MapReduce之WordCount

这是我在学习《深入理解Hadoop》中的代码示例，仅作示例用

package edu.hfut.wls.study.hadoop;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.LongWritable;
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.input.TextInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;
import org.apache.hadoop.util.GenericOptionsParser;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;

import java.io.IOException;

/**
 * Created by lianbin.zlb.
 */
public class WordCount extends Configured implements Tool{
    @Override
    public int run(String[] strings) {
        try {
            Job job = Job.getInstance(getConf());
            job.setJarByClass(WordCount.class);

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

            job.setMapperClass(WcMapper.class);
            job.setReducerClass(WcReducer.class);

            job.setInputFormatClass(TextInputFormat.class);
            job.setOutputFormatClass(TextOutputFormat.class);

            String[] args = new GenericOptionsParser(getConf(), strings).getRemainingArgs();

            FileInputFormat.setInputPaths(job, new Path(args[0]));
            FileOutputFormat.setOutputPath(job, new Path(args[1]));
            job.submit();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return 0;
    }

    public static class WcMapper extends Mapper{
        @Override
        protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
            String mVal = value.toString();
            context.write(new Text(mVal), new LongWritable(1));
        }
    }
    public static class WcReducer extends Reducer{
        @Override
        protected void reduce(Text key, Iterable values, Context context) throws IOException, InterruptedException {
            long sum = 0;
            for(LongWritable lVal : values){
                sum += lVal.get();
            }
            context.write(key, new LongWritable(sum));
        }
    }
    public static void main(String[] args) throws Exception {
        Configuration conf = new Configuration();
        ToolRunner.run(new WordCount(), args);
    }
}