本文利用apache ftp工具實現檔案的上傳下載和刪除。具體如下：

1、下載相應的jar包

     commons-net-1.4.1.jar

2、實現程式碼如下：

public class FtpUtils {
        //ftp伺服器地址
        public String hostname = "192.168.1.249";
        //ftp伺服器埠號預設為21
        public Integer port = 21 ;
        //ftp登入賬號
        public String username = "root";
        //ftp登入密碼
        public String password = "123";
        
        public FTPClient ftpClient = null;
        
        /**
         * 初始化ftp伺服器
         */
        public void initFtpClient() {
            ftpClient = new FTPClient();
            ftpClient.setControlEncoding("utf-8");
            try {
                System.out.println("connecting...ftp伺服器:"+this.hostname+":"+this.port); 
                ftpClient.connect(hostname, port); //連線ftp伺服器
                ftpClient.login(username, password); //登入ftp伺服器
                int replyCode = ftpClient.getReplyCode(); //是否成功登入伺服器
                if(!FTPReply.isPositiveCompletion(replyCode)){
                    System.out.println("connect failed...ftp伺服器:"+this.hostname+":"+this.port); 
                }
                System.out.println("connect successfu...ftp伺服器:"+this.hostname+":"+this.port); 
            }catch (MalformedURLException e) { 
               e.printStackTrace(); 
            }catch (IOException e) { 
               e.printStackTrace(); 
            } 
        }

        /**
        * 上傳檔案
        * @param pathname ftp服務儲存地址
        * @param fileName 上傳到ftp的檔名
        *  @param originfilename 待上傳檔案的名稱（絕對地址） * 
        * @return
        */
        public boolean uploadFile( String pathname, String fileName,String originfilename){
            boolean flag = false;
            InputStream inputStream = null;
            try{
                System.out.println("開始上傳檔案");
                inputStream = new FileInputStream(new File(originfilename));
                initFtpClient();
                ftpClient.setFileType(ftpClient.BINARY_FILE_TYPE);
                CreateDirecroty(pathname);
                ftpClient.makeDirectory(pathname);
                ftpClient.changeWorkingDirectory(pathname);
                ftpClient.storeFile(fileName, inputStream);
                inputStream.close();
                ftpClient.logout();
                flag = true;
                System.out.println("上傳檔案成功");
            }catch (Exception e) {
                System.out.println("上傳檔案失敗");
                e.printStackTrace();
            }finally{
                if(ftpClient.isConnected()){ 
                    try{
                        ftpClient.disconnect();
                    }catch(IOException e){
                        e.printStackTrace();
                    }
                } 
                if(null != inputStream){
                    try {
                        inputStream.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    } 
                } 
            }
            return true;
        }
        /**
         * 上傳檔案
         * @param pathname ftp服務儲存地址
         * @param fileName 上傳到ftp的檔名
         * @param inputStream 輸入檔案流 
         * @return
         */
        public boolean uploadFile( String pathname, String fileName,InputStream inputStream){
            boolean flag = false;
            try{
                System.out.println("開始上傳檔案");
                initFtpClient();
                ftpClient.setFileType(ftpClient.BINARY_FILE_TYPE);
                CreateDirecroty(pathname);
                ftpClient.makeDirectory(pathname);
                ftpClient.changeWorkingDirectory(pathname);
                ftpClient.storeFile(fileName, inputStream);
                inputStream.close();
                ftpClient.logout();
                flag = true;
                System.out.println("上傳檔案成功");
            }catch (Exception e) {
                System.out.println("上傳檔案失敗");
                e.printStackTrace();
            }finally{
                if(ftpClient.isConnected()){ 
                    try{
                        ftpClient.disconnect();
                    }catch(IOException e){
                        e.printStackTrace();
                    }
                } 
                if(null != inputStream){
                    try {
                        inputStream.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    } 
                } 
            }
            return true;
        }
        //改變目錄路徑
         public boolean changeWorkingDirectory(String directory) {
                boolean flag = true;
                try {
                    flag = ftpClient.changeWorkingDirectory(directory);
                    if (flag) {
                      System.out.println("進入資料夾" + directory + " 成功！");

                    } else {
                        System.out.println("進入資料夾" + directory + " 失敗！開始建立資料夾");
                    }
                } catch (IOException ioe) {
                    ioe.printStackTrace();
                }
                return flag;
            }

