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12.5每日总结8

发布时间 2023-12-05 23:40:21作者: 听着DJ读童话
  1. 编程实现一个类“MyFSDataInputStream”，该类继承“org.apache.hadoop.fs.FSDataInputStream”，要求如下：实现按行读取HDFS中指定文件的方法“readLine()”，如果读到文件末尾，则返回空，否则返回文件一行的文本。

  2. import java.io.BufferedReader;
    import java.io.IOException;
    import java.io.InputStream;
    import java.io.InputStreamReader;

    import org.apache.hadoop.conf.Configuration;
    import org.apache.hadoop.fs.*;

     


    public class MyFSDataInputStream extends FSDataInputStream{

    /**
    * @param args
    */
    public MyFSDataInputStream(InputStream in){
    super(in);
    }
    public static String readline(Configuration conf,String remoteFilePath){
    try (FileSystem fs = FileSystem.get(conf)) {
    Path remotePath = new Path(remoteFilePath);
    FSDataInputStream in = fs.open(remotePath);
    BufferedReader d = new BufferedReader(new InputStreamReader(in));
    String line = null;
    if ((line = d.readLine()) != null) {
    d.close();
    in.close();
    return line;
    }
    return null;
    } catch (IOException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
    return null;
    }

    }

    public static void main(String[] args) {
    // TODO Auto-generated method stub
    Configuration conf=new Configuration();
    conf.set("fs.default.name","hdfs://localhost:9000");
    String remoteFilePath="/Test/text.txt";

    System.out.println("读取文件："+remoteFilePath);
    System.out.println(MyFSDataInputStream.readline(conf, remoteFilePath));
    System.out.println("\n读取完成");
    }

    }