The technical principles of the FTP transmission framework and its application in the Java class library
The technical principles of the FTP transmission framework and its application in the Java class library
Summary:
FTP (file transmission protocol) is a commonly used protocol for transmission between computers.In Java development, many types of libraries can be used to achieve FTP transmission, such as Apache Commons Net, Apache Commons VFS, and JSCH.This article will introduce the technical principles of FTP transmission and provide application examples in the Java class library.
1. Technical principle of FTP transmission:
The main principle of FTP transmission is a communication connection based on the client and the server. The connection uses the TCP/IP protocol for data transmission on the network.The client can interact with the server through the FTP command, and use specific commands to implement the file uploading, downloading, and deleting operations.
2. FTP class library in Java:
2.1 Apache Commons Net：
Apache Commonts Net is an open source Java class library that is used to implement the client and server of the network protocol.It provides rich classes and methods to write FTP client applications.Here are a sample code that uses Apache Commons Net to implement FTP files:
import org.apache.commons.net.ftp.FTP;
import org.apache.commons.net.ftp.FTPClient;
import java.io.FileInputStream;
import java.io.IOException;
public class FTPExample {
public static void main(String[] args) {
String server = "ftp.example.com";
int port = 21;
String user = "username";
String password = "password";
String file = "example.txt";
FTPClient ftpClient = new FTPClient();
try {
ftpClient.connect(server, port);
ftpClient.login(user, password);
FileInputStream fileInputStream = new FileInputStream(file);
ftpClient.storeFile(file, fileInputStream);
fileInputStream.close();
ftpClient.logout();
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
if (ftpClient.isConnected()) {
ftpClient.disconnect();
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
2.2 Apache Commons VFS：
Apache Commons VFS is another powerful Java class library for processing various file systems.It supports a variety of protocols including FTP.The following is an example code that uses Apache Commons VFS to implement FTP files:
import org.apache.commons.vfs2.*;
import java.io.File;
public class VFSExample {
public static void main(String[] args) {
String server = "ftp://ftp.example.com";
String user = "username";
String password = "password";
String file = "example.txt";
try {
FileSystemManager fsManager = VFS.getManager();
FileObject remoteFile = fsManager.resolveFile(server + "/" + file,
fsOptions(user, password));
File localFile = new File("local.txt");
FileObject localFileObj = fsManager.resolveFile(localFile.getAbsolutePath());
localFileObj.copyFrom(remoteFile, Selectors.SELECT_SELF);
localFileObj.close();
remoteFile.close();
} catch (FileSystemException e) {
e.printStackTrace();
}
}
private static FileSystemOptions fsOptions(String user, String password) {
FileSystemOptions opts = new FileSystemOptions();
try {
DefaultFileSystemConfigBuilder.getInstance().setUserAuthenticator(opts,
new StaticUserAuthenticator(null, user, password));
} catch (FileSystemException e) {
e.printStackTrace();
}
return opts;
}
}
2.3 JSCH ：
JSCH is a Java class library for implementing the SSH protocol, but it can also be used for FTP transmission.The following is an example code that uses JSCH to implement FTP files:
import com.jcraft.jsch.*;
public class JSchExample {
public static void main(String[] args) {
String host = "ftp.example.com";
int port = 22;
String user = "username";
String password = "password";
String file = "example.txt";
try {
JSch jsch = new JSch();
Session session = jsch.getSession(user, host, port);
session.setPassword(password);
session.setConfig("StrictHostKeyChecking", "no");
session.connect();
ChannelSftp channelSftp = (ChannelSftp) session.openChannel("sftp");
channelSftp.connect();
channelSftp.rm(file);
channelSftp.disconnect();
session.disconnect();
} catch (JSchException | SftpException e) {
e.printStackTrace();
}
}
}
in conclusion:
This article introduces the technical principles of FTP transmission, and provides the use of Apache Commons Net, Apache Commons VFS and JSCH and other JAVA libraries to implement FTP transmission sample code.These class libraries provide rich methods and functions, which can easily create FTP client applications and implement operations to upload, download, and delete files.By using these class libraries, developers can easily integrate FTP transmission functions into their Java applications.
