InstantiationAwareBeanPostProcessor未生效

BeanPostProcessor及子类介绍

/**
 * Factory hook that allows for custom modification of new bean instances,
 * e.g. checking for marker interfaces or wrapping them with proxies.
 *
 * <p>ApplicationContexts can autodetect BeanPostProcessor beans in their
 * bean definitions and apply them to any beans subsequently created.
 * Plain bean factories allow for programmatic registration of post-processors,
 * applying to all beans created through this factory.
 *
 * <p>Typically, post-processors that populate beans via marker interfaces
 * or the like will implement {@link #postProcessBeforeInitialization},
 * while post-processors that wrap beans with proxies will normally
 * implement {@link #postProcessAfterInitialization}.
 *
 * @author Juergen Hoeller
 * @since 10.10.2003
 * @see InstantiationAwareBeanPostProcessor
 * @see DestructionAwareBeanPostProcessor
 * @see ConfigurableBeanFactory#addBeanPostProcessor
 * @see BeanFactoryPostProcessor
 */
public interface BeanPostProcessor {

	/**
	 * Apply this BeanPostProcessor to the given new bean instance <i>before</i> any bean
	 * initialization callbacks (like InitializingBean's {@code afterPropertiesSet}
	 * or a custom init-method). The bean will already be populated with property values.
	 * The returned bean instance may be a wrapper around the original.
	 * @param bean the new bean instance
	 * @param beanName the name of the bean
	 * @return the bean instance to use, either the original or a wrapped one;
	 * if {@code null}, no subsequent BeanPostProcessors will be invoked
	 * @throws org.springframework.beans.BeansException in case of errors
	 * @see org.springframework.beans.factory.InitializingBean#afterPropertiesSet
	 */
	Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException;

	/**
	 * Apply this BeanPostProcessor to the given new bean instance <i>after</i> any bean
	 * initialization callbacks (like InitializingBean's {@code afterPropertiesSet}
	 * or a custom init-method). The bean will already be populated with property values.
	 * The returned bean instance may be a wrapper around the original.
	 * <p>In case of a FactoryBean, this callback will be invoked for both the FactoryBean
	 * instance and the objects created by the FactoryBean (as of Spring 2.0). The
	 * post-processor can decide whether to apply to either the FactoryBean or created
	 * objects or both through corresponding {@code bean instanceof FactoryBean} checks.
	 * <p>This callback will also be invoked after a short-circuiting triggered by a
	 * {@link InstantiationAwareBeanPostProcessor#postProcessBeforeInstantiation} method,
	 * in contrast to all other BeanPostProcessor callbacks.
	 * @param bean the new bean instance
	 * @param beanName the name of the bean
	 * @return the bean instance to use, either the original or a wrapped one;
	 * if {@code null}, no subsequent BeanPostProcessors will be invoked
	 * @throws org.springframework.beans.BeansException in case of errors
	 * @see org.springframework.beans.factory.InitializingBean#afterPropertiesSet
	 * @see org.springframework.beans.factory.FactoryBean
	 */
	Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException;

}

BeanPostProcssor是Spring提供的工厂钩子方法，用于拦截每一个Bean对象的创建过程，接口有两个方法，Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException;和Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException;，分别在Bean对象创建后初始化方法（比如init-method、InitializingBean#afterPropertiesSet）调用前后进行调用，此时Bean的属性值已经被设置好了。容器可以自动发现BeanPostProcessor，我们只需要将其放入容器即可。他有一些提供更强功能的子类接口：

• InstantiationAwareBeanPostProcessor
• SmartInstantiationAwareBeanPostProcessor
• MergedBeanDefinitionPostProcessor
• DestructionAwareBeanPostProcessor

/**
 * Subinterface of {@link BeanPostProcessor} that adds a before-instantiation callback,
 * and a callback after instantiation but before explicit properties are set or
 * autowiring occurs.
 *
 * <p>Typically used to suppress default instantiation for specific target beans,
 * for example to create proxies with special TargetSources (pooling targets,
 * lazily initializing targets, etc), or to implement additional injection strategies
 * such as field injection.
 *
 * <p><b>NOTE:</b> This interface is a special purpose interface, mainly for
 * internal use within the framework. It is recommended to implement the plain
 * {@link BeanPostProcessor} interface as far as possible, or to derive from
 * {@link InstantiationAwareBeanPostProcessorAdapter} in order to be shielded
 * from extensions to this interface.
 *
 * @author Juergen Hoeller
 * @author Rod Johnson
 * @since 1.2
 * @see org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator#setCustomTargetSourceCreators
 * @see org.springframework.aop.framework.autoproxy.target.LazyInitTargetSourceCreator
 */
public interface InstantiationAwareBeanPostProcessor extends BeanPostProcessor {

