Spring Bean生命周期-registerBeanPostProcessors(七)

ApplicationContext刷新的时候上一步提到了，先调用BeanFactoryPostProcessors预处理下BeanFactory，现在注册Bean processors来拦截Bean的创建。

实例化，然后调用所有注册的BeanPostProcessor bean。如果指定了顺序，会按照顺序执行。
必须在应用Bean实例化之前调用。

protected void registerBeanPostProcessors(ConfigurableListableBeanFactory beanFactory) {
		PostProcessorRegistrationDelegate.registerBeanPostProcessors(beanFactory, this);
	}

分析

先看到还是这个工具类，在上步的BeanFactoryPostProcessors中使用的也是它。

注册BeanPostProcessor的代码如下：

	public static void registerBeanPostProcessors(
			ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {
      
      // 获取BeanFactory中注册的类型为BeanPostProcessor.class的bean名称。一般获取到的是实现了BeanPostProcessor接口的Bean
		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.
		// 注册一个BeanPostProcessorChecker，用来记录bean在BeanPostProcessor实例化时的信息。
		int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
		beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));

		// Separate between BeanPostProcessors that implement PriorityOrdered,
		// Ordered, and the rest.
		// 将BeanPostProcessors分为实现了PriorityOrdered，Ordered等类型
		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);
				// 如果BeanPostProcessors也实现了MergedBeanDefinitionPostProcessor接口，加入internalPostProcessors
				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.
		// 首先注册实现了PriorityOrdered接口的BeanPostProcessors
		sortPostProcessors(beanFactory, priorityOrderedPostProcessors);
		registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);

		// Next, register the BeanPostProcessors that implement Ordered.
		// 然后，注册实现了Ordered的BeanPostProcessors
		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.
		// 现在注册所有常规的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.
		// 最后注册，所有的internal，也就是实现MergedBeanDefinitionPostProcessor的BeanPostProcessors
		sortPostProcessors(beanFactory, internalPostProcessors);
		registerBeanPostProcessors(beanFactory, internalPostProcessors);
     
     //添加ApplicationListenerDetector的BeanPostProcessor
		beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
	}

整体代码也不难理解，如函数名，就是做了注册BeanPostProcessor

• 获取实现了BeanPostProcessor的bean Name，最开始Bean的信息注册到了beandifinitionMap中
• 将获取到的BeanPostProcessor分类，分为PriorityOrdered，Ordered和常规的类型
• 分别将PriorityOrdered，Ordered和常规的Bean添加进ApplicationContext的beanPostProcessors中，ApplicationContext的beanPostProcessors是ArrayList。

BeanFactory.getBeanNamesForType具体实现

其内部调用的是doGetBeanNamesForType

• 遍历beanDefinitionNames判断是否符合要求是否为type
• 遍历manualSingletonNames。

内部有个处理是如果Bean是FactoryBean，其名称前面加上&

private String[] doGetBeanNamesForType(ResolvableType type, boolean includeNonSingletons, boolean allowEagerInit){
    		// Check all bean definitions.
    		// 检查所有的beanDefinitionNames。
		for (String beanName : this.beanDefinitionNames) {
			// Only consider bean as eligible if the bean name
			// is not defined as alias for some other bean.
			if (!isAlias(beanName)) {
				try {
					RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
					// Only check bean definition if it is complete.
					if (!mbd.isAbstract() && (allowEagerInit ||
							((mbd.hasBeanClass() || !mbd.isLazyInit() || isAllowEagerClassLoading())) &&
									!requiresEagerInitForType(mbd.getFactoryBeanName()))) {
						// In case of FactoryBean, match object created by FactoryBean.
						boolean isFactoryBean = isFactoryBean(beanName, mbd);
						boolean matchFound = (allowEagerInit || !isFactoryBean || containsSingleton(beanName)) &&
								(includeNonSingletons || isSingleton(beanName)) && isTypeMatch(beanName, type);
						if (!matchFound && isFactoryBean) {
							// In case of FactoryBean, try to match FactoryBean instance itself next.
							beanName = FACTORY_BEAN_PREFIX + beanName;
							matchFound = (includeNonSingletons || mbd.isSingleton()) && isTypeMatch(beanName, type);
						}
						if (matchFound) {
							result.add(beanName);
						}
					}
				}
			   ....
		}

		// Check manually registered singletons too.
		for (String beanName : this.manualSingletonNames) {
			try {
				// In case of FactoryBean, match object created by FactoryBean.
				if (isFactoryBean(beanName)) {
					if ((includeNonSingletons || isSingleton(beanName)) && isTypeMatch(beanName, type)) {
						result.add(beanName);
						// Match found for this bean: do not match FactoryBean itself anymore.
						continue;
					}
					// In case of FactoryBean, try to match FactoryBean itself next.
					beanName = FACTORY_BEAN_PREFIX + beanName;
				}
				// Match raw bean instance (might be raw FactoryBean).
				if (isTypeMatch(beanName, type)) {
					result.add(beanName);
				}
			}
			...
		}

		return StringUtils.toStringArray(result);
}

TODO

• BeanFactory中beanDefinitionNames，manualSingletonNames等属性深入理解

最后

注册BeanPostProcessor和invokeBeanFactoryPostProcessors很像，并且没什么复杂逻辑。就是将已经注册到beanFacory的Bean筛选出BeanPostProcessor然后添加到ApplicationContext的beanPostProcessor集合中。