Hibernate Validator does not enforce the @NotNull annotation. That is taken care of by
JSF. The best way to ensure that you get per-field validation messages is to use the <s
ecorate> tag along with the layout/edit.xhtml template provided with seam-gen:
Right now, you are probably displaying them at the top of the page using <h:messages/>. Change that to <h:messages globalOnly="true"/>.
To customize JSF messages, you enter the keys in the messages*.properties files. Again, if you create a seam-gen project, you will see the keys that are in these files. Here are the two keys you want: