C#实现web信息抓取

随着Internet的普及，网络信息正以极高的速度增长，在这么多数据中找到自己需要的信息是一件很繁琐的事情，找到需要的信息后如何获取也是件麻烦的事。这就需要Internet信息抓取程序来代替人工的操作。

所谓Internet信息抓取程序，就是程序会按照用户的关键词或关键网站来收集相应的信息，并提供给用户想要的信息格式。

信息量的增加会带来信息网站发布人员工作量的剧增，为实现信息发布系统实现信息自

动发布、减少工作人员工作量、即时跟踪最新信息，就需要自动信息提供程序，因此Internet信息抓取程序应运而生。

目标

实现自定义网站信息分类抓取，存入本地数据库、生成静态页面或其它用户定义的信息结构，并下载与信息相关的多媒体文件。

开发

l 目标站点结构分析

本步骤是准确抓取信息个关键。

首先要选择更新频率高的页面做为抓取地址，然后分析要抓取内容页面url特点。

然后分析要抓取信息页面的元素特性，比如标题位置，内容位置等，得到定位标记点。

将以上信息写成自己的配置文件或存到数据库中。

每个网站都需要分析，写出单独的配置文件，供抓取程序使用。

l 信息提取

根据配置文件取得要抓取页面url，使用HttpWebRequest类获取内容：

//获取http页面函数

public string Get_Http(string a_strUrl,int timeout)

{

string strResult ;

try

{

HttpWebRequest myReq =

(HttpWebRequest)HttpWebRequest.Create(a_strUrl) ;

myReq.Timeout = timeout;

HttpWebResponse HttpWResp =

(HttpWebResponse)myReq.GetResponse();

Stream myStream = HttpWResp.GetResponseStream () ;

StreamReader sr = new StreamReader(myStream ,

Encoding.Default);

StringBuilder strBuilder = new StringBuilder();

while (-1 != sr.Peek())

{

strBuilder.Append(sr.ReadLine()+"\r\n");

}

strResult = strBuilder.ToString();

}

catch(Exception exp)

{

strResult = "错误：" + exp.Message ;

}

return strResult ;

}

获取页面内容后，分析页面中连接地址取到要抓取的url：

//处理页面标题和链接

public string SniffWebUrl( string urlStr,string

blockB,string blockE )

{

string urlch1 = "";

string urlch2 = "";

int end_n1 = 0;

int end_nums = 0;

int end_nums1 = 0;

int end_nums2 = 0;

int end_nums3 = 0;

string reUTStr = "";

string reTitle = "";

string ret = "";

try

{

int pos01 = urlStr.IndexOf( "." );

int pos02 = urlStr.LastIndexOf( "/" );

if( pos01 < 0 )

{

return "";

}

if( pos02 < 0 )

{

return "";

}

int pos03 = urlStr.IndexOf( "/",pos01 );

if ( pos03 < 0 )

{

urlch1 = urlStr;

urlch2 = urlStr;

}

else

{

urlch1 = urlStr.Substring( 0,pos03 );

urlch2 = urlStr.Substring( 0,pos02 );

}

string tmpAllStr = new PublicFun().Get_Http( urlStr

,time1);

int pos1 = tmpAllStr.IndexOf( blockB );

int pos2 = tmpAllStr.IndexOf( blockE,pos1 +

blockB.Length );

if ( pos1>0 && pos2>0 && pos2>pos1 )

{

ret = tmpAllStr.Substring( pos1 +

blockB.Length,pos2 - pos1 - blockB.Length );

ret = ret.Substring( ret.IndexOf( "<" ));

while( ret.IndexOf( "<A" ) >= 0 )

{

ret = ret.Substring( 0,ret.IndexOf( "<A" ) )

+ "<a" + ret.Substring( ret.IndexOf( "<A" ) + 2 );

}

while( ret.IndexOf( "</A" ) >=0 )

{

ret = ret.Substring( 0,ret.IndexOf( "</A" )

) + "</a" + ret.Substring( ret.IndexOf( "</A" ) + 3 );

}

while( ret.IndexOf( "Href=" ) >=0 )

{

ret = ret.Substring( 0,ret.IndexOf( "Href="

)) + "href=" + ret.Substring( ret.IndexOf( "Href=" ) + 5 );

}

while( ret.IndexOf( "HREF=" ) >=0 )

{

ret = ret.Substring( 0,ret.IndexOf( "HREF="

)) + "href=" + ret.Substring( ret.IndexOf( "HREF=" ) + 5 );

}

while( ret.IndexOf( "href='" ) >=0 )

{

ret = ret.Substring( 0,ret.IndexOf( "href='"

)) + "href=\"" + ret.Substring( ret.IndexOf( "href='" ) + 6 );

}

tmpAllStr = ret;

int begin_nums = tmpAllStr.IndexOf( "href=" );

while ( begin_nums >= 0 )

{

string tmpStrA = "";

string tmpStrB = tmpAllStr.Substring( begin_nums

+ 5,1 );

if ( tmpStrB == "\"" )

{

end_n1 = begin_nums + 6;

if ( ( end_n1 + 1 ) > tmpAllStr.Length )

{

return "";

}

tmpStrA = tmpAllStr.Substring(

begin_nums+6,1 );

}

else

{

end_n1 = begin_nums + 5;

tmpStrA = tmpStrB;

}

if ( tmpStrA == "#" )

{

tmpAllStr = tmpAllStr.Substring( end_n1 );

begin_nums = tmpAllStr.IndexOf( "href=" );

}

else

{

end_nums1 = tmpAllStr.IndexOf( " ",end_n1 );

end_nums2 = tmpAllStr.IndexOf( ">",end_n1 );

end_nums3 = tmpAllStr.IndexOf(

"</a",end_nums2 );

if ( ( end_nums3 >= 0 ) && ( end_nums2 >= 0

) )

{

reTitle = tmpAllStr.Substring( end_nums2

+ 1,end_nums3 - end_nums2 - 1 );

if ( end_nums1 > end_nums2 )

{

end_nums = end_nums2;

}

else

{

if ( end_nums1 < 0 )

{

end_nums = end_nums2;

}

else

{

end_nums = end_nums1;

}

string str4 = tmpAllStr.Substring(

end_nums-1, end_nums - end_nums + 1 );

if ( str4 =="\"" || str4 == "'" )

{

end_nums = end_nums - 1;

}

string sTotalOne = tmpAllStr.Substring(

end_n1,end_nums - end_n1 );

if ( sTotalOne.IndexOf( "http://" ) <0 )

{

if ( sTotalOne.IndexOf( "/" ) == 0 )

{

sTotalOne = urlch1 + sTotalOne;

}

else

{

int linshiIntNum = 0;

int flags = 0;

string urlChange = urlStr;;

while( sTotalOne.IndexOf( "../"

) >= 0 )

{

sTotalOne =

sTotalOne.Substring( sTotalOne.IndexOf( "../" ) + 3 );

linshiIntNum = linshiIntNum

+ 1;

flags = flags +1;

}

while( ( urlChange.LastIndexOf(

"/" ) >= 0 ) && ( linshiIntNum >= 0 ) )

{

urlChange =

urlChange.Substring( 0,urlChange.LastIndexOf( "/" ) );

linshiIntNum = linshiIntNum

- 1;

}

if ( flags == 0 )

{

sTotalOne = urlch2 + "/" +

sTotalOne;

}

else

{

sTotalOne = urlChange + "/"

+ sTotalOne;

}

reUTStr = reUTStr + new

PublicFun().RemoveHtmlCode( reTitle ) + sTotalOne;

tmpAllStr = tmpAllStr.Substring(

end_nums3 + 4 );

begin_nums = tmpAllStr.IndexOf( "href="

);

}

else

{

begin_nums = -1;

}

return reUTStr;

}

catch( Exception e)

{

return "";

}

得到要抓取内容的url后，处理该页面：

//获取链接内容并分类处理

public string GetWebContent( string gatherUrl,string

subUrl,string subTitle,string b_Content,string e_Content,string

b_Filter,string e_Filter,string root )

{

string tmpAllStr = "";

string dfStrB = "";

string dfStrE = "";

string rePicStr = "";//图片返回路径

string reContentStr = "";

string picHtml = "images"; //本地图片路径

string urlch1 ="";

string urlch2 ="";

int pos1 = gatherUrl.IndexOf( "." );

int pos2 = gatherUrl.LastIndexOf( "/" );

if( pos1 < 0 )

{

return "";

}

if( pos2 < 0 )

{

return "";

}

int pos3 = gatherUrl.IndexOf( "/",pos1 );

if ( pos3 < 0 )

{

urlch1 = gatherUrl;

urlch2 = gatherUrl;

}

else

{

urlch1 = gatherUrl.Substring( 0,pos3 );

urlch2 = gatherUrl.Substring( 0,pos2 );

}

tmpAllStr = new PublicFun().Get_Http( subUrl,time1 );

