Question

我正在尝试运行puma benchmark

中给出的单词计数程序

The WordCount.java file is as follows:

/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.hadoop.examples;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
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 = new Job(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);

    List<String> other_args = new ArrayList<String>();
    for(int i=0; i < args.length; ++i) {
      try {
        if ("-r".equals(args[i])) {
          job.setNumReduceTasks(Integer.parseInt(args[++i]));
        } else {
          other_args.add(args[i]);
        }
      } catch (NumberFormatException except) {
        System.out.println("ERROR: Integer expected instead of " + args[i]);
        System.err.println("Usage: wordcount <numReduces> <in> <out>");
        System.exit(2);         
      } catch (ArrayIndexOutOfBoundsException except) {
        System.out.println("ERROR: Required parameter missing from " +
            args[i-1]);
        System.err.println("Usage: wordcount <numReduces> <in> <out>");
        System.exit(2);
      }
    }
    // Make sure there are exactly 2 parameters left.
    if (other_args.size() != 2) {
      System.out.println("ERROR: Wrong number of parameters: " +
          other_args.size() + " instead of 2.");
      System.err.println("Usage: wordcount <numReduces> <in> <out>");
      System.exit(2);
    }

    FileInputFormat.addInputPath(job, new Path(other_args.get(0)));
    FileOutputFormat.setOutputPath(job, new Path(other_args.get(1)));
    Date startIteration = new Date();
    Boolean waitforCompletion = job.waitForCompletion(true) ;
    Date endIteration = new Date();
    System.out.println("The iteration took "
        + (endIteration.getTime() - startIteration.getTime()) / 1000
        + " seconds.");
    System.exit(waitforCompletion ? 0 : 1);
  }
}

我使用了以下命令并获得了以下结果：

#javac -cp /opt/local/share/java/hadoop-1.2.1/hadoop-core-1.2.1.jar -d wordcount_classes WordCount.java

#jar -cvf wordcount.jar -C wordcount_classes/ .

我得到的输出是：

added manifest
adding: org/(in = 0) (out= 0)(stored 0%)
adding: org/apache/(in = 0) (out= 0)(stored 0%)
adding: org/apache/hadoop/(in = 0) (out= 0)(stored 0%)
adding: org/apache/hadoop/examples/(in = 0) (out= 0)(stored 0%)
adding: org/apache/hadoop/examples/WordCount$IntSumReducer.class(in = 1793) (out= 750)(deflated 58%)
adding: org/apache/hadoop/examples/WordCount$TokenizerMapper.class(in = 1790) (out= 764)(deflated 57%)
adding: org/apache/hadoop/examples/WordCount.class(in = 3131) (out= 1682)(deflated 46%)
adding: org/myorg/(in = 0) (out= 0)(stored 0%)
adding: org/myorg/WordCount$IntSumReducer.class(in = 1759) (out= 745)(deflated 57%)
adding: org/myorg/WordCount$TokenizerMapper.class(in = 1756) (out= 759)(deflated 56%)
adding: org/myorg/WordCount.class(in = 3080) (out= 1676)(deflated 45%)


#hadoop jar wordcount.jar WordCount ../input/file01.txt ../output/

我得到了以下输出：

Exception in thread "main" java.lang.NoClassDefFoundError: WordCount (wrong name: org/apache/hadoop/examples/WordCount)
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClass(ClassLoader.java:800)
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
    at java.net.URLClassLoader.defineClass(URLClassLoader.java:449)
    at java.net.URLClassLoader.access$100(URLClassLoader.java:71)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:412)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
    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)

我在本网站中应用了之前描述的所有程序，但没有任何对我有用。如果有人告诉我如何解决这个问题，我将非常感激。

Answer 1

将包语句更改为

package org.myorg;

使用完整的班级名称运行程序。

查看输出，您似乎在不同的路径（= packages）中包含WordCount类两次，但是当您运行该程序时，您没有指定任何包。

Answer 2

hadoop jar wordcount.jar org/apache/hadoop/examples/WordCount ../input/file01.txt ../output/

我认为存在问题，因为您没有使用完整的班级名称。

Answer 3

你的wordcount.jar有两个Wordount类，用你要运行的限定符来指定类。

e.g

hadoop jar wordcount.jar org.apache.hadoop.examples.WordCount ../input/file01.txt ../output/

或

hadoop jar wordcount.jar org.myorg.WordCount ../input/file01.txt ../output/

Answer 4

您的WordCount class内部有两个嵌套类，即：TokenizerMapper和IntSumReducer。

您需要确保这些类包含在您正在生成的 jar 文件中。试试这个：

jar cvf WordCount.jar WordCount.class WordCount\$TokenizerMapper.class WordCount\$IntSumReducer.class

在运行hadoop字数统计程序时遇到麻烦

4 个答案: