OrderHub Day 6: Pagination, Sorting & Filtering in Spring Boot

OrderHub Day 6: the list endpoint that returns everything is a time bomb. With 10 orders it's fine; with 10 million it OOMs the server and times out the client. Today: pagination, sorting, and filtering — done the Spring Data way.

📑 Try the paged/sorted/filtered list: https://dev48v.infy.uk/orderhub/day6-pagination.html

Pageable + Page

Spring Data hands you this almost for free. The controller accepts a Pageable, so GET /orders?page=1&size=20&sort=createdAt,desc is parsed automatically; the repository returns a Page<Order> — a slice of content plus metadata (totalElements, totalPages, number).

@GetMapping
PagedResponse<OrderResponse> list(
    @RequestParam(required=false) String status,
    @PageableDefault(size=20, sort="createdAt") Pageable pageable) { ... }

Filtering behind the port

OrderHub keeps its repository port abstraction: I added search(status, pageable) to the interface and implemented it in both backends — a derived findByStatus(status, pageable) for JPA, and a manual filter+sort+slice for the in-memory one. The service and controller don't care which is active.

Three production habits

• Cap the page size (@PageableDefault + a max) so nobody requests size=1000000 — a cheap DoS.
• Return DTOs, not entities, even in a page.
• Know that offset paging gets slow deep in huge tables — keyset/cursor paging scales better (a later day).

🔨 Full walkthrough (Pageable → Page → @PageableDefault → findByStatus → PagedResponse) on the page: https://dev48v.infy.uk/orderhub/day6-pagination.html

OrderHub — a production-grade Spring Boot backend, one feature a day.
🌐 https://dev48v.infy.uk · Code: https://github.com/dev48v/order-hub-from-zero