        //建立多層目錄檔案，如果有ftp伺服器已存在該檔案，則不建立，如果無，則建立
        public boolean CreateDirecroty(String remote) throws IOException {
            boolean success = true;
            String directory = remote + "/";
            // 如果遠端目錄不存在，則遞迴建立遠端伺服器目錄
            if (!directory.equalsIgnoreCase("/") && !changeWorkingDirectory(new String(directory))) {
                int start = 0;
                int end = 0;
                if (directory.startsWith("/")) {
                    start = 1;
                } else {
                    start = 0;
                }
                end = directory.indexOf("/", start);
                String path = "";
                String paths = "";
                while (true) {
                    String subDirectory = new String(remote.substring(start, end).getBytes("GBK"), "iso-8859-1");
                    path = path + "/" + subDirectory;
                    if (!existFile(path)) {
                        if (makeDirectory(subDirectory)) {
                            changeWorkingDirectory(subDirectory);
                        } else {
                            System.out.println("建立目錄[" + subDirectory + "]失敗");
                            changeWorkingDirectory(subDirectory);
                        }
                    } else {
                        changeWorkingDirectory(subDirectory);
                    }

                    paths = paths + "/" + subDirectory;
                    start = end + 1;
                    end = directory.indexOf("/", start);
                    // 檢查所有目錄是否建立完畢
                    if (end <= start) {
                        break;
                    }
                }
            }
            return success;
        }

      //判斷ftp伺服器檔案是否存在    
        public boolean existFile(String path) throws IOException {
                boolean flag = false;
                FTPFile[] ftpFileArr = ftpClient.listFiles(path);
                if (ftpFileArr.length > 0) {
                    flag = true;
                }
                return flag;
            }
        //建立目錄
        public boolean makeDirectory(String dir) {
            boolean flag = true;
            try {
                flag = ftpClient.makeDirectory(dir);
                if (flag) {
                    System.out.println("建立資料夾" + dir + " 成功！");

                } else {
                    System.out.println("建立資料夾" + dir + " 失敗！");
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
            return flag;
        }
        
        /** * 下載檔案 * 
        * @param pathname FTP伺服器檔案目錄 * 
        * @param filename 檔名稱 * 
        * @param localpath 下載後的檔案路徑 * 
        * @return */
        public  boolean downloadFile(String pathname, String filename, String localpath){ 
            boolean flag = false; 
            OutputStream os=null;
            try { 
                System.out.println("開始下載檔案");
                initFtpClient();
                //切換FTP目錄 
                ftpClient.changeWorkingDirectory(pathname); 
                FTPFile[] ftpFiles = ftpClient.listFiles(); 
                for(FTPFile file : ftpFiles){ 
                    if(filename.equalsIgnoreCase(file.getName())){ 
                        File localFile = new File(localpath + "/" + file.getName()); 
                        os = new FileOutputStream(localFile); 
                        ftpClient.retrieveFile(file.getName(), os); 
                        os.close(); 
                    } 
                } 
                ftpClient.logout(); 
                flag = true; 
                System.out.println("下載檔案成功");
            } catch (Exception e) { 
                System.out.println("下載檔案失敗");
                e.printStackTrace(); 
            } finally{ 
                if(ftpClient.isConnected()){ 
                    try{
                        ftpClient.disconnect();
                    }catch(IOException e){
                        e.printStackTrace();
                    }
                } 
                if(null != os){
                    try {
                        os.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    } 
                } 
            } 
            return flag; 
        }
        
        /** * 刪除檔案 * 
        * @param pathname FTP伺服器儲存目錄 * 
        * @param filename 要刪除的檔名稱 * 
        * @return */ 
        public boolean deleteFile(String pathname, String filename){ 
            boolean flag = false; 
            try { 
                System.out.println("開始刪除檔案");
                initFtpClient();
                //切換FTP目錄 
                ftpClient.changeWorkingDirectory(pathname); 
                ftpClient.dele(filename); 
                ftpClient.logout();
                flag = true; 
                System.out.println("刪除檔案成功");
            } catch (Exception e) { 
                System.out.println("刪除檔案失敗");
                e.printStackTrace(); 
            } finally {
                if(ftpClient.isConnected()){ 
                    try{
                        ftpClient.disconnect();
                    }catch(IOException e){
                        e.printStackTrace();
                    }
                } 
            }
            return flag; 
        }
        
        public static void main(String[] args) {
            FtpUtils ftp =new FtpUtils(); 
            //ftp.uploadFile("ftpFile/data", "123.docx", "E://123.docx");
            //ftp.downloadFile("ftpFile/data", "123.docx", "F://");
            ftp.deleteFile("ftpFile/data", "123.docx");
            System.out.println("ok");
        }
}