线程“main”java.lang.NoClassDefFoundError中的异常:org/apache/http/c

Question

我正在使用Crawler4j示例代码，但我发现我得到了一个异常。

这是我的例外：

Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/http/conn/scheme/SchemeSocketFactory
    at LocalDataCollectorController.main(LocalDataCollectorController.java:24)
Caused by: java.lang.ClassNotFoundException: org.apache.http.conn.scheme.SchemeSocketFactory 

这是我的代码：

    public static void main(String[] args) throws Exception {
            String root Folder = "D:\";
            int numberOfCrawlers = 5;
            System.out.println("numberOfCrawlers"+numberOfCrawlers);
            System.out.println(rootFolder);
          CrawlConfig config = new CrawlConfig();
            config.setCrawlStorageFolder(rootFolder);
            config.setMaxPagesToFetch(10);
            config.setPolitenessDelay(1000);
              PageFetcher pageFetcher = new PageFetcher(config);
           RobotstxtConfig robotstxtConfig = new RobotstxtConfig();
            RobotstxtServer robotstxtServer = new RobotstxtServer(robotstxtConfig, pageFetcher);
            CrawlController controller = new CrawlController(config, pageFetcher, robotstxtServer);
            controller.addSeed("http://www.ohloh.net/p/crawler4j");
            controller.start(LocalDataCollectorCrawler.class, numberOfCrawlers);
            List<Object> crawlersLocalData = controller.getCrawlersLocalData();
            long totalLinks = 0;
            long totalTextSize = 0;
            int totalProcessedPages = 0;
            for (Object localData : crawlersLocalData) {
                    CrawlStat stat = (CrawlStat) localData;
                    totalLinks += stat.getTotalLinks();
                    totalTextSize += stat.getTotalTextSize();
                    totalProcessedPages += stat.getTotalProcessedPages();
            }
           System.out.println("Aggregated Statistics:");
            System.out.println("   Processed Pages: " + totalProcessedPages);
            System.out.println("   Total Links found: " + totalLinks);
            System.out.println("   Total Text Size: " + totalTextSize);
    }
}

Answer 1

下载HttpClient并将其添加到构建路径中。

还有一个软件包，其中包含下载部分的所有 crawler4j 依赖项。您应该使用它来避免进一步的问题。

Answer 2

NoClassDefFoundError的原因始终相同：您在运行时执行期间未提供依赖项类。换句话说，当你运行你的示例时，你没有把 HttpClient 的 JAR 文件放在类路径上。这样做，问题就会消失。