12 Spring-Boot Interview Questions for Java Developers series -22
Hello folks, In this article, I have published 12 Spring Boot interview questions. Going forward, I will be posting more than 200+ interview questions exclusively on Spring Boot Microservice in a series of articles every week. Please stay tuned for more articles like these.
(A bit of context: I’ve conducted numerous interviews for software engineering positions in most of the MNCs. Additionally, there have been instances where I faced challenges during coding interviews due to lack of preparation.)
Are you preparing for a job interview as a Java developer?
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Guide To Clear Spring-Boot Microservice Interview here Gumroad (PDF Format) and Amazon (Kindle eBook).
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Guide To Clear Spring-Boot Microservice Interview[Free Sample Copy]
What is Spring-boot? What are the benefits? What is the advantage of Spring boots?
Spring Boot is an open-source Java framework for building production-ready applications quickly and easily.
Benefits of Spring Boot: Rapid development: It simplifies and accelerates application development.
- Opinionated defaults: It provides sensible configurations and eliminates boilerplate code.
- Microservices-ready: It offers features for building and deploying microservices.
- Auto-configuration: It automatically configures the application based on dependencies.
- Embedded servers: It includes embedded servers for easy deployment.
- Easy testing: It provides utilities for testing and mocking dependencies.
- Actuator: It offers production-ready features like monitoring and metrics.
- Large community and ecosystem: It has extensive community support and a vast ecosystem of plugins and libraries.
Advantage:
Spring Boot’s advantages lie in its simplicity, rapid development capabilities, embedded servers, microservices support, production-ready features, ecosystem integration, and developer-centric approach. These benefits contribute to faster development cycles, increased productivity, and streamlined application deployment.
Difference between a spring framework and Spring-Boot?
Key differences:
- Configuration: Spring requires explicit configuration, while Spring Boot provides opinionated defaults and auto-configuration.
- Deployment: Spring requires manual deployment and setup, while Spring Boot includes embedded servers and facilitates easy deployment.
- Development speed: Spring can have a steeper learning curve and more configuration overhead, while Spring Boot aims for rapid application development with less boilerplate code.
- Microservices support: Spring Boot has built-in features and dependencies for developing microservices, while Spring requires additional configuration for microservices architecture.
Latest Feature of Spring-Boot?
- Improved startup time: Spring Boot 2.3 introduced significant improvements in startup time.
- JDK 17 support: Added support for JDK 17 as a baseline, including new language features.
- Spring Boot Actuator enhancements: Actuator, the production-ready monitoring and management tool, received various improvements.
- RSocket support: Added support for the RSocket communication protocol.
- OAuth 2.0 client enhancements: Improved support for OAuth 2.0 client functionality.
- Kotlin Coroutines support: Added support for Kotlin Coroutines, enabling asynchronous programming in Kotlin.
What is Auto-Configuration?
Auto-configuration in Spring Boot is a feature that automatically configures the application based on the dependencies and settings it detects on the classpath. It eliminates the need for manual configuration by providing sensible defaults and automatically wiring beans. It simplifies development by reducing the amount of explicit configuration required and allows developers to focus more on writing business logic.
What are Sprint-boot starters?
Spring Boot starters are a set of convenient dependencies bundled together to provide a specific feature or functionality in a Spring Boot application. They simplify the process of adding common dependencies to your project by including a curated set of libraries and configurations.
Starters encapsulate all the necessary dependencies, configurations, and auto-configuration classes required for a particular functionality, such as web development, data access, security, messaging, etc. By including a starter dependency in your project, you get access to all the required dependencies and auto-configuration automatically, without the need to manually manage and configure them individually. Starters make it easier to get started with various aspects of Spring Boot development and promote a more streamlined and opinionated approach to building applications.
What are actuators in Spring-Boot?
Actuators in Spring Boot are a set of production-ready features that provide insight into and control over the running application. They enable monitoring, managing, and interacting with the application in a production environment.
Actuator endpoints expose information about the application, such as health status, metrics, environment variables, and more. These endpoints can be accessed via HTTP or JMX to retrieve important runtime information, troubleshoot issues, and perform management operations on the application.
Actuators provide valuable features like health checks, metrics gathering, logging configuration, thread dump analysis, and more. They enhance observability and facilitate operational tasks, making it easier to monitor and manage the Spring Boot application in production.
What is dev-tools in the boot?
Key features of DevTools include:
- Automatic Restart: DevTools monitors classpath changes and automatically restarts the application whenever a file is modified, allowing for faster iteration during development.
