Spring Interview Questions

Intermediate Level Spring Interview Questions

In this section, we will discuss intermediate-level Spring interview questions.

11. What do you understand by Spring MVC?

Spring MVC stands for Spring Model-View-Controller. It is a powerful and flexible web framework. It is part of the Spring Framework. Spring MVC follows the Model-View-Controller design pattern, which separates the application into three components:

1. Model: It represents the application data and business logic.
    
2. View: It represents the presentation layer of the application.
    
3. Controller: It handles user requests and responses and interacts with the model and view.

12. What do you mean by DispatcherServlet in a Spring MVC application?

The DispatcherServlet in a Spring MVC application is a special servlet. It acts as the front controller for all incoming HTTP(Hypertext Transfer Protocol) requests. It is the heart of the Spring MVC framework. It is also responsible for handling and routing all requests to the appropriate controller. It handles and routes based on the request URL and HTTP method.

When a request is made to a Spring MVC application, it is first intercepted by the Servlet container. The container then passes the request to the DispatcherServlet, which is configured in the web.xml file of the Spring MVC application.

13. What is the use of the @ModelAttribute annotation in Spring MVC?

The @ModelAttribute annotation is used to bind the request parameters to a model attribute. The attribute can then be used by the view to render the response.

Whenever a form is submitted in a Spring MVC application, the values of the form fields are sent as request parameters. The @ModelAttribute annotation in Spring MVC can be used to automatically populate a model attribute with the values of the corresponding form fields.

14. What are the differences between BeanFactory and ApplicationContext?

Both BeanFactory and ApplicationContext are core components of the Spring Framework. They serve as a container for Spring beans. 

However, there are primary differences between them, as mentioned below:

BeanFactory	ApplicationContext
It provides basic support for dependency injection and bean lifecycle management. It initializes beans lazily, which means that beans are only created when they are requested.	It initializes beans eagerly, which means that all beans are created at startup.
It can load resources like XML configuration files, property files, and annotations from any location accessible by the classloader.	It supports a wider range of resource types, such as JNDI objects, JDBC DataSource, and JMS Destination.
It does not provide support for bean post-processors.	It supports bean post-processors, which can modify or enhance the functionality of beans after they are initialized.
It does not provide support for internationalization.	It provides support for internationalization through the use of resource bundles, message sources, and locale resolvers.

15. What do you understand by Spring Security?

Spring Security is a powerful and highly customizable security framework. It provides authentication, authorization, and other security features for Spring-based applications. It is built on top of the Spring framework. It offers various security features, such as encryption, session management, and access control.

Spring Security works by intercepting incoming HTTP requests. It applies a set of security rules and policies to determine whether the request is allowed or not. This is achieved through a combination of filters, interceptors, and configuration settings.

16. What is the use of the Spring WebFlux module, and how is it different from Spring MVC?

The Spring WebFlux module is a reactive web framework. It is built on top of the Spring Framework. It is used for building asynchronous, non-blocking, and event-driven web applications. It provides a functional programming model. It also supports reactive streams, which enable developers to write highly scalable and performant web applications.

Spring WebFlux differs from Spring MVC in several ways:

• Programming model
   
• Concurrency model
   
• Reactive streams

17. What are the differences between Spring Boot and Spring?

Spring Boot and Spring are two related but distinct projects within the Spring ecosystem. Here are the main differences between the two:

Spring Boot	Spring
It provides a "convention over configuration" approach that allows developers to quickly create and configure a Spring application with minimal boilerplate.	It requires developers to configure many aspects of the application explicitly.
It includes a built-in dependency management system that automatically manages versions and conflicts of Spring and other third-party libraries.	It requires developers to manage dependencies manually.
It is designed to be a standalone framework that can be used to create self-contained, production-ready applications.	It is a more general-purpose framework. It can be used for various applications and use cases.
It is easy to use and requires minimal configuration to get up and run.	It can be more complex to use and requires a deeper understanding of the framework.
It is an opinionated framework that provides a set of preconfigured defaults and best practices for building applications.	It is a more modular framework. It provides a wide range of building blocks and allows developers to assemble them customized.

18. What are the different types of bean scopes in Spring?

There are several types of bean scopes in Spring. You can use them to define the lifecycle of a bean. The following are the different types of bean scopes in Spring:

• Singleton: This is the default scope in Spring. 
   
• Prototype: If you need to create a new instance of a bean whenever requested, you should use the prototype scope.
   
• Request: If you need to create a bean that is used only for the duration of an HTTP request, you should use the request scope.
   
• Session: If you need to create a bean that is used only for the duration of an HTTP session, you should use the session scope.
   
• Global Session: If you need to create a bean that is used only for the duration of a global HTTP session, you should use the global session scope.
   
• Application: If you need to create a bean that is used throughout the entire application, you should use the application scope.

19. How do you configure logging in to a Spring Boot application?

Spring Boot provides built-in support for configuring logging into an application. 

The following are the steps to configure logging into a Spring Boot application:

1. Add the logging dependencies.
    
2. Configure the logging level.
    
3. Customize the logging configuration.
    
4. Add log statements to the code.
    
5. View the logs.

20. What kind of information is saved under the application.properties file?

The application.properties file is used in Spring Boot applications to configure various properties related to the application, such as database configuration, server port, logging configuration, etc. Some examples of the properties that can be configured in the application.properties file are:

Server Configuration:

server.port=8080
server.servlet.context-path=/myapp

 

Database Configuration:

spring.datasource.url=jdbc:mysql://localhost/mydb
spring.datasource.username=user
spring.datasource.password=password
spring.jpa.hibernate.ddl-auto=create-drop

 

Logging Configuration:

logging.level.root=INFO
logging.file=myapp.log

 

Security Configuration:

spring.security.user.name=user
spring.security.user.password=password

These are just a few examples of the properties. These properties can be configured in the application.properties file. Spring Boot provides many more configuration options. Those options can be used to customize the behavior of the application. The properties specified in the application.properties file are loaded by Spring Boot at runtime. They are used to configure the application.

Advanced Level Spring Interview Questions

In this section, we will discuss Advance level Spring interview questions.

21. How is Spring integrated with other technologies like Hibernate, JPA, and RESTful web services?

Spring provides several integration mechanisms to work seamlessly with other technologies. These technologies can be Hibernate, JPA(Java Persistence API), and RESTful web services. Here's how Spring integrates with each of these technologies:

• Hibernate Integration: Spring provides integration with Hibernate through the Spring ORM(Object-relational mapping) module. The ORM module provides a HibernateTemplate class. This class simplifies the use of Hibernate APIs and provides a simplified API for performing CRUD(CREATE, READ, UPDATE, and DELETE) operations, query execution, and transaction management. Spring also supports declarative transaction management for Hibernate using annotations or XML configuration.
   
• JPA Integration: Spring integrates with JPA through the Spring Data JPA module. This module provides a repository abstraction. This repository abstraction simplifies the use of JPA APIs. The repository abstraction provides a simplified API for performing CRUD operations and query execution. Spring also supports declarative transaction management for JPA using annotations or XML configuration.
   
• RESTful Web Services Integration: Spring integrates RESTful web services through the Spring MVC module. The Spring MVC module supports developing RESTful web services using annotations or XML configuration. Spring MVC supports using the @RestController annotation to create RESTful controllers. These controllers can handle requests and return responses in various formats, such as JSON, XML, or plain text. Spring also provides support for RESTful client development using the RestTemplate class.

22. How can we implement caching in a Spring Boot application?

Spring Boot provides built-in support for implementing caching. We can implement caching using several caching providers such as Ehcache, Redis, and Caffeine. Here's how to implement caching in a Spring Boot application using the Spring Cache Abstraction:

1. To use caching in your Spring Boot application, you must add the appropriate caching dependencies to your build file. 
    
2. To enable caching, you need to add the @EnableCaching annotation to one of your configuration classes. 
    
3. To configure caching, you must define one or more cache managers. A cache manager is responsible for creating and managing caches. You can configure a cache manager by implementing the CachingConfigurer interface. You can also configure it by using the CacheManagerCustomizer interface.
    
4. Once you've enabled and configured caching in your Spring Boot application, you can use caching by adding the @Cacheable annotation to methods that return values that can be cached. 

23. How can we handle exceptions in a Spring Boot application?

In a Spring Boot application, we can handle exceptions in many ways:

• We can use the @ExceptionHandler annotation. This annotation is used to handle exceptions thrown by a specific controller method or by any controller in your application. 
   
• We can use the @ControllerAdvice annotation to define a global exception handler. It can handle exceptions thrown by any controller in your application.
   
• Spring Boot provides default error handling. It automatically displays a user-friendly error page when an exception is thrown. We can customize this error page by creating a custom error page. We can also configure Spring Boot to use it.
   
