mapreduce实现社交中共同好友

测试数据中给了一个单向的一个用户有哪些好友，

A:B,C,D,F,E,O
B:A,C,E,K
C:F,A,D,I
D:A,E,F,L
E:B,C,D,M,L
F:A,B,C,D,E,O,M
G:A,C,D,E,F
H:A,C,D,E,O
I:A,O
J:B,O
K:A,C,D
L:D,E,F
M:E,F,G
O:A,H,I,J

//先求 单向的 哪些人加了该用户为好友

package cn.itcast.bigdata.mr.fensi;

import java.io.IOException;

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;

public class SharedFriendsStepOne {

    static class SharedFriendsStepOneMapper extends Mapper<LongWritable, Text, Text, Text> {

        @Override
        protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
            // A:B,C,D,F,E,O
            String line = value.toString();
            String[] person_friends = line.split(":");
            String person = person_friends[0];
            String friends = person_friends[1];

            for (String friend : friends.split(",")) {

                // 输出<好友，人>
                context.write(new Text(friend), new Text(person));
            }

        }

    }

    static class SharedFriendsStepOneReducer extends Reducer<Text, Text, Text, Text> {

        @Override
        protected void reduce(Text friend, Iterable<Text> persons, Context context) throws IOException, InterruptedException {

            StringBuffer sb = new StringBuffer();

            for (Text person : persons) {
                sb.append(person).append(",");

            }
            context.write(friend, new Text(sb.toString()));
        }

    }

    public static void main(String[] args) throws Exception {

        Configuration conf = new Configuration();

        Job job = Job.getInstance(conf);
        job.setJarByClass(SharedFriendsStepOne.class);

        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(Text.class);
        
        job.setMapperClass(SharedFriendsStepOneMapper.class);
        job.setReducerClass(SharedFriendsStepOneReducer.class);

        FileInputFormat.setInputPaths(job, new Path("D:/srcdata/friends"));
        FileOutputFormat.setOutputPath(job, new Path("D:/temp/out"));

        job.waitForCompletion(true);

    }

}

//求共同好友

package cn.itcast.bigdata.mr.fensi;

import java.io.IOException;
import java.util.Arrays;

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;

public class SharedFriendsStepTwo {

    static class SharedFriendsStepTwoMapper extends Mapper<LongWritable, Text, Text, Text> {

        // 拿到的数据是上一个步骤的输出结果
        // A I,K,C,B,G,F,H,O,D,
        // 友 人，人，人
        @Override
        protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {

            String line = value.toString();
            String[] friend_persons = line.split("	");

            String friend = friend_persons[0];
            String[] persons = friend_persons[1].split(",");

            Arrays.sort(persons);

            for (int i = 0; i < persons.length - 1; i++) {
                for (int j = i + 1; j < persons.length; j++) {
                    // 发出 <人-人，好友> ，这样，相同的“人-人”对的所有好友就会到同1个reduce中去
                    context.write(new Text(persons[i] + "-" + persons[j]), new Text(friend));
                }

            }

        }

    }

    static class SharedFriendsStepTwoReducer extends Reducer<Text, Text, Text, Text> {

        @Override
        protected void reduce(Text person_person, Iterable<Text> friends, Context context) throws IOException, InterruptedException {

            StringBuffer sb = new StringBuffer();

            for (Text friend : friends) {
                sb.append(friend).append(" ");

            }
            context.write(person_person, new Text(sb.toString()));
        }

    }

    public static void main(String[] args) throws Exception {

        Configuration conf = new Configuration();

        Job job = Job.getInstance(conf);
        job.setJarByClass(SharedFriendsStepTwo.class);

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

        job.setMapperClass(SharedFriendsStepTwoMapper.class);
        job.setReducerClass(SharedFriendsStepTwoReducer.class);

        FileInputFormat.setInputPaths(job, new Path("D:/temp/out/part-r-00000"));
        FileOutputFormat.setOutputPath(job, new Path("D:/temp/out2"));

        job.waitForCompletion(true);

    }

}