无法运行jar文件，因为“无法找到或加载主类” [英] Cannot run jar file because of "Could not find or load main class"

问题描述

我有一个测试目录，其中包含3个文件夹：

   -  META-INF：
一个文件MANIFEST.MF在目录中：
 MANIFEST.MF：
 anifest-Version：1.0 
创建者：1.7.0_04 -ea（Oracle Corporation）
 Class-Path：lib / *; 。 
 Main-Class：Setup.WordCount 
  -  lib：
我需要的所有外部jar文件
  - 安装程序：
 dir中的3个文件： 
 WordCount $ IntSumReducer.clas 
 WordCount $ TokenizerMapper.class 
 WordCount.class 
  

我使用命令创建了一个jar文件
$ b

  jar cmf test.jar test / META-INF / MANIFEST.MF test / Setup test / lib 
  

但是当我尝试运行 test.jar ，报错：

 错误：无法找到或加载主类Setup.WordCount 
  

我试图调试prob一整天，仍然不知道！

WordCount.java ：

  package Setup; 
 
 import java.io.IOException; 
 import java.util.StringTokenizer; 
 
导入org.apache.hadoop.conf.Configuration; 
导入org.apache.hadoop.fs.Path; 
 import org.apache.hadoop.io.IntWritable; 
 import org.apache.hadoop.io.Text; 
 import org.apache.hadoop.mapreduce.Job; 
 import org.apache.hadoop.mapreduce.Mapper; 
 import org.apache.hadoop.mapreduce.Reducer; 
 import org.apache.hadoop.mapreduce.lib.input.FileInputFormat; 
 import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat; 
 import org.apache.hadoop.util.GenericOptionsParser; 
 
 public class WordCount {
 
 public static class TokenizerMapper 
 extends Mapper< Object，Text，Text，IntWritable> {
 
 private final static IntWritable one = new IntWritable（1）; 
私人文字=新文字（）; 
 
 public void map（Object key，Text value，Context context 
）throws IOException，InterruptedException {
 StringTokenizer itr = new StringTokenizer（value.toString（））; 
 while（itr.hasMoreTokens（））{
 word.set（itr.nextToken（））; 
 context.write（word，one）; 
 
 
 
 
 public static class IntSumReducer 
 extends Reducer< Text，IntWritable，Text，IntWritable> {
 private IntWritable result = new IntWritable（）; 
 $ b public void reduce（Text key，Iterable< IntWritable> values，
 Context context 
）throws IOException，InterruptedException {
 int sum = 0; （IntWritable val：values）
 {
 sum + = val.get（）; 
} 
 result.set（sum）; 
 context.write（key，result）; 
 
 
 
 public static void main（String [] args）throws Exception {
 Configuration conf = new Configuration（）; 
 String [] otherArgs = new GenericOptionsParser（conf，args）.getRemainingArgs（）; 
 if（otherArgs.length！= 2）{
 System.err.println（Usage：wordcount< in>< out>）; 
 System.exit（2）; 
} 
工作工作=新工作（conf，字数）; 
 job.setJarByClass（WordCount.class）; 
 job.setMapperClass（TokenizerMapper.class）; 
 job.setCombinerClass（IntSumReducer.class）; 
 job.setReducerClass（IntSumReducer.class）; 
 job.setOutputKeyClass（Text.class）; 
 job.setOutputValueClass（IntWritable.class）; 
 FileInputFormat.addInputPath（job，new Path（otherArgs [0]））; 
 FileOutputFormat.setOutputPath（job，new Path（otherArgs [1]））; 
 System.exit（job.waitForCompletion（true）？0：1）; 
 
 
 $ / code $ / pre 
 
 
代码与<$ c $完全相同c> hadoop / example / WordCount ，我试图在我的本地开发环境中实现hadoop示例。   

>你的jar语句稍微偏离。试试这个：

  jar -cfm test.jar测试/ META-INF / MANIFEST.MF -C测试设置-C测试lib 
  

您的命令将test / Setup / WordCount.class放在jar文件中，这就是为什么Java找不到安装程序/WordCount.class

您还遗漏了您发布的代码中的包装声明：

 软件包安装程序; 
  

I have a test dir, which contains 3 folders:

--META-INF:
  one file MANIFEST.MF in the dir:
  MANIFEST.MF:
      anifest-Version: 1.0
      Created-By: 1.7.0_04-ea (Oracle Corporation)
      Class-Path: lib/*; .
      Main-Class: Setup.WordCount
-- lib:
   all the external jars I need for the project
-- Setup:
   3 files in the dir:
   WordCount$IntSumReducer.clas
   WordCount$TokenizerMapper.class
   WordCount.class

I create a jar file using the command

jar cmf test.jar test/META-INF/MANIFEST.MF test/Setup test/lib

but when I try to run the test.jar, an error reported:

Error: Could not find or load main class Setup.WordCount

I’ve tried to debug the prob for the whole day, still no idea!

WordCount.java:

package Setup;

import java.io.IOException;
import java.util.StringTokenizer;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.util.GenericOptionsParser;

public class WordCount {

  public static class TokenizerMapper
       extends Mapper<Object, Text, Text, IntWritable>{

    private final static IntWritable one = new IntWritable(1);
    private Text word = new Text();

    public void map(Object key, Text value, Context context
                    ) throws IOException, InterruptedException {
      StringTokenizer itr = new StringTokenizer(value.toString());
      while (itr.hasMoreTokens()) {
        word.set(itr.nextToken());
        context.write(word, one);
      }
    }
  }

  public static class IntSumReducer
       extends Reducer<Text,IntWritable,Text,IntWritable> {
    private IntWritable result = new IntWritable();

    public void reduce(Text key, Iterable<IntWritable> values,
                       Context context
                       ) throws IOException, InterruptedException {
      int sum = 0;
      for (IntWritable val : values) {
        sum += val.get();
      }
      result.set(sum);
      context.write(key, result);
    }
  }

  public static void main(String[] args) throws Exception {
    Configuration conf = new Configuration();
    String[] otherArgs = new GenericOptionsParser(conf, args).getRemainingArgs();
    if (otherArgs.length != 2) {
      System.err.println("Usage: wordcount <in> <out>");
      System.exit(2);
    }
    Job job = new Job(conf, "word count");
    job.setJarByClass(WordCount.class);
    job.setMapperClass(TokenizerMapper.class);
    job.setCombinerClass(IntSumReducer.class);
    job.setReducerClass(IntSumReducer.class);
    job.setOutputKeyClass(Text.class);
    job.setOutputValueClass(IntWritable.class);
    FileInputFormat.addInputPath(job, new Path(otherArgs[0]));
    FileOutputFormat.setOutputPath(job, new Path(otherArgs[1]));
    System.exit(job.waitForCompletion(true) ? 0 : 1);
  }
}

The code is exactly the same as hadoop/example/WordCount, I’m trying to implementing hadoop example on my local dev environment.

解决方案

Your jar statement is slightly off. Try this:

jar -cfm test.jar test/META-INF/MANIFEST.MF -C test Setup -C test lib

Your command puts test/Setup/WordCount.class in the jar, which is why Java cannot find Setup/WordCount.class

You are also missing the package statement in the code you posted:

package Setup;

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