大数据学习——mapreduce学习topN问题

求每一个订单中成交金额最大的那一笔 top1

数据

Order_0000001,Pdt_01,222.8

Order_0000001,Pdt_05,25.8

Order_0000002,Pdt_05,325.8

Order_0000002,Pdt_03,522.8

Order_0000002,Pdt_04,122.4

Order_0000003,Pdt_01,222.8

Order_0000003,Pdt_01,322.8

pom.xml

<?xml version="1.0" encoding="UTF-8"?>

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">

  <modelVersion>4.0.0</modelVersion>

  <groupId>com.cyf</groupId>

  <artifactId>MapReduceCases</artifactId>

  <packaging>jar</packaging>

  <version>1.0</version>

  <properties>

    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>

    <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>

  </properties>

  <dependencies>

    <dependency>

      <groupId>org.apache.hadoop</groupId>

      <artifactId>hadoop-common</artifactId>

      <version>2.6.4</version>

    </dependency>

    <dependency>

      <groupId>org.apache.hadoop</groupId>

      <artifactId>hadoop-hdfs</artifactId>

      <version>2.6.4</version>

    </dependency>

    <dependency>

      <groupId>org.apache.hadoop</groupId>

      <artifactId>hadoop-client</artifactId>

      <version>2.6.4</version>

    </dependency>

    <dependency>

      <groupId>org.apache.hadoop</groupId>

      <artifactId>hadoop-mapreduce-client-core</artifactId>

      <version>2.6.4</version>

    </dependency>

    <dependency>

      <groupId>com.alibaba</groupId>

      <artifactId>fastjson</artifactId>

      <version>1.1.40</version>

    </dependency>

    <dependency>

      <groupId>mysql</groupId>

      <artifactId>mysql-connector-java</artifactId>

      <version>5.1.36</version>

    </dependency>

  </dependencies>

  <build>

    <plugins>

      <plugin>

        <artifactId>maven-assembly-plugin</artifactId>

        <configuration>

          <appendAssemblyId>false</appendAssemblyId>

          <descriptorRefs>

            <descriptorRef>jar-with-dependencies</descriptorRef>

          </descriptorRefs>

          <archive>

            <manifest>

              <mainClass>cn.itcast.mapreduce.top.one.TopOne</mainClass>

            </manifest>

          </archive>

        </configuration>

        <executions>

          <execution>

            <id>make-assembly</id>

            <phase>package</phase>

            <goals>

              <goal>assembly</goal>

            </goals>

          </execution>

        </executions>

      </plugin>

    </plugins>

  </build>

</project>

package cn.itcast.mapreduce.top.one;

import java.io.DataInput;

import java.io.DataOutput;

import java.io.IOException;

import org.apache.hadoop.io.DoubleWritable;

import org.apache.hadoop.io.Text;

import org.apache.hadoop.io.WritableComparable;

/**

 *

 *

 */

public class OrderBean implements WritableComparable<OrderBean> {

    private Text itemid;

    private DoubleWritable amount;

    public OrderBean() {

    }

    public OrderBean(Text itemid, DoubleWritable amount) {

        set(itemid, amount);

    }

    public void set(Text itemid, DoubleWritable amount) {

        this.itemid = itemid;

        this.amount = amount;

    }

    public Text getItemid() {

        return itemid;

    }

    public DoubleWritable getAmount() {

        return amount;

    }

    public int compareTo(OrderBean o) {

        int cmp = this.itemid.compareTo(o.getItemid());

        if (cmp == 0) {

            cmp = -this.amount.compareTo(o.getAmount());

        }

        return cmp;

    }

    public void write(DataOutput out) throws IOException {

        out.writeUTF(itemid.toString());

        out.writeDouble(amount.get());

    }

    public void readFields(DataInput in) throws IOException {

        String readUTF = in.readUTF();

        double readDouble = in.readDouble();

        this.itemid = new Text(readUTF);

        this.amount = new DoubleWritable(readDouble);

    }

    @Override

    public String toString() {

        return itemid.toString() + "\t" + amount.get();

