Check the version from your spring-boot-starter-parent dependency.
If you are using an older version than 2.1.5.RELEASE, its possible that you are using the embedded mysql-connector which is an old version and contains a bug!
Upgrade your spring-boot dependency to the current release or just to 2.1.5.RELEASE which contains the newer version of the mysql-connector.
So you don't need to add params to your jdbc-url, it's a bug in the mysql-connector.
Have fun, take a coffee and chill again :)