com.ckelsel.hadoop.mapreduce.WordCount.WordCount.java Source code

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Here is the source code for com.ckelsel.hadoop.mapreduce.WordCount.WordCount.java

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/**-------------------------------------------------------------------------
 * Copyright (C) 2015 KunMing Xie <kunming.xie@hotmail.com>
 * 
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */
package com.ckelsel.hadoop.mapreduce.WordCount;

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;

import java.io.IOException;

public class WordCount {

    public static class MyMapper extends Mapper<Object, Text, Text, IntWritable> {
        private final static IntWritable one = new IntWritable(1);
        private Text event = new Text();

        public void map(Object key, Text value, Context context) throws IOException, InterruptedException {
            int idx = value.toString().indexOf(" ");
            if (idx > 0) {
                String e = value.toString().substring(0, idx);
                event.set(e);
                context.write(event, one);
            }
        }
    }

    public static class MyReducer 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);
        }
    }

    public static void main(String[] args) throws Exception {
        Configuration conf = new Configuration();
        String[] otherArgs = new GenericOptionsParser(conf, args).getRemainingArgs();
        if (otherArgs.length < 2) {
            System.err.println("Usage: EventCount <in> <out>");
            System.exit(2);
        }
        Job job = Job.getInstance(conf, "event count");
        job.setJarByClass(WordCount.class);
        job.setMapperClass(MyMapper.class);
        job.setCombinerClass(MyReducer.class);
        job.setReducerClass(MyReducer.class);
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(IntWritable.class);
        FileInputFormat.addInputPath(job, new Path(otherArgs[0]));

        // delete output if exists
        Path outPath = new Path(otherArgs[1]);
        outPath.getFileSystem(conf).delete(outPath, true);
        FileOutputFormat.setOutputPath(job, outPath);
        System.exit(job.waitForCompletion(true) ? 0 : 1);
    }
}