Hibernate is a widely used object-relational mapping (ORM) framework, and if you’re interviewing for a Back-End Developer, Full-Stack Developer, or Java Developer role, there’s a good chance you’ll be asked some questions about it during your technical interview.
One of the best ways to prepare for Hibernate interview questions is to practice them before your actual interview. You can set up a mock interview with a friend or family member and have them ask you questions so you can practice answering them out loud in front of someone.
If you’re interviewing over Zoom, you may want to do your mock interview over Zoom too. That way, you’re practicing in a similar environment to the one your interview will be conducted in. You can also use Zoom on your own and record yourself answering questions. Then, when you play it back, you can have the opportunity to fine-tune your answers and mannerisms.
To help you with your interview prep, here are 15 Hibernate interview questions and tips for how to answer them.
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1. What is Hibernate?
If you’re interviewing for an internship or your first job after college, there’s a good chance you’ll be asked this question, even though it seems like an obvious question to ask. In your answer, you should point out that Hibernate is a popular framework that helps Java applications communicate with and interact with databases. Hibernate is an object-relational mapping (ORM) tool that maps an object-oriented model to a relational database.
2. What is persistence?
Persistence is the concept of storing data that gets saved in a database — or persists. One of the main functions of Hibernate is to persist changes, in a Java object’s state, to the connected database.. Classes in Java whose objects are stored in a database are called persistent classes.
3. What are some of the advantages of Hibernate?
Hibernate has a number of advantages that you can discuss in your answer to this question. You can talk about how it’s open source, so there isn’t a single company that has absolute control over Hibernate’s development. Another advantage of Hibernate is how quickly it can provide information about query statistics and database status. Also, it’s database-independent which means that it’s not dependent on a specific database management system.
4. What is HQL?
HQL stands for Hibernate Query Language. While HQL looks similar to SQL, it’s an independent query language that you can use with any database. HQL is then converted to the database’s native SQL syntax at runtime. Unlike SQL, HQL supports full object-oriented programming (OOP) capabilities.
5. What are some databases that are supported by Hibernate?
Hibernate supports a variety of databases, including MySQL, Oracle, DB2, Sybase SQL Server, Informix Dynamic Server, HSQL, PostgreSQL, and FrontBase.
6. What are three key association mappings in Hibernate?
Hibernate supports the same three basic associations as a relational database, which are:
- One-to-one associations
- One-to-many/many-to-one associations
- Many-to-many associations
7. What is a one-to-one association?
A one-to-one association is where a record in a particular database table can be linked to one and only one other record in another database table.
For example, in a database of students at a college, each student is associated with only one student ID number. At the same time, each student ID number is associated with only one student.
8. How would you create a one-to-one mapping solution in Hibernate?
There are three techniques to create a one-to-one association in Hibernate. You can create a foreign key column in one of the tables or a new table that contains the mapped values, or you can use a common primary key value in both tables.
9. What is a one-to-many association?
In a one-to-many association, a record in a database table can be linked to multiple records in another database table.
For example, consider a college database that contains information about courses and instructors. An instructor can teach multiple courses, but one course can only be linked to one instructor. This represents the one-to-many relationship, where one instructor is associated with many courses.
10. How would you create a one-to-many mapping solution in Hibernate?
In Hibernate, there are two ways to set up a one-to-many association. If we use the example of the college courses and instructors, then the first method is to create a foreign key column in the Courses table that associates each course with an instructor — the assumption is that instructors are all assigned a unique ID or number.
The second option is to create another table that contains two columns. One has a foreign key that refers to the primary key in the Courses table, and the other has a foreign key that refers to the primary key of the Instructors table.
11. What is a many-to-many association?
A many-to-many association involves records in one database table that can be linked to multiple records in another table. At the same time, a record in the first table can also be linked to multiple records in the first table.
For example, in a college database that contains student enrollment information, a single course will likely have many students enrolled. At the same time, a single student can be enrolled in multiple courses.
12. What are some major Hibernate interfaces?
Some of the important Hibernate interfaces are Configuration, SessionFactory, Session, Criteria, Query, and Transaction.
13. What is a Hibernate Session, and how do you create one?
A Session in Hibernate is an object that manages the connection between a Java object and a database. Session methods allow you to store, extract, edit, or delete information from a database.
To create a Session object in Hibernate, use the SessionFactory interface.
14. How can you make an immutable class in Hibernate?
By default, classes in Hibernate are mutable. However, you make a class immutable by marking the class as mutable = false.
15. What are the three states of a Hibernate object?
The three states of an instance or object in Hibernate are:
- Transient: The object isn’t yet associated with a Hibernate Session and has no persistent representation in the database. In other words, Hibernate isn’t yet collecting data about the object class and recording values into a database table.
- Persistent: The object is associated with a Hibernate session and has representation in the database.
- Detached: The object has been made persistent, but its associated Session has been closed. A detached object can be modified and made persistent later on if it’s associated with a new Session.
Get ready for your technical interview
If you’re looking for more ways to prepare for your upcoming interview, check out our complete guide to acing the technical interview and our tips on answering behavioral interview questions. Also, take a look at our advice for the whiteboard interview.Visit our Career Center for even more resources on interviewing and job hunting, like resume writing, networking, and creating a portfolio. If you’re looking for a class to learn a new skill or take an existing one up a notch, you can explore our full course catalog.
