MR--案列2

最新推荐文章于 2024-10-21 19:32:28 发布

原创最新推荐文章于 2024-10-21 19:32:28 发布 · 306 阅读

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本文介绍了一个使用Hadoop实现的左连接示例程序，包括Mapper和Reducer的实现细节。通过对买家名称、接收者名称、商品及价格进行处理，演示了如何在大规模数据集上执行左连接操作。

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参考案例1的测试数据:

package com.testMr;

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

import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
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 org.apache.hadoop.mapreduce.lib.partition.HashPartitioner;

public class LeftJoinDemo {

	public static class LeftJoinMap extends Mapper<LongWritable, Text, Text, Text> {
		@Override
		protected void map(LongWritable key, Text value, Mapper<LongWritable, Text, Text, Text>.Context context)
				throws IOException, InterruptedException {
			String[] line = value.toString().split(" ");
			String buyerName = line[0];
			String receiverName = line[1];
			String goods = line[2];
			String price = line[3];
			context.write(new Text(buyerName), new Text(buyerName + " " + receiverName + " " + goods + " " + price));

		}
	}

	public static class LeftJoinReduce extends Reducer<Text, Text, Text, Text> {

		@Override
		protected void reduce(Text arg0, Iterable<Text> arg1, Reducer<Text, Text, Text, Text>.Context arg2)
				throws IOException, InterruptedException {

			Iterator it = arg1.iterator();
			String[] arr;
			int max = Integer.MIN_VALUE;
			String maxGoodsName = "";
			while (it.hasNext()) {
				String line = it.next().toString();
				arr = line.split(" ");

				if (arr.length != 4) {
					throw new RuntimeException("数组个数不是4个，这行的数据为" + line.toString() + ", 大小为：" + arr.length);
				}

				if (Integer.parseInt(arr[3]) > max) {
					max = Integer.parseInt(arr[3]);
					maxGoodsName = arr[2];
				}
			}
			String m = Integer.toString(max);
			arg2.write(new Text(arg0), new Text(m + " " + maxGoodsName));
		}

	}

	public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {
		System.out.println(args.length);
		for (String str : args) {
			System.out.println(str);
		}
		String input1 = args[0];
		// String input2 = args[1];
		String outputPath = args[1];

		Job job = Job.getInstance();

		job.setJobName("test");
		job.setJarByClass(LeftJoinDemo.class);

		FileInputFormat.addInputPath(job, new Path(input1));
		// FileInputFormat.addInputPath(job, new Path(input2));
		FileOutputFormat.setOutputPath(job, new Path(outputPath));

		job.setMapperClass(LeftJoinMap.class);
		job.setReducerClass(LeftJoinReduce.class);
		job.setPartitionerClass(HashPartitioner.class);
		job.setNumReduceTasks(1);

		job.setOutputValueClass(Text.class);
		job.setOutputKeyClass(Text.class);

		System.exit(job.waitForCompletion(true) ? 0 : 1);
	}

}