spring-boot-mvc-architecture

Organize code into Controller, Mapper, Service, Repository, and Entity layers where each layer has a single responsibility. Controllers handle HTTP requests, mappers convert between DTOs and domain models, services hold business logic, and repositories manage data access via Spring Data JPA.

Use Pageable with PageRequest.of(page, size) in the repository layer, and validate inputs with value objects like BoundedPageSize that enforce a maximum page size. Convert one-based page numbers from clients to zero-based Spring Data indexes in a utility class.

JpaRepository provides standard CRUD and pagination methods, while JpaSpecificationExecutor adds support for dynamic queries using the Criteria API. For fully custom filtered queries, implement a DAO with EntityManager and CriteriaBuilder.

Create a @MappedSuperclass base entity with @CreationTimestamp and @UpdateTimestamp fields for createdAt and updatedAt, plus createdBy and updatedBy user references. Populate the user fields in the service layer from the Spring Security authentication context.

Use the crupdate pattern when clients can submit entities that may or may not already exist, identified by client-provided IDs. The service checks whether each ID exists in the database and either updates the existing record or creates a new one in a single transaction.