SerializablePage<T>

Package: com.toni.FoodApp.response

A lightweight serialization wrapper around Spring's Page<T> that enables paginated data to be stored and retrieved from Redis.

Why It Exists

Spring's PageImpl<T> cannot be deserialized by Jackson out of the box — it lacks a no-argument constructor and has complex internal state. SerializablePage<T> solves this by reducing a page to four plain fields that Redis can safely serialize and deserialize.

Fields

Field	Type	Description
content	List<T>	The actual list of items on this page
pageNumber	int	Zero-based page index
pageSize	int	Number of items per page
totalElements	long	Total number of items across all pages

Constructors & Methods

SerializablePage(Page<T> page)

Converts a Spring Page<T> into a serializable form before storing in Redis.

Page<RestaurantSummaryDTO> dtoPage = repository.findAll(pageable);
SerializablePage<RestaurantSummaryDTO> cached = new SerializablePage<>(dtoPage);

toSpringPage()

Reconstructs a Spring Page<T> after fetching from Redis.

SerializablePage<RestaurantSummaryDTO> cached = // fetched from Redis
Page<RestaurantSummaryDTO> page = cached.toSpringPage();

Round Trip

Database
   │
   ▼
PageImpl<T>  ──────────────────────►  SerializablePage<T>  ──►  Redis (JSON)
                new SerializablePage()                               │
                                                                     │
Client  ◄──  PageImpl<T>  ◄──────────────────────────────────────────
                          .toSpringPage()

Usage with @Cacheable

@Cacheable(
    value = "dashboardRestaurants",
    key = "#sort + ':' + #pageable.pageNumber + ':' + #roundedLat + ',' + #roundedLng"
)
public SerializablePage<RestaurantSummaryDTO> getCachedDashboardPage(...) {
    Page<RestaurantSummaryDTO> page = repository.findAll(pageable);
    return new SerializablePage<>(page); // wrapped before caching
}

Redis Representation

{
  "@class": "com.toni.FoodApp.response.SerializablePage",
  "content": [ ...list of DTOs... ],
  "pageNumber": 0,
  "pageSize": 10,
  "totalElements": 5
}

---

Note

• T must itself be serializable by Jackson (no unserializable Spring internals).
• The @class field is written by Jackson's polymorphic type handling and is required for correct deserialization — do not remove it from the Redis config.
• This class is not a domain object — it is purely a caching utility and should not be exposed directly in API responses.