package com.ftp.demo;

import org.apache.commons.net.ftp.FTP;
import org.apache.commons.net.ftp.FTPClient;
import org.apache.commons.net.ftp.FTPFile;

import java.io.*;

public class FtpDemo {

    public static void main(String[] args) {
        FTPClient ftpClient = new FTPClient();
        String server = "url";
        int port = 21;
        String username = "user";
        String password = "123";
        try {
            // 连接到FTP服务器
            ftpClient.connect(server, port);
            ftpClient.login(username, password);

            // 设置文件传输模式为二进制
            ftpClient.setFileType(FTP.BINARY_FILE_TYPE);

            if (ftpClient.getReplyCode() > 0) {
                String dirs = "/filesync";
                ftpClient.enterLocalPassiveMode();
                ftpClient.changeWorkingDirectory(dirs);
                FTPFile[] ftpFiles = ftpClient.listFiles();
                for (int i = 0; i < ftpFiles.length; i++) {
                    FTPFile ftpFile = ftpFiles[i];
                    System.out.println(ftpFile.getName());
                    InputStream inputStream = ftpClient.retrieveFileStream(dirs + File.separator + ftpFile.getName());
                    if (inputStream == null) {
                        continue;
                    }
                    BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));

                    String s=null;
                    while ((s= reader.readLine())!=null){
                        System.out.println(s);
                    }
                    System.out.println("ftpFile.getName() end.");
                    inputStream.close();
                    reader.close();                                        
​​​​​​​                    ftpClient.completePendingCommand();
                }
            }

            // 断开连接
            ftpClient.logout();
            ftpClient.disconnect();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

maven依赖

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