Question

我目前想要创建Hadoop的单个实例节点。所以我关注这个tutorial。我在终端中运行了以下命令：

hduser@ubuntu:/usr/local/hadoop$ bin/hadoop jar WordCount.jar geekyomega.WordCount /user/hduser/gutenberg /user/hduser/gutenberg-output

在我遇到这个错误之前，事情进展顺利：

Exception in thread "main" java.lang.ClassNotFoundException: WordCount
    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:424)
    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:153)

我试图使用以下代码运行此示例，我从here获取。这是我的代码版本：

package geekyomega;

import java.io.IOException;
import java.util.*;

import org.apache.hadoop.fs.Path;
import org.apache.hadoop.conf.*;
import org.apache.hadoop.io.*;
import org.apache.hadoop.mapreduce.*;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.input.TextInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;

public class WordCount {

 public static class Map extends Mapper<LongWritable, Text, Text, IntWritable> {
    private final static IntWritable one = new IntWritable(1);
    private Text word = new Text();

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

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

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

 public static void main(String[] args) throws Exception {
    Configuration conf = new Configuration();

    Job job = new Job(conf, "WordCount");

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

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

    job.setInputFormatClass(TextInputFormat.class);
    job.setOutputFormatClass(TextOutputFormat.class);

    FileInputFormat.addInputPath(job, new Path(args[0]));
    FileOutputFormat.setOutputPath(job, new Path(args[1]));

    job.waitForCompletion(true);
 }

}

我认为我的问题是工作实例化。所以我做了如下，我改变了：

Job job = new Job(conf, "wordcount");

以下大写版本：

Job job = new Job(conf, "WordCount");

但这没有帮助。有人知道什么可以帮助我吗？

谢谢，令人讨厌

PS - 我不想运行wordcount的教程版本。我所做的是在eclipse中创建了项目，将hadoop jar添加到它，并将其导出为jar文件。

Answer 1

你的班级名称是geekyomega.WordCount

您没有附加包名称。在命令行中，在jar文件名之后，给出作业类的完全限定名称。

Answer 2

除了添加包之外，还在程序的作业配置部分添加以下行：

<强> job.setJarByClass（WordCount.class）;

线程“main”中的异常java.lang.ClassNotFoundException：WordCount

2 个答案: