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From Tao Xiao <xiaotao.cs....@gmail.com>
Subject Re: issue about no class find in running MR job
Date Fri, 13 Dec 2013 02:17:45 GMT
how did you package and compile your jar ? did you specify the main class
for the JAR file you generated ?


2013/12/13 ch huang <justlooks@gmail.com>

> 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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