MR-join连接

package com.bw.mr;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.HashMap;
import java.util.Map;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;

public class MapJoin {
    // 两个文件都在内存中 一个机器的内存中
    // 通过集合放入一个机器的内存中
    // 通过map任务放入内存中
    // join连接共有的属性连接
    public static class JMapper extends Mapper<LongWritable, Text, Text, NullWritable> {
        // 将user放入内存中
        private Map<String, String> map = new HashMap<String, String>();

        // 重新setup方法 运行在map前面
        @Override
        protected void setup(Mapper<LongWritable, Text, Text, NullWritable>.Context context)
                throws IOException, InterruptedException {
            // 创建连接
            FileSystem fs = FileSystem.get(context.getConfiguration());
            // user01.txt hdfs 拉取信息 到内存map
            FSDataInputStream in = fs.open(new Path("hdfs://linux04:9000/user.txt"));
            // 读取 BufferedReader 读取器
            BufferedReader bf = new BufferedReader(new InputStreamReader(in));
            // 一行一行读取
            String line = null;
            while ((line = bf.readLine()) != null) {
                String[] split = line.split(" ");
                map.put(split[], split[] + " " + split[] + " " + split[]);
            }
            bf.close();
            in.close();
        }
        @Override
        protected void map(LongWritable key, Text value, Mapper<LongWritable, Text, Text, NullWritable>.Context context)
                throws IOException, InterruptedException {
            String[] strs = value.toString().split(" ");
            String orderId = strs[];
            String uid = strs[];
            String money = strs[];
            //join 的uid 关联】
            String productInfo = map.get(uid);
            context.write(new Text(orderId+" "+uid+" "+productInfo), NullWritable.get());
        }
    }
    public static void main(String[] args) throws Exception {
        Configuration conf =new  Configuration();
        Job job = Job.getInstance(conf);
        job.setJarByClass(MapJoin.class);
        job.setMapperClass(JMapper.class);
        job.setMapOutputKeyClass(Text.class);
        job.setMapOutputValueClass(NullWritable.class);
        job.setNumReduceTasks();
        FileInputFormat.addInputPath(job,new Path(args[]));
        FileOutputFormat.setOutputPath(job, new Path(args[]));
        job.waitForCompletion(true);

    }
}