hadoop - 尝试从Hadoop URL读取数据，但无法读取错误信息

Question

ReadFromHadoopURL文件的内容如下:

package com.felix.hadoop.training;

import java.io.InputStream;
import java.net.URL;

import org.apache.hadoop.fs.FsUrlStreamHandlerFactory;
import org.apache.hadoop.io.IOUtils;

//  URLCat
public class ReadFromHadoopURL {

  static {
        URL.setURLStreamHandlerFactory(new FsUrlStreamHandlerFactory());
  }

  public static void main(String[] args) throws Exception {
    InputStream in = null;
    try {
      in = new URL(args[0]).openStream();
      IOUtils.copyBytes(in, System.out, 4096, false);
    } finally {
      IOUtils.closeStream(in);
    }
      }
    }

然后，我创建了一个jar文件ReadFromHadoopURL.jar。

然后我运行了这个命令

hadoop jar /home/training/Pradosh/ReadFromHadoopURL.jar ReadFromHadoopURL hdfs://localhost:54310/my/empfile

我收到此错误

Exception in thread "main" java.lang.ClassNotFoundException: ReadFromHadoopURL
    at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:423)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:356)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:264)
    at org.apache.hadoop.util.RunJar.main(RunJar.java:149)

您能帮我调试一下吗？

Answer 1

您可能只需要使用包名完全限定您的类名。 ReadFromHadoopURL应该是com.felix.hadoop.training.ReadFromHadoopURL。

hadoop jar /home/training/Pradosh/ReadFromHadoopURL.jar com.felix.hadoop.training.ReadFromHadoopURL hdfs://localhost:54310/my/empfile