Spring Framework Spring Data & JPA 3

Question 1

What is the N+1 query problem in JPA?

Accepted Answer

A performance issue where fetching N entities triggers N additional queries to load each entity's lazy associations

Answer

The N+1 problem occurs when JPA executes 1 query to load N entities and then N additional queries to lazily load each entity's associations, causing excessive database round trips.

Question 2

Which annotation is used in a Spring configuration class to enable scanning for Spring Data JPA repositories?

Accepted Answer

@EnableJpaRepositories

Answer

@EnableJpaRepositories triggers component scanning for interfaces extending Spring Data JPA repository types and creates their bean implementations.

Question 3

What is the primary use of the @EntityGraph annotation in Spring Data JPA?

Accepted Answer

To specify which lazy associations should be eagerly fetched for a particular query

Answer

@EntityGraph overrides the default fetch plan for a specific repository query, loading specified associations eagerly to avoid N+1 problems.

Question 4

Which JPA annotation defines a named query at the entity class level that can be referenced by name in repository methods?

Accepted Answer

@NamedQuery

Answer

@NamedQuery is placed on an entity class to define a static, pre-compiled JPQL query identified by a name for later reference.

Question 5

What does the cascade attribute on a JPA relationship annotation (e.g., @OneToMany) control?

Accepted Answer

Which EntityManager lifecycle operations (persist, merge, remove, etc.) propagate from the parent to child entities

Answer

The cascade attribute determines which JPA lifecycle operations on the parent entity (such as PERSIST, MERGE, REMOVE) are automatically applied to its associated child entities.

Spring Framework Practice Test

Spring Framework Practice Test

Spring Framework Spring Data & JPA 3