The Complete Lifecycle of a Spring Boot Application: From Start to Finish

source: bootcamptoprod.com/

Have you ever wondered what happens behind the scenes when you start a Spring Boot application? How does it go from a simple main() method call to a fully functioning web application? And what happens when you shut it down?

In this article, we’ll walk through the entire lifecycle of a Spring Boot application in plain language. We’ll look at each step from startup to shutdown and explain the key components that make it all work.

The Birth of a Spring Boot Application

Every Spring Boot application starts with a simple Java main() method. This is the entry point that kicks off the whole process. Here's what a typical Spring Boot starter class looks like:

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

This tiny block of code hides a complex sequence of events. Let’s break down what happens when you run this application.

Phase 1: The Bootstrap Phase

When you call SpringApplication.run(), you trigger the bootstrap phase. This is where Spring Boot prepares everything before creating the application context.