本文章基于 Spring 5.3.15
Spring IOC 的核心是
其中一共有 13 个主要方法，这里分析第 5 个：AbstractApplicationContext的refresh方法。invokeBeanFactoryPostProcessors。
1 AbstractApplicationContext
1-1 执行 Bean 工厂的增强器
invokeBeanFactoryPostProcessors(beanFactory)
protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) { // 获取 Bean工厂 增强器 // 执行 Bean工厂 增强器 PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors()); if (!NativeDetector.inNativeImage() && beanFactory.getTempClassLoader() == null && beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) { beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory)); beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader())); }} 1-2 获取 Bean工厂 增强器
getBeanFactoryPostProcessors()
/** * Bean 工厂增强器集合 */private final ListbeanFactoryPostProcessors = new ArrayList<>();public List getBeanFactoryPostProcessors() { return this.beanFactoryPostProcessors;}
1-2 执行 Bean工厂 增强器
invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors())
2 PostProcessorRegistrationDelegate
public static void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory, ListbeanFactoryPostProcessors) { Set processedBeans = new HashSet<>(); // 对 BeanDefinitionRegistry 类型的处理 if (beanFactory instanceof BeanDefinitionRegistry) { BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory; List regularPostProcessors = new ArrayList<>(); List registryProcessors = new ArrayList<>(); // 硬编码注册的后处理器 for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) { if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) { BeanDefinitionRegistryPostProcessor registryProcessor = (BeanDefinitionRegistryPostProcessor) postProcessor; // 有自定义的方法，需要先调用 registryProcessor.postProcessBeanDefinitionRegistry(registry); registryProcessors.add(registryProcessor); } else { // 记录常规 BeanFactoryPostProcessor regularPostProcessors.add(postProcessor); } } List currentRegistryProcessors = new ArrayList<>(); // 首先，调用实现 PriorityOrdered 的 BeanDefinitionRegistryPostProcessor String[] 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); } } // 排序增强器 sortPostProcessors(currentRegistryProcessors, beanFactory); registryProcessors.addAll(currentRegistryProcessors); // 调用 Bean 定义注册表增强器 invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup()); currentRegistryProcessors.clear(); // 其次，调用实现 Ordered 的 BeanDefinitionRegistryPostProcessors 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); } } // 排序增强器 sortPostProcessors(currentRegistryProcessors, beanFactory); registryProcessors.addAll(currentRegistryProcessors); // 调用 Bean 定义注册表增强器 invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup()); currentRegistryProcessors.clear(); // 最后, 调用所有其他 BeanDefinitionRegistryPostProcessor 直到不再出现 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; } } // 排序增强器 sortPostProcessors(currentRegistryProcessors, beanFactory); registryProcessors.addAll(currentRegistryProcessors); // 调用 Bean 定义注册表增强器 invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup()); currentRegistryProcessors.clear(); } // 调用 Bean 工厂增强器 invokeBeanFactoryPostProcessors(registryProcessors, beanFactory); invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory); } else { // 调用向上下文实例注册的工厂处理器 invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory); } // 配置中读取的 BeanFactoryPostProcessor 的处理 String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false); // 将实现 PriorityOrdered、Ordered 和其余部分的 BeanFactoryPostProcessor 分开 List priorityOrderedPostProcessors = new ArrayList<>(); List orderedPostProcessorNames = new ArrayList<>(); List nonOrderedPostProcessorNames = new ArrayList<>(); // 对后处理器进行分类 for (String ppName : postProcessorNames) { if (processedBeans.contains(ppName)) { // 已经处理过则跳过 } 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 PriorityOrdered 的 BeanFactoryPostProcessor sortPostProcessors(priorityOrderedPostProcessors, beanFactory); invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory); // 接下来，调用实现 Ordered 的 BeanFactoryPostProcessors List orderedPostProcessors = new ArrayList<>(orderedPostProcessorNames.size()); for (String postProcessorName : orderedPostProcessorNames) { orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class)); } sortPostProcessors(orderedPostProcessors, beanFactory); invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory); // 最后，调用所有其他 BeanFactoryPostProcessor List nonOrderedPostProcessors = new ArrayList<>(nonOrderedPostProcessorNames.size()); for (String postProcessorName : nonOrderedPostProcessorNames) { nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class)); } invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory); // 清除元数据缓存，清除缓存的合并 bean 定义，因为后处理器可能已经修改了原始元数据，例如替换值中的占位符 beanFactory.clearMetadataCache();}
2-1 排序增强器
sortPostProcessors(currentRegistryProcessors, beanFactory)
private static void sortPostProcessors(List postProcessors, ConfigurableListableBeanFactory beanFactory) { if (postProcessors.size() <= 1) { return; } Comparator 2-1 调用 Bean 定义注册表增强器
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup())
private static void invokeBeanDefinitionRegistryPostProcessors( Collection postProcessors, BeanDefinitionRegistry registry, ApplicationStartup applicationStartup) { for (BeanDefinitionRegistryPostProcessor postProcessor : postProcessors) { StartupStep postProcessBeanDefRegistry = applicationStartup.start("spring.context.beandef-registry.post-process").tag("postProcessor", postProcessor::toString); postProcessor.postProcessBeanDefinitionRegistry(registry); postProcessBeanDefRegistry.end(); }} 2-1 清除元数据缓存
beanFactory.clearMetadataCache()
3 DefaultListableBeanFactory
public void clearMetadataCache() { // 调用父类方法 super.clearMetadataCache(); this.mergedBeanDefinitionHolders.clear(); // 按类型清除缓存 clearByTypeCache();} 3-1 调用父类方法
super.clearMetadataCache()
4 AbstractBeanFactory
public void clearMetadataCache() { this.mergedBeanDefinitions.forEach((beanName, bd) -> { // 判断 Bean 是否有资格进行元数据缓存 if (!isBeanEligibleForMetadataCaching(beanName)) { bd.stale = true; } });} 4-1 判断 Bean 是否有资格进行元数据缓存
private final SetalreadyCreated = Collections.newSetFromMap(new ConcurrentHashMap<>(256));protected boolean isBeanEligibleForMetadataCaching(String beanName) { return this.alreadyCreated.contains(beanName);}
3 DefaultListableBeanFactory
3-1 按类型清除缓存
clearByTypeCache()
private void clearByTypeCache() { this.allBeanNamesByType.clear(); this.singletonBeanNamesByType.clear();}