AFAIK Redash doesn’t have any JDBC connectors. The back-end is all Python and it uses ODBC in most places. You can still write a query runner for this, but you’ll need to hack it yourself since there isn’t any JDBC prior art.
There is this older post on the forum about implementing a new query runner. As long as you can use your JDBC driver from Python then it should work. I don’t know enough about JDBC to say if that’s quite possible though