How does @autowired work?

After the above steps, you will AutowiredAnnotationBeanPostProcessor RootBeanDefinition into beanDefinitionMap, the class hierarchy is as follows:

Implement the PriorityOrdered interface, mainly implement getOrder() method, used for sorting; Implement BeanFactoryAware interface, implement setBeanFactory method, assign value to beanFactory through Aware callback; Implement MergedBeanDefinitionPostProcessor interface: 1, 2, resetBeanDefinition SmartInstantiationAwareBeanPostProcessor postProcessMergedBeanDefinition interface: 1, determineCandidateConstructors InstantiationAwareBeanPostProcessor interface: 1, postProcessPropertiesCopy the code

Take a look at his unique constructor:

A few notes from @autowired: