【Hadoop离线基础总结】MapReduce 社交粉丝数据分析 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？

MapReduce 社交粉丝数据分析

---

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？

• 用户及好友数据

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

• java代码

需要两步完成需求

首先先创建第一步的package

在package中定义main、Mapper、Reducer三个类

定义一个Mapper类

package cn.itcast.demo1.step1;

import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;

import java.io.IOException;

public class Step1Mapper extends Mapper<LongWritable, Text, Text, Text> {
    @Override
    protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
        //输入数据如下格式  A:B,C,D,E,O
        //将用户和好友列表分开
        String[] split = value.toString().split(":");
        //将好友列表分开，放到一个数组中去
        String[] friendList = split[1].split(",");
        //循环遍历，输出的k2,v2格式为 B [A,E]
        for (String friend : friendList) {
            context.write(new Text(friend), new Text(split[0]));
        }
    }
}

定义一个Reducer类

package cn.itcast.demo1.step1;

import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Reducer;

import java.io.IOException;

public class Step1Reducer extends Reducer<Text,Text,Text,Text> {
    /*
    reduce接收到数据是 B [A,E]
    B是好友，集合里面装的是多个用户
    将数据最终转换成这样的形式进行输出 A-B-E-F-G-H-K-  C
     */
    @Override
    protected void reduce(Text key, Iterable<Text> values, Context context) throws IOException, InterruptedException {
        //创建StringBuffer对象
        StringBuffer sb = new StringBuffer();
        //循环遍历得到v2并拼接成字符串
        for (Text value : values) {
            sb.append(value.toString()).append("-");
        }
        context.write(new Text(sb.toString()),key);
    }
}

程序main函数入口

package cn.itcast.demo1.step1;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.lib.input.TextInputFormat;
import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;

public class Step1Main extends Configured implements Tool {
    @Override
    public int run(String[] args) throws Exception {
        //创建job对象
        Job job = Job.getInstance(super.getConf(), "step1");
        //输入数据，设置输入路径
        job.setInputFormatClass(TextInputFormat.class);
        TextInputFormat.setInputPaths(job, new Path("file:////Volumes/赵壮备份/大数据离线课程资料/5.大数据离线第五天/共同好友/input/friends.txt"));

        //自定义map逻辑
        job.setMapperClass(Step1Mapper.class);
        //设置k2,v2输出类型
        job.setMapOutputKeyClass(Text.class);
        job.setMapOutputValueClass(Text.class);

        //自定义reduce逻辑
        job.setReducerClass(Step1Reducer.class);
        //设置k3,v3输出类型
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(Text.class);

        //输出数据，设置输出路径
        job.setOutputFormatClass(TextOutputFormat.class);
        TextOutputFormat.setOutputPath(job, new Path("file:////Volumes/赵壮备份/大数据离线课程资料/5.大数据离线第五天/共同好友/step1_output"));

        //将任务提交至集群
        boolean b = job.waitForCompletion(true);
        return b ? 0 : 1;
    }

    public static void main(String[] args) throws Exception {
        int run = ToolRunner.run(new Configuration(), new Step1Main(), args);
        System.exit(run);
    }
}

运行完成后，得到第一步的数据

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

创建第二步的package

在package中定义main、Mapper、Reducer三个类

定义一个Mapper类

package cn.itcast.demo1.step2;

import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;

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

public class Step2Mapper extends Mapper<LongWritable, Text, Text, Text> {
    @Override
    protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
        //对拿到的数据进行分割，得到用户列表和好友
        String[] split = value.toString().split("\t");
        //再对用户列表进行分割，得到用户列表数组
        String[] userList = split[0].split("-");
        //因为文件中的数据并不是按照字典顺序进行排序，所以有可能会出来A-E E-A的情况，reduceTask是无法将这种情况视为key相同的
        //所以需要进行排序
        Arrays.sort(userList);
        for (int i = 0; i < userList.length - 1; i++) {
            for (int j = i + 1; j < userList.length; j++) {
                String userTwo = userList[i] + "-" + userList[j];
                context.write(new Text(userTwo), new Text(split[1]));
            }
        }
    }
}

定义一个reducer类

package cn.itcast.demo1.step2;

import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Reducer;

import java.io.IOException;

public class Step2Reducer extends Reducer<Text, Text, Text, Text> {
    @Override
    protected void reduce(Text key, Iterable<Text> values, Context context) throws IOException, InterruptedException {
        //创建StringBuffer对象
        StringBuffer sb = new StringBuffer();
        for (Text value : values) {
            //获取共同好友列表
            sb.append(value.toString()).append("-");
        }
        context.write(key, new Text(sb.toString()));
    }
}

程序main函数入口

package cn.itcast.demo1.step2;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.lib.input.TextInputFormat;
import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;

public class Step2Main extends Configured implements Tool {
    @Override
    public int run(String[] args) throws Exception {
        //创建job对象
        Job job = Job.getInstance(super.getConf(), "step2");
        //输入数据，设置输入路径
        job.setInputFormatClass(TextInputFormat.class);
        TextInputFormat.setInputPaths(job, new Path("file:////Volumes/赵壮备份/大数据离线课程资料/5.大数据离线第五天/共同好友/step1_output"));

        //自定义map逻辑
        job.setMapperClass(Step2Mapper.class);
        //设置k2,v2输出类型
        job.setMapOutputKeyClass(Text.class);
        job.setMapOutputValueClass(Text.class);

        //自定义reduce逻辑
        job.setReducerClass(Step2Reducer.class);
        //设置k3,v3输出类型
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(Text.class);

        //输出数据，设置输出路径
        job.setOutputFormatClass(TextOutputFormat.class);
        TextOutputFormat.setOutputPath(job, new Path("file:////Volumes/赵壮备份/大数据离线课程资料/5.大数据离线第五天/共同好友/step2_output"));

        //提交任务至集群
        boolean b = job.waitForCompletion(true);
        return b ? 0 : 1;
    }

    public static void main(String[] args) throws Exception {
        int run = ToolRunner.run(new Configuration(), new Step2Main(), args);
        System.exit(run);
    }
}

运行结果为

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