MapReduce程式設計例項之自定義排序

任務描述：

給出一組資料，自定義排序的樣式，第一列降序，相同時第二列升序

example Data：

2013 1
2013 5
2014 5
2014 8
2015 9
2015 4

Code:

package mrTest;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;

import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.WritableComparable;
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;

public class zidingyiSort {

	public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {
		// TODO Auto-generated method stub

		Job job = new Job();
		job.setJarByClass(zidingyiSort.class);
		// 1
		FileInputFormat.setInputPaths(job, new Path(args[0]));
		// 2
		job.setMapperClass(Map.class);
		job.setMapOutputKeyClass(MyK2.class);
		job.setMapOutputValueClass(LongWritable.class);
		// 3
		// 4
		// 5
		job.setNumReduceTasks(1);
		// 6
		job.setReducerClass(Reduce.class);
		job.setOutputKeyClass(LongWritable.class);
		job.setOutputValueClass(LongWritable.class);
		// 7
		FileOutputFormat.setOutputPath(job, new Path(args[1]));
		// 8
		System.exit(job.waitForCompletion(true)? 0 :1 );
	}
public static class Map extends Mapper<Object, Text, MyK2, LongWritable>{
	public void map(Object key, Text value, Context context) throws IOException, InterruptedException{
		String line = value.toString();
		String[] split = line.split("\t");
		MyK2 my = new MyK2(Long.parseLong(split[0]), Long.parseLong(split[1]));
		context.write(my, new LongWritable(1));
	}
} 
public static class Reduce extends Reducer<MyK2, LongWritable, LongWritable, LongWritable>{
	public void reduce(MyK2 key, Iterable<LongWritable> values, Context context) throws IOException, InterruptedException{
		context.write(new LongWritable(key.myk2), new LongWritable(key.myv2));
	}
} 

public static class MyK2 implements WritableComparable<MyK2>{

	public long myk2;
	public long myv2;
	
	MyK2(){}
	
	MyK2(long myk2, long myv2){
		this.myk2 = myk2;
		this.myv2 = myv2;
	}
	
	@Override
	public void readFields(DataInput in) throws IOException {
		// TODO Auto-generated method stub
		this.myk2 = in.readLong();
		this.myv2 = in.readLong();
	}

	@Override
	public void write(DataOutput out) throws IOException {
		// TODO Auto-generated method stub
		out.writeLong(myk2);
		out.writeLong(myv2);
	}
	
	@Override
	public int compareTo(MyK2  myk2) {
		// TODO Auto-generated method stub
		//myk2之差>0 返回-1          <0 返回1 代表 myk2列降序
		//myk2之差<0 返回-1           >0 返回1 代表 myk2列升序
		long temp = this.myk2 - myk2.myk2;
		if(temp>0)
			return -1;
		else if(temp<0)
			return 1;
		//控制myv2升序
		return (int)(this.myv2 - myk2.myv2);
	}
}
}

效果展示：

2015 4
2015 9
2014 5
2014 8
2013 1
2013 5