使用java API操作hdfs--拷贝部分文件到本地

要求：和前一篇的要求正好相反。。

 

在HDFS中生成一个130KB的文件：

代码如下：

 

import java.io.IOException;

import org.apache.hadoop.conf.Configuration;

import java.net.URI;

import org.apache.hadoop.fs.FileSystem;

import java.io.OutputStream;

import org.apache.hadoop.fs.Path;

public class ShenChenHDFS {

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

                // TODO Auto-generated method stub

                String uri = args[0];

                Configuration conf = new Configuration();

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

                OutputStream os=fs.create(new Path(uri));

                byte[] bytes=new byte[130];

                for (int i = 0; i < bytes.length; i++) {

                        bytes[i]=(byte) i;

                }

                os.write(bytes);

        }

}

 

 

运行的结果：

 

代码如下：

 

import java.io.File;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.InputStream;

import org.apache.hadoop.io.IOUtils;

import org.apache.hadoop.fs.Path;

import java.net.URI;

import org.apache.hadoop.fs.FileSystem;

import org.apache.hadoop.conf.Configuration;

public class CopyHDFSToLocal {

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

                String uri = args[0];

                Configuration conf = new Configuration();

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

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

                File file=new File("/home/weiguohui/shengcheng_hdfs_to_local.txt");

                FileOutputStream fos=new FileOutputStream(file);

                byte[] bytes=new byte[1024];

                int offset=100;

                int len=20;

                int numberRead=0;

                while((numberRead=in.read(bytes))!=-1){

                        fos.write(bytes, 100, 20);

           }

                IOUtils.closeStream(in);

                IOUtils.closeStream(fos);

        }

}