spring boot项目@Async注解

@Component
public class AService {
    @Resource
    private BService bService;
    @Async
    public void save() {
    }
}
@Component
public class BService {
    @Resource
    private AService aService;
}

@Override
public Object applyBeanPostProcessorsAfterInitialization(Object existingBean, String beanName)throws BeansException {
    Object result = existingBean;
    for (BeanPostProcessor processor : getBeanPostProcessors()) {
         Object current = processor.postProcessAfterInitialization(result, beanName);
         if (current == null) {
            return result;
         }
         result = current;
     }
    return result;
}

@Override
public Object postProcessAfterInitialization(Object bean, String beanName) {
    if (this.advisor == null || bean instanceof AopInfrastructureBean) {
   // Ignore AOP infrastructure such as scoped proxies.
        return bean;
    }
    if (bean instanceof Advised) {
       Advised advised = (Advised) bean;
       if (!advised.isFrozen() && isEligible(AopUtils.getTargetClass(bean))) {
           // Add our local Advisor to the existing proxy's Advisor chain...
           if (this.beforeExistingAdvisors) {
              advised.addAdvisor(0, this.advisor);
           }
           else {
              advised.addAdvisor(this.advisor);
           }
           return bean;
        }
     }
     if (isEligible(bean, beanName)) {
        ProxyFactory proxyFactory = prepareProxyFactory(bean, beanName);
        if (!proxyFactory.isProxyTargetClass()) {
           evaluateProxyInterfaces(bean.getClass(), proxyFactory);
        }
        proxyFactory.addAdvisor(this.advisor);
        customizeProxyFactory(proxyFactory);
        return proxyFactory.getProxy(getProxyClassLoader());
     }
     // No proxy needed.
     return bean;
}

@Override
public Object postProcessAfterInitialization(@Nullable Object bean, String beanName) throws BeansException {
    if (bean != null) {
       Object cacheKey = getCacheKey(bean.getClass(), beanName);
       if (!this.earlyProxyReferences.contains(cacheKey)) {
           //生成动态代理，如果需要被代理的话
           return wrapIfNecessary(bean, beanName, cacheKey);
       }
     }
    return bean;
}

addSingletonFactory(beanName, () -> getEarlyBeanReference(beanName, mbd, bean));

protected void addSingletonFactory(String beanName, ObjectFactory<?> singletonFactory) {
    Assert.notNull(singletonFactory, "Singleton factory must not be null");
    synchronized (this.singletonObjects) {
       if (!this.singletonObjects.containsKey(beanName)) {
           this.singletonFactories.put(beanName, singletonFactory);
           this.earlySingletonObjects.remove(beanName);
           this.registeredSingletons.add(beanName);
       }
    }
}

protected Object getEarlyBeanReference(String beanName, RootBeanDefinition mbd, Object bean) {
    Object exposedObject = bean;
    if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
        for (BeanPostProcessor bp : getBeanPostProcessors()) {
            if (bp instanceof SmartInstantiationAwareBeanPostProcessor) {
               SmartInstantiationAwareBeanPostProcessor ibp = (SmartInstantiationAwareBeanPostProcessor) bp;
               exposedObject = ibp.getEarlyBeanReference(exposedObject, beanName);
            }
       }
    }
    return exposedObject;
}

@Override
public Object getEarlyBeanReference(Object bean, String beanName) throws BeansException {
    Object cacheKey = getCacheKey(bean.getClass(), beanName);
    if (!this.earlyProxyReferences.contains(cacheKey)) {
        this.earlyProxyReferences.add(cacheKey);
    }
    return wrapIfNecessary(bean, beanName, cacheKey);
}

if (earlySingletonExposure) {
  // 获取到早期暴露出去的对象
  Object earlySingletonReference = getSingleton(beanName, false);
  if (earlySingletonReference != null) {
      // 早期暴露的对象不为null，说明出现了循环依赖
      if (exposedObject == bean) {
          // 这个判断的意思就是指 postProcessAfterInitialization 回调没有进行动态代理，如果没有那么就将早期暴露出去的对象赋值给最终暴露（生成）出去的对象，
          // 这样就实现了早期暴露出去的对象和最终生成的对象是同一个了
          // 但是一旦 postProcessAfterInitialization 回调生成了动态代理 ，那么就不会走这，也就是加了@Aysnc注解，是不会走这的
          exposedObject = earlySingletonReference;
      }
      else if (!this.allowRawInjectionDespiteWrapping && hasDependentBean(beanName)) {
               // allowRawInjectionDespiteWrapping 默认是false
               String[] dependentBeans = getDependentBeans(beanName);
               Set<String> actualDependentBeans = new LinkedHashSet<>(dependentBeans.length);
               for (String dependentBean : dependentBeans) {
                   if (!removeSingletonIfCreatedForTypeCheckOnly(dependentBean)) {
                       actualDependentBeans.add(dependentBean);
                  }
               }
               if (!actualDependentBeans.isEmpty()) {
                   //抛出异常
                   throw new BeanCurrentlyInCreationException(beanName,
                           "Bean with name '" + beanName + "' has been injected into other beans [" +
                           StringUtils.collectionToCommaDelimitedString(actualDependentBeans) +
                           "] in its raw version as part of a circular reference, but has eventually been " +
                           "wrapped. This means that said other beans do not use the final version of the " +
                           "bean. This is often the result of over-eager type matching - consider using " +
                           "'getBeanNamesOfType' with the 'allowEagerInit' flag turned off, for example.");
               }
      }
   }
}

@Component
public class AService {
    @Resource
    @Lazy
    private BService bService;
    @Async
    public void save() {
    }
}

@Component
public class MyBeanFactoryPostProcessor implements BeanFactoryPostProcessor {
    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
        ((DefaultListableBeanFactory) beanFactory).setAllowRawInjectionDespiteWrapping(true);
    }
}