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第二个MapReduce

大家在学习Hadoop的MapReduce的时候，90%的第一个程序都是WordCount，所以在这里分享一下我的第二个MapReduce程序。对于学习编程语言的人来说，有时候代码是最好的沟通方式之一。

 1 package com.zhongxin.mr;
 2 
 3 import org.apache.hadoop.conf.Configuration;
 4 import org.apache.hadoop.fs.Path;
 5 import org.apache.hadoop.io.LongWritable;
 6 import org.apache.hadoop.io.Text;
 7 import org.apache.hadoop.mapreduce.Job;
 8 import org.apache.hadoop.mapreduce.Mapper;
 9 import org.apache.hadoop.mapreduce.Reducer;
10 import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
11 import org.apache.hadoop.mapreduce.lib.input.TextInputFormat;
12 import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
13 import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;
14 
15 import java.io.IOException;
16 import java.math.BigDecimal;
17 import java.util.regex.Pattern;
18 
19 /**
20  * 用户已收本息
21  * Created by DingYS on 2017/11/21.
22  */
23 public class UserReceiveAmount {
24 
25     public static class Map extends Mapper<LongWritable,Text,Text,Text>{
26         private Text outKey = new Text();
27         private Text outValue = new Text();
28         private Pattern pattern = Pattern.compile(",");
29 
30 
31         @Override
32         public void map(LongWritable key,Text value,Context context) throws IOException,InterruptedException{
33             // 利息
34             BigDecimal interest = new BigDecimal(0);
35             // 本金
36             BigDecimal capital = new BigDecimal(0);
37             String splits[] = pattern.split(String.valueOf(value));
38             String onwerType = splits[2];
39             String fundsDirection = splits[6];
40             String tradeType = splits[5];
41             String penaltyAmount = splits[15];
42             String tradeAmount = splits[7];
43             String tradeShare = splits[8];
44             String ownerCustomNo = splits[1];
45             if("USER".equals(onwerType) && "INCR".equals(fundsDirection) && !Pattern.matches("CURRENT_.*?",tradeType)){
46                 if("INTEREST".equals(tradeType) && ("null".equals(penaltyAmount) || "".equals(penaltyAmount) ||"0.00".equals(penaltyAmount))){
47                     interest =new BigDecimal(Double.parseDouble(tradeAmount)).setScale(2,BigDecimal.ROUND_HALF_UP);
48                 }else{
49                         interest = new BigDecimal(Double.parseDouble(tradeAmount)).subtract(new BigDecimal(Double.parseDouble(tradeShare))).setScale(2,BigDecimal.ROUND_HALF_UP);
50                         capital = new BigDecimal(Double.parseDouble(tradeShare)).setScale(2,BigDecimal.ROUND_HALF_UP);
51                 }
52                 outKey.set(ownerCustomNo);
53                 outValue.set(String.valueOf(interest) + pattern + String.valueOf(capital));
54                 context.write(outKey,outValue);
55             }
56         }
57     }
58 
59     public static class Reduce extends Reducer<Text,Text,Text,Text>{
60 
61         public void reduce(Text key,Iterable<Text> values,Context context) throws IOException,InterruptedException{
62             Text outValue = new Text();
63             BigDecimal interest = new BigDecimal(0);
64             BigDecimal capital = new BigDecimal(0);
65             for(Text value:values){
66                 String[] splits = value.toString().split(",");
67                 interest = interest.add(new BigDecimal(Double.parseDouble(splits[0]))).setScale(2,BigDecimal.ROUND_HALF_UP);
68                 capital = capital.add(new BigDecimal(Double.parseDouble(splits[1]))).setScale(2,BigDecimal.ROUND_HALF_UP);
69             }
70             outValue.set(String.valueOf(interest) + "\t" + String.valueOf(capital));
71             context.write(key,outValue);
72         }
73     }
74 
75     public static void main(String[] args) throws Exception{
76         Configuration config = new Configuration();
77         Job job = Job.getInstance(config);
78         job.setJobName("userReceiveAmount");
79         job.setJarByClass(UserReceiveAmount.class);
80 
81         job.setOutputKeyClass(Text.class);
82         job.setOutputValueClass(Text.class);
83 
84         job.setMapperClass(Map.class);
85         job.setReducerClass(Reduce.class);
86 
87         job.setInputFormatClass(TextInputFormat.class);
88         job.setOutputFormatClass(TextOutputFormat.class);
89 
90         FileInputFormat.addInputPath(job,new Path(args[0]));
91         FileOutputFormat.setOutputPath(job,new Path(args[1]));
92 
93         job.waitForCompletion(true);
94 
95     }
96 }