	/**
	 * Apply this BeanPostProcessor <i>before the target bean gets instantiated</i>.
	 * The returned bean object may be a proxy to use instead of the target bean,
	 * effectively suppressing default instantiation of the target bean.
	 * <p>If a non-null object is returned by this method, the bean creation process
	 * will be short-circuited. The only further processing applied is the
	 * {@link #postProcessAfterInitialization} callback from the configured
	 * {@link BeanPostProcessor BeanPostProcessors}.
	 * <p>This callback will only be applied to bean definitions with a bean class.
	 * In particular, it will not be applied to beans with a "factory-method".
	 * <p>Post-processors may implement the extended
	 * {@link SmartInstantiationAwareBeanPostProcessor} interface in order
	 * to predict the type of the bean object that they are going to return here.
	 * @param beanClass the class of the bean to be instantiated
	 * @param beanName the name of the bean
	 * @return the bean object to expose instead of a default instance of the target bean,
	 * or {@code null} to proceed with default instantiation
	 * @throws org.springframework.beans.BeansException in case of errors
	 * @see org.springframework.beans.factory.support.AbstractBeanDefinition#hasBeanClass
	 * @see org.springframework.beans.factory.support.AbstractBeanDefinition#getFactoryMethodName
	 */
	Object postProcessBeforeInstantiation(Class<?> beanClass, String beanName) throws BeansException;

	/**
	 * Perform operations after the bean has been instantiated, via a constructor or factory method,
	 * but before Spring property population (from explicit properties or autowiring) occurs.
	 * <p>This is the ideal callback for performing custom field injection on the given bean
	 * instance, right before Spring's autowiring kicks in.
	 * @param bean the bean instance created, with properties not having been set yet
	 * @param beanName the name of the bean
	 * @return {@code true} if properties should be set on the bean; {@code false}
	 * if property population should be skipped. Normal implementations should return {@code true}.
	 * Returning {@code false} will also prevent any subsequent InstantiationAwareBeanPostProcessor
	 * instances being invoked on this bean instance.
	 * @throws org.springframework.beans.BeansException in case of errors
	 */
	boolean postProcessAfterInstantiation(Object bean, String beanName) throws BeansException;

	/**
	 * Post-process the given property values before the factory applies them
	 * to the given bean. Allows for checking whether all dependencies have been
	 * satisfied, for example based on a "Required" annotation on bean property setters.
	 * <p>Also allows for replacing the property values to apply, typically through
	 * creating a new MutablePropertyValues instance based on the original PropertyValues,
	 * adding or removing specific values.
	 * @param pvs the property values that the factory is about to apply (never {@code null})
	 * @param pds the relevant property descriptors for the target bean (with ignored
	 * dependency types - which the factory handles specifically - already filtered out)
	 * @param bean the bean instance created, but whose properties have not yet been set
	 * @param beanName the name of the bean
	 * @return the actual property values to apply to the given bean
	 * (can be the passed-in PropertyValues instance), or {@code null}
	 * to skip property population
	 * @throws org.springframework.beans.BeansException in case of errors
	 * @see org.springframework.beans.MutablePropertyValues
	 */
	PropertyValues postProcessPropertyValues(
			PropertyValues pvs, PropertyDescriptor[] pds, Object bean, String beanName) throws BeansException;

}

InstantiationAwareBeanPostProcessor接口增加了Bean实例化之前的回调方法Object postProcessBeforeInstantiation(Class<?> beanClass, String beanName) throws BeansException;和实例化之后但是属性值或者自动装配之前的回调方法boolean postProcessAfterInstantiation(Object bean, String beanName) throws BeansException;，以及PropertyValues postProcessPropertyValues(PropertyValues pvs, PropertyDescriptor[] pds, Object bean, String beanName) throws BeansException;。
此类最典型的应用通常用于拦截特定目标bean的默认实例化，例如，创建特定TargetSources（pooling targets, lazily initializing targets, etc）的代理，或实施额外的注入策略比如按照Field注入。此接口主要用于框架自己，不建议程序猿使用。类似的其子类SmartInstantiationAwareBeanPostProcessor提供了以下三个方法供框架使用。

