mapreduce基础: 手写本地wordcount案例

Dear 丶 2023-09-26 21:48 45阅读 0赞

### 文章目录 ###

*   *  一、源代码
     *   *  1. WordCountMapper类
         *  2. WordCountReducer类
         *  3. WordCountDriver类
     *  二、运行截图

## 一、源代码 ##

### 1. WordCountMapper类 ###

package org.example.wordcount;
    
    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 java.io.IOException;
    
    public class WordCountMapper extends Mapper<LongWritable, Text,Text, IntWritable> {
        
    
        //新建输出文本对象(输出的key类型)
        private Text text = new Text();
        //新建输出IntWritable对象(输出的value类型)
        private IntWritable intWritable = new IntWritable( 1);
    
    
        /**
         * 重写map方法
         * @param key 文本的索引
         * @param value 文本值
         * @param context 上下文对象
         * @throws IOException
         * @throws InterruptedException
         */
        @Override
        protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
        
    
            //获取拆分后的一行文本
    
            //mysql mysql value value value
            String line = value.toString();
    
            //根据分隔符进行单词拆分
            String[] words = line.split( " ");
    
            //循环创建键值对
            for (String word : words){
        
    
                //输出key值设置
                text.set (word) ;
    
                //进行map输出
                //igeek igeek -> <igeek ,1> <igeek,1>
                context.write(text,intWritable);
            }
    
        }
    }

### 2. WordCountReducer类 ###

package org.example.wordcount;
    
    import org.apache.hadoop.io.IntWritable;
    import org.apache.hadoop.io.Text;
    import org.apache.hadoop.mapreduce.Reducer;
    
    import java.io.IOException;
    
    public class WordCountReducer extends Reducer<Text, IntWritable,Text, IntWritable> {
        
    
        //输出value对象
        private IntWritable valueOut = new IntWritable();
    
    
        /**
         * 重写reduce方法
         * @param key 单词值
         * @param values 单词出现的次数集合
         * @param context   上下文对象
         * @throws IOException
         * @throws InterruptedException
         */
        @Override
        protected void reduce(Text key, Iterable<IntWritable> values, Context context) throws IOException, InterruptedException {
        
    
            //每个单词出现的次数
            int sum= 0;
    
            //<igeek,(1,1)>
            for (IntWritable value : values){
        
    
            //累计单词出现的数量
                sum += value.get();
            }
    
            //进行封装
            valueOut.set(sum);
    
            // reduce输出
            context.write(key, valueOut);
    
    
        }
    }

### 3. WordCountDriver类 ###

package org.example.wordcount;
    
    import org.apache.hadoop.conf.Configuration;
    import org.apache.hadoop.fs.Path;
    import org.apache.hadoop.io.IntWritable;
    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.wordcounttemplate.WordCountMapper;
    import org.example.wordcounttemplate.WordCountReducer;
    
    import java.io.IOException;
    
    /**
     * 充当mapreduce任务的客户端，用于提交任务
     */
    
    public class WordCountDriver {
        
        public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {
        
    //        1.获取配置信息，获取job对象实例
            Configuration conf=new Configuration();
            Job job=Job.getInstance(conf);
    
    //        2.关联本Driver得jar路径
            job.setJarByClass(WordCountDriver.class);
    
    //        3.关联map和reduce
            job.setMapperClass(WordCountMapper.class);
            job.setReducerClass(WordCountReducer.class);
    
    //        4.设置map得输出kv类型
            job.setMapOutputKeyClass(Text.class);
            job.setMapOutputValueClass(IntWritable.class);
    
    //        5.设置最终输出得kv类型
            job.setOutputKeyClass(Text.class);
            job.setOutputValueClass(IntWritable.class);
    
    //        6.设置输入和输出路径
    //        setInputPaths:可传多个输入文件
    //         FileInputFormat.setInputPaths(job,new Path(args[0]));
    //         FileOutputFormat.setOutputPath(job,new Path(args[1]));
            
            Path inputPath = new Path("D:\\Documentation\\Hello.txt");
            FileInputFormat.setInputPaths(job,inputPath);
    
