عرض عملي: مفاجآت التسلسل وحذف اليتامى

خطوة بخطوة

1. Remove one line from the order's list and commit; the log shows a delete for that line only.
2. Replace the whole list with order.setLines(newList) and show the orphan-removal error ("collection was no longer referenced") and why to mutate the same collection.
3. Planned mistake: put CascadeType.ALL on OrderLine.product; delete an order and watch it try to delete a product used elsewhere (constraint error).
4. Remove the cascade and show the order deletes alone.
5. Summarize: cascade only parent-to-owned-children.