SSM-----BeanFactoryPostProcessor分析

本文主要是介绍SSM-----BeanFactoryPostProcessor分析，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

BeanFactoryPostProcessor

是一个beanFactory的后置处理器。

执行时机

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.

在beanFactory初始化之后，所有的bean定义已经被加载，但是bean还没有被实例化的时候执行。

执行步骤

调用redresh()，刷新容器

public AnnotationConfigApplicationContext(Class<?>... componentClasses) {this();register(componentClasses);refresh();
}

调用invokeBeanFactoryPostProcessors(beanFactory)，调用在上下文中注册为bean的工厂处理器。

// Invoke factory processors registered as beans in the context.
invokeBeanFactoryPostProcessors(beanFactory);

/*** 实例化并调用所有注册的BeanFactoryPostProcessor Bean，*遵循显式顺序（如果给定）。* 必须在单例实例化之前调用。*/
protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors());// Detect a LoadTimeWeaver and prepare for weaving, if found in the meantime// (e.g. through an @Bean method registered by ConfigurationClassPostProcessor)if (beanFactory.getTempClassLoader() == null && beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));}
}

调用PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors())

public static void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {// 如果有的话，首先调用BeanDefinitionRegistryPostProcessors。Set<String> processedBeans = new HashSet<>();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;// 调用BeanDefinitionRegistryPostProcessor的postProcessBeanDefinitionRegistry()方法registryProcessor.postProcessBeanDefinitionRegistry(registry);registryProcessors.add(registryProcessor);}else {regularPostProcessors.add(postProcessor);}}List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>();// 首先，调用实现了PriorityOrdered接口的BeanDefinitionRegistryPostProcessorString[] postProcessorNames =beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);for (String ppName : postProcessorNames) {if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));processedBeans.add(ppName);}}sortPostProcessors(currentRegistryProcessors, beanFactory);registryProcessors.addAll(currentRegistryProcessors);invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);currentRegistryProcessors.clear();// 然后，调用实现了Ordered接口的BeanDefinitionRegistryPostProcessorpostProcessorNames = 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，调用没用实现接口的BeanDefinitionRegistryPostProcessorboolean 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();}// 现在，调用到目前为止已处理的所有处理器的BeanDefinitionRegistryPostProcessors回调。invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);}else {// 调用在上下文实例中注册的工厂处理器。如果beanFactoryPostProcessor没有实现了BeanDefinitionRegistryPostProcessors接口的话，这里的beanFactoryPostProcessors.size()就是0invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);}// 以下是对beanFactoryPostProcessor的操作String[] postProcessorNames =beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);// 这里声明一些变量，并通过beanFactory获取实现对应接口的beanFactoryPostProcessor的名称，并存放到指定List中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);}}// 首先，调用实现了PriorityOrdered接口的BeanFactoryPostProcessorsortPostProcessors(priorityOrderedPostProcessors, beanFactory);invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);// 然后，调用实现了Ordered接口的BeanFactoryPostProcessorList<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<>(orderedPostProcessorNames.size());for (String postProcessorName : orderedPostProcessorNames) {orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));}sortPostProcessors(orderedPostProcessors, beanFactory);invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);// 最后，调用没有实现接口的BeanFactoryPostProcessorList<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<>(nonOrderedPostProcessorNames.size());for (String postProcessorName : nonOrderedPostProcessorNames) {nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));}invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory);// 清除bean定义缓存，因为元数据可能已经更改beanFactory.clearMetadataCache();
}

因为我们的MyBeanPostProcessor没有实现PriorityOrdered、Ordered接口，所以是最后调用的。

invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory);

/**调用给定的BeanFactoryPostProcessor bean。
*/
private static void invokeBeanFactoryPostProcessors(Collection<? extends BeanFactoryPostProcessor> postProcessors, ConfigurableListableBeanFactory beanFactory) {// 调用所有的BeanFactoryPostProcessor中的postProcessBeanFactory(beanFactory)方法for (BeanFactoryPostProcessor postProcessor : postProcessors) {postProcessor.postProcessBeanFactory(beanFactory);}
}

执行我们的MyBeanPostProcessor中自定义的postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory)方法

public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {// bean定义个数int beanDefinitionCount = beanFactory.getBeanDefinitionCount();// bean定义列表String[] beanDefinitionNames = beanFactory.getBeanDefinitionNames();System.out.println("beanFactory中一共有"+beanDefinitionCount+"个bean定义");System.out.println(ArrayUtil.arrayToString(beanDefinitionNames));
}