本文章基于 Spring 5.3.15
Spring IOC 的核心是
AbstractApplicationContext的refresh方法。其中一共有 13 个主要方法，这里分析第 5 个：
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 List<BeanFactoryPostProcessor> beanFactoryPostProcessors = new ArrayList<>();
public List<BeanFactoryPostProcessor> 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, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {
Set<String> processedBeans = new HashSet<>();
// 对 BeanDefinitionRegistry 类型的处理
if (beanFactory instanceof BeanDefinitionRegistry) {
BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>();
List<BeanDefinitionRegistryPostProcessor> 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<BeanDefinitionRegistryPostProcessor> 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<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
List<String> orderedPostProcessorNames = new ArrayList<>();
List<String> 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<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，调用所有其他 BeanFactoryPostProcessor
List<BeanFactoryPostProcessor> 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<Object> comparatorToUse = null;
if (beanFactory instanceof DefaultListableBeanFactory) {
comparatorToUse = ((DefaultListableBeanFactory) beanFactory).getDependencyComparator();
}
if (comparatorToUse == null) {
comparatorToUse = OrderComparator.INSTANCE;
}
postProcessors.sort(comparatorToUse);
}
2-1 调用 Bean 定义注册表增强器
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup())
private static void invokeBeanDefinitionRegistryPostProcessors( Collection<? extends BeanDefinitionRegistryPostProcessor> 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 Set<String> alreadyCreated = 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();
}
