Description: The ‘ApplicationStartup’ in the context of Spring Boot refers to an interface that provides access to application startup events. This functionality is crucial for the lifecycle of a Spring Boot application, as it allows developers to execute specific code at key moments during the boot process. For example, events can be logged, resources initialized, or custom configurations executed. The interface enables developers to subscribe to startup events, facilitating the implementation of additional logic that may be necessary before the application is fully operational. Furthermore, this feature is part of Spring Boot’s approach to simplifying application development, allowing developers to focus on business logic without worrying about the underlying infrastructure. In summary, ‘ApplicationStartup’ is a powerful tool that enhances flexibility and customization in the development of applications with Spring Boot.