mapreduce系列（7）--查找共同好友

一、概述

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是谁

比如:

a-b :  c ,e

思路：

首先可以第一步可以把朋友作为key，人作为value，形成：友–>人，人，人。这样的中间结果

第二把，把（人，人，人）进行排序，避免重复，然后进行两两匹配形成：(人-人）–>友。这样的键值对，进行mr统计，最后结果就是两两的共同好友了

第一步代码：

SharedFriendsStepOne.java

package friends;

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.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.net.URI;
import java.net.URISyntaxException;

/**
* Created by tianjun on 2017/3/20.
*/
public class SharedFriendsStepOne {

static class SharedFriendsStepOneMapper extends Mapper<LongWritable,Text,Text,Text> {
Text k = new Text();
Text v = new Text();
@Override
protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
String line = value.toString();
String[] person_friends = line.split(":");
String person = person_friends[0];
String[] friends = person_friends[1].split(",");
for(String friend : friends){
k.set(friend);
v.set(person);
//<好友，人>
context.write(k,v);
}
}
}

static class SharedFriendsStepOneReduce 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){
if(sb.length()!=0){
sb.append(",");
}
sb.append(person);
}
context.write(friend,new Text(sb.toString()));
}
}

public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException, URISyntaxException {
String os = System.getProperty("os.name").toLowerCase();
if (os.contains("windows")) {
System.setProperty("HADOOP_USER_NAME", "root");
}

Configuration conf = new Configuration();

conf.set("mapreduce.framework.name","yarn");
conf.set("yarn.resourcemanager.hostname","mini01");
conf.set("fs.defaultFS","hdfs://mini01:9000/");

//            默认就是local模式
//        conf.set("mapreduce.framework.name","local");
//        conf.set("mapreduce.jobtracker.address","local");
//        conf.set("fs.defaultFS","file:///");

Job wcjob = Job.getInstance(conf);

wcjob.setJar("F:/myWorkPlace/java/dubbo/demo/dubbo-demo/mr-demo1/target/mr.demo-1.0-SNAPSHOT.jar");

//如果从本地拷贝，是不行的，这时需要使用setJar
//        wcjob.setJarByClass(Rjoin.class);

wcjob.setMapperClass(SharedFriendsStepOneMapper.class);
wcjob.setReducerClass(SharedFriendsStepOneReduce.class);

//设置我们的业务逻辑Mapper类的输出key和value的数据类型
wcjob.setMapOutputKeyClass(Text.class);
wcjob.setMapOutputValueClass(Text.class);

//设置我们的业务逻辑Reducer类的输出key和value的数据类型
wcjob.setOutputKeyClass(Text.class);
wcjob.setOutputValueClass(Text.class);

//如果不设置InputFormat，默认就是使用TextInputFormat.class
//        wcjob.setInputFormatClass(CombineFileInputFormat.class);
//        CombineFileInputFormat.setMaxInputSplitSize(wcjob,4194304);
//        CombineFileInputFormat.setMinInputSplitSize(wcjob,2097152);

FileSystem fs = FileSystem.get(new URI("hdfs://mini01:9000"), new Configuration(), "root");
Path path = new Path("hdfs://mini01:9000/wc/friends/stepone");
if (fs.exists(path)) {
fs.delete(path, true);
}

//指定要处理的数据所在的位置
FileInputFormat.setInputPaths(wcjob, new Path("hdfs://mini01:9000/input/friends"));
//指定处理完成之后的结果所保存的位置
FileOutputFormat.setOutputPath(wcjob, new Path("hdfs://mini01:9000/wc/friends/stepone"));

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

}

计算结果：

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

为了防止b–>c和c–>b这样同一对朋友的重复，所以，下面基于这个结果处理的时候，需要进行排序，这样就能达到没有重复朋友对的出现。

第二步：

SharedFriendsStepTwo.java

package friends;

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.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.net.URI;
import java.net.URISyntaxException;
import java.util.Arrays;

