Spring Boot Interview Questions And Answers
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Best Spring Boot Interview Questions and Answers
Preparing for a Spring Boot interview? Whether you’re a fresher starting your career in Java development or an experienced professional looking to advance your skills, having a solid understanding of Spring Boot concepts is essential. Spring Boot is one of the most popular frameworks for building enterprise-grade Java applications and RESTful web services, making it a highly sought-after skill among employers. In this article, we’ve compiled the Top 50 Spring Boot Interview Questions and Answers covering core concepts, annotations, Spring Data JPA, REST APIs, dependency injection, security, microservices, and best practices. These carefully selected questions will help you strengthen your technical knowledge, boost your confidence, and prepare effectively for your next Spring Boot interview.
Spring Boot is an extension of the Spring Framework that simplifies the development of Java applications by providing auto-configuration, embedded servers, starter dependencies, and production-ready features.
- Auto Configuration
- Embedded Tomcat, Jetty, or Undertow
- Starter Dependencies
- Minimal XML Configuration
- Production-ready Actuator
- Faster application development
Auto Configuration automatically configures Spring beans based on the dependencies available in the classpath, reducing manual configuration.
Spring Boot Starters are pre-configured dependency packages that simplify dependency management.
Examples:
- spring-boot-starter-web
- spring-boot-starter-data-jpa
- spring-boot-starter-security
- spring-boot-starter-test
It combines:
- @Configuration
- @EnableAutoConfiguration
- @ComponentScan
into a single annotation.
Spring Initializr is a web-based tool that generates a Spring Boot project with selected dependencies.
An embedded server (Tomcat, Jetty, Undertow) runs inside the application, eliminating the need to deploy WAR files separately.
| Spring | Spring Boot |
|---|---|
| Requires manual configuration | Auto configuration |
| External server required | Embedded server |
| More setup | Less setup |
| XML-heavy | Annotation-based |
Dependency Injection is a design pattern where Spring automatically provides required objects instead of creating them manually.
Actuators provide production-ready endpoints to monitor application health, metrics, beans, environment properties, and more.
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Apache Tomcat.
server.port=9090
It is the configuration file used to store application settings like database credentials, server port, logging, etc.
A YAML-based alternative to application.properties.
Example:
port: 8081
It combines:
- @Controller
- @ResponseBody
Used for creating REST APIs.
@Controller returns views.
@RestController returns JSON/XML responses.
Maps HTTP requests to controller methods.
Handles HTTP GET requests.
@GetMapping(“/users”)
Handles HTTP POST requests.
Handles HTTP PUT requests for updating resources.
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Handles HTTP DELETE requests.
Retrieves query parameters from the URL.
@GetMapping
public String get(@RequestParam String name)
Extracts values from the URL path.
@GetMapping(“/user/{id}”)
Converts incoming JSON into a Java object.
Returns the object directly as JSON instead of rendering a view.
Spring Data JPA simplifies database access by reducing boilerplate code using repositories.
It provides CRUD operations along with pagination and sorting.
CrudRepository provides basic CRUD operations.
JpaRepository extends CrudRepository with JPA-specific features like pagination and batch operations.
Hibernate is the default ORM framework used by Spring Boot for mapping Java objects to database tables.
Object Relational Mapping converts Java objects into database tables automatically.
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Marks a Java class as a database table.
Specifies the primary key of an entity.
Automatically generates primary key values.
Automatically injects dependencies into Spring beans.
Registers a Java class as a Spring-managed bean.
- @Component: Generic Spring bean.
- @Service: Business logic layer.
- @Repository: Data access layer with exception translation.
Bean scope defines the lifecycle of a bean.
Common scopes:
- Singleton
- Prototype
- Request
- Session
Provides automatic restart and LiveReload during development.
Profiles allow different configurations for environments like development, testing, and production.
Example:
spring.profiles.active=devHandled using:
- @ExceptionHandler
- @ControllerAdvice
- @RestControllerAdvice
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Provides centralized exception handling across all controllers.
Spring Security provides authentication, authorization, password encryption, and protection against common security threats.
JSON Web Token (JWT) is a compact token used for secure authentication in REST APIs.
CORS allows web applications from different origins to access resources securely.
The /actuator/health endpoint displays the application’s health status.
Pagination retrieves data in smaller chunks using Pageable.
Caching improves performance by storing frequently accessed data in memory using annotations like @Cacheable.
Spring Boot is widely used to build independently deployable microservices that communicate through REST APIs or messaging systems.
Configure the database connection in application.properties:
spring.datasource.url=jdbc:mysql://localhost:3306/testdb
spring.datasource.username=root
spring.datasource.password=password
spring.jpa.hibernate.ddl-auto=update- Follow layered architecture.
- Use constructor-based dependency injection.
- Implement global exception handling.
- Validate user input.
- Externalize configuration.
- Secure APIs with Spring Security and JWT.
- Use logging frameworks like SLF4J and Logback.
- Write unit and integration tests.
- Monitor applications with Spring Boot Actuator.
- Optimize database queries and use caching where appropriate.
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