案例需求

a.html
hello world
hello lucy
hello jack
hello liuyan

b.html
hello aaa
aaa bbb
bbb ccc
hello liuyan 
liuyan  tangyan

c.html
world hello 
liuyan tangyan
tangyan aaa
bbb    ccc

计算每个单词在每个文件中出现的次数 
aaa    b.html-2 c.html-1 
bbb    b.html-2 c.html-1 
ccc    b.html-1 
hello    a.html-4 b.html-2 c.html-1 
jack    a.html-1 
liuyan    b.html-2 c.html-1 
lucy    a.html-1 
tangyan    c.html-2 b.html-1 
world    a.html-1 
 

 

需求分析

如图所示,需两次mapreduce

 

 代码

 

package day36.com.doit.demo3;


import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
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.FileSplit;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;

import java.io.IOException;

public class Test {

    private static class IndexMapper extends Mapper<LongWritable, Text,Text, IntWritable> {
        private String fileName;
        @Override
        protected void setup(Context context) throws IOException, InterruptedException {
            FileSplit fileSplit = (FileSplit)context.getInputSplit();
             fileName = fileSplit.getPath().getName();
        }

        Text k2 = new Text();
        IntWritable v2 = new IntWritable();
        @Override
        protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {

            String[] arr = value.toString().split("\\s+");
            for (String s : arr) {
                k2.set(s+"-"+fileName);
                v2.set(1);
                context.write(k2,v2);
            }



        }
    }


    private static class IndexReducer extends Reducer<Text,IntWritable,Text,IntWritable> {

        IntWritable v3 = new 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();
            }
            v3.set(sum);

            context.write(key,v3);
        }
    }

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

        //创建任务
        Job job = Job.getInstance(conf, "index");
        //设置Mapper类
        job.setMapperClass(IndexMapper.class);
        //设置Reduce类
        job.setReducerClass(IndexReducer.class);
        //设置map的输出类型
        job.setMapOutputKeyClass(Text.class);
        job.setMapOutputValueClass(IntWritable.class);

        //设置reduce的输出类型
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(IntWritable.class);

        //设置输入文件位置
        FileInputFormat.setInputPaths(job,new Path("d:\\ideawork\\bbb\\input"));
        //设置输出文件位置
        FileOutputFormat.setOutputPath(job,new Path("d:\\ideawork\\bbb\\output2"));

        //将任务提交 并等待完成
        job.waitForCompletion(true);
    }
}

 

 将第一次输出结果作为第二次的输入

package day36.com.doit.demo3;

import org.apache.hadoop.conf.Configuration;
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.output.FileOutputFormat;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

public class Test2 {

    private static class IndexMapper extends Mapper<LongWritable, Text,Text,Text> {
        Text k2 =new Text();
        Text v2 = new Text();
        @Override
        protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
            String[] arr = value.toString().split("-");
            k2.set(arr[0]);
            v2.set(arr[1].replaceAll("\\s+","-"));
            context.write(k2,v2);

        }
    }

    private static class IndexReducer extends Reducer<Text,Text,Text,Text> {
        Text v3 = new Text();
        @Override
        protected void reduce(Text key, Iterable<Text> values, Context context) throws IOException, InterruptedException {
            List<String> list = new ArrayList<>();


            StringBuilder sb = new StringBuilder();
            for (Text value : values) {
//                sb.append(value.toString()).append(" ");
                list.add(value.toString());

            }
            Collections.sort(list, new Comparator<String>() {
                @Override
                public int compare(String o1, String o2) {
                    return  o2.split("-")[1].compareTo(o1.split("-")[1]);
                }
            });
//            v3.set(sb.toString());
            for (String s : list) {
                sb.append(" "+s);
                v3.set(sb.toString());

            }
            context.write(key,v3);

        }
    }

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

        //创建任务
        Job job = Job.getInstance(conf, "index");
        //设置Mapper类
        job.setMapperClass(IndexMapper.class);
        //设置Reduce类
        job.setReducerClass(IndexReducer.class);
        //设置map的输出类型
        job.setMapOutputKeyClass(Text.class);
        job.setMapOutputValueClass(Text.class);

        //设置reduce的输出类型
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(Text.class);

        //设置输入文件位置
        FileInputFormat.setInputPaths(job,new Path("d:\\ideawork\\bbb\\output2"));
        //设置输出文件位置
        FileOutputFormat.setOutputPath(job,new Path("d:\\ideawork\\bbb\\output2_6"));

        //将任务提交 并等待完成
        job.waitForCompletion(true);
    }

}