• We can create custom error pages for specific HTTP status codes or for specific exception types. To do this, we can create an error page template and configure Spring Boot to use it for specific error codes or exceptions.
   
• We can use the @ResponseStatus annotation. This annotation is used to specify the HTTP status code that should be returned whenever a specific exception is thrown.

24. What do you mean by Spring Interceptors?

Spring Interceptors are a feature in the Spring Framework. They allow you to intercept and modify incoming HTTP requests and outgoing HTTP responses. They are a type of aspect-oriented programming (AOP) functionality. They provide a way to add standard behavior or logic to multiple controllers or actions in a Spring MVC application.

They are implemented as classes. These classes implement the HandlerInterceptor interface. This interface defines three methods. These three methods can be used to intercept HTTP requests and responses:

1. preHandle()
    
2. postHandle()
    
3. afterCompletion()
    

Spring Interceptors can be registered globally or for specific controllers. They can be used for various purposes, such as authentication, caching, logging, or performance monitoring.

25. What are the different types of advice available in AOP?

There are several types of advice in AOP. They can be used to separate cross-cutting concerns from the main logic of a program. The different types of advice in AOP are:

1. Before advice: This advice executes before the actual method execution. It is used to perform some pre-processing before invoking the actual method.
    
2. After returning advice: This advice executes after the successful completion of execution of the actual method and returns a value. It is used to perform some post-processing on the returned value.
    
3. After throwing advice: This advice executes if an exception is thrown by the actual method. It is used to handle the exception and perform some cleanup activities.
    
4. After advice: This advice executes after the completion of execution of the actual method, whether it is normally returning or throwing an exception. It is used to perform some cleanup activities.
    
5. Around advice: This advice executes around the actual method. It can control the invocation of the actual method. It can also perform some pre-processing and post-processing and can handle exceptions.

26. What do you mean by Spring Data JPA? How does it work, and what are some of its advantages over traditional JDBC?

Spring Data JPA is a framework. It provides an abstraction layer on top of the Java Persistence API (JPA). It makes easy the process of accessing and managing relational databases using JPA. Developers can write less boilerplate code and focus on the business logic of their application with Spring Data JPA.

Spring Data JPA works by automatically generating JPA queries. These queries are based on the method name and parameters of the repository interface methods. It provides a set of standard CRUD operations, which can be extended to include custom queries. Developers can also use JPA's query language, JPQL(Java Persistence query language), or native SQL queries.

Some of the advantages of using Spring Data JPA over traditional JDBC(Java database connectivity) include the following:

• Simplified data access
   
• Increased productivity
   
• Improved maintainability
   
• Better code organization

27. What are @Component, @Repository, and @Service annotations in Spring?

The @Component, @Repository, and @Service annotations in Spring are used to indicate the role of a class in the application. All three annotations are used to mark a class as a Spring bean.

• @Component: This is the most general-purpose annotation. It can be used to mark any class as a Spring bean. It indicates that a class is a general-purpose component, such as a utility class or a data access object. It is the default annotation for any class that does not fit into one of the more specific categories.
   
• @Repository: This annotation indicates that a class is a data access object (DAO). It marks classes interacting with a database or another data store. The main advantage of using the @Repository annotation is that it enables exception translation.
   
• @Service: This annotation indicates that a class is a service layer component. It is used to mark classes that contain business logic, such as transactional services or other application services. 

28. What are the differences between @PathVariable and @RequestParam annotations in Spring MVC?

The @PathVariable and @RequestParam annotations in Spring MVC. They are used to extract parameters from the incoming HTTP request. While both annotations are mainly used to handle request parameters, there are some differences in their usage and functionality.

• PathVariable: This annotation is used to extract a variable from the URI(Universal Resource Identifier) path of the request. It is used to handle requests that contain dynamic values, such as RESTful APIs. The @PathVariable annotation maps a variable in the URI to a method parameter. For example, if the URI is "/employees/{empId}", the @PathVariable annotation can be used to extract the value of "empId" from the URI and use it as a method parameter.
   
• @RequestParam: This annotation extracts a parameter from the query string or form data of the request. It is used to handle requests that contain fixed parameters, such as search or filter parameters. The @RequestParam annotation maps a parameter in the request to a method parameter. For example, if the request contains a parameter "number" with value "1", the @RequestParam annotation can be used to extract the value of "number" and use it as a method parameter.

29. What is Spring HATEOAS?

Spring HATEOAS is a subproject of the Spring Framework. It provides support for building hypermedia-driven RESTful web services. HATEOAS stands for "Hypermedia As The Engine Of Application State". It refers to the concept of including hypermedia links in the response of a RESTful service to enable clients to navigate the service's resources.

Spring HATEOAS provides a set of classes and annotations. This set of classes and annotations can be used to create hypermedia links and embed them in the response of a RESTful service. These links provide information about the resources available in the service and the operations that can be performed on them. By including these links in the response, clients can navigate the service's resources without having prior knowledge of the service's API.

30. What is reactive programming, and how does it relate to Spring WebFlux?

Reactive programming is a programming paradigm. It allows for the efficient and scalable handling of large amounts of data in real time. It is characterized by the use of asynchronous and non-blocking data streams. This can handle large amounts of data with lower resource utilization and better performance than traditional blocking I/O.

Spring WebFlux is a reactive web framework. It was introduced in Spring 5. It supports reactive programming in Spring. It is built on top of the reactive streams API. It provides a fully non-blocking and reactive API for handling HTTP requests and responses. Developers can build reactive, event-driven, and non-blocking web applications with Spring WebFlux.

Spring Boot Interview Questions

31. What is Spring Boot and how does it differ from the Spring Framework?

 Spring Boot is an extension of the Spring Framework that simplifies the process of setting up and developing new Spring applications. It provides default configurations, embedded servers, and production-ready features to help developers create stand-alone, production-grade applications quickly. Unlike the traditional Spring Framework, which requires more configuration and setup, Spring Boot uses convention over configuration to streamline development.

32. What are Spring Boot starters?

Spring Boot starters are pre-configured sets of dependencies designed to simplify the setup of Spring applications. Each starter includes a group of related libraries that provide essential functionality for common tasks. For example, spring-boot-starter-web includes libraries for building web applications, such as Spring MVC and embedded Tomcat, while spring-boot-starter-data-jpa includes dependencies for JPA and Hibernate. By using starters, you can easily manage dependencies and avoid manual configuration, making it quicker and more convenient to get your Spring Boot application up and running. Starters help streamline development and ensure consistent configuration across different projects.

33. How does Spring Boot handle external configuration?

Spring Boot handles external configuration through properties files or YAML files, typically named application.properties or application.yml. These files allow you to configure application settings such as database connections, server ports, and custom properties. Spring Boot also supports environment variables and command-line arguments for configuration.

34. What is the purpose of the @SpringBootApplication annotation?

The @SpringBootApplication annotation is a convenience annotation that combines three key annotations: @Configuration, @EnableAutoConfiguration, and @ComponentScan. It indicates that the class is a Spring Boot application and enables auto-configuration and component scanning, allowing Spring Boot to set up the application context and scan for Spring components.

35. How can you customize the Spring Boot banner?

You can customize the Spring Boot banner by creating a banner.txt file in the src/main/resources directory. This file allows you to define a custom ASCII art banner or message that is displayed when the application starts. You can also use a Banner implementation to programmatically customize the banner.

36. What is the role of spring-boot-devtools?

The spring-boot-devtools module provides development-time tools to enhance the developer experience. It includes features like automatic restarts, live reloads, and enhanced debugging. This module helps speed up the development process by automatically restarting the application when changes are detected in the code.

37. How does Spring Boot manage database migrations?

Spring Boot manages database migrations using tools like Flyway or Liquibase. These tools handle versioned migrations, allowing you to apply schema changes and data migrations automatically. You can configure the migration tool in your application.properties or application.yml file and place migration scripts in the appropriate directory.

38. What is the purpose of @ConditionalOnClass annotation in Spring Boot?

The @ConditionalOnClass annotation is used to conditionally configure beans based on the presence of specific classes on the classpath. It allows you to include or exclude configuration based on whether certain classes are available, making it easier to create optional or environment-specific beans.

39. How do you create a RESTful web service using Spring Boot?

To create a RESTful web service with Spring Boot, you need to define a @RestController class with methods annotated with @GetMapping, @PostMapping, @PutMapping, or @DeleteMapping. These annotations map HTTP requests to methods, enabling you to handle different HTTP operations and return responses.

40. How can you secure a Spring Boot application?

You can secure a Spring Boot application using Spring Security. This involves adding the spring-boot-starter-security dependency and configuring security settings using Java configuration or application properties. Spring Security provides authentication, authorization, and protection against common security vulnerabilities.