//取稿源

string docFromStr = "";

if ( dfStrB != "" && dfStrE != "" )

{

if ( tmpAllStr != "" )

{

int b_docF = tmpAllStr.IndexOf( dfStrB );

if ( b_docF > 0 )

{

int e_docF = tmpAllStr.IndexOf(

dfStrE,b_docF + dfStrB.Length );

if ( e_docF > 0 && e_docF > b_docF && e_docF

- b_docF < 20 )

{

docFromStr = tmpAllStr.Substring( b_docF

+ dfStrB.Length, e_docF - b_docF - dfStrB.Length );

}

//取内容

if ( tmpAllStr != "" )

{

int begin_strnum = tmpAllStr.IndexOf( b_Content );

if ( begin_strnum < 0 )

{

return "";

}

int end_strnum = tmpAllStr.IndexOf(

e_Content,begin_strnum + b_Content.Length );

if ( end_strnum < 0 )

{

return "";

}

string sTotalSubM = "";

if ( end_strnum > begin_strnum )

{

sTotalSubM = tmpAllStr.Substring (

begin_strnum,end_strnum - begin_strnum );

}

if ( sTotalSubM == "" )

{

return "";

}

//过滤无用信息

int bfnum = sTotalSubM.IndexOf( b_Filter );

if ( bfnum > -1 )

{

int efnum = sTotalSubM.IndexOf( e_Filter,bfnum

);

if ( efnum > -1 )

{

if ( efnum > bfnum )

{

sTotalSubM = sTotalSubM.Substring(

0,bfnum ) + sTotalSubM.Substring( efnum + e_Filter.Length );

}

//格式化图片标记

while( sTotalSubM.IndexOf( "Src=" ) >= 0 )

{

sTotalSubM = sTotalSubM.Substring(

0,sTotalSubM.IndexOf( "Src=" ) ) + "src=" + sTotalSubM.Substring(

sTotalSubM.IndexOf( "Src=" ) + 4 );

}

while( sTotalSubM.IndexOf( "SRC=" ) >= 0 )

{

sTotalSubM = sTotalSubM.Substring(

0,sTotalSubM.IndexOf( "SRC=" ) ) + "src=" + sTotalSubM.Substring(

sTotalSubM.IndexOf( "SRC=" ) + 4 );

}

while( sTotalSubM.IndexOf( "src='" ) >= 0 )

{

sTotalSubM = sTotalSubM.Substring(

0,sTotalSubM.IndexOf( "src='" ) ) + "src=\"" + sTotalSubM.Substring(

sTotalSubM.IndexOf( "src='" ) + 5 );

}

//取图片地址

int end_n12 = 0;

int end_nums2 = 0;

int begin_nums2 = sTotalSubM.IndexOf( "src=" );

while( begin_nums2 >= 0 )

{

String tmpStr = sTotalSubM.Substring(

begin_nums2 + 4,1 );

if ( tmpStr == "\"" )

{

end_n12 = begin_nums2 + 5;

}

else

{

end_n12 = begin_nums2 + 4;

}

int end_nums2a = sTotalSubM.IndexOf( " ",end_n12

);

int end_nums2b = sTotalSubM.IndexOf( ">",end_n12

);

if ( end_nums2b < 0 )

{

break;

}

if ( end_nums2a > end_nums2b )

{

end_nums2 = end_nums2b;

}

else

{

if (end_nums2a<0)

{

end_nums2 = end_nums2b;

}

else

{

end_nums2 = end_nums2a;

}

tmpStr = sTotalSubM.Substring( end_nums2-1,1 );

if ( tmpStr == "\"" || tmpStr == "'" )

{

end_nums2 = end_nums2 - 1;

}

string tmpPicStr = sTotalSubM.Substring(

end_n12,end_nums2 - end_n12 );

if ( tmpPicStr.IndexOf( "http://" ) < 0 )

{

if ( tmpPicStr.IndexOf( "/" ) == 0 )

{

tmpPicStr = urlch1 + tmpPicStr;

}

else

{

int linshiIntNum = 0;

int flags = 0;

string urlChange = subUrl;

while( tmpPicStr.IndexOf( "../" ) >= 0 )

{

tmpPicStr = tmpPicStr.Substring(

tmpPicStr.IndexOf("../") + 3 );

linshiIntNum = linshiIntNum + 1;

flags = flags + 1;

}

while( ( urlChange.LastIndexOf( "/" ) >=

0 ) && ( linshiIntNum >= 0 ) )

