MapReduce编程实例之自定义排序

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任务描述：

给出一组数据，自定义排序的样式，第一列降序，相同时第二列升序

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 stubJob job = new Job();job.setJarByClass(zidingyiSort.class);// 1FileInputFormat.setInputPaths(job, new Path(args[0]));// 2job.setMapperClass(Map.class);job.setMapOutputKeyClass(MyK2.class);job.setMapOutputValueClass(LongWritable.class);// 3// 4// 5job.setNumReduceTasks(1);// 6job.setReducerClass(Reduce.class);job.setOutputKeyClass(LongWritable.class);job.setOutputValueClass(LongWritable.class);// 7FileOutputFormat.setOutputPath(job, new Path(args[1]));// 8System.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;}@Overridepublic void readFields(DataInput in) throws IOException {// TODO Auto-generated method stubthis.myk2 = in.readLong();this.myv2 = in.readLong();}@Overridepublic void write(DataOutput out) throws IOException {// TODO Auto-generated method stubout.writeLong(myk2);out.writeLong(myv2);}@Overridepublic 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

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