二次排序
一:二次排序自定义GroupingComparator
1.问题:现有如下订单数据,需要求出每一个订单中成交金额最大的一笔交易
|
订单id |
商品id |
成交金额 |
|
Order_0000001 |
Pdt_01 |
222.8 |
|
Order_0000001 |
Pdt_05 |
25.8 |
|
Order_0000002 |
Pdt_03 |
522.8 |
|
Order_0000002 |
Pdt_04 |
122.4 |
|
Order_0000002 |
Pdt_05 |
722.4 |
|
Order_0000003 |
Pdt_01 |
222.8 |
|
Order_0000003 |
Pdt_02 |
22.8 |
|
Order_0000004 |
Pdt_03 |
522.8 |
|
Order_0000004 |
Pdt_04 |
122.4 |
|
Order_0000004 |
Pdt_05 |
1034.4 |
2.分析
a、利用“订单id和成交金额”作为key，可以将map阶段读取到的所有订单数据按照id分区，按照金额排序，发送到reduce
b、在reduce端利用groupingcomparator将订单id相同的kv聚合成组，然后取第一个即是最大值
3.实现
1 package com.oracle.www.secondarySort_Max2; 2 3 import java.io.IOException; 4 5 import org.apache.hadoop.conf.Configuration; 6 import org.apache.hadoop.fs.FileSystem; 7 import org.apache.hadoop.fs.Path; 8 import org.apache.hadoop.io.LongWritable; 9 import org.apache.hadoop.io.NullWritable; 10 import org.apache.hadoop.io.Text; 11 import org.apache.hadoop.mapreduce.Job; 12 import org.apache.hadoop.mapreduce.Mapper; 13 import org.apache.hadoop.mapreduce.Reducer; 14 import org.apache.hadoop.mapreduce.lib.input.FileInputFormat; 15 import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;; 16 17 public class SecondarySort { 18 static class MyMapper extends Mapper<LongWritable, Text, OrderBean, NullWritable> { 19 @Override 20 protected void map(LongWritable key, Text value, 21 Mapper<LongWritable, Text, OrderBean, NullWritable>.Context context) 22 throws IOException, InterruptedException { 23 String[] datas = value.toString().split("\t"); 24 OrderBean bean = new OrderBean(datas[0], datas[1], Double.parseDouble(datas[2])); 25 context.write(bean, NullWritable.get()); 26 } 27 } 28 29 static class MyReducer extends Reducer<OrderBean, NullWritable, OrderBean, NullWritable> { 30 @Override 31 protected void reduce(OrderBean key, Iterable<NullWritable> value, 32 Reducer<OrderBean, NullWritable, OrderBean, NullWritable>.Context context) 33 throws IOException, InterruptedException { 34 context.write(key, NullWritable.get()); 35 } 36 } 37 38 public static void main(String[] args) throws ClassNotFoundException, InterruptedException { 39 Configuration conf = new Configuration(); 40 try { 41 Job job = Job.getInstance(); 42 43 job.setJarByClass(SecondarySort.class); 44 job.setMapperClass(MyMapper.class); 45 job.setReducerClass(MyReducer.class); 46 job.setPartitionerClass(MyPartition.class); 47 job.setGroupingComparatorClass(MyGroup.class); 48 49 job.setMapOutputKeyClass(OrderBean.class); 50 job.setMapOutputValueClass(NullWritable.class); 51 52 job.setOutputKeyClass(OrderBean.class); 53 job.setOutputValueClass(NullWritable.class); 54 55 job.setNumReduceTasks(3); 56 57 Path outPath = new Path("hdfs://192.168.9.13:8020/Order_item_data2"); 58 FileSystem fs = outPath.getFileSystem(conf); 59 if (fs.exists(outPath)) { 60 fs.delete(outPath, true); 61 } 62 FileInputFormat.setInputPaths(job, new Path("hdfs://192.168.9.13:8020/Order_item")); 63 FileOutputFormat.setOutputPath(job, outPath); 64 job.waitForCompletion(true); 65 66 } catch (IOException e) { 67 // TODO Auto-generated catch block 68 e.printStackTrace(); 69 } 70 71 } 72 73 }
1 package com.oracle.www.secondarySort_Max2; 2 3 import org.apache.hadoop.io.NullWritable; 4 import org.apache.hadoop.mapreduce.Partitioner; 5 6 public class MyPartition extends Partitioner<OrderBean, NullWritable> { 7 8 @Override 9 public int getPartition(OrderBean key, NullWritable value, int numPartitions) { 10 return key.getOrderId().hashCode() & Integer.MAX_VALUE % numPartitions; 11 } 12 13 }
1 package com.oracle.www.secondarySort_Max2; 2 3 import org.apache.hadoop.io.WritableComparable; 4 import org.apache.hadoop.io.WritableComparator; 5 6 public class MyGroup extends WritableComparator { 7 public MyGroup() { 8 super(); 9 } 10 11 @Override 12 public int compare(WritableComparable a, WritableComparable b) { 13 OrderBean bean1 = (OrderBean) a; 14 OrderBean bean2 = (OrderBean) b; 15 return bean1.getOrderId().compareTo(bean2.getOrderId()); 16 17 } 18 19 }
1 package com.oracle.www.secondarySort_Max2; 2 3 import java.io.DataInput; 4 import java.io.DataOutput; 5 import java.io.IOException; 6 7 import org.apache.hadoop.io.WritableComparable; 8 9 public class OrderBean implements WritableComparable<OrderBean> { 10 private String orderId; 11 private String productId; 12 private double price; 13 14 public OrderBean() { 15 16 } 17 18 public OrderBean(String orderId, String productId, double price) { 19 this.orderId = orderId; 20 this.productId = productId; 21 this.price = price; 22 } 23 24 public String getOrderId() { 25 return orderId; 26 } 27 28 public void setOrderId(String orderId) { 29 this.orderId = orderId; 30 } 31 32 public String getProductId() { 33 return productId; 34 } 35 36 public void setProductId(String productId) { 37 this.productId = productId; 38 } 39 40 public double getPrice() { 41 return price; 42 } 43 44 public void setPrice(double price) { 45 this.price = price; 46 } 47 48 /* 49 * (non-Javadoc) 50 * 51 * @see java.lang.Object#toString() 52 */ 53 @Override 54 public String toString() { 55 return "OrderBean [orderId=" + orderId + ", productId=" + productId + ", price=" + price + "]"; 56 } 57 58 @Override 59 public void write(DataOutput out) throws IOException { 60 out.writeUTF(orderId); 61 out.writeUTF(productId); 62 out.writeDouble(price); 63 } 64 65 @Override 66 public void readFields(DataInput in) throws IOException { 67 this.orderId = in.readUTF(); 68 this.productId = in.readUTF(); 69 this.price = in.readDouble(); 70 71 } 72 73 @Override 74 public int compareTo(OrderBean o) { 75 // 先按订单id进行排序,再按销售进行排序 76 int temp = this.orderId.compareTo(o.orderId); 77 if (temp == 0) { 78 // this.-o. 79 // 0:顺序不发生改变(set集合会覆盖,list集合顺序不发生改变) 80 // 1(>0):当前对象大,顺序往后放 81 // -1(<0):当前对象小,顺序往前放 82 double error = this.getPrice() - o.getPrice(); 83 if (error > 0) { 84 return -1; 85 } else { 86 return 1; 87 } 88 } 89 return temp; 90 } 91 92 }
