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From ch huang <justlo...@gmail.com>
Subject issue about no class find in running MR job
Date Fri, 13 Dec 2013 02:11:05 GMT
hi,maillist:

             i rewrite WordCount.java and try to compile and run  it but it
say not find main class ,why?

[root@CHBM224 myMR]# cat WordCount.java
import java.io.IOException;
import java.util.StringTokenizer;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;
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;
import org.apache.hadoop.util.ToolRunner;
import org.apache.hadoop.util.Tool;
public class WordCount extends Configured implements Tool {
  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);
    }
  }
  private static void usage() throws IOException {
    System.err.println("teragen <num rows> <output dir>");
  }
  public int run(String[] args) throws IOException, InterruptedException,
ClassN
otFoundException {
        Job job = Job.getInstance(getConf());
        if (args.length != 2) {
              usage();
              return 2;
        }
        job.setJobName("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]));
        return job.waitForCompletion(true) ? 0 : 1;
  }
  public static void main(String[] args) throws Exception {
        int res = ToolRunner.run(new Configuration(), new WordCount(),
args);
        System.exit(res);
  }
}
[root@CHBM224 myMR]# javac -cp
'/usr/lib/hadoop/*:/usr/lib/hadoop-mapreduce/*' -d ../test WordCount.java
[root@CHBM224 myMR]#  hadoop ../test/WordCount
Error: Could not find or load main class ...test.WordCount

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