Spring Boot Basics

Introduction

Spring Boot is the most popular framework for building Java backends. It bundles Spring + auto-configuration + an embedded server so you go from main() to a running HTTP service in minutes.

Informative example

A complete REST endpoint in 15 lines:

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.*;

@SpringBootApplication
@RestController
public class HelloApp {

    public static void main(String[] args) {
        SpringApplication.run(HelloApp.class, args);
    }

    @GetMapping("/hello/{name}")
    public Hello hello(@PathVariable String name) {
        return new Hello("Hello, " + name);
    }

    record Hello(String message) {}
}

Best practices

• Use Spring Initializr (start.spring.io) to scaffold new projects.
• Keep controllers thin — push business logic into @Service beans.
• Externalise config in application.yml, not hard-coded constants.

Purpose of this lesson

Master Spring Boot Basics so you can apply it confidently in production Java code, technical interviews, and code reviews.

Step-by-step explanation

1. Understand the core idea behind Spring Boot Basics.
2. Walk through the runnable example and tweak it in the playground.
3. Apply the pattern in a small Spring Boot or CLI exercise of your own.
4. Re-read the common mistakes and interview Q&A to lock the concept in.

Interactive workflow diagram

Useful template

@SpringBootApplication
public class App {
  public static void main(String[] args) { SpringApplication.run(App.class, args); }
}

Debugging tips

• Read the full stack trace — Java's exception messages name the offending class and line.
• Reproduce in the smallest possible main() method before fixing in the real app.
• Use IntelliJ's debugger breakpoints and 'Evaluate Expression' rather than scattering System.out.

Optimization strategies

• Profile before optimizing — JFR (Java Flight Recorder) and async-profiler reveal real hotspots.
• Prefer immutable data and stream pipelines over hand-rolled loops when readability matters.
• Reach for the right JDK collection (ArrayList vs LinkedList vs ArrayDeque) before writing custom data structures.

Enterprise example

Teams at Netflix, Uber and Goldman Sachs apply Spring Boot Basics daily — usually wrapped behind Spring Boot services with observability hooks (Micrometer + OpenTelemetry).

Interview questions & answers

Summary

In this lesson you learned Spring Boot Basics — the concept, syntax, a runnable example, and the production pitfalls to avoid. Apply it in the playground before moving on.