{

urlChange = urlChange.Substring(

0,urlChange.LastIndexOf( "/" ) );

linshiIntNum = linshiIntNum - 1;

}

if ( flags == 0 )

{

tmpPicStr = urlch2 + "/" +

tmpPicStr;

}

else

{

tmpPicStr = urlChange + "/" +

tmpPicStr;

}

//tmpPicStr = tmpPicStr.ToLower();

string tmpPicStrTmp = tmpPicStr.ToLower();

//if ( tmpPicStr.IndexOf( ".jpg" ) > 0 ||

tmpPicStr.IndexOf( ".gif" ) > 0 || tmpPicStr.IndexOf( ".bmp" ) > 0 )

if ( tmpPicStrTmp.IndexOf( ".jpg" ) > 0 ||

tmpPicStrTmp.IndexOf( ".gif" ) > 0 || tmpPicStrTmp.IndexOf( ".bmp" )

> 0 )

{

rePicStr = rePicStr + "||" + tmpPicStr ;

int flagN2 = tmpPicStr.LastIndexOf( "/" );

string fileN2 = picHtml +

tmpPicStr.Substring( flagN2 );

sTotalSubM = sTotalSubM.Substring(

0,end_nums2 ) + ">******" + fileN2 + "******<" +

sTotalSubM.Substring( end_nums2 );

begin_nums2 = sTotalSubM.IndexOf( "src=",

end_nums2 + fileN2.Length + 22 );

}

else

{

begin_nums2 = sTotalSubM.IndexOf( "src=",

end_nums2 + 4 );

}

if ( rePicStr.Length > 2 )

rePicStr = rePicStr.Substring(2);

//内容处理格式化关键标记

while( sTotalSubM.IndexOf( "<P" ) >= 0 )

{

sTotalSubM = sTotalSubM.Substring(

0,sTotalSubM.IndexOf( "<P" ) ) + "|****|<" + sTotalSubM.Substring(

sTotalSubM.IndexOf( "<P" ) + 2 );

}

while( sTotalSubM.IndexOf( "<p" ) >= 0 )

{

sTotalSubM = sTotalSubM.Substring(

0,sTotalSubM.IndexOf( "<p" ) ) + "|****|<" + sTotalSubM.Substring(

sTotalSubM.IndexOf( "<p" ) + 2 );

}

while( sTotalSubM.IndexOf( "</P" ) >= 0 )

{

sTotalSubM = sTotalSubM.Substring(

0,sTotalSubM.IndexOf( "</P" ) ) + "|****|<" + sTotalSubM.Substring(

sTotalSubM.IndexOf( "</P" ) + 3 );

}

while( sTotalSubM.IndexOf( "</p" ) >= 0 )

{

sTotalSubM = sTotalSubM.Substring(

0,sTotalSubM.IndexOf( "</p" ) ) + "|****|<" + sTotalSubM.Substring(

sTotalSubM.IndexOf( "</p" ) + 3 );

}

while( sTotalSubM.IndexOf( "<br" ) >=0 )

{

sTotalSubM = sTotalSubM.Substring(

0,sTotalSubM.IndexOf( "<br" ) ) + "+****+<" + sTotalSubM.Substring(

sTotalSubM.IndexOf( "<br" ) + 3 );

}

while( sTotalSubM.IndexOf( "<BR" ) >= 0 )

{

sTotalSubM = sTotalSubM.Substring(

0,sTotalSubM.IndexOf( "<BR" ) ) + "+****+<" + sTotalSubM.Substring(

sTotalSubM.IndexOf( "<BR" ) + 3 );

}

while( sTotalSubM.IndexOf( "<Br" ) >= 0 )

{

sTotalSubM = sTotalSubM.Substring(

0,sTotalSubM.IndexOf( "<Br" ) ) + "+****+<" + sTotalSubM.Substring(

sTotalSubM.IndexOf( "<Br" ) + 3 );

}

while( sTotalSubM.IndexOf( "<bR" ) >= 0 )

{

sTotalSubM = sTotalSubM.Substring(

0,sTotalSubM.IndexOf( "<bR" ) ) + "+****+<" + sTotalSubM.Substring(

sTotalSubM.IndexOf( "<bR" ) + 3 );

}

//去除html标记

int linshiInt1 = sTotalSubM.IndexOf( "<" );

int linshiInt2 = sTotalSubM.IndexOf( ">" );

if ( linshiInt2 < linshiInt1 )

{

sTotalSubM = sTotalSubM.Substring( linshiInt2 +

1 );

}

int linshiInt11 = sTotalSubM.LastIndexOf( "<" );

int linshiInt12 = sTotalSubM.LastIndexOf( ">" );

if ( linshiInt12 < linshiInt11 )

{

sTotalSubM = sTotalSubM.Substring( 0,linshiInt12

+ 1 );

}

linshiInt1 = sTotalSubM.IndexOf( "<" );

while ( linshiInt1 >= 0 )

{

linshiInt2 = sTotalSubM.IndexOf( ">",linshiInt1

);

if ( linshiInt2 >= 0 )

{

sTotalSubM = sTotalSubM.Substring(

0,linshiInt1 ) + sTotalSubM.Substring( linshiInt2 + 1 );

}

else

{

sTotalSubM = sTotalSubM.Substring(

0,linshiInt1 );

}

linshiInt1 = sTotalSubM.IndexOf("<");

}

//还原关键标记

int linshiInt3 = 0;

int linshiInt4 = 0;

while( sTotalSubM.IndexOf( "+****+" ) >= 0 )

{

sTotalSubM = sTotalSubM.Substring(

0,sTotalSubM.IndexOf( "+****+" ) ) + "<br>\n" +

sTotalSubM.Substring( sTotalSubM.IndexOf( "+****+" ) + 9 );

}

while( sTotalSubM.IndexOf( "|****|" ) >= 0 )

{

sTotalSubM = sTotalSubM.Substring(

0,sTotalSubM.IndexOf( "|****|" ) ) + "<br>\n" +

sTotalSubM.Substring( sTotalSubM.IndexOf( "|****|" ) + 9 );

}

while( sTotalSubM.IndexOf( "******" ) >= 0 )

{

linshiInt3 = sTotalSubM.IndexOf( "******" ) + 9;

linshiInt4 = sTotalSubM.IndexOf(

"******",linshiInt3 );

if ( linshiInt4 >= 0 )

{

int tmpPos = sTotalSubM.IndexOf( "******" );

string tmpStr1 = sTotalSubM.Substring(

0,tmpPos );

string tmpStr2 = sTotalSubM.Substring(

linshiInt3,linshiInt4 - linshiInt3 );

string tmpStr3 = sTotalSubM.Substring(

linshiInt4 + 9 );

sTotalSubM = tmpStr1 + "<img src=" + tmpStr2

+ ">" + tmpStr3;

}

else

{

break;

}

//去除内容中的标题

if ( sTotalSubM.IndexOf( subTitle ) >= 0 )

{

sTotalSubM = sTotalSubM.Substring(

0,sTotalSubM.IndexOf( subTitle ) ) + sTotalSubM.Substring(

sTotalSubM.IndexOf( subTitle ) + subTitle.Length );

}

reContentStr = sTotalSubM;

//调用下载图片功能

//下载图片到指定目录

string[] img_Url = new PublicFun().split(

rePicStr,"||" );

for ( int i=0;i<img_Url.Length;i++ )

{

if ( img_Url[i] != "" )

{

new PublicFun().Get_Img(

img_Url[i],10000,root + "\\images\\" + img_Url[i].Substring(

img_Url[i].LastIndexOf("/")+1 ) );

}

return reContentStr;

}

以上方法返回要取得的信息，包括标题内容，图片地址等。

下载页面中图片：

//下载图片

public void Get_Img(string a_strUrl,int timeout,string

filepath)

{

try

{

HttpWebRequest myReq =

(HttpWebRequest)HttpWebRequest.Create(a_strUrl) ;

myReq.Timeout = timeout;

HttpWebResponse HttpWResp =

(HttpWebResponse)myReq.GetResponse();

Stream myStream = HttpWResp.GetResponseStream () ;

Bitmap map = new Bitmap( myStream );

PictureBox picB = new PictureBox();

picB.Image = (Image)map;

string path = filepath.Substring(

0,filepath.LastIndexOf( "\\" ) );

if (!Directory.Exists(path))

{

CreateDir( path );

}

picB.Image.Save(filepath);

}

catch(Exception exp)

{

string ss = exp.Message;

WriteLog( filepath.Substring(0,filepath.LastIndexOf("\\")) +

"\\error.log",a_strUrl + "--" + ss + "\r\n");

}

l 保存文件或入库

上面取得的信息可以按自己的要求保存。

****设计的时候没有使用url按层次循环抓取，这样定义抓取url效率更高，速度更快。

posted on 2007-09-19 08:14 石川阅读(248) 评论(0) 编辑收藏举报