For Java Application Development, Spring Boot questions are a big part of the coding interviews. Spring Boot is used to build standalone microservices and is based on Spring Framework. It can create a reliable Java application from scratch due to its low configuration and monitoring features such as tomcat, jetty, and more.

Spring Boot interview questions are tricky to answer as it’s a vast topic to cover. It is essential to follow a thorough preparation strategy and practice some mock Java Spring Boot interview questions. Some of the important concepts you should focus on are Spring Boot auto-configuration, Spring Boot CLI, Spring Boot Actuators, and Spring Boot starter POMs.

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Are you a software engineer and want to know the kind of Spring Boot questions asked in coding interviews? Read further to learn which ones you should prepare.

Here’s what we’ll discuss in this article:

• Spring vs. Spring Boot
• Advantages of Using Spring Boot
• Topics to Prepare for Spring Boot Interview
• Spring Boot Interview Questions for Freshers
• Topic-wise Spring Boot Interview Questions for Experienced Developers
• FAQs on Spring Boot Interview Questions

Spring vs. Spring Boot

Let’s look at some of the differences between Spring and Spring Boot.

Advantages of Using Spring Boot

Let’s look at some of the advantages of using Spring Boot:

• Spring Boot is easy to use and is used to develop spring applications.
• Spring Boot is an existing framework with an addition of an embedded HTTP Server and annotation configuration, making it easier to understand and fasten the development process.
• Spring Boot increases productivity and reduces development time.
• We don’t need to write any XML configuration. Only a few annotations would be enough to do the required configurations.

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Topics to Prepare for Spring Boot Interview

Here’s a list of topics you can prepare for your Spring Boot interview:

• Container, Dependency, and IOC
• Spring Bean Lifecycle
• Aspect-Oriented Programming (AOP)
• Spring MVC
• Spring Boot Basics
• Spring Boot Auto Configuration
• Spring Boot Starter Dependency
• Spring Boot Actuator
• Spring Boot CLI
• Spring Boot Testing 
• Spring Cloud
• Spring Data JPA
• Spring Security

Spring Boot Interview Questions and Answers for Freshers

1. What are the key components of Spring Boot?

Below are the four key components of Spring Boot:

• Spring Boot auto-configuration
• Spring Boot CLI
• Spring Boot starter POMs
• Spring Boot Actuators

2. How does Spring Boot work?

Spring Boot automatically configures your application based on the dependencies you add to the project using annotation. It scans all the components in the project using @ComponentScan annotation.

3. What are starter dependencies?

Spring Boot starter is a maven template which contains a collection of all relevant transitive dependencies which are needed to start a particular functionality. To create a web application, we must import the spring-boot-starter-web dependency.

<dependency>

<groupId> org.springframework.boot</groupId>

<artifactId> spring-boot-starter-web </artifactId>

</dependency>

4. What are the basic annotations that Spring Boot offers?

Spring Boot's primary annotations are found in org.springframework.boot.autoconfigure and its sub-packages. A few of them are:

• @EnableAutoConfiguration - This looks for auto-configuration beans on its classpath and automatically applies them.
• @SpringBootApplication - This denotes the main class of a Boot application. 

5. What is the difference between RequestMapping and GetMapping?

RequestMapping can be used with GET, POST, PUT, and other request methods using the method attribute on the annotation. GetMapping, on the other hand, is an extension of RequestMapping that helps you improve request clarity.

6. What is the use of Profiles in Spring Boot?

Profiles keep the configuration of different environments (DEV, QA, PROD) separate. 

7. How to enable debugging log in Spring Boot application?

There are three ways to enable debugging logs:

• Start the application with –debug switch.
• Set the logging.level.root = debug property in application.property file.
• In the supplied logging configuration file, set the root logger's logging level to debug.

8. What is Dependency Injection?

Dependency Injection is the process of injecting dependent bean objects into target bean objects. There are three types of dependency injection:

• Setter Injection
• Constructor Injection
• Field Injection

9. Explain how to deploy to another server using Spring Boot?

Follow the steps below to deploy a different server with Spring Boot:

• Generate a WAR file from the project.
• Deploy the WAR file to any server

10. What are the steps to connect an external database like MySQL or Oracle?

To connect an external database:

• Add the dependency for MySQL connector to pom.xml
• Remove H2 Dependency from pom.xml
• Set up your MySQL database and configure your connection to the MySQL database.

Topic-wise Spring Boot Interview Questions for Experienced Developers

Container, Dependency, and IOC

1. Describe Dependency Injection and IOC, and explain how Spring MVC implements them.
2. Explain component-scanning and how it’s performed by Spring.
3. Differentiate between Setter and Constructor Injection in Spring.

Aspect-Oriented Programming (AOP)

1. How would you try and catch exceptions using AOP?
2. What is a Cross-cutting concern, and explain how Spring implements it?
3. Explain the advantages of using AOP.

Spring Data JPA

1. Describe Spring Data Repository Interface.
2. Explain the configurations required to use JPA with Spring.
3. How do you implement Spring Data Repositories by Spring at runtime?

Spring Boot Testing

1. Explain the process of creating a shared application context in a JUnit integration test.
2. Differentiate between @MockBean and @Mock. 
3. Explain how Spring Boot simplifies writing tests.

Spring Cloud

1. Describe service registration and discovery.
2. Explain how to implement load balancing using Spring Cloud.
3. Explain Netflix Feign.

Spring Boot Actuator

1. What are the Health Indicator statuses which are provided out of the box?
2. Describe actuator endpoints.
3.  Explain Spring Boot Actuator.

Spring Security

1. Explain how to enable Spring Security in a Java Web Application.
2. Explain how to limit the number of active user sessions using Spring Security.
3. What are security context holders in Spring?

Spring MVC

1. What is the role of DispatcherServlet in Spring MVC?
2. Differentiate between @RequestMapping and @GetMapping.
3. What are the valid return types of a controller method?

FAQs on Spring Boot Interview Questions

Q1. What is the difference between Spring and Spring Boot?

Spring Boot is a framework built on top of Spring and is widely used to develop REST APIs. IT has embedded servers such as Tomcat and Jetty.

Q2. Is Spring Boot hard to learn?

Spring Boot has features like starter dependency, auto-configuration, Spring Boot CLI, Spring Initializr, and Spring Boot Actuator, making Java development easy and fun.

Q3. How to prepare for a Spring Boot interview?

Understand the basic concepts of Spring Boot first. It helps you in understanding the advanced questions later. When a topic is asked, be ready to explain the concepts with the help of an example. It shows the interviewer how good you are with the concepts.

Q4. Which are some Spring Boot interview questions?

Some basic Spring Boot Interview Questions are: What does @SpringbootApplication annotation do? What is a Spring Boot starter? Describe some embedded containers that Spring Boot supports and Explain some Spring Boot annotations.

Q5. What is the starting point of spring boot application?

The entry point of a Spring Boot application is a class that contains @SpringBootApplication annotation. This class needs to have the primary method to run the Spring Boot application.

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