Spring Data Access Interview Questions

41. What is Spring Data JPA?

Spring Data JPA is a module within the Spring Data project designed to simplify data access and manipulation using JPA (Java Persistence API). It abstracts the complexity of data persistence by providing a repository abstraction layer, which reduces the amount of boilerplate code required for database operations. With Spring Data JPA, you can easily perform CRUD (Create, Read, Update, Delete) operations and define custom queries through repositories, making data handling more efficient and straightforward. The framework integrates seamlessly with JPA, allowing for more flexible and powerful data management in Java applications.

42. How does Spring Data JPA handle entity relationships?

Spring Data JPA handles entity relationships through JPA annotations such as @OneToOne, @OneToMany, @ManyToOne, and @ManyToMany. These annotations define the nature of relationships between entities and enable you to fetch related data using methods like findBy and getOne.

43. What is the purpose of the @Query annotation in Spring Data JPA?

The @Query annotation in Spring Data JPA allows you to define custom queries using JPQL (Java Persistence Query Language) or native SQL directly on repository methods. This annotation provides flexibility to execute complex queries that cannot be generated automatically from method names. By specifying the query in the annotation, you can tailor the query to meet specific requirements, optimize performance, and handle cases where the standard query derivation does not suffice. Additionally, @Query supports query parameters and named parameters, making it a powerful tool for creating efficient and customized data retrieval operations.

44. How does Spring Data JPA support pagination and sorting?

Spring Data JPA supports pagination and sorting through the PagingAndSortingRepository interface. This interface provides methods for paginating and sorting data results. You can use PageRequest to define pagination details, such as the page number and page size, and Sort to specify sorting criteria, such as sorting by a particular field or in ascending/descending order. When you call repository methods with these parameters, Spring Data JPA efficiently retrieves a subset of data and applies the specified sorting, which is useful for managing large datasets and improving performance by loading only the necessary data.

45. What is the purpose of the @Transactional annotation in Spring Data JPA?

The @Transactional annotation in Spring Data JPA manages transaction boundaries. It ensures that all operations within a method are executed as a single transaction. If any operation within the method fails or throws an exception, the entire transaction is rolled back, meaning all changes made during the transaction are undone. This mechanism helps maintain data consistency and integrity, ensuring that the database remains in a stable state even if errors occur during data manipulation.

46. How can you define custom queries in Spring Data JPA repositories?

You can define custom queries in Spring Data JPA repositories using the @Query annotation. By applying @Query to repository methods, you can write JPQL (Java Persistence Query Language) or native SQL queries to handle complex data retrieval needs that go beyond the capabilities of method name conventions. This flexibility allows you to create precise and efficient queries tailored to specific requirements, providing more control over how data is accessed and manipulated.

47. What are @Entity, @Table, and @Id annotations used for in Spring Data JPA?

In Spring Data JPA, the @Entity annotation designates a class as a JPA entity, meaning it represents a table in the database. This annotation tells JPA to manage instances of this class as persistent data. The @Table annotation specifies the name of the database table that the entity is mapped to, allowing customization of table names and schemas. The @Id annotation identifies the primary key field of the entity, which uniquely distinguishes each record in the table. Together, these annotations establish the mapping between Java objects and database tables, enabling JPA to perform operations like querying and updating records.

48. How does Spring Data JPA handle lazy loading?

Spring Data JPA handles lazy loading through the FetchType.LAZY setting on entity relationships. When you define a relationship with FetchType.LAZY, related entities are not loaded immediately when the parent entity is fetched. Instead, they are retrieved only when explicitly accessed. This approach helps improve performance by reducing the amount of data loaded initially, which can be particularly beneficial for large datasets or complex object graphs. However, using lazy loading requires careful management to avoid issues such as LazyInitializationException. This exception occurs if you try to access a lazily-loaded collection or entity outside of an active session or transaction, leading to potential runtime errors. To avoid such issues, ensure that the session remains open while accessing lazily-loaded data or use alternative strategies like eager loading for specific scenarios.

49. What is a repository in Spring Data JPA?

In Spring Data JPA, a repository is an interface that provides a set of methods for performing CRUD (Create, Read, Update, Delete) operations on entities. By extending interfaces like JpaRepository or CrudRepository, you gain access to a variety of built-in methods for interacting with the database, such as save(), findById(), delete(), and more. These repository interfaces simplify data access and reduce the need for boilerplate code. Additionally, you can define custom query methods using method naming conventions or the @Query annotation to handle more complex queries. Repositories abstract away the underlying data access logic, allowing developers to focus on business logic rather than database interactions.

