Hadoop Java错误：线程中的异常“main” java.lang.NoClassDefFoundError：WordCount（错误名称：org / myorg / WordCount） [英] Hadoop Java Error : Exception in thread "main" java.lang.NoClassDefFoundError: WordCount (wrong name: org/myorg/WordCount)

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问题描述

我是hadoop的新手。我跟着maichel-noll教程在单个节点中设置hadoop。我尝试运行WordCount程序。这是我使用的代码： 

  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; 
 
 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（）; 
 Job job = Job.getInstance（conf，WordCount）; 
 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（args [0]））; 
 FileOutputFormat.setOutputPath（job，new Path（args [1]））; 
 System.exit（job.waitForCompletion（true）？0：1）; 
} 
}

这是我尝试运行时得到的结果。 

  hduser @ aswin -HP-Pavilion-15-Notebook-PC：/ usr / local / hadoop $ bin / hadoop jar wc .jar WordCount / home / hduser / gutenberg /home/hduser/gutenberg-output/sample.txt 
线程main中的异常java.lang.NoClassDefFoundError：WordCount（错误名称：org / myorg / WordCount）
 at java.lang.ClassLoader.defineClass1（Native Method）$ b $ java.util.ClassLoader.defineClass（ClassLoader.java:788）
 at java.security.SecureClassLoader.defineClass（SecureClassLoader.java：在java.net.URLClassLoader.defineClass（URLClassLoader.java:447）处
在java.net.URLClassLoader.access处
（URLClassLoader.java:71）在java.net处
。 URLClassLoader $ 1.run（URLClassLoader.java:361）在java.net.URLClassLoader中
 $ 1.run（URLClassLoader.java:355）$ java.util.AccessController.doPrivileged中的$ b $（本地方法）
在java.net.URLClassLoader.findClass（URLClassL $ java.util.ClassLoader.loadClass（ClassLoader.java:424）
 at sun.misc.Launcher $ AppClassLoader.loadClass（Launcher.java:308）
在java.lang.ClassLoader.loadClass（ClassLoader.java:411）$ b $在java.lang.ClassLoader.loadClass（ClassLoader.java:357）
在java.lang.Class.forName0（本地方法） 
 at java.lang.Class.forName（Class.java:270）
 at org.apache.hadoop.util.RunJar.main（RunJar.java:205）

任何人都可以请帮助我。
我的课程路径：

  hduser @ aswin -HP-Pavilion-15-Notebook-PC：/ usr / local / hadoop $ hadoop classpath 
 / usr / local / hadoop / etc / hadoop：/ usr / local / hadoop / share / hadoop / common / lib / *：/ usr / local / hadoop / share / hadoop / common / *：在/ usr /本地/ Hadoop的/股/的Hadoop / HDFS：在/ usr /本地/ Hadoop的/股/的Hadoop / HDFS / lib目录/ *：在/ usr /本地/ Hadoop的/股/的Hadoop / HDFS / *：在/ usr /本地/ Hadoop的/股/的Hadoop /纱/ lib目录/ *：在/ usr /本地/ Hadoop的/股/的Hadoop /纱/ *：在/ usr /本地/ Hadoop的/股/的Hadoop / MapReduce的/ lib目录/ *：在/ usr /本地/hadoop/share/hadoop/mapreduce/*:/usr/lib/jvm/java-7-openjdk-i386/lib/tools.jar:/usr/local/hadoop/contrib/capacity-scheduler/*.jar


解决方案

试试这个， 

  import java.io.IOException; 
 import java.util.Iterator; 
 import java.util.StringTokenizer; 
 
导入org.apache.hadoop.fs.Path; 
 import org.apache.hadoop.io.IntWritable; 
 import org.apache.hadoop.io.LongWritable; 
 import org.apache.hadoop.io.Text; 
 import org.apache.hadoop.mapred.FileInputFormat; 
 import org.apache.hadoop.mapred.FileOutputFormat; 
 import org.apache.hadoop.mapred.JobClient; 
 import org.apache.hadoop.mapred.JobConf; 
 import org.apache.hadoop.mapred.MapReduceBase; 
 import org.apache.hadoop.mapred.Mapper; 
 import org.apache.hadoop.mapred.OutputCollector; 
 import org.apache.hadoop.mapred.Reducer; 
 import org.apache.hadoop.mapred.Reporter; 
 import org.apache.hadoop.mapred.TextInputFormat; 
 import org.apache.hadoop.mapred.TextOutputFormat; 
 
 public class WordCount {
 
 public static class Map扩展MapReduceBase实现
 Mapper< LongWritable，Text，Text，IntWritable> {
 
 @Override 
 public void map（LongWritable key，Text value，OutputCollector< Text，IntWritable> output，Reporter reporter）
抛出IOException {
 
 String line = value.toString（）; 
 StringTokenizer tokenizer = new StringTokenizer（line）; 
 
 while（tokenizer.hasMoreTokens（））{
 value.set（tokenizer.nextToken（））; 
 output.collect（value，new IntWritable（1））; 
 
 
 
 
 $ b public static class Reduce extends MapReduceBase implements 
 Reducer< Text，IntWritable，Text，IntWritable> {b 
 $ b @Override 
 public void reduce（Text key，Iterator< IntWritable> values，
 OutputCollector< Text，IntWritable>输出，Reporter记者）
抛出IOException { 
 int sum = 0; 
 while（values.hasNext（））{
 sum + = values.next（）。get（）; 
} 
 
 output.collect（key，new IntWritable（sum））; 
 
