Hello,
I'm getting the following error with version 6.0.0, Vaadin 23.3.x, under a WildFly JEE8 environment:
HV000074: org.vaadin.stefan.fullcalendar.NotNull contains Constraint annotation, but does not contain a message parameter.
Seems that Hibernate Validator (6.0) does not like the way this annotation is declared because it's missing the `message`, `groups` and `payload` parameters.
In my case the error occurs at initialization if there are any classes extending `Entry`.