Question 1

What is Hibernate and how does it work as an ORM tool?

Accepted Answer

Hibernate is a Java-based ORM framework that maps Java objects to database tables. It abstracts the database interactions, allowing developers to manipulate data via Java objects instead of SQL queries.

Question 2

Explain first-level and second-level caching in Hibernate.

Accepted Answer

First-level caching is session-scoped and is enabled by default. Second-level caching is session factory-scoped and must be configured explicitly using cache providers like EHCache or Infinispan.

Question 3

How does Hibernate manage transactions?

Accepted Answer

Hibernate uses database transactions via `Transaction` API. Transactions should be explicitly begun and committed or rolled back for data integrity and consistency.

Question 4

What is the difference between eager and lazy fetching in Hibernate?

Accepted Answer

Eager fetching retrieves associated entities immediately with the main entity, while lazy fetching delays the loading until the association is accessed. Lazy is preferred for performance unless associations are always needed.

Question 5

How do you improve Hibernate performance?

Accepted Answer

Performance can be improved using batching, caching, appropriate fetching strategies, indexing, and query optimization. Avoiding N+1 select problems is critical for efficient data access.

Question 6

Explain the difference between `get()` and `load()` in Hibernate.

Accepted Answer

`get()` loads the object immediately and returns null if not found. `load()` returns a proxy and throws ObjectNotFoundException if the object doesn't exist when accessed.

Question 7

What are the different states of an entity in Hibernate?

Accepted Answer

Transient (new, not associated with session), Persistent (managed by session), Detached (previously persistent, session closed), Removed (scheduled for deletion).

Question 8

What is the purpose of the `@Version` annotation?

Accepted Answer

`@Version` enables optimistic locking. Hibernate checks the version field during updates to prevent lost updates.

Question 9

What is the difference between `save()` and `persist()`?

Accepted Answer

`save()` returns the generated identifier and can be called outside transaction. `persist()` is JPA-specified, returns void, and must be within transaction.

Question 10

What is a query cache in Hibernate?

Accepted Answer

Query cache caches the results of queries (list of identifiers) rather than entities. It requires second-level cache to be enabled and the cacheable flag on queries.

Hibernate Interview Questions & Answers

What is Hibernate and how does it work as an ORM tool?

Explain first-level and second-level caching in Hibernate.

How does Hibernate manage transactions?

What is the difference between eager and lazy fetching in Hibernate?

How do you improve Hibernate performance?

Explain the difference between `get()` and `load()` in Hibernate.

What are the different states of an entity in Hibernate?

What is the purpose of the `@Version` annotation?

What is the difference between `save()` and `persist()`?

What is a query cache in Hibernate?

How do you configure second-level cache with EHCache?

How does Hibernate handle cache concurrency strategies?

What is the difference between `flush()` and `commit()`?

What are the transaction isolation levels in Hibernate?

How do you handle transactions in Spring with Hibernate?

What is the difference between `JOIN FETCH` and `@EntityGraph`?

How do you solve the N+1 select problem?

What is the purpose of `@Fetch` annotation?

What is the difference between `StatelessSession` and regular session?

How does Hibernate's `hibernate.jdbc.batch_size` improve performance?

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