hadoop案例：Mapjoin

分手后的思念是犯贱 2022-11-22 00:02 120阅读 0赞

### 文章目录 ###

*   *  pom.xml
     *  输入数据
     *  期望结果
     *  需求分析
     *  Mapper类
     *  Reducer类
     *  Driver类
     *  执行结果

## pom.xml ##

<groupId>com.huang</groupId>
        <artifactId>Hadoop</artifactId>
        <version>1.0-SNAPSHOT</version>
        <build>
            <plugins>
                <plugin>
                    <groupId>org.apache.maven.plugins</groupId>
                    <artifactId>maven-compiler-plugin</artifactId>
                    <configuration>
                        <source>7</source>
                        <target>7</target>
                    </configuration>
                </plugin>
            </plugins>
        </build>
        <dependencies>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-core</artifactId>
            <version>2.8.2</version>
        </dependency>
        <dependency>
            <groupId>org.apache.hadoop</groupId>
            <artifactId>hadoop-common</artifactId>
            <version>2.7.2</version>
        </dependency>
        <dependency>
            <groupId>org.apache.hadoop</groupId>
            <artifactId>hadoop-client</artifactId>
            <version>2.7.2</version>
        </dependency>
        <dependency>
            <groupId>org.apache.hadoop</groupId>
            <artifactId>hadoop-hdfs</artifactId>
            <version>2.7.2</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>RELEASE</version>
            <scope>compile</scope>
        </dependency>
    
    </dependencies>
    </project>

## 输入数据 ##

order.txt

1001	01	1
    1002	02	2
    1003	03	3
    1004	01	4
    1005	02	5
    1006	03	6

pd.txt

01	小米
    02	华为
    03	格力

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzNjc0MzYw_size_16_color_FFFFFF_t_70_pic_center]

## 期望结果 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzNjc0MzYw_size_16_color_FFFFFF_t_70_pic_center 1]

## 需求分析 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzNjc0MzYw_size_16_color_FFFFFF_t_70_pic_center 2]

## Mapper类 ##

package com.mr.mapjoin;
    
    import org.apache.commons.lang.StringUtils;
    import org.apache.hadoop.io.IOUtils;
    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.BufferedReader;
    import java.io.FileInputStream;
    import java.io.IOException;
    import java.io.InputStreamReader;
    import java.net.URI;
    import java.util.HashMap;
    
    
    public class MapJoinMapper extends Mapper<LongWritable, Text, Text, NullWritable> { 
    
    
        HashMap<String, String> pdMap = new HashMap<>();
        Text text = new Text();
    
    
        @Override
        protected void setup(Context context) throws IOException, InterruptedException { 
    // 获取到缓存文件，是一个 URI 的数组
            URI[] cacheFiles = context.getCacheFiles();
    // 由于只有一个缓存文件 pd.txt，我们这里只需要拿到第一个元素即可
            URI pdUri = cacheFiles[0];
    // 获取到缓存文件的路径
            String path = pdUri.getPath();
    
    // 获取到bufferedReader对象（缓冲字符流）
           // FileInputStream fileInputStream = new FileInputStream(path);
           // InputStreamReader inputStreamReader = new InputStreamReader(fileInputStream);
            BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(new FileInputStream(path)));
    
    // 对每行数据做迭代，进行切割，切割后的数据放入到map中
            String line;
           // String line = bufferedReader.readLine();
    // while (!(line = bufferedReader.readLine()).isEmpty()) { 
            while (StringUtils.isNotEmpty(line = bufferedReader.readLine())) { 
                String[] split = line.split("\t");
                pdMap.put(split[0], split[1]);
            }
    // 关闭资源
            IOUtils.closeStream(bufferedReader);
    
        }
    
        @Override
        protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException { 
    // 读取order.txt 的每行数据，并进行切割
            String[] split = value.toString().split("\t");
    // 获取 pid 公共字段
            String pid = split[1];
    // 根据pid从map中获取到pname
            String pname = pdMap.get(pid);
    
    // 拼接最后的结果
            text.set(split[0] + "\t" + pname + "\t" + split[2]);
            context.write(text, NullWritable.get());
    
        }
    }

## Reducer类 ##

无，这里需要，在driver里面设就行

## Driver类 ##

package com.mr.mapjoin;
    
    import org.apache.hadoop.conf.Configuration;
    import org.apache.hadoop.fs.Path;
    import org.apache.hadoop.io.NullWritable;
    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 java.io.IOException;
    import java.net.URI;
    import java.net.URISyntaxException;
    
    
    public class MapJoinDriver { 
        public static void main(String[] args) throws IOException, URISyntaxException, ClassNotFoundException, InterruptedException { 
            args = new String[]{ "E:/Hadoop/src/main/resources/input/jointest", "E:/Hadoop/src/main/resources/ouput/join"};
    
            Configuration configuration = new Configuration();
            Job job = Job.getInstance(configuration);
    
            job.setJarByClass(MapJoinDriver.class);
    
            job.setMapOutputKeyClass(Text.class);
            job.setMapOutputValueClass(NullWritable.class);
    
            job.setMapperClass(MapJoinMapper.class);
    
            job.addCacheFile(new URI("file:///E:/Hadoop/src/main/resources/input/tablenum/pd.txt"));
            job.setNumReduceTasks(0);
    
            FileInputFormat.setInputPaths(job, new Path(args[0]));
            FileOutputFormat.setOutputPath(job, new Path(args[1]));
    
            boolean b = job.waitForCompletion(true);
            System.exit(b ? 0 : 1);
    
    
    
        }
    }

## 执行结果 ##

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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzNjc0MzYw_size_16_color_FFFFFF_t_70_pic_center 2]: https://img-blog.csdnimg.cn/20201102202321219.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzNjc0MzYw,size_16,color_FFFFFF,t_70#pic_center