Action File Upload Interceptor allowedTypes/allowedExtensions

Hi,
while I know the way of setting
	<param name=3D"actionFileUpload.allowedTypes">application/pdf</param>
	<param name=3D"actionFileUpload.allowedExtensions">.pdf</param>
in struts.xml, I am looking for a way to do that in a more flexible way fr=
om my action.

	<param name=3D"actionFileUpload.allowedTypes">${acceptedFileTypes}</param=
>
	<param name=3D"actionFileUpload.allowedExtensions">${acceptedFileExtensio=
ns}</param>
does not work (due to TextParseUtil.commaDelimitedStringToSet in ActractFi=
leUploadInterceptor).

https://struts.apache.org/core-developers/action-file-upload mentions:
>>
Programmatically limiting the file type means using the information passed=
 in to your Action class via the setXContentType(String contentType) metho=
d.=20
<<
Any advice how to use this "setXContentType" method? Can not find this met=
hod in struts7 core source.

Or any better idea to set allowedTypes and allowedExtensions from my actio=
n?
(other than to write a custom interceptor)

I also used <s:file accepted=3D${acceptedFileTypes}
but the focus of my application is more on the extensions.
The upload with struts must match the application's parallel batch import =
function (without struts).

Best regards
Ute