HDFS 中读取数据的步骤

HDFS 中读取数据的方法

方法之一： 通过URL

 

 

import java.io.BufferedReader;

import java.io.IOException;

import java.io.InputStream;

import java.io.InputStreamReader;

import java.net.MalformedURLException;

import java.net.URL;

 

import org.apache.hadoop.fs.FsUrlStreamHandlerFactory;

import org.apache.hadoop.io.IOUtils;

 

public class Test {

static {

URL.setURLStreamHandlerFactory(new FsUrlStreamHandlerFactory());

}

/**

* @param args

*/

public static void main(String[] args) {

InputStream in = null;

try {

in = new URL("hdfs://192.168.1.150:9000/tmp/output/part-r-00000").openStream();

BufferedReader reader = new BufferedReader(new InputStreamReader(in));

String line = null;

while( (line = reader.readLine()) != null){

System.out.println(line);

}

} catch (MalformedURLException e) {

// TODO Auto-generated catch block

e.printStackTrace();

} catch (IOException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}finally{

IOUtils.closeStream(in);

}

}

}

 

方法二： 通过FileSytem 方式

 

 

 

import java.io.IOException;

import java.io.InputStream;

import java.net.URI;

 

import org.apache.hadoop.conf.Configuration;

import org.apache.hadoop.fs.FileSystem;

import org.apache.hadoop.fs.Path;

import org.apache.hadoop.io.IOUtils;

 

public class FileSytemCat {

 

/**

* @param args

* @throws IOException 

*/

public static void main(String[] args) throws IOException {

// TODO Auto-generated method stub

Configuration conf = new Configuration();

String uri = "hdfs://192.168.1.150:9000/tmp/output/part-r-00000";

FileSystem fs = FileSystem.get(URI.create(uri), conf);

InputStream in = null;

in = fs.open(new Path(uri));

IOUtils.copyBytes(in, System.out,4096, false);

IOUtils.closeStream(in);

}

}