Introduction to Spring Boot

🌿 Spring BootLesson 1Beginner

Spring Boot is an opinionated, convention-over-configuration framework built on top of the Spring Framework. It eliminates boilerplate configuration and lets you build production-ready Java applications in minutes, not days.

1 Why Spring Boot?

Auto-configuration: Spring Boot auto-configures beans based on the JARs present on your classpath. No XML required.
Embedded Server: Ships with embedded Tomcat, Jetty, or Undertow — just run java -jar app.jar.
Starter POMs: Curated dependency sets (spring-boot-starter-web, spring-boot-starter-data-jpa, etc.) that eliminate version conflicts.
Actuator: Built-in production monitoring endpoints (/health, /metrics, /info).
Spring Ecosystem: Seamlessly integrates with Spring Security, Spring Data, Spring Cloud, and more.

2 Your First Spring Boot Application

Java — Main Application Class

package com.example.demo;

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

@SpringBootApplication  // Combines @Configuration + @EnableAutoConfiguration + @ComponentScan
@RestController
public class DemoApplication {

    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
        // Starts embedded Tomcat on port 8080
    }

    @GetMapping("/")
    public String hello() {
        return "Hello, Spring Boot!";
    }
}

3 Spring Boot vs Plain Spring

Feature	Plain Spring	Spring Boot
Configuration	XML or Java @Configuration	Auto-configured, minimal setup
Web Server	External (deploy WAR)	Embedded (run JAR)
Dependencies	Manual, version-managed	Starters with BOM
Startup Time	Slow (heavy XML)	Fast (lazy init option)
Production Ready	Manual setup	Actuator built-in

4 Code Challenge

Challenge: Create a Spring Boot app with two endpoints: GET /ping that returns {"status":"ok","timestamp":"..."} and GET /version that returns the app version from application.properties.