IDEA调试本地Hadoop程序

1、新建IntelliJ下的maven项目

点击File->New->Project，在弹出的对话框中选择Maven，JDK选择你自己安装的版本，点击Next

2、填写Maven的GroupId和ArtifactId

你可以根据自己的项目随便填，点击Next

这样就新建好了一个空的项目

这里程序名填写WordCount,我们的程序是一个通用的网上的范例,用来计算文件中单词出现的次数

3、设置程序的编译版本

打开Intellij的Preference偏好设置，定位到Build, Execution, Deployment->Compiler->Java Compiler，

将WordCount的Target bytecode version修改为你的jdk版本(我的是1.8)

4、配置依赖

编辑pom.xml进行配置

1) 添加hadoop依赖

这里只需要用到基础依赖hadoop-core和hadoop-common；如果需要读写HDFS，
则还需要依赖hadoop-hdfs和hadoop-client；如果需要读写HBase，则还需要依赖hbase-client

在project内尾部添加

<dependencies>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>
        <dependency>
            <groupId>org.apache.hadoop</groupId>
            <artifactId>hadoop-client</artifactId>
            <version>2.7.3</version>
        </dependency>
        <dependency>
            <groupId>org.apache.hadoop</groupId>
            <artifactId>hadoop-common</artifactId>
            <version>2.7.3</version>
        </dependency>
        <dependency>
            <groupId>org.apache.hadoop</groupId>
            <artifactId>hadoop-hdfs</artifactId>
            <version>2.7.3</version>
        </dependency>
    </dependencies>

修改pom.xml完成后，Intellij右上角会提示Maven projects need to be Imported，点击Import Changes以更新依赖,或者点击Enable Auto Import

最后,我的完整的pom.xml如下:

<?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>me.jinkun</groupId>
    <artifactId>mapreducer</artifactId>
    <version>1.0-SNAPSHOT</version>
    <dependencies>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>
        <dependency>
            <groupId>org.apache.hadoop</groupId>
            <artifactId>hadoop-client</artifactId>
            <version>2.7.3</version>
        </dependency>
        <dependency>
            <groupId>org.apache.hadoop</groupId>
            <artifactId>hadoop-common</artifactId>
            <version>2.7.3</version>
        </dependency>
        <dependency>
            <groupId>org.apache.hadoop</groupId>
            <artifactId>hadoop-hdfs</artifactId>
            <version>2.7.3</version>
        </dependency>
    </dependencies>

</project>

5、编写主程序

RunJob.java

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
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.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;

public class RunJob {
    public static void main(String[] args) throws Exception {
        //System.setProperty("hadoop.home.dir", "D:\\software\\hadoop-2.7.3");
        Configuration config = new Configuration();
        //设置hdfs的通讯地址
        config.set("fs.defaultFS", "hdfs://localhost:9000");
        //设置RN的主机
        config.set("yarn.resourcemanager.hostname", "localhost");

        try {
            FileSystem fs = FileSystem.get(config);

            Job job = Job.getInstance(config);
            job.setJarByClass(RunJob.class);

            job.setJobName("wc");

            job.setMapperClass(WcMapper.class);
            job.setReducerClass(WcReducer.class);

            job.setMapOutputKeyClass(Text.class);
            job.setMapOutputValueClass(IntWritable.class);

            FileInputFormat.addInputPath(job, new Path("file:/D:/software/hadoop-2.7.3/tmp/input/LICENSE.txt"));

            Path outpath = new Path("output");
            if (fs.exists(outpath)) {
                fs.delete(outpath, true);
            }
            FileOutputFormat.setOutputPath(job, outpath);

            boolean f = job.waitForCompletion(true);
            if (f) {
                System.out.println("job任务执行成功");
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

map程序WcMapper.java

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 org.apache.hadoop.util.StringUtils;

import java.io.IOException;

public class WcMapper extends Mapper<LongWritable, Text, Text, IntWritable> {
    @Override
    protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
        String[] words = StringUtils.split(value.toString(), ' ');
        for (String w : words) {
            context.write(new Text(w), new IntWritable(1));
        }
    }
}

Reduce程序WcReducer.java

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

import java.io.IOException;

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

6、配置输入和输出结果文件夹

1) 添加和src目录同级的input文件夹到项目中

在input文件夹中放置一个或多个输入文件源

我的输入文件源是定义的磁盘文件file:/D:/software/hadoop-2.7.3/tmp/input/LICENSE.txt

2) 配置运行参数
在Intellij菜单栏中选择Run->Edit Configurations，在弹出来的对话框中点击+，新建一个Application配置。配置Main class为RunJob（可以点击右边的…选择），

Program arguments为input/ output/，即输入路径为刚才创建的input文件夹，输出为output

我的设定的是如下方式，即存储在hdfs中

Path outpath = new Path("output");
FileOutputFormat.setOutputPath(job, outpath);

由于Hadoop的设定，下次运行时务必删除output文件夹！

好了,运行程序，至此,一个简单的hadoop程序完成!

常见问题：
1、Failed to locate the winutils binary in the hadoop binary path

windows上运行程序需要winutils.exe支持，否则会报错，自己百度下载一个，将winutils.exe和libwinutils.lib放在Hadoop的bin下，并将Hadoop.dll放入系统的C:\Windows\System32中

并且添加HADOOP_HOME和path环境变量

2、文件权限问题
修改hdfs-site.xml，添加入下配置

<property>   
        <name>dfs.permissions</name>   
        <value>false</value>   
</property>

3、运行日志输出

在src统计目录添加log4j.properties

log4j.appender.console=org.apache.log4j.ConsoleAppender
log4j.appender.console.Target=System.out
log4j.appender.console.layout=org.apache.log4j.PatternLayout
log4j.appender.console.layout.ConversionPattern=%d{ABSOLUTE} %5p %c{1}:%L - %m%n
log4j.rootLogger=INFO, console