Hadoop 2.7.x에서 사용할 수 있는 파일/디렉토리 관련 utils

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

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;

public class HDFSUtils {
	/**
	   * create a existing file from local filesystem to hdfs
	   * @param source
	   * @param dest
	   * @param conf
	   * @throws IOException
	   */
	  public void addFile(String source, String dest, Configuration conf) throws IOException {

	    FileSystem fileSystem = FileSystem.get(conf);

	    // Get the filename out of the file path
	    String filename = source.substring(source.lastIndexOf('/') + 1,source.length());

	    // Create the destination path including the filename.
	    if (dest.charAt(dest.length() - 1) != '/') {
	      dest = dest + "/" + filename;
	    } else {
	      dest = dest + filename;
	    }

	    // System.out.println("Adding file to " + destination);

	    // Check if the file already exists
	    Path path = new Path(dest);
	    if (fileSystem.exists(path)) {
	      System.out.println("File " + dest + " already exists");
	      return;
	    }

	    // Create a new file and write data to it.
	    FSDataOutputStream out = fileSystem.create(path);
	    InputStream in = new BufferedInputStream(new FileInputStream(new File(
	        source)));

	    byte[] b = new byte[1024];
	    int numBytes = 0;
	    while ((numBytes = in.read(b)) > 0) {
	      out.write(b, 0, numBytes);
	    }

	    // Close all the file descriptors
	    in.close();
	    out.close();
	    fileSystem.close();
	  }

	  /**
	   * read a file from hdfs
	   * @param file
	   * @param conf
	   * @throws IOException
	   */
	  public void readFile(String file, Configuration conf) throws IOException {
	    FileSystem fileSystem = FileSystem.get(conf);

	    Path path = new Path(file);
	    if (!fileSystem.exists(path)) {
	      System.out.println("File " + file + " does not exists");
	      return;
	    }

	    FSDataInputStream in = fileSystem.open(path);

	    String filename = file.substring(file.lastIndexOf('/') + 1,
	        file.length());

	    OutputStream out = new BufferedOutputStream(new FileOutputStream(
	        new File(filename)));

	    byte[] b = new byte[1024];
	    int numBytes = 0;
	    while ((numBytes = in.read(b)) > 0) {
	      out.write(b, 0, numBytes);
	    }

	    in.close();
	    out.close();
	    fileSystem.close();
	  }

	  /**
	   * delete a directory in hdfs
	   * @param file
	   * @throws IOException
	   */
	  public void deleteFile(String file, Configuration conf) throws IOException {
	    FileSystem fileSystem = FileSystem.get(conf);

	    Path path = new Path(file);
	    if (!fileSystem.exists(path)) {
	      System.out.println("File " + file + " does not exists");
	      return;
	    }

	    fileSystem.delete(new Path(file), true);

	    fileSystem.close();
	  }

	  /**
	   * create directory in hdfs
	   * @param dir
	   * @throws IOException
	   */
	  public void mkdir(String dir, Configuration conf) throws IOException {
	    FileSystem fileSystem = FileSystem.get(conf);

	    Path path = new Path(dir);
	    if (fileSystem.exists(path)) {
	      System.out.println("Dir " + dir + " already exists");
	      return;
	    } else {
		    fileSystem.mkdirs(path);
		    fileSystem.close();
	    }
	  }
	  
	  /**
	   * delete directory in hdfs
	   * @param dir
	   * @throws IOException
	   */
	  public void rmdir(String dir, Configuration conf) throws IOException {
	    FileSystem fileSystem = FileSystem.get(conf);

	    Path path = new Path(dir);
	    if (fileSystem.exists(path)) {
		    fileSystem.delete(path, true);
		    fileSystem.close();
	    } else {
		    System.out.println("Dir " + dir + " not exists");
	    }
	  }


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

	    if (args.length < 1) {
	      System.out.println("Usage: hdfsclient add/read/delete/mkdir"
	          + " [<local_path> <hdfs_path>]");
	      System.exit(1);
	    }

	    FileSystemOperations client = new FileSystemOperations();
	    String hdfsPath = "hdfs://" + args[0] + ":" + args[1];

	    Configuration conf = new Configuration();
	    // Providing conf files
	    // conf.addResource(new Path(HDFSAPIDemo.class.getResource("/conf/core-site.xml").getFile()));
	    // conf.addResource(new Path(HDFSAPIDemo.class.getResource("/conf/hdfs-site.xml").getFile()));
	    // (or) using relative paths
	    //    conf.addResource(new Path(
	    //        "/u/hadoop-1.0.2/conf/core-site.xml"));
	    //    conf.addResource(new Path(
	    //        "/u/hadoop-1.0.2/conf/hdfs-site.xml"));

	    //(or)
	    // alternatively provide namenode host and port info
	    conf.set("fs.default.name", hdfsPath);

	    if (args[0].equals("add")) {
	      if (args.length < 3) {
	        System.out.println("Usage: hdfsclient add <local_path> "
	            + "<hdfs_path>");
	        System.exit(1);
	      }

	      client.addFile(args[1], args[2], conf);

	    } else if (args[0].equals("read")) {
	      if (args.length < 2) {
	        System.out.println("Usage: hdfsclient read <hdfs_path>");
	        System.exit(1);
	      }

	      client.readFile(args[1], conf);

	    } else if (args[0].equals("delete")) {
	      if (args.length < 2) {
	        System.out.println("Usage: hdfsclient delete <hdfs_path>");
	        System.exit(1);
	      }

	      client.deleteFile(args[1], conf);

	    } else if (args[0].equals("mkdir")) {
	      if (args.length < 2) {
	        System.out.println("Usage: hdfsclient mkdir <hdfs_path>");
	        System.exit(1);
	      }

	      client.mkdir(args[1], conf);

	    } else {
	      System.out.println("Usage: hdfsclient add/read/delete/mkdir"
	          + " [<local_path> <hdfs_path>]");
	      System.exit(1);
	    }

	    System.out.println("Done!");
	  }
	  */
}