Cracking the Spring MVC Interview: Tips and Must-Know Questions

Cracking the Spring MVC Interview: Tips and Must-Know Questions Work through these 12 questions out loud. Open any question for the full model answer, the trap to avoid, and the follow-up a panel usually asks.

  1. What is the N+1 query problem and how do you fix it?

    Loading 100 orders then accessing each order's items triggers 101 queries. Fix with JOIN FETCH in JPQL, @EntityGraph on repository method, or a DTO query selecting only...

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  2. How do you handle exceptions globally in Spring?

    Create @RestControllerAdvice with @ExceptionHandler(MethodArgumentNotValidException.class) returning 400 + field map, NotFoundException → 404, generic Exception → 500 without...

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  3. How do you test Spring Boot applications?

    Unit test services with Mockito — no Spring. @WebMvcTest + MockMvc for controller contract. @DataJpaTest for repository queries. @SpringBootTest + Testcontainers for critical...

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  4. How configure CORS correctly in Spring Security 6?

    CorsConfiguration config = new CorsConfiguration(); config.setAllowedOrigins(List.of("https://app.example.com")); config.setAllowedMethods(List.of("GET","POST"));...

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  5. How does Spring Boot auto-configuration work?

    @SpringBootApplication enables @EnableAutoConfiguration, which loads candidate configs from starters. Each auto-config uses @ConditionalOn* to register beans only when...

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  6. Describe the Spring Bean lifecycle.

    Container instantiates the bean, injects dependencies, runs BeanPostProcessors, then @PostConstruct or InitializingBean. Singleton lives for context lifetime; prototype creates...

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  7. @RestController vs @Controller?

    @Controller is for traditional MVC — return "user/list" view name. @RestController adds @ResponseBody so return types become JSON/XML body — standard for REST APIs. Use...

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  8. springdoc-openapi vs legacy springfox — what should new projects use?

    Add springdoc-openapi-starter-webmvc-ui dependency. Annotate with @Operation, @Schema on DTOs. Disable in prod via springdoc.api-docs.enabled=false or secure endpoint. Generate...

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  9. Best practices for Spring Data pagination with Pageable?

    Controller: @PageableDefault(size=20, sort="createdAt", direction=DESC) Pageable p. Cap size at 100. Admin reports: keyset pagination on id > lastId for deep pages — OFFSET...

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  10. What are common mistakes freshers make in Spring Boot projects?

    ```java // ❌ Wrong @RestController public class OrderController { @PostMapping("/orders") public Order create(@RequestBody Order o) { return orderRepository.save(o); // DB in...

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  11. What is AiServices, and why is it better than calling chat.completions() from a controller?

    AiServices is a typed facade over ChatLanguageModel. I declare TicketAssistant with @SystemMessage and @UserMessage, register it as a singleton @Bean, and the controller never...

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  12. What happens if an exception occurs inside a filter or interceptor?

    Exceptions in `Filter` bypass `@ControllerAdvice` unless handled. Filters run before MVC. ```java @Override protected void doFilterInternal(HttpServletRequest req,...

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