Hibernate Interview Questions- Part 2

Hibernate Interview Questions- Part 2
Hibernate remains a powerhouse in Java-based applications, providing seamless object-relational mapping and database interactions with minimal fuss. Whether you’re aiming for a backend developer role or a full-stack position, having a solid grip on Hibernate can tip the scales in your favor.

This guide compiles some of the most commonly asked Hibernate interview questions—ranging from basic concepts to more advanced configurations—to help you speak confidently and think on your feet during interviews. With clear, concise answers and practical examples, you’ll not only review what you already know but also discover new facets of Hibernate’s capabilities. Time to turn preparation into performance.

Answer:

A Session is an object that maintains the connection between the database & Java object application. It contains methods for modifying, storing, deleting, or retrieving data from the database using methods such as load(), persist(), update(), get(), delete(), etc. A Session also includes the factory methods to return Criteria, Query, and transaction objects.

Answer:

SessionFactory refers to a factory class used to get the Session objects. It is a heavyweight object; therefore, it is created during the application startup & kept for later use. The SessionFactory is a thread-safe object used by all the application’s threads. In the case of using multiple databases, you need to create multiple SessionFactory objects.

Answer:

The difference between openSession & getCurrentSession is:

Parameter openSession getCurrentSession
Session object The openSession method always creates a new Session object. The getCurrentSession only creates a new Session if not exists; otherwise, it uses the same Session, which is in the current Hibernate context.
Flush & close You have to flush & close session objects in the openSession explicitly. There is no need to flush & close session objects in getCuttentSession as it is automatically taken care of by the Hibernate internally.
Performance In a single-threaded environment, the openSession is slower than the getCurrentSession. In a single-threaded environment, getCurrentSesstion is faster than the getOpenSession.
Configuration There is no need to configure any property to call the openSession method. You need to configure an additional property of “hibernate.current_session_context_class” to call getCurrentSession method, else it will throw exceptions.

Answer:

The Hibernate Configuration File is one of the most in-demand configuration files in Hibernate. This file is placed by default under the src/main/resource folder. It contains database & session-related configurations. Hibernate provides the configuration either in an XML file or as a properties file.

The Hibernate Configuration file is used to define the following:

  • Details of database connection such as URL, Driver class, password & username.
  • There should be at least one configuration file for a database used in an application. So, if you want to connect with two databases, you need to create two configuration files with different names.
  • Hibernate properties including; Dialect, show SQL, second-level cache, & mapping file names.

Answer:

Hibernate configuration provides two key components, namely:

  • Database Connection: It is handled by one or more than one configuration file. Such files are hibernate.cfg.xml & hibernate.properties.
  • Class Mapping setup: This component helps to create the connection between database tables & Java classes.

Answer:

Following are the five collection types in Hibernate used for One-to-Many relationship mapping:

  • Bag
  • Set
  • List
  • Array
  • Map

Answer:

HibernateTemplate is known as the helper class that simplifies the data access code. It automatically converts HibernateExceptions, a checked exception, into DataAccessExceptions, an unchecked exception. HibernateTemplate is mostly used to implement business logic services or data access.

Answer:

Below are the key benefits of HibernateTemplate:

  • Automated Session closing ability.
  • Simplified interaction with the Hibernate Session.
  • Automated Exception handling.
  • The common functions are streamlined to single-method calls.

Answer:

Here are some design patterns used in Hibernate Framework, namely:

  • Domain Model Pattern: It is an object model of a domain that incorporates both behaviour & data.
  • Data Mapper: It is a layer of the map that moves data between objects & the database while keeping them independent of each other & the map itself.
  • Proxy Pattern: It is used for lazy loading.
  • Factory Pattern: It is used in the Session Factory.

Answer:

Hibernate Validator Framework provides the reference implementation of the bean validation specs. It is intended to implement multi-layered data validation, wherein the constraints are expressed in a single place & checked in several different layers of an application.

Answer:

Dirty Checking is a feature of Hibernate that enables developers to avoid any time-consuming write actions; thus, it helps to reduce database write times. Dirty Checking feature changes or updates the fields that require actions while keeping the rest of the fields unchanged.

Answer:

Light Object Mapping is one of the most valuable levels of Object-relational mapping quality. It uses special design patterns to hide the syntax from the business logic. All entities are represented as classes & mapped manually. This approach works well with applications that have fewer applications & entities that use metadata-driven data models.

Answer:

Optimizing the performance of an application is called Hibernate tuning. The performance tuning strategies for Hibernate are as follows:

  • Session Management
  • SQL Optimization
  • Data Caching

Answer:

Transaction management is easy in Hibernate as most operations are not permitted outside the transactions. After getting a session from the SessionFactory, one can call the session through the beginTransaction() to start the transaction. It returns the Transaction reference that can be used later to either rollback or commit the transaction. Hibernate transaction management is better as compared to JDBC transaction management as it eliminates the need to rely on exceptions for rollbacks. Thus, an exception thrown by the session method automatically rolls back the transaction.

Answer:

Mapping a primary key column by using Hibernate is quite simple. You need to add an attribute to your entity, ensure that its type & name match the database column & annotate it with @Column. Thereby, you can use that primary key to load an entity. Hibernate will then set a primary key value automatically. In case you want to persist a new entity, you’ll have to set the primary key value programmatically.

Answer:

The Query Cache refers to a separate cache that only stores the query results. Conceptually, it looks similar to a hash map, wherein a key is composed through the query text & parameter values. Here, the value is a list of entity IDs that match the query. The query cache is primarily responsible for caching the results of queries.

Answer:

Hibernate provides an option to execute Native SQL queries by using the SQLQuery object. It helps to support special database features through SQL’s dialect that the HQL does not support.

Answer:

The Named Query in Hibernate helps to group queries at a central location rather than letting them scattered across the code. The syntax of Named Query is checked while creating a Hibernate session factory. It makes an application fail fast if there are any errors in the named queries. Hibernate Named Query is global; hence, once defined, it can be used throughout the application. A significant disadvantage of Named SQL Query is that it is hard to debug as you need to find the location of the definition.
In Hibernate; we can use @NameQueries & @NameQuery annotations:

  • @NameQueries annotation is used to define multiple named queries.
  • @NameQuery annotation is used to define a single-named query.

Answer:

    • update(): You should use update() if you’re sure that the Hibernate Session doesn’t consist of an already persistent instance with the same ID.
    • merge(): You should use merge() to merge your modifications at any time without considering the state of a Session.

Answer:

A Session refers to a single-threaded, short-lived object that renders the first-level cache. On the other hand, a SessionFactory is immutable & shared by all the Sessions. It provides the second-level cache and lives until the runtime of Hibernate.