hadoop 自学指南二之开发环境搭建

一、前言

从一个简单的程序观察hadoop 的运行过程

二、window 下hadoop 的开发环境搭建

环境准备：

hadoop 1.2.1

eclipse Version: Mars Release (4.5.0)

hadoop-eclipse-plugin-1.2.1(网上有许多，不再重复提供）

hadoop-eclipse-plugin-1.2.1放到dropins 启动eclipse

根据自己的情况填写

advanced parameters:这里要改一下

出现

代表成功了

问题ps： 一直有listening.....请检查插件版本与hadoop 版本是否一致

插件安装没有成功,原因可以是eclipse版本过旧，你到官网下载最新的版本

三、hadoop 运行过程

下面是hadoop-example的一个经典程序hello word,是wordCount

package hadoop.v3;

import java.io.IOException;
import java.util.Iterator;
import java.util.StringTokenizer;

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.mapred.FileInputFormat;
import org.apache.hadoop.mapred.FileOutputFormat;
import org.apache.hadoop.mapred.JobClient;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.MapReduceBase;
import org.apache.hadoop.mapred.Mapper;
import org.apache.hadoop.mapred.OutputCollector;
import org.apache.hadoop.mapred.Reducer;
import org.apache.hadoop.mapred.Reporter;
import org.apache.hadoop.mapred.TextInputFormat;
import org.apache.hadoop.mapred.TextOutputFormat;
import org.hai.hdfs.utils.HDFSUtils;

/**
 * hadoop 的 hello word
 * @author : chenhaipeng
 * @date : 2015年9月5日 下午8:38:13
 */
public class WordCount {
	
	//Map 
	public static class Map extends MapReduceBase implements Mapper{
		private final static IntWritable one = new IntWritable(1);
		private Text word = new Text();
		
		public void map(LongWritable key, Text value, OutputCollector output, 
				Reporter reporter) throws IOException{
			String line = value.toString();
			StringTokenizer tokenizer = new StringTokenizer(line);
			while(tokenizer.hasMoreTokens()){
				word.set(tokenizer.nextToken());
				output.collect(word, one);
			}
			
		}
	}
	
	//reduce
	public static class Reduce extends MapReduceBase implements Reducer{
		public void reduce(Text key, Iterator values, 
				OutputCollector output,Reporter reporter)throws IOException{
			int sum = 0; 
			while(values.hasNext()){
				sum += values.next().get();
			}
			output.collect(key, new IntWritable(sum));
		}
	}
	
	public static void deletedir(String path){
		try {
			HDFSUtils.DeleteHDFSFile(path);
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
	
	
	public static void main(String[] args) throws Exception {
		JobConf conf  = new JobConf(WordCount.class);
		conf.setJobName("mywordcount");
		
		conf.setOutputKeyClass(Text.class);
		conf.setOutputValueClass(IntWritable.class);
		
		conf.setMapperClass(Map.class);
		conf.setReducerClass(Reduce.class);
		
		conf.setInputFormat(TextInputFormat.class);
		conf.setOutputFormat(TextOutputFormat.class);
		
		FileInputFormat.setInputPaths(conf, new Path(args[0]));
		deletedir(args[1]);
		FileOutputFormat.setOutputPath(conf, new Path(args[1]));
		
		JobClient.runJob(conf);

	}

}

输入为：

Mary had a little lamb
its fleece very white as snow
and everywhere that Mary went
the lamb was sure to go

查看输出结果如下 ：

进入http://hai:50030/jobtracker.jsp 发现根本就没有运行这个job,但结果有输出，什么鬼？

参巧hadoop 自学指南-hadoop 的各种问题汇总