maprecuce系列（4）——reduce端join算法实现

原创 于 2017-03-19 22:30:19 发布 · 665 阅读 · 1 ·
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文章标签：

#mapreduce

本文介绍如何使用MapReduce技术实现订单表与商品信息表的联表查询，并提供了一个具体的Java实现案例。通过自定义Bean类存储数据并利用MapReduce进行处理，最终实现了两表的高效合并。

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一、需求

1、如下订单表：id、date、pid、amount

1001,20160710,P0001,2
1002,20160710,P0001,3
1002,20170710,P0002,3
1001,20160710,P0001,2
1002,20140710,P0003,3
1003,20150710,P0002,3

2、如下商品信息表：id,panme,category_id,price

P0001,xiaomi5,1000,2
P0002,chuiziT1,1000,3
P0003,meizu,1001,3

其中订单表中的pid对应商品列表中的id。
如果进行聊表查询所有的详细信息，想想，如果是在sql中就非常简单了：select a.id,a.date,b.name,b.category_id,b.price from t_order a join t_product b on a.pid = b.id
3、思路：
如果利用mapreduce进行处理，其实我们可以想象，
在maptask后，同样的key被归为一组，传递给reduceTask来进行处理的，这时我如果把两个表以同一个key来map，所以最后在，reduce的时候合并起来就肯定是订单和商品的详细信息了。

二、代码实现

1、首先定义个bean包含所有的订单信息和商品信息，当同时得有一个flag来区分这个bean到底是订单，还是商品：
InfoBean1.java

package join;


import org.apache.hadoop.io.Writable;

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

/**
 *
 * Created by tianjun on 2017/3/17.
 */
public class InfoBean1  implements Writable {
    private int order_id;
    private String dateString;
    private String p_id;
    private int amount;
    private String pname;
    private int category_id;
    private float price;
    //flag=0表示封装的是订单表记录
    //flag=1表示封装的是产品信息记录
    private String flag;


    public int getOrder_id() {
        return order_id;
    }

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

    public String getDateString() {
        return dateString;
    }

    public void setDateString(String dateString) {
        this.dateString = dateString;
    }

    public String getP_id() {
        return p_id;
    }

    public void setP_id(String p_id) {
        this.p_id = p_id;
    }

    public int getAmount() {
        return amount;
    }

    public void setAmount(int amount) {
        this.amount = amount;
    }

    public String getPname() {
        return pname;
    }

    public void setPname(String pname) {
        this.pname = pname;
    }

    public int getCategory_id() {
        return category_id;
    }

    public void setCategory_id(int category_id) {
        this.category_id = category_id;
    }

    public float getPrice() {
        return price;
    }

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

    public String getFlag() {
        return flag;
    }

    public void setFlag(String flag) {
        this.flag = flag;
    }

    public InfoBean1() {
    }

    public InfoBean1(int order_id, String dateString, String p_id, int amount, String pname, int category_id, float price, String flag) {
        this.order_id = order_id;
        this.dateString = dateString;
        this.p_id = p_id;
        this.amount = amount;
        this.pname = pname;
        this.category_id = category_id;
        this.price = price;
        this.flag = flag;
    }

    public void set(int order_id, String dateString, String p_id, int amount, String pname, int category_id, float price, String flag) {
        this.order_id = order_id;
        this.dateString = dateString;
        this.p_id = p_id;
        this.amount = amount;
        this.pname = pname;
        this.category_id = category_id;
        this.price = price;
        this.flag = flag;
    }


    @Override
    public void write(DataOutput out) throws IOException {

        out.writeInt(order_id);
        out.writeUTF(dateString);
        out.writeUTF(p_id);
        out.writeInt(amount);
        out.writeUTF(pname);
        out.writeInt(category_id);
        out.writeFloat(price);
        out.writeUTF(flag);
    }

    @Override
    public void readFields(DataInput in) throws IOException {
        order_id = in.readInt();
        dateString= in.readUTF();
        p_id = in.readUTF();
        amount = in.readInt();
        pname = in.readUTF();
        category_id = in.readInt();
        price = in.readFloat();
        flag = in.readUTF();
    }

    @Override
    public String toString() {
        return  "order_id=" + order_id +
                ", dateString='" + dateString + '\'' +
                ", p_id='" + p_id + '\'' +
                ", amount=" + amount +
                ", pname='" + pname + '\'' +
                ", category_id=" + category_id +
                ", price=" + price;
    }
}

2、join功能的实现：
Rjoin.java

package join;

import org.apache.commons.beanutils.BeanUtils;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
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.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.input.FileSplit;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;

import java.io.IOException;
import java.net.URI;
import java.net.URISyntaxException;
import java.util.ArrayList;

/**
 * Created by tianjun on 2017/3/17.
 */
public class Rjoin {

    static class RjoinMapper extends Mapper<LongWritable, Text, Text, InfoBean1> {

        InfoBean1 infoBean = new InfoBean1();
        Text k = new Text();


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

            String line = value.toString();