 
 
 public static void main（String [] args）throws Exception {
 
 JobConf conf = new JobConf（WordCount.class）; 
 conf.setJobName（wordcount）; 
 
 conf.setOutputKeyClass（Text.class）; 
 conf.setOutputValueClass（IntWritable.class）; 
 
 conf.setMapperClass（Map.class）; 
 conf.setReducerClass（Reduce.class）; 
 
 conf.setInputFormat（TextInputFormat.class）; 
 conf.setOutputFormat（TextOutputFormat.class）; 
 
 FileInputFormat.setInputPaths（conf，new Path（args [0]））; 
 FileOutputFormat.setOutputPath（conf，new Path（args [1]））; 
 
 JobClient.runJob（conf）; 
 
 
 $ b

然后运行命令

  bin / hadoop jar WordCount.jar WordCount / hdfs_Input_filename / output_filename

如果你的代码是特定的包，那么你不得不提及包名称和类名称

  bin / hadoop jar WordCount.jar PakageName.WordCount / hdfs_Input_filename / output_filename


I am new to hadoop. I followed the maichel-noll tutorial to set up hadoop in single node.I tried running WordCount program. This is the code I used:

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;

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();
    Job job = Job.getInstance(conf, "WordCount");
    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(args[0]));
    FileOutputFormat.setOutputPath(job, new Path(args[1]));
    System.exit(job.waitForCompletion(true) ? 0 : 1);
  }
}

This is what I get when I try running it.

hduser@aswin-HP-Pavilion-15-Notebook-PC:/usr/local/hadoop$ bin/hadoop jar wc.jar WordCount /home/hduser/gutenberg /home/hduser/gutenberg-output/sample.txt
Exception in thread "main" java.lang.NoClassDefFoundError: WordCount (wrong name: org/myorg/WordCount)
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClass(ClassLoader.java:788)
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
    at java.net.URLClassLoader.defineClass(URLClassLoader.java:447)
    at java.net.URLClassLoader.access$100(URLClassLoader.java:71)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:411)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:270)
    at org.apache.hadoop.util.RunJar.main(RunJar.java:205)

Can anyone please help me. My class path :

hduser@aswin-HP-Pavilion-15-Notebook-PC:/usr/local/hadoop$ hadoop classpath
/usr/local/hadoop/etc/hadoop:/usr/local/hadoop/share/hadoop/common/lib/*:/usr/local/hadoop/share/hadoop/common/*:/usr/local/hadoop/share/hadoop/hdfs:/usr/local/hadoop/share/hadoop/hdfs/lib/*:/usr/local/hadoop/share/hadoop/hdfs/*:/usr/local/hadoop/share/hadoop/yarn/lib/*:/usr/local/hadoop/share/hadoop/yarn/*:/usr/local/hadoop/share/hadoop/mapreduce/lib/*:/usr/local/hadoop/share/hadoop/mapreduce/*:/usr/lib/jvm/java-7-openjdk-i386/lib/tools.jar:/usr/local/hadoop/contrib/capacity-scheduler/*.jar

解决方案

try this,

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

import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapred.FileInputFormat;
import org.apache.hadoop.mapred.FileOutputFormat;
import org.apache.hadoop.mapred.JobClient;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.MapReduceBase;
import org.apache.hadoop.mapred.Mapper;
import org.apache.hadoop.mapred.OutputCollector;
import org.apache.hadoop.mapred.Reducer;
import org.apache.hadoop.mapred.Reporter;
import org.apache.hadoop.mapred.TextInputFormat;
import org.apache.hadoop.mapred.TextOutputFormat;

public class WordCount {

    public static class Map extends MapReduceBase implements
            Mapper<LongWritable, Text, Text, IntWritable> {

        @Override
        public void map(LongWritable key, Text value, OutputCollector<Text, IntWritable> output, Reporter reporter)
                throws IOException {

            String line = value.toString();
            StringTokenizer tokenizer = new StringTokenizer(line);

            while (tokenizer.hasMoreTokens()) {
                value.set(tokenizer.nextToken());
                output.collect(value, new IntWritable(1));
            }

        }
    }

    public static class Reduce extends MapReduceBase implements
            Reducer<Text, IntWritable, Text, IntWritable> {

        @Override
        public void reduce(Text key, Iterator<IntWritable> values,
                OutputCollector<Text, IntWritable> output, Reporter reporter)
                throws IOException {
            int sum = 0;
            while (values.hasNext()) {
                sum += values.next().get();
            }

            output.collect(key, new IntWritable(sum));
        }
    }

    public static void main(String[] args) throws Exception {

        JobConf conf = new JobConf(WordCount.class);
        conf.setJobName("wordcount");

        conf.setOutputKeyClass(Text.class);
        conf.setOutputValueClass(IntWritable.class);

        conf.setMapperClass(Map.class);
        conf.setReducerClass(Reduce.class);

        conf.setInputFormat(TextInputFormat.class);
        conf.setOutputFormat(TextOutputFormat.class);

        FileInputFormat.setInputPaths(conf, new Path(args[0]));
        FileOutputFormat.setOutputPath(conf, new Path(args[1]));

        JobClient.runJob(conf);

    }
}

then run command

bin/hadoop jar WordCount.jar WordCount /hdfs_Input_filename /output_filename

if your code is in particular package then you have to mention package name with class name

bin/hadoop jar WordCount.jar PakageName.WordCount /hdfs_Input_filename /output_filename

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