Cloud 学习笔记5.Word Count

Word Count

实验准备

环境：CDH 5.13.0 镜像，虚拟机

VMware版

VirtualBox版

下载对应版本的虚拟机和镜像。如果没有开启VT-d, 需要进入BIOS开启。

导入虚拟机

1. 解压下载好的镜像, 点击ovf文件
2. 最低配置为6GB内存，2CPU
3. 导入镜像，开机。系统的性能此过程可能持续5~30分钟
4. 开机完成会自动打开Firefox浏览器

启动Eclipse

1. 打开eclipse，新建Project, 选择Maven Project
2. 点击Next
3. Group Id和Artifact Id 随意填写，点击Finish，创建项目
4. 在新建的项目中，修改pom.xml
5. 在pom.xml中添加dependency

<dependency>
  <groupId>org.apache.hadoop</groupId>
  <artifactId>hadoop-core</artifactId>
  <version>1.2.1</version>
</dependency>
<dependency>
  <groupId>org.apache.hadoop</groupId>
  <artifactId>hadoop-common</artifactId>
  <version>2.7.2</version>
</dependency>

1. 保存之后Maven将自动引入依赖文件
2. 从src中删除自动生成的App.java文件，新建MapReduce程序

代码

在项目目录下新建input/文件夹，在该文件夹下新建data.txt文件。data.txt写入输入样本，如：

I love big data and hadoop and I love data science

在src/main/java文件夹下，新建WordCount.java

package big.data;
import java.io.IOException;
import java.util.StringTokenizer;

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.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 WordCount {

    public static class TokenizerMapper extends Mapper<Object, Text, Text, IntWritable> {

        public void map(Object key, Text value, Context context)
                throws IOException, InterruptedException {
            StringTokenizer itr = new StringTokenizer(value.toString());
            while (itr.hasMoreTokens()) {
                context.write(new Text(itr.nextToken()), new IntWritable(1));
            }
        }
    }

    public static class IntSumReducer extends Reducer<Text, IntWritable, Text, IntWritable> {
        public void reduce(Text key, Iterable<IntWritable> values, Context context) throws IOException, InterruptedException {
            int sum = 0;
            for (IntWritable val : values) {
                sum += val.get();
            }
            context.write(key, new IntWritable(sum));
        }
    }

    public static void main(String[] args) throws Exception {
        Configuration conf = new Configuration();
        Job job = new Job(conf, "word count");
        job.setJarByClass(WordCount.class);

        job.setMapperClass(TokenizerMapper.class);
        job.setReducerClass(IntSumReducer.class);

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

        FileInputFormat.addInputPath(job, new Path(args[0]));
        FileOutputFormat.setOutputPath(job, new Path(args[1]));
        System.exit(job.waitForCompletion(true) ? 0 : 1);
    }
}

执行

1. 点击Run按钮，修改Configuration，确保Project和Main Class正确
2. 修改Argument, 点击Run
3. 在output路径下查看输出