50 Hibernate Interview Questions for Experienced Developers

Hibernate is a skill in high demand among Java developers. The Hibernate framework aims to free Java developers from complex persistence configurations by abstractly mapping POJO objects to database tables. Top tech companies use Hibernate in their tech stacks, so they seek Java Web Developers who are well-versed in Hibernate.

We’ve listed the top advanced Hibernate interview questions and answers for experienced professionals in this article. Practicing these Hibernate interview questions and answers will help you revise the key concepts and assess your preparation for the upcoming technical interview.

Hibernate Interview Questions and Answers for Experienced Developers <h2>

Interviewers at top tech companies expect Hibernate developers to be well-prepared for Hibernate interview questions and answers for experienced professionals and basic concepts. Let’s go through some of the most common questions asked in tech interviews.

Q1. Why is Java Hibernate so popular? <h3>

The following four reasons make Java Hibernate so popular:

• Interfacing incompatible databases: Java Hibernate helps bridge the gap between incompatible databases.

• Automatic SQL query generation: Hibernate allows automatic SQL query writing and thus separates the roles of a database administrator and developer.

• It helps apps remain persistence engine agnostic, and it does not matter which database is being used.

• Resistance to SQL injection: Hibernate ORM limits the risk of SQL injection and provides a safer alternative to SQL queries.

Q2. What are fetching strategies? Which strategies do Hibernate support? <h3>

Hibernate uses a fetching strategy for retrieving associated objects when the application has to navigate the association. The strategies can be declared in the O/R mapping metadata or overridden by a particular HQL or criteria query. Hibernate supports the following fetching strategies:

• Join fetching

• Batch fetching

• Immediate fetching

• Select fetching

• Subselect fetching

• Lazy collection fetching

• "No-proxy" fetching

• "Extra-lazy" collection fetching

• Proxy fetching

• Lazy attribute fetching

Q3. What parts do Hibernate applications consist of? <h3>

This is one of the most commonly asked Hibernate interview questions and answers for experienced developers. An application developed using Hibernate consists of the following four parts:

• Java Application

• Hibernate Framework: Configuration and mapping Files

• Internal AP: JDBC (Java Database Connectivity), JTA (Java Transaction API), JNDI (Java Naming Directory Interface)

• Database - MySQL, PostgreSQL, Oracle

Q4. What are the main elements of the Hibernate framework? <h3>

Hibernate framework consists of the following main elements:

• SessionFactory: It gives a factory method to create session objects and get clients of ConnectionProvider. It is immutable and holds a second-level cache (optional) of data.

• Session: A short-lived object acting as an interface between the Java application objects and database data. It is usually used to generate query, transaction, and criteria objects. It has a first-level cache (mandatory) of data.

• Transaction: An object specifying the atomic unit of work. It has methods for transaction management and is optional.

• TransactionFactory: A factory of transaction objects. It is optional.

• ConnectionProvider: A factory of JDBC connection objects. It is optional and gives abstraction to the application from the DriverManager.

Q5. What are the most commonly used methods in query interface?

Interviewers often ask such Hibernate interview questions and answers for experienced professionals to gauge your proficiency in HQL. The following table enumerates the most commonly used methods and their functions.

Q6. How are one-to-many associations different from many-to-many associations? <h3>

The one-to-many association indicates that one object is associated with multiple objects. On the contrary, many-to-many association indicates multiple relations between the instances of two entities.

Q7. Can we define an entity class final in Hibernate? <h3>

No, we should not declare the entity class final because Hibernate employs objects for lazy loading of data and proxy classes and hits the database only if it is absolutely necessary. You can achieve the same by extending the entity bean. However, if you declare the entity class (or bean) final, then it can't be extended. As a result, lazy loading won't be supported.

Q8. What is a polymorphic association? <h3>

The term polymorphic association is used in discussions of ORM with respect to the problem of representing in the relational database domain a relationship from one class to multiple classes. In Java, these multiple classes serve as subclasses of the same superclass.

Q9. What are concurrency strategies in Hibernate? <h3>

Concurrency strategies act like mediators storing and retrieving items from the cache. The following concurrency strategies are used in Hibernate:

• Transactional: It is used for updating data that causes stale data.  

• Read-Only: It is applicable when we do not wish to modify the data. It can be used for reference data only.

• Read-Write: It allows the data to be read and is suitable when preventing stale data is critical.

• Non-strict-Read-Write: The strategy ensures that there wouldn't be any consistency between the database and cache. It is used when the data can be modified and stale data isn't of critical concern.

