Hadoop_24_MapReduce实现QQ共同好友

1.社交粉丝数据分析：

以下是qq的好友列表数据，冒号前是一个用户，冒号后是该用户的所有好友（数据中的好友关系是单向的）

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

求出哪些人两两之间有共同好友，及他俩的共同好友都有谁？

解题思路：如果想要得到两两之间的共同好友，若A和B的共同好友是C，通过反向思考，可以求出C是哪些人的共同好友，然后将这些共同好友

　　　　  两两组合；

c --> a  b  e  f g  h  k （第一步：找出c的所有共同好友）

a-b  c

a-e  c  （第二步：作为key,即可得到a-e的共同好友c和d）

d --> a  c  e  f g  h  k

a-c  d

a-e  d

第一步代码实现：

package cn.bigdata.hdfs.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(找出具有共同好友的都是哪些人的)

            String line = value.toString();

            String[] person_friends = line.split(":");

            String person = person_friends[0];

            String feiends = person_friends[1];

            for(String friend : feiends.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 {

            //persons:具有共同好友的所有人：c --> a b e f g h k

            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(args[0]));

        FileOutputFormat.setOutputPath(job, new Path(args[1]));

        job.waitForCompletion(true);

    }

}

运行结果：

A    I,K,C,B,G,F,H,O,D,

B    A,F,J,E,

C    A,E,B,H,F,G,K,

D    G,C,K,A,L,F,E,H,

E    G,M,L,H,A,F,B,D,

F    L,M,D,C,G,A,

G    M,

H    O,

I    O,C,

J    O,

K    B,

L    D,E,

M    E,F,

O    A,H,I,J,F,

第二步代码实现：具有共同好友的人两两作为key输出

package cn.bigdata.hdfs.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("\t");

            String friend = friend_persons[0];

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

            //排序，使得B-C和C-B不重复

            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("F:/fensiOutput/part-r-00000"));

        FileOutputFormat.setOutputPath(job, new Path("F:/fensiOutput4"));

        job.waitForCompletion(true);

    }

}

运行结果：

A-B    E C

A-C    D F

A-D    E F

A-E    D B C

A-F    O B C D E

A-G    F E C D

A-H    E C D O

A-I    O

A-J    O B

A-K    D C

A-L    F E D

A-M    E F

B-C    A

B-D    A E

B-E    C

B-F    E A C

B-G    C E A

B-H    A E C

B-I    A

B-K    C A

B-L    E

B-M    E

B-O    A

C-D    A F

C-E    D

C-F    D A

C-G    D F A

C-H    D A

C-I    A

C-K    A D

C-L    D F

C-M    F

C-O    I A

D-E    L

D-F    A E

D-G    E A F

D-H    A E

D-I    A

D-K    A

D-L    E F

D-M    F E

D-O    A

E-F    D M C B

E-G    C D

E-H    C D

E-J    B

E-K    C D

E-L    D

F-G    D C A E

F-H    A D O E C

F-I    O A

F-J    B O

F-K    D C A

F-L    E D

F-M    E

F-O    A

G-H    D C E A

G-I    A

G-K    D A C

G-L    D F E

G-M    E F

G-O    A

H-I    O A

H-J    O

H-K    A C D

H-L    D E

H-M    E

H-O    A

I-J    O

I-K    A

I-O    A

K-L    D

K-O    A

L-M    E F