Hibernate Interview Questions and Answers

It is an ORM developed for mapping tool for Java application program. It has been used in the development of Java application program as the primary function of Hibernate ORM is mapping the classes to the database tables and the types of Java data to SQL data types.

Other uses are-

• Retrieving the data results
• Writing data queries
• Solves the problems of the mismatch of the traditional object and relational impedance issue

Hibernate is a popular Java-based framework for developing persistent data storage solutions, and it offers several benefits:

• Simplifies database operations: Hibernate eliminates the need for manual data handling and reduces the complexity of database operations by providing a high-level API for working with data.
• Increases developer productivity: Hibernate abstracts away the underlying database technology, allowing developers to focus on the business logic rather than writing low-level SQL queries.
• Improved performance: Hibernate provides features such as caching and lazy loading that can significantly improve the performance of your application.
• Supports multiple databases: Hibernate is database agnostic, meaning it can be used with any relational database management system. This allows developers to switch between databases without having to change their code.
• Easy to maintain: Hibernate provides a flexible and extensible architecture that makes it easy to maintain and evolve your data storage solutions over time.

Overall, Hibernate provides a convenient and efficient way to work with data, making it a popular choice for many Java-based applications.

Java API or known as JPA is an interface specification of Java application program. It is used to describes the relational data’s management in the Java-based applications along with Enterprise Edition and Java platform.

There are four transactions in Hibernate ORM, and these are Atomicity, Consistency, Isolation, and Durability. Acronym used is ACID. These are the properties which every transaction follows.

Transaction commit in Hibernate is a process that marks the end of a transaction and signals the database to make the changes permanent. When a transaction commit is executed, all changes made within the transaction are saved to the database and the transaction is closed. The commit operation is used to persist the changes to the database and ensure data integrity and consistency. If a transaction is not committed, any changes made within the transaction are rolled back and not saved to the database.

The procedure of synchronizing the persistence context state with the database is known as flushing. There are a set of methods sent by Hibernate Session and EntityManager with the help of which the persistence state of an entity can be changed by the application developer.

Save and merge are two methods in Hibernate that are used to persist entities in the database. However, they have different purposes and implications:

1. Save: The save method is used to insert a new entity into the database. It generates a new ID for the entity and sets its state to persistent. If the entity already exists in the database, an exception is thrown.

2. Merge: The merge method is used to update an existing entity in the database or insert a new entity if it does not already exist. Unlike save, merge does not generate a new ID for the entity and does not change its state to persistent. Instead, it returns a managed entity that is in sync with the state of the database.

In summary, save is used for inserting new entities, while the merge is used for updating existing entities or inserting new entities if they do not exist.

The evict method is used for detaching the object from hibernate provides evict () method and session cache. After this process, there is no persistence in the change of the object. The detachment of the associated objects can also take place with the mapping associated with the cascade=” evict.”

Hibernate SessionFactory is an interface, and it is created with the help of Configuration object. It consists of all the database related property details and in this, either hibernate.properties, the hibernate.cfg.xml file is used for pulling it. In the case of the increased number of multiple databases, then the requirement of creating one SessionFactory per database.

Session Factory is used to configure objects which is further responsible for allowing instantiation of the Session object and turning the configuration Hibernation for supplied configuration file application. Threads of an application use SessionFactory in Hibernation.