Spring Boot

Spring Boot eliminates most Spring Framework boilerplate by providing sensible defaults through auto-configuration. It reads your classpath, detects what you have, and configures beans automatically via @Conditional rules. Understanding auto-configuration — not just using it — is what separates developers who can debug Spring Boot from those who can only use it.

What You'll Find Here

Topic	Description
Auto-Configuration	@SpringBootApplication, @EnableAutoConfiguration, @ConditionalOn* conditions.
Application Properties	application.yml, profiles, @ConfigurationProperties, @Value.
Spring Boot Starters	What's in a starter; common starters (web, data-jpa, security, test, actuator).
Actuator	Built-in endpoints (/health, /metrics); custom health indicators; securing endpoints.
Spring Boot Testing	@SpringBootTest, test slices (@WebMvcTest, @DataJpaTest), @MockBean.

Learning Path

1. Auto-Configuration — understanding @ConditionalOnClass and @ConditionalOnMissingBean demystifies 90% of Boot magic.
2. Application Properties — @ConfigurationProperties replaces scattered @Value for structured config; learn both.
3. Starters — know what spring-boot-starter-web wires up (Tomcat, Jackson, Spring MVC).
4. Actuator — essential for production; understand which endpoints to expose and how to secure them.
5. Testing — @WebMvcTest and @DataJpaTest slices are faster than @SpringBootTest; know when to use each.

Related Domains

• Spring Framework — Spring Boot runs on top of Spring Framework; understand the foundation first.
• Web & REST — Spring MVC and WebFlux are the web layer wired by spring-boot-starter-web.
• Testing — Spring Boot testing slices and Testcontainers integration are covered there.

Demos

Practical, hidden demo pages with runnable examples and step-by-step walkthroughs:

Hands-on step-by-step demos with runnable examples:

Demo	What It Shows
Auto-Configuration Demo	Observe auto-config condition evaluation, override defaults, and write a minimal auto-configuration.
Application Properties Demo	Profiles, @ConfigurationProperties binding, validation, and test property overrides.
Starters Demo	Inspect what common starters pull in, dependency-tree examples, and swapping embedded servers.
Actuator Demo	Expose and secure Actuator endpoints, custom health indicators, and Micrometer/Prometheus wiring.
Testing Demo	Unit → slice → integration → Testcontainers examples and context caching strategies.