spring中单例实例的循环依赖spring中单例实例的循环依赖

boolean earlySingletonExposure = (mbd.isSingleton() && this.allowCircularReferences &&    isSingletonCurrentlyInCreation(beanName));  if (earlySingletonExposure) {   if (logger.isTraceEnabled()) {    logger.trace(\"Eagerly caching bean '\" + beanName +      \"' to allow for resolving potential circular references\

BeanUtils

Bean的实例化for (String beanName : beanNames){getBean(beanName);}

CircularRelyOnBeanB circularRelyOnBeanB = null

AbstractAutowireCapableBeanFactory

CircularRelyOnBeanA 内存空间

此时 circularRelyOnBeanB 还没有依赖注入；但是的了引用指向这个对象

会触发类中属性上带有@Autowired 注解的getBean操作 CircularRelyOnBeanB的实例化

getBean(beanName);

AbstractBeanFactory#doGetBean

DefaultListableBeanFactory#preInstantiateSingletons

流程主干线

口述Spring单例实例循环依赖的流程

// 根据beanName从一级缓存中拿实例Object sharedInstance = getSingleton(beanName);第一次实例化缓存中肯定不存在，获取的值为NULL。如果是单例的。

下面的流程先不要看了没梳理玩很深，先得到一个结论就行