What you want to achieve, regardless of the environment you are in and technology you are using, is fine-grained access control / authorization.
The way to do that is to use authorization frameworks. Spring Security has one for instance. I'm not sure whether Vaadin comes with anything.
In our company we use Vaadin to develop a management portal and we then use XACML to apply fine-grained decisions to the portal such as which functions to enable for which users and even which items to display in a Vaadin table.
Generally speaking you want to look at the field of attribute-based access control (NIST ABAC). ABAC lets you define authorization constraints based on different factors/parameters such as user attributes (location, department, role...) and resource attributes (where the resource can be data, widgets, functions... You name it).
I actually delivered a webinar yesterday on the topic of fine-grained authorization for Java MVC apps. I think it could prove useful for you.
If you go down the XACML path, you do not need to create a custom database with the information inside as you have done. All you need to do is write authorization policies e.g. a user in purchasing can use the purchasing functions.
There are several open source XACML implementations as well as vendor solutions such as the one I work for, Axiomatics.
I hope this helps. I've also written a lengthier answer here which covers the broader field of authorization.