Hadoop之简单文件读写

 文件简单写操作：

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataOutputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
public class writeFile {
    public static void main(String[] args) {
        try{
            Configuration conf=new Configuration();
            //如果没有把配置文件加入bin文件夹，那么需要加入下面两行
            //conf.set("fs.defaultFS","hdfs://localhost:9000" );
            //conf.set("fs.hdfs.impl", "org.apache.hadoop.hdfs.DistributedFileSystem");
            FileSystem fs =FileSystem.get(conf);
            byte[] buffer="Hello world!".getBytes();
            String Filename="hdfs://localhost:9000/user/hadoop/file5.txt";
 
            FSDataOutputStream os=fs.create(new Path(Filename));
            os.write(buffer,0,buffer.length);
            
            System.out.println("creat "+Filename+" successfully");
            os.close();
            fs.close();
        }
        catch(Exception e){
            e.printStackTrace();
        }
    }
}

文件简单读操作：

import java.io.BufferedReader;
import java.io.InputStreamReader;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;

public class readFile {
    public static void main(String argsp[]){
        try{
            Configuration conf = new Configuration();
            conf.set("fs.defaultFS","hdfs://localhost:9000" );
            conf.set("fs.hdfs.impl", "org.apache.hadoop.hdfs.DistributedFileSystem");
            FileSystem fs = FileSystem.get(conf);
            
            Path file = new Path("hdfs://localhost:9000/user/hadoop/file5.txt");
            
            FSDataInputStream is = fs.open(file);
            
            BufferedReader bd = new BufferedReader(new InputStreamReader(is));
            String content = bd.readLine();
            
            System.out.println(content);
            
            bd.close();
            fs.close();
        }
        catch(Exception e){
            e.printStackTrace();
        }
    }
}