Top 50+ Hibernate Interview Questions and Answers for 2023

Top 50 most commonly asked Hibernate interview questions along with example answers:

Other Technical Interview Questions and Answers

👉 Top 50 most asked interview questions and answers with examples

1. What is Hibernate, and how does it differ from JDBC?

   - Hibernate is an Object-Relational Mapping (ORM) framework for Java that simplifies database operations by mapping Java objects to database tables. Unlike JDBC, Hibernate abstracts the low-level database interactions, making it more convenient for developers.

2. Explain the main benefits of using Hibernate.

   - Hibernate offers benefits such as automatic table creation, portability across databases, efficient caching, and simplified object-oriented programming. It also reduces the amount of boilerplate code for database access.

3. What are the core interfaces of Hibernate?

   - Hibernate's core interfaces include

Session,SessionFactory,Configuration, and Transaction.

4. How do you configure Hibernate in a Java application?

   - Example Answer: "Hibernate configuration is typically done using a hibernate.cfg.xml file, which includes database connection properties, mapping information, and other settings. This file is loaded during the initialization of a SessionFactory."

5. What is the purpose of the Hibernate SessionFactory?

   - Example Answer: "The SessionFactory is used to create and manage Session instances. It's a heavyweight object and typically created only once during the application's lifecycle to optimize performance."

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6. Explain the difference between a transient, persistent, and detached object in Hibernate.

   - Example Answer: "A transient object is not associated with any Session or database. A persistent object is associated with a Session and is being tracked for changes. A detached object was once associated with a Session but has since become disconnected."

7. How do you map a Java class to a database table in Hibernate?

   - Example Answer: "You can use Hibernate annotations or XML mapping files to define the mapping between Java classes and database tables. Annotations are typically preferred as they provide a more concise and readable approach."

8. What is lazy loading in Hibernate, and why is it important?

   - Example Answer: "Lazy loading is a feature that loads associated objects from the database only when they are accessed. This improves performance by reducing unnecessary data retrieval."

9. Explain the different fetching strategies in Hibernate.

   - Example Answer: "Hibernate supports various fetching strategies, including eager fetching (loads all related objects upfront), lazy fetching (loads objects on-demand), and subselect fetching (uses a separate SQL query for each association)."

10. How do you define a one-to-many relationship in Hibernate?

- Example Answer: "You can define a one-to-many relationship in Hibernate by using annotations like

@OneToMany and @ManyToOne to establish the association between entities. For example, a Department may have a one-to-many relationship with

Employee ."

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11. What is the purpose of the Hibernate HQL

(Hibernate Query Language)?

- Example Answer: "HQL is a query language for Hibernate that allows you to retrieve objects from the database using object-oriented syntax, rather than writing raw SQL queries."

12. How do you perform transactions in Hibernate?

- Example Answer: "Hibernate provides transaction management through the Transaction API. You can use begin , commit. , and rollback methods to manage transactions."

13. What is a second-level cache in Hibernate, and how is it configured?

- Example Answer: "The second-level cache in Hibernate is used to cache objects at the SessionFactory level, providing a shared cache for multiple Session instances. It can be configured in

hibernate.cfg.xml using cache providers like Ehcache or Infinispan."

14. What is the purpose of the Hibernate Criteria

API?

- Example Answer: "The Criteria API in Hibernate is used to build and execute queries on persistent objects. It provides a programmatic, type-safe, and object-oriented way to create queries."

15. Explain the difference between save ,saveOrUpdate , and persist methods in Hibernate.

- Example Answer: "The save method is used to save an object to the database, generating an identifier.

saveOrUpdate is used to save or update an object depending on whether it already exists in the database.

persist is similar to save , but it doesn't return the generated identifier."

16. What is the purpose of the @JoinColumn annotation in Hibernate?

   - Example Answer: "The @JoinColumn annotation is used to specify the column in the owning side of a relationship that maps to the primary key column of the referenced (target) entity. It allows you to customize the foreign key column's name and other properties."

17. Explain the concept of a composite primary key in Hibernate.

   - Example Answer: "A composite primary key in Hibernate is a primary key made up of multiple columns. It's used to uniquely identify a row in a database table when a single column primary key is insufficient."

18. What is a Hibernate mapping file, and how is it configured?

   - Example Answer: "A Hibernate mapping file is an XML file that defines the mapping between Java classes and database tables. It specifies the class, properties, associations, and other metadata. Mapping files are typically configured in the

hibernate.cfg.xml

file."

19. What is the purpose of the @Transient annotation in Hibernate?

   - Example Answer: "The @Transient annotation is used to indicate that a field or property in an entity should not be persisted to the database. It's often used for calculated or derived values that don't need to be stored."

20. Explain the differences between Session.get() and

Session.load() methods in Hibernate.

   - Example Answer: "The Session.get() method retrieves an object from the database and returns null

if the object doesn't exist. In contrast,

Session.load() returns a proxy object without hitting the database immediately; it throws an exception only when you access the proxy."

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21. What is a named query in Hibernate, and how is it defined?

   - Example Answer: "A named query in Hibernate is a pre-defined query that can be named and executed later. Named queries can be defined in the Hibernate mapping files or using annotations, making them reusable across different parts of the application."

22. What is the purpose of the cascade attribute in Hibernate associations?

   - Example Answer: "The cascade attribute defines the actions that should be cascaded from one entity to another in a parent-child relationship. For example, if you set cascade = CascadeType.PERSIST , when you persist the parent entity, the child entities will also be persisted."

23. How do you implement a many-to-many relationship in Hibernate?

   - Example Answer: "To implement a many-to-many relationship, you can use the @ManyToMany

annotation in Hibernate, specifying the association between two entities. For instance, a Student entity may have a many-to-many relationship with a Course entity."

24. Explain the purpose of the hibernate.hbm2ddl.auto

property.

   - Example Answer: "The hibernate.hbm2ddl.auto property is used to automatically generate and update the database schema based on the Hibernate mapping files. Values like create, update , and validate control how the schema is managed."

25. What is the difference between the first-level cache and the second-level cache in Hibernate?

   - Example Answer: "The first-level cache, also known as the session cache, is associated with a single Hibernate Session and stores objects during a session's lifecycle. The second-level cache is shared across multiple sessions and caches data at the

SessionFactory level."

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26. How do you handle transactions in a Hibernate application?

   - Example Answer: "Transactions in Hibernate are managed using the Session and Transaction

API. You can begin, commit, or rollback transactions 

using these objects to ensure data consistency."

27. What is the purpose of the @GeneratedValue

annotation in Hibernate?

- Example Answer: "The @GeneratedValue

annotation is used to specify how primary key values are generated. It can be combined with

@Id to automatically generate primary key values, and it supports strategies like IDENTITY,SEQUENCE, and TABLE."

28. Explain the N+1 select problem in Hibernate. How can it be mitigated?

   - Example Answer: "The N+1

select problem occurs when Hibernate issues N+1

SQL queries to fetch N entities and their associated collections, resulting in a performance issue. It can be mitigated using techniques like eager fetching, batch fetching, and caching."

29. What is the purpose of the Session.clear()

method in Hibernate?

   - Example Answer: "The Session.clear() method is used to detach all objects from a session, effectively clearing the first-level cache. This can be useful when you want to release memory or start fresh within a session."

30. How do you perform pagination in Hibernate?

   - Example Answer: "Pagination in Hibernate is typically achieved using the setFirstResult() and setMaxResults()

methods in a query. These methods allow you to specify the starting row and the maximum number of rows to retrieve."

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