指导参考图：

一、源代码

1.UserSaleMapper类

package org.example.writable;

import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;
import org.example.model.UserSale;

import java.io.IOException;

public class UserSaleMapper extends Mapper<LongWritable, Text,Text, UserSale> {

    //map阶段输出的key类型
    private Text outputKey =new Text();

    @Override
    protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
        //获取一行文本数据
        String line = value.toString();
        //根据分隔符进行数据拆分
        String[] split = line.split( ",");
        //根据下标获取数据
        String saleld = split[0] ;
        String userName = split[1];
        String goodsName = split[2];
        String price = split[3] ;
        String saleCount = split[4];

        //对对象封装
        UserSale userSale = new UserSale();

        userSale.setSaleId(Integer. parseInt(saleld));
        userSale.setUserName (userName);
        userSale.setGoodsName(goodsName);
        userSale.setPrice(Integer.parseInt(price));
        userSale.setSaleCount(Integer.parseInt(saleCount));
        userSale.setTotalPrice(Integer.parseInt(price)*Integer.parseInt(saleCount));

        //封装输出的key
        outputKey.set (userName);

        //map阶段进行输出
        context.write(outputKey, userSale);

    }
}

2. UserSaleReducer类

package org.example.writable;

import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Reducer;
import org.example.model.UserSale;

import java.io.IOException;

public class UserSaleReducer extends Reducer<Text, UserSale,Text,UserSale> {

    //创建reducer阶段输出的对象
    private UserSale outputUser = new UserSale();

    @Override
    protected void reduce(Text key, Iterable<UserSale> values, Context context) throws IOException, InterruptedException {

        Integer totalPrice = 0;
        //遍历集合，进行总金额的累加

        for (UserSale userSale : values){
            totalPrice += userSale.getTotalPrice();
        }

        //对输出对象进行封装
        outputUser.setTotalPrice(totalPrice);

        // reduce阶段输出
        context.write(key,outputUser);

    }
}

3. UserSaleDriver类

package org.example.writable;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
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;
import org.example.model.UserSale;

import java.io.IOException;

public class UserSaleDriver {
    public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {

        // 1获取配置对象和job对象
        Configuration conf = new Configuration();
        Job job = Job. getInstance(conf);

        // 2关联Driver类
        job.setJarByClass(UserSaleDriver.class);

        // 3关联mapper和reducer类
        job.setMapperClass(UserSaleMapper.class);
        job.setReducerClass(UserSaleReducer.class);

        // 4设置mapper阶段输出的k, v类型
        job.setMapOutputKeyClass(Text.class);
        job.setMapOutputValueClass(UserSale.class);

        // 5设置最终输出的k, v类型
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(UserSale.class);

        // 6设置文件的输入路径和输出路径
        FileInputFormat. setInputPaths(job, new Path( "D:\\Documentation\\sale_detail.txt"));
        // 注意：输出目录需不存在，填入已存在的目录会报错
        FileOutputFormat. setOutputPath(job, new Path(  "D:\\Documentation\\output3"));

        // 7提交任务
        boolean result = job. waitForCompletion(true) ;
        System.out. println(result?"任务执行成功":"任务执行失败");




    }
}

4.pom.xml

<?xml version="1.0" encoding="UTF-8"?>

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>org.example</groupId>
  <artifactId>mapreduce_demo</artifactId>
  <version>1.0-SNAPSHOT</version>

  <name>mapreduce_demo</name>
  <!-- FIXME change it to the project's website -->
  <url>http://www.example.com</url>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.source>1.8</maven.compiler.source>
    <maven.compiler.target>1.8</maven.compiler.target>
  </properties>

  <dependencies>
    <!-- https://mvnrepository.com/artifact/org.apache.hadoop/hadoop-client -->
    <dependency>
      <groupId>org.apache.hadoop</groupId>
      <artifactId>hadoop-client</artifactId>
      <version>3.1.3</version>
    </dependency>

  </dependencies>
  <build>
    <plugins>
      <plugin>
        <artifactId>maven-compiler-plugin</artifactId>
        <version>3.6.1</version>
        <configuration>
          <source>1.8</source>
          <target>1.8</target>
        </configuration>
      </plugin>
      <plugin>
        <artifactId>maven-assembly-plugin</artifactId>
        <configuration>
          <descriptorRefs>
            <descriptorRef>jar-with-dependencies</descriptorRef>
          </descriptorRefs>
        </configuration>
        <executions>
          <execution>
            <id>make-assembly</id>
            <phase>package</phase>
            <goals>
              <goal>single</goal>
            </goals>
          </execution>
        </executions>
      </plugin>
    </plugins>
  </build>

</project>

二、执行结果