/**
 * Extension of the {@link InstantiationAwareBeanPostProcessor} interface,
 * adding a callback for predicting the eventual type of a processed bean.
 *
 * <p><b>NOTE:</b> This interface is a special purpose interface, mainly for
 * internal use within the framework. In general, application-provided
 * post-processors should simply implement the plain {@link BeanPostProcessor}
 * interface or derive from the {@link InstantiationAwareBeanPostProcessorAdapter}
 * class. New methods might be added to this interface even in point releases.
 *
 * @author Juergen Hoeller
 * @since 2.0.3
 * @see InstantiationAwareBeanPostProcessorAdapter
 */
public interface SmartInstantiationAwareBeanPostProcessor extends InstantiationAwareBeanPostProcessor {

	/**
	 * Predict the type of the bean to be eventually returned from this
	 * processor's {@link #postProcessBeforeInstantiation} callback.
	 * @param beanClass the raw class of the bean
	 * @param beanName the name of the bean
	 * @return the type of the bean, or {@code null} if not predictable
	 * @throws org.springframework.beans.BeansException in case of errors
	 */
	Class<?> predictBeanType(Class<?> beanClass, String beanName) throws BeansException;

	/**
	 * Determine the candidate constructors to use for the given bean.
	 * @param beanClass the raw class of the bean (never {@code null})
	 * @param beanName the name of the bean
	 * @return the candidate constructors, or {@code null} if none specified
	 * @throws org.springframework.beans.BeansException in case of errors
	 */
	Constructor<?>[] determineCandidateConstructors(Class<?> beanClass, String beanName) throws BeansException;

	/**
	 * Obtain a reference for early access to the specified bean,
	 * typically for the purpose of resolving a circular reference.
	 * <p>This callback gives post-processors a chance to expose a wrapper
	 * early - that is, before the target bean instance is fully initialized.
	 * The exposed object should be equivalent to the what
	 * {@link #postProcessBeforeInitialization} / {@link #postProcessAfterInitialization}
	 * would expose otherwise. Note that the object returned by this method will
	 * be used as bean reference unless the post-processor returns a different
	 * wrapper from said post-process callbacks. In other words: Those post-process
	 * callbacks may either eventually expose the same reference or alternatively
	 * return the raw bean instance from those subsequent callbacks (if the wrapper
	 * for the affected bean has been built for a call to this method already,
	 * it will be exposes as final bean reference by default).
	 * @param bean the raw bean instance
	 * @param beanName the name of the bean
	 * @return the object to expose as bean reference
	 * (typically with the passed-in bean instance as default)
	 * @throws org.springframework.beans.BeansException in case of errors
	 */
	Object getEarlyBeanReference(Object bean, String beanName) throws BeansException;

}

/**
 * Post-processor callback interface for <i>merged</i> bean definitions at runtime.
 * {@link BeanPostProcessor} implementations may implement this sub-interface in order
 * to post-process the merged bean definition (a processed copy of the original bean
 * definition) that the Spring {@code BeanFactory} uses to create a bean instance.
 *
 * <p>The {@link #postProcessMergedBeanDefinition} method may for example introspect
 * the bean definition in order to prepare some cached metadata before post-processing
 * actual instances of a bean. It is also allowed to modify the bean definition but
 * <i>only</i> for definition properties which are actually intended for concurrent
 * modification. Essentially, this only applies to operations defined on the
 * {@link RootBeanDefinition} itself but not to the properties of its base classes.
 *
 * @author Juergen Hoeller
 * @since 2.5
 * @see org.springframework.beans.factory.config.ConfigurableBeanFactory#getMergedBeanDefinition
 */
public interface MergedBeanDefinitionPostProcessor extends BeanPostProcessor {

	/**
	 * Post-process the given merged bean definition for the specified bean.
	 * @param beanDefinition the merged bean definition for the bean
	 * @param beanType the actual type of the managed bean instance
	 * @param beanName the name of the bean
	 */
	void postProcessMergedBeanDefinition(RootBeanDefinition beanDefinition, Class<?> beanType, String beanName);

}

MergedBeanDefinitionPostProcessor提供了运行时处理merged bean definitions的能力。这三个类的典型实现是RequiredAnnotationBeanPostProcessor和AutowiredAnnotationBeanPostProcessor，用于处理@Requied和@Autowired、@Value注解。

