Hi, change your trigger as following(add a "if :NEW.STUDENT_ID is null " statement, then when hibernate increasing the sequence by 1, oracle trigger will not do it again, but other application can still use the trigger to get a increasing by 1 ID
):
CREATE OR REPLACE TRIGGER TRG_STUDENT_INSERT BEFORE INSERT ON STUDENT
FOR EACH ROW
BEGIN
if :NEW.STUDENT_ID is null
then SELECT STUDENT_SEQ.NEXTVAL INTO :NEW.STUDENT_ID FROM DUAL;
end if;
END;