.Net中也有很多很多開源的爬蟲工具，abot就是其中之一。Abot是一個開源的.net爬蟲，速度快，易于使用和擴展。項目的地址是https://code.google.com/p/abot/
對于爬取的Html，使用的分析工具是CsQuery, CsQuery可以算是.net中實現的Jquery, 可以使用類似Jquery中的方法來處理html頁面。CsQuery的項目地址是https://github.com/afeiship/CsQuery
1. 通過屬性設置
先創建config對象，然后設置config中的各項屬性:
CrawlConfiguration crawlConfig = new CrawlConfiguration(); crawlConfig.CrawlTimeoutSeconds = 100; crawlConfig.MaxConcurrentThreads = 10; crawlConfig.MaxPagesToCrawl = 1000; crawlConfig.UserAgentString = "abot v1.0 http://code.google.com/p/abot"; crawlConfig.ConfigurationExtensions.Add("SomeCustomConfigValue1", "1111"); crawlConfig.ConfigurationExtensions.Add("SomeCustomConfigValue2", "2222");
2. 通過App.config配置
直接從配置文件中讀取，但是也任然可以在修改各項屬性:
CrawlConfiguration crawlConfig = AbotConfigurationSectionHandler.LoadFromxml().Convert(); crawlConfig.CrawlTimeoutSeconds = 100; crawlConfig.MaxConcurrentThreads = 10;
3. 應用配置到爬蟲對象
PoliteWebCrawler crawler = new PoliteWebCrawler();PoliteWebCrawler crawler = new PoliteWebCrawler(crawlConfig, null, null, null, null, null, null, null);
爬蟲中主要是4個事件, 頁面爬取開始、頁面爬取失敗、頁面不允許爬取事件、頁面中的鏈接不允許爬取事件。
下面是示例代碼:
crawlergeCrawlStartingAsync += crawler_PRocessPageCrawlStarting;//單個頁面爬取開始 crawler.PageCrawlCompletedAsync += crawler_ProcessPageCrawlCompleted;//單個頁面爬取結束 crawler.PageCrawlDisallowedAsync += crawler_PageCrawlDisallowed;//頁面不允許爬取事件 crawler.PageLinksCrawlDisallowedAsync += crawler_PageLinksCrawlDisallowed;//頁面鏈接不允許爬取事件void crawler_ProcessPageCrawlStarting(object sender, PageCrawlStartingArgs e){ PageToCrawl pageToCrawl = e.PageToCrawl; Console.WriteLine("About to crawl link {0} which was found on page {1}", pageToCrawl.Uri.AbsoluteUri, pageToCrawl.ParentUri.AbsoluteUri);}void crawler_ProcessPageCrawlCompleted(object sender, PageCrawlCompletedArgs e){ CrawledPage crawledPage = e.CrawledPage; if (crawledPage.WebException != null || crawledPage.HttpWebResponse.StatusCode != HttpStatusCode.OK) Console.WriteLine("Crawl of page failed {0}", crawledPage.Uri.AbsoluteUri); else Console.WriteLine("Crawl of page succeeded {0}", crawledPage.Uri.AbsoluteUri); if (string.IsNullOrEmpty(crawledPage.Content.Text)) Console.WriteLine("Page had no content {0}", crawledPage.Uri.AbsoluteUri);}void crawler_PageLinksCrawlDisallowed(object sender, PageLinksCrawlDisallowedArgs e){ CrawledPage crawledPage = e.CrawledPage; Console.WriteLine("Did not crawl the links on page {0} due to {1}", crawledPage.Uri.AbsoluteUri, e.DisallowedReason);}void crawler_PageCrawlDisallowed(object sender, PageCrawlDisallowedArgs e){ PageToCrawl pageToCrawl = e.PageToCrawl; Console.WriteLine("Did not crawl page {0} due to {1}", pageToCrawl.Uri.AbsoluteUri, e.DisallowedReason);}
Abot應該是借鑒了asp.net MVC中的ViewBag, 也為爬蟲對象設置了對象級別的CrwalBag和Page級別的ViewBag.
PoliteWebCrawler crawler = new PoliteWebCrawler();crawler.CrawlBag.MyFoo1 = new Foo();//對象級別的CrwalBagcrawler.CrawlBag.MyFoo2 = new Foo();crawler.PageCrawlStartingAsync += crawler_ProcessPageCrawlStarting;...void crawler_ProcessPageCrawlStarting(object sender, PageCrawlStartingArgs e){ //獲取CrwalBag中的對象 CrawlContext context = e.CrawlContext; context.CrawlBag.MyFoo1.Bar();//使用CrwalBag context.CrawlBag.MyFoo2.Bar(); //使用頁面級別的PageBag e.PageToCrawl.PageBag.Bar = new Bar();}
啟動爬蟲非常簡單，調用Crawl方法，指定好開始頁面，就可以了。
CrawlResult result = crawler.Crawl(new Uri("http://localhost:1111/"));if (result.ErrorOccurred) Console.WriteLine("Crawl of {0} completed with error: {1}", result.RootUri.AbsoluteUri, result.ErrorException.Message);else Console.WriteLine("Crawl of {0} completed without error.", result.RootUri.AbsoluteUri);
在PageCrawlCompletedAsync事件中, e.CrawledPage.CsQueryDocument就是一個CsQuery對象。
這里介紹一下CsQuery在分析Html上的優勢:
cqDocument.Select(".bigtitle > h1")
這里的選擇器的用法和Jquery完全相同，這里是取class為.bittitle下的h1標簽。如果你能熟練的使用Jquery，那么上手CsQuery會非常快和容易。
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