/**
 * Subinterface of {@link BeanPostProcessor} that adds a before-destruction callback.
 *
 * <p>The typical usage will be to invoke custom destruction callbacks on
 * specific bean types, matching corresponding initialization callbacks.
 *
 * @author Juergen Hoeller
 * @since 1.0.1
 */
public interface DestructionAwareBeanPostProcessor extends BeanPostProcessor {

	/**
	 * Apply this BeanPostProcessor to the given bean instance before
	 * its destruction. Can invoke custom destruction callbacks.
	 * <p>Like DisposableBean's {@code destroy} and a custom destroy method,
	 * this callback just applies to singleton beans in the factory (including
	 * inner beans).
	 * @param bean the bean instance to be destroyed
	 * @param beanName the name of the bean
	 * @throws org.springframework.beans.BeansException in case of errors
	 * @see org.springframework.beans.factory.DisposableBean
	 * @see org.springframework.beans.factory.support.AbstractBeanDefinition#setDestroyMethodName
	 */
	void postProcessBeforeDestruction(Object bean, String beanName) throws BeansException;

	/**
	 * Determine whether the given bean instance requires destruction by this
	 * post-processor.
	 * <p><b>NOTE:</b> Even as a late addition, this method has been introduced on
	 * {@code DestructionAwareBeanPostProcessor} itself instead of on a SmartDABPP
	 * subinterface. This allows existing {@code DestructionAwareBeanPostProcessor}
	 * implementations to easily provide {@code requiresDestruction} logic while
	 * retaining compatibility with Spring <4.3, and it is also an easier onramp to
	 * declaring {@code requiresDestruction} as a Java 8 default method in Spring 5.
	 * <p>If an implementation of {@code DestructionAwareBeanPostProcessor} does
	 * not provide a concrete implementation of this method, Spring's invocation
	 * mechanism silently assumes a method returning {@code true} (the effective
	 * default before 4.3, and the to-be-default in the Java 8 method in Spring 5).
	 * @param bean the bean instance to check
	 * @return {@code true} if {@link #postProcessBeforeDestruction} is supposed to
	 * be called for this bean instance eventually, or {@code false} if not needed
	 * @since 4.3
	 */
	boolean requiresDestruction(Object bean);

}

DestructionAwareBeanPostProcessor 提供了Bean销毁之前的回调方法void postProcessBeforeDestruction(Object bean, String beanName) throws BeansException; 其典型实现有ApplicationListenerDetector用于处理ApplicationListener的添加和销毁、InitDestroyAnnotationBeanPostProcessor用于处理@PostConstruct和@PreDestroy、ScheduledAnnotationBeanPostProcessor用于处理@Scheduled注解。

注册时机

BeanPostProcessor的运行机制是先注册，后使用。注册是在AbstractApplicationContext#refresh方法中。使用就是在Bean对象的初始化前后进行使用。

registerBeanPostProcessors方法委托给PostProcessorRegistrationDelegate#registerBeanPostProcessors(ConfigurableListableBeanFactory,AbstractApplicationContext)。

public static void registerBeanPostProcessors(
			ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {

		String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);

		// Register BeanPostProcessorChecker that logs an info message when
		// a bean is created during BeanPostProcessor instantiation, i.e. when
		// a bean is not eligible for getting processed by all BeanPostProcessors.
		int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
		beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));

		// Separate between BeanPostProcessors that implement PriorityOrdered,
		// Ordered, and the rest.
		List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<BeanPostProcessor>();
		List<BeanPostProcessor> internalPostProcessors = new ArrayList<BeanPostProcessor>();
		List<String> orderedPostProcessorNames = new ArrayList<String>();
		List<String> nonOrderedPostProcessorNames = new ArrayList<String>();
		for (String ppName : postProcessorNames) {
			if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
				BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
				priorityOrderedPostProcessors.add(pp);
				if (pp instanceof MergedBeanDefinitionPostProcessor) {
					internalPostProcessors.add(pp);
				}
			}
			else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
				orderedPostProcessorNames.add(ppName);
			}
			else {
				nonOrderedPostProcessorNames.add(ppName);
			}
		}

		// First, register the BeanPostProcessors that implement PriorityOrdered.
		sortPostProcessors(beanFactory, priorityOrderedPostProcessors);
		registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);

