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

建立三个hadoop编程类EmployeeSortMain、Employee、EmployeeSortMapper这三个类

对应的java代码如下

实例

EmployeeSortMain

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;public class EmployeeSortMain {public static void main(String[] args) throws Exception{//创建一个jobJob job = Job.getInstance(new Configuration());job.setJarByClass(EmployeeSortMain.class);//指定job的mapper和输出的类型 k2  v2job.setMapperClass(EmployeeSortMapper.class);job.setOutputKeyClass(Employee.class);job.setMapOutputValueClass(NullWritable.class);//指定job的输入和输出的路径FileInputFormat.setInputPaths(job,new Path(args[0]));FileOutputFormat.setOutputPath(job,new Path(args[1]));//提交程序，并且监控打印程序执行的结果boolean b = job.waitForCompletion(true);System.exit(b?0:1);}
}

Employee

import org.apache.hadoop.io.WritableComparable;import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;//1.若要把Employee作为key2，则需要实现序列化
//2.员工对象为Employee类，可被排序
//数据：7654，MARTIN	，SALESMAN，7698，1981/9/28，1250，1400，30
public class Employee implements WritableComparable<Employee> {private int empno;private String ename;private String job;private int mgr;private String hiredate;private int sal;private int comm;private int deptno;@Overridepublic String toString(){return "Employee[empno="+empno+",ename="+ename+",sal="+sal+",deptno="+deptno+"]";}@Overridepublic int compareTo(Employee o) {//多个列的排序：select * from emp order by deptno,sal;//首先按照deptno排序if(this.deptno >o.getDeptno()){return 1;}else if(this.deptno < o.getDeptno()){return -1;}//如果deptno相等，按照sal排序if(this.sal >= o.getSal()){return 1;}else{return -1;}}@Overridepublic void write(DataOutput output) throws IOException {//序列化output.writeInt(this.empno);output.writeUTF(this.ename);output.writeUTF(this.job);output.writeInt(this.mgr);output.writeUTF(this.hiredate);output.writeInt(this.sal);output.writeInt(this.comm);output.writeInt(this.deptno);}@Overridepublic void readFields(DataInput input) throws IOException {//反序列化this.empno = input.readInt();this.ename = input.readUTF();this.job = input.readUTF();this.mgr = input.readInt();this.hiredate = input.readUTF();this.sal = input.readInt();this.comm = input.readInt();this.deptno = input.readInt();}public int getEmpno() {return empno;}public void setEmpno(int empno) {this.empno = empno;}public String getEname() {return ename;}public void setEname(String ename) {this.ename = ename;}public String getJob() {return job;}public void setJob(String job) {this.job = job;}public int getMgr() {return mgr;}public void setMgr(int mgr) {this.mgr = mgr;}public String getHiredate() {return hiredate;}public void setHiredate(String hiredate) {this.hiredate = hiredate;}public int getSal() {return sal;}public void setSal(int sal) {this.sal = sal;}public int getComm() {return comm;}public void setComm(int comm) {this.comm = comm;}public int getDeptno() {return deptno;}public void setDeptno(int deptno) {this.deptno = deptno;}
}

EmployeeSortMapper

import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;
import java.io.IOException;public class EmployeeSortMapper extends Mapper<LongWritable,Text,Employee, NullWritable> {@Overrideprotected void map(LongWritable key1, Text value1, Context context) throws IOException, InterruptedException {//数据：7654，MARTIN	，SALESMAN，7698，1981/9/28，1250，1400，30String data = value1.toString();//分词String[] words = data.split(",");//创建员工对象Employee e = new Employee();//设置员工的属性// 员工号e.setEmpno(Integer.parseInt(words[0]));//姓名e.setEname(words[1]);//职位e.setJob(words[2]);//老板号（注意：可能没有老板号）try{e.setMgr(Integer.parseInt(words[3]));}catch (Exception ex){//没有老板号e.setMgr(-1);}//入职日期e.setHiredate(words[4]);//月薪e.setSal(Integer.parseInt(words[5]));//奖金（注意：奖金也有可能没有）try{e.setComm(Integer.parseInt(words[6]));}catch (Exception ex){//没有奖金e.setComm(0);}//部门号e.setDeptno(Integer.parseInt(words[7]));//输出context.write(e,NullWritable.get());}
}

 代码命令

hadoop jar 3.jar  ch03.EmployeeSortMain  /user/data/input/emp.csv  /user/data/output/ch3
hadoop jar 包名   主类  输入路径  输出路径

结果展示：

 

 学习连接

hadoop编程之工资序列化排序-CSDN博客

hadoop编程之词频统计-CSDN博客

hadoop编程之工资序列化排序-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

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