Explore the technical principles and implementation of the FTP transmission framework in the Java library

The FTP transmission framework in the Java library is a technical tool for implementing file transmission protocol (FTP).FTP is a standard protocol for file transmission on a computer network.The Java class library provides some classes and methods for processing FTP transmission, so that developers can easily implement FTP transmission function. The implementation of the FTP transmission framework usually involves the following aspects: 1. Connection and authentication: The FTP class in the Java class library provides a method of establishing connections and authentication with the FTP server.Generally, the host name and the port number are connected to the FTP server, and the user name and password are used to verify the identity.The following is an example code: String server = "ftp.example.com"; int port = 21; String user = "username"; String password = "password"; FTPClient ftpClient = new FTPClient(); ftpClient.connect(server, port); ftpClient.login(user, password); 2. File upload and download: FTP transmission framework provides methods to upload and download files.When downloading files from the FTP server, you need to specify the file path on the server and the local storage path.When uploading the file, you need to specify the local file path and server storage path.The following is an example code: String remoteFile = "/path/to/remote/file.txt"; String localFile = "/path/to/local/file.txt"; // download file OutputStream outputStream = new FileOutputStream(localFile); ftpClient.retrieveFile(remoteFile, outputStream); outputStream.close(); // upload files InputStream inputStream = new FileInputStream(localFile); ftpClient.storeFile(remoteFile, inputStream); inputStream.close(); 3. Directory operation: The FTP transmission framework also provides methods for processing directory operations.You can list the files and directory on the server, create and delete the directory, and change the current directory.The following is an example code: // List the files and directory in the directory FTPFile[] files = ftpClient.listFiles(); // Create a directory ftpClient.makeDirectory("/path/to/new/directory"); // Delete the directory ftpClient.removeDirectory("/path/to/directory"); // Change the current directory ftpClient.changeWorkingDirectory("/path/to/directory"); 4. Progress monitoring: Sometimes, when transmitting large files, you need to monitor and control the transmission process.The FTP transmission framework provides some callback functions and listeners, which can be used to monitor the progress and state of transmission.The following is an example code: FTPClientConfig config = new FTPClientConfig(); config.setCopyStreamListener(new CopyStreamAdapter() { @Override public void bytesTransferred(long totalBytesTransferred, int bytesTransferred, long streamSize) { // Progress monitoring logic } }); ftpClient.configure(config); In summary, the FTP transmission framework in the Java class library provides a set of convenient and easy -to -use APIs to achieve FTP transmission function.Developers can establish connection, identity verification, upload download files, and direct directory operations through these classes and methods, and can monitor progress by callback functions and listeners.