1. What is Spring Boot?<\/strong><\/h4>\n\n\n\nAnswer:<\/strong>
Spring Boot is an open-source framework built on top of the Spring Framework. It simplifies the development of stand-alone, production-grade Spring applications by providing auto-configuration, embedded servers, and opinionated defaults.<\/p>\n\n\n\n2. How is Spring Boot different from the traditional Spring Framework?<\/strong><\/h4>\n\n\n\nAnswer:<\/strong>
Spring Boot reduces boilerplate configuration by offering:<\/p>\n\n\n\n\n- Auto-configuration of beans and components<\/li>\n\n\n\n
- Embedded web servers like Tomcat or Jetty<\/li>\n\n\n\n
- Convention over configuration<\/li>\n\n\n\n
- Minimal XML setup
Traditional Spring requires extensive manual configuration and external server deployment.<\/li>\n<\/ul>\n\n\n\n3. What is the role of the @SpringBootApplication<\/code> annotation?<\/strong><\/h4>\n\n\n\nAnswer:<\/strong>
@SpringBootApplication<\/code> is a meta-annotation that combines:<\/p>\n\n\n\n\n@Configuration<\/code><\/li>\n\n\n\n@EnableAutoConfiguration<\/code><\/li>\n\n\n\n@ComponentScan<\/code>
It marks the main class and enables component scanning and auto-configuration.<\/li>\n<\/ul>\n\n\n\n4. How do you run a Spring Boot application?<\/strong><\/h4>\n\n\n\nAnswer:<\/strong>
A Spring Boot application can be run using:<\/p>\n\n\n\n\n- The
main()<\/code> method with SpringApplication.run()<\/code><\/li>\n\n\n\n- The command
mvn spring-boot:run<\/code> or gradle bootRun<\/code><\/li>\n\n\n\n- Executing the generated
.jar<\/code> file with java -jar<\/code><\/li>\n<\/ul>\n\n\n\n5. What is the default port of a Spring Boot application?<\/strong><\/h4>\n\n\n\nAnswer:<\/strong>
By default, Spring Boot applications run on port 8080 when using an embedded server like Tomcat.<\/p>\n\n\n\n6. How do you change the default port of a Spring Boot application?<\/strong><\/h4>\n\n\n\nAnswer:<\/strong>
You can change the port in application.properties<\/code>:<\/p>\n\n\n\nserver.port=9090
<\/code><\/pre>\n\n\n\nor in application.yml<\/code>:<\/p>\n\n\n\nserver:
port: 9090
<\/code><\/pre>\n\n\n\n7. What are Spring Boot Starters?<\/strong><\/h4>\n\n\n\nAnswer:<\/strong>
Starters are dependency descriptors that simplify Maven or Gradle configurations. They bundle commonly used dependencies for specific functionalities.
Example:<\/p>\n\n\n\n\nspring-boot-starter-web<\/code> (for building web apps and RESTful APIs)<\/li>\n\n\n\nspring-boot-starter-data-jpa<\/code> (for JPA and Hibernate integration)<\/li>\n<\/ul>\n\n\n\n8. What is auto-configuration in Spring Boot?<\/strong><\/h4>\n\n\n\nAnswer:<\/strong>
Auto-configuration automatically sets up application beans based on classpath settings, property files, and annotations. It reduces the need for manual configuration.<\/p>\n\n\n\n9. How is dependency management handled in Spring Boot?<\/strong><\/h4>\n\n\n\nAnswer:<\/strong>
Spring Boot uses a parent POM<\/strong> that provides dependency versions. You can include only the necessary dependencies without specifying version numbers, ensuring compatibility.<\/p>\n\n\n\n10. What is the difference between @Component<\/code>, @Service<\/code>, and @Repository<\/code>?<\/strong><\/h4>\n\n\n\nAnswer:<\/strong>
All three are specializations of @Component<\/code> and enable component scanning:<\/p>\n\n\n\n\n@Component<\/code>: Generic component<\/li>\n\n\n\n@Service<\/code>: Business logic layer<\/li>\n\n\n\n@Repository<\/code>: Data access layer (with exception translation enabled)<\/li>\n<\/ul>\n\n\n\n11. What is the use of application.properties<\/code> or application.yml<\/code>?<\/strong><\/h4>\n\n\n\nAnswer:<\/strong>
These files store external configuration settings such as port number, database URL, logging levels, and custom properties. They allow environment-specific and centralized configuration.<\/p>\n\n\n\n12. What is the use of the @RestController<\/code> annotation?<\/strong><\/h4>\n\n\n\nAnswer:<\/strong>
@RestController<\/code> is a combination of @Controller<\/code> and @ResponseBody<\/code>. It is used to build RESTful web services and automatically serializes return values into JSON or XML.<\/p>\n\n\n\n13. How can you create a simple REST endpoint in Spring Boot?<\/strong><\/h4>\n\n\n\nAnswer:<\/strong><\/p>\n\n\n\n@RestController
public class HelloController {
@GetMapping(\"\/hello\")
public String hello() {
return \"Hello, World!\";
}
}<\/code><\/pre>\n\n\n\n14. What is the purpose of the @RequestMapping<\/code> annotation?<\/strong><\/h4>\n\n\n\nAnswer:<\/strong>
@RequestMapping<\/code> is used to map web requests to controller methods. It supports various HTTP methods through attributes like method = RequestMethod.GET<\/code>.<\/p>\n\n\n\n15. How do you handle dependency injection in Spring Boot?<\/strong><\/h4>\n\n\n\nAnswer:<\/strong>
Spring Boot handles dependency injection using annotations:<\/p>\n\n\n\n\n@Autowired<\/code> for field or constructor injection<\/li>\n\n\n\n@Component<\/code>, @Service<\/code>, @Repository<\/code> to define beans<\/li>\n\n\n\n- Constructor-based injection is preferred for testability and immutability<\/li>\n<\/ul>\n\n\n\n
Intermediate-Level Spring Boot Interview Questions (16\u201330)<\/h3>\n\n\n\n16. What is the difference between @ComponentScan<\/code> and @EnableAutoConfiguration<\/code>?<\/strong><\/h4>\n\n\n\nAnswer:<\/strong><\/p>\n\n\n\n\n@ComponentScan<\/code>: Tells Spring where to look for annotated components (like @Service<\/code>, @Controller<\/code>) for dependency injection.<\/li>\n\n\n\n@EnableAutoConfiguration<\/code>: Enables Spring Boot\u2019s auto-configuration mechanism, allowing the framework to automatically configure beans based on classpath dependencies.<\/li>\n<\/ul>\n\n\n\n17. What is Spring Boot DevTools and why is it useful?<\/strong><\/h4>\n\n\n\nAnswer:<\/strong>
spring-boot-devtools<\/code> is a development-time dependency that provides features like automatic restarts, live reload, and configuration caching. It improves developer productivity by reflecting changes without restarting the application manually.<\/p>\n\n\n\n18. How do you configure a Spring Boot application to connect to a database?<\/strong><\/h4>\n\n\n\nAnswer:<\/strong>
By setting properties in application.properties<\/code> or application.yml<\/code>, for example:<\/p>\n\n\n\nspring.datasource.url=jdbc:mysql:\/\/localhost:3306\/mydb
spring.datasource.username=root
spring.datasource.password=pass
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver<\/code><\/pre>\n\n\n\n19. What is @Value<\/code> annotation used for in Spring Boot?<\/strong><\/h4>\n\n\n\nAnswer:<\/strong>
@Value<\/code> is used to inject property values into fields from external configuration files.
