大数据培训Map Join

package test;

import java.net.URI;

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;

public class DistributedCacheDriver {

   public static void main(String[] args) throws Exception {

// 0 根据自己电脑路径重新配置

args = new String[]{“e:/input/inputtable2”, “e:/output1”};

// 1 获取job信息

      Configuration configuration = new Configuration();

      Job job = Job.getInstance(configuration);

      // 2 设置加载jar包路径

      job.setJarByClass(DistributedCacheDriver.class);

      // 3 关联map

      job.setMapperClass(DistributedCacheMapper.class);

// 4 设置最终输出数据类型

      job.setOutputKeyClass(Text.class);

      job.setOutputValueClass(NullWritable.class);

      // 5 设置输入输出路径

      FileInputFormat.setInputPaths(job, new Path(args[0]));

      FileOutputFormat.setOutputPath(job, new Path(args[1]));

      // 6 加载缓存数据

      job.addCacheFile(new URI(“file:///e:/input/inputcache/pd.txt”));

      // 7 Map端Join的逻辑不需要Reduce阶段，设置reduceTask数量为0

      job.setNumReduceTasks(0);

      // 8 提交

      boolean result = job.waitForCompletion(true);

      System.exit(result ? 0 : 1);

   }

}

package test;

import java.io.BufferedReader;

import java.io.FileInputStream;

import java.io.IOException;

import java.io.InputStreamReader;

import java.util.HashMap;

import java.util.Map;

import org.apache.commons.lang.StringUtils;

import org.apache.hadoop.io.LongWritable;

import org.apache.hadoop.io.NullWritable;

import org.apache.hadoop.io.Text;

import org.apache.hadoop.mapreduce.Mapper;

public class DistributedCacheMapper extends Mapper<LongWritable, Text, Text, NullWritable>{

   Map<String, String> pdMap = new HashMap<>();

   @Override

   protected void setup(Mapper<LongWritable, Text, Text, NullWritable>.Context context) throws IOException, InterruptedException {

      // 1 获取缓存的文件

      URI[] cacheFiles = context.getCacheFiles();

      String path = cacheFiles[0].getPath().toString();

      BufferedReader reader = new BufferedReader(new InputStreamReader(new FileInputStream(path), “UTF-8”));

      String line;

      while(StringUtils.isNotEmpty(line = reader.readLine())){

          // 2 切割

          String[] fields = line.split(“\t”);

          // 3 缓存数据到集合

          pdMap.put(fields[0], fields[1]);

      }

      // 4 关流

      reader.close();

   }

   Text k = new Text();

   @Override

   protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {

      // 1 获取一行

      String line = value.toString();

      // 2 截取

      String[] fields = line.split(“\t”);

      // 3 获取产品id

      String pId = fields[1];

      // 4 获取商品名称

      String pdName = pdMap.get(pId);

      // 5 拼接

      k.set(line + “\t”+ pdName);

      // 6 写出

      context.write(k, NullWritable.get());

   }

}