    }

}

package cn.itcast.mapreduce.top.one;

import org.apache.hadoop.io.WritableComparable;

import org.apache.hadoop.io.WritableComparator;

/**

 *

 */

public class ItemidGroupingComparator extends WritableComparator {

    protected ItemidGroupingComparator() {

        super(OrderBean.class, true);

    }

    @Override

    public int compare(WritableComparable a, WritableComparable b) {

        OrderBean abean = (OrderBean) a;

        OrderBean bbean = (OrderBean) b;

        //��item_id��ͬ��bean����Ϊ��ͬ���Ӷ�ۺ�Ϊһ��

        return abean.getItemid().compareTo(bbean.getItemid());

    }

}

package cn.itcast.mapreduce.top.one;

import org.apache.hadoop.io.NullWritable;

import org.apache.hadoop.mapreduce.Partitioner;

public class ItemIdPartitioner extends Partitioner<OrderBean, NullWritable> {

    @Override

    public int getPartition(OrderBean key, NullWritable value, int numPartitions) {

        //ָ

        return (key.getItemid().hashCode() & Integer.MAX_VALUE) % numPartitions;

    }

}

package cn.itcast.mapreduce.top.one;

import java.io.IOException;

import org.apache.commons.lang.StringUtils;

import org.apache.hadoop.conf.Configuration;

import org.apache.hadoop.fs.Path;

import org.apache.hadoop.io.DoubleWritable;

import org.apache.hadoop.io.LongWritable;

import org.apache.hadoop.io.NullWritable;

import org.apache.hadoop.io.Text;

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;

import com.sun.xml.bind.v2.schemagen.xmlschema.List;

/**

 * ����secondarysort�������ÿ��item����������ļ�¼

 *

 * @author AllenWoon

 */

public class TopOne {

    static class TopOneMapper extends Mapper<LongWritable, Text, OrderBean, NullWritable> {

        OrderBean bean = new OrderBean();

        /* Text itemid = new Text(); */

        @Override

        protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {

            String line = value.toString();

            String[] fields = StringUtils.split(line, ",");

            bean.set(new Text(fields[0]), new DoubleWritable(Double.parseDouble(fields[2])));

            context.write(bean, NullWritable.get());

        }

    }

    static class TopOneReducer extends Reducer<OrderBean, NullWritable, OrderBean, NullWritable> {

        @Override

        protected void reduce(OrderBean key, Iterable<NullWritable> values, Context context) throws IOException, InterruptedException {

            context.write(key, NullWritable.get());

        }

    }

    public static void main(String[] args) throws Exception {

        Configuration conf = new Configuration();

        Job job = Job.getInstance(conf);

//        job.setJarByClass(TopOne.class);

        //告诉框架，我们的程序所在jar包的位置

        job.setJar("/root/TopOne.jar");

        job.setMapperClass(TopOneMapper.class);

        job.setReducerClass(TopOneReducer.class);

        job.setOutputKeyClass(OrderBean.class);

        job.setOutputValueClass(NullWritable.class);

        FileInputFormat.setInputPaths(job, new Path("/top/input"));

        FileOutputFormat.setOutputPath(job, new Path("/top/output1"));

        // FileInputFormat.setInputPaths(job, new Path(args[0]));

        // FileOutputFormat.setOutputPath(job, new Path(args[1]));

        // ָ��shuffle��ʹ�õ�GroupingComparator��

        job.setGroupingComparatorClass(ItemidGroupingComparator.class);

        // ָ��shuffle��ʹ�õ�partitioner��

        job.setPartitionerClass(ItemIdPartitioner.class);

        job.setNumReduceTasks(1);

        job.waitForCompletion(true);

