Spring Boot Interview Questions And Answer

Introduction

The Spring Framework is an application and an inversion of control container for the Java platform. Any Java application can use its core features, but these are extensions for creating web applications on top of the Java EE (Enterprise Edition) platform. It does not impose any specific programming model and has become popular in the Java community as an addition to the JavaBeans (EJB) model. The Spring Framework is open source.  

Spring Boot is an open-source Java framework for building microservices and web apps with minimal setup and no XML configuration. It’s a key topic and often appears in interview questions on Spring Boot for its auto-configuration and fast development features.

Let's get started with Spring Boot Interview Questions and Answers!

Spring Boot Interview Questions and Answers For Freshers

Let us now read a set of Spring Boot interview questions and answers for freshers, which will surely help you crack your dream job:

1. What is Spring Boot? 

Sprint Boot is the Java-based Spring framework used for Rapid Apps Development (to build standalone microservices). It has extra support for auto-configuration and embedded application servers like Jetty, Tomcat, etc. 

• Spring Boot framework is independent.
   
• It creates executable Spring applications that are production-grade.

2. What are the advantages of using Spring Boot?

The advantages are as follows:

• We don't need to write XML configuration; only a few annotations are required to complete the configuration
• Easy to understand and develop Spring applications
• Increases productivity and reduces development time
• Minimum configuration
• Spring Boot is an existing framework with the addition of the embedded HTTP server and annotation configuration, making it easier to understand and faster the development process

3. Write some features of Spring Boot?

A few features of Spring Boot are given below:

1. Spring CLI allows you to use Groovy to write Spring Boot applications and avoid boilerplate code
    
2. Starter Dependency – It aggregates common dependencies together and eventually improves productivity
    
3. Auto-Configuration – This Spring Boot feature helps you load the default configurations according to the project you are working on. In this way, we can avoid any unnecessary WAR files
    
4. Spring Initializer is a web application that can create an internal project structure. So, you do not need to manually set up the project structure, and you can use this feature
    
5. Spring Actuator – This feature helps while running Spring Boot applications
    
6. Logging and Security – The security and logging feature of Spring ensures that all the applications made using Spring Boot are adequately secured without any hassle

4. What are the Spring Boot key components?

Spring Boot is a powerful framework that simplifies the development of Spring-based applications by providing auto-configuration, embedded servers, and production-ready features. The four primary components of Spring Boot are:

1. Spring Boot Starters

• Spring Boot starters are a set of pre-configured dependencies that help developers quickly set up a project without manually specifying each library.
   
• These starters include commonly used dependencies for different functionalities, such as spring-boot-starter-web (for building web applications), spring-boot-starter-data-jpa (for database interactions), and spring-boot-starter-test (for testing).
   
• By using starters, developers can avoid version conflicts and dependency management issues, making project setup easier and faster.
   
• Starters reduce the complexity of managing dependencies, ensuring that all necessary components work seamlessly together.
   

2. Spring Boot Auto-Configuration

• Auto-configuration is one of the most powerful features of Spring Boot, enabling the framework to automatically configure beans based on the dependencies available in the classpath.
   
• It eliminates the need for extensive manual configuration by providing sensible defaults, making application development more streamlined.
   
• Developers can override default configurations by defining custom settings in the application.properties or application.yml file.
   
• Auto-configuration significantly reduces boilerplate code, allowing developers to focus on business logic rather than infrastructure setup.
   

3. Spring Boot Embedded Server

• Spring Boot comes with embedded servers like Tomcat, Jetty, and Undertow, which eliminate the need to deploy applications to an external server.
   
• This feature allows developers to run applications as standalone Java applications without requiring additional configuration.
   
• Embedded servers improve development efficiency by enabling rapid testing and deployment, making the application more portable.
   
• Developers can customize the embedded server configurations through properties or programmatic settings, allowing flexibility in tuning performance and behavior.
   

4. Spring Boot Actuator

• Spring Boot Actuator provides production-ready features, such as monitoring, metrics, and health checks, making it easier to manage and troubleshoot applications.
   
• It exposes endpoints like /actuator/health (to check application health) and /actuator/metrics (to monitor system metrics).
   
• Actuator helps in identifying performance bottlenecks and potential issues by offering detailed insights into application runtime.
   
• It integrates with monitoring tools like Prometheus, Grafana, and Micrometer, enabling seamless observability of Spring Boot applications.
   

These four components work together to make Spring Boot a robust framework, simplifying development while ensuring efficiency and scalability.

5. What is meant by the RAD model?

The RAD(Rapid Application Development) model is a software development process that prioritizes rapid prototyping and speedy development over extensive planning and design phases. It emphasizes iterative development and close collaboration with end-users to quickly produce a functional software product.

