Cracking the Spring Data JPA Interview: Tips and Must-Know Questions

Cracking the Spring Data JPA 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. How do Spring application events work with @EventListener?

    OrderService publishes OrderCreatedEvent after save. EmailListener @EventListener sends confirmation. @TransactionalEventListener(AFTER_COMMIT) prevents email on rolled-back...

    Full answer

  2. Lazy vs eager fetching in JPA — trade-offs?

    Default associations LAZY. Service method needing orders+items uses JOIN FETCH in repository query. Disable spring.jpa.open-in-view=false — forces explicit fetch in service...

    Full answer

  3. When use @Query native SQL vs JPQL in Spring Data JPA?

    JPQL for standard entity fetches and portable logic. Native for PostgreSQL-specific jsonb queries, recursive CTEs, or performance-tuned index hints after EXPLAIN. Interface...

    Full answer

  4. What are Spring Boot starters?

    spring-boot-starter-web brings spring-webmvc, Tomcat, Jackson with tested versions and enables WebMvcAutoConfiguration. You declare one starter instead of 10 coordinates....

    Full answer

  5. IdentityHashMap vs HashMap — when would you use IdentityHashMap?

    Use when identity matters not value — tracking object visitation in deep graph walk. Business keys (userId, email) belong in HashMap with proper equals/hashCode....

    Full answer

  6. 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...

    Full answer

  7. How do JPA Specifications (Criteria API) help dynamic queries?

    UserSearchSpec.withStatus(status).and(withNameLike(name)) — repository.findAll(spec, pageable). Criteria API verbose — wrap in static factory methods. Alternative: Querydsl or...

    Full answer

  8. How does @Transactional work?

    Spring creates a proxy around @Transactional beans. Calling createOrder() from another bean starts a transaction on the thread-bound EntityManager; commit on success, rollback...

    Full answer

  9. How do you handle exceptions globally in Spring?

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

    Full answer

  10. What is the difference between JPA and Hibernate?

    JPA is the API contract; Hibernate is the engine under Spring Boot by default. You write @Entity per JPA spec; Hibernate handles SQL generation. Spring Data JpaRepository adds...

    Full answer

  11. 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...

    Full answer

  12. What changed migrating Spring Boot 2 to Spring Boot 3 (Jakarta EE)?

    Upgrade to Java 17+, replace imports javax.persistence → jakarta.persistence, update Spring Security config to SecurityFilterChain lambda DSL, run OpenRewrite migration recipe,...

    Full answer

Spring Data JPA Interview Questions and Answers · Top 50 Spring Data JPA Interview Questions and Answers (2026 Edition) · Top 40 Spring Data JPA Interview Questions | Must-Prepare before interview. · Spring Data JPA Interview Questions Every Fresher Must Know

All interview question lists · Interview guides · Home · Support the platform