Hi Marcel Stör, thanks for the issue report. Do you have any concrete wording in mind?

Also, I think we have to separate between the constraint @URL and its constraint validator implementation, in our case URLValidator. The latter is atm using the java.net.URL constructor in an attempt to implement the @URL constraint. Its limitations should imo really be documented there. Maybe we could add a note to @URL, saying that a constraint validator implementation of this constraint needs to support the 'http' protocol, but potentially could provide more.

The URLValidator documentation could then deal with the fact that in this particular case java.net.URL is used and that more protocols can be supported by installing more protocol handlers.