The JDBC URL required for Sponge’s SQLService is completely different from what can be done with ConnectionConfiguration:

A jdbc connection url is expected to be of the following form or an alias (available aliases are known only by the service provider):
jdbc:<engine>://[<username>[:<password>]@]<host>/<database>

This problem must be solved, e.g. by making ConnectionConfiguration an interface that is implemented on a platform level.