wiki:Hadoop_Lab4_hello_018
import java.io.IOException;
import java.util.Iterator;

import org.apache.hadoop.fs.Path;
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 Hello {

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

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

      output.collect(key, value);
    }
  }

  public static class Reduce extends MapReduceBase implements
      Reducer<LongWritable, Text, LongWritable, Text> {
    Text ret = new Text("");

    public void reduce(LongWritable key, Iterator<Text> values,
        OutputCollector<LongWritable, Text> output, Reporter reporter)
        throws IOException {

      while (values.hasNext()) {
        ret = values.next();
      }
      output.collect(key, ret);
    }
  }

  public static void main(String[] args) throws Exception {
    JobConf conf = new JobConf(Hello.class);
    conf.setJobName("Hello");

    conf.setMapperClass(Map.class);
    conf.setCombinerClass(Reduce.class);
    conf.setReducerClass(Reduce.class);
    conf.setMapOutputKeyClass(LongWritable.class);
    conf.setMapOutputValueClass(Text.class);
    conf.setOutputKeyClass(LongWritable.class);
    conf.setOutputValueClass(Text.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);
  }
}

Last modified 11 years ago Last modified on Mar 3, 2010, 12:14:04 PM