hadoop1.2.1 MultipleOutputs将结果输出到多个文件或文件夹

hadoop1.2.1中使用MultipleOutputs将结果输出到多个文件或文件夹

使用步骤主要有三步：

1、在reduce或map类中创建MultipleOutputs对象，将结果输出

class reduceStatistics extends Reducer<Text, IntWritable, Text, IntWritable>{

	//将结果输出到多个文件或多个文件夹
	private MultipleOutputs<Text,IntWritable> mos;
    //创建对象
    protected void setup(Context context) throws IOException,InterruptedException {
        mos = new MultipleOutputs<Text, IntWritable>(context);
     }
    	
        //关闭对象
	protected void cleanup(Context context) throws IOException,InterruptedException {
        mos.close();
	}
}

 2、在map或reduce方法中使用MultipleOutputs对象输出数据，代替congtext.write()

protected void reduce(Text key, Iterable<IntWritable> values, Context context)
			throws IOException, InterruptedException {
		IntWritable V = new IntWritable();
		int sum = 0;
		for(IntWritable value : values){
			sum = sum + value.get();
		}
		System.out.println("word:" + key.toString() + "     sum = " + sum);
		V.set(sum);

		//使用MultipleOutputs对象输出数据
		if(key.toString().equals("hello")){
			mos.write("hello", key, V);
		}else if(key.toString().equals("world")){
			mos.write("world", key, V);
		}else if(key.toString().equals("hadoop")){
			//输出到hadoop/hadoopfile-r-00000文件
			mos.write("hadoopfile", key, V, "hadoop/");
		}
		
	}

 3、在创建job时，定义附加的输出文件，这里的文件名称与第二步设置的文件名相同

//定义附加的输出文件
			MultipleOutputs.addNamedOutput(job,"hello",TextOutputFormat.class,Text.class,IntWritable.class);
			MultipleOutputs.addNamedOutput(job,"world",TextOutputFormat.class,Text.class,IntWritable.class);
			MultipleOutputs.addNamedOutput(job,"hadoopfile",TextOutputFormat.class,Text.class,IntWritable.class);

完整代码：

package com.ru.hadoop.wordcount;

import java.io.IOException;
import java.net.URI;
import java.net.URISyntaxException;
import java.util.regex.Pattern;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;
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.NullWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.RecordWriter;
import org.apache.hadoop.mapred.lib.MultipleOutputFormat;
import org.apache.hadoop.mapred.lib.MultipleTextOutputFormat;
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;
import org.apache.hadoop.mapreduce.lib.output.MultipleOutputs;
import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;
import org.apache.hadoop.util.Progressable;

public class WordCount2 extends Configured{

	public static void main(String[] args) {
		String in = "/home/nange/work/test/word/";
		String out = "hdfs://localhost:9000/hdfs/test/wordcount/out/";
		
		Job job;
		try {
			//删除hdfs目录
			WordCount2 wc2 = new WordCount2();
			wc2.removeDir(out);
			
			job = new Job(new Configuration(), "wordcount Job");
			job.setOutputKeyClass(Text.class);
			job.setOutputValueClass(IntWritable.class);
			job.setMapperClass(mapperString.class);
//			job.setCombinerClass(reduceStatistics.class);
			job.setReducerClass(reduceStatistics.class);
			
			//定义附加的输出文件
			MultipleOutputs.addNamedOutput(job,"hello",TextOutputFormat.class,Text.class,IntWritable.class);
			MultipleOutputs.addNamedOutput(job,"world",TextOutputFormat.class,Text.class,IntWritable.class);
			MultipleOutputs.addNamedOutput(job,"hadoopfile",TextOutputFormat.class,Text.class,IntWritable.class);
			
			FileInputFormat.addInputPath(job, new Path(in));
			FileOutputFormat.setOutputPath(job, new Path(out));
			job.waitForCompletion(true);
		} catch (IOException e) {
			e.printStackTrace();
		} catch (URISyntaxException e) {
			e.printStackTrace();
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
	}
	
	public void removeDir(String filePath) throws IOException, URISyntaxException{
		String url = "hdfs://localhost:9000";
		FileSystem fs  = FileSystem.get(new URI(url), new Configuration());
		fs.delete(new Path(filePath));
	}
}


/**
 * 重写maptask使用的map方法 
 * @author nange
 *
 */
class mapperString extends Mapper<LongWritable, Text, Text, IntWritable>{
	//设置正则表达式的编译表达形式
	public static Pattern PATTERN = Pattern.compile(" ");
	Text K = new Text();
	IntWritable V = new IntWritable(1);
	@Override
	protected void map(LongWritable key, Text value, Context context)
			throws IOException, InterruptedException {
		
		String[] words = PATTERN.split(value.toString());
		System.out.println("********" + value.toString());
		for(String word : words){
			K.set(word);
			context.write(K, V);
		}
	}
}

/**
 * 对单词做统计
 * @author nange
 *
 */
class reduceStatistics extends Reducer<Text, IntWritable, Text, IntWritable>{

	//将结果输出到多个文件或多个文件夹
	private MultipleOutputs<Text,IntWritable> mos;
	//创建MultipleOutputs对象
    protected void setup(Context context) throws IOException,InterruptedException {
        mos = new MultipleOutputs<Text, IntWritable>(context);
     }
    
	@Override
	protected void reduce(Text key, Iterable<IntWritable> values, Context context)
			throws IOException, InterruptedException {
		IntWritable V = new IntWritable();
		int sum = 0;
		for(IntWritable value : values){
			sum = sum + value.get();
		}
		System.out.println("word:" + key.toString() + "     sum = " + sum);
		V.set(sum);

		//使用MultipleOutputs对象输出数据
		if(key.toString().equals("hello")){
			mos.write("hello", key, V);
		}else if(key.toString().equals("world")){
			mos.write("world", key, V);
		}else if(key.toString().equals("hadoop")){
			//输出到hadoop/hadoopfile-r-00000文件
			mos.write("hadoopfile", key, V, "hadoop/");
		}
		
	}
	
	//关闭MultipleOutputs对象
	protected void cleanup(Context context) throws IOException,InterruptedException {
        mos.close();
	}
}