[Java知识库]Spring的BeanFactoryPostProcessor和BeanPostProcessor

BeanFactoryPostProcessor和BeanPostProcessor，这两个接口，都是Spring初始化bean时对外暴露的扩展点。两个接口名称看起来很相似，但作用及使用场景却不同.

BeanFactoryPostProcessor和BeanPostProcessor都是后置增强器。还有一个是BeanDefinitionRegistryPostProcessor
BeanPostProcessor是Bean的后置增强
BeanFactoryPostProcessor和BeanDefinationRegistryPostProcessor是Bean工厂的后置增强
InitializingBean: 是Bean初始化以后对组件进行后序设置。
BeanPostProcessor和BeanFactoryPostProcessor在于改变,而InitializingBean在于后序设置, 额外处理。

1.BeanFactoryPostProcessor接口

public interface BeanFactoryPostProcessor {
 
	/**
	 * Modify the application context's internal bean factory after its standard
	 * initialization. All bean definitions will have been loaded, but no beans
	 * will have been instantiated yet. This allows for overriding or adding
	 * properties even to eager-initializing beans.
	 * @param beanFactory the bean factory used by the application context
	 * @throws org.springframework.beans.BeansException in case of errors
	 */
	void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException;
 
}

实现该接口，可以在spring的bean创建之前，修改bean的定义属性。

Spring允许BeanFactoryPostProcessor在容器实例化任何其它bean之前读取配置元数据，并可以根据需要进行修改，例如可以把bean的scope从singleton改为prototype，也可以把property的值给修改掉。可以同时配置多个BeanFactoryPostProcessor，并通过设置’order’属性来控制各个BeanFactoryPostProcessor的执行次序。

BeanFactoryPostProcessor是在spring容器加载了bean的定义文件之后，在bean实例化之前执行的。接口方法的入参是ConfigurrableListableBeanFactory，使用该参数，可以获取到相关bean的定义信息

自定义的BeanFactoryPostProcessor:

public class MyBeanFactoryPostProcessor implements BeanFactoryPostProcessor {
 
    public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
        System.out.println("调用MyBeanFactoryPostProcessor的postProcessBeanFactory");
        BeanDefinition bd = beanFactory.getBeanDefinition("myJavaBean");
        System.out.println("属性值============" + bd.getPropertyValues().toString());
        MutablePropertyValues pv =  bd.getPropertyValues();  
        if (pv.contains("remark")) {  
            pv.addPropertyValue("remark", "把备注信息修改一下");  
        }  
        bd.setScope(BeanDefinition.SCOPE_PROTOTYPE);
    }
 
}

spring中，有内置的一些BeanFactoryPostProcessor实现类，常用的有：

• org.springframework.beans.factory.config.PropertyPlaceholderConfigurer
• org.springframework.beans.factory.config.PropertyOverrideConfigurer
• org.springframework.beans.factory.config.CustomEditorConfigurer：用来注册自定义的属性编辑器

2.BeanPostProcessor接口

public interface BeanPostProcessor {
 
	/**
	 * Apply this BeanPostProcessor to the given new bean instance <i>before</i> any bean
	 * initialization callbacks (like InitializingBean's <code>afterPropertiesSet</code>
	 * 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
	 * @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</code>
	 * 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</code> 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
	 * @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;
 
}

BeanPostProcessor，可以在spring容器实例化bean之后，在执行bean的初始化方法前后，添加一些自己的处理逻辑。这里说的初始化方法，指的是下面两种：

• bean实现了InitializingBean接口，对应的方法为afterPropertiesSet
• 在bean定义的时候，通过init-method设置的方法

