the request doesn't contain a multipart/form-data or multipart/mixed stream, content type header is application/x-www-form-urlencoded;charset=UTF-8

the request doesn't contain a multipart/form-data or multipart/mixed stream, content type header is application/x-www-form-urlencoded;charset=UTF-8

This exception  appears when you want to make upload on your from.

To resolve this problem you must add in your commnadbutton this attribute ajax="false".

and enctype="multipart/form-data" on your form.
Like this:
<h:form enctype="multipart/form-data">