前言
版本：spring-boot-2.7.3 | spring-context-5.3.22
在Spring Boot啟動過程中【細讀Spring Boot源碼】啟動步驟 主流程詳情7中applicationContext.refresh();這個操作是加載或刷新容器，把所有的配置轉(zhuǎn)換成響應的對象并存入容器。
下面看下他的具體執(zhí)行流程
調(diào)用主流程
主流程使用了模板模式是一個模板方法
@Override
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
// 步驟記錄器記錄開始
StartupStep contextRefresh = this.applicationStartup.start("spring.context.refresh");
// Prepare this context for refreshing.
// 準備刷新。詳看1
prepareRefresh();
// Tell the subclass to refresh the internal bean factory.
// 告訴子類刷新內(nèi)部 bean 工廠，得到Bean工廠。詳看2
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
// Prepare the bean factory for use in this context.
// 準備 bean 工廠以在此上下文中使用。詳看3
prepareBeanFactory(beanFactory);
try {
// Allows post-processing of the bean factory in context subclasses.
// 在標準初始化后修改應用程序上下文的內(nèi)部bean工廠。
// 所有bean定義都已加載，但尚未實例化bean。
// 這允許在某些應用程序上下文實現(xiàn)中注冊特殊的BeanPostProcessors等。詳看4
postProcessBeanFactory(beanFactory);
StartupStep beanPostProcess = this.applicationStartup.start("spring.context.beans.post-process");
// Invoke factory processors registered as beans in the context.
// 調(diào)用工廠處理注冊Bean到上下文
invokeBeanFactoryPostProcessors(beanFactory);
// Register bean processors that intercept bean creation.
// 從BeanFactory掃描找出BeanPostProcessor，實例化并注冊到BeanFactory里beanPostProcessors屬性中
// 詳看6
registerBeanPostProcessors(beanFactory);
beanPostProcess.end();
// Initialize message source for this context.
// 初始化消息資源。詳看7
initMessageSource();
// Initialize event multicaster for this context.
// 初始化應用事件多播器。詳看8
initApplicationEventMulticaster();
// Initialize other special beans in specific context subclasses.
// 在特定上下文子類中初始化其他特殊bean。詳看9
onRefresh();
// Check for listener beans and register them.
// 注冊監(jiān)聽器。詳看10
registerListeners();
// Instantiate all remaining (non-lazy-init) singletons.
// 實例化所有剩余的 (非惰性init) 單例。詳看11
finishBeanFactoryInitialization(beanFactory);
// Last step: publish corresponding event.
// 發(fā)布相應的事件。詳看12
finishRefresh();
}
catch (BeansException ex) {
if (logger.isWarnEnabled()) {
logger.warn("Exception encountered during context initialization - " +
"cancelling refresh attempt: " + ex);
}
// Destroy already created singletons to avoid dangling resources.
destroyBeans();
// Reset 'active' flag.
cancelRefresh(ex);
// Propagate exception to caller.
throw ex;
}
finally {
// Reset common introspection caches in Spring's core, since we
// might not ever need metadata for singleton beans anymore...
// 重置通用緩存
resetCommonCaches();
// 刷新結(jié)束
contextRefresh.end();
}
}
}
詳情1——準備刷新prepareRefresh()
Springboot容器沒有直接使用AbstractApplicationContext抽象類默認實現(xiàn)方法，Springboot容器是AnnotationConfigServletWebServerApplicationContext類，
功能如下：
- 清除之前容器緩存
- 記錄時間，撤銷關(guān)閉狀態(tài)，開啟活躍狀態(tài)
- 初始化屬性源信息(Property)
- 驗證環(huán)境信息里一些必須存在的屬性
- 把早期使用的監(jiān)聽器存入監(jiān)聽器列表
實現(xiàn)如下
protected void prepareRefresh() {
// 清除緩存，理解這里在清除之前容器的緩存。例如：nacos引導容器啟動時使用的緩存
this.scanner.clearCache();
// 再調(diào)用AbstractApplicationContext抽象類默認實現(xiàn)
super.prepareRefresh();
}
看下AbstractApplicationContext抽象類默認實現(xiàn)。
protected void prepareRefresh() {
// Switch to active.
