Top 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.
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Here's what we'll cover in this article:
- Hibernate Interview Questions and Answers for Experienced Developers
- Sample Java Hibernate Interview Questions for Practice
- FAQs on Hibernate Interview Questions and Answers for Experienced Professionals
Hibernate Interview Questions and Answers for Experienced Developers
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?
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?
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?
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?
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 is HQL?
HQL stands for Hibernate Query Language. It serves as an extension of SQL. It is straightforward and very flexible. Using HQL, a developer need not write complicated queries. It is used for performing complex operations on relational databases. HQL is the object-oriented query language that uses the Query interface of Hibernate. So, you will be using a class name instead of a table name. Thus, the language is independent of any database.
Q6. 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.
Q7. How are one-to-many associations different from many-to-many associations?
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.
Recommended Reading: Most Frequently Asked Hibernate Interview Questions With Answers
Q8. Can we define an entity class final in Hibernate?
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 cant be extended. As a result, lazy loading won't be supported.
Q9. What is a polymorphic association?
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.
Q10. What are concurrency strategies in Hibernate?
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 cause 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.
Q12. What practices would you follow to avoid SQL Injection attacks?
The following practices help avoid SQL Injection attacks:
- Using stored procedures
- Using pre-prepared statements that employ parameterized queries
- Performing input sanitation
Q13. What is JMX in Hibernate?
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.
Q14. How would you bind a hibernate session factory to JNDI?
You can bind the SessionFactory to JNDI using the values of hibernate.jndi.url, hibernate.jndi.class to instantiate an initial context.
Q15. What do you understand about the Hibernate QBC API?
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.
Q16. What is the role of the 'evict' method in Hibernate?
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.
Q17. What are Hibernate's callback interfaces?
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.
Sample Java Hibernate Interview Questions for Practice
Practicing the following Java Hibernate interview questions for experienced professionals will help you get familiar with the most anticipated Hibernate developer questions.
- Does Hibernate support Native SQL Queries?
- What happens when the Entity bean lacks the no-args constructor?
- What do you understand about the states of a persistent entity?
- What is Query Cache in Java Hibernate?
- What do you understand about the N+1 SELECT problem in Hibernate?
- How would you solve the N+1 SELECT problem?
- What is the role of the session.lock() method?
- What is Hibernate caching?
- What is the role of the merge() method in Hibernate?
- What is the difference between setMaxResults() and setFetchSize() of Query?
- What is a Single Table Strategy?
- What is the Table Per Class Strategy?
- What is the Table per Concrete Class in Hibernate?
- What is light object mapping in Hibernate?
- What do you understand by version property and derived property in Hibernate?
- What are the benefits of NamedQuery?
- What is the use of projection in Hibernate?
- How would you implement joins in Hibernate?
This completes the list of the most commonly asked Hibernate interview questions and answers for experienced professionals. You must practice these and enroll in a few mock interviews to get familiar with technical interviews and obtain experts' recommendations on your interview preparation.
FAQs on Hibernate Interview Questions and Answers for Experienced Professionals
Q1. Is Hibernate important for backend developers?
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 interview questions for experienced developers?
Lazy loading is one of the most frequently asked Hibernate interview questions and answers for experienced professionals. 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?
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?
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?
The average salary of a Hibernate developer is $120,000/year or $61.54/hour in the United States. While entry-level positions begin at $97,500/year, experienced professionals can earn up to $150,000/year (Source: talent.com).
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