Jaspersoft Studio - JDBC Data Adapter - specify DB schema

I have a Jaspersoft Studio Oracle JDBC data adapter defined however I come into the database as a public user - I would like to specify the default schema to be used for queries (i.e. alter session set current_schema = {schema}) however I've not found out how/where/if that is possible

suggestions or ideas?   my options to do anything outside of Jaspersoft studio (i.e in the db itself) with regards to this user are limited at best