云计算——实验一 HDFS与MAPREDUCE操作

1、虚拟机集群搭建部署hadoop

利用VMware、centOS-7、Xshell(secureCrt)等软件搭建集群部署hadoop

远程连接工具使用Xshell：

HDFS文件操作

2.1 HDFS接口编程

调用HDFS文件接口实现对分布式文件系统中文件的访问，如创建、修改、删除等

三、MAPREDUCE并行程序开发

求每年最高气温

本实验是编写完成相关代码后，将该项目打包成jar包，上传至centos后利用hadoop命令进行运行。

import java.io.IOException;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
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.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
public class Temperature {
    /**
     * 四个泛型类型分别代表：
     * KeyIn        Mapper的输入数据的Key，这里是每行文字的起始位置（0,11,...）
     * ValueIn      Mapper的输入数据的Value，这里是每行文字
     * KeyOut       Mapper的输出数据的Key，这里是每行文字中的“年份”
     * ValueOut     Mapper的输出数据的Value，这里是每行文字中的“气温”
     */
    static class TempMapper extends
            Mapper<LongWritable, Text, Text, IntWritable> {
        @Override
        public void map(LongWritable key, Text value, Context context)
                throws IOException, InterruptedException {
            // 打印样本: Before Mapper: 0, 2000010115
            System.out.print("Before Mapper: " + key + ", " + value);
            String line = value.toString();
            String year = line.substring(0, 4);
            int temperature = Integer.parseInt(line.substring(8));
            context.write(new Text(year), new IntWritable(temperature));
            // 打印样本: After Mapper:2000, 15
            System.out.println(
                    "======" +
                    "After Mapper:" + new Text(year) + ", " + new IntWritable(temperature));
        }
    }

       static class TempReducer extends
            Reducer<Text, IntWritable, Text, IntWritable> {
        @Override
        public void reduce(Text key, Iterable<IntWritable> values,
                Context context) throws IOException, InterruptedException {
            int maxValue = Integer.MIN_VALUE;
            StringBuffer sb = new StringBuffer();
            //取values的最大值
            for (IntWritable value : values) {
                maxValue = Math.max(maxValue, value.get());
                sb.append(value).append(", ");
            }
            // 打印样本： Before Reduce: 2000, 15, 23, 99, 12, 22,
            System.out.print("Before Reduce: " + key + ", " + sb.toString());
            context.write(key, new IntWritable(maxValue));
            // 打印样本： After Reduce: 2000, 99
            System.out.println(
                    "======" +
                    "After Reduce: " + key + ", " + maxValue);
        }
    }

    public static void main(String[] args) throws Exception {
        //输入路径
        String dst = "hdfs://localhost:9000/intput.txt";
        //输出路径，必须是不存在的，空文件加也不行。
        String dstOut = "hdfs://localhost:9000/output";
        Configuration hadoopConfig = new Configuration();

        hadoopConfig.set("fs.hdfs.impl",
            org.apache.hadoop.hdfs.DistributedFileSystem.class.getName()
        );
        hadoopConfig.set("fs.file.impl",
            org.apache.hadoop.fs.LocalFileSystem.class.getName()
        );
        Job job = new Job(hadoopConfig);

        //如果需要打成jar运行，需要下面这句
        job.setJarByClass(NewMaxTemperature.class);

        //job执行作业时输入和输出文件的路径
        FileInputFormat.addInputPath(job, new Path(dst));
        FileOutputFormat.setOutputPath(job, new Path(dstOut));

        //指定自定义的Mapper和Reducer作为两个阶段的任务处理类
        job.setMapperClass(TempMapper.class);
        job.setReducerClass(TempReducer.class);

        //设置最后输出结果的Key和Value的类型
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(IntWritable.class);
        //执行job，直到完成
        job.waitForCompletion(true);
        System.out.println("Finished");
    }
}

词频统计

import java.io.IOException;

import org.apache.commons.lang.StringUtils;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;

public class WordCountMapper extends Mapper<LongWritable, Text, Text, LongWritable>{

    @Override
    protected void map(LongWritable key, Text value, Mapper<LongWritable, Text, Text, LongWritable>.Context context)
            throws IOException, InterruptedException {
        // TODO Auto-generated method stub
        //super.map(key, value, context);
        //String[] words = StringUtils.split(value.toString());
          String[] words = StringUtils.split(value.toString(), " ");
        for(String word:words)
        {
              context.write(new Text(word), new LongWritable(1));

        }
    }
}

reducer：
package cn.edu.bupt.wcy.wordcount;

import java.io.IOException;

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

public class WordCountReducer extends Reducer<Text, LongWritable, Text, LongWritable> {

    @Override
    protected void reduce(Text arg0, Iterable<LongWritable> arg1,
            Reducer<Text, LongWritable, Text, LongWritable>.Context context) throws IOException, InterruptedException {
        // TODO Auto-generated method stub
        //super.reduce(arg0, arg1, arg2);
        int sum=0;
        for(LongWritable num:arg1)
        {
            sum += num.get();

        }
        context.write(arg0,new LongWritable(sum));

    }
}

runner：
package cn.edu.bupt.wcy.wordcount;

import java.io.IOException;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;

import org.apache.hadoop.io.LongWritable;
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.input.TextInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;

public class WordCountRunner {

    public static void main(String[] args) throws IllegalArgumentException, IOException, ClassNotFoundException, InterruptedException {
        Configuration conf = new Configuration();
        Job job = new Job(conf);
        job.setJarByClass(WordCountRunner.class);
        job.setJobName("wordcount");
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(LongWritable.class);
        job.setMapperClass(WordCountMapper.class);
        job.setReducerClass(WordCountReducer.class);
        job.setInputFormatClass(TextInputFormat.class);
        job.setOutputFormatClass(TextOutputFormat.class);
        FileInputFormat.addInputPath(job, new Path(args[1]));
        FileOutputFormat.setOutputPath(job, new Path(args[2]));
        job.waitForCompletion(true);
    }

}