Java操作ftp,上传,下载,删除操作

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

public class FtpCtrl {
    
    
    public static void main(String[] args) throws Exception {
        
        String url = "ip";
        int port = 21;
        String username = "username";
        String password = "password";
        String path = "/";
        String filename = "ftp.test.tmp";
        FileInputStream fis = new FileInputStream("/home/iamsuperman/ftp.txt");
        uploadFile(url, port, username, password, path, filename, fis);
        
    }

    /**
     * @param ip
     *            FTP服务器IP地址
     * @param port
     *            FTP服务器端口
     * @param username
     *            FTP服务器登录名
     * @param password
     *            FTP服务器密码
     * @param remotePath
     *            远程文件路径
     * @param fileName
     *            待删除的文件名
     * @return
     * @see [类、类#方法、类#成员]
     */
    public static boolean deleteFtpFile(String ip, int port, String username, String password, String remotePath,
            String fileName) {
        boolean success = false;
        FTPClient ftp = new FTPClient();
        try {
            int reply;

            // 连接FTP服务器
            if (port > -1) {
                ftp.connect(ip, port);
            } else {
                ftp.connect(ip);
            }

            // 登录
            ftp.login(username, password);
            reply = ftp.getReplyCode();
            if (!FTPReply.isPositiveCompletion(reply)) {
                ftp.disconnect();
                return success;
            }

            // 转移到FTP服务器目录
            ftp.changeWorkingDirectory(remotePath);
            success = ftp.deleteFile(remotePath + "/" + fileName);
            ftp.logout();
        } catch (IOException e) {
            e.printStackTrace();
            success = false;
        } finally {
            if (ftp.isConnected()) {
                try {
                    ftp.disconnect();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return success;
    }

    /**
     * Description: 从FTP服务器下载文件
     * 
     * @param ip
     *            FTP服务器hostname
     * @param port
     *            FTP服务器端口
     * @param username
     *            FTP登录账号
     * @param password
     *            FTP登录密码
     * @param remotePath
     *            FTP服务器上的相对路径
     * @param fileName
     *            要下载的文件名
     * @param localPath
     *            下载后保存到本地的路径
     * @return
     */
    public static boolean downloadFile(String ip, int port, String username, String password, String remotePath,
            String fileName, String localPath) {
        boolean success = false;
        FTPClient ftp = new FTPClient();
        try {
            int reply;

            // 连接FTP服务器
            if (port > -1) {
                ftp.connect(ip, port);
            } else {
                ftp.connect(ip);
            }

            ftp.login(username, password);// 登录
            reply = ftp.getReplyCode();
            if (!FTPReply.isPositiveCompletion(reply)) {
                ftp.disconnect();
                return success;
            }
            ftp.changeWorkingDirectory(remotePath);// 转移到FTP服务器目录
            FTPFile[] fs = ftp.listFiles();
            for (FTPFile ff : fs) {
                if (ff.getName().equals(fileName)) {
                    File localFile = new File(localPath + "/" + ff.getName());

                    OutputStream is = new FileOutputStream(localFile);
                    ftp.retrieveFile(ff.getName(), is);
                    is.close();
                }
            }

            ftp.logout();
            success = true;
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (ftp.isConnected()) {
                try {
                    ftp.disconnect();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return success;
    }

    /**
     * Description: 向FTP服务器上传文件
     * 
     * @param ip
     *            FTP服务器hostname
     * @param port
     *            FTP服务器端口，如果默认端口请写-1
     * @param username
     *            FTP登录账号
     * @param password
     *            FTP登录密码
     * @param path
     *            FTP服务器保存目录
     * @param filename
     *            上传到FTP服务器上的文件名
     * @param input
     *            输入流
     * @return 成功返回true，否则返回false
     */
    public static boolean uploadFile(String ip, int port, String username, String password, String path,
            String filename, InputStream input) {
        boolean success = false;
        FTPClient ftp = new FTPClient();
        try {
            int reply;

            // 连接FTP服务器
            if (port > -1) {
                ftp.connect(ip, port);
            } else {
                ftp.connect(ip);
            }

            // 登录FTP
            ftp.login(username, password);
            reply = ftp.getReplyCode();
            if (!FTPReply.isPositiveCompletion(reply)) {
                ftp.disconnect();
                return success;
            }
            ftp.changeWorkingDirectory(path);
            ftp.storeFile(filename, input);

            input.close();
            ftp.logout();
            success = true;
        } catch (IOException e) {
            success = false;
            e.printStackTrace();
        } finally {
            if (ftp.isConnected()) {
                try {
                    ftp.disconnect();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return success;
    }

}

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获取连接时候：
ftp.enterLocalPassiveMode();
这句话特别重要。