		// Next, register the BeanPostProcessors that implement Ordered.
		List<BeanPostProcessor> orderedPostProcessors = new ArrayList<BeanPostProcessor>();
		for (String ppName : orderedPostProcessorNames) {
			BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
			orderedPostProcessors.add(pp);
			if (pp instanceof MergedBeanDefinitionPostProcessor) {
				internalPostProcessors.add(pp);
			}
		}
		sortPostProcessors(beanFactory, orderedPostProcessors);
		registerBeanPostProcessors(beanFactory, orderedPostProcessors);

		// Now, register all regular BeanPostProcessors.
		List<BeanPostProcessor> nonOrderedPostProcessors = new ArrayList<BeanPostProcessor>();
		for (String ppName : nonOrderedPostProcessorNames) {
			BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
			nonOrderedPostProcessors.add(pp);
			if (pp instanceof MergedBeanDefinitionPostProcessor) {
				internalPostProcessors.add(pp);
			}
		}
		registerBeanPostProcessors(beanFactory, nonOrderedPostProcessors);

		// Finally, re-register all internal BeanPostProcessors.
		sortPostProcessors(beanFactory, internalPostProcessors);
		registerBeanPostProcessors(beanFactory, internalPostProcessors);

		// Re-register post-processor for detecting inner beans as ApplicationListeners,
		// moving it to the end of the processor chain (for picking up proxies etc).
		beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
	}

按照实现了以下接口PriorityOrdered、Ordered和无顺序接口分别进行注册，其中实现了MergedBeanDefinitionPostProcessor接口的还额外添加了一次。最后添加了一个ApplicationListenerDetector，用于获取容器中的ApplicationListener进行注册。添加方法使用BeanFactory#addBeanPostProcessor(BeanPostProcessor beanPostProcessor);。此时容器中已经保存的是BeanPostProcessor的实例，因为已经调用BeanFactory#getBean方法。关于MergedBeanDefinitionPostProcessor接口，虽然通过internalPostProcessors重新添加了一次，但是并不会重复添加，因为addBeanPostProcessor方法是先remove，再add，这些BeanPostProcessor就会添加到最后。

@Override
	public void addBeanPostProcessor(BeanPostProcessor beanPostProcessor) {
		Assert.notNull(beanPostProcessor, "BeanPostProcessor must not be null");
		this.beanPostProcessors.remove(beanPostProcessor);
		this.beanPostProcessors.add(beanPostProcessor);
		if (beanPostProcessor instanceof InstantiationAwareBeanPostProcessor) {
			this.hasInstantiationAwareBeanPostProcessors = true;
		}
		if (beanPostProcessor instanceof DestructionAwareBeanPostProcessor) {
			this.hasDestructionAwareBeanPostProcessors = true;
		}
	}

介入时机

经过以上的步骤，此时容器中已经包含了所有的BeanPostProcessor ，在其他Bean创建的时候，这些BeanPostProcessor 就会介入工作。

在AbstractAutowireCapableBeanFactory#createBean方法中，首先给InstantiationAwareBeanPostProcessor一个机会创建对象的代理。

protected Object resolveBeforeInstantiation(String beanName, RootBeanDefinition mbd) {
		Object bean = null;
		if (!Boolean.FALSE.equals(mbd.beforeInstantiationResolved)) {
			// Make sure bean class is actually resolved at this point.
			if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
				Class<?> targetType = determineTargetType(beanName, mbd);
				if (targetType != null) {
					bean = applyBeanPostProcessorsBeforeInstantiation(targetType, beanName);
					if (bean != null) {
						bean = applyBeanPostProcessorsAfterInitialization(bean, beanName);
					}
				}
			}
			mbd.beforeInstantiationResolved = (bean != null);
		}
		return bean;
	}

	protected Object applyBeanPostProcessorsBeforeInstantiation(Class<?> beanClass, String beanName) {
		for (BeanPostProcessor bp : getBeanPostProcessors()) {
			if (bp instanceof InstantiationAwareBeanPostProcessor) {
				InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
				Object result = ibp.postProcessBeforeInstantiation(beanClass, beanName);
				if (result != null) {
					return result;
				}
			}
		}
		return null;
	}
	@Override
	public Object applyBeanPostProcessorsAfterInitialization(Object existingBean, String beanName)
			throws BeansException {

		Object result = existingBean;
		for (BeanPostProcessor beanProcessor : getBeanPostProcessors()) {
			result = beanProcessor.postProcessAfterInitialization(result, beanName);
			if (result == null) {
				return result;
			}
		}
		return result;
	}

首先调用InstantiationAwareBeanPostProcessor#postProcessBeforeInstantiation创建对象，不为空则直接返回，所以，最多只有一个InstantiationAwareBeanPostProcessor会起作用。然后调用所有的BeanPostProcessor的postProcessAfterInitialization方法。

