MapReduce

package com.hongyaa.mr.mobile.member;

import java.io.IOException;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
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.output.FileOutputFormat;

public class MemberLevelCount {

public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {
	// （1）创建配置文件对象
	Configuration conf = new Configuration();
	conf.set("fs.defaultFS", "hdfs://localhost:9000");

	// （2）新建一个 job 任务
	Job job = Job.getInstance(conf);

	// （3）将 job 所用到的那些类（class）文件，打成jar包 （打成jar包在集群运行必须写）
	job.setJarByClass(MemberLevelCount.class);

	// （4）指定 mapper 类和 reducer 类
	job.setMapperClass(MemberLevelCountMapper.class);
	job.setReducerClass(MemberLevelCountReducer.class);

	// （5）指定 ReduceTask 的输出key-value类型
	job.setOutputKeyClass(Text.class);
	job.setOutputValueClass(IntWritable.class);

	// （6）指定该 mapreduce 程序数据的输入和输出路径
	Path inPath = new Path("/mobile/input");
	Path outPath = new Path("/mobile/member_level");

	// 获取 fs 对象
	FileSystem fs = FileSystem.get(conf);
	if (fs.exists(outPath)) {
		fs.delete(outPath, true);
	}
	FileInputFormat.setInputPaths(job, inPath);
	FileOutputFormat.setOutputPath(job, outPath);

	// （7）最后给YARN来运行，等着集群运行完成返回反馈信息，客户端退出
	boolean waitForCompletion = job.waitForCompletion(true);
	System.exit(waitForCompletion ? 0 : 1);
}


public static class MemberLevelCountMapper extends Mapper {
	
	@Override
	protected void map(LongWritable key, Text value, Mapper.Context context)
			throws IOException, InterruptedException {
		// （1）获取一行文本的内容
		String line = value.toString();
		// （2）根据分隔符“t”进行切分
		String[] mobile = line.split("t");
		// 会员等级
		String memberLevel = mobile[3];
		// （3）将会员等级作为key，将次数1作为value，分发给Reduce端
		context.write(new Text(memberLevel), new IntWritable(1));
	}
}


public static class MemberLevelCountReducer extends Reducer {
	@Override
	protected void reduce(Text key, Iterable values,
			Reducer.Context context)
			throws IOException, InterruptedException {
		// 做每个会员等级的结果汇总
		int sum = 0;
		// （1）遍历values
		for (IntWritable v : values) {
			// 累积求和
			sum += v.get();
		}
		// （2）将会员等级作为key，总数作为value，输出最终结果
		context.write(key, new IntWritable(sum));
	}
}

}