要实现这一点，您必须使用减速器。原因是，你想要所有的记录 eid 去同一个减速机和所有的记录 ename 转到同一个减速器。这将帮助您聚合 eid 以及 ename .
如果您只是使用Map器（不带还原器），那么可能 eid 我可以去找不同的制图员。
以下代码实现了这一点：

package com.myorg.hadooptests;    

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.*;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;

import java.io.IOException;
import java.util.Iterator;

public class EidTest {

    public static class EidTestMapper
            extends Mapper<LongWritable, Text , Text, Text > {

        public void map(LongWritable key, Text value, Context context)
                throws IOException, InterruptedException {

            String line = value.toString();
            String[] words = line.split("\t");

            if(words.length == 2) {
                context.write(new Text("eid"), new Text(words[0]));
                context.write(new Text("ename"), new Text(words[1]));
            }
        }
    }

    public static class EidTestReducer
            extends Reducer<Text, Text, Text, Text> {

        public void reduce(Text key, Iterable<Text> values, Context context)
                throws IOException, InterruptedException {

            String finalVal = "";

            for (Text val : values) {
                finalVal = finalVal.concat(val.toString()).concat(",");
            }

            finalVal = finalVal.substring(0, finalVal.length() - 1); // Remove trailing comma
            context.write(key, new Text(finalVal));
        }
    }

    public static void main(String[] args) throws Exception {

        Configuration conf = new Configuration();

        Job job = Job.getInstance(conf, "EidTest");
        job.setJarByClass(WordCount.class);
        job.setMapperClass(EidTestMapper.class);
        job.setReducerClass(EidTestReducer.class);

        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(Text.class);

        FileInputFormat.addInputPath(job, new Path("/in/in9.txt"));
        FileOutputFormat.setOutputPath(job, new Path("/out/"));

        job.waitForCompletion(true);
    }
}

对于您的输入，我得到了输出（Map器假设键/值是用tab分隔的）：

eid     3,2,1
ename   c,b,a