gws.WordCount.java Source code

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Here is the source code for gws.WordCount.java

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package gws;

/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

// Modified by Shimin Chen to demonstrate functionality for Homework 2
// April-May 2015

import java.io.IOException;
import java.util.StringTokenizer;

import org.apache.hadoop.conf.Configuration;
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;

public class WordCount {

    // This is the Mapper class
    // reference:
    // http://hadoop.apache.org/docs/r2.6.0/api/org/apache/hadoop/mapreduce/Mapper.html
    //
    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 IntSumCombiner 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);
        }
    }

    // This is the Reducer class
    // reference
    // http://hadoop.apache.org/docs/r2.6.0/api/org/apache/hadoop/mapreduce/Reducer.html
    //
    // We want to control the output format to look at the following:
    //
    // count of word = count
    //
    public static class IntSumReducer extends Reducer<Text, IntWritable, Text, Text> {

        private Text result_key = new Text();
        private Text result_value = new Text();
        private byte[] prefix;
        private byte[] suffix;

        protected void setup(Context context) {
            try {
                prefix = Text.encode("count of ").array();
                suffix = Text.encode(" =").array();
            } catch (Exception e) {
                prefix = suffix = new byte[0];
            }
        }

        public void reduce(Text key, Iterable<IntWritable> values, Context context)
                throws IOException, InterruptedException {
            int sum = 0;
            for (IntWritable val : values) {
                sum += val.get();
            }

            // generate result key
            result_key.set(prefix);
            result_key.append(key.getBytes(), 0, key.getLength());
            result_key.append(suffix, 0, suffix.length);

            // generate result value
            result_value.set(Integer.toString(sum));

            context.write(result_key, result_value);
        }
    }

    public static void main(String[] args) throws Exception {
        Configuration conf = new Configuration();
        conf.addResource(new Path("/home/ucas/bigdata/hadoop-2.6.2/etc/hadoop/core-site.xml"));
        conf.addResource(new Path("/home/ucas/bigdata/hadoop-2.6.2/etc/hadoop/hdfs-site.xml"));
        String[] otherArgs = new GenericOptionsParser(conf, args).getRemainingArgs();
        if (otherArgs.length < 2) {
            System.err.println("Usage: wordcount <in> [<in>...] <out>");
            System.exit(2);
        }

        Job job = Job.getInstance(conf, "word count");

        job.setJarByClass(WordCount.class);

        job.setMapperClass(TokenizerMapper.class);
        job.setCombinerClass(IntSumCombiner.class);
        job.setReducerClass(IntSumReducer.class);

        job.setMapOutputKeyClass(Text.class);
        job.setMapOutputValueClass(IntWritable.class);

        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(Text.class);

        // add the input paths as given by command line
        for (int i = 0; i < otherArgs.length - 1; ++i) {
            FileInputFormat.addInputPath(job, new Path(otherArgs[i]));
        }

        // add the output path as given by the command line
        FileOutputFormat.setOutputPath(job, new Path(otherArgs[otherArgs.length - 1]));

        System.exit(job.waitForCompletion(true) ? 0 : 1);
    }
}