Solution: You can process every bean before initialization callback method by implementing the postProcessBeforeInitialization() and methods.

Solution: You can process every bean after initialization callback method by implementing the postProcessAfterInitialization() and methods.

Solution: ShutdownHook method gracefully shuts down each bean process before closing the container.

Solution: When using a bean factory as your IoC container, bean post processors can only be registered programmatically, or more accurately, via the addBeanPostProcessor() method.

Solution: First of all, for the bean post processor to distinguish which beans should be checked, you create a marker interface, StorageConfig, for your target beans to implement.

Solution: Moreover, for your bean post processor to check for path existence, it must be able to access the path property. This can be done by adding the getPath() method to this interface.

Solution: This is because your bean post processor has a lower priority than CommonAnnotationBeanPostProcessor by default. As a result, the initialization method will be called before your path checking.

Solution: Spring comes with a bean factory post processor called PropertyPlaceholderConfigurer for you to externalize part of the bean configurations into a properties file.

Solution: MessageSource is an interface that defines several methods for resolving messages.

Solution: For a bean to listen to certain events, it must implement the ApplicationListener interface and handle the events in the onApplicationEvent() method.