HADOOP :: java.lang.ClassNotFoundException：WordCount [英] HADOOP :: java.lang.ClassNotFoundException: WordCount

问题描述

我使用eclipse导出map-reduce程序的jar文件。当我使用命令运行jar时

  hadoop jar hadoop-prog.jar WordCount / home / temp / input / home / temp /输出
  

它总是显示错误：

< pre在java.net.URLClassLoader中的
$ 1.run（URLClassLoader.java:202）
在java中
在java中的异常.security.AccessController.doPrivileged（本地方法）$ b $ java.net.URLClassLoader.findClass（URLClassLoader.java:190）
at java.lang.ClassLoader.loadClass（ClassLoader.java:306）$ b $ java.util.ClassLoader.loadClass（ClassLoader.java:247）$ b $ at java.lang.Class.forName0（Native Method）$ b $ java.util.Class.forName（Class.java： 247）
at org.apache.hadoop.util.RunJar.main（RunJar.java:149）

顺便说一句，我从互联网上得到了一个wordcount的示例jar文件，它运行得非常好。

我找不出问题在哪里。 p>

$ p> hadoop jar hadoop * examples * .jar wordcount / home / temp / input / home / temp / output


更多关于如何运行wordcount的信息此链接。

一般来说，如果您正在开发自己的Map / Reduce作业，那么您应该包括你的驱动类的完整包名，所以类似这样的东西可能会起作用：

  hadoop jar wordcount.jar com.something .WordCount / home / temp / input / home / temp / output 
  

I am using eclipse to export the jar file of a map-reduce program. When i am run the jar using command

 hadoop jar hadoop-prog.jar WordCount /home/temp/input /home/temp/output

it always shows the error :

   Exception in thread "main" java.lang.ClassNotFoundException: WordCount
    at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:247)
    at org.apache.hadoop.util.RunJar.main(RunJar.java:149)

Btw, I get a sample example jar file of wordcount from internet and it ran very well.

I could not figure out where is the problem.

解决方案

If you're trying to run the wordcount provided in the examples, you should run:

hadoop jar hadoop*examples*.jar wordcount /home/temp/input /home/temp/output

More info on how to run wordcount on this link.

In general, if you're developing your own Map/Reduce jobs, you should include the full package name of your driver class, so something like this might work:

hadoop jar wordcount.jar com.something.WordCount /home/temp/input /home/temp/output

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