When using Undertow as named Java 9 modules, there currently is a mandatory dependence to the java.sql module due to a specific log handler and exposure of SQLException in a few signatures of UndertowLogger. By not exposing that exception type, that dependence can be made optional (requires static java.sql in terms of the module descriptor), resulting in smaller sizes of modular runtime images containing Undertow, if the JDBC-based log handler isn't used.