That works for our tests for a database/driver that supports JDBC CallableStatement API, as per this link. These tests are public, and anybody can contribute to them, just like they can the code (not that 99% of users get what "open source" is).

Since you don't define what is your database, JDBC driver, version of DataNucleus, what you've tried, what happened ("did not work" strangely doesn't explain much there), what your stored proc is, then there is nothing more to say.