Q10. What practices would you follow to avoid SQL Injection attacks? <h3>

The following practices help avoid SQL Injection attacks:

• Using stored procedures

• Using pre-prepared statements that employ parameterized queries

• Performing input sanitation

Q11. What is JMX in Hibernate? <h3>

JMX or Java Management Extensions is a Java technology that provides tools for monitoring and managing applications, devices, system objects, and service-oriented networks. The resources are represented by objects referred to as Managed Beans.

Q12. How would you bind a hibernate session factory to JNDI? <h3>

You can bind the SessionFactory to JNDI using the values of hibernate.jndi.url, hibernate.jndi.class to instantiate an initial context.

Q13. What do you understand about the Hibernate QBC API? <h3>

The Hibernate QBC API stands for Hibernate Query By Criteria Application Performing Interface. It is used to create queries by manipulating criteria objects at runtime.

Q14. What is the role of the 'evict' method in Hibernate? <h3>

The evict() method in Hibernate helps detach the object from the session cache. Once the object is detached from the session, any change to the object will not be persisted.

Q15. What are Hibernate's callback interfaces? <h3>

The callback interface is used in a Hibernate application to receive a notification when an object event occurs, such as loading, saving, or deletion. It is used with HibernateTemplate's execution methods, and its implementation will call session.load/find/update to perform certain operations on persistent objects.

Also read: Hibernate Java Interview Questions for Beginners and Experienced Developers.

Hibernate Interview Questions for 3 Years Experience <h2>

These Hibernate interview questions focus on basic concepts, basic problem-solving, and working with Hibernate in ordinary application development.

Q16. What are Hibernate's callback interfaces? <h3>

The callback interface is used in a Hibernate application to receive a notification when an object event occurs, such as loading, saving, or deletion. It is used with HibernateTemplate's execution methods, and its implementation will call session.load/find/update to perform certain operations on persistent objects.

Q17. What do you understand about the states of a Hibernate persistent entity? <h3>

In Hibernate, an entity can exist in three states as follows:

• Transient: The object is not yet associated with the database.

• Persistent: The object is associated with a session; thus, the object is sure to exist in the database.

• Detached: The object was stuck there previously but is no longer bound with an active session.

Q18. What is a one-to-one relationship in Hibernate? <h3>

The @OneToOne annotation is used in Hibernate to represent a one-to-one mapping. It can be defined with optional cascade types. Besides this, the relationship can also be specified using mappedBy for bidirectional mappings or the foreign key using @JoinColumn.

Q19. What is a Hibernate transaction, and how is it handled? <h3>

In Hibernate, a transaction is a portion of database operations that should be carried out as a logical unit. It may be controlled manually via Session object (beginTransaction(), commit(), rollback() ) or declaratively using annotations on classes in frameworks, such as Spring using @Transactional.

Q20. How do you implement pagination in Hibernate?

Pagination in Hibernate is achieved by the Query or Criteria API by setting first, by first making use of the method setFirstResult() for the definition of the start point and then setMaxResults() is used to set the number of results returning in a single page.

Hibernate Interview Questions for 7 Years Experience <h2>

These Hibernate interview questions questions are related to slightly advanced topics, best practices, and common challenges that tend to emerge in mid to senior-level positions.

Q21. What is the difference between merge() and update() methods in Hibernate?

The merge() method copies the state of a detached entity into the current persistence context, returning a managed instance. This does not throw an exception if the entity is already in session. update() on the other hand re-attaches a detached entity but throws an exception if there already exists an instance of that entity in the session.

Q22. What are the best practices to avoid the N+1 problem in Hibernate?

• Use JOIN FETCH to fetch the related entities in a single query.

• The batch fetching fetches multiple related entities in as few queries as possible.

• Set up proper @FetchMode-such as FetchMode.SUBSELECT-to optimize the execution of these queries.

• Use entity graphs to control related lazy loads.

Q23. What are Hibernate annotations, and how do they differ from XML configuration?

Hibernate Annotations directly map Java classes to database tables within the Java code. While it is easier to configure and accompanied by fewer XML files, it locates the XML configuration in a separate, more verbose piece of code but does prove to be handy in having the necessity for externalized, modular configurations.

Q24. What are the types of inheritance mapping in Hibernate?

Hibernate supports three types of inheritance mappings:

• Single Table: All classes in a hierarchy are stored in one table.

• Table per Class: This has a table for each class in the hierarchy.

• Joined Strategy: A table is created for the base class and each subclass. Relationships are maintained through foreign keys.

Q25. How do you implement custom types in Hibernate using @TypeDef?

@TypeDef allows you to define custom types in Hibernate by mapping Java types to database types. To do so, you have to first create a class implementing the UserType interface, then register it with @TypeDef, and finally annotate your entity field with @Type.

Hibernate Interview Questions for 10 Years Experience <h2>

These Hibernate interview questions focus on deep architectural and performance-based aspects along with that of real-world problem-solving.

Q26. How would you handle transactions in a distributed application of Hibernate?

Java Transaction API, JTA, is the service provided for distributed applications that coordinates transactions across several resources, like databases or message queues. Hibernate integrates into this type of global transaction and provides for consistency across systems.

For such an ability you will have to configure the application server's transaction manager, and each resource must enlist with the JTA for coordinated, distributed management.

Q27. What are your strategies for debugging difficult Hibernate queries in a production environment?

To debug Hibernate queries in production:

• Enable SQL logging to view the generated SQL statements.
• Use Hibernate statistics (hibernate.generate_statistics) for cache hits, the execution time of the query, etc.
• Enable second-level cache metrics to understand cache utilization.
• Profiling tools should also be used that make JProfiler profiles at runtime. Use query plan analysis of your database to review the execution plans of tricky queries.

Q28. Describe the interaction of Hibernate with a database in ACID terms.

Hibernate fully supports ACID properties through transaction management.

• Atomicity: Hibernate, due to the transaction boundaries, provides full transactions with full execution or full rollback of a transaction.
• Consistency: Hibernate enforces database constraints that maintain data integrity.
• Isolation: Hibernate provides isolation levels based on the database transaction. They, therefore, do not affect each other wrong in concurrent transactions.
• Durability: After a transaction is committed, Hibernate guarantees that data are properly persisted in the database, relying on whatever the underlying database guarantees with respect to  durability.

Q29. Describe how you’ve tuned Hibernate to handle high-concurrency applications.

High concurrency in Hibernate is fine-tuned by:

• Configuring second-level caching to optimize the read operation on the database.
• Using optimistic locking to prevent conflicts during concurrent updates.
• Implementing batch processing and updating in bulk to call fewer queries. Optimize connection pooling and reduce session usage to avoid overhead over simultaneous requests.

Java Hibernate Interview Questions for Practice <h2>

Practicing the following Java Hibernate interview questions for experienced professionals will help you get familiar with the most anticipated Hibernate developer questions.

1. Does Hibernate support Native SQL Queries?
2. What happens when the Entity bean lacks the no-args constructor?
3. What do you understand about the states of a persistent entity?
4. What is Query Cache in Java Hibernate?
5. What do you understand about the N+1 SELECT problem in Hibernate?
6. How would you solve the N+1 SELECT problem?
7. What is the role of the session.lock() method?
8. What is Hibernate caching?
9. What is the role of the merge() method in Hibernate?
10. What is the difference between setMaxResults() and setFetchSize() of Query?
11. What is a Single Table Strategy?
12. What is the Table Per Class Strategy?
13. What is the Table per Concrete Class in Hibernate?
14. What is light object mapping in Hibernate?
15. What do you understand by version property and derived property in Hibernate?
16. What are the benefits of NamedQuery?
17. What is the use of projection in Hibernate?
18. How would you implement joins in Hibernate?
19. What is the difference between optimistic and pessimistic locking in Hibernate, and when would you use each?
20. How does Hibernate handle bidirectional relationships, and what are the potential issues with managing these associations?

FAQs on Hibernate Interview Questions and Answers for Experienced Professionals

Q1. Is Hibernate important for backend developers? <h3>

Hibernate is one of the most popular Java backend frameworks as it provides an abstraction layer for interacting with databases and allows establishing connections to implement CRUD operations.

Q2. What is lazy loading in Hibernate?<h3>

Lazy loading in Hibernate is when it does not initially load the children (child objects) along with the parent; rather, it loads children on demand. The feature improves the performance and is enabled by default in Hibernate.

Q3. Do Hibernate interview questions and answers for experienced professionals include coding? <h3>

Yes, the interviewer can ask you to explain Hibernate features through code. You should practice coding problems to ace coding interview rounds during on-site interviews at top companies.

Q4. What topics are important for Hibernate interview questions and answers for experienced developers? <h3>

You should be well versed in the following Hibernate concepts: Lazy Loading, Concurrency, SQL injection risks, fetching, annotations in Hibernate, Hibernate architecture, and APIs.

Q5. What is the average salary of a Hibernate developer in the US? <h3>

The average salary of a Hibernate developer is $120,000/yearin the United States. While entry-level positions begin at $97,500/year, experienced professionals can earn up to $150,000/year.).

Related reads:

• 40+ Technical Interview Questions Asked at Top Technology Companies