数据集展示

7369	SMITH	CLERK	7902	1980/12/17	800		20
7499	ALLEN	SALESMAN	7698	1981/2/20	1600	300	30
7521	WARD	SALESMAN	7698	1981/2/22	1250	500	30
7566	JONES	MANAGER	7839	1981/4/2	2975		20
7654	MARTIN	SALESMAN	7698	1981/9/28	1250	1400	30
7698	BLAKE	MANAGER	7839	1981/5/1	2850		30
7782	CLARK	MANAGER	7839	1981/6/9	2450		10
7788	SCOTT	ANALYST	7566	1987/4/19	3000		20
7839	KING	PRESIDENT		1981/11/17	5000		10
7844	TURNER	SALESMAN	7698	1981/9/8	1500	0	30
7876	ADAMS	CLERK	7788	1987/5/23	1100		20
7900	JAMES	CLERK	7698	1981/12/3	950		30
7902	FORD	ANALYST	7566	1981/12/3	3000		20
7934	MILLER	CLERK	7782	1982/1/23	1300		10

 建立不同的java类

SalaryTotalMain、SalaryTotalMapper、SalaryTotalReducer这三个类

对应代码如下：

SalaryTotalMain

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.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
public class SalaryTotalMain {public static void main(String[] args) throws Exception {Configuration conf = new Configuration();Job job = Job.getInstance(conf);job.setJarByClass(SalaryTotalMain.class);job.setMapperClass(SalaryTotalMapper.class);job.setReducerClass(SalaryTotalReducer.class);job.setMapOutputKeyClass(LongWritable.class);job.setMapOutputValueClass(LongWritable.class);job.setOutputKeyClass(LongWritable.class);job.setOutputValueClass(LongWritable.class);FileInputFormat.setInputPaths(job, new Path(args[0]));FileOutputFormat.setOutputPath(job, new Path(args[1]));job.waitForCompletion(true);}
}

SalaryTotalMapper

import java.io.IOException;
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.mapreduce.Mapper.Context;
public class SalaryTotalMapper extends Mapper<LongWritable,Text, LongWritable, LongWritable> {@Overrideprotected void map(LongWritable key1,Text value1, Context context)throws IOException, InterruptedException {String data = value1.toString();String[] words = data.split(",");context.write(new LongWritable(Integer.parseInt(words[7])),new LongWritable(Integer.parseInt(words[5])));}}

SalaryTotalReducer

import java.io.IOException;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.Reducer.Context;
public class SalaryTotalReducer extends Reducer<LongWritable, LongWritable,LongWritable, LongWritable> {@Overrideprotected void reduce(LongWritable k3, Iterable<LongWritable> v3,Context context) throws IOException,InterruptedException {long  total = 0;long  max = 0;for(LongWritable v:v3){total=v.get();if(max<total){max=total;}}context.write(k3, new LongWritable(max));}}

命令

hadoop jar 2.jar  ch02.SalaryTotalMain  /user/data/input/emp.csv  /user/data/output/ch2
hadoop jar 包名   主类  输入路径 输出路径

对应结果

 

 学习链接

在Ubuntu上用mapreduce进行词频统计（伪分布式）_mapreduce怎么统计txt文件词频终端-CSDN博客

利用mapreduce统计部门的最高工资_使用mapreduce查询某个部门中薪资最高的员工姓名,如果输出结果的格式为“薪资 员-CSDN博客

hadoop编程之工资序列化排序-CSDN博客

 hadoop编程之部门工资求和-CSDN博客

hadoop编程之词频统计-CSDN博客