MapReduce本地IDEA操作

一、环境准备

（1）本地搭建hadoop环境

将hadoop相关文件放到目录下如下

配置环境变量

在终端输入hadoop version 如下

（2）搭建maven

conf下setting文件使用国内镜像

    
      nexus-aliyun
      central
      Nexus aliyun
      http://maven.aliyun.com/nexus/content/groups/public
    

  

环境变量

 在终端下输入mvn  -v

二、IDEA编写

 （1）新建一个Maven 工程

 界面如下：

（2）修改配置文件位置

（3）编辑pom.xml 文件  代码如下

    4.0.0

    org.example
    MapReduce
    1.0

    
        3.1.3
    

    
        
            org.apache.hadoop
            hadoop-client
            ${hadoop.version}
        

        
            org.apache.hadoop
            hadoop-common
            ${hadoop.version}
        

        
            org.apache.hadoop
            hadoop-hdfs
            ${hadoop.version}
        
    

 然后点击maven 进行下载 如下

（3）在data下新建一个wc.txt文件  内容如下

（4） 新建MRMapper,java

代码如下：

package MR.wc;
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;

public class MRMapper extends Mapper {
    Text k = new Text();
    IntWritable v = new IntWritable(1);

    @Override
    protected void setup(Context context) throws IOException, InterruptedException {
        System.out.println("Mapper.setup----------");
    }

    @Override
    protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
        // 1 获取一行
        String line = value.toString();

        // 2 切割
        String[] words = line.split(" ");

        // 3 输出
        for (String word : words) {
            k.set(word);
            context.write(k, v);
        }
    }

    @Override
    protected void cleanup(Context context) throws IOException, InterruptedException {
        System.out.println("Mapper.cleanup");
    }
}

（5）新建MRReducer.java

package MR.wc;

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

import java.io.IOException;

public class MRReducer extends Reducer {
    int sum;
    IntWritable v = new IntWritable();

    @Override
    protected void setup(Context context) throws IOException, InterruptedException {
        System.out.println("Mapper.setup__________");
    }

    @Override
    protected void reduce(Text key, Iterable values,Context context) throws IOException, InterruptedException {
        // 1 累加求和
        sum = 0;
        for (IntWritable count : values) {
            sum += count.get();
        }

        // 2 输出
        v.set(sum);
        context.write(key, v);
    }

    @Override
    protected void cleanup(Context context) throws IOException, InterruptedException {
        System.out.println("Mapper.cleanup__________");
    }
}