【Spring 源码】 贯穿 Bean 生命周期的核心类之 AbstractAutowireCapableBeanFactory

  protected Object doCreateBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args)
      throws BeanCreationException {
    // Instantiate the bean.
    BeanWrapper instanceWrapper = null;
    if (mbd.isSingleton()) {
      instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);
    }
    if (instanceWrapper == null) {
      instanceWrapper = createBeanInstance(beanName, mbd, args);
    }
    Object bean = instanceWrapper.getWrappedInstance();
    Class<?> beanType = instanceWrapper.getWrappedClass();
    if (beanType != NullBean.class) {
      mbd.resolvedTargetType = beanType;
    }
    // Allow post-processors to modify the merged bean definition.
    synchronized (mbd.postProcessingLock) {
      if (!mbd.postProcessed) {
        try {
          applyMergedBeanDefinitionPostProcessors(mbd, beanType, beanName);
        }
        catch (Throwable ex) {
          throw new BeanCreationException(mbd.getResourceDescription(), beanName,
              "Post-processing of merged bean definition failed", ex);
        }
        mbd.markAsPostProcessed();
      }
    }
    // Eagerly cache singletons to be able to resolve circular references
    // even when triggered by lifecycle interfaces like BeanFactoryAware.
    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");
      }
      addSingletonFactory(beanName, () -> getEarlyBeanReference(beanName, mbd, bean));
    }
    // Initialize the bean instance.
    Object exposedObject = bean;
    try {
      populateBean(beanName, mbd, instanceWrapper);
      exposedObject = initializeBean(beanName, exposedObject, mbd);
    }
    catch (Throwable ex) {
      if (ex instanceof BeanCreationException bce && beanName.equals(bce.getBeanName())) {
        throw bce;
      }
      else {
        throw new BeanCreationException(mbd.getResourceDescription(), beanName, ex.getMessage(), ex);
      }
    }
    if (earlySingletonExposure) {
      Object earlySingletonReference = getSingleton(beanName, false);
      if (earlySingletonReference != null) {
        if (exposedObject == bean) {
          exposedObject = earlySingletonReference;
        }
        else if (!this.allowRawInjectionDespiteWrapping && hasDependentBean(beanName)) {
          String[] dependentBeans = getDependentBeans(beanName);
          Set<String> actualDependentBeans = new LinkedHashSet<>(dependentBeans.length);
          for (String dependentBean : dependentBeans) {
            if (!removeSingletonIfCreatedForTypeCheckOnly(dependentBean)) {
              actualDependentBeans.add(dependentBean);
            }
          }
          if (!actualDependentBeans.isEmpty()) {
            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 " +
                "'getBeanNamesForType' with the 'allowEagerInit' flag turned off, for example.");
          }
        }
      }
    }
    // Register bean as disposable.
    try {
      registerDisposableBeanIfNecessary(beanName, bean, mbd);
    }
    catch (BeanDefinitionValidationException ex) {
      throw new BeanCreationException(
          mbd.getResourceDescription(), beanName, "Invalid destruction signature", ex);
    }
    return exposedObject;
  }

BeanWrapper instanceWrapper = null;
if (mbd.isSingleton()) {
    instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);
}
if (instanceWrapper == null) {
    instanceWrapper = createBeanInstance(beanName, mbd, args);
}

populateBean(beanName, mbd, instanceWrapper);

exposedObject = initializeBean(beanName, exposedObject, mbd);

Object earlySingletonReference = getSingleton(beanName, false);
if (earlySingletonReference != null) {
    // 处理代理，获取早期半成品对象
    exposedObject = earlySingletonReference;
}