6. What are the distinct phases involved in the RAD (Rapid Application Development) model?

Various phases are involved in the RAD model:

1. Business Modeling: Identifying the needs and objectives of the project
    
2. Data Modeling: Creating data models to represent the system's data
    
3. Process Modeling: Defining system processes and workflows
    
4. Application Generation: Rapidly building the software using tools and techniques
    
5. Testing and Turnover: Rigorous testing and user feedback to refine the application
    
6. Cutover: Deploying the application into the production environment

7. How can I start a Spring Boot executable JAR file?

You can start a Spring Boot executable JAR by running the java -jar command followed by the JAR file's name. 

For example: java -jar myapp.jar.

8. What are the Spring Boot starters, and what are the available starters?

Spring starters are a set of convenient dependency management providers that can enable dependencies in the application. These starters make development fast and rapid. All the available starters come under the organization's Spring Framework.boot group. A few of the famous starters are as follows:

• Spring-boot-starter: – This is one of the core starters that includes logging, auto-configuration support, and YAML
   
• Spring-boot-starter-JDBC – This is used for the HikariCP connection pool with JDBC
   
• Spring-boot-starter-web – This is the starter used for building web applications, including RESTful apps using Spring MVC
   
• Spring-boot-starter-data-JPA – This is the starter to use Spring Data JPA and Hibernate
   
• Spring-boot-starter-security – It is used for Spring Security
   
• spring-boot-starter-aop: This is used for aspect-oriented programming with AspectJ and Spring AOP
   
• Spring-boot-starter-test: This is the starter for testing Spring Boot applications

9. What is Thymeleaf in Spring Boot?

The Java-based server-side template engine offers elegant and natural temps for a web application.

10. What does Spring Boot support embedded containers? 

Spring Boot supports three embedded containers:

• Tomcat (used by default)
   
• Undertow
   
• Jetty

11. How to deploy Spring Boot applications in Tomcat?

Whenever you create your Spring Boot application and run it, Spring Boot will automatically detect the embedded Tomcat server and deploy your application on Tomcat.

After the successful execution of your application, you will be able to launch your REST endpoints and get a response.

12. What is Spring Actuator, and write its advantages?

Spring Actuator is one of the cool features of Spring Boot, with the help of which you can easily see what is running inside a running application. So, when you want to debug your application and analyze the logs, you need to understand what is happening in the application. In such a scenario, the Spring Actuator provides easy access to features such as identifying beans, CPU usage, etc. The Spring Actuator provides an effortless way to access the production-ready REST points and helps to fetch all information from the web. These points are secured using Security's content negotiation strategy.

13. What is Spring Boot dependency management?

Spring Boot dependency management is used for managing dependencies and configuration automatically without the need to specify the version for any of those dependencies.

14. Can you disable particular auto-configuration in Spring Boot? Explain how?

Yes, we can do that by

• Using the exclude attribute of @EnableAutoConfiguration

@Configuration
@EnableAutoConfiguration(exclude={DataSourceAutoConfiguration.class})
public class CustomConfiguration {}

• using the exclude attribute for @SpringBootApplication annotation

@SpringBootApplication(exclude= DataSourceAutoConfiguration.class)
public class CustomApplication {}

15. Can Spring Boot be used to create non-web applications?

Yes, Spring Boot supports both web and non-web applications. We must remove these web dependencies from the classpath and the application context to create the non-web application. 

16. Explain how to use Thymeleaf?

Thymeleaf is a server-side Java engine used for web applications. It aims to bring a template for your web application and can integrate well with the Spring Framework and HTML5 Java web applications. To use Thymeleaf, you must add the following code in the pom.xml file. 

<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-thymeleaf</artifactId>
</dependency>  

17. What does the @SpringBootApplication annotation do?

The @SpringBootApplication annotation is the same as using @Configuration, @EnableAutoConfiguration, and @ComponentScan with default attributes. Spring Boot enables the developer to use a single annotation instead of multiple. But, as we know, Spring provides very loosely coupled features so that we can use them for each annotation per our project needs.  

18. What is the purpose of using @ComponentScan in the class files?

It scanned all the beans and package declarations when we initiated the application. We need to add the @ComponentScan for your class file to scan the components added to your project.

19. How does a Spring Boot application get started?

Like any other Java program, a Spring Boot application has a main method. This method is an entry point that invokes the SpringApplication#run method to bootstrap the application.

@SpringBootApplication 
public class Application { 
   
       public static void main(String[] args) {    
    
             SpringApplication.run(MyApplication.class);        
               // other statements     
       } 
}