二次排序 3

package com.bw.mr;

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

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.NullWritable;
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.Partitioner;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;

//match  chinese  数学成绩和  语文成绩
// 98 56
// 85 65
// 72 76
// 85 98
// 72 75
// 89 80
// 98 99
// 65 99    shuffle 的key排序  
//需求  按照学生的考试成绩进行排序   1.按照数学成绩排序 2.数学成绩一致  按照语文成绩排序
//1. 默认给定了三次排序  integerw   in.......
public class SecondarySort2 {
    public static class SSMapper extends Mapper<LongWritable, Text, Score2, NullWritable> {
        @Override
        protected void map(LongWritable key, Text value,
                Mapper<LongWritable, Text, Score2, NullWritable>.Context context)
                throws IOException, InterruptedException {
            // 切分对象
            String[] strs = value.toString().split(" ");
            context.write(new Score2(Integer.parseInt(strs[0].toString()), Integer.parseInt(strs[1].toString())),
                    NullWritable.get());
        }
    }

    public static class SSReducer extends Reducer<Score2, NullWritable, Score2, NullWritable> {
        @Override
        protected void reduce(Score2 arg0, Iterable<NullWritable> arg1,
                Reducer<Score2, NullWritable, Score2, NullWritable>.Context arg2)
                throws IOException, InterruptedException {
            arg2.write(arg0, NullWritable.get());
        }
    }

    // 定义自定义分区 避免系统将 相同数据未放置在同一分分区中
    public static class MyPartitioner extends Partitioner<Score2, NullWritable> {
        @Override // 将相同的数据放在同一个分区中 match + chinese
        public int getPartition(Score2 arg0, NullWritable arg1, int numpartitions) {
            // 保证了相同数据在同一个分区
            return arg0.getMatch() % numpartitions;// 同一个成绩余数相同
        }
    }

    public static void main(String[] args) throws Exception {
        Configuration conf = new Configuration();
        Job job = Job.getInstance(conf);
        job.setPartitionerClass(MyPartitioner.class);
        job.setJarByClass(SecondarySort2.class);
        job.setMapperClass(SSMapper.class);
        job.setMapOutputKeyClass(Score2.class);
        job.setMapOutputValueClass(NullWritable.class);
        job.setReducerClass(SSReducer.class);
        job.setOutputKeyClass(Score2.class);
        job.setMapOutputValueClass(NullWritable.class);
        job.setNumReduceTasks(2);
        FileInputFormat.addInputPath(job, new Path(args[0]));
        FileOutputFormat.setOutputPath(job, new Path(args[1]));
        job.waitForCompletion(true);
    }
}

class Score2 implements WritableComparable<Score2> {
    // 定义两个成绩
    private int match;
    private int chinese;
    // 构造器 get set

    public int getMatch() {
        return match;
    }

    @Override
    public String toString() {
        return "Score2 [match=" + match + ", chinese=" + chinese + "]";
    }

    public Score2(int match, int chinese) {
        super();
        this.match = match;
        this.chinese = chinese;
    }

    public Score2() {
        super();
    }

    public void setMatch(int match) {
        this.match = match;
    }

    public int getChinese() {
        return chinese;
    }

    public void setChinese(int chinese) {
        this.chinese = chinese;
    }

    // 利用shuffle排序 对象具备序列化
    @Override
    public void readFields(DataInput in) throws IOException {
        this.match = in.readInt();
        this.chinese = in.readInt();
    }

    @Override
    public void write(DataOutput out) throws IOException {
        out.writeInt(this.match);
        out.writeInt(this.chinese);
    }

    // 重写 compareTo的方法 定义排序规则
    @Override
    public int compareTo(Score2 o) {
        // 如果数学成绩一致的话 就去比较语文成绩
        if (o.getMatch() == this.getMatch()) {
            return o.getChinese() - this.getChinese();
        } else {
            // 比较数学成绩
            return o.getMatch() - this.getMatch();
        }
    }
}