Master Spring Boot: Core Concepts, Configurations, and Best Practices

1. What is SpringBoot?

SpringBoot is a sub‑project of the Spring open‑source organization that provides an all‑in‑one solution for Spring components, simplifying usage by reducing configuration, offering starters, and enabling rapid development.

2. Advantages of SpringBoot

Reduces development and testing time.

JavaConfig avoids XML.

Eliminates heavy Maven imports and version conflicts.

Provides opinionated development approach.

Quick start with default values.

No separate web server needed; embedded Tomcat/Jetty.

Less configuration; no web.xml, use @Configuration and @Bean, optional @Autowired.

Environment‑specific configuration can be passed via: -Dspring.profiles.active={environment} After loading the main application properties, Spring loads additional properties from (application{environment}.properties).

3. Core configuration files and differences

application and bootstrap files.

application file is for Spring Boot’s auto‑configuration.

bootstrap is used for Spring Cloud Config, immutable properties, encryption scenarios.

4. Configuration file formats

SpringBoot supports .properties and .yml files, differing only in syntax. app.user.name=javastack YAML example:

app:
  user:
    name: javastack

5. Core annotation

The main annotation is @SpringBootApplication, which combines: @SpringBootConfiguration (includes @Configuration). @EnableAutoConfiguration (can exclude specific auto‑config, e.g., DataSourceAutoConfiguration). @ComponentScan.

6. Ways to enable SpringBoot features

Inherit from spring-boot-starter-parent.

Import spring-boot-dependencies dependencies.

7. Does SpringBoot need an external container?

No, it embeds containers such as Tomcat or Jetty.

8. Ways to run SpringBoot

Package and run the jar or deploy to a container.

Run via Maven/Gradle plugin.

Execute the main method directly.

9. Auto‑configuration principle

Annotations like @EnableAutoConfiguration, @Configuration, and @ConditionalOnClass drive auto‑configuration based on classpath presence.

10. New features in SpringBoot 2.x

Configuration changes.

JDK version upgrades.

Third‑party library updates.

Reactive Spring support.

HTTP/2 support.

Configuration property binding.

Various improvements.

11. Pagination and sorting

Use Spring Data JPA; pass org.springframework.data.domain.Pageable to repository methods.

12. Implementing security

Add spring-boot-starter-security and create a configuration class extending WebSecurityConfigurerAdapter to override methods.

13. Integrating ActiveMQ

Include spring-boot-starter-activemq dependency; minimal configuration required.

14. What is YAML?

Human‑readable data serialization language.

Commonly used for configuration files.

Provides hierarchical, less confusing structure compared with properties files.

15. SpringBoot Actuator

Provides production‑ready monitoring endpoints.

Exposes health, metrics, and other info via HTTP URLs.

16. Swagger

Swagger visualizes APIs, offering an online sandbox via Swagger UI, generating RESTful documentation that stays in sync with the server.

17. Exception handling

Use @ControllerAdvice to handle exceptions globally by implementing a class annotated with it.

18. RequestMapping vs GetMapping

@RequestMapping

supports multiple HTTP methods; @GetMapping is a shortcut for GET requests, improving clarity.

19. Compatibility with legacy Spring projects

Use @ImportResource to import old Spring XML configuration files.

20. Protecting SpringBoot applications

Use HTTPS and dependency scanning tools.

Upgrade to latest versions.

Enable CSRF protection.

Apply Content‑Security‑Policy to prevent XSS.

21. Difference between SpringBoot executable jar and regular jar

SpringBoot produces an executable jar that runs with java -jar and cannot be used as a normal library; its classes reside under BOOT-INF/classes. To create a regular jar, configure the build to produce two artifacts.

22. Scheduling tasks

SpringBoot supports scheduling via the @Scheduled annotation or by integrating the Quartz framework.