code: private String getFinalPath(String uploadPath) {
  		if (uploadPath == null) {
  			throw new IllegalArgumentException("uploadPath can not be null.");
  		}
  		
  		uploadPath = uploadPath.trim();
  		if (uploadPath.startsWith("/") || uploadPath.startsWith("\\")) {
  			if (baseUploadPath.equals("/")) {
  				return uploadPath;
  			} else {
  				return baseUploadPath + uploadPath;
  			}
  		} else {
  			return baseUploadPath + File.separator + uploadPath;
  		}
  	}
docs: 路径允许为 "" 值，表示直接使用基础路径 baseUploadPath