将文件转换为文件流传输下载文件(本节文件从FTP服务获取)

一丶需求

移动端根据文件流进行选择地址下载文件, 每次下载文件路径都会不同, 避免可根据地址重复下载或泄露文件.

二丶具体实现(直接上代码)

1丶编写接口(get请求)

		@GetMapping("/getPdfFile")
        @ApiOperation(value = "公众号拿取报告pdf接口")
        public AjaxResult getPdfFile(@RequestParam("chid") Integer chid, HttpServletResponse response) {
                return iMedicalAppointmentService.getCheckReportbyFile(chid, response);
        }

2丶连接FTP服务获取文件

	/**
     * @param filePath 文件相对路径
     * @param response 响应对象
     */
    public static void getPdfFileStream(String filePath, HttpServletResponse response) {
        FtpUtil ftpUtil = BeanHelper.getBean(FtpUtil.class);
        FTPClient ftpClient = ftpUtil.getFtpClient(3);
        ftpUtil.downFileStream(ftpClient, filePath, response);
    }

3丶将文件流写入响应对象

	/**
     * 文件流传输
     *
     * @param ftpClient FTP
     * @param fileName
     * @param response
     */
    public void downFileStream(FTPClient ftpClient, String fileName, HttpServletResponse response) {
        InputStream inputStream = null;
        OutputStream outputStream = null;
        try {
            // 设置文本类型
            response.setContentType(String.valueOf(MediaType.APPLICATION_OCTET_STREAM));
            // 设置文件类型和文件名
            response.setHeader(HttpHeaders.CONTENT_DISPOSITION, "attachment;filename=" + new Date().getTime() + ".pdf");
            outputStream = new BufferedOutputStream(response.getOutputStream());
            ftpClient.enterLocalPassiveMode();
            // 获取ftp上的文件流
            inputStream = ftpClient.retrieveFileStream(fileName);
            // 文件流写入
            int len;
            byte[] bytes = new byte[1024];
            while ((len = inputStream.read(bytes)) != -1) {
                outputStream.write(bytes, 0, len);
            }
        }catch (Exception e) {
            log.error("FTP file download failed！" + e.getMessage());
        } finally {
            try {
                if (inputStream != null) {
                    inputStream.close();
                }
                // 强制将缓存区的数据进行输出
                assert outputStream != null;
                outputStream.flush();
                // 关流
                outputStream.close();
            } catch (IOException e) {
                log.error("Download stream failed to close" + e.getMessage());
            }
        }
    }

FTP连接方法如下:

	/**
     * @param type 1-B超 2-心电图 3后续再加  3-36服务器
     * @author LingCoder
     * @date 2020/10/21 12:24
     * @description: 根据传进来的ftp类型，初始化对应ftp服务器
     */
    public  FTPClient getFtpClient(Integer type) {
        FTPClient ftpClient = new FTPClient();
        ftpClient.setControlEncoding("utf-8");

        FtpConnect ftpConnect = new FtpConnect();
        switch (type) {
            // B超
            case 1:
                log.info("connecting...ftp server:" + BCHostName + ":" + BCPort);
                ftpConnect.setHostname(BCHostName);
                ftpConnect.setPort(BCPort);
                ftpConnect.setUsername(BCUsername);
                ftpConnect.setPassword(BCPassword);
                break;

            // 心电图
            case 2:
                log.info("connecting...ftp server:" + XDTHostName + ":" + XDTPort);
                ftpConnect.setHostname(XDTHostName);
                ftpConnect.setPort(XDTPort);
                ftpConnect.setUsername(XDTUsername);
                ftpConnect.setPassword(XDTPassword);
                break;
            case 3:
                log.info("connecting...ftp server:" + HostName36 + ":" + Port36);
                ftpConnect.setHostname(HostName36);
                ftpConnect.setPort(Port36);
                ftpConnect.setUsername(Username36);
                ftpConnect.setPassword(Password36);
                break;
            case 4:
                log.info("connecting...ftp server:" + HostName51 + ":" + Port51);
                ftpConnect.setHostname(HostName51);
                ftpConnect.setPort(Port51);
                ftpConnect.setUsername(Username51);
                ftpConnect.setPassword(Password51);
                break;
            default:
                log.info("No ftp server has been matched yet");
                break;
        }

        try {
            //设置连接超时时间
            ftpClient.setDataTimeout(1000 * 120);

            // 连接ftp服务器
            ftpClient.connect(ftpConnect.getHostname(), ftpConnect.getPort());

            // 登录ftp服务器
            ftpClient.login(ftpConnect.getUsername(), ftpConnect.getPassword());

            // 中文支持
            ftpClient.setControlEncoding("UTF-8");

            // 设置文件类型为二进制（如果从FTP下载或上传的文件是压缩文件的时候，不进行该设置可能会导致获取的压缩文件解压失败）
            ftpClient.setFileType(FTPClient.BINARY_FILE_TYPE);

            //开启被动模式，否则文件上传不成功，也不报错
            ftpClient.enterLocalPassiveMode();

            // 是否成功登录服务器
            int replyCode = ftpClient.getReplyCode();

            // 开启服务器对UTF-8的支持，如果服务器支持就用UTF-8编码，否则就使用本地编码（GBK）.
            if (FTPReply.isPositiveCompletion(ftpClient.sendCommand(
                    "OPTS UTF8", "ON"))) {
                LOCAL_CHARSET = "UTF-8";
            }

            if (!FTPReply.isPositiveCompletion(replyCode)) {
                ftpClient.disconnect();
                throw new FtpConnectException("connect failed...ftp server:" + ftpConnect.getHostname() + ":" + ftpConnect.getPort());
            }
            log.info("connect successfu...ftp server:" + ftpConnect.getHostname() + ":" + ftpConnect.getPort());
        } catch (Exception e) {
            log.error(e.getMessage(), e);
        }

        return ftpClient;
    }