I generally prefer to not mess with Jasperserver internal PostgreSQL database. Mainly for security reasons – best protection for this internal database is to not open it for remote connections. Therefore I install another standard PostgreSQL installation on the same machine. It runs on the port 5433. And this one I use to access internal JS database.

You can simply use foreign data wrapper for it:

create extension postgres_fdw;
create schema jasperserver;
CREATE SERVER jasperserver FOREIGN DATA WRAPPER postgres_fdw OPTIONS (host 'localhost', dbname 'jasperserver', port '5432');
CREATE USER MAPPING FOR upcload SERVER jasperserver OPTIONS (user 'jasperdb', password 'password');
IMPORT FOREIGN SCHEMA public FROM SERVER jasperserver INTO jasperserver;