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();
         }
     }
 }