BeanPostProcessor是在spring容器加载了bean的定义文件并且实例化bean之后执行的。BeanPostProcessor的执行顺序是在BeanFactoryPostProcessor之后。

spring中，有内置的一些BeanPostProcessor实现类，例如：

• org.springframework.context.annotation.CommonAnnotationBeanPostProcessor：支持@Resource注解的注入
• org.springframework.beans.factory.annotation.RequiredAnnotationBeanPostProcessor：支持@Required注解的注入
• org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor：支持@Autowired注解的注入
• org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor：支持@PersistenceUnit和@PersistenceContext注解的注入
• org.springframework.context.support.ApplicationContextAwareProcessor：用来为bean注入ApplicationContext等容器对象

3.实例

public class MyJavaBean implements InitializingBean {
    private String desc;
    private String remark;
    
    public MyJavaBean() {
        System.out.println("MyJavaBean的构造函数被执行啦");
    }
    public String getDesc() {
        return desc;
    }
    public void setDesc(String desc) {
        System.out.println("调用setDesc方法");
        this.desc = desc;
    }
    public String getRemark() {
        return remark;
    }
    public void setRemark(String remark) {
        System.out.println("调用setRemark方法");
        this.remark = remark;
    }
    public void afterPropertiesSet() throws Exception {
        System.out.println("调用afterPropertiesSet方法");
        this.desc = "在初始化方法中修改之后的描述信息";
    }
    public void initMethod() {
        System.out.println("调用initMethod方法");
    }
    public String toString() {
        StringBuilder builder = new StringBuilder();
        builder.append("[描述：").append(desc);
        builder.append("， 备注：").append(remark).append("]");
        return builder.toString();
    }
}

public class MyBeanDefinitionRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor {
    @Override
    public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
        System.out.println("MyBeanDefinitionRegistryPostProcessor");
    }

    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
        System.out.println("MyBeanDefinitionRegistryPostProcessor...");
    }
}

public class MyBeanPostProcessor implements BeanPostProcessor {
 
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        System.out.println("BeanPostProcessor，对象" + beanName + "调用初始化方法之前的数据： " + bean.toString());
        return bean;
    }
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        System.out.println("BeanPostProcessor，对象" + beanName + "调用初始化方法之后的数据：" + bean.toString());
        return bean;
    }
}

public class MyBeanFactoryPostProcessor implements BeanFactoryPostProcessor {
    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
        System.out.println("调用MyBeanFactoryPostProcessor的postProcessBeanFactory");
        BeanDefinition bd = beanFactory.getBeanDefinition("myJavaBean");
        MutablePropertyValues pv =  bd.getPropertyValues();
        if (pv.contains("remark")) {
            pv.addPropertyValue("remark", "在BeanFactoryPostProcessor中修改之后的备忘信息");
        }

    }
}

<?xml version="1.0" encoding="UTF-8" ?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context"
       xmlns:p="http://www.springframework.org/schema/p" xmlns:tx="http://www.springframework.org/schema/tx"
       xmlns:aop="http://www.springframework.org/schema/aop"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
				http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-2.5.xsd
				http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.5.xsd"
       default-autowire="byName">

    <bean id="myJavaBean" class="com.atguigu.bean.MyJavaBean" init-method="initMethod">
        <property name="desc" value="原始的描述信息" />
        <property name="remark" value="原始的备注信息" />
    </bean>

    <bean id="myBeanPostProcessor" class="com.atguigu.postprocessor.MyBeanPostProcessor" />
    <bean id="myBeanFactoryPostProcessor" class="com.atguigu.postprocessor.MyBeanFactoryPostProcessor" />
</beans>

public class PostProcessorMain {
    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("bean2.xml");
        MyJavaBean bean = (MyJavaBean) context.getBean("myJavaBean");
        System.out.println("===============下面输出结果============");
        System.out.println("描述：" + bean.getDesc());
        System.out.println("备注：" + bean.getRemark());
 
