The ftp4j library implements a Java full-features FTP client. With ftp4j embedded in your application you can: transfer files (upload and download), browse the remote FTP site (directory listing included), create, delete, rename and move remote directories and files.
ftp4j類庫可支持實現java版的FTP客戶端，可應用到你的應用程序中，實現文件的上傳下載，瀏覽遠程FTP服務器上的目錄和文件，創建、刪除、重命，移動遠程目錄和文件等操作。
ftp4j的特點：
1、100%免費
2、可遠程連接FTP服務器
3、遠程操作
4、文件上傳下載
5、異常捕獲
下載路徑：http://www.sauronsoftware.it/projects/ftp4j/ftp4j-1.3.1.zip
快速上手：
The main class of the library is FTPClient (it.sauronsoftware.ftp4j.FTPClient).
Start creating a FTPClient instance:
FTPClient client = new FTPClient();
Connect now to a remote FTP service:
client.connect("ftp.host.com");
If the service port is other than the standard 21:
client.connect("ftp.host.com", port);
In example:
client.connect("ftp.host.com", 8021);
Step now to the login procedure:
client.login("carlo", "mypassword");
If no exception is thrown you are now authenticated to the remote server. Otherwise, if the authentication attempt fails, you receive a it.sauronsoftware.ftp4j.FTPException.
Anonymous authentication, if admitted by the connected service, can be done sending the username "anonymous" and an arbitrary password (note that some servers require an e-mail address in place of the password):
client.login("anonymous", "ftp4j");
Do anything you want with the remote FTP service, then disconnect:
client.disconnect(true);
This one sends the FTP QUIT command to the remote server, requesting a legal disconnect procedure. If you just want to break the connection, without sending any advice to the server, call:
client.disconnect(false);
Connecting through a proxy
The client connects to the server through a connector (an object implementing the it.sauronsoftware.ftp4j.FTPConnector interface), which returns to the client an already open connection (an object implementing the it.sauronsoftware.ftp4j.FTPConnection interface). That is why ftp4j could support a large set of proxies.
The connector for a client instance can be setted with the setConnector() method, obviously before connecting the remote server:
client.setConnector(anyConnectorYouWant);
Browsing the remote site
Get the current directory absolute path calling:
String dir = client.currentDirectory();
Change directory with:
client.changeDirectory(newPath);
You can use both absolute and relative paths:
client.changeDirectory("/an/absolute/one");
client.changeDirectory("relative");
Back to the parent directory with:
client.changeDirectoryUp();
Renaming files and directories
To rename a remote file or directory:
client.rename("oldname", "newname");
Moving files and directories
The rename() method can also be used to move files and directories from a location to another.
In example, think in the current working directory you have a file called "myfile.txt", and you want to move it in the sub-directory "myfolder":
client.rename("myfile.txt", "myfolder/myfile.txt");
Deleting files
To delete a remote file call:
client.deleteFile(relativeOrAbsolutePath);
In example:
client.deleteFile("useless.txt");
Creating and deleting directories
You can create a new directory on the remote site, if the service gives you this oppurtunity:
client.createDirectory("newfolder");
You can also remove an existing one:
client.deleteDirectory(absoluteOrRelativePath);
In example:
client.deleteDirectory("oldfolder");
Please note that usually FTP servers can delete only empty directories.
Downloading and uploading files
The easiest way to download a remote file is a call to the download(String, File) method:
client.download("remoteFile.ext", new java.io.File("localFile.ext"));
To upload:
client.upload(new java.io.File("localFile.ext"));
參考文章路徑:http://www.sauronsoftware.it/projects/ftp4j/manual.php#3