魇 通过本文主要向大家介绍了c#多线程爬虫,c#多线程,c#多线程编程实例,c#多线程编程,c#多线程同步等相关知识,希望对您有所帮助,也希望大家支持linkedu.com www.linkedu.com
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，
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;
}
</div>
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";
}
</div>
话不多说，更多的需要大家自己去改进咯！欢迎读者来与楼主进行交流。
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