عرض عملي: مراقبة سياق الاستمرارية عبر تسجيل SQL

خطوة بخطوة

1. Enable spring.jpa.show-sql (or logging.level.org.hibernate.SQL=DEBUG) in a throwaway sandbox project.
2. Call find twice for the same id inside one transaction; count the selects (one).
3. Change a field on the loaded entity and print a marker line before the transaction ends; show the update appears after the marker, at commit.
4. Planned mistake: call find outside any transaction and change a field; show nothing is saved, then add a transaction.
5. Summarize: identity map avoided a query, unit of work delayed the update.