spring-boot

Create a @RestController with constructor-injected services, validate request bodies with @Valid, and return DTO records. Layer the application as Controller → Service → Repository, and handle errors globally with @RestControllerAdvice.

Configure a SecurityFilterChain bean with stateless sessions, add a JwtAuthenticationFilter before UsernamePasswordAuthenticationFilter, and use a JwtService to generate and validate HS256 tokens. Alternatively, configure an OAuth2 resource server with a JwtDecoder pointing to your issuer.

Constructor injection is the required pattern. It makes dependencies explicit, enables final fields, simplifies unit testing with mocks, and avoids the hidden-dependency problems of @Autowired field injection.

Use @WebMvcTest targeting your controller, mock the service layer with @MockBean, and perform requests with MockMvc verifying status codes and JSON paths. Add @WithMockUser to test security rules without real authentication.

Yes, Testcontainers runs a real PostgreSQL container during tests. Declare a @Container PostgreSQLContainer, wire its JDBC URL via @DynamicPropertySource, and run @SpringBootTest against the actual database.

Use JOIN FETCH in JPQL queries, @EntityGraph with attributePaths, or @BatchSize on collections to load associations in batches. Combine with pagination to avoid loading entire datasets into memory.