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); } }
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(","); 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); } }
测试文件:
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
输出结果:
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,
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