回顾
在Spring 容器初始化流程(上)中我们分析了上下文环境的构建和Bean工程的构建及初始化流程,接下来我们继续深入Spring容器初始化的源码中,学习Spring框架原理,在本篇涉及到的源码包含Bean工厂的后置处理器注册调用、Bean后置处理器的注册、国际化、事件广播器等
废话不多说,接着上篇我们继续分析:
5. invokeBeanFactoryPostProcessors
激活各种BeanFactory处理器
protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
// getBeanFactoryPostProcessors 获取的是 this.beanFactoryPostProcessors;
//this.beanFactoryPostProcessors 只能通过 AbstractApplicationContext.addBeanFactoryPostProcessor 方法添加
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()));
}
}
invokeBeanFactoryPostProcessors(beanFactory)
方法的主要的逻辑在PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors
方法中。
在看代码前,我们先看看这个方法的执行流程,主要是获取并调用Bean工厂后置处理器的相关方法,达到动态修改BeanDefinition的能力,如使用BeanFactoryPostProcessor
对BeanDefinition进行编辑,使用BeanDefinitionRegistryPostProcessor
对BeanDefinition进行增删。

// PostProcessorRegistrationDelegate.java
public static void invokeBeanFactoryPostProcessors(
ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {
// 定义一个 set 保存所有的 BeanFactoryPostProcessors
Set<String> processedBeans = new HashSet<>();
// 如果当前 BeanFactory 为 BeanDefinitionRegistry
// 默认的 DefaultListableBeanFactory 实现了BeanDefinitionRegistry
if (beanFactory instanceof BeanDefinitionRegistry) {
BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
// BeanFactoryPostProcessor 集合
List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>();
// BeanDefinitionRegistryPostProcessor 集合
List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>();
// 先迭代注册用户添加的 beanFactoryPostProcessors
for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
// 如果是 BeanDefinitionRegistryPostProcessor,则调用 postProcessBeanDefinitionRegistry 进行注册,
// 同时加入到 registryProcessors 集合中
BeanDefinitionRegistryPostProcessor registryProcessor =
(BeanDefinitionRegistryPostProcessor) postProcessor;
// 先执行BeanDefinitionRegistryPostProcessor的postProcessBeanDefinitionRegistry方法
// 这个方法可提供动态修改BeanDefinition的能力
registryProcessor.postProcessBeanDefinitionRegistry(registry);
registryProcessors.add(registryProcessor);
}
else {
// 否则当做普通的 BeanFactoryPostProcessor 处理
// 添加到 regularPostProcessors 集合中即可,便于后面做后续处理
regularPostProcessors.add(postProcessor);
}
}
// 用于保存当前处理的 BeanDefinitionRegistryPostProcessor
List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>();
// 首先处理实现了 PriorityOrinvokeBeanFactoryPostProcessorsdered (有限排序接口)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
sortPostProcessors(currentRegistryProcessors, beanFactory);
// 加入registryProcessors集合
registryProcessors.addAll(currentRegistryProcessors);
// 调用所有实现了 PriorityOrdered 的 BeanDefinitionRegistryPostProcessors 的 postProcessBeanDefinitionRegistry()
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
// 清空,以备下次使用
currentRegistryProcessors.clear();
// 其次,调用是实现了 Ordered(普通排序接口)的 BeanDefinitionRegistryPostProcessors
// 逻辑和 上面一样
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();
// 最后调用其他的 BeanDefinitionRegistryPostProcessors
boolean reiterate = true;
while (reiterate) {
reiterate = false;
// 获取 BeanDefinitionRegistryPostProcessor
postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
for (String ppName : postProcessorNames) {
if (!processedBeans.contains(ppName)) {
// 没有包含在 processedBeans 中的(因为包含了的都已经处理了)
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
processedBeans.add(ppName);
reiterate = true;
}
}
// 与上面处理逻辑一致
sortPostProcessors(currentRegistryProcessors, beanFactory);
registryProcessors.addAll(currentRegistryProcessors);
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
currentRegistryProcessors.clear();
}
// 调用所有 BeanDefinitionRegistryPostProcessor (包括手动注册和通过配置文件注册)
// 和 BeanFactoryPostProcessor(只有手动注册)的回调函数(postProcessBeanFactory())
invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
}
else {
// 如果不是 BeanDefinitionRegistry 只需要调用其回调函数(postProcessBeanFactory())即可
invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
}
// Do not initialize FactoryBeans here: We need to leave all regular beans
// uninitialized to let the bean factory post-processors apply to them!