50. How can you handle data validation in Spring Data JPA?

Data validation in Spring Data JPA is managed using JSR-303/JSR-380 annotations such as @NotNull, @Size, and @Pattern on entity fields. These annotations define constraints directly in the entity classes, specifying rules for the data. For example, @NotNull ensures a field cannot be null, @Size limits the length of a string, and @Pattern validates against a regular expression. Spring Boot integrates with Hibernate Validator, which automatically checks these constraints during data persistence and retrieval. This validation process helps maintain data integrity and ensures that only valid data is stored in the database.

Spring Aspect-Oriented Programming (AOP) Interview Questions

51. What is Aspect-Oriented Programming (AOP) in Spring?

Aspect-Oriented Programming (AOP) in Spring is a paradigm that enables the separation of cross-cutting concerns from the main business logic. Cross-cutting concerns, such as logging, security, or transactions, affect multiple parts of an application and can be handled independently from the core functionality. AOP uses "aspects" to modularize these concerns, making the code cleaner and more maintainable. Aspects are applied across various parts of the application, ensuring consistent behavior without scattering the logic throughout the codebase.

52. How do you define an aspect in Spring AOP?

In Spring AOP, you define an aspect by annotating a class with @Aspect. This class contains methods that are annotated with advice annotations such as @Before, @After, @Around, or @AfterReturning. These advices specify actions to be taken at certain points during program execution, called join points. For example, @Before advice runs before the method execution, while @Around advice can modify method behavior and handle both before and after execution.

53. What is a join point in Spring AOP?

A join point in Spring AOP is a specific point during the execution of an application where aspect's advice can be applied. Join points can include method executions, object instantiations, or field access. By targeting these points, you can inject cross-cutting concerns like logging or security checks at precise locations in your codebase, allowing for more modular and maintainable code.

54. What are the different types of advice in Spring AOP?

The different types of advice in Spring AOP include:

• @Before: Runs before the method execution.
• @After: Runs after the method execution, regardless of the outcome.
• @AfterReturning: Runs after the method execution if it completes successfully.
• @AfterThrowing: Runs if the method throws an exception.
• @Around: Surrounds the method execution, allowing for pre- and post-processing.

55. What is a pointcut in Spring AOP?

In Spring AOP, a pointcut is an expression that identifies specific join points where advice should be applied. Join points are points in the execution of the application, such as method calls or object instantiations. Pointcuts use expressions to define criteria based on method names, argument types, or annotations. For example, a pointcut might be configured to apply advice to all methods in a particular package or to methods with a certain annotation. By defining these criteria, pointcuts allow developers to target precise locations in their codebase where cross-cutting concerns, like logging or security, should be injected.

Spring 5 Interview Questions

56. What are the new features introduced in Spring 5?

Spring 5 introduced several key features to enhance its capabilities. Notably, it added support for reactive programming with Spring WebFlux, which enables building non-blocking, asynchronous web applications. The new @RestController annotation simplifies REST API development by combining @Controller and @ResponseBody, automatically handling JSON and XML serialization. Spring 5 also improved its integration with Kotlin, offering extensions and support for Kotlin features. Additionally, performance and flexibility improvements were made across the core framework to enhance overall efficiency and adaptability.

57. How does Spring 5 support reactive programming?

Spring 5 supports reactive programming through Spring WebFlux, a framework designed for building reactive, non-blocking web applications. It leverages reactive types like Flux and Mono, which represent asynchronous data streams and single values, respectively. WebFlux enables efficient handling of large volumes of data with minimal resource consumption and allows for non-blocking, event-driven programming. This approach improves scalability and responsiveness, particularly for applications with high concurrency requirements or complex data flows.

58. What is the role of the @RestController annotation in Spring 5?

The @RestController annotation in Spring 5 simplifies the development of RESTful web services by combining @Controller and @ResponseBody. It automatically serializes return values to JSON or XML format and handles HTTP requests and responses, making it easier to create REST APIs. This annotation reduces boilerplate code and ensures that response data is correctly formatted for client-side consumption without needing explicit response handling.

