hadoop-mr程式設計1-WordCount

程式設計題1：編寫一個WordCount程式

Mapper

import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;
import java.io.IOException;

public class WcountMapper extends Mapper<LongWritable,Text,Text,IntWritable> {

    @Override
    protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {

        String s = value.toString();
        String[] split = s.split(" ");
        for (String s1 : split) {
            context.write(new Text(s1), new IntWritable(1));
        }
    }
}
           

Reducer

import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Reducer;
import java.io.IOException;

public class WcountReducer extends Reducer<Text,IntWritable,Text,IntWritable> {
    
    @Override
    protected void reduce(Text key, Iterable<IntWritable> values, Context context) throws IOException, InterruptedException {

        int sum = 0;
        for (IntWritable value : values) {
            sum += value.get();
        }
        context.write(key,new IntWritable(sum));
    }
}
           

driver

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.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;

import java.io.IOException;

public class WcountDriver {
    public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {
        Configuration entries = new Configuration();
        Job job = Job.getInstance(entries);

        job.setJarByClass(WcountDriver.class);
        job.setMapperClass(WcountMapper.class);
        job.setReducerClass(WcountReducer.class);

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

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

        FileInputFormat.setInputPaths(job,new Path("F:\\data\\input\\KvText.txt"));
        FileOutputFormat.setOutputPath(job,new Path("F:\\data\\outputdata\\output1"));

        job.waitForCompletion(true);
    }
}