用流的方式来操作hdfs上的文件

 

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.net.URI;

import org.apache.commons.io.IOUtils;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FSDataOutputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.junit.Before;
import org.junit.Test;


/**
 * 用流的方式来操作hdfs上的文件
 * 可以实现读取指定偏移量范围的数据
 * @author
 *
 */
public class HdfsStreamAccess {
    
    FileSystem fs = null;
    Configuration conf = null;
    
    @Before
    public void init() throws Exception{
        
        conf = new Configuration();
        //拿到一个文件系统操作的客户端实例对象
//        fs = FileSystem.get(conf);
        //可以直接传入 uri和用户身份
        fs = FileSystem.get(new URI("hdfs://node2:8020"),conf,"root");
    }
    

    /**
     * 通过流的方式上传文件到hdfs
     * @throws Exception
     */
    @Test
    public void testUpload() throws Exception {
        
        FSDataOutputStream outputStream = fs.create(new Path("/aaa"), true);
        FileInputStream inputStream = new FileInputStream("d:/bbb");
        
        IOUtils.copy(inputStream, outputStream);
        
    }
    
    
    /**
     * 通过流的方式获取hdfs上数据
     * @throws Exception
     */
    @Test
    public void testDownLoad() throws Exception {
        
        FSDataInputStream inputStream = fs.open(new Path("/aaa"));        
        
        FileOutputStream outputStream = new FileOutputStream("d:/ccc");
        
        IOUtils.copy(inputStream, outputStream);
        
    }
    
    
    @Test
    public void testRandomAccess() throws Exception{
        
        FSDataInputStream inputStream = fs.open(new Path("/aaa"));
    
        inputStream.seek(12);
        
        FileOutputStream outputStream = new FileOutputStream("d:/ddd");
        
        IOUtils.copy(inputStream, outputStream);
        
        
    }
    
    
    
    /**
     * 显示hdfs上文件的内容
     * @throws IOException 
     * @throws IllegalArgumentException 
     */
    @Test
    public void testCat() throws IllegalArgumentException, IOException{
        
        FSDataInputStream in = fs.open(new Path("/aaa"));
        
        IOUtils.copy(in, System.out);
        
//        IOUtils.copyBytes(in, System.out, 1024);
    }
    
}