    }
}

-> BeanDefinitionRegistryPostProcessor .postProcessorBeanDefinitionRefistry
->BeanDefinitionRegistryPostProcessor. postProcessBeanFactory
-> BeanFactoryPostProcessor.postProcessorBeanFactory方法
-> BeanPostProcessor.postProcessBeforeInitialization： 前置方法
-> IniitializingBean. afterProperties
-> invoke-meethod
-> beanPostProcessor.postProcessAfterInitialization： 后置方法

4.分析

invokeBeanFactoryPostProcessors() 执行工厂的后置增强 -> ConfigurationClassPostProcessor 解析配置类的后置处理器
-> postProcessorRegistrationDelegate 管理所有的后置处理器的执行,

在使用ApplicationContext启动spring容器的时候，在AbstractApplicationContext.refresh()方法中，完成相关初始化工作：

1. BeanDefinitionRegistryPostProcessor

2. BeanFactoryPostProcessor.postProcessBeanFactory -> invokeBeanFactoryPostProcessors

/**
	 * Instantiate and invoke all registered BeanFactoryPostProcessor beans,
	 * respecting explicit order if given.
	 * <p>Must be called before singleton instantiation.
	 */
	protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
		// Invoke factory processors registered with the context instance.
		for (Iterator it = getBeanFactoryPostProcessors().iterator(); it.hasNext();) {
			BeanFactoryPostProcessor factoryProcessor = (BeanFactoryPostProcessor) it.next();
			factoryProcessor.postProcessBeanFactory(beanFactory);
		}
 
		// Do not initialize FactoryBeans here: We need to leave all regular beans
		// uninitialized to let the bean factory post-processors apply to them!
		String[] postProcessorNames =
				beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);
 
		// Separate between BeanFactoryPostProcessors that implement PriorityOrdered,
		// Ordered, and the rest.
		List priorityOrderedPostProcessors = new ArrayList();
		List orderedPostProcessorNames = new ArrayList();
		List nonOrderedPostProcessorNames = new ArrayList();
		for (int i = 0; i < postProcessorNames.length; i++) {
			if (isTypeMatch(postProcessorNames[i], PriorityOrdered.class)) {
				priorityOrderedPostProcessors.add(beanFactory.getBean(postProcessorNames[i]));
			}
			else if (isTypeMatch(postProcessorNames[i], Ordered.class)) {
				orderedPostProcessorNames.add(postProcessorNames[i]);
			}
			else {
				nonOrderedPostProcessorNames.add(postProcessorNames[i]);
			}
		}
 
		// First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.
		Collections.sort(priorityOrderedPostProcessors, new OrderComparator());
		invokeBeanFactoryPostProcessors(beanFactory, priorityOrderedPostProcessors);
 
		// Next, invoke the BeanFactoryPostProcessors that implement Ordered.
		List orderedPostProcessors = new ArrayList();
		for (Iterator it = orderedPostProcessorNames.iterator(); it.hasNext();) {
			String postProcessorName = (String) it.next();
			orderedPostProcessors.add(getBean(postProcessorName));
		}
		Collections.sort(orderedPostProcessors, new OrderComparator());
		invokeBeanFactoryPostProcessors(beanFactory, orderedPostProcessors);
 
		// Finally, invoke all other BeanFactoryPostProcessors.
		List nonOrderedPostProcessors = new ArrayList();
		for (Iterator it = nonOrderedPostProcessorNames.iterator(); it.hasNext();) {
			String postProcessorName = (String) it.next();
			nonOrderedPostProcessors.add(getBean(postProcessorName));
		}
		invokeBeanFactoryPostProcessors(beanFactory, nonOrderedPostProcessors);
	}
 
	/**
	 * Invoke the given BeanFactoryPostProcessor beans.
	 */
	private void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory, List postProcessors) {
		for (Iterator it = postProcessors.iterator(); it.hasNext();) {
			BeanFactoryPostProcessor postProcessor = (BeanFactoryPostProcessor) it.next();
			postProcessor.postProcessBeanFactory(beanFactory);
		}
	}

