WordDistinct

(1)WordDistinctMappper

package s27;

import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;

import java.io.IOException;

public class WordDistinctMapper extends Mapper<LongWritable,Text,Text,NullWritable>{
public void map(LongWritable key, Text value, Context context) throws IOException,InterruptedException {
context.write(value,NullWritable.get());
}
}

(2)WordDistinctReduce

package s27;

import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Reducer;

import java.io.IOException;

public class WordDistinctReducer extends Reducer<Text,NullWritable,Text,NullWritable> {
public void reduce(Text key,Iterable values,Context context) throws IOException,InterruptedException {
context.write(key,NullWritable.get());
}

}

(3)WordDistinctJob

package s27;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.NullWritable;
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 WordDistinctJob {
public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {
Configuration conf=new Configuration();
conf.set("fs.defaultFS","hdfs://master:9000");

    Job job= Job.getInstance(conf);

    job.setJarByClass(WordDistinctJob.class);
    job.setMapperClass(WordDistinctMapper.class);
    job.setReducerClass(WordDistinctReducer.class);

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

    Path pin=new Path("/sw");
    Path pout=new Path("/out");

    FileSystem fs=FileSystem.get(conf);
    if(fs.exists(pout)){
        fs.delete(pout,true);
    }

    FileInputFormat.setInputPaths(job,pin);
    FileOutputFormat.setOutputPath(job,pout);

    job.waitForCompletion(true);

}

}

WordDistinct

原文：https://www.cnblogs.com/Song-wei/p/13902086.html