- Live Reload: It enables live reloading of static resources, such as HTML, CSS, and JavaScript files, without requiring a full application restart. This feature speeds up frontend development by reflecting changes instantly in the browser.
- Remote Development: DevTools supports remote development scenarios, allowing developers to edit code on their local machine while the application runs on a remote server. Changes are automatically synchronized and applied without the need for manual redeployment.
- Developer-Friendly Configuration: DevTools provides sensible defaults and auto-configuration to optimize the development experience, while still allowing developers to customize the behavior as needed.
What Are the Annotations that Spring Boot Offers?
Spring-Boot Annotations:
@RequestMapping, @RestController, @SpringBootApplication, @ComponenScan, @EnableAutoConfiguration, @Configuration, @Component, @Bean, @Service, @Repository
- @RequestMapping: Specifies the URL mapping for handling HTTP requests in a Spring MVC controller.
- @RestController: Combines @Controller and @ResponseBody, indicating that the return value of the methods should be serialized directly into the HTTP response body.
- @SpringBootApplication: Combines @Configuration, @EnableAutoConfiguration, and @ComponentScan, marking the main class of a Spring Boot application and enabling auto-configuration and component scanning.
- @ComponentScan: Scans the specified packages for Spring components to be managed by the Spring container.
- @EnableAutoConfiguration: Enables Spring Boot’s auto-configuration mechanism, allowing the application to configure itself based on classpath dependencies.
- @Configuration: Indicates that a class declares bean definitions and should be processed by the Spring container.
- @Component: Marks a class as a Spring component, allowing it to be automatically detected and managed by the Spring container.
- @Bean: Indicates that a method produces a bean instance to be managed by the Spring container.
- @Service: Marks a class as a service component, typically used for business logic implementation.
- @Repository: Marks a class as a repository component, typically used for database access.
How to disable Auto-Confguration for a specific class?
To disable auto-configuration for a specific class in a Spring Boot application, you can use the @EnableAutoConfiguration annotation along with the exclude attribute. Here’s a short answer on how to do it:
- Create a configuration class and annotate it with @EnableAutoConfiguration.
- Use the exclude attribute of @EnableAutoConfiguration to specify the class or classes you want to exclude from auto-configuration.
- Provide the class or classes you want to exclude as values to the exclude attribute.
@Configuration
@EnableAutoConfiguration(exclude = SomeClassToExclude.class)
@SpringBootApplication
public class YourApplication {
// Application code
}Uses of Springboot Profiles?
Environment-specific configuration: Profiles help in defining specific configurations for different environments such as development, testing, staging, and production. This enables easy customization of properties, database connections, and other settings based on the target environment.
For Example, You can use YAML files specific to the environment like Dev, QA, and PROD environment.
Feature toggling: Profiles can be used to enable or disable certain features based on the active profile. This allows you to control the availability of specific functionality in different environments.
Component customization: Profiles enable you to define different beans or configurations for specific profiles. This allows you to use different implementations of components based on the active profile, facilitating easy testing or runtime customization.
Integration with external systems: Profiles can be used to configure different settings for interacting with external systems. For example, you can define separate profiles for connecting to different databases or using different messaging brokers.
Conditional loading: Profiles can be used to conditionally load or exclude certain configurations or beans based on the active profile. This helps in managing dependencies and improves application performance by loading only the required components.
How to set active profiles in Spring-boot?
application.properties/application.yml: Add the following line to your application.properties or application.yml file:
spring.profiles.active=profile1,profile2How to use a different server instead of Tomcat in the boot?
To use a different server instead of Tomcat in a Spring Boot application, follow these steps:
- Exclude the Tomcat dependency from your project’s dependencies. This can be done in your build files, such as build.gradle or pom.xml, by removing or excluding the Tomcat dependency.
- Add the desired server dependency to your project’s dependencies. For example, if you want to use Jetty as the server, include the Jetty server dependency in your build file.
- Configure the server in your application. Create a configuration class and annotate it with @Configuration or @SpringBootApplication. Define a bean of the server type (e.g., JettyServer, UndertowServer) and customize it as needed.
Example for Jetty:
@SpringBootApplication
public class YourApplication {
@Bean
public Server jettyServer() {
return new Server(8080); // Customize the server configuration as per your needs
}
}Other useful articles for Java developer
Free PDF’s from @javinpaul from @javarevisited
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Grokking the Spring Boot Interview [Free Sample Copy]
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