hadop 역 열 색인

                    ，             。           （   ），                   ，                  ，                   ，          ，         。

   inversed.files  file1，file2，file3  ，       ：

file1：

dog cat
dog rabbit
tiger mice
goose chicken
rabbit fox

file2：

tiger donkey
lion fish
duck wolf
dog bird
cat bear

file3：

snake pig
lion
cat
elephant

         ，    ：

 
 
bear file2:1 ,
 
 
bird file2:1 ,
 
 
cat file2:1 ,file1:1 ,file3:1 ,
 
 
chicken file1:1 ,
dog 
  file1:2 ,file2:1 ,duck 
  file2:1 ,dungkey 
  file2:1 ,elephant 
  file3:1 ,fish 
  file2:1 ,fox 
  file1:1 ,goose 
  file1:1 ,lion 
  file2:1 ,file3:1 ,mice 
  file1:1 ,pig 
  file3:1 ,rabbit 
  file1:2 ,snake 
  file3:1 ,tiger 
  file2:1 ,file1:1 ,wolf 
  file2:1 , 
 
 
 
import java.io.IOException;
import java.util.StringTokenizer;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
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;

public class InversedIndex {
	
	/**
	 *        ，
	 *                 map key  ，
	 *         value  
	 * */
	
	public static class InversedIndexMapper extends Mapper<Object, Text, Text, Text> {
		
		private Text outKey = new Text();
		private Text outVal = new Text();
		
		@Override
		public void map (Object key,Text value,Context context) {
			StringTokenizer tokens = new StringTokenizer(value.toString());
			FileSplit split = (FileSplit) context.getInputSplit();
			while(tokens.hasMoreTokens()) {
				String token = tokens.nextToken();
				try {
					outKey.set(token + ":" + split.getPath());
					outVal.set("1");
					context.write(outKey, outVal);
				} catch (IOException e) {
					e.printStackTrace();
				} catch (InterruptedException e) {
					e.printStackTrace();
				}
			}
		}
	}
	
	/**
	 * map      combiner  ，                   reduce  ，
	 *     key          ，         key，
	 *          ，    value，
	 *            ，             key--value  
	 * */
	public static class InversedIndexCombiner extends Reducer<Text, Text, Text, Text> {
		
		private Text outKey = new Text();
		private Text outVal = new Text();
		
		@Override
		public void reduce(Text key,Iterable<Text> values,Context context) {
			String[] keys = key.toString().split(":");
			int sum = 0;
			for(Text val : values) {
				sum += Integer.parseInt(val.toString());
			}
			try {
				outKey.set(keys[0]);
				int index = keys[keys.length-1].lastIndexOf('/');
				outVal.set(keys[keys.length-1].substring(index+1) + ":" + sum);
				context.write(outKey, outVal);
			} catch (IOException e) {
				e.printStackTrace();
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
		}
		
	}
	
	/**
	 *  combiner  key value   reduce，
	 *   combiner  ，            value，      value      
	 * */
	
	public static class InversedIndexReducer extends Reducer<Text, Text, Text, Text> {
		
		@Override
		public void reduce (Text key,Iterable<Text> values,Context context) {
			StringBuffer sb = new StringBuffer();
			for(Text text : values) {
				sb.append(text.toString() + " ,");
			}
			try {
				context.write(key, new Text(sb.toString()));
			} catch (IOException e) {
				e.printStackTrace();
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
		}
	}
	
	public static void main(String[] args) throws IOException, InterruptedException, ClassNotFoundException {
		Configuration conf = new Configuration();
		Job job = new Job(conf,"index inversed");
		
		job.setJarByClass(InversedIndex.class);
		job.setMapperClass(InversedIndexMapper.class);
		job.setCombinerClass(InversedIndexCombiner.class);
		job.setReducerClass(InversedIndexReducer.class);
		job.setMapOutputKeyClass(Text.class);
		job.setMapOutputValueClass(Text.class);
		job.setOutputKeyClass(Text.class);
		job.setOutputValueClass(Text.class);
		
		FileInputFormat.addInputPath(job, new Path("inversed.files"));
		FileOutputFormat.setOutputPath(job, new Path("inversed.result"));
		
		System.exit(job.waitForCompletion(true)?0:1);
		
	}

}