String[] postProcessorNames =
beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);
// 这里同样需要区分 PriorityOrdered 、Ordered 和 no Ordered
List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
List<String> orderedPostProcessorNames = new ArrayList<>();
List<String> nonOrderedPostProcessorNames = new ArrayList<>();
for (String ppName : postProcessorNames) {
if (processedBeans.contains(ppName)) {
// 已经处理过了的,跳过
}
else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
// PriorityOrdered
priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
}
else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
// Ordered
orderedPostProcessorNames.add(ppName);
}
else {
// no Ordered
nonOrderedPostProcessorNames.add(ppName);
}
}
// First, PriorityOrdered 接口
sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);
// Next, Ordered 接口
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, no ordered
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();
}
配置注释和上面的执行流程,应该比较清楚。
扩展点:关于BeanFactoryPostProcessor和BeanDefinitionRegistryPostProcessor的区别
6. registerBeanPostProcessors
注册拦截Bean创建的Bean处理器,即注册 BeanPostProcessor
与 BeanFactoryPostProcessor
一样,也是委托给 PostProcessorRegistrationDelegate
来实现的。
// AbstractApplicationContext.java
protected void registerBeanPostProcessors(ConfigurableListableBeanFactory beanFactory) {
PostProcessorRegistrationDelegate.registerBeanPostProcessors(beanFactory, this);
}
按照惯例,先看看执行流程:

主要是获取并注册所有的BeanPostProcessor
,结合上图,看下面的代码就会跟清晰:
// PostProcessorRegistrationDelegate.java
public static void registerBeanPostProcessors(
ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {
// 所有的 BeanPostProcessors
String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);
// 注册 BeanPostProcessorChecker
// 主要用于记录一些 bean 的信息,这些 bean 不符合所有 BeanPostProcessors 处理的资格
int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));
// 区分 PriorityOrdered、Ordered 、 no ordered
List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
// 存放MergedBeanDefinitionPostProcessor类型的处理器
List<BeanPostProcessor> internalPostProcessors = new ArrayList<>();
List<String> orderedPostProcessorNames = new ArrayList<>();
List<String> nonOrderedPostProcessorNames = new ArrayList<>();
for (String ppName : postProcessorNames) {
if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
priorityOrderedPostProcessors.add(pp);
if (pp instanceof MergedBeanDefinitionPostProcessor) {
internalPostProcessors.add(pp);
}
}
else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
orderedPostProcessorNames.add(ppName);
}
else {
nonOrderedPostProcessorNames.add(ppName);
}
}
// 先注册优先排序的处理器
sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);
// 再处理普通排序的处理器
List<BeanPostProcessor> orderedPostProcessors = new ArrayList<>(orderedPostProcessorNames.size());
for (String ppName : orderedPostProcessorNames) {
BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
orderedPostProcessors.add(pp);
if (pp instanceof MergedBeanDefinitionPostProcessor) {
internalPostProcessors.add(pp);
}
}
sortPostProcessors(orderedPostProcessors, beanFactory);
registerBeanPostProcessors(beanFactory, orderedPostProcessors);
// 然后注册普通的处理器
List<BeanPostProcessor> nonOrderedPostProcessors = new ArrayList<>(nonOrderedPostProcessorNames.size());
for (String ppName : nonOrderedPostProcessorNames) {
BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
nonOrderedPostProcessors.add(pp);
if (pp instanceof MergedBeanDefinitionPostProcessor) {
internalPostProcessors.add(pp);
}
}
