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【Spring-IOC】通过BeanFactoryPostProcessor实现BeanFactory的定制化

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什么是BeanFactory的定制化呢?先来看看这个接口:BeanFactoryPostProcessor

public interface BeanFactoryPostProcessor {

	void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException;

}

使用的时候可以得到beanFactory,那么beanFactory中的所有东西都能得到。beanFactory有spring提供的默认配置。比如实例化策略呀,类加载器,资源加载器,bean名称的生成器等等。当然包括注册bf的map和实例化bean的map。这样我们可以设置我们们自定义的配置。或者手动向IOC容器中添加bf或者实例,不在通过spring。

还有一层意思是当我们调用到这个接口的时候,我们向IOC注册的bean,都已经解析为BeaDefinition保存再beanFactory中了。

spring是何时调用的这个接口呢?

找到refresh方法,找到这个方法:org.springframework.context.support.AbstractApplicationContext#invokeBeanFactoryPostProcessors

	public static void invokeBeanFactoryPostProcessors(
			ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {

		// beanFactoryPostProcessors是spring内部直接添加的处理器
		// 所以得先处理spring内部的。
		Set<String> processedBeans = new HashSet<>();
		// 通常beanFactory 都会是BeanDefinitionRegistry,
		// 既是BeanDefinition注册器,又是bean对象的实例化保存工厂。
		if (beanFactory instanceof BeanDefinitionRegistry) {
			BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
			List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>();
			List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>();

			for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
				if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
					BeanDefinitionRegistryPostProcessor registryProcessor =
							(BeanDefinitionRegistryPostProcessor) postProcessor;
							// 如果是BeanDefinitionRegistryPostProcessor就先调用postProcessBeanDefinitionRegistry方法。

					registryProcessor.postProcessBeanDefinitionRegistry(registry);
					registryProcessors.add(registryProcessor);
				}
				else {
					regularPostProcessors.add(postProcessor);
				}
			}

			// 上面都是先处理spring内部直接添加的处理器,这个处理器不会走spring的实例化过程
			
			// 下面才是走spring实例化过程的。

			List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>();

			// 1. 先找PriorityOrdered接口的BeanDefinitionRegistryPostProcessor
			// 实现PriorityOrdered有高优先级
			String[] postProcessorNames =
					beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
			for (String ppName : postProcessorNames) {
				if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
					// 这里实例化了处理器
					currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
					processedBeans.add(ppName);
				}
			}
			// 排序是根据order值排序的,从小到大,越小优先级越高。
			sortPostProcessors(currentRegistryProcessors, beanFactory);
			registryProcessors.addAll(currentRegistryProcessors);
			//调用postProcessBeanDefinitionRegistry方法。

			invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
			currentRegistryProcessors.clear();

			// 2. 还是同样的逻辑:只不过是找Ordered接口的BeanDefinitionRegistryPostProcessor
			postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
			for (String ppName : postProcessorNames) {
				if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {
					currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
					processedBeans.add(ppName);
				}
			}
			sortPostProcessors(currentRegistryProcessors, beanFactory);
			registryProcessors.addAll(currentRegistryProcessors);
			invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
			currentRegistryProcessors.clear();

			// 最后找的是普通的
			boolean reiterate = true;
			while (reiterate) {
				reiterate = false;
				postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
				for (String ppName : postProcessorNames) {
					if (!processedBeans.contains(ppName)) {
						currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
						processedBeans.add(ppName);
						reiterate = true;
					}
				}
				sortPostProcessors(currentRegistryProcessors, beanFactory);
				registryProcessors.addAll(currentRegistryProcessors);
				invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
				currentRegistryProcessors.clear();
			}

			// 由于BeanDefinitionRegistryPostProcessor extends BeanFactoryPostProcessor
			// 所以这里调用了BeanFactoryPostProcessor的方法
			invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
			invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
		}

		else {
			// Invoke factory processors registered with the context instance.
			invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
		}

		//以上是处理BeanDefinitionRegistryPostProcessor ,下面是处理BeanFactoryPostProcessor
		// 还是同样的逻辑:
		String[] postProcessorNames =
				beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);

		// Separate between BeanFactoryPostProcessors that implement PriorityOrdered,
		// Ordered, and the rest.
		List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
		List<String> orderedPostProcessorNames = new ArrayList<>();
		List<String> nonOrderedPostProcessorNames = new ArrayList<>();
		for (String ppName : postProcessorNames) {
			if (processedBeans.contains(ppName)) {
				// skip - already processed in first phase above
			}
			else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
				priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
			}
			else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
				orderedPostProcessorNames.add(ppName);
			}
			else {
				nonOrderedPostProcessorNames.add(ppName);
			}
		}

		// First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.
		sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
		invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);

		// Next, invoke the BeanFactoryPostProcessors that implement Ordered.
		List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<>(orderedPostProcessorNames.size());
		for (String postProcessorName : orderedPostProcessorNames) {
			orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
		}
		sortPostProcessors(orderedPostProcessors, beanFactory);
		invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);

		// Finally, invoke all other BeanFactoryPostProcessors.
		List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<>(nonOrderedPostProcessorNames.size());
		for (String postProcessorName : nonOrderedPostProcessorNames) {
			nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
		}
		invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory);

		// Clear cached merged bean definitions since the post-processors might have
		// modified the original metadata, e.g. replacing placeholders in values...
		beanFactory.clearMetadataCache();
	}

该方法会先处理BeanDefinitionRegistryPostProcessor接口的类。

  1. 找到实现了PriorityOrdered接口的,根据order值从小到大排序。执行postProcessBeanDefinitionRegistry方法。
  2. 找到实现了Ordered接口的,根据order值从小到大排序,执行postProcessBeanDefinitionRegistry方法。
  3. 找到普通的,依旧排序,按什么排序呢?会找Order注解,根据注解的值从小到大排序;如果没有order注解,就默认是只是Integer.MAX_VALUE,最小优先级。 执行postProcessBeanDefinitionRegistry方法
  4. postProcessBeanDefinitionRegistry执行完成后,以上的所有实例会执行postProcessBeanFactory,因为BeanDefinitionRegistryPostProcessor extends BeanFactoryPostProcessor,要执行BeanFactoryPostProcessor的方法。

执行完BeanDefinitionRegistryPostProcessor类型的,下面才是执行BeanFactoryPostProcessor类型的。
逻辑是一样的。

所以如果你想定制BeanFactory中的处理器,那么实现BeanFactoryPostProcessor接口,如果你想更改beanDefinition中的值,实现BeanDefinitionRegistryPostProcessor即可偶是更好的选择。

标签:beanFactory,currentRegistryProcessors,Spring,ppName,BeanFactoryPostProcessor,Bea
来源: https://blog.csdn.net/qq_34501351/article/details/122797104