MapReduce高级案例⑨

辅助排序和二次排序案例（GroupingComparator）

[infobox title=”案例”]
现在需要求出每一个订单中最贵的商品。
[collapse title=”数据 GroupingComparator.txt”]

0000001	Pdt_01	222.8
0000001	Pdt_05	722.4
0000002	Pdt_05	25.8
0000002	Pdt_01	222.8
0000002	Pdt_01	33.8
0000003	Pdt_03	522.8
0000003	Pdt_04	122.4

[/collapse]
[collapse title=”输出数据预期”]

3    222.8
2    722.4
1    222.8

[/collapse]
[/infobox]
[infobox title=”code”]
[collapse title=”ruaDriver”]

package com.kami.demo01;

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

import java.io.IOException;

/**
 * @version v 1.0
 * @Author kamisamak
 * @Date 2020/6/17
 */
public class ruaDriver {
    public static void main(String[] args) throws Exception, IOException {
        args = new String[]{"data\\d01\\GroupingComparator.txt","output\\d01"};
        Configuration conf = new Configuration();
        Job job = Job.getInstance(conf);

        job.setJarByClass(ruaDriver.class);
//        job.setNumReduceTasks(3);

        job.setGroupingComparatorClass(ruaGroupingComparator.class);
        job.setPartitionerClass(ruaPartitioner.class);

        job.setMapperClass(ruaMapper.class);
        job.setReducerClass(ruaReducer.class);

        job.setMapOutputKeyClass(OrderBean.class);
        job.setMapOutputValueClass(NullWritable.class);
        job.setOutputKeyClass(OrderBean.class);
        job.setOutputValueClass(NullWritable.class);

        FileInputFormat.setInputPaths(job, new Path(args[0]));
        FileOutputFormat.setOutputPath(job, new Path(args[1]));

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

[/collapse]
[collapse title=”OrderBean”]

package com.kami.demo01;

import org.apache.hadoop.io.WritableComparable;

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

/**
 * @version v 1.0
 * @Author kamisamak
 * @Date 2020/6/17
 */

public class OrderBean implements WritableComparable {
    // 订单id号
    private int order_id;
    // 价格
    private double price;

    public OrderBean() {
        super();
    }

    public OrderBean(int order_id, double price) {
        super();
        this.order_id = order_id;
        this.price = price;
    }

    @Override
    public void write(DataOutput out) throws IOException {
        out.writeInt(order_id);
        out.writeDouble(price);
    }

    @Override
    public void readFields(DataInput in) throws IOException {
        order_id = in.readInt();
        price = in.readDouble();
    }

    @Override
    public String toString() {
        return order_id + "\t" + price;
    }

    public int getOrder_id() {
        return order_id;
    }

    public void setOrder_id(int order_id) {
        this.order_id = order_id;
    }

    public double getPrice() {
        return price;
    }

    public void setPrice(double price) {
        this.price = price;
    }

    // 二次排序
    @Override
    public int compareTo(OrderBean o) {
        int result = order_id > o.getOrder_id() ? 1 : -1;
        if (order_id > o.getOrder_id()) {
            result = 1;
        } else if (order_id < o.getOrder_id()) {
            result = -1;
        } else {
            // 价格倒序排序
            result = price > o.getPrice() ? -1 : 1;
        }
        return result;
    }
}

[/collapse]
[collapse title=”ruaGroupingComparator”]

package com.kami.demo01;

import org.apache.hadoop.io.WritableComparable;
import org.apache.hadoop.io.WritableComparator;

/**
 * @version v 1.0
 * @Author kamisamak
 * @Date 2020/6/17
 */
public class ruaGroupingComparator extends WritableComparator {

    protected ruaGroupingComparator() {
        super(OrderBean.class, true);
    }

    @SuppressWarnings("rawtypes")
    @Override
    public int compare(WritableComparable a, WritableComparable b) {
        OrderBean aBean = (OrderBean) a;
        OrderBean bBean = (OrderBean) b;
        int result;
        if (aBean.getOrder_id() > bBean.getOrder_id()) {
            result = 1;
        } else if (aBean.getOrder_id() < bBean.getOrder_id()) {
            result = -1;
        } else {
            result = 0;
        }
        return result;
    }
}

[/collapse]
[collapse title="ruaMapper"]

package com.kami.demo01;

import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;

import java.io.IOException;

/**
 * @version v 1.0
 * @Author kamisamak
 * @Date 2020/6/17
 */
public class ruaMapper extends Mapper {

    OrderBean k = new OrderBean();

    @Override
    protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
        String[] fields = value.toString().split("\t");
        k.setOrder_id(Integer.parseInt(fields[0]));
        k.setPrice(Double.parseDouble(fields[2]));
        context.write(k, NullWritable.get());
    }
}

[/collapse]
[collapse title="ruaPartitioner"]

package com.kami.demo01;

import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.mapreduce.Partitioner;

/**
 * @version v 1.0
 * @Author kamisamak
 * @Date 2020/6/17
 */
public class ruaPartitioner extends Partitioner {
    @Override
    public int getPartition(OrderBean key, NullWritable value, int numReduceTasks) {
        return (key.getOrder_id() & Integer.MAX_VALUE) % numReduceTasks;
    }
}

[/collapse]
[collapse title="ruaReducer"]

package com.kami.demo01;

import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.mapreduce.Reducer;

import java.io.IOException;

/**
 * @version v 1.0
 * @Author kamisamak
 * @Date 2020/6/17
 */
public class ruaReducer extends Reducer {
    @Override
    protected void reduce(OrderBean key, Iterable values, Context context) throws IOException, InterruptedException {
        context.write(key, NullWritable.get());
    }
}

[/collapse]
[/infobox]