xiaoming laowang renhua linzhiling
laowang xiaoming fengjie
renhua xiaoming ligang fengjie
linzhiling xiaoming ligang fengjie guomeimei
ligang renhua fengjie linzhiling
guomeimei fengjie linzhiling
fengjie renhua laowang linzhiling guomeimei

二，编码操作

1.项目建包目录

2.FriendsRecommend.java

package org.hadoop.mr;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;


import java.io.IOException;

public class FriendsRecommend {
    public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {
        Configuration conf = new Configuration();
        Job job = Job.getInstance(conf);

        job.setJarByClass(FriendsRecommend.class);

        Path input = new Path(args[0]);
        FileInputFormat.addInputPath(job, input);

        Path output = new Path(args[1]);
        //如果文件存在,,删除文件,方便后续调试代码
        if (output.getFileSystem(conf).exists(output)) {
            output.getFileSystem(conf).delete(output,true);
        }

        FileOutputFormat.setOutputPath(job, output);

        job.setMapperClass(FriendsRecommendMapper.class);
        job.setMapOutputKeyClass(Text.class);
        job.setOutputValueClass(IntWritable.class);
        job.setReducerClass(FriendsRecommendReduce.class);

        job.waitForCompletion(true);
    }
}

3.FriendsRecommendMapper.java

package org.hadoop.mr;

import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.util.StringUtils;

import java.io.IOException;

public class FriendsRecommendMapper extends Mapper<LongWritable, Text, Text, IntWritable> {
    Text mkey = new Text();
    IntWritable mval = new IntWritable();

    @Override
    protected void map(LongWritable key, Text value, Context context)
            throws IOException, InterruptedException {
        //不能用双引号,要用单引号 将传递过来的值进行分割
        String[] strs = StringUtils.split(value.toString(), ' ');
        // 直接好友的 key为直接好友列表  value为0
        for (int i = 1; i < strs.length; i++) {
            //直接好友关系
            mkey.set(fof(strs[0], strs[i]));
            mval.set(0);
            context.write(mkey, mval);
            //间接好友关系 设置value为1
            for (int j = i + 1; j < strs.length; j++) {
                mkey.set(fof(strs[i], strs[j]));
                mval.set(1);
                context.write(mkey, mval);
            }
        }
    }

    //两个共同好友的间接好友之间,可能存在 B C 和C B 的情况,但是比对累加时,计算机不识别,所以需要字典排序
    private static String fof(String str1, String str2) {
        //compareTo比较的 正数说明大
        if (str1.compareTo(str2) > 0) {
            return str2 + ":" + str1;
        }
        return str1 + ":" + str2;
    }
}

4.FriendsRecommendReduce.java

package org.hadoop.mr;

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

import java.io.IOException;

public class FriendsRecommendReduce extends Reducer<Text, IntWritable, Text, IntWritable> {

    private IntWritable mValue = new IntWritable();

    @Override
    protected void reduce(Text key, Iterable<IntWritable> values, Context context) throws IOException, InterruptedException {

        //
        int flg = 0;
        int sum = 0;
        for (IntWritable value : values) {
            if (value.get() == 0) {// 直接关系
                flg = 1;
            }
            sum += value.get(); // 添加间接权重
        }

        if (flg == 0) {
            mValue.set(sum);
            context.write(key, mValue);
        }
    }
}