小编Rag*_*ddy的帖子

我正在使用Crawler4j示例代码,但我发现我有一个例外.

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; …

我有以下代码

if (rs != null)
{
  out.println("result set has got something");
  while (rs.next())
  { 
    //I am processing result set now
  }
}
else
{
  out.println("result set is empty");
}

尽管rs为null,但它正在打印"结果集已经有了东西".为什么会这样发生？如何检查空结果集？