Spring Data & JPA Flashcards

Which annotation marks a Java class as a JPA entity that can be persisted in a relational database?

Answer: @Entity

@Entity designates a Java class as a JPA entity, mapping it to a database table for persistence.

Which Spring Data interface provides the minimum set of CRUD operations for a repository?

Answer: CrudRepository

CrudRepository defines the core CRUD methods (save, findById, findAll, delete, count) that all Spring Data repositories can extend.

What does the @GeneratedValue annotation configure when used alongside @Id in a JPA entity?

Answer: The strategy used to generate primary key values

@GeneratedValue specifies the strategy (AUTO, IDENTITY, SEQUENCE, TABLE) used to automatically generate primary key values.

Which annotation is used in a Spring Data JPA repository interface to define a custom JPQL or native SQL query?

Answer: @Query

@Query allows you to define a custom JPQL or native SQL query directly on a repository method using its value or nativeQuery attributes.

What is the primary effect of applying @Transactional to a Spring service method?

Answer: The method executes within a database transaction, with automatic commit or rollback

@Transactional wraps the method in a database transaction, automatically committing on success or rolling back on exception.

How does saveAndFlush() in JpaRepository differ from save()?

Answer: It immediately synchronizes the entity state with the database within the current transaction

saveAndFlush() calls save() and then immediately flushes the persistence context, pushing changes to the database within the current transaction.

What is the return type of the findById() method defined in Spring Data's CrudRepository?

Answer: Optional

findById() returns Optional to safely handle the case where no entity with the given ID exists, avoiding NullPointerExceptions.