如果以上方法返回null，则说明需要走Bean创建流程，就调用AbstractAutowireCapableBeanFactory#doCreateBean方法。

protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final 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);
		}
		final Object bean = (instanceWrapper != null ? instanceWrapper.getWrappedInstance() : null);
		Class<?> beanType = (instanceWrapper != null ? instanceWrapper.getWrappedClass() : null);
		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.postProcessed = true;
			}
		}

		// 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.isDebugEnabled()) {
				logger.debug("Eagerly caching bean '" + beanName +
						"' to allow for resolving potential circular references");
			}
			addSingletonFactory(beanName, new ObjectFactory<Object>() {
				@Override
				public Object getObject() throws BeansException {
					return getEarlyBeanReference(beanName, mbd, bean);
				}
			});
		}

		// Initialize the bean instance.
		Object exposedObject = bean;
		try {
			populateBean(beanName, mbd, instanceWrapper);
			if (exposedObject != null) {
				exposedObject = initializeBean(beanName, exposedObject, mbd);
			}
		}
		catch (Throwable ex) {
			if (ex instanceof BeanCreationException && beanName.equals(((BeanCreationException) ex).getBeanName())) {
				throw (BeanCreationException) ex;
			}
			else {
				throw new BeanCreationException(
						mbd.getResourceDescription(), beanName, "Initialization of bean failed", 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<String>(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 " +
								"'getBeanNamesOfType' 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;
	}

创建BeanWrapper（这个类是对Bean实例的一次封装）之后。应用MergedBeanDefinitionPostProcessor#postProcessMergedBeanDefinition再给一次机会修改BeanDefinition。

protected void applyMergedBeanDefinitionPostProcessors(RootBeanDefinition mbd, Class<?> beanType, String beanName) {
		for (BeanPostProcessor bp : getBeanPostProcessors()) {
			if (bp instanceof MergedBeanDefinitionPostProcessor) {
				MergedBeanDefinitionPostProcessor bdp = (MergedBeanDefinitionPostProcessor) bp;
				bdp.postProcessMergedBeanDefinition(mbd, beanType, beanName);
			}
		}
	}

populateBean(beanName, mbd, instanceWrapper);对Bean进行属性赋值，这个方法中如果有InstantiationAwareBeanPostProcessor，会调用postProcessAfterInstantiation方法和postProcessPropertyValues方法。
之后进行对象的初始化，首先如果Bean实现了BeanNameAware、BeanClassLoaderAware、BeanFactoryAware，则分别注入这些，然后在初始化方法调用前后应用BeanPostProcessor#postProcessBeforeInitialization、BeanPostProcessor#postProcessAfterInitialization

protected Object initializeBean(final String beanName, final Object bean, RootBeanDefinition mbd) {
		if (System.getSecurityManager() != null) {
			AccessController.doPrivileged(new PrivilegedAction<Object>() {
				@Override
				public Object run() {
					invokeAwareMethods(beanName, bean);
					return null;
				}
			}, getAccessControlContext());
		}
		else {
			invokeAwareMethods(beanName, bean);
		}

		Object wrappedBean = bean;
		if (mbd == null || !mbd.isSynthetic()) {
			wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
		}

		try {
			invokeInitMethods(beanName, wrappedBean, mbd);
		}
		catch (Throwable ex) {
			throw new BeanCreationException(
					(mbd != null ? mbd.getResourceDescription() : null),
					beanName, "Invocation of init method failed", ex);
		}

		if (mbd == null || !mbd.isSynthetic()) {
			wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);
		}
		return wrappedBean;
	}

@Override
	public Object applyBeanPostProcessorsBeforeInitialization(Object existingBean, String beanName)
			throws BeansException {

		Object result = existingBean;
		for (BeanPostProcessor beanProcessor : getBeanPostProcessors()) {
			result = beanProcessor.postProcessBeforeInitialization(result, beanName);
			if (result == null) {
				return result;
			}
		}
		return result;
	}

	@Override
	public Object applyBeanPostProcessorsAfterInitialization(Object existingBean, String beanName)
			throws BeansException {

		Object result = existingBean;
		for (BeanPostProcessor beanProcessor : getBeanPostProcessors()) {
			result = beanProcessor.postProcessAfterInitialization(result, beanName);
			if (result == null) {
				return result;
			}
		}
		return result;
	}