增强工厂: 通过beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false)，获取spring配置文件中定义的所有实现BeanFactoryPostProcessor接口的bean，然后根据优先级进行排序，之后对于每个BeanFactoryPostProcessor，调用postProcessBeanFactory方法。

3. 而BeanPostProcessor的执行，取决于配置文件中bean的定义，如果定义的bean是singleton并且不是抽象类，也不延迟初始化，则BeanPostProcessor是在第11步中执行；而对于prototype的bean，BeanPostProcessor是在程序getBean的时候执行的。在第6步中，调用registerBeanPostProcessors方法，注册所有实现BeanPostProcessor接口的bean，该方法的实现如下：
   registerBeanPostProcessors用于管理Bean的后置处理器

protected void registerBeanPostProcessors(ConfigurableListableBeanFactory beanFactory) {
   	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 priorityOrderedPostProcessors = new ArrayList();
   	List orderedPostProcessorNames = new ArrayList();
   	List nonOrderedPostProcessorNames = new ArrayList();
   	for (int i = 0; i < postProcessorNames.length; i++) {
   		if (isTypeMatch(postProcessorNames[i], PriorityOrdered.class)) {
   			priorityOrderedPostProcessors.add(beanFactory.getBean(postProcessorNames[i]));
   		}
   		else if (isTypeMatch(postProcessorNames[i], Ordered.class)) {
   			orderedPostProcessorNames.add(postProcessorNames[i]);
   		}
   		else {
   			nonOrderedPostProcessorNames.add(postProcessorNames[i]);
   		}
   	}

   	// First, register the BeanPostProcessors that implement PriorityOrdered.
   	Collections.sort(priorityOrderedPostProcessors, new OrderComparator());
   	registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);

   	// Next, register the BeanPostProcessors that implement Ordered.
   	List orderedPostProcessors = new ArrayList();
   	for (Iterator it = orderedPostProcessorNames.iterator(); it.hasNext();) {
   		String postProcessorName = (String) it.next();
   		orderedPostProcessors.add(getBean(postProcessorName));
   	}
   	Collections.sort(orderedPostProcessors, new OrderComparator());
   	registerBeanPostProcessors(beanFactory, orderedPostProcessors);

   	// Finally, register all other BeanPostProcessors.
   	List nonOrderedPostProcessors = new ArrayList();
   	for (Iterator it = nonOrderedPostProcessorNames.iterator(); it.hasNext();) {
   		String postProcessorName = (String) it.next();
   		nonOrderedPostProcessors.add(getBean(postProcessorName));
   	}
   	registerBeanPostProcessors(beanFactory, nonOrderedPostProcessors);
   }

在第11步中，调用finishBeanFactoryInitialization方法，该方法通过调用DefaultListableBeanFactory.preInstantiateSingletons()，进行相关初始化工作：

从上面的代码可以看出，对于非抽象类、非延迟初始化的单例bean，在spring容器启动的时候调用getBean方法来实例化bean，并进行相关初始化工作，getBean方法最终调用AbstractAutowireCapableBeanFactory.doCreateBean方法，该方法的实现如下：

protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final Object[] args) {
		// Instantiate the bean.
		BeanWrapper instanceWrapper = null;
		if (mbd.isSingleton()) {
			instanceWrapper = (BeanWrapper) 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);
 
		// Allow post-processors to modify the merged bean definition.
		synchronized (mbd.postProcessingLock) {
			if (!mbd.postProcessed) {
				applyMergedBeanDefinitionPostProcessors(mbd, beanType, beanName);
				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() {
				public Object getObject() throws BeansException {
					return 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 && 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 actualDependentBeans = new LinkedHashSet(dependentBeans.length);
					for (int i = 0; i < dependentBeans.length; i++) {
						String dependentBean = dependentBeans[i];
						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.
		registerDisposableBeanIfNecessary(beanName, bean, mbd);
 
