hadoop之 mapreduce example（1）

环境：
jdk: 1.8
hadoop: 2.6.4

mapper:

package com.hadoop.mapreduce;

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

import java.io.IOException;

/**
 * Created by madong on 2016/05/22.
 */
public class MaxTemperatureMapper extends Mapper<LongWritable,Text,Text,IntWritable>{
    private static final int MISSING = 9999;

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

        System.out.println("mapper input："+ key + "  "+ value);
        String line = value.toString();
        String year = line.substring(15,19);
        int airTemperature;
        if (line.charAt(87) == '+'){
            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(year), new IntWritable(airTemperature));
        }

    }
}

reducer:

package com.hadoop.mapreduce;

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

import java.io.IOException;

/**
 * Created by madong on 2016/05/22.
 */
public class MaxTemperatureReducer extends Reducer<Text,IntWritable,Text,IntWritable> {

    @Override
    protected void reduce(Text key, Iterable<IntWritable> 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));
    }
}

job:

package com.hadoop.mapreduce;

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

/**
 * Created by madong on 2016/05/22.
 */
public class MaxTemperatureJob {

    private final static String INPUT_PATH = "hdfs://lenovo:9000/hadoop/temp";
    private final static String OUT_PUTH = "hdfs://lenovo:9000/hadoop/out";

    public static void main(String[] args) {


        try {
            //远程连接 配置 如果不是windows远程连接可以不用配置Configuration
            Configuration configuration = new Configuration();
            configuration.set("fs.defaultFS", "hdfs://lenovo:9000");
            configuration.set("mapreduce.framework.name", "yarn");
            configuration.set("yarn.resourcemanager.address", "lenovo:8032");
            configuration.set("yarn.resourcemanager.scheduler.address", "lenovo:8030");
            configuration.set("mapred.jar", "D:\\tool\\IdeaProjects\\hadoop\\out\\artifacts\\hadoop_jar\\hadoop.jar");

            Job job = Job.getInstance(configuration);

            job.setJarByClass(MaxTemperatureJob.class);
            job.setJobName("Max temperature");

            FileInputFormat.addInputPath(job,new Path(INPUT_PATH));
            FileOutputFormat.setOutputPath(job,new Path(OUT_PUTH));

            job.setMapperClass(MaxTemperatureMapper.class);
            job.setReducerClass(MaxTemperatureReducer.class);

            job.setOutputKeyClass(Text.class);
            job.setOutputValueClass(IntWritable.class);

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

        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}