对于看懂mapReduce这个程序，有一个非常关键的点就是：map每次读取一行数据，相同key的数据进入到同一个reduce中。

上面是将统计结果输出到hdfs上，下面来一个输出到Hbase中的，请看码

package com.zhongxin.mr;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.hbase.HBaseConfiguration;
import org.apache.hadoop.hbase.client.Mutation;
import org.apache.hadoop.hbase.client.Put;
import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
import org.apache.hadoop.hbase.mapreduce.TableMapReduceUtil;
import org.apache.hadoop.hbase.mapreduce.TableReducer;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;

import java.io.IOException;
import java.math.BigDecimal;
import java.util.regex.Pattern;

/**
 * 用户已收本息
 * Created by DingYS on 2017/11/21.
 */
public class UserReceiveAmount {

    public static class Map extends Mapper<LongWritable,Text,Text,Text>{
        private Text outKey = new Text();
        private Text outValue = new Text();
        private Pattern pattern = Pattern.compile(",");


        @Override
        public void map(LongWritable key,Text value,Context context) throws IOException,InterruptedException{
            // 利息
            BigDecimal interest = new BigDecimal(0);
            // 本金
            BigDecimal capital = new BigDecimal(0);
            String splits[] = pattern.split(String.valueOf(value));
            String onwerType = splits[2];
            String fundsDirection = splits[6];
            String tradeType = splits[5];
            String penaltyAmount = splits[15];
            String tradeAmount = splits[7];
            String tradeShare = splits[8];
            String ownerCustomNo = splits[1];
            if("USER".equals(onwerType) && "INCR".equals(fundsDirection) && !Pattern.matches("CURRENT_.*?",tradeType)){
                if("INTEREST".equals(tradeType) && ("null".equals(penaltyAmount) || "".equals(penaltyAmount) ||"0.00".equals(penaltyAmount))){
                    interest =new BigDecimal(Double.parseDouble(tradeAmount)).setScale(2,BigDecimal.ROUND_HALF_UP);
                }else{
                        interest = new BigDecimal(Double.parseDouble(tradeAmount)).subtract(new BigDecimal(Double.parseDouble(tradeShare))).setScale(2,BigDecimal.ROUND_HALF_UP);
                        capital = new BigDecimal(Double.parseDouble(tradeShare)).setScale(2,BigDecimal.ROUND_HALF_UP);
                }
                outKey.set(ownerCustomNo);
                outValue.set(String.valueOf(interest) + pattern + String.valueOf(capital));
                context.write(outKey,outValue);
            }
        }
    }

    public static class Reduce extends TableReducer<Text,Text,ImmutableBytesWritable> {

        ImmutableBytesWritable k = new ImmutableBytesWritable();

        public void reduce(Text key,Iterable<Text> values,Context context) throws IOException,InterruptedException{
            BigDecimal interest = new BigDecimal(0);
            BigDecimal capital = new BigDecimal(0);
            for(Text value:values){
                String[] splits = value.toString().split(",");
                interest = interest.add(new BigDecimal(Double.parseDouble(splits[0]))).setScale(2,BigDecimal.ROUND_HALF_UP);
                capital = capital.add(new BigDecimal(Double.parseDouble(splits[1]))).setScale(2,BigDecimal.ROUND_HALF_UP);
            }
            String family = "info";
            Put put = new Put(String.valueOf(key).getBytes());
            put.addColumn(family.getBytes(),"interest".getBytes(),String.valueOf(interest).getBytes());
            put.addColumn(family.getBytes(),"capital".getBytes(),String.valueOf(capital).getBytes());
            k.set(key.getBytes());
            context.write(k,put);
        }
    }

    public static void main(String[] args) throws Exception{
        Configuration config = HBaseConfiguration.create();
        Job job = Job.getInstance(config,"userReceiveAmount");
        job.setJarByClass(UserReceiveAmount.class);

        FileInputFormat.addInputPath(job,new Path(args[0]));
        job.setMapperClass(Map.class);
        TableMapReduceUtil.initTableReducerJob("userReceiveAmount",Reduce.class,job);

        job.setMapOutputKeyClass(Text.class);
        job.setMapOutputValueClass(Text.class);

        job.setOutputKeyClass(ImmutableBytesWritable.class);
        job.setOutputValueClass(Text.class);
        job.setOutputValueClass(Mutation.class);

        System.exit(job.waitForCompletion(true) ? 0 : 1);

    }
}

　　注意点：rowkey的类型需要是String，如果是Text，需要Text.toString()一下，Text中重写了toString()方法，经测试String.valueOf()也没问题

Put put = new Put(rowkey.getBytes());

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原文地址：https://www.cnblogs.com/Smilence1024/p/7884679.html