Interview Questions On Spring & Hibernate

Go through important interview questions on Spring & Hibernate. Enhance your knowledge and ace your next interview with confidence.

1. What is an inversion of control (IoC) and how does Spring implement it? 

Inversion of Control is a design principle where the control of object creation and lifecycle is transferred to a container or framework. In Spring, IoC is achieved through dependency injection, where the container manages the creation and wiring of objects (beans) and injects dependencies into them. 

2. Explain the difference between constructor injection and setter injection in Spring. 

Constructor injection involves passing dependencies as arguments to a class’s constructor, while setter injection involves using setter methods to set dependencies on a class after it has been instantiated.  Constructor injection is generally considered preferable for mandatory dependencies, as it ensures that objects are fully initialized when they’re created, while setter injection is more suitable for optional dependencies or circular dependencies. 

3. What are the different types of bean scopes supported by Spring? 

Spring supports several bean scopes, including singleton (default), prototype, request, session, and application. Singleton beans are created once per Spring container, while prototype beans are created each time they’re requested. Request, session, and application scopes are specific to web applications and dictate the lifecycle of beans within the corresponding web contexts. 

 

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4. Explain the concept of aspect-oriented programming (AOP) and how it is implemented in Spring. 

Aspect-oriented programming is a programming paradigm that allows you to modularize cross-cutting concerns, such as logging, transaction management, and security, that would otherwise result in code duplication. In Spring, AOP is implemented using aspects, which are modular units of cross-cutting functionality. Spring AOP uses proxy-based or aspectJ-based mechanisms to apply aspects to target objects at runtime. 

5. What is Spring MVC, and how does it differ from Spring Boot? 

Spring MVC is a web framework built on top of the Spring framework that provides support for building web applications using the Model-View-Controller pattern. It offers features such as controllers, view resolvers, and form handling. Spring Boot, on the other hand, is an opinionated framework for building stand-alone, production-grade Spring-based applications with minimal configuration. While Spring MVC  is a part of the broader Spring ecosystem, Spring Boot simplifies the setup and deployment of Spring applications. 

6. Explain the role of the @Component, @Service, @Repository, and @Controller annotations in Spring. 

These annotations are used to declare Spring-managed beans within an application: 

@Component: Marks a class as a Spring component, indicating that it will be automatically detected and registered as a bean. 

@Service: Specialization of @Component used to annotate classes representing business services.

 

@Repository: Specialization of @Component used to annotate classes representing data access 

components (typically DAOs). 

@Controller: Specialization of @Component used to annotate classes representing web controllers in a  Spring MVC application. 

7. What is Hibernate, and how does it differ from JDBC? 

Hibernate is an open-source Object-Relational Mapping (ORM) framework for Java that simplifies the development of database-driven applications by mapping Java objects to database tables and vice versa.  Unlike JDBC, which requires developers to write SQL queries and handle database connections manually,  Hibernate abstracts away the database interactions and provides a higher-level, object-oriented interface for data persistence. 

8. What are the key benefits of using Hibernate? 

Some key benefits of using Hibernate include: 

• Automatic mapping of Java objects to database tables (and vice versa). 
• Simplified database access through the use of HQL (Hibernate Query Language) or Criteria API. Automatic generation of SQL queries, reducing the need for manual query writing. Built-in caching mechanisms for improved performance. 
• Support for transaction management and database operations. 
• Database independence, allows applications to work with different database systems without modification. 

9. Explain the difference between transient, persistent, and detached objects in Hibernate. 

Transient objects are newly created objects that are not associated with any Hibernate session or database record. 

Persistent objects are objects that are associated with a Hibernate session and have a corresponding database record. Changes made to persistent objects are automatically synchronized with the database. 

Detached objects are objects that were previously associated with a Hibernate session but are no longer actively managed. They may still contain data from the database, but changes made to detached objects are not automatically synchronized with the database unless they are reattached to a session. 

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10. What is lazy loading in Hibernate, and how does it work? 

Lazy loading is a technique used to delay the fetching of related entities until they are explicitly accessed.  In Hibernate, lazy loading is achieved through proxy objects and bytecode instrumentation. When an entity with lazy-loaded associations is loaded from the database, Hibernate substitutes the actual collection or reference with a proxy object. The proxy object only loads the associated data from the database when it is accessed for the first time.

11. What is the difference between Hibernate’s save() and persist() methods? 

Both save() and persist() methods are used to save transient objects to the database. The main difference between them is that persist() is part of the JPA specification, while save() is specific to  Hibernate. Additionally, persist() does not guarantee immediate execution of the SQL INSERT statement,  while save() does. In practice, persist() is typically used for entities that are not yet associated with a database identity, while save() is used when you need immediate feedback about the success of the  operation. 

12. Explain the concept of Hibernate caching, and discuss its types. 

Hibernate caching is a mechanism used to improve the performance of database operations by storing frequently accessed data in memory. Hibernate supports several types of caching: 

First-level cache (session cache): Maintained at the session level, it caches objects retrieved within a session. 

Second-level cache: Shared across sessions and caches objects at the session factory level, providing a broader scope of caching. 

Query cache: Stores the results of queries in memory, allowing subsequent identical queries to be served from the cache rather than hitting the database.

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Author:-

Pooja Ghodekar

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