spring中service类代理的加载过程

@RestController
public class HelloController {
    @Autowired
    UserService userService;
}
@Service
public class UserServiceImpl implements UserService {

}

关键步骤

• spring容器初始化HelloController
• 属性填充userService
• AutowiredAnnotationBeanPostProcessor完成userService填充
• spring容器初始化userService
• AnnotationAwareAspectJAutoProxyCreator将userService封装成代理类

流程

org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#doCreateBean创建bean
	createBeanInstance创建HelloController实例
	populateBean属性设置（设置UserService）
		AutowiredAnnotationBeanPostProcessor#postProcessProperties设置Autowired属性
			findAutowiringMetadata查找所有需要注入的属性
			metadata.inject属性注入
				element.inject(target, beanName, pvs)
					org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.AutowiredFieldElement#inject
						beanFactory.resolveDependency从beanFactory中获取需要注入的对象
						field.set(bean, value);利用反射进行属性设置
	initializeBean初始化完成后的一些后置操作，userService创建时会在此处创建代理

@Autowired注解

Note that actual injection is performed through a BeanPostProcessor which in turn means that you cannot use @Autowired to inject references into BeanPostProcessor or BeanFactoryPostProcessor types. Please consult the javadoc for the AutowiredAnnotationBeanPostProcessor class (which, by default, checks for the presence of this annotation).

请注意，实际的注入是通过BeanPostProcessor执行的，这意味着您不能使用@Autowired将引用注入到BeanPostProcessor或BeanFactoryPostProcessor类型中。请咨询javadoc以获得AutowiredAnnotationBeanPostProcessor类(在默认情况下，该类检查是否存在此注释)。

@Autowired通过AutowiredAnnotationBeanPostProcessor来完成注入

AutowiredAnnotationBeanPostProcessor类

主要靠这个类完成属性注入

参考

• https://blog.csdn.net/qq_26344609/article/details/78905985