Windows+Idea安装Hadoop开发环境

前言:这种问题,本来不应该写篇博客的,但是实在是折磨我太久了,现在终于修好了,必须记一下,否则对不起自己的时间,对自己的博客道歉


简介

环境:Windows 10+JDK1.8+Intellij Idea,无需手动安装Hadoop

Maven

Maven是项目管理及自动构建工具,由Apache软件基金会所提供。基于项目对象模型(缩写:POM)概念,Maven利用一个pom.xml的文件管理一个项目的构建、报告和文档等步骤。只需要在Maven配置文件中指定Hadoop依赖包名字和版本号,Maven就能自动搞定这些依赖。

Intellij Idea

之所以写这篇博客,就是因为我从Eclipse切换到了Idea产生了很多问题。之前使用Eclipse+Hadoop伪分布式,但是用起来有些不顺手。

WordCount

1.新建项目

2.使用Maven配置Hadoop依赖
完成以上步骤,如果正常将会出现: 箭头所指,即是用来Maven的pom.xml文件,在该文件上填写好依赖,填写好的xml文件为:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.cmn</groupId>
    <artifactId>test</artifactId>
    <version>1.0-SNAPSHOT</version>

    <repositories>
        <repository>
            <id>apache</id>
            <url>http://maven.apache.org</url>
        </repository>
    </repositories>

    <dependencies>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>

        <dependency>
            <groupId>org.apache.hadoop</groupId>
            <artifactId>hadoop-common</artifactId>
            <version>2.6.1</version>
        </dependency>
        <dependency>
            <groupId>org.apache.hadoop</groupId>
            <artifactId>hadoop-hdfs</artifactId>
            <version>2.6.1</version>
        </dependency>
        <dependency>
            <groupId>commons-cli</groupId>
            <artifactId>commons-cli</artifactId>
            <version>1.2</version>
        </dependency>
        <dependency>
            <groupId>org.apache.hadoop</groupId>
            <artifactId>hadoop-mapreduce-client-core</artifactId>
            <version>2.6.1</version>
        </dependency>
        <dependency>
            <groupId>org.apache.hadoop</groupId>
            <artifactId>hadoop-mapreduce-client-jobclient</artifactId>
            <version>2.6.1</version>
        </dependency>
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>
        <dependency>
            <groupId>org.apache.hadoop</groupId>
            <artifactId>hadoop-mapreduce-examples</artifactId>
            <version>2.6.1</version>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.16.6</version>
        </dependency>
        <dependency>
            <groupId>org.apache.zookeeper</groupId>
            <artifactId>zookeeper</artifactId>
            <version>3.4.8</version>
        </dependency>
    </dependencies>

</project>

分别添加了<repositories></repositories><dependencies></dependencies>,Idea会询问是否导入变更,选择Import Changes 3.展开项目目录,src->main->java,在该目录下新建java class,命名为WordCount,WordCount.java文件内容如下:

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> {

        private final static IntWritable one = new IntWritable(1);
        private Text word = new Text();

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

    public static class IntSumReducer
            extends Reducer<Text, IntWritable, Text, IntWritable> {
        private IntWritable result = new IntWritable();

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

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

4.输入代码后,在src目录的同级新建一个Dirctory,命名为input,在里面新建一个文本文件,命名随意,内容随意。完成后目录类似如下:
5.选择File->Project Structure,在右侧的Project Setting中选择Modules,选择Language Level为8 - Lambdas...,如下:
6.选择Run->Run/Debug Configurations->左上角绿色加号->Application,Name填WordCount,MainClass选择WordCount,Program填input/ output/,类似:
7.运行,Run->Run WordCount,等待几秒,结果会出现在output目录下。

可能出现的错误

解决方法:重启你的Idea