15.辅助排序

版权声明：1911907658 https://blog.csdn.net/qq_33598343/article/details/84454788

需求：对于不同商品号，我需要获得分区的信息，并且每个分区我只要一行信息，要求价格为最高

数据:

中间以"\t"分割

1001	Tmall_01	998
1001	Tmall_06	88.8
1001	Tmall_03	522.8
1002	Tmall_03	522.8
1002	Tmall_04	132.4
1002	Tmall_05	372.4
1003	Tmall_01	998
1003	Tmall_02	8.5
1003	Tmall_04	132.4

Mapper:

public class GoodMapper extends Mapper<LongWritable, Text, GoodsBeen, NullWritable>{

	@Override
	protected void map(LongWritable key, Text value,
			Context context)
			throws IOException, InterruptedException {
		// TODO Auto-generated method stub
		String line = value.toString();
		String[] fields = line.split("\t");
		int p_id = Integer.parseInt(fields[0]);
		String p_name = fields[1];
		Double p_price = Double.parseDouble(fields[2]);
		context.write(new GoodsBeen(p_id, p_name, p_price), NullWritable.get());
	}

GoodBeen:

public class GoodsBeen implements WritableComparable<GoodsBeen>{
	private int p_id ;
	private String p_name ;
	private Double P_price ;
	@Override
	public String toString() {
		return p_id+"\t"+p_name+"\t"+P_price;
	}
	@Override
	public void readFields(DataInput in) throws IOException {
		// TODO Auto-generated method stub
		p_id = in.readInt();
		p_name = in.readUTF();
		P_price = in.readDouble();
	}
	@Override
	public void write(DataOutput out) throws IOException {
		// TODO Auto-generated method stub
		out.writeInt(p_id);
		out.writeUTF(p_name);
		out.writeDouble(P_price);
	}
	@Override
	public int compareTo(GoodsBeen o) {
		// TODO Auto-generated method stub
		return this.P_price>o.P_price?-1:1;
	}
	public int getP_id() {
		return p_id;
	}
	public void setP_id(int p_id) {
		this.p_id = p_id;
	}
	public String getP_name() {
		return p_name;
	}
	public void setP_name(String p_name) {
		this.p_name = p_name;
	}
	public Double getP_price() {
		return P_price;
	}
	public void setP_price(Double p_price) {
		P_price = p_price;
	}
	public GoodsBeen(int p_id, String p_name, Double p_price) {
		super();
		this.p_id = p_id;
		this.p_name = p_name;
		P_price = p_price;
	}
	public GoodsBeen() {
		super();
		// TODO Auto-generated constructor stub
	}
	
	
}

Reducer:

public class GoodsReducer extends Reducer<GoodsBeen, NullWritable, GoodsBeen, NullWritable>{

	@Override
	protected void reduce(GoodsBeen key, Iterable<NullWritable> value,
		Context context)
			throws IOException, InterruptedException {
		// TODO Auto-generated method stub
		context.write(key, NullWritable.get());
	}
	
}

Partition:

public class GoodPartition extends Partitioner<GoodsBeen, NullWritable>{

	@Override
	public int getPartition(GoodsBeen key, NullWritable value, int partition) {
		// TODO Auto-generated method stub
		return (key.getP_id()&Integer.MAX_VALUE)%partition;
	}
	

}

Group:

public class GoodGroup extends WritableComparator{

	public GoodGroup() {
		super(GoodsBeen.class,true);
		// TODO Auto-generated constructor stub
	}

	@Override
	public int compare(WritableComparable a, WritableComparable b) {
		// TODO Auto-generated method stub
		GoodsBeen aa = (GoodsBeen)a;
		GoodsBeen bb = (GoodsBeen)b;
		int rs = 0;
		if(aa.getP_id()>bb.getP_id()) {
			rs = 1;
		}
		if(aa.getP_id()<bb.getP_id()) {
			rs =-1;
		}
		if(aa.getP_id()==bb.getP_id())
		{
			rs = 0;
		}
		
		return rs;
	}
	

}

这个构造必须加，不然会报空指针异常，需要指定你要进行辅助排序的class，并且，相同对象的话，我们就赋值0，不给予操作，这样就可以获得每个分区一行数据

Job:

public class GoodJobDrive {

	public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {
		// TODO Auto-generated method stub
		Configuration conf = new Configuration();
		Job job = Job.getInstance(conf);
		
		job.setJarByClass(GoodJobDrive.class);
		job.setMapperClass(GoodMapper.class);
		job.setReducerClass(GoodsReducer.class);
		
		job.setMapOutputKeyClass(GoodsBeen.class);
		job.setMapOutputValueClass(NullWritable.class);
		
		job.setOutputKeyClass(GoodsBeen.class);
		job.setOutputValueClass(NullWritable.class);
		
		job.setGroupingComparatorClass(GoodGroup.class);
		
		job.setPartitionerClass(GoodPartition.class);
		job.setNumReduceTasks(3);
		
		FileInputFormat.setInputPaths(job, new Path("B:/笔记/数据素材/商品表.txt"));
		FileOutputFormat.setOutputPath(job, new Path("B:/笔记/数据素材/商品表测试"));
		
		boolean waitForCompletion = job.waitForCompletion(true);
		System.out.println(waitForCompletion);
		
	}

}