registerBeanPostProcessors(beanFactory, nonOrderedPostProcessors);
// 最后,重新注册所有MergedBeanDefinitionPostProcessor类型的bean。
sortPostProcessors(internalPostProcessors, beanFactory);
registerBeanPostProcessors(beanFactory, internalPostProcessors);
// 重新注册用来自动探测内部ApplicationListener的post-processor
beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
}
MergedBeanDefinitionPostProcessor
- 继承了
BeanPostProcessor
,额外提供了postProcessMergedBeanDefinition
方法,该方法把bean的BeanDefinition信息和beanType也传递到处理器中,处理器可根据传参做进一步的处理 ApplicationListenerDetector
- 该处理器的作用是扫描出所有单例的
ApplicationListener
,并添加到Spring上下文中
7. initMessageSource
初始化上下文中的资源文件,如国际化文件的处理等 。
其实该方法就是初始化一个
MessageSource
接口的实现类,主要用于国际化/i18n
// AbstractApplicationContext.java
protected void initMessageSource() {
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
if (beanFactory.containsLocalBean(MESSAGE_SOURCE_BEAN_NAME)) {
// 包含 “messageSource” 的bean
this.messageSource = beanFactory.getBean(MESSAGE_SOURCE_BEAN_NAME, MessageSource.class);
if (this.parent != null && this.messageSource instanceof HierarchicalMessageSource) {
// 如果有父类
// HierarchicalMessageSource 分级处理的 MessageSource
HierarchicalMessageSource hms = (HierarchicalMessageSource) this.messageSource;
if (hms.getParentMessageSource() == null) {
// 如果没有注册父 MessageSource,则设置为父类上下文的的 MessageSource
hms.setParentMessageSource(getInternalParentMessageSource());
}
}
if (logger.isTraceEnabled()) {
logger.trace("Using MessageSource [" + this.messageSource + "]");
}
}
else {
// 使用 空 MessageSource
DelegatingMessageSource dms = new DelegatingMessageSource();
dms.setParentMessageSource(getInternalParentMessageSource());
this.messageSource = dms;
// 注册到beanFactory中
beanFactory.registerSingleton(MESSAGE_SOURCE_BEAN_NAME, this.messageSource);
if (logger.isTraceEnabled()) {
logger.trace("No '" + MESSAGE_SOURCE_BEAN_NAME + "' bean, using [" + this.messageSource + "]");
}
}
}
方法比较简单,主要是初始化一个名为messageSource
的bean,用于国际化
8. initApplicationEventMulticaster
初始化上下文事件广播器
// AbstractApplicationContext.java
protected void initApplicationEventMulticaster() {
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
if (beanFactory.containsLocalBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME)) {
// 如果存在 applicationEventMulticaster bean,则获取并赋值
this.applicationEventMulticaster =
beanFactory.getBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, ApplicationEventMulticaster.class);
if (logger.isTraceEnabled()) {
logger.trace("Using ApplicationEventMulticaster [" + this.applicationEventMulticaster + "]");
}
}
else {
// 没有则新建 SimpleApplicationEventMulticaster,并完成 bean 的注册
this.applicationEventMulticaster = new SimpleApplicationEventMulticaster(beanFactory);
beanFactory.registerSingleton(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, this.applicationEventMulticaster);
if (logger.isTraceEnabled()) {
logger.trace("No '" + APPLICATION_EVENT_MULTICASTER_BEAN_NAME + "' bean, using " +
"[" + this.applicationEventMulticaster.getClass().getSimpleName() + "]");
}
}
}
类似initMessageSource
,如果当前容器中存在 applicationEventMulticaster
的 bean,则对 applicationEventMulticaster
赋值,否则新建一个 SimpleApplicationEventMulticaster
的对象(默认的),并完成注册。
9. onRefresh
空实现,给子类扩展初始化其他Bean
// AbstractApplicationContext.java
protected void onRefresh() throws BeansException {
// For subclasses: do nothing by default.
}
预留给 AbstractApplicationContext
的子类用于初始化其他特殊的 bean,该方法需要在所有单例 bean 初始化之前调用。
结语
到此,Spring容器的初始化流程已经走完三分之二了,坚持到这里的都是大佬啊,佩服佩服,那么继续乘胜追击吧:Spring 容器初始化流程(下)