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Sudhakar V
Sudhakar V

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SpringBoot

Spring Boot is an opinionated, convention-over-configuration layer built on top of the Spring Framework that makes it fast and easy to create production-ready, stand-alone Spring applications. Rather than assembling and wiring dozens of Spring modules yourself, Spring Boot provides:

🚀 Key Principles & Features

Feature What It Does
Auto-Configuration Scans your classpath and beans, then applies sensible defaults (e.g. an embedded Tomcat).
Starter POMs Curated “starters” (Maven/Gradle) group common dependencies (e.g. spring-boot-starter-web).
Embedded Server Bundles Tomcat/Jetty/Undertow so you can java -jar your app—no external WAR required.
Production-Ready Includes Actuator endpoints for health, metrics, tracing, logging, and more, out of the box.
Externalized Config Reads properties from application.properties/application.yml, environment variables, etc.
Spring CLI Optional command-line tool for running and testing Groovy scripts as microservices.
DevTools Enables hot-reload, automatic restart, and live livereload during development.

⚙️ Getting Started

  1. Generate a Project Use Spring Initializr (https://start.spring.io) or your IDE’s Spring Boot wizard.
  • Choose your build tool (Maven/Gradle), Java version, and starters (e.g. Web, Data JPA, Security).
  1. Project Structure 
   my-app/
   ├── src/
   │   ├── main/
   │   │   ├── java/com/example/demo/
   │   │   │   └── DemoApplication.java
   │   │   └── resources/
   │   │       ├── application.properties
   │   │       └── static/ (CSS/JS/images)
   │   └── test/java/com/example/demo/
   └── pom.xml or build.gradle
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  1. Minimal Application 
   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
   public class DemoApplication {
       public static void main(String[] args) {
           SpringApplication.run(DemoApplication.class, args);
       }
   }

   @RestController
   class HelloController {
       @GetMapping("/hello")
       String sayHello() {
           return "Hello, Spring Boot!";
       }
   }
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  • @SpringBootApplication = @Configuration + @EnableAutoConfiguration + @ComponentScan
  • Run with mvn spring-boot:run or java -jar target/demo-0.0.1-SNAPSHOT.jar

🔧 Core Components

1. Starters

Artifact Purpose
spring-boot-starter-web Spring MVC + embedded Tomcat + Jackson
spring-boot-starter-data-jpa Spring Data JPA + Hibernate
spring-boot-starter-security Spring Security
spring-boot-starter-test JUnit, Mockito, Spring Test utilities

2. Auto-Configuration

  • Picks up beans and jars on the classpath
  • Applies defaults (e.g., if spring-webmvc is present, configures a DispatcherServlet)
  • You can override or disable specific auto-configs via @EnableAutoConfiguration(exclude = ...) or properties

3. Actuator

Add spring-boot-starter-actuator to expose endpoints like:

/actuator/health
/actuator/info
/actuator/metrics
/actuator/loggers
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Customize via management.endpoints.web.exposure.include=* in application.properties.

4. Externalized Configuration

  • Profile-specific properties: 
  # application.yml
  spring:
    profiles:
      active: dev

  ---
  spring:
    profiles: dev
  server:
    port: 8081
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  • Environment variables, command-line args, and property files are merged in a well-defined order.

📦 Packaging & Deployment

  • Fat JAR: All dependencies + embedded server → single runnable JAR.
  • Docker: Commonly containerized: 
  FROM eclipse-temurin:17-jdk-alpine
  ARG JAR_FILE=target/*.jar
  COPY ${JAR_FILE} app.jar
  ENTRYPOINT ["java","-jar","/app.jar"]
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  • Cloud-Ready: Spring Boot’s 12-factor support (config, logging, ports) plays nicely with platforms like Kubernetes, Cloud Foundry, and Heroku.

🌐 When to Use Spring Boot

  • Microservices: Rapidly build and deploy small, focused services.
  • Greenfield Projects: Start with sensible defaults and conventions.
  • Cloud Native: Easy scaling, containerization, and monitoring.
  • Prototyping: Run simple HTTP endpoints or CLI scripts with minimal setup.

Next Steps

  • Deep Dive into custom auto-configurers and conditional beans.
  • Secure your endpoints with spring-boot-starter-security and JWT/OAuth.
  • Persist data via spring-boot-starter-data-jpa and transaction management.
  • Monitor your services with Actuator and integrate with Prometheus/Grafana.

Let me know which area you’d like to explore further—examples on data access, security configs, custom health indicators, or something else!

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