		return exposedObject;
	}

在该方法中，首先调用createBeanInstance方法，创建bean实例对象（这个时候执行bean的构造方法），然后调用populateBean方法，对bean进行填充，注入相关依赖，之后再调用方法initializeBean，进行相关初始化工作，initializeBean方法的实现如下：

protected Object initializeBean(String beanName, Object bean, RootBeanDefinition mbd) {
		if (bean instanceof BeanNameAware) {
			((BeanNameAware) bean).setBeanName(beanName);
		}
 
		if (bean instanceof BeanClassLoaderAware) {
			((BeanClassLoaderAware) bean).setBeanClassLoader(getBeanClassLoader());
		}
 
		if (bean instanceof BeanFactoryAware) {
			((BeanFactoryAware) bean).setBeanFactory(this);
		}
 
		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;
	}

applyBeanPostProcessorsBeforeInitialization方法: 执行每个BeanPostProcessor的postProcessBeforeInitialization，然后调用invokeInitMethods方法，执行bean的初始化方法，最后调用applyBeanPostProcessorsAfterInitialization方法，执行每个BeanPostProcessor的postProcessAfterInitialization方法。

	public Object applyBeanPostProcessorsBeforeInitialization(Object existingBean, String beanName)
			throws BeansException {
 
		Object result = existingBean;
		for (Iterator it = getBeanPostProcessors().iterator(); it.hasNext();) {
			BeanPostProcessor beanProcessor = (BeanPostProcessor) it.next();
			result = beanProcessor.postProcessBeforeInitialization(result, beanName);
		}
		return result;
	}
 
	public Object applyBeanPostProcessorsAfterInitialization(Object existingBean, String beanName)
			throws BeansException {
 
		Object result = existingBean;
		for (Iterator it = getBeanPostProcessors().iterator(); it.hasNext();) {
			BeanPostProcessor beanProcessor = (BeanPostProcessor) it.next();
			result = beanProcessor.postProcessAfterInitialization(result, beanName);
		}
		return result;
	}
protected void invokeInitMethods(String beanName, Object bean, RootBeanDefinition mbd)
			throws Throwable {
 
		boolean isInitializingBean = (bean instanceof InitializingBean);
		if (isInitializingBean && (mbd == null || !mbd.isExternallyManagedInitMethod("afterPropertiesSet"))) {
			if (logger.isDebugEnabled()) {
				logger.debug("Invoking afterPropertiesSet() on bean with name '" + beanName + "'");
			}
			((InitializingBean) bean).afterPropertiesSet();
		}
 
		String initMethodName = (mbd != null ? mbd.getInitMethodName() : null);
		if (initMethodName != null && !(isInitializingBean && "afterPropertiesSet".equals(initMethodName)) &&
				!mbd.isExternallyManagedInitMethod(initMethodName)) {
			invokeCustomInitMethod(beanName, bean, initMethodName, mbd.isEnforceInitMethod());
		}
	}

从invokeInitMethods方法的实现可以看出，先执行afterPropertiesSet方法，然后再通过反射，执行init-method指定的方法。

5.Spring 闭环操作

闭环逻辑l: 容器中有就拿没有就创建。

所有的组件都是通过getBean获取的。

6.总结

有4种增强: BeanDefinitionRegitryPostProcessor, BeanFactoryPostProcessor, BeanPostProcessor, InitalizingBean

他们的顺序为

-> BeanDefinitionRegistryPostProcessor .postProcessorBeanDefinitionRefistry
->BeanDefinitionRegistryPostProcessor. postProcessBeanFactory
-> BeanFactoryPostProcessor.postProcessorBeanFactory方法
-> BeanPostProcessor.postProcessBeforeInitialization： 前置方法
-> IniitializingBean. afterProperties
-> invoke-meethod：invokeInitMethod方法:初始化方法
-> beanPostProcessor.postProcessAfterInitialization： 后置方法