窗體設計器所必需的 '不要使用代碼編輯器修改它。 InitializeComponent() End Sub #End Region Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load '在此處放置初始化頁的用戶代碼 Label1.Text = "請輸入一個URL地址：" scrapeButton.Text = "分離Href鏈接" End Sub Private report As New StringBuilder() Private webPage As String Private countOfMatches As Int32 Public Sub scrapeButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) webPage = GrabUrl() Dim myDelegate As New MatchEvaluator(AddressOf MatchHandler) Dim linksExpression As New Regex( _ "/<a.+?href=['""](?!http/:////)(?!mailto/:)(?>foundAnchor>[^'"">]+?)[^>]*?/>", _ RegexOptions.Multiline Or RegexOptions.IgnoreCase Or RegexOptions.IgnorePatternWhitespace) Dim newWebPage As String = linksExpression.Replace(webPage, myDelegate) TipResult.Text = "<h2>從 " & urlTextBox.Text & "分離出的Href鏈接</h2>" & _ "<b>找到並整理" & countOfMatches.ToString() & " 個鏈接</b><br><br>" & _ report.ToString().Replace(Environment.NewLine, "<br>") TipResult.Text &= "<h2>整理過的頁面</h2><script>window.document.title='抓取網頁中的鏈接'</script>" resultLabel.Text = newWebPage End Sub Public Function MatchHandler(ByVal m As Match) As String Dim link As String = m.Groups("foundAnchor").Value Dim rToL As New Regex("^", RegexOptions.Multiline Or RegexOptions.RightToLeft) Dim col, row As Int32 Dim lineBegin As Int32 = rToL.Match(webPage, m.Index).Index row = rToL.Matches(webPage, m.Index).Count col = m.Index - lineBegin report.AppendFormat( _ "Link <b>{0}</b>, fixed at row: {1}, col: {2}{3}", _ Server.HtmlEncode(m.Groups(0).Value), _ row, _ col, _ Environment.NewLine _ ) Dim newLink As String If link.StartsWith("/") Then newLink = link.Substring(1) Else newLink = link End If countOfMatches += 1 Return m.Groups(0).Value.Replace(link, newLink) End Function Private Function GrabUrl() As String Dim wc As New WebClient() Dim s As Stream = wc.OpenRead(urlTextBox.Text) Dim sr As StreamReader = New StreamReader(s, System.Text.Encoding.Default) GrabUrl = sr.ReadToEnd s.Close() wc.Dispose() End Function End Class |
抓取網頁中的鏈接
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