java - Crawler4j，某些URL可以毫无问题地进行爬网，而其他URL则完全不可以进行爬网

我一直在玩Crawler4j，并成功地使它爬行了一些页面，但是没有成功地爬行了其他页面。例如，我已使用以下代码成功抓取了Reddi:

public class Controller {
    public static void main(String[] args) throws Exception {
        String crawlStorageFolder = "//home/user/Documents/Misc/Crawler/test";
        int numberOfCrawlers = 1;

        CrawlConfig config = new CrawlConfig();
       config.setCrawlStorageFolder(crawlStorageFolder);

        /*
         * Instantiate the controller for this crawl.
         */
        PageFetcher pageFetcher = new PageFetcher(config);
        RobotstxtConfig robotstxtConfig = new RobotstxtConfig();
        RobotstxtServer robotstxtServer = new RobotstxtServer(robotstxtConfig, pageFetcher);
        CrawlController controller = new CrawlController(config, pageFetcher, robotstxtServer);

        /*
         * For each crawl, you need to add some seed urls. These are the first
         * URLs that are fetched and then the crawler starts following links
         * which are found in these pages
         */
        controller.addSeed("https://www.reddit.com/r/movies");
        controller.addSeed("https://www.reddit.com/r/politics");


        /*
         * Start the crawl. This is a blocking operation, meaning that your code
         * will reach the line after this only when crawling is finished.
         */
        controller.start(MyCrawler.class, numberOfCrawlers);
    }


}

与:

@Override
 public boolean shouldVisit(Page referringPage, WebURL url) {
     String href = url.getURL().toLowerCase();
     return !FILTERS.matcher(href).matches()
            && href.startsWith("https://www.reddit.com/");
 }

在MyCrawler.java中。但是，当我尝试爬网http://www.ratemyprofessors.com/时，该程序只是挂起而没有输出，并且不爬网任何内容。我在myController.java中使用上面的以下代码:

controller.addSeed("http://www.ratemyprofessors.com/campusRatings.jsp?sid=1222");
controller.addSeed("http://www.ratemyprofessors.com/ShowRatings.jsp?tid=136044");

在MyCrawler.java中:

 @Override
 public boolean shouldVisit(Page referringPage, WebURL url) {
     String href = url.getURL().toLowerCase();
     return !FILTERS.matcher(href).matches()
            && href.startsWith("http://www.ratemyprofessors.com/");
 }

所以我想知道:

是否有些服务器能够立即识别爬网程序并且不允许它们收集数据？

我注意到RateMyProfessor页面是.jsp格式；这可能与它有关吗？

有什么方法可以更好地调试它？控制台不输出任何内容。

最佳答案

crawler4j尊重爬虫的礼貌，例如 robots.txt 。在您的情况下，此文件为以下one。

检查此文件可以发现，它不允许爬取给定的种子点:

 Disallow: /ShowRatings.jsp
 Disallow: /campusRatings.jsp

crawler4j日志输出支持此理论:

2015-12-15 19:47:18,791 WARN  [main] CrawlController (430): Robots.txt does not allow this seed: http://www.ratemyprofessors.com/campusRatings.jsp?sid=1222
2015-12-15 19:47:18,793 WARN  [main] CrawlController (430): Robots.txt does not allow this seed: http://www.ratemyprofessors.com/ShowRatings.jsp?tid=136044