            Path outputPath = new Path("D:\\Documentation\\outHello");
            FileOutputFormat.setOutputPath(job,outputPath);
    
    //        7.提交job任务
            boolean result=job.waitForCompletion(true);
            System.out.println(result?"任务提交成功":"任务提交失败");
    
        }
    
    }

1.  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>
      
      <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>
        
        <dependency>
          <groupId>org.apache.hadoop</groupId>
          <artifactId>hadoop-client</artifactId>
          <version>3.1.3</version>
        </dependency>
    
      </dependencies>
    
      <build>
        <pluginManagement>
          <plugins>
            
            <plugin>
              <artifactId>maven-clean-plugin</artifactId>
              <version>3.1.0</version>
            </plugin>
            
            <plugin>
              <artifactId>maven-resources-plugin</artifactId>
              <version>3.0.2</version>
            </plugin>
            <plugin>
              <artifactId>maven-compiler-plugin</artifactId>
              <version>3.8.0</version>
            </plugin>
            <plugin>
              <artifactId>maven-surefire-plugin</artifactId>
              <version>2.22.1</version>
            </plugin>
            <plugin>
              <artifactId>maven-jar-plugin</artifactId>
              <version>3.0.2</version>
            </plugin>
            <plugin>
              <artifactId>maven-install-plugin</artifactId>
              <version>2.5.2</version>
            </plugin>
            <plugin>
              <artifactId>maven-deploy-plugin</artifactId>
              <version>2.8.2</version>
            </plugin>
            
            <plugin>
              <artifactId>maven-site-plugin</artifactId>
              <version>3.7.1</version>
            </plugin>
            <plugin>
              <artifactId>maven-project-info-reports-plugin</artifactId>
              <version>3.0.0</version>
            </plugin>
          </plugins>
        </pluginManagement>
      </build>
    </project>

1.  Hello.txt 测试文档

> mysql mysql value value value  
> igeek igeek  
> mysql hive port property  
> mysql value value value property  
> mysql value port property  
> mysql hive port property  
> mysql value hive hive hive property  
> mysql hive port property  
> mysql port property  
> mysql value hive hive port property  
> value property  
> value hive

![在这里插入图片描述][19614ebfe5a6432e9e9ba5694e6a75af.png]

## 二、运行截图 ##

![在这里插入图片描述][8a7dd37ece524244bc996189808a47e1.png]  
![在这里插入图片描述][369f76cc5061481c9eb208a148f09769.png]

![在这里插入图片描述][ed8bfaaf758d460881ab1884adb3f7cb.png]

![在这里插入图片描述][0fa74b231c674880b9d4246993fb8f14.png]

对照文章：  
大数据作业4（含大数据hdfs上实现wordcount案例）  
[https://blog.csdn.net/m0\_48170265/article/details/130029532?spm=1001.2014.3001.5501][https_blog.csdn.net_m0_48170265_article_details_130029532_spm_1001.2014.3001.5501]

[19614ebfe5a6432e9e9ba5694e6a75af.png]: https://img-blog.csdnimg.cn/19614ebfe5a6432e9e9ba5694e6a75af.png
[8a7dd37ece524244bc996189808a47e1.png]: https://img-blog.csdnimg.cn/8a7dd37ece524244bc996189808a47e1.png
[369f76cc5061481c9eb208a148f09769.png]: https://img-blog.csdnimg.cn/369f76cc5061481c9eb208a148f09769.png
[ed8bfaaf758d460881ab1884adb3f7cb.png]: https://img-blog.csdnimg.cn/ed8bfaaf758d460881ab1884adb3f7cb.png
[0fa74b231c674880b9d4246993fb8f14.png]: https://img-blog.csdnimg.cn/0fa74b231c674880b9d4246993fb8f14.png
[https_blog.csdn.net_m0_48170265_article_details_130029532_spm_1001.2014.3001.5501]: https://blog.csdn.net/m0_48170265/article/details/130029532?spm=1001.2014.3001.5501