What are the design patterns used in Hibernate?

Hibernate, being an ORM (Object-Relational Mapping) framework, leverages several design patterns to facilitate the mapping between object-oriented domain models and relational database tables. Some of the key design patterns used in Hibernate include:

1. Data Access Object (DAO) Pattern:

   • The DAO pattern is used to abstract and encapsulate the interactions with the underlying database.
   • In Hibernate, DAO classes are often used to isolate the database access logic, providing methods for CRUD (Create, Read, Update, Delete) operations on entities.

2. Session per Request Pattern:

   • This pattern involves associating a Hibernate Session with each user request or transactional context.
   • It ensures that each request or transaction operates within its own session scope, allowing for proper transaction management, caching, and session lifecycle control.

3. Transaction Management Pattern:

   • Hibernate utilizes the transaction management pattern to manage database transactions effectively.
   • Transactions are typically initiated and controlled using Hibernate's transaction API or managed by a transaction manager such as JTA (Java Transaction API) or Spring's transaction management framework.

4. Identity Map Pattern:

   • The Identity Map pattern ensures that each object retrieved from the database is represented by only one instance within the application's memory.
   • Hibernate's first-level cache (session cache) implements this pattern, caching entity instances retrieved during a session to avoid redundant database queries and maintain object identity.

5. Lazy Loading Pattern:

   • Lazy loading is a technique used to defer the loading of associated entities until they are explicitly accessed.
   • Hibernate supports lazy loading for associations, allowing entities to be loaded lazily to improve performance by avoiding unnecessary database queries.

6. Unit of Work Pattern:

   • The Unit of Work pattern ensures that changes made to multiple entities within a single transaction are coordinated and persisted atomically.
   • Hibernate's session acts as a unit of work, tracking changes to managed entities and flushing them to the database in a coordinated manner at the end of the transaction.

7. Proxy Pattern:

   • Hibernate uses proxies to implement lazy loading for associated entities.
   • When an entity with lazy-loaded associations is loaded, Hibernate creates proxy objects that serve as placeholders for the associated entities until they are accessed.

8. Factory Pattern:

   • Hibernate's SessionFactory acts as a factory for creating Hibernate Session instances, providing a centralized mechanism for managing sessions and their lifecycles.
   • The SessionFactory follows the factory pattern to encapsulate the creation and configuration of Session objects.

These design patterns help Hibernate provide a flexible, efficient, and object-oriented approach to database access and persistence, promoting modular design, code reuse, and maintainability in Hibernate-based applications.