3.Spring Boot : IOC container and it's interface | Interview Question

The Spring framework's Inversion of Control (IoC) container is a core component that manages the creation, configuration, and wiring of application objects, also known as beans. The IoC container uses dependency injection to inject dependencies into beans, thus decoupling the components and facilitating easier testing and maintenance.

There are two main types of Spring IoC containers:

BeanFactory:

This is the simplest container providing the basic support for DI and is more lightweight. It's typically used in standalone applications with a limited number of beans and where eager initialization is not required.

ApplicationContext:

This is a more advanced container, extending the functionality of BeanFactory. It adds additional enterprise-specific features such as event propagation, internationalization, and message resource handling. ApplicationContext is typically used in enterprise-level applications.

Some common methods provided by the ApplicationContext interface include:

getBean(String name): Retrieves an instance of the specified bean by its name.

getBean(Class requiredType): Retrieves an instance of the specified bean by its class.

containsBean(String name): Checks if the container contains a bean with the given name.

getBeanDefinitionCount(): Returns the number of beans defined in the container.

getBeanNamesForType(Class type): Returns the names of beans of the given type.

registerShutdownHook(): Registers a shutdown hook with the JVM to close the application context gracefully.

Apart from the core ApplicationContext interface, there are several implementations available in Spring, such as ClassPathXmlApplicationContext, FileSystemXmlApplicationContext, AnnotationConfigApplicationContext, etc., each catering to different types of configuration styles and environments.

In summary, the Spring IoC container is a crucial part of the Spring framework, providing a powerful mechanism for managing dependencies and facilitating the development of loosely coupled, maintainable, and testable applications.