Chapter 12: Understanding SpringApplication.run() Method Internals | Spring Boot Course

Explore how Spring Boot’s run() method works internally. Learn what happens behind the scenes when a Spring Boot application starts.

Previous Chapter:

Chapter 13: Understanding @SpringBootApplication Annotation | Spring Boot Course

Introduction

Inside the main entry point class of Spring Boot, you can see the run() method:

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

Spring Boot applications always start with one familiar line:

SpringApplication.run(MyApp.class, args);

It looks simple, but behind the scenes, this line does a lot of heavy lifting.

In this chapter, we’ll explore:

• 🔍 What the run() method really does
• 🧩 Step-by-step flow inside SpringApplication
• 🛠️ Internal components involved in the startup process

📌 Basic Example