StoredProcedureQuery query = entityManager
.createStoredProcedureQuery("count_comments")
.registerStoredProcedureParameter(
    1,
    Long.class,
    ParameterMode.IN
)
.registerStoredProcedureParameter(
    2,
    Long.class,
    ParameterMode.OUT
)
.setParameter(1, 1L);
 
query.execute();
 
Long commentCount = (Long) query.getOutputParameterValue(2);

declare
  x_result number;
begin
  x_result := my_function( :param1, :param2 );
  :param3 := x_result;
end;

CREATE OR REPLACE FUNCTION fn_count_comments (
    postId IN NUMBER )
    RETURN NUMBER
IS
    commentCount NUMBER;
BEGIN
    SELECT COUNT(*) INTO commentCount
    FROM post_comment
    WHERE post_id = postId;
    RETURN( commentCount );
END;

Session session = entityManager.unwrap( Session.class );
 
Integer commentCount = session.doReturningWork(
    connection -> {
    try (CallableStatement function = connection
        .prepareCall(
            "{ ? = call fn_count_comments(?) }" )) {
        function.registerOutParameter( 1, Types.INTEGER );
        function.setInt( 2, 1 );
        function.execute();
        return function.getInt( 1 );
    }
} );