@Configuration
public class WebMvcConfig implements WebMvcConfigurer {

    @Autowired
    FileServiceImpl fileService;

    @Override
    public void addResourceHandlers(ResourceHandlerRegistry registry) {
        //將匹配上/files/**虛擬路徑的url映射到文件上傳到服務(wù)器的目錄，獲取靜態(tài)資源
        registry.addResourceHandler("/" + fileService.pathPattern + "/**").addResourceLocations("file:" + fileService.filePath);
        WebMvcConfigurer.super.addResourceHandlers(registry);
    }
}

@RestController
@RequestMapping("/file")
public class FileController {

    @Autowired
    private FileServiceImpl fileService;

    @PostMapping("/upload")
    public FileUploadResponse upload(@RequestParam("file") MultipartFile file) {
        return fileService.upload(file);
    }
}

@Slf4j
@Service
public class FileServiceImpl {

    //攔截的url，虛擬路徑
    public String pathPattern = "files";

    //自己設(shè)置的目錄
    private static final String fileDir = "fileStorage";

    //上傳文件存放目錄  =  工作目錄絕對(duì)路徑 + 自己設(shè)置的目錄，也可以直接自己指定服務(wù)器目錄
    //windows本地測(cè)試
    //絕對(duì)路徑: D:\develop\work\project\myblog\myblog-file-upload\fileStorage\202302021010345680.jpg
    //System.getProperty("user.dir")   D:\develop\work\project\myblog\myblog-file-upload
    //fileDir                          fileStorage
    //fileName                         202302021010345680.jpg
    public String filePath = System.getProperty("user.dir") + File.separator + fileDir + File.separator;

    private static final AtomicInteger SUFFIX = new AtomicInteger(0);

    @Value(value = "${file.upload.suffix:jpg,jpeg,png,bmp,xls,xlsx,pdf}")
    private String fileUploadSuffix;

    public FileUploadResponse upload(MultipartFile file) {
        FileUploadResponse result = new FileUploadResponse();
        if (file.isEmpty()) {
            log.error("the file to be uploaded is empty");
            return result;
        }
        List<String> suffixList = Lists.newArrayList(fileUploadSuffix.split(","));

        try {
            //校驗(yàn)文件后綴
            String originalFilename = file.getOriginalFilename();
            String suffix = originalFilename.substring(originalFilename.lastIndexOf(".") + 1);
            if (!suffixList.contains(suffix)) {
                log.error("unsupported file format");
                return result;
            }

            //首次需生成目錄
            File folder = new File(filePath);
            if (!folder.exists()) {
                folder.mkdirs();
            }

            String fileName = timeFormat(System.currentTimeMillis()) + SUFFIX.getAndIncrement() + "." + suffix;
            String absolutePath = filePath + fileName;
            log.info("absolutePath is {}", absolutePath);
            file.transferTo(new File(absolutePath));

            String separator = "/";
            String path = separator + pathPattern + separator + fileName;
            result.setPath(path);
            result.setFileName(fileName);
        } catch (Exception e) {
            log.error("the file upload error occurred. e ", e);
        }
        return result;
    }

    public static String timeFormat(Long time) {
        if (Objects.isNull(time)) {
            return null;
        }
        DateFormat sdf = new SimpleDateFormat("yyyyMMddHHmmssSSS");
        return sdf.format(time);
    }

}