基于Mapreduce数据排序

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 {
    // map将输入中的value化成IntWritable类型，作为输出的key
    public static class Map extends
            Mapper<Object, Text, IntWritable, IntWritable> {
        private static IntWritable data = new IntWritable();

        // 实现map函数
        public void map(Object key, Text value, Context context)
                throws IOException, InterruptedException {

            String line = value.toString();

            data.set(Integer.parseInt(line));

            context.write(data, new IntWritable(1));
        }
    }

    // reduce将输入中的key复制到输出数据的key上，

    // 然后根据输入的value-list中元素的个数决定key的输出次数

    // 用全局linenum来代表key的位次

    public static class Reduce extends

    Reducer<IntWritable, IntWritable, IntWritable, IntWritable> {
        private static IntWritable linenum = new IntWritable(1);

        // 实现reduce函数
        public void reduce(IntWritable key, Iterable<IntWritable> values,
                Context context)

        throws IOException, InterruptedException {

            for (IntWritable val : values) {

                context.write(linenum, key);

                linenum = new IntWritable(linenum.get() + 1);

            }
        }
    }

    public static void main(String[] args) throws Exception {

        Configuration conf = new Configuration();
        conf.set("mapred.job.tracker", "localhost:9000");
        String[] ioArgs = new String[] { "hdfs://localhost:9000/input/sort",
                "hdfs://localhost:9000/output/sortout" };

        String[] otherArgs = new GenericOptionsParser(conf, ioArgs)
                .getRemainingArgs();

        if (otherArgs.length != 2) {

            System.err.println("Usage: Data Sort <in> <out>");

            System.exit(2);

        }
        // Job job = new Job(conf, "Data Sort");
        Job job = Job.getInstance(conf, "Data Sort");

        job.setJarByClass(Sort.class);
        // 设置Map和Reduce处理类
        job.setMapperClass(Map.class);

        job.setReducerClass(Reduce.class);
        // 设置输出类型
        job.setOutputKeyClass(IntWritable.class);

        job.setOutputValueClass(IntWritable.class);
        // 设置输入和输出目录
        FileInputFormat.addInputPath(job, new Path(otherArgs[0]));

        FileOutputFormat.setOutputPath(job, new Path(otherArgs[1]));

        System.exit(job.waitForCompletion(true) ? 0 : 1);
    }
}