Question

我一直在玩Crawler4j并成功抓取了一些页面，但没有成功抓取其他页面。例如，我已经使用以下代码成功抓取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);
    }


}

并且：

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

MyCrawler.java中的

。但是，当我尝试抓取http://www.ratemyprofessors.com/时，程序只挂起而没有输出，也不会抓取任何内容。我在myController.java中使用了上面的代码：

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：

某些服务器是否能够立即识别抓取工具并且不允许他们收集数据？
我注意到RateMyProfessor页面是.jsp格式;这可能与它有什么关系吗？
我有什么办法可以更好地调试这个吗？控制台不输出任何内容。

Answer 1

crawler4j尊重履带式政治，例如robots.txt。在您的情况下，此文件是以下one。

检查此文件显示，不允许抓取您给定的种子点：

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

crawler4j日志输出支持该理论：

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

Answer 2

我也有类似的问题，我得到的错误信息是：

2017-01-18 14：18：21,136 WARN [Crawler 1] e.u.i.c.c.WebCrawler [：412]获取http://people.com/时未处理的异常：people.com：80未能响应
2017-01-18 14：18：21,140 INFO [Crawler 1] e.u.i.c.c.WebCrawler [：357] Stacktrace： org.apache.http.NoHttpResponseException：people.com：80未能回复

但我确信people.com会对浏览器做出回应。

Crawler4j，一些网址被抓取没有问题，而其他网址根本没有被抓取

2 个答案: