eclipse怎样使用maven连接hadoop集群

2025-03-28 08:25:33

推荐回答（1个）

回答1：

关于Maven的使用就不再啰嗦了，网上很多，并且这么多年变化也不大，这里仅介绍怎么搭建Hadoop的开发环境。

1. 首先创建工程

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mvn archetype:generate -DgroupId=my.hadoopstudy -DartifactId=hadoopstudy -DarchetypeArtifactId=maven-archetype-quickstart -DinteractiveMode=false

2. 然后在pom.xml文件里添加hadoop的依赖包hadoop-common, hadoop-client, hadoop-hdfs，添加后的pom.xml文件如下

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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
4.0.0
my.hadoopstudy
hadoopstudy
jar
1.0-SNAPSHOT
hadoopstudy
http://maven.apache.org
org.apache.hadoop
hadoop-common
2.5.1
org.apache.hadoop
hadoop-hdfs
2.5.1
org.apache.hadoop
hadoop-client
2.5.1
junit
junit
3.8.1
test

3. 测试

3.1 首先我们可以测试一下hdfs的开发，这里假定使用上一篇Hadoop文章中的hadoop集群，类代码如下

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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);
}
}

3.2 测试MapReduce作业

测试代码比较简单，如下：

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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{
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 {
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();
String[] otherArgs = new GenericOptionsParser(conf, args).getRemainingArgs();
if (otherArgs.length < 2) {
System.err.println("Usage: EventCount ");
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);
}
}