hadoop安装--18-- 验证 WordCount 例子

wordcount 代码， 这是从网上找的，源地址忘记了，》《

import java.io.IOException;

import java.util.ArrayList;

import java.util.Iterator;

import java.util.List;

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.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.util.Tool;

import org.apache.hadoop.util.ToolRunner;

/**

 * This is an example Hadoop Map/Reduce application.

 * It reads the text input files, breaks each line into words

 * and counts them. The output is a locally sorted list of words and the

 * count of how often they occurred.

 *

 * To run: bin/hadoop jar build/hadoop-examples.jar wordcount

 *            [-m <i>maps</i>] [-r <i>reduces</i>] <i>in-dir</i> <i>out-dir</i>

 */

public class WordCount extends Configured implements Tool {

 

  /**

   * Counts the words in each line.

   * For each line of input, break the line into words and emit them as

   * (<b>word</b>, <b>1</b>).

   */

  public static class MapClass extends MapReduceBase

    implements 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,

                    OutputCollector<Text, IntWritable> output,

                    Reporter reporter) throws IOException {

      String line = value.toString();

      StringTokenizer itr = new StringTokenizer(line);

      while (itr.hasMoreTokens()) {

        word.set(itr.nextToken());

        output.collect(word, one);

      }

    }

  }

 

  /**

   * A reducer class that just emits the sum of the input values.

   */

  public static class Reduce extends MapReduceBase

    implements Reducer<Text, IntWritable, Text, IntWritable> {

   

    public void reduce(Text key, Iterator<IntWritable> values,

                       OutputCollector<Text, IntWritable> output,

                       Reporter reporter) throws IOException {

      int sum = 0;

      while (values.hasNext()) {

        sum += values.next().get();

      }

      output.collect(key, new IntWritable(sum));

    }

  }

 

  static int printUsage() {

    System.out.println("wordcount [-m <maps>] [-r <reduces>] <input> <output>");

    ToolRunner.printGenericCommandUsage(System.out);

    return -1;

  }

 

  /**

   * The main driver for word count map/reduce program.

   * Invoke this method to submit the map/reduce job.

   * @throws IOException When there is communication problems with the

   *                     job tracker.

   */

  public int run(String[] args) throws Exception {

    JobConf conf = new JobConf(getConf(), WordCount.class);

    conf.setJobName("wordcount");

   

    FileInputFormat.setInputPaths(conf, new Path("hdfs://master:9000/dft_input"));

    // the keys are words (strings)

    conf.setOutputKeyClass(Text.class);

    // the values are counts (ints)

    conf.setOutputValueClass(IntWritable.class);

   

    conf.setMapperClass(MapClass.class);       

    conf.setCombinerClass(Reduce.class);

    conf.setReducerClass(Reduce.class);

   

    List<String> other_args = new ArrayList<String>();

    for(int i=0; i < args.length; ++i) {

      try {

        if ("-m".equals(args[i])) {

          conf.setNumMapTasks(Integer.parseInt(args[++i]));

        } else if ("-r".equals(args[i])) {

          conf.setNumReduceTasks(Integer.parseInt(args[++i]));

        } else {

          other_args.add(args[i]);

        }

      } catch (NumberFormatException except) {

        System.out.println("ERROR: Integer expected instead of " + args[i]);

        return printUsage();

      } catch (ArrayIndexOutOfBoundsException except) {

        System.out.println("ERROR: Required parameter missing from " +

                           args[i-1]);

        return printUsage();

      }

    }

    // Make sure there are exactly 2 parameters left.

    if (other_args.size() != 2) {

      System.out.println("ERROR: Wrong number of parameters: " +

                         other_args.size() + " instead of 2.");

      return printUsage();

    }

  //  FileInputFormat.setInputPaths(conf, other_args.get(0));

    FileOutputFormat.setOutputPath(conf, new Path(other_args.get(1)));

       

    JobClient.runJob(conf);

    return 0;

  }

 

 

  public static void main(String[] args) throws Exception {

    int res = ToolRunner.run(new Configuration(), new WordCount(), args);

    System.exit(res);

  }

}