/**
* Created by tianjun on 2017/3/20.
*/
public class SharedFriendsStepTwo {

static class SharedFriendsStepTwoMapper extends Mapper<LongWritable,Text,Text,Text> {
Text k = new Text();
Text v = new Text();
@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
Arrays.sort(persons);
for(int i = 0 ; i<persons.length-2;i++){
for(int j=i+1;j<persons.length-1;j++){
//<人-人,好友> ,这样相同的“人-人”对好友发到一起了
context.write(new Text(persons[i]+"-"+persons[j]),new Text(friend));
}
}
}
}

static class SharedFriendsStepTwoReduce 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 IOException, ClassNotFoundException, InterruptedException, URISyntaxException {
String os = System.getProperty("os.name").toLowerCase();
if (os.contains("windows")) {
System.setProperty("HADOOP_USER_NAME", "root");
}

Configuration conf = new Configuration();

conf.set("mapreduce.framework.name","yarn");
conf.set("yarn.resourcemanager.hostname","mini01");
conf.set("fs.defaultFS","hdfs://mini01:9000/");

//            默认就是local模式
//        conf.set("mapreduce.framework.name","local");
//        conf.set("mapreduce.jobtracker.address","local");
//        conf.set("fs.defaultFS","file:///");

Job wcjob = Job.getInstance(conf);

wcjob.setJar("F:/myWorkPlace/java/dubbo/demo/dubbo-demo/mr-demo1/target/mr.demo-1.0-SNAPSHOT.jar");

//如果从本地拷贝，是不行的，这时需要使用setJar
//        wcjob.setJarByClass(Rjoin.class);

wcjob.setMapperClass(SharedFriendsStepTwoMapper.class);
wcjob.setReducerClass(SharedFriendsStepTwoReduce.class);

//设置我们的业务逻辑Mapper类的输出key和value的数据类型
wcjob.setMapOutputKeyClass(Text.class);
wcjob.setMapOutputValueClass(Text.class);

//设置我们的业务逻辑Reducer类的输出key和value的数据类型
wcjob.setOutputKeyClass(Text.class);
wcjob.setOutputValueClass(Text.class);

//如果不设置InputFormat，默认就是使用TextInputFormat.class
//        wcjob.setInputFormatClass(CombineFileInputFormat.class);
//        CombineFileInputFormat.setMaxInputSplitSize(wcjob,4194304);
//        CombineFileInputFormat.setMinInputSplitSize(wcjob,2097152);

FileSystem fs = FileSystem.get(new URI("hdfs://mini01:9000"), new Configuration(), "root");
Path path = new Path("hdfs://mini01:9000/wc/friends/steptwo");
if (fs.exists(path)) {
fs.delete(path, true);
}

//指定要处理的数据所在的位置
FileInputFormat.setInputPaths(wcjob, new Path("hdfs://mini01:9000/wc/friends/stepone"));
//指定处理完成之后的结果所保存的位置
FileOutputFormat.setOutputPath(wcjob, new Path("hdfs://mini01:9000/wc/friends/steptwo"));

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

}

最后计算得出的两俩好友如下：

[root@mini03 ~]# hdfs dfs -cat /wc/friends/steptwo/*
A-B     C E
A-C     F D
A-D     E F
A-E     B C D
A-F     C D B E O
A-G     D E F C
A-H     E O C D
A-I     O
A-K     D
A-L     F E
B-C     A
B-D     E A
B-E     C
B-F     E A C
B-G     C E A
B-H     E C A
B-I     A
B-K     A
B-L     E
C-D     F A
C-E     D
C-F     D A
C-G     F A D
C-H     A D
C-I     A
C-K     D A
C-L     F
D-F     E A
D-G     A E F
D-H     A E
D-I     A
D-K     A
D-L     F E
E-F     C D B
E-G     D C
E-H     D C
E-K     D
F-G     C E D A
F-H     C A D E O
F-I     A O
F-K     D A
F-L     E
G-H     D E C A
G-I     A
G-K     A D
G-L     F E
H-I     A O
H-K     A D
H-L     E
I-K     A