创建MapReduce程序，并在hadoop集群中运行_hadoop中创建mapreduce

关键词： MapReduce, hadoop 2.6.0, intellij IDEA, Maven

1、在intellij IDEA下创建maven项目

2、引入hadoop相关jar包

    <properties>

        <hadoop.version>2.6.0</hadoop.version>

    </properties>

    <dependencies>

        <dependency>

            <groupId>org.apache.hadoop</groupId>

            <artifactId>hadoop-common</artifactId>

            <version>${hadoop.version}</version>

        </dependency>

        <dependency>

            <groupId>org.apache.hadoop</groupId>

            <artifactId>hadoop-mapreduce-client-core</artifactId>

            <version>${hadoop.version}</version>

        </dependency>

        <dependency>

            <groupId>org.apache.hadoop</groupId>

            <artifactId>hadoop-mapreduce-client-common</artifactId>

            <version>${hadoop.version}</version>

        </dependency>

        <dependency>

            <groupId>org.apache.hadoop</groupId>

            <artifactId>hadoop-mapreduce-client-jobclient</artifactId>

            <version>${hadoop.version}</version>

        </dependency>

    </dependencies>

3、创建MapReduce程序（程序的思想copy来的）

package cn.edu.kmust.cti;

import org.apache.hadoop.conf.Configuration;

import org.apache.hadoop.fs.Path;

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;

import java.io.IOException;

/**

 * @author wei.feng@corp.elong.com

 * @since 15-3-27

 */

public class Dedup {

    public static class Map extends Mapper {

        private static Text line = new Text();

        @Override

        protected void map(Object key, Text value, Context context)

                throws IOException, InterruptedException {

            //super.map(key, value, context);

            line = value;

            context.write(line, new Text(""));

        }

    }

    public static class Reduce extends Reducer {

        @Override

        protected void reduce(Text key, Iterable values, Context context)

                throws IOException, InterruptedException {

            context.write(key, new Text(""));

        }

    }

    public static void main(String[] args) throws Exception {

        Configuration conf = new Configuration();

        conf.set("mapred.job.tracker", "10.211.55.6:9001");

        Job job = Job.getInstance(conf, "Data Deduplication");

        job.setJarByClass(Dedup.class);

        job.setMapperClass(Map.class);

        job.setCombinerClass(Reduce.class);

        job.setReducerClass(Reduce.class);

        job.setOutputKeyClass(Text.class);

        job.setOutputValueClass(Text.class);

        FileInputFormat.addInputPath(job,

                new Path("hdfs://hadoop1:9000/dedup_in"));

        FileOutputFormat.setOutputPath(job,

                new Path("hdfs://hadoop1:9000/dedup_out"));

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

    }

}

说明：

10.211.55.6    hadoop集群namenode的ip地址

dedup_in    hadoop文件夹名称，MapReduce的输入路径

dedup_out    hadoop文件夹名称，MapReduce的输出路径

4、打jar包

参考：http://bglmmz.iteye.com/blog/2058785

a、不能通过mvn package打包，原因：打入不了所依赖的第三方jar包等

intellij IDEA -> File -> Project Structure

-> OK

b、intellij IDEA -> Build -> Build Artifacts

-> Build / Rebuild

5、将程序传输到hadoop集群的namenode上

scp ./out/artifacts/HadoopDemo_jar/* root@10.211.55.6:/home/user/hadoop/dedup/

查看linux服务器

说明：

file1和file2为程序用到的数据文件，一会儿将上传到hadoop集群中

6、准备程序使用的数据

在hadoop集群的namenode节点，创建文件夹、上传文件

hadoop fs -mkdir /dedup_in

hadoop fs -mkdir /dedup_out

hadoop fs -put /home/user/hadoop/file1 /dedup_in/

hadoop fs -put /home/user/hadoop/file2 /dedup_in/

查看

7、运行程序

hadoop jar ./dedup/HadoopDemo.jar /dedup_in /dedup_out

执行过程

8、查看计算结果