一文解析Java如何连接FTP服务器

<dependency>
    <groupId>commons-net</groupId>
    <artifactId>commons-net</artifactId>
    <version>3.8.0</version>
</dependency>

import org.apache.commons.net.ftp.FTPClient;
import java.net.SocketException;
import java.io.IOException;

public class FTPConnectionExample {
    public static void main(String[] args) {
        FTPClient ftpClient = new FTPClient();
        String ftpServer = "your_ftp_server_ip";
        int ftpPort = 21;
        String username = "your_username";
        String password = "your_password";

​​​​​​​        try {
            // 连接 FTP 服务器
            ftpClient.connect(ftpServer, ftpPort);
            // 登录 FTP 服务器
            boolean login = ftpClient.login(username, password);
            boolean login1 = ftpClient.login("anonymous", "");
            if (login) {
                System.out.println("成功登录到 FTP 服务器");
                // 在这里可以进行后续的 FTP 操作
            } else {
                System.out.println("登录失败");
            }
        } catch (SocketException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            // 关闭连接
            try {
                if (ftpClient.isConnected()) {
                    ftpClient.logout();
                    ftpClient.disconnect();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

boolean changeDir = ftpClient.changeWorkingDirectory("/new/directory/path");
if (changeDir) {
    System.out.println("成功切换到指定目录");
} else {
    System.out.println("切换目录失败");
}

FTPFile[] files = ftpClient.listFiles();
for (FTPFile file : files) {
    System.out.println(file.getName());
}

File localFile = new File("path/to/local/file.txt");
InputStream inputStream = new FileInputStream(localFile);
boolean upload = ftpClient.storeFile("remote_file_name.txt", inputStream);
if (upload) {
    System.out.println("文件上传成功");
} else {
    System.out.println("文件上传失败");
}
inputStream.close();

OutputStream outputStream = new FileOutputStream("path/to/local/downloaded_file.txt");
boolean download = ftpClient.retrieveFile("remote_file.txt", outputStream);
if (download) {
    System.out.println("文件下载成功");
} else {
    System.out.println("文件下载失败");
}
outputStream.close();

FTPFile[] files = ftpClient.listFiles();
for (FTPFile file : files) {
    long lastModified = file.getTimestamp().getTimeInMillis();
    System.out.println("文件 " + file.getName() + " 的最近修改时间：" + new Date(lastModified));
}

ftpClient.setConnectTimeout(5000); // 设置连接超时时间为 5 秒

ftpClient.enterLocalPassiveMode();