Class to do useful things on the FTP server.

FtpUtils.java

package com.package.utils;

/*
 * This code is free software; you can redistribute it and/or modify it under
 * the terms of the GNU Lesser General Public License as published by the Free
 * Software Foundation; either version 2.1 of the License, or (at your option)
 * any later version.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT ANY
 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
 * A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
 * details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program; if not, write to the Free Software Foundation, Inc.,
 * 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

import java.io.File;
import java.io.FileOutputStream;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.ArrayList;
import java.util.List;

import org.apache.commons.net.ftp.FTP;
import org.apache.commons.net.ftp.FTPClient;
import org.apache.commons.net.ftp.FTPFile;
import org.apache.commons.net.ftp.FTPReply;

/**
 * Class to do useful things on the FTP server. V. 0.1
 * 
 * <blockquote>
 * Dependency: <a href="http://commons.apache.org/net/">commons-net 3.1</a>
 * </blockquote>
 * 
 * @author <a href="mailto:paulohenriqueas13@gmail.com">Paulo H3nrique Alves</a>
 */
public class FtpUtils {

	private static void downloadNewFilesFromFtpDirectory(String host, String username, String password, String remoteFolder, List<String> existentFiles, String localStoreFolder) {
		FTPClient ftpClient = new FTPClient();
		InetAddress hostAddr = null;

		try {
			hostAddr = InetAddress.getByName(host);
		} catch (UnknownHostException err) {
			System.err.println("Host inválido.");
			System.exit(1);
		} catch (Exception err) {
			System.err.println("Erro genérico :: " + err.getMessage());
			System.exit(1);
		}

		try {
			int hostReply;
			ftpClient.connect(hostAddr);
			System.out.print(ftpClient.getReplyString());
			hostReply = ftpClient.getReplyCode();

			if (!FTPReply.isPositiveCompletion(hostReply)) {
				ftpClient.disconnect();
				System.err.println("Servidor FTP recusando conexões.");
				System.exit(1);
			}
			if (ftpClient.login(username, password)) {

				System.out.print(ftpClient.getReplyString());

				ftpClient.setFileType(FTP.BINARY_FILE_TYPE);
				System.out.print(ftpClient.getReplyString());

				ftpClient.enterLocalPassiveMode();

				if (ftpClient.changeWorkingDirectory(remoteFolder)) {
					System.out.print(ftpClient.getReplyString());

					System.out.println("Listando arquivos do diretório.");
					FTPFile[] files = ftpClient.listFiles();
					System.out.print(ftpClient.getReplyString());

					List<String> filesToDownload = new ArrayList<String>();
					for (FTPFile ftpFile : files) {
						if (ftpFile.isFile()) {
							boolean download = true;
							for (String existentFile : existentFiles) {
								if (ftpFile.getName().equals(existentFile)) {
									download = false;
								}
							}
							if (download) {
								filesToDownload.add(ftpFile.getName());
							}
						}
					}

					for (String filename : filesToDownload) {
						String filenameDownload = localStoreFolder + File.separator + filename;
						File downloadFile = new File(filenameDownload);
						FileOutputStream fileOutputStream = null;
						try {
							fileOutputStream = new FileOutputStream(downloadFile);
						} catch (Exception err) {
							System.out.println("Diretório local não existe :: " + localStoreFolder);
							System.exit(1);
						}
						System.out.println("Baixando arquivo :: " + filename);
						ftpClient.retrieveFile(filename, fileOutputStream);
						System.out.print(ftpClient.getReplyString());
					}
				} else {
					System.out.println("Diretório não existe :: " + remoteFolder);
				}
				ftpClient.logout();
				System.out.print(ftpClient.getReplyString());
			}
		} catch (Exception err) {
			err.printStackTrace();
		} finally {
			if (ftpClient.isConnected()) {
				try {
					ftpClient.disconnect();
					System.out.println("Desconectado do servidor :: " + hostAddr);
				} catch (Exception err) {

				}
			}
		}
	}

	public static void main(String[] args) {
		List<String> existentFiles = new ArrayList<String>();
		existentFiles.add("arquivo1.txt");
		existentFiles.add("arquivo2.txt");
		existentFiles.add("arquivo3.txt");
		
		FtpUtils.downloadNewFilesFromFtpDirectory("www.site.com.br", "username", "password", "/www", existentFiles, "/home/user/Desktop"); // Linux
//		FtpUtils.downloadNewFilesFromFtpDirectory("www.site.com.br", "username", "password", "/www", existentFiles, "c:\temp"); // Windows
	}
}