JavaWeb之文件上传、下载

文件上传

service

public String saveImage(MultipartFile file) throws IOException {
		// 正确性检验
        int dotPos = file.getOriginalFilename().lastIndexOf(".");
        if (dotPos < 0) {
            return null;
        }
        String fileExt = file.getOriginalFilename().substring(dotPos + 1).toLowerCase();
        if (!ToutiaoUtil.isFileAllowed(fileExt)) {
            return null;
        }
		//给文件取一个新的名字
        String fileName = UUID.randomUUID().toString().replaceAll("-", "") + "." + fileExt;
        Files.copy(file.getInputStream(), new File(ToutiaoUtil.IMAGE_DIR + fileName).toPath(),
                StandardCopyOption.REPLACE_EXISTING);
        return ToutiaoUtil.TOUTIAO_DOMAIN + "image?name=" + fileName;
    }

ToutiaoUtil

public static String TOUTIAO_DOMAIN = "http://127.0.0.1:8080/";
    public static String IMAGE_DIR = "D:/upload/";
    public static String[] IMAGE_FILE_EXTD = new String[] {"png", "bmp", "jpg", "jpeg"};

    public static boolean isFileAllowed(String fileName) {
        for (String ext : IMAGE_FILE_EXTD) {
            if (ext.equals(fileName)) {
                return true;
            }
        }
        return false;
    }

关于StandardCopyOption的选项

有三个选择，分别是

ATOMIC_MOVE Move the file as an atomic file system operation. 解释： copy() 方法不支持StandardCopyOption的ATOMIC_MOVE选项，在文件拷贝中该选项是一个无意义的。 用于文件的原子性移动操作，要么移动成功，要么不用移动。

COPY_ATTRIBUTES Copy attributes to the new file. 解释： 尝试将文件的属性拷贝到目标文件。

REPLACE_EXISTING Replace an existing file if it exists. 解释：当文件已经存在时，目标文件将被代替。

使用七牛云存储图片

@Service
public class QiniuService {
    private static final Logger logger = LoggerFactory.getLogger(QiniuService.class);
    //设置好账号的ACCESS_KEY和SECRET_KEY
    String ACCESS_KEY = "abNXnXBIlI6viRaOeRY6Hk-zc3V-NpjLcGfYz5kD";
    String SECRET_KEY = "QP7Xja3FmP1Zyl-oxwQDCb7T6wCoEFKoO-0vht_5";
    //要上传的空间
    String bucketname = "nowcoder";

    //密钥配置
    Auth auth = Auth.create(ACCESS_KEY, SECRET_KEY);
    //创建上传对象
    UploadManager uploadManager = new UploadManager();

    private static String QINIU_IMAGE_DOMAIN = "http://7xsetu.com1.z0.glb.clouddn.com/";

    //简单上传，使用默认策略，只需要设置上传的空间名就可以了
    public String getUpToken() {
        return auth.uploadToken(bucketname);
    }

    public String saveImage(MultipartFile file) throws IOException {
        try {
            int dotPos = file.getOriginalFilename().lastIndexOf(".");
            if (dotPos < 0) {
                return null;
            }
            String fileExt = file.getOriginalFilename().substring(dotPos + 1).toLowerCase();
            if (!ToutiaoUtil.isFileAllowed(fileExt)) {
                return null;
            }

            String fileName = UUID.randomUUID().toString().replaceAll("-", "") + "." + fileExt;
            //调用put方法上传
            Response res = uploadManager.put(file.getBytes(), fileName, getUpToken());
            //打印返回的信息
            if (res.isOK() && res.isJson()) {
                return QINIU_IMAGE_DOMAIN + JSONObject.parseObject(res.bodyString()).get("key");
            } else {
                logger.error("七牛异常:" + res.bodyString());
                return null;
            }
        } catch (QiniuException e) {
            // 请求失败时打印的异常的信息
            logger.error("七牛异常:" + e.getMessage());
            return null;
        }
    }
}

文件下载

@RequestMapping(path = {"/image"}, method = {RequestMethod.GET})
    @ResponseBody
    public void getImage(@RequestParam("name") String imageName,
                         HttpServletResponse response) {
        try {
            response.setContentType("image/jpeg");
            StreamUtils.copy(new FileInputStream(new
                    File(ToutiaoUtil.IMAGE_DIR + imageName)), response.getOutputStream());
        } catch (Exception e) {
            logger.error("读取图片错误" + imageName + e.getMessage());
        }
    }