SpringBoot实现数据下资源的永久地址

目的：实现数据下资源的永久地址，无论这条数据下文件资源被替换成何种文件，但是预览地址始终不变

/**
 * 预览或下载文件
 * @param id 资源id
 * @return 文件
 */
@GetMapping("/preview/{id}")
public ResponseEntity<org.springframework.core.io.Resource> preview(@PathVariable("id") Long id) {
    LayoutResource layoutResource = layoutResourceService.getById(id);
    if(ObjectUtil.isEmpty(layoutResource)){
        throw new ServiceException("资源不存在");
    }
    SysOssVo sysOssVo = sysOssService.getById(layoutResource.getOssId());
    String contentType = getContentType(sysOssVo.getUrl());
    InputStream inputStream = sysOssService.getObjectContent(layoutResource.getOssId());
    boolean hasImage = isImage(sysOssVo.getFileName());
    if (contentType == null) {
        contentType = "application/octet-stream";
    }
    return ResponseEntity.ok()
        .header(HttpHeaders.CONTENT_DISPOSITION, hasImage ? "inline" : "attachment; filename=\""
            + java.net.URLEncoder.encode(sysOssVo.getOriginalName(),StandardCharsets.UTF_8) + "\"")
        .contentType(MediaType.parseMediaType(contentType))
        .body(new InputStreamResource(inputStream));
}

/**
 * 获取文件类型
 * @param urlString URL地址
 * @return 文件类型
 */
private String getContentType(String urlString){
    String contentType = null;
    try {
        URL url = new URL(urlString);
        URLConnection connection = url.openConnection();
        connection.setUseCaches(false);
        connection.connect();
        contentType = connection.getContentType();
    } catch (Exception e) {
        e.printStackTrace();
    }
    return contentType;
}