// 切換到活躍
this.startupDate = System.currentTimeMillis();
this.closed.set(false);
this.active.set(true);
if (logger.isDebugEnabled()) {
if (logger.isTraceEnabled()) {
logger.trace("Refreshing " + this);
}
else {
logger.debug("Refreshing " + getDisplayName());
}
}
// Initialize any placeholder property sources in the context environment.
// 初始化上下文環(huán)境中的任何占位符屬性源
initPropertySources();
// Validate that all properties marked as required are resolvable:
// see ConfigurablePropertyResolver#setRequiredProperties
// 驗證標記為必需的所有屬性都是可解析的
getEnvironment().validateRequiredProperties();
// Store pre-refresh ApplicationListeners...
// 存儲預刷新 ApplicationListeners
if (this.earlyApplicationListeners == null) {
this.earlyApplicationListeners = new LinkedHashSet<>(this.applicationListeners);
}
else {
// Reset local application listeners to pre-refresh state.
// 清空
this.applicationListeners.clear();
// 把早期使用的監(jiān)聽器存入監(jiān)聽器列表
this.applicationListeners.addAll(this.earlyApplicationListeners);
}
// Allow for the collection of early ApplicationEvents,
// to be published once the multicaster is available...
// 允許早期應用程序事件的集合，一旦multicaster可用就發(fā)布
this.earlyApplicationEvents = new LinkedHashSet<>();
}
詳看2——obtainFreshBeanFactory()
獲取BeanFactory
protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
// 刷新Bean工廠
refreshBeanFactory();
// 得到Bean工廠
return getBeanFactory();
}
其中refreshBeanFactory()是AbstractApplicationContext抽象類的一個抽象方法。
子類必須實現(xiàn)此方法才能執(zhí)行實際的配置負載。在任何其他初始化工作之前，該方法都會通過refresh() 調(diào)用。
子類將創(chuàng)建一個新的bean工廠并持有對它的引用，或者返回它持有的單個BeanFactory實例。在后一種情況下，如果多次刷新上下文，通常會拋出IllegalStateException。
實際上就是：刷新內(nèi)部 bean 工廠，把當前上下文的Bean工廠切換為當前的Bean工廠。
protected final void refreshBeanFactory() throws IllegalStateException {
// 如果當前值 = 期望值，則原子地將值設(shè)置為給定的更新值
// 這個來判斷當前容器是否刷新過。即refreshed的值為false，就把值替換為true，并返回true。取反
if (!this.refreshed.compareAndSet(false, true)) {
// 如果刷新過就拋出異常
throw new IllegalStateException(
"GenericApplicationContext does not support multiple refresh attempts: just call 'refresh' once");
}
// 替換。為序列化目的指定一個id，如果需要的話，允許這個BeanFactory從這個id反序列化回BeanFactory對象。
this.beanFactory.setSerializationId(getId());
}
詳看3——prepareBeanFactory(beanFactory)
設(shè)置這個工廠（BeanFactory）的標準上下文特征（一些配置），例如上下文的類加載器和后處理器。
在這之前先了解幾個方法：
-
void addBeanPostProcessor(BeanPostProcessor beanPostProcessor);這個方法：添加一個新的BeanPostProcessor，該處理器將應用于該工廠創(chuàng)建的bean。在工廠配置期間調(diào)用。
注意: 此處提交的后處理器將按注冊順序應用; 通過實現(xiàn)org.springframework.core.Ordered接口表達的任何排序語義將被忽略。
請注意，自動檢測的后處理器 (例如，在ApplicationContext中作為bean) 將始終在以編程方式注冊的處理器之后應用。
-
void ignoreDependencyInterface(Class<?> ifc);這個方法：忽略給定的依賴接口進行自動查詢。
這通常將由應用程序上下文用于注冊依賴關(guān)系，這些依賴關(guān)系以其他方式解決，例如通過BeanFactoryAware的BeanFactory或通過ApplicationContext的ApplicationContext。
默認情況下，僅忽略BeanFactoryAware接口。對于要忽略的其他類型，請為每種類型調(diào)用此方法。 -
void registerResolvableDependency(Class<?> dependencyType, @Nullable Object autowiredValue);這個方法：用相應的autowired值注冊一個特殊的依賴類型。這適用于factorycontext引用，這些引用應該是自動的，但在工廠中未定義為bean: 例如，ApplicationContext類型的依賴關(guān)系解析為bean所在的