<!--apache下，包含連接ftp服務(wù)器的工具-->
<dependency>
    <groupId>commons-net</groupId>
    <artifactId>commons-net</artifactId>
    <version>3.6</version>
</dependency>

import lombok.extern.slf4j.Slf4j;
import org.apache.commons.net.ftp.FTP;
import org.apache.commons.net.ftp.FTPClient;
import org.apache.commons.net.ftp.FTPReply;
import java.io.*;
import java.nio.charset.StandardCharsets;
@Slf4j
public class FtpUtil {
    /**
     * 獲取一個ftp連接
     * @param host ip地址
     * @param port 端口
     * @param username 用戶名
     * @param password 密碼
     * @return 返回ftp連接對象
     * @throws Exception 連接ftp時發(fā)生的各種異常
     */
    public static FTPClient getFtpClient(String host, Integer port, String username, String password) throws Exception{
        FTPClient ftpClient = new FTPClient();
        // 連接服務(wù)器
        ftpClient.connect(host, port);
        int reply = ftpClient.getReplyCode();
        if(!FTPReply.isPositiveCompletion(reply)){
            log.error("無法連接至ftp服務(wù)器， host:{}, port:{}", host, port);
            ftpClient.disconnect();
            return null;
        }
        // 登入服務(wù)器
        boolean login = ftpClient.login(username, password);
        if(!login){
            log.error("登錄失敗， 用戶名或密碼錯誤");
            ftpClient.logout();
            ftpClient.disconnect();
            return null;
        }
        // 連接并且成功登陸ftp服務(wù)器
        log.info("login success ftp server, host:{}, port:{}, user:{}", host, port, username);
        // 設(shè)置通道字符集， 要與服務(wù)端設(shè)置一致
        ftpClient.setControlEncoding("UTF-8");
        // 設(shè)置文件傳輸編碼類型， 字節(jié)傳輸：BINARY_FILE_TYPE, 文本傳輸：ASCII_FILE_TYPE， 建議使用BINARY_FILE_TYPE進行文件傳輸
        ftpClient.setFileType(FTP.BINARY_FILE_TYPE);
        // 動模式: enterLocalActiveMode(),被動模式: enterLocalPassiveMode(),一般選擇被動模式
        ftpClient.enterLocalPassiveMode();
        // 切換目錄
        //ftpClient.changeWorkingDirectory("xxxx");
        return ftpClient;
    }
    /**
     * 斷開ftp連接
     * @param ftpClient ftp連接客戶端
     */
    public static void disConnect(FTPClient ftpClient){
        if(ftpClient == null){
            return;
        }
        try {
            log.info("斷開ftp連接， host:{}, port:{}", ftpClient.getPassiveHost(), ftpClient.getPassivePort());
            ftpClient.logout();
            ftpClient.disconnect();
        } catch (IOException e) {
            e.printStackTrace();
            log.error("ftp連接斷開異常， 請檢查");
        }
    }
    /**
     * 文件下載
     * @param ftpClient ftp連接客戶端
     * @param path 文件路徑
     * @param fileName 文件名稱
     */
    public static void download(FTPClient ftpClient, String path, String fileName) throws Exception {
        if(ftpClient == null || path == null || fileName == null){
            return;
        }
        // 中文目錄處理存在問題， 轉(zhuǎn)化為ftp能夠識別中文的字符集
        String remotePath;
        try {
            remotePath = new String(path.getBytes(StandardCharsets.UTF_8), FTP.DEFAULT_CONTROL_ENCODING);
        } catch (UnsupportedEncodingException e) {
            remotePath = path;
        }
        InputStream inputStream = ftpClient.retrieveFileStream(remotePath);
        if (inputStream == null) {
            log.error("{}在ftp服務(wù)器中不存在，請檢查", path);
            return;
        }
        FileOutputStream outputStream = new FileOutputStream("D:\\test\\" + fileName);
        BufferedInputStream bufferedInputStream = new BufferedInputStream(inputStream);
        BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(outputStream);
        try{
            byte[] buffer = new byte[2048];
            int i;
            while ((i = bufferedInputStream.read(buffer)) != -1) {
                bufferedOutputStream.write(buffer, 0, i);
                bufferedOutputStream.flush();
            }
        } catch (Exception e) {
            log.error("文件下載異常", e);
            log.error("{}下載異常，請檢查", path);
        }
        inputStream.close();
        outputStream.close();
        bufferedInputStream.close();
        bufferedOutputStream.close();
        // 關(guān)閉流之后必須執(zhí)行，否則下一個文件導(dǎo)致流為空
        boolean complete = ftpClient.completePendingCommand();
        if(complete){
            log.info("文件{}下載完成", remotePath);
        }else{
            log.error("文件{}下載失敗", remotePath);
        }
    }
    /**
     * 上傳文件
     * @param ftpClient ftp連接客戶端
     * @param sourcePath 源地址
     */
    public static void upload(FTPClient ftpClient, String sourcePath) throws Exception{
        if(ftpClient == null || sourcePath == null){
            return;
        }
        File file = new File(sourcePath);
        if(!file.exists() || !file.isFile()){
            return;
        }
        // 中文目錄處理存在問題， 轉(zhuǎn)化為ftp能夠識別中文的字符集
        String remotePath;
        try {
            remotePath = new String(file.getName().getBytes(StandardCharsets.UTF_8), FTP.DEFAULT_CONTROL_ENCODING);
        } catch (UnsupportedEncodingException e) {
            remotePath = file.getName();
        }
        try(
                InputStream inputStream = new FileInputStream(file);
                OutputStream outputStream = ftpClient.storeFileStream(remotePath);
        ){
            byte[] buffer = new byte[2048];
            int length;
            while((length = inputStream.read(buffer)) != -1){
                outputStream.write(buffer, 0, length);
                outputStream.flush();
            }
        }catch (Exception e){
            log.error("文件上傳異常", e);
        }
        // 關(guān)閉流之后必須執(zhí)行，否則下一個文件導(dǎo)致流為空
        boolean complete = ftpClient.completePendingCommand();
        if(complete){
            log.info("文件{}上傳完成", remotePath);
        }else{
            log.error("文件{}上傳失敗", remotePath);
        }
    }
}

@Slf4j
@RestController
public class FtpController {
    private static final String FTP_HOST = "your host";
    private static final Integer FTP_PORT = 21;
    private static final String FTP_USERNAME = "your username";
    private static final String FTP_PASSWORD = "your password";
    @GetMapping("/test")
    public void test() throws Exception{
        FTPClient ftpClient = FtpUtil.getFtpClient(FTP_HOST, FTP_PORT, FTP_USERNAME, FTP_PASSWORD);
        // 展示文件夾
        FTPFile[] ftpFiles = ftpClient.listDirectories();
        for(FTPFile file : ftpFiles){
            System.out.println(file.getName());
        }
        // 下載文件
        FtpUtil.download(ftpClient, "test.txt", "test.txt");
        //FtpUtil.download(ftpClient, "test.py", "test.py");
        // 上傳文件
        FtpUtil.upload(ftpClient, "D:\\test\\test.py");
        FtpUtil.disConnect(ftpClient);
    }
}

// 關(guān)閉流之后必須執(zhí)行，否則下一個文件導(dǎo)致流為空
boolean complete = ftpClient.completePendingCommand();
if(complete){
    log.info("文件{}下載完成", remotePath);
}else{
    log.error("文件{}下載失敗", remotePath);
}