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wordcount数据去重案例

package com.Practice.RemoveDupData;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.NullWritable;
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;
<!---more--->
import java.io.IOException;

/**
 * 题目:数据去重
 * 解题思路:将每行数据作为key值,value值为空
 *  2012-3-1 a
    2012-3-2 b
    2012-3-3 c
    2012-3-4 d
    2012-3-5 a
    2012-3-6 b
    2012-3-7 c
    2012-3-3 c
    2012-3-1 b
    2012-3-2 a
    2012-3-3 b
    2012-3-4 d
    2012-3-5 a
    2012-3-6 c
    2012-3-7 d
    2012-3-3 c
 */
public class RemoveDupData {

    public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {
        Configuration conf = new Configuration();
        FileSystem fs = FileSystem.get(conf);

        Job job = Job.getInstance(conf);
        job.setJar("wordcountJar/wordcount.jar");

        job.setMapperClass(RemoveDupDataMapper.class);
        job.setReducerClass(RemoveDupDataReducer.class);

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

        Path inputPath = new Path("input/RemoveDupData");
        Path outputPath = new Path("output/RemoveDupData");


        if(fs.isDirectory(outputPath)){
            fs.delete(outputPath,true);
        }
        FileInputFormat.setInputPaths(job,inputPath);
        FileOutputFormat.setOutputPath(job,outputPath);

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

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

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

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