    }

}

创建文件夹

hadoop fs -mkdir -p /top/input

上传数据

hadoop fs -put top.txt /top/input

运行

hadoop jar TopOne.jar cn.itcast.mapreduce.top.one.TopOne

运行结果

topN

<?xml version="1.0" encoding="UTF-8"?>

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">

    <modelVersion>4.0.0</modelVersion>

    <groupId>com.cyf</groupId>

    <artifactId>MapReduceCases</artifactId>

    <packaging>jar</packaging>

    <version>1.0</version>

    <properties>

        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>

        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>

    </properties>

    <dependencies>

        <dependency>

            <groupId>org.apache.hadoop</groupId>

            <artifactId>hadoop-common</artifactId>

            <version>2.6.4</version>

        </dependency>

        <dependency>

            <groupId>org.apache.hadoop</groupId>

            <artifactId>hadoop-hdfs</artifactId>

            <version>2.6.4</version>

        </dependency>

        <dependency>

            <groupId>org.apache.hadoop</groupId>

            <artifactId>hadoop-client</artifactId>

            <version>2.6.4</version>

        </dependency>

        <dependency>

            <groupId>org.apache.hadoop</groupId>

            <artifactId>hadoop-mapreduce-client-core</artifactId>

            <version>2.6.4</version>

        </dependency>

        <dependency>

            <groupId>com.alibaba</groupId>

            <artifactId>fastjson</artifactId>

            <version>1.1.40</version>

        </dependency>

        <dependency>

            <groupId>mysql</groupId>

            <artifactId>mysql-connector-java</artifactId>

            <version>5.1.36</version>

        </dependency>

    </dependencies>

    <build>

        <plugins>

            <plugin>

                <artifactId>maven-assembly-plugin</artifactId>

                <configuration>

                    <appendAssemblyId>false</appendAssemblyId>

                    <descriptorRefs>

                        <descriptorRef>jar-with-dependencies</descriptorRef>

                    </descriptorRefs>

                    <archive>

                        <manifest>

                            <mainClass>cn.itcast.mapreduce.top.n.TopN</mainClass>

                        </manifest>

                    </archive>

                </configuration>

                <executions>

                    <execution>

                        <id>make-assembly</id>

                        <phase>package</phase>

                        <goals>

                            <goal>assembly</goal>

                        </goals>

                    </execution>

                </executions>

            </plugin>

        </plugins>

    </build>

</project>

package cn.itcast.mapreduce.top.n;

import java.io.DataInput;

import java.io.DataOutput;

import java.io.IOException;

import org.apache.hadoop.io.DoubleWritable;

import org.apache.hadoop.io.Text;

import org.apache.hadoop.io.WritableComparable;

/**

 * ������Ϣbean��ʵ��hadoop�����л�����

 */

public class OrderBean implements WritableComparable<OrderBean> {

    private Text itemid;

    private DoubleWritable amount;

    public OrderBean() {

    }

    public OrderBean(Text itemid, DoubleWritable amount) {

        set(itemid, amount);

    }

    public void set(Text itemid, DoubleWritable amount) {

        this.itemid = itemid;

        this.amount = amount;

    }

    public Text getItemid() {

        return itemid;

    }

    public DoubleWritable getAmount() {

        return amount;

    }

    public int compareTo(OrderBean o) {

        int cmp = this.itemid.compareTo(o.getItemid());

        if (cmp == 0) {

            cmp = -this.amount.compareTo(o.getAmount());

        }

        return cmp;

    }

    public void write(DataOutput out) throws IOException {

        out.writeUTF(itemid.toString());

        out.writeDouble(amount.get());

    }

    public void readFields(DataInput in) throws IOException {

        String readUTF = in.readUTF();

        double readDouble = in.readDouble();

        this.itemid = new Text(readUTF);

        this.amount = new DoubleWritable(readDouble);

    }

    @Override

    public String toString() {

        return itemid.toString() + "\t" + amount.get();

    }

    /*

     * @Override public int hashCode() {

     *

     * return this.itemid.hashCode(); }

     */

    @Override

    public boolean equals(Object obj) {

        OrderBean bean = (OrderBean) obj;

        return bean.getItemid().equals(this.itemid);

    }

}

package cn.itcast.mapreduce.top.n;

import org.apache.hadoop.io.WritableComparable;

import org.apache.hadoop.io.WritableComparator;

/**

 * ���ڿ���shuffle�����reduce�˶�kv�Եľۺ��߼�

 */

public class ItemidGroupingComparator extends WritableComparator {

    protected ItemidGroupingComparator() {

        super(OrderBean.class, true);