59. What is the purpose of the ReactiveCrudRepository interface in Spring 5?

The ReactiveCrudRepository interface in Spring 5 provides methods for performing CRUD (Create, Read, Update, Delete) operations in a reactive, non-blocking manner. It extends ReactiveSortingRepository and supports asynchronous interactions with data sources using reactive types like Mono and Flux. This interface allows for efficient data access and manipulation in reactive applications, aligning with the principles of reactive programming and enhancing scalability and performance.

60. How does Spring 5 improve support for Kotlin?

Spring 5 enhances support for Kotlin by integrating Kotlin-specific extensions and features into the Spring framework. It provides Kotlin-friendly APIs and extensions for modules like Spring Data and Spring WebFlux, allowing developers to leverage Kotlin’s concise syntax and language features. This support makes it easier to use Kotlin in Spring applications, offering a more idiomatic and seamless development experience for Kotlin users.

61. What is the significance of WebClient in Spring 5?

WebClient in Spring 5 is a non-blocking, reactive HTTP client designed to handle asynchronous and synchronous HTTP requests. It offers a more modern alternative to the traditional RestTemplate, providing enhanced flexibility and efficiency for making HTTP calls. WebClient supports a wide range of HTTP operations and can handle responses in a non-blocking manner, making it ideal for reactive programming and high-performance applications. It allows for better resource utilization and responsiveness, especially in applications requiring a high volume of concurrent HTTP interactions.

62. What are the key improvements in Spring 5’s web support?

Key improvements in Spring 5’s web support include the introduction of Spring WebFlux for reactive web applications, enhanced support for WebSocket and Server-Sent Events (SSE), and improvements in the @RequestMapping annotation to simplify request mapping and handling.

63. How does Spring 5 handle data binding and validation?

Spring 5 handles data binding and validation using the @Valid and @Validated annotations. These annotations are used to apply validation constraints to user inputs and model attributes, ensuring that data adheres to specified rules. Spring 5 integrates with JSR-380 (Bean Validation 2.0), allowing you to define validation constraints using annotations like @NotNull, @Size, and @Pattern on your Java beans. When a form is submitted or data is bound to a model, Spring automatically validates it according to these constraints and can provide feedback on validation errors, ensuring data integrity and consistency in your application.

64. What is the purpose of the @FunctionalInterface annotation in Spring 5?

The @FunctionalInterface annotation in Spring 5 is used to indicate that an interface is intended to be a functional interface, which means it has exactly one abstract method. This annotation helps with lambda expressions and method references, improving code readability and functional programming support.

65. How does Spring 5 enhance support for microservices?

Spring 5 enhances microservices support through Spring Boot 2.x and Spring Cloud, offering comprehensive tools and libraries for building, deploying, and managing microservices. Key features include service discovery with Eureka, circuit breakers with Hystrix, and distributed tracing with Sleuth. These tools simplify the development and operation of microservice architectures by providing robust solutions for common challenges such as inter-service communication, fault tolerance, and monitoring. Spring 5’s integration with these technologies streamlines the creation of scalable and resilient microservices, facilitating the development of complex distributed systems.

Frequently Asked Questions

How to prepare for Java Spring Interview?

Study essential concepts such as dependency injection, Spring MVC, AOP, and security to prepare for a Java Spring interview. Work on real-world projects while practicing coding exercises and answering common interview questions.  

What is Dependency Injection and IoC in Spring?

Dependency Injection is a technique for supplying dependencies, and Inversion of Control is the ultimate effect of Dependency Injection. IoC is a design approach in which the program's control flow is inverted. One of the subtypes of the IOC principle is dependency injection.

Is Dao a module of Spring?

The Spring-DAO module is not a spring module. It does not include any interfaces or templates for gaining access to the data. One significant change that must be made when using Spring DAO is that it must be annotated with @Repository.

Why Spring is the best framework? 

Due to its comprehensive features, such as dependency injection, aspect-oriented programming, security, and MVC support, Spring is regarded as one of the greatest Java frameworks. Its modular, adaptive structure enables applications that are strong, scalable and maintained.

Conclusion

In this article, we have discussed Spring Interview Questions and Answers. We have discussed interview questions in three categories: beginner, intermediate, and advance. You can check out our other interview questions blogs:

• Excel Interview Questions
• MySQL Interview Questions
• MongoDB Interview Questions
• Manual testing interview questions
•  Wordpress Interview Questions

 

You can also consider our Spring Boot Course to give your career an edge over others.

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