How does Spring Boot automatically configure its components and dependencies?

Spring Boot uses an auto-configuration mechanism based on the @EnableAutoConfiguration annotation. When starting a Spring Boot application, it scans the classpath and automatically configures the necessary beans and components based on the presence of certain libraries and classes.

For example, if a database library (such as H2 or MySQL) is present in the classpath, Spring Boot will automatically create a DataSource and configure the database connection. This is achieved through special spring.factories files that specify which configurations to apply when certain conditions are met.

An example of using auto-configuration:

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

Thus, developers do not need to manually write many configurations — Spring Boot does this for them based on the context and project dependencies.