    }

    @Override

    public int compare(WritableComparable a, WritableComparable b) {

        OrderBean abean = (OrderBean) a;

        OrderBean bbean = (OrderBean) b;

        //��item_id��ͬ��bean����Ϊ��ͬ���Ӷ�ۺ�Ϊһ��

        return abean.getItemid().compareTo(bbean.getItemid());

    }

}

package cn.itcast.mapreduce.top.n;

import org.apache.hadoop.io.NullWritable;

import org.apache.hadoop.mapreduce.Partitioner;

public class ItemIdPartitioner extends Partitioner<OrderBean, NullWritable> {

    @Override

    public int getPartition(OrderBean key, NullWritable value, int numPartitions) {

        //ָ��item_id��ͬ��bean������ͬ��reducer task

        return (key.getItemid().hashCode() & Integer.MAX_VALUE) % numPartitions;

    }

}

package cn.itcast.mapreduce.top.n;

import java.io.IOException;

import org.apache.commons.lang.StringUtils;

import org.apache.hadoop.conf.Configuration;

import org.apache.hadoop.fs.Path;

import org.apache.hadoop.fs.shell.Count;

import org.apache.hadoop.io.DoubleWritable;

import org.apache.hadoop.io.LongWritable;

import org.apache.hadoop.io.NullWritable;

import org.apache.hadoop.io.Text;

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;

import com.sun.xml.bind.v2.schemagen.xmlschema.List;

/**

 * ����secondarysort�������ÿ��item����������ļ�¼

 */

public class TopN {

    static class TopNMapper extends Mapper<LongWritable, Text, OrderBean, OrderBean> {

        OrderBean v = new OrderBean();

        Text k = new Text();

        @Override

        protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {

            String line = value.toString();

            String[] fields = StringUtils.split(line, ",");

            k.set(fields[0]);

            v.set(new Text(fields[0]), new DoubleWritable(Double.parseDouble(fields[2])));

            context.write(v, v);

        }

    }

    static class TopNReducer extends Reducer<OrderBean, OrderBean, NullWritable, OrderBean> {

        int topn = 1;

        int count = 0;

        @Override

        protected void setup(Context context) throws IOException, InterruptedException {

            Configuration conf = context.getConfiguration();

            topn = Integer.parseInt(conf.get("topn"));

        }

        @Override

        protected void reduce(OrderBean key, Iterable<OrderBean> values, Context context) throws IOException, InterruptedException {

            for (OrderBean bean : values) {

                if ((count++) == topn) {

                    count = 0;

                    return;

                }

                context.write(NullWritable.get(), bean);

            }

        }

    }

    public static void main(String[] args) throws Exception {

        Configuration conf = new Configuration();

        // ָ������classpath�µ��û��Զ��������ļ�

//        conf.addResource("userconfig.xml");

//        System.out.println(conf.get("top.n"));

        // Ҳ����ֱ���ô��������ò���ݸ�mapreduce�����ڲ�ʹ��

        conf.set("topn", "2");

        Job job = Job.getInstance(conf);

//        job.setJarByClass(TopN.class);

        //告诉框架，我们的程序所在jar包的位置

        job.setJar("/root/TopOne.jar");

        job.setMapperClass(TopNMapper.class);

        job.setReducerClass(TopNReducer.class);

        job.setMapOutputKeyClass(OrderBean.class);

        job.setMapOutputValueClass(OrderBean.class);

        job.setOutputKeyClass(NullWritable.class);

        job.setOutputValueClass(OrderBean.class);

        FileInputFormat.setInputPaths(job, new Path("/top/input"));

        FileOutputFormat.setOutputPath(job, new Path("/top/outputn"));

        // ָ��shuffle��ʹ�õ�partitioner��

        job.setPartitionerClass(ItemIdPartitioner.class);

        job.setGroupingComparatorClass(ItemidGroupingComparator.class);

        job.setNumReduceTasks(1);

        job.waitForCompletion(true);

    }

}

打包并运行

运行

hadoop jar TopN.jar cn.itcast.mapreduce.top.n.TopN

运行结果 n=2

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