每日總結

Mapreduce執行個體——去重

依賴：

<dependency>

      <groupId>org.apache.hadoop</groupId>

      <artifactId>hadoop-common</artifactId>

      <version>3.2.0</version>

    </dependency>

    <dependency>

      <artifactId>hadoop-mapreduce-client-app</artifactId>

      <artifactId>hadoop-hdfs</artifactId>

      <groupId>org.slf4j</groupId>

      <artifactId>slf4j-log4j12</artifactId>

      <version>1.7.30</version>

      <artifactId>hadoop-client</artifactId>

</dependency>

package mapreduce;  

import java.io.IOException;  

import org.apache.hadoop.conf.Configuration;  

import org.apache.hadoop.fs.Path;  

import org.apache.hadoop.io.IntWritable;  

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.input.TextInputFormat;  

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

import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;  

public class Filter {

    public static class Map extends Mapper<Object, Text, Text, NullWritable> {

        private static Text newKey = new Text();

        public void map(Object key, Text value, Context context) throws IOException, InterruptedException {

            String line = value.toString();

            System.out.println(line);

            String arr[] = line.split("\t");

            newKey.set(arr[1]);

            context.write(newKey, NullWritable.get());

            System.out.println(newKey);

        }

    }

    public static class Reduce extends Reducer<Text, NullWritable, Text, NullWritable> {

        public void reduce(Text key, Iterable<NullWritable> values, Context context) throws IOException, InterruptedException {

            context.write(key, NullWritable.get());

    public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {

        Configuration conf = new Configuration();

        System.out.println("start");

        Job job = new Job(conf, "filter");

        job.setJarByClass(Filter.class);

        job.setMapperClass(Map.class);

        job.setReducerClass(Reduce.class);

        job.setOutputKeyClass(Text.class);

        job.setOutputValueClass(NullWritable.class);

        job.setInputFormatClass(TextInputFormat.class);

        job.setOutputFormatClass(TextOutputFormat.class);

        Path in = new Path("hdfs://hadoop102:8020/mymapreduce2/in/buyer_favorite1");

        Path out = new Path("hdfs://hadoop102:8020/mymapreduce2/out");

        FileInputFormat.addInputPath(job, in);

        FileOutputFormat.setOutputPath(job, out);

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

}