عرض عملي: الإسقاطات لقوائم مرقّمة

خطوة بخطوة

1. Define ProductListItem (id, name, price, category name).
2. Write one @Query with optional name, category, and price-range filters and a Pageable parameter.
3. Call it from the service with PageRequest.of(page, size, Sort.by("name")).
4. Planned mistake: return the entity from the controller; show the extra columns and lazy-loading trouble, then switch to the projection.
5. Check the SQL log: only the listed columns are selected, plus a count query.