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

A bug where primary key generation fails for every Nth entity

Answer

A limitation where a session can process at most N+1 concurrent queries

Answer

A deadlock between a parent transaction and N child transactions

Question 2

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

Accepted Answer

@EnableJpaRepositories

Answer

@ScanJpaRepositories

Answer

@EnableDataRepositories

Answer

@JpaRepositoriesScan

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

To render a visual diagram of entity relationships in the admin console

Answer

To define the database schema and constraints for an entity class

Answer

To cache an entity's state across multiple transactions

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

@Query

Answer

@PredefinedQuery

Answer

@EntityQuery

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 order in which child entities are loaded from the database

Answer

The foreign key column name generated in the child table

Answer

The maximum depth of nested entity graphs that can be traversed

Question 6

What is the primary purpose of the @Version annotation in a JPA entity?

Accepted Answer

To implement optimistic locking by tracking a version field that JPA increments on each update

Answer

To record the timestamp of the entity's last modification

Answer

To specify which version of the JPA specification the entity targets

Answer

To enable versioned caching so the second-level cache can detect stale entries

Question 7

What distinguishes JPQL (Java Persistence Query Language) from standard SQL?

Accepted Answer

JPQL operates on JPA entity objects and their mapped fields rather than directly on database tables and columns

Answer

JPQL is a JSON-based query language designed for NoSQL databases

Answer

JPQL is a proprietary Spring extension of SQL that adds built-in pagination syntax

Answer

JPQL is compiled to bytecode and executed inside the JVM without any database interaction