Hadoop MapReduce多表關聯查詢

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.InputSplit;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.input.FileSplit;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

public class one {
    static {
        System.setProperty("hadoop.home.dir","D:\\hadoop\\hadoop-2.9.2");
    }
    public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {
        Configuration conf = new Configuration();
        Job job = Job.getInstance(conf, "one");
        //擷取輸入
        FileInputFormat.addInputPaths(job,args[0]);
        //mapper計算
        job.setMapperClass(MyMapper.class);
        //shuffle計算
        //reduce計算
        job.setReducerClass(MyReduce.class);
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(Text.class);
        //擷取輸出
        FileOutputFormat.setOutputPath(job,new Path(args[1]));
        //送出
        boolean b = job.waitForCompletion(true);
        System.out.println(b?1:0);
    }
    public static class MyMapper extends Mapper<LongWritable,Text,Text,Text>{
        @Override
        protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
            String fileName = ((FileSplit) context.getInputSplit()).getPath().getName();
            String line = value.toString();
            String[] lineArr = line.split(",");
            if ("order.txt".equals(fileName)){
                context.write(new Text(lineArr[1]),new Text("1,"+lineArr[0]));
            }else {
                context.write(new Text(lineArr[0]),new Text("2,"+lineArr[1]+","+lineArr[2]+","+lineArr[3]));
            }
        }
    }
    public static class MyReduce extends Reducer<Text,Text,Text,Text> {
        @Override
        protected void reduce(Text key, Iterable<Text> values, Context context) throws IOException, InterruptedException {
            List<String> orderDetailList = new ArrayList<>();
            List<String> itemInfoList = new ArrayList<>();
            for (Text value:values){
                String valueStr = value.toString();
                String[] valueArr = valueStr.split(",");
                if ("1".equals(valueArr[0])){
                    orderDetailList.add(valueArr[1]);
                }else{
                    itemInfoList.add(valueStr.substring(2));
                }
            }
            for (String iteminfo:itemInfoList){
                for (String orderDetail:orderDetailList){
                    context.write(new Text(orderDetail+","+key+","+iteminfo),new Text(""));
                }
            }
        }
    }
}