Using two forms is the simplest way to do this.
Thanks, I know it, but I dont know how to disable validation. When sumbiting first button, I would like to validate field via medatadata (@NotNull), but when I click on the second button (on same form) I would like to call listener action without validation.
@NotNull doesn't really work (see the Seam Problems FAQ on the wiki).
It's hard to disable validation depending on which button is pressed using the standard JSF/Seam validation stuff. You would need to cook up your own solution, or, as I mentioned, use two forms.
This is a general JSF thing. You can do this:
<h:commandButton immediate="true" onclick="bCancel=true" value="Upload Attachment"/>