Spring Interview Questions Preparation Course

1. You work for modules in Web layer of Spring framework?

   • The Web layer of Spring, often used with Spring MVC, provides capabilities to build web applications and services. It includes support for various data-access technologies like JDBC, ORM (Object-Relational Mapping), messaging (JMS, AMQP), as well as RESTful and RPC-style web services.

2. What is the main use of Core Container module in Spring framework?

   • The Core Container module provides the foundation for the entire Spring Framework, providing Dependency Injection (DI) capabilities. It manages objects by allowing you to define your application's objects as 'beans'. These beans are configured to depend on other beans, and the container resolves these dependencies for you.

3. What kind of testing can be done in Spring Test Module?

   • The Spring Test module allows for unit and integration testing of your Spring-based applications. It provides support for mock objects, aspect-oriented testing, context loading from various sources, and a powerful TestContext framework to assist in advanced testing scenarios.

4. What is the use of BeanFactory in Spring framework?

   • The BeanFactory interface is the foundation of the Spring IoC container. It allows for the instantiation, configuration, and invocation of beans within a single class or multiple classes. It provides a way to look up and instantiate objects from a pool of configured beans and manage their lifecycle.

5. Which is the most popular implementation of BeanFactory in Spring?

   • The most popular implementation of BeanFactory is ApplicationContext. While BeanFactory supports basic IoC container functionality, ApplicationContext extends this with additional capabilities such as easy integration with AOP alliance proxies (for use with AOP), and resource resolution from the context environment.

6. How to decide which scope- Prototype or Singleton to use for a bean in Spring?

   • Choose Prototype if the bean is stateless and needs a new instance each time it's requested. Use Singleton when there should be a single instance of the bean throughout the application's lifetime, shared by all beans that depend on it.

7. What are the drawbacks of Setter based Dependency Injection (DI) in Spring?

   • Setter-based DI can lead to larger codebases if many setter methods need to be defined for a class. It can also make it harder to see at a glance which dependencies a class has, and it can result in classes with a lot of empty or nullable setters which some developers find less than ideal.

8. What are the differences between Dependency Injection (DI) and Factory Pattern?

   • Dependency Injection (DI) is a design pattern whereby an object's dependencies are injected into it by an external source, rather than the object creating them itself. The Factory pattern is a creational design pattern that provides an interface for creating objects in a superclass, but allows subclasses to alter the type of objects created. DI promotes loose coupling and better testability, while the Factory pattern focuses on creating objects without specifying the exact class of the object that will be created.

9. What is the difference between FileSystemResource and ClassPathResource?

   • FileSystemResource represents a resource located within the file system, while ClassPathResource locates a resource as a file within the classpath of the application (i.e., within the archive or on the filesystem location that forms the classpath).

10. Name some popular Spring framework annotations that you use in your project?

    • Some of the most commonly used Spring annotations include: @Autowired, @Service, @Component, @Repository, @Configuration, @Bean, @Inject, @Value, @RequestMapping, @RestController, @GetMapping, @PostMapping, @PutMapping, @DeleteMapping, @ExceptionHandler.

11. How can you upload a file in Spring MVC Application?

    • To handle file uploads in Spring MVC, you can use the @MultipartHolder or commons-fileupload and commons-io libraries. You define a form with enctype="multipart/form-data" in your JSP or HTML and create a handler method annotated with @PostMapping to process the uploaded file(s).

12. What are the different types of events provided by Spring framework?

    • Spring provides two types of events: application events (which are part of the Spring Framework) and context startup events (part of the WebApplicationContext in a web environment). Application events can be defined using ApplicationEvent or by implementing ApplicationEventPublisherAware. Context startup events provide information about the lifecycle transitions of the WebApplicationContext.

13. What is Spring Boot?

    • Spring Boot is an extension of the Spring framework that simplifies the initial setup and development effort for creating stand-alone, production-grade Spring applications. It automates configuration for common services, provides opinionated defaults to simplify decision making, and offers a suite of tools to facilitate development (like auto-configuration, Actuator, DevTools, etc.).

14. What is the difference between DispatcherServlet and ContextLoaderListener in Spring?

    • DispatcherServlet is the front controller that handles all incoming requests in a web application and routes them to the appropriate handler methods. It is responsible for setting up an application context, invoking handlers, and returning the results as HTTP responses. ContextLoaderListener is a listener that loads and destroys the root WebApplicationContext for a web application when it starts up and shuts down.

15. How will you handle exceptions in Spring MVC Framework?

    • Exception handling in Spring MVC can be done by defining exception handler methods annotated with @ExceptionHandler at the controller level, or globally by configuring an ExceptionResolver implementation within the DispatcherServlet. Additionally, Spring MVC supports internationalized error pages using property files or error pages defined as resources.

16. How to manage database transactions in Spring?

    • Database transactions can be managed using the @Transactional annotation at the service layer. This annotation is provided by the Spring Transaction abstraction which is based on AOP. It allows defining transactional semantics for methods declared in your class without having to write any aspect code yourself.

17. What are the benefits of using Spring Data JPA?

    • Spring Data JPA provides easy integration with various JPA implementations, abstracts the data access layer, reduces boilerplate code, simplifies testing, and provides advanced features like custom repositories, query method abstraction, and more. It also supports the use of various NoSQL databases in addition to traditional SQL databases.

18. How to handle asynchronous processing in Spring?

    • To handle asynchronous processing in Spring, you can use @Async annotation on a method to execute it asynchronously. Spring also provides the TaskExecutor interface and various implementations like ThreadPoolTaskExecutor to manage a pool of threads for executing tasks concurrently.

19. What is Spring Security and how to use it?

    • Spring Security is a powerful, extensible authentication and access-control framework for securing Spring applications. It provides ready-to-use security features such as form-based login, role-based access control, and integration with OAuth2 and OpenID Connect. To use Spring Security, you typically create a configuration class that extends WebSecurityConfigurerAdapter or SecurityConfig and configure the required security settings there.

20. What are the benefits of using Spring Cloud?

    • Spring Cloud provides a set of tools for developers to quickly build scalable, resilient, and distributed system. It simplifies the process of configuring complex functionality like service discovery, circuit breakers, intelligent routing, control bus, global unique ID generation, and distributed configuration. It also supports integration with cloud-specific features and services from Amazon Web Services (AWS), Microsoft Azure, or Google Cloud Platform (GCP).

These are just a few of the many concepts and functionalities provided by Spring. Depending on your specific use case, you may encounter other patterns and practices within the Spring ecosystem that can help streamline your application development process.