Hadoop MultipleOutputs輸出到多個文件中的實現(xiàn)方法
1.輸出到多個文件或多個文件夾：
驅(qū)動中不需要額外改變，只需要在MapClass或Reduce類中加入如下代碼
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private MultipleOutputs<Text,IntWritable> mos;public void setup(Context context) throws IOException,InterruptedException { mos = new MultipleOutputs(context);}public void cleanup(Context context) throws IOException,InterruptedException { mos.close();} |
然后就可以用mos.write(Key key,Value value,String baseOutputPath)代替context.write(key, value);
在MapClass或Reduce中使用，輸出時也會有默認(rèn)的文件part-m-00*或part-r-00*，不過這些文件是無內(nèi)容的，大小為0. 而且只有part-m-00*會傳給Reduce。
注意：multipleOutputs.write(key, value, baseOutputPath)方法的第三個函數(shù)表明了該輸出所在的目錄（相對于用戶指定的輸出目錄）。
如果baseOutputPath不包含文件分隔符“/”，那么輸出的文件格式為baseOutputPath-r-nnnnn（name-r-nnnnn)；
如果包含文件分隔符“/”，例如baseOutputPath=“029070-99999/1901/part”，那么輸出文件則為029070-99999/1901/part-r-nnnnn
2.案例-需求
需求，下面是有些測試數(shù)據(jù)，要對這些數(shù)據(jù)按類目輸出到output中：
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1512,iphone5s,4英寸,指紋識別,A7處理器,64位,M7協(xié)處理器,低功耗1512,iphone5,4英寸,A6處理器,IOS71512,iphone4s,3.5英寸,A5處理器,雙核,經(jīng)典50019780,ipad,9.7英寸,retina屏幕,豐富的應(yīng)用50019780,yoga,聯(lián)想,待機18小時,外形獨特50019780,nexus 7,華碩&google,7英寸50019780,ipad mini 2,retina顯示屏,蘋果,7.9英寸1101,macbook air,蘋果超薄,OS X mavericks1101,macbook pro,蘋果,OS X lion1101,thinkpad yoga,聯(lián)想,windows 8,超級本 |
3.Mapper程序：
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package cn.edu.bjut.multioutput;import java.io.IOException;import org.apache.hadoop.io.IntWritable;import org.apache.hadoop.io.LongWritable;import org.apache.hadoop.io.Text;import org.apache.hadoop.mapreduce.Mapper;public class MultiOutPutMapper extends Mapper<LongWritable, Text, IntWritable, Text> { @Override protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException { String line = value.toString().trim(); if(null != line && 0 != line.length()) { String[] arr = line.split(","); context.write(new IntWritable(Integer.parseInt(arr[0])), value); } }} |
4.Reducer程序：
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package cn.edu.bjut.multioutput;import java.io.IOException;import org.apache.hadoop.io.IntWritable;import org.apache.hadoop.io.NullWritable;import org.apache.hadoop.io.Text;import org.apache.hadoop.mapreduce.Reducer;import org.apache.hadoop.mapreduce.lib.output.MultipleOutputs;public class MultiOutPutReducer extends Reducer<IntWritable, Text, NullWritable, Text> { private MultipleOutputs<NullWritable, Text> multipleOutputs = null; @Override protected void reduce(IntWritable key, Iterable<Text> values, Context context) throws IOException, InterruptedException { for(Text text : values) { multipleOutputs.write("KeySpilt", NullWritable.get(), text, key.toString()+"/"); multipleOutputs.write("AllPart", NullWritable.get(), text); } } @Override protected void setup(Context context) throws IOException, InterruptedException { multipleOutputs = new MultipleOutputs<NullWritable, Text>(context); } @Override protected void cleanup(Context context) throws IOException, InterruptedException { if(null != multipleOutputs) { multipleOutputs.close(); multipleOutputs = null; } }} |
5.主程序：
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package cn.edu.bjut.multioutput;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.NullWritable;import org.apache.hadoop.io.Text;import org.apache.hadoop.mapreduce.Job;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;public class MainJob { public static void main(String[] args) throws Exception { Configuration conf = new Configuration(); Job job = new Job(conf, "aaa"); job.setJarByClass(MainJob.class); job.setMapperClass(MultiOutPutMapper.class); job.setMapOutputKeyClass(IntWritable.class); job.setMapOutputValueClass(Text.class); job.setReducerClass(MultiOutPutReducer.class); job.setOutputKeyClass(NullWritable.class); job.setOutputValueClass(Text.class); FileInputFormat.addInputPath(job, new Path(args[0])); MultipleOutputs.addNamedOutput(job, "KeySpilt", TextOutputFormat.class, NullWritable.class, Text.class); MultipleOutputs.addNamedOutput(job, "AllPart", TextOutputFormat.class, NullWritable.class, Text.class); Path outPath = new Path(args[1]); FileSystem fs = FileSystem.get(conf); if(fs.exists(outPath)) { fs.delete(outPath, true); } FileOutputFormat.setOutputPath(job, outPath); job.waitForCompletion(true); }} |
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原文鏈接：http://blog.csdn.net/zhyooo123/article/details/77866458