Example:@Value(\"${server.port}\")
private int port;<\/code><\/p>\n\n\n\n20. How do you handle exceptions in Spring Boot REST APIs?<\/strong><\/h4>\n\n\n\nAnswer:<\/strong>
By using @ControllerAdvice<\/code> and @ExceptionHandler<\/code> annotations:<\/p>\n\n\n\n@ControllerAdvice
public class GlobalExceptionHandler {
@ExceptionHandler(ResourceNotFoundException.class)
public ResponseEntity<String> handleNotFound(ResourceNotFoundException ex) {
return new ResponseEntity<>(ex.getMessage(), HttpStatus.NOT_FOUND);
}
}<\/code><\/pre>\n\n\n\n21. What is the use of @Entity<\/code> and @Table<\/code> in Spring Boot?<\/strong><\/h4>\n\n\n\nAnswer:<\/strong><\/p>\n\n\n\n\n@Entity<\/code>: Marks a class as a JPA entity to be mapped to a database table.<\/li>\n\n\n\n@Table<\/code>: Optionally specifies the name of the table (if different from the class name).<\/li>\n<\/ul>\n\n\n\n22. What is Spring Data JPA and why is it used in Spring Boot?<\/strong><\/h4>\n\n\n\nAnswer:<\/strong>
Spring Data JPA simplifies database access by eliminating boilerplate code for repositories. It supports CRUD operations, pagination, and custom queries with method naming conventions or @Query<\/code>.<\/p>\n\n\n\n23. What is the difference between CrudRepository<\/code>, JpaRepository<\/code>, and PagingAndSortingRepository<\/code>?<\/strong><\/h4>\n\n\n\nAnswer:<\/strong><\/p>\n\n\n\n\nCrudRepository<\/code>: Basic CRUD functionality<\/li>\n\n\n\nPagingAndSortingRepository<\/code>: Adds pagination and sorting capabilities<\/li>\n\n\n\nJpaRepository<\/code>: Extends both and adds JPA-specific operations (e.g., batch inserts)<\/li>\n<\/ul>\n\n\n\n24. How do you enable CORS in a Spring Boot application?<\/strong><\/h4>\n\n\n\nAnswer:<\/strong>
Using @CrossOrigin<\/code> annotation:<\/p>\n\n\n\n@CrossOrigin(origins = \"http:\/\/example.com\")
@GetMapping(\"\/api\/data\")
public String getData() {
return \"Some data\";
}<\/code><\/pre>\n\n\n\n25. How do you secure endpoints using Spring Security in Spring Boot?<\/strong><\/h4>\n\n\n\nAnswer:<\/strong>
By adding spring-boot-starter-security<\/code> and creating a security configuration class:<\/p>\n\n\n\n@EnableWebSecurity
public class SecurityConfig extends WebSecurityConfigurerAdapter {
@Override
protected void configure(HttpSecurity http) throws Exception {
http.authorizeRequests()
.anyRequest().authenticated()
.and().httpBasic();
}
}
<\/code><\/pre>\n\n\n\n26. What is the difference between @RestController<\/code> and @Controller<\/code>?<\/strong><\/h4>\n\n\n\nAnswer:<\/strong><\/p>\n\n\n\n\n@RestController<\/code>: Returns data directly (e.g., JSON) without a view<\/li>\n\n\n\n@Controller<\/code>: Returns a view (typically used with web templates like Thymeleaf)<\/li>\n<\/ul>\n\n\n\n27. How do you read a custom property value in Spring Boot?<\/strong><\/h4>\n\n\n\nAnswer:<\/strong>
Using @ConfigurationProperties<\/code>:<\/p>\n\n\n\n@ConfigurationProperties(prefix = \"myapp\")
public class MyAppConfig {
private String name;
\/\/ getters and setters
}
<\/code><\/pre>\n\n\n\nOr using @Value(\"${myapp.name}\")<\/code> directly.<\/p>\n\n\n\n28. What are profiles in Spring Boot and how do you use them?<\/strong><\/h4>\n\n\n\nAnswer:<\/strong>
Profiles allow you to define different configurations for different environments (e.g., dev, test, prod). You can activate a profile using:<\/p>\n\n\n\npropertiesCopyEditspring.profiles.active=dev\n<\/code><\/pre>\n\n\n\nAnd annotate config classes or beans using @Profile(\"dev\")<\/code><\/p>\n\n\n\n29. How do you implement logging in Spring Boot?<\/strong><\/h4>\n\n\n\nAnswer:<\/strong>
Spring Boot supports logging with Logback, Log4j2, or Java Util Logging. You can configure it via application.properties<\/code>:<\/p>\n\n\n\nlogging.level.org.springframework=INFO
logging.file.name=app.log
<\/code><\/pre>\n\n\n\nUse Logger<\/code> in classes:<\/p>\n\n\n\nprivate static final Logger logger = LoggerFactory.getLogger(MyClass.class);