使用Maven搭建Hadoop开发环境

<project xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://maven.apache.org/POM/4.0.0"  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>my.hadoopstudy</groupId> <artifactId>hadoopstudy</artifactId> <packaging>jar</packaging> <version>1.0-SNAPSHOT</version> <name>hadoopstudy</name> <url>http://maven.apache.org</url> <dependencies> <dependency>  <groupId>org.apache.hadoop</groupId>  <artifactId>hadoop-common</artifactId>  <version>2.5.1</version> </dependency> <dependency>  <groupId>org.apache.hadoop</groupId>  <artifactId>hadoop-hdfs</artifactId>  <version>2.5.1</version> </dependency> <dependency>  <groupId>org.apache.hadoop</groupId>  <artifactId>hadoop-client</artifactId>  <version>2.5.1</version> </dependency> <dependency>  <groupId>junit</groupId>  <artifactId>junit</artifactId>  <version>3.8.1</version>  <scope>test</scope> </dependency> </dependencies></project>

package my.hadoopstudy.dfs;import org.apache.hadoop.conf.Configuration;import org.apache.hadoop.fs.FSDataOutputStream;import org.apache.hadoop.fs.FileStatus;import org.apache.hadoop.fs.FileSystem;import org.apache.hadoop.fs.Path;import org.apache.hadoop.io.IOUtils;import java.io.InputStream;import java.net.URI;public class Test { public static void main(String[] args) throws Exception { String uri = "hdfs://9.111.254.189:9000/"; Configuration config = new Configuration(); FileSystem fs = FileSystem.get(URI.create(uri), config); // 列出hdfs上/user/fkong/目录下的所有文件和目录 FileStatus[] statuses = fs.listStatus(new Path("/user/fkong")); for (FileStatus status : statuses) {  System.out.println(status); } // 在hdfs的/user/fkong目录下创建一个文件，并写入一行文本 FSDataOutputStream os = fs.create(new Path("/user/fkong/test.log")); os.write("Hello World!".getBytes()); os.flush(); os.close(); // 显示在hdfs的/user/fkong下指定文件的内容 InputStream is = fs.open(new Path("/user/fkong/test.log")); IOUtils.copyBytes(is, System.out, 1024, true); }}

package my.hadoopstudy.mapreduce;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;import org.apache.hadoop.util.GenericOptionsParser;import java.io.IOException;public class EventCount { public static class MyMapper extends Mapper<Object, Text, Text, IntWritable>{ private final static IntWritable one = new IntWritable(1); private Text event = new Text(); public void map(Object key, Text value, Context context) throws IOException, InterruptedException {  int idx = value.toString().indexOf(" ");  if (idx > 0) {  String e = value.toString().substring(0, idx);  event.set(e);  context.write(event, one);  } } } public static class MyReducer 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(); String[] otherArgs = new GenericOptionsParser(conf, args).getRemainingArgs(); if (otherArgs.length < 2) {  System.err.println("Usage: EventCount <in> <out>");  System.exit(2); } Job job = Job.getInstance(conf, "event count"); job.setJarByClass(EventCount.class); job.setMapperClass(MyMapper.class); job.setCombinerClass(MyReducer.class); job.setReducerClass(MyReducer.class); job.setOutputKeyClass(Text.class); job.setOutputValueClass(IntWritable.class); FileInputFormat.addInputPath(job, new Path(otherArgs[0])); FileOutputFormat.setOutputPath(job, new Path(otherArgs[1])); System.exit(job.waitForCompletion(true) ? 0 : 1); }}