Hadoop-5、排序（Combiner泛谈）

import java.io.IOException;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
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;
import org.apache.hadoop.util.GenericOptionsParser;


public class Sort {
    public static class Map extends Mapper<Object,Text,IntWritable,IntWritable>{
        private static IntWritable num = new IntWritable();
        public void map(Object key,Text value,Context context) throws IOException, InterruptedException{
            String line = value.toString();
            num.set(Integer.parseInt(line));
            context.write(num, new IntWritable(1));
        }
    }
    
    public static class Reduce extends Reducer<IntWritable,IntWritable,IntWritable,IntWritable>{
        private static IntWritable count = new IntWritable(0);
        public void reduce(IntWritable key,Iterable<IntWritable> value,Context context) throws IOException, InterruptedException{
            for(IntWritable val : value){
                count = new IntWritable(count.get()+1);
                context.write(count,key);
            }
        }
    }
    
    public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException{
        Configuration conf = new Configuration();
        conf.addResource(new Path("/usr/hadoop-1.0.3/conf/core-site.xml"));
        
        String[] arg = new GenericOptionsParser(conf,args).getRemainingArgs();
        
        Job job = new Job(conf,"Sort");
        
        job.setJarByClass(Sort.class);
        
        job.setMapperClass(Map.class);
        job.setReducerClass(Reduce.class);
        
        job.setOutputKeyClass(IntWritable.class);
        job.setOutputValueClass(IntWritable.class);
        
        FileInputFormat.addInputPath(job, new Path(arg[0]));
        FileOutputFormat.setOutputPath(job, new Path(arg[1]));
        
        System.exit(job.waitForCompletion(true) ? 0 : 1);
    }
}