            FileSplit inputSplit = (FileSplit) context.getInputSplit();
            String name = inputSplit.getPath().getName();
            //通过文件名判断是那种数据
            String pid = "";
            if (name.startsWith("order")) {
                String[] fields = line.split(",");
                pid = fields[2];
                infoBean.set(Integer.parseInt(fields[0]), fields[1], pid, Integer.parseInt(fields[3]), "", 0, 0, "0");
            } else {
                String[] fields = line.split(",");
                pid = fields[0];
                infoBean.set(0, "", pid, 0, fields[1], Integer.parseInt(fields[2]), Float.parseFloat(fields[3]), "1");
            }

            k.set(pid);
            context.write(k, infoBean);
        }
    }

    static class RjoinReducer extends Reducer<Text, InfoBean1, InfoBean1, NullWritable> {
        @Override
        protected void reduce(Text key, Iterable<InfoBean1> values, Context context) throws IOException, InterruptedException {
            InfoBean1 pdBean = new InfoBean1();
            ArrayList<InfoBean1> orderBeans = new ArrayList<>();
            for (InfoBean1 bean : values) {
                if ("1".equals(bean.getFlag())) {
                    try {
                        BeanUtils.copyProperties(pdBean, bean);
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                } else {
                    InfoBean1 odBean = new InfoBean1();
                    try {
                        BeanUtils.copyProperties(odBean, bean);
                        orderBeans.add(odBean);
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            }

            for (InfoBean1 bean : orderBeans) {
                bean.setPname(pdBean.getPname());
                bean.setCategory_id(pdBean.getCategory_id());
                bean.setPrice(pdBean.getPrice());

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

    }

    public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException, URISyntaxException {
        String os = System.getProperty("os.name").toLowerCase();
        if (os.contains("windows")) {
            System.setProperty("HADOOP_USER_NAME", "root");
        }

        Configuration conf = new Configuration();

        conf.set("mapreduce.framework.name","yarn");
        conf.set("yarn.resourcemanager.hostname","mini01");
        conf.set("fs.defaultFS","hdfs://mini01:9000/");

//            默认就是local模式
//        conf.set("mapreduce.framework.name","local");
//        conf.set("mapreduce.jobtracker.address","local");
//        conf.set("fs.defaultFS","file:///");


        Job wcjob = Job.getInstance(conf);

        wcjob.setJar("F:/myWorkPlace/java/dubbo/demo/dubbo-demo/mr-demo1/target/mr.demo-1.0-SNAPSHOT.jar");

        //如果从本地拷贝，是不行的，这时需要使用setJar
//        wcjob.setJarByClass(Rjoin.class);

        wcjob.setMapperClass(RjoinMapper.class);
        wcjob.setReducerClass(RjoinReducer.class);

        //设置我们的业务逻辑Mapper类的输出key和value的数据类型
        wcjob.setMapOutputKeyClass(Text.class);
        wcjob.setMapOutputValueClass(InfoBean1.class);


        //设置我们的业务逻辑Reducer类的输出key和value的数据类型
        wcjob.setOutputKeyClass(InfoBean1.class);
        wcjob.setOutputValueClass(NullWritable.class);


        //如果不设置InputFormat，默认就是使用TextInputFormat.class
//        wcjob.setInputFormatClass(CombineFileInputFormat.class);
//        CombineFileInputFormat.setMaxInputSplitSize(wcjob,4194304);
//        CombineFileInputFormat.setMinInputSplitSize(wcjob,2097152);


        FileSystem fs = FileSystem.get(new URI("hdfs://mini01:9000"), new Configuration(), "root");
        Path path = new Path("hdfs://mini01:9000/wc/rjoin");
        if (fs.exists(path)) {
            fs.delete(path, true);
        }

        //指定要处理的数据所在的位置
        FileInputFormat.setInputPaths(wcjob, new Path("hdfs://mini01:9000/input/rjoin"));
        //指定处理完成之后的结果所保存的位置
        FileOutputFormat.setOutputPath(wcjob, new Path("hdfs://mini01:9000/wc/rjoin"));

        boolean res = wcjob.waitForCompletion(true);
        System.exit(res ? 0 : 1);

    }

}

三、结果

处理结果如下：

order_id=1001, dateString='20150710', p_id='P0001', amount=2, pname='xiaomi5', category_id=1000, price=2.0
order_id=1002, dateString='20150710', p_id='P0001', amount=3, pname='xiaomi5', category_id=1000, price=2.0
order_id=1001, dateString='20150710', p_id='P0001', amount=2, pname='xiaomi5', category_id=1000, price=2.0
order_id=1003, dateString='20150710', p_id='P0002', amount=3, pname='chuiziT1', category_id=1000, price=3.0
order_id=1002, dateString='20150710', p_id='P0002', amount=3, pname='chuiziT1', category_id=1000, price=3.0
order_id=1002, dateString='20150710', p_id='P0003', amount=3, pname='meizu', category_id=1001, price=3.0
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