在将其提供给 POI 之前您无法检查它.只需捕获 POI 在解析过程中可能抛出的异常.如果它引发异常，那么您只需向最终用户显示 FacesMessage 上传的文件不是支持的 excel 格式.

You can't check that before feeding it to POI. Just catch the exception which POI can throw during parsing. If it throws an exception then you can just show a FacesMessage to the enduser that the uploaded file is not in the supported excel format.