Spring Boot

The standard Java framework for building enterprise applications and microservices — used across banking, insurance, healthcare, and large-scale e-commerce.

Spring Boot is the de-facto standard for enterprise Java development. It removes the configuration overhead of traditional Spring by providing opinionated defaults, embedded servers (Tomcat), and auto-configuration — developers can have a production-ready REST API running in minutes. Spring Boot powers the backend systems of financial institutions, insurance companies, healthcare platforms, and large retailers. Java/Spring Boot roles dominate enterprise job postings and consistently command some of the highest backend engineering salaries.

Typical time to job-readiness: ~3 months.

Learning Spring Boot

Beginner

Build a REST API with Spring Boot: define a model, use Spring Data JPA to connect to a database, and expose endpoints with a RestController. Learn how dependency injection and the application context work — it's the foundation of everything.

Intermediate

Spring Security for authentication and authorization (JWT, OAuth2), exception handling with @ControllerAdvice, writing tests with JUnit and Mockito, and Spring Data relationships (OneToMany, ManyToMany).

Advanced

Reactive programming with Spring WebFlux, microservices patterns (service discovery, circuit breakers with Resilience4j), Spring Cloud Config, and distributed tracing. Enterprise Spring interviews involve significant system design and concurrency questions.

Key concepts

  • Dependency injection — Spring manages object creation; you declare what you need via @Autowired or constructor injection
  • @RestController and @GetMapping/@PostMapping — annotations that map HTTP requests to Java methods
  • Spring Data JPA — repository interfaces that generate SQL automatically from method names
  • @Service, @Repository, @Component — stereotype annotations for organizing the application context
  • Spring Security — authentication and authorization framework; configure via SecurityFilterChain
  • application.properties / application.yml — external configuration for database URLs, secrets, and feature flags

Common interview topics

  • Explain how dependency injection works in Spring
  • What is the difference between @Component, @Service, and @Repository
  • How does Spring Data JPA work and what is a repository
  • How do you implement authentication in a Spring Boot application
  • Explain Spring Boot's auto-configuration mechanism

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