hadoop入门 权威指南 气温统计案例

Hadoop 权威指南(第3版) 下载：https://download.csdn.net/download/henry_lin_wind/11036890

气象数据集的编码格式：安行并以ASCII格式存储，其中每一行是一条记录 

1-4     0169    
5-10    501360      # USAF weather station identifier 
11-15   99999       # WBAN weather station identifier
16-23   20170101    # 记录日期
24-27   0000        # 记录时间
28      4
29-34   +52130      # 纬度（1000倍）
35-41   +122520     # 经度（1000倍）
42-46   FM-12
47-51   +0433      # 海拔（米）
52-56   99999
57-60   V020
61-63   220         # 风向
64      1           # 质量代码
65      N
66-69   0010
70      1
71-75   02600       # 云高（米）
76      1
77      9
78      9
79-84   003700      # 能见距离（米）
85      1           # 质量代码
86      9
87      9
88-92   -0327       # 空气温度(摄氏度*10)
93      1
94-98   -0363       # 露点温度(摄氏度*10)
99      1           # 质量代码
100-104 10264       # 大气压力
105     1           # 质量代码

某地区2002年的气象数据：https://download.csdn.net/download/henry_lin_wind/11064461

本地模式的安装和部署可以参考我的博客 ：https://blog.csdn.net/Henry_Lin_Wind/article/details/88812421

1、创建Map/Reduce Project

新建input文件夹，用来存放气象数据。新建三个类，如下图：

1、MaxTemperature

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;

public class MaxTemperature extends Configured implements Tool {

	public static void main(String[] args) throws Exception {
        if (args.length != 2) {
            System.err
                    .println("Usage: MaxTemperature  
");
            System.exit(-1);
        }
        //Configuration conf = new Configuration();
        //conf.set("mapred.jar", "MaxTemperature.jar");
        //Job job = Job.getInstance(conf);
        Job job = new Job();
        job.setJarByClass(MaxTemperature.class);
        job.setJobName("Max temperature");
        FileInputFormat.addInputPath(job, new Path(args[0]));
        FileOutputFormat.setOutputPath(job, new Path(args[1]));
        job.setMapperClass(MaxTemperatureMapper.class);
        job.setReducerClass(MaxTemperatureReducer.class);
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(IntWritable.class);
        long currentTimeMillis = System.currentTimeMillis();
        System.out.println("开始调用");
        int result = job.waitForCompletion(true) ? 0 : 1;
        System.out.println("调用耗时 "+(System.currentTimeMillis()-currentTimeMillis)+" 毫秒");
        System.exit(result);
    }

    @Override
    public int run(String[] arg0) throws Exception {
        // TODO Auto-generated method stub
        return 0;
    }
}

 2、MaxTemperatureMapper

import java.io.IOException; 
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;

public class MaxTemperatureMapper extends Mapper { 

	 private static final int MISSING = 9999;

     @Override
     public void map(LongWritable key, Text value, Context context)
                     throws IOException, InterruptedException {
             String line = value.toString();
             String data = line.substring(15, 21);
             int airTemperature;
             if (line.charAt(87) == '+') { // parseInt doesn't like leading plus
                                                                            // signs
                     airTemperature = Integer.parseInt(line.substring(88, 92));
             } else {
                     airTemperature = Integer.parseInt(line.substring(87, 92));
             }
             String quality = line.substring(92, 93);
             if (airTemperature != MISSING && quality.matches("[01459]")) {
                     context.write(new Text(data), new IntWritable(airTemperature));
             }
     }
}

3、MaxTemperatureReducer

import java.io.IOException; 
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Reducer; 

public class MaxTemperatureReducer extends Reducer {        

	 @Override
     public void reduce(Text key, Iterable values, Context context)
                     throws IOException, InterruptedException {
             int maxValue = Integer.MIN_VALUE;
             for (IntWritable value : values) {
                     maxValue = Math.max(maxValue, value.get());
             }
             context.write(key, new IntWritable(maxValue));
     }
}

2、运行测试 

Run - Run Configurations 

 运行结果：