昨天写的代码并不符合MapReduce的思想，今天重新写了一篇
数据：
A:B D E
B:A C F
C:A D E
D:A B C D
F:C D E G
E:A D
共分两次MapReduce过程
第一次MapReduce 得到PeopleA 含有PeopleA好友的所有人的集合
package nuc.edu.ls.friends.Final;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 FindFriend {public static class MapTask extends Mapper<LongWritable, Text, Text, Text>{@Overrideprotected void map(LongWritable key, Text value, Mapper<LongWritable, Text, Text, Text>.Context context)throws IOException, InterruptedException {// TODO Auto-generated method stubString[] split = value.toString().split(":");String[] split2 = split[1].split("\\s+");for (String string : split2) {// PeopleA 谁的好友有Acontext.write(new Text(string),new Text(split[0]));}}}public static class ReduceTask extends Reducer<Text, Text, Text, Text>{@Overrideprotected void reduce(Text arg0, Iterable<Text> arg1, Reducer<Text, Text, Text, Text>.Context context)throws IOException, InterruptedException {// TODO Auto-generated method stubStringBuilder whoFriendHasMe=new StringBuilder();for (Text text : arg1) {String who = text.toString();whoFriendHasMe.append(who+"\t");}//A 好友为A的集合context.write(new Text(arg0.toString()+":"), new Text(whoFriendHasMe.toString()));}}public static void main(String[] args) throws Exception{System.setProperty("HADOOP_USER_NAME", "root");Configuration conf = new Configuration();Job job = Job.getInstance(conf, "eclipseToCluster");job.setMapperClass(MapTask.class);job.setReducerClass(ReduceTask.class);job.setJarByClass(FindFriend.class);//job.setJar("C:\\Users\\LENOVO\\Desktop\\WordCount.jar");job.setMapOutputKeyClass(Text.class);job.setMapOutputValueClass(Text.class);job.setOutputKeyClass(Text.class);job.setOutputValueClass(Text.class);FileInputFormat.addInputPath(job, new Path("d:/friend.txt"));FileOutputFormat.setOutputPath(job, new Path("d:/friendResult1/"));boolean completion = job.waitForCompletion(true);System.out.println(completion ? 0 : 1);}}
运行结果：
第二次MapReduce 得到共同好友
package nuc.edu.ls.friends.Final;import java.io.IOException;import java.util.Arrays;import java.util.List;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 FindFriendFinal {public static class MapTask extends Mapper<LongWritable, Text, Text, Text> {@Overrideprotected void map(LongWritable key, Text value, Mapper<LongWritable, Text, Text, Text>.Context context)throws IOException, InterruptedException {// TODO Auto-generated method stubString[] split = value.toString().split(":");String[] split2 = split[1].split("\t");Arrays.sort(split2);List<String> peopleList = Arrays.asList(split2);for (int i = 0; i < peopleList.size(); i++) {for (int j = i + 1; j < peopleList.size(); j++) {if(peopleList.get(i).length()>0&&peopleList.get(j).length()>0)context.write(new Text(peopleList.get(i) + "与" + peopleList.get(j) + "共同好友"), new Text(split[0]));}}}}public static class ReduceTask extends Reducer<Text, Text, Text, Text>{@Overrideprotected void reduce(Text arg0, Iterable<Text> arg1, Reducer<Text, Text, Text, Text>.Context arg2)throws IOException, InterruptedException {// TODO Auto-generated method stubStringBuilder sb=new StringBuilder();for (Text text : arg1) {sb.append(text.toString()+" ");}arg2.write(arg0, new Text(sb.toString()));}}public static void main(String[] args) throws Exception{System.setProperty("HADOOP_USER_NAME", "root");Configuration conf = new Configuration();Job job = Job.getInstance(conf, "eclipseToCluster");job.setMapperClass(MapTask.class);job.setReducerClass(ReduceTask.class);job.setJarByClass(FindFriendFinal.class);//job.setJar("C:\\Users\\LENOVO\\Desktop\\WordCount.jar");job.setMapOutputKeyClass(Text.class);job.setMapOutputValueClass(Text.class);job.setOutputKeyClass(Text.class);job.setOutputValueClass(Text.class);FileInputFormat.addInputPath(job, new Path("d:/friendResult1/part-r-00000"));FileOutputFormat.setOutputPath(job, new Path("d:/friendResultFinal/"));boolean completion = job.waitForCompletion(true);System.out.println(completion ? 0 : 1);}}
运行结果：
