source: sample/hadoop-0.17/tw/org/nchc/demo/DemoWordCountTuple2.java @ 61

/**
 * Program: HBaseRecordPro.java
 * Editor: Waue Chen 
 * From :  NCHC. Taiwn
 * Last Update Date: 07/02/2008
 * Upgrade to 0.17
 */
/*
 * Cloud9: A MapReduce Library for Hadoop
 */

package tw.org.nchc.demo;

import java.io.IOException;
import java.util.Iterator;

import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
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.SequenceFileInputFormat;
import org.apache.hadoop.mapred.SequenceFileOutputFormat;

import tw.org.nchc.code.Convert;
import tw.org.nchc.tuple.ListWritable;
import tw.org.nchc.tuple.Schema;
import tw.org.nchc.tuple.Tuple;

/**
 * <p>
 * Demo that illustrates the use of the tuple library ({@link Tuple} and
 * {@link ListWritable} class). Input comes from Bible+Shakespeare sample
 * collection, encoded with {@link DemoPackRecords2}. Otherwise, this demo is
 * exactly the same as {@link DemoWordCountTuple}.
 * </p>
 */
public class DemoWordCountTuple2 {

  // create the schema for the tuple that will serve as the key
  private static final Schema KEY_SCHEMA = new Schema();

  // define the schema statically
  static {
    KEY_SCHEMA.addField("Token", String.class, "");
    KEY_SCHEMA.addField("EvenOrOdd", Integer.class, new Integer(1));
  }

  // mapper that emits tuple as the key, and value '1' for each occurrence
  private static class MapClass extends MapReduceBase implements
      Mapper<LongWritable, Tuple, Tuple, IntWritable> {

    // define value '1' statically so we can reuse the object, i.e., avoid
    // unnecessary object creation
    private final static IntWritable one = new IntWritable(1);

    // once again, reuse tuples if possible
    private Tuple tupleOut = KEY_SCHEMA.instantiate();

    public void map(LongWritable key, Tuple tupleIn,
        OutputCollector<Tuple, IntWritable> output, Reporter reporter)
        throws IOException {

      @SuppressWarnings("unchecked")
      ListWritable<Text> list = (ListWritable<Text>) tupleIn.get(1);

      for (int i = 0; i < list.size(); i++) {
        Text t = (Text) list.get(i);

        String token = t.toString();

        // put new values into the tuple
        tupleOut.set("Token", token);
        tupleOut.set("EvenOrOdd", ((Integer) tupleIn.get(0)) % 2);

        // emit key-value pair
        output.collect(tupleOut, one);
      }
    }
  }

  // reducer counts up tuple occurrences
  private static class ReduceClass extends MapReduceBase implements
      Reducer<Tuple, IntWritable, Tuple, IntWritable> {
    private final static IntWritable SumValue = new IntWritable();

    public synchronized void reduce(Tuple tupleKey,
        Iterator<IntWritable> values,
        OutputCollector<Tuple, IntWritable> output, Reporter reporter)
        throws IOException {
      // sum values
      int sum = 0;
      while (values.hasNext()) {
        sum += values.next().get();
      }

      // keep original tuple key, emit sum of counts as value
      SumValue.set(sum);
      output.collect(tupleKey, SumValue);
    }
  }

  // dummy constructor
  private DemoWordCountTuple2() {
  }

  /**
   * Runs the demo.
   */
  public static void main(String[] args) throws IOException {
    String inPath = "/shared/sample-input/bible+shakes.nopunc.packed2";
    String outputPath = "word-counts2-tuple";
    int numMapTasks = 20;
    int numReduceTasks = 20;

    JobConf conf = new JobConf(DemoWordCountTuple2.class);
    conf.setJobName("wordcount");

    conf.setNumMapTasks(numMapTasks);
    conf.setNumReduceTasks(numReduceTasks);
    
    // 0.16
//    conf.setInputPath(new Path(inPath));
    Convert.setInputPath(conf,new Path(inPath));
    conf.setInputFormat(SequenceFileInputFormat.class);
    // 0.16
//    conf.setOutputPath(new Path(outputPath));
    Convert.setInputPath(conf, new Path(outputPath));
    
    conf.setOutputKeyClass(Tuple.class);
    conf.setOutputValueClass(IntWritable.class);
    conf.setOutputFormat(SequenceFileOutputFormat.class);

    conf.setMapperClass(MapClass.class);
    conf.setCombinerClass(ReduceClass.class);
    conf.setReducerClass(ReduceClass.class);

    JobClient.runJob(conf);
  }
}