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apache源
在project内尾部添加
apache http://maven.apache.org
2) 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
org.apache.hadoop hadoop-core 1.2.1 org.apache.hadoop hadoop-common 2.7.2
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:
4.0.0 com.fun hadoop 1.0-SNAPSHOT apache http://maven.apache.org org.apache.hadoop hadoop-core 1.2.1 org.apache.hadoop hadoop-common 2.7.2 maven-dependency-plugin false true ./lib
5. 编写主程序
WordCount.java
/** * Created by jinshilin on 16/12/7. */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 { 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 { private IntWritable result = new IntWritable(); public void reduce(Text key, Iterable 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); }}
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
我的输入文件源如下:
test.segmented:
dfdfadgdgag
aadadsfudflclcckcerfadfdfdfadgdgagfudflclfuckfuckfuckfuckhahaaaa
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WordCount（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
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,结果如下:
aaa 1
aadads 1cckcer 1dfdfadgdgag 2fadf 1fuck 2fuckfuck 1fudflcl 2haha 1
至此,一个简单的hadoop程序完成!