Spring Boot Interview Questions

Introduction to Spring boot Interview Questions And Answers

Spring BOOT is a very popular framework which is built on the top of the Spring framework. It comes up with a new development approach to ease bootstrapping and development of Spring applications. In a typical Spring framework, there are lots of bean and meta configuration in multiple ways like XML, annotations and Java configuration. Spring BOOT avoids all configurations so that developer can quick start new Spring project within a short span of time. Spring BOOT is not a new approach to solve some problems, but it solves the same problem as Spring framework does, but with minimal to no configuration. It follows a default configuration approach which is opinionated. It helps in reducing a lot of boilerplate code and configuration to improve development, unit testing, and integration test process.

Now, if you are looking for a job which is related to Spring Boot then you need to prepare for the Spring Boot Interview Questions. It is true that every interview is different as per the different job profiles but still to clear the interview you need to have a good and clear knowledge of Spring Boot. Here, we have prepared the important Spring Boot Interview Questions and answers which will help you get success in your interview.

Below is the list of top Spring Boot Interview Questions that are asked in an interview, these questions are divided into two parts are as follows:

Part 1 – Spring Boot Interview Questions (Basic)

This first part covers the basic Spring Boot Interview Questions and Answers

Q1) What are the advantages of using Spring boot over spring framework?

Answer:
Some advantage points are listed below:

• Spring boot provides a configuration which is opinionated, thus avoiding lots of boilerplate code and configuration.
• Its applications can be easily integrated into the Spring ecosystem like Spring Security, Spring AOP, Spring transaction, and cache etc.
• It provides embedded HTTP servers like Tomcat etc. to enhance the development process.
• Spring boot offers a command-line interface i.e. CLI tool to develop and test the application, which is prompt and less intrusive.
• Spring boot reduces a lot of development time, by reducing the configuration to minimal or “no-configuration” approach, thus enhances productivity.

Q2) What is @SpringBootApplication annotation?

Answer:
Before Spring BOOT 1.2, it was very common to use annotations like @Configuration, @EnableAutoConfiguration, @ComponentScan. The @SpringBootApplication annotation is equal to all of the three annotations mentioned before with their default attributes. Means a single annotation is enough now for multiple features like enabling auto configuration and performing a component scan of beans.

@SpringBootApplication
public class MyApp {
……….
}

Q3) Explain about Spring boot starter POM file?

Answer:
Starter POM file actually contains a lot of dependencies, so that project can be up and running quickly within in a very short span of time. It is basically a combination of dependency descriptors that anyone can include in their application and automatically all project related dependency would be available. Starter POM files also manage transitive dependencies of the project. POM file structure is arriving from Maven based application. In other words, a developer creating a project that uses Spring REST for creating rest APIs, just have to include relevant starter POM file, which will import all required dependencies for Spring rest application. All the tedious task of searching and configuring dependencies, required for a framework is now no more needed.

Let us move to the next Spring Boot Interview Questions.

Q4) Explain the Actuator in Spring Boot?

Answer:
Actuator brings production-ready features to the table for Spring boot application. Production-ready features like application monitoring, gathering metrics, understanding traffic, and the database state, become very crucial to keep the application in a healthy state. A major benefit of utilizing Actuator like a library is that a developer can have access to production-grade tools, without having to implement any one of these tools. To enable Spring Boot Actuator dependency to our package manager, add below to your POM file

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

Once this dependency is in the classpath, multiple endpoints are available with the developer.

Q5) What is the way to reload changes on Spring boot without server-restart?

Answer:
Any changes are reloaded in spring boot without starting the server by using dev tools.

<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-devtools</artifactId>
<optional>true</optional>
</dependency>

Spring boot provides module called DevTools, which can enhance the productivity of a spring boot developer. It can auto-deploy the changes to the server, with auto-restarting the server. This is the common Spring Boot Interview Questions asked in an interview. Thus, a developer can reload his changes on Spring boot without having to restart the server. This package is provided in development mode only, but not in production mode.

Part 2 – Spring Boot Interview Questions (Advanced)

Let us now have a look at the advanced Spring Boot Interview Questions.

Q6) What is the way to run the Spring boot application on a custom port?

Answer:
There is a file called application.properties in Spring boot. This file can be customized to bring in any change, to alter the behavior of a running spring boot application. If a developer wants to run a spring boot application on a custom port, he can specify the port in an application.properties file:

server.port = 8080

This entry will ensure that application would run on 8080 port.

Q7) What is the way to implement Spring batch in Spring boot?

Answer:
batch processing involves large volumes of data records processing. Spring boot batch provides a function which can be reused, and essential for doing batch processing. It also provides services and features, which helps in optimization and partition techniques, resulting in high volume and high-performance batch jobs.

<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-batch</artifactId>
<optional>true</optional>
</dependency>

Above changes in POM file, will include the necessary packages in an application, which are required to do the batch processing in spring boot project.

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Let us move to the next Spring Boot Interview Questions

Q8) What is the way to configure logging in Spring boot application?

Answer:
The developer can easily specify logging level in an application.properties files:
Logging.level.spring.framework = Debug
This single line in application properties file will let the spring framework logs to the debug level.
In case, a developer wants to put logs to the file, he can specify logger.file in application properties

Logging.file = ${java.io.tempdirectory}/sample.log

Apart from the above two approaches, a developer can also create a logback.xml file under main/java/resources and specify the logging configuration in the file. Spring boot will automatically pick this file.

Q9) What is a benefit of including spring-boot-maven-plugin?

Answer:
This is the advanced Spring Boot Interview Questions asked in an interview. spring-boot-maven-plugin provides a list of commands which are helpful in enabling the developer to package the code as a jar file to run the application.
Spring-boot: run, it will run spring boot application.
Spring-boot: repackage, it will repackage jar or war file
Spring-boot: build, generate build information
Spring-boot: start, stop – to manage the lifecycle of spring boot application.

Q10) What is the way to add custom JS code in Spring boot application?

Answer:
A developer can create a folder by the name of “static”, under the resources folder. Then all the static content can be put into this folder.
Any JavaScript file i.e. test.js would reside in /resources/static/js/test.js
Developer can then refer to this file in JSP like:
<script src = “/js/test.js”></script>

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