IntelliJ IDEA + Maven环境编写第一个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apache源 在project内尾部添加 <repositories> <repository> <id>apache</id> <url>http://maven.apache.org</url> </repository> </repositories> 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 <dependencies> <dependency> <groupId>org.apache.hadoop</groupId> <artifactId>hadoop-core</artifactId> <version>1.2.1</version> </dependency> <dependency> <groupId>org.apache.hadoop</groupId> <artifactId>hadoop-common</artifactId> <version>2.7.2</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>com.fun</groupId> <artifactId>hadoop</artifactId> <version>1.0-SNAPSHOT</version> <repositories> <repository> <id>apache</id> <url>http://maven.apache.org</url> </repository> </repositories> <dependencies> <dependency> <groupId>org.apache.hadoop</groupId> <artifactId>hadoop-core</artifactId> <version>1.2.1</version> </dependency> <dependency> <groupId>org.apache.hadoop</groupId> <artifactId>hadoop-common</artifactId> <version>2.7.2</version> </dependency> </dependencies> <build> <plugins> <plugin> <artifactId>maven-dependency-plugin</artifactId> <configuration> <excludeTransitive>false</excludeTransitive> <stripVersion>true</stripVersion> <outputDirectory>./lib</outputDirectory> </configuration> </plugin> </plugins> </build> </project> 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<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); } } 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: dfdfadgdgagaadadsfudflclcckcerfadfdfdfadgdgagfudflclfuckfuckfuckfuckhahaaaa 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 1aadads 1cckcer 1dfdfadgdgag 2fadf 1fuck 2fuckfuck 1fudflcl 2haha 1 至此,一个简单的hadoop程序完成!
