During the creation and initialization of beans, I've noticed that Spring iterates over all registered BeanPostProcessors for every bean, invoking each one that matches the current lifecycle phase through an instanceof check. Given that the number of BeanPostProcessors can grow quite large in complex applications, wouldn't this approach potentially cause performance overhead, especially during startup?
I was thinking, instead of having a single list for all BeanPostProcessors, why not categorize them according to their types (like InstantiationAwareBeanPostProcessor, MergedBeanDefinitionPostProcessor, etc.) and maintain separate lists for each category. This way, during each phase of the bean lifecycle, Spring could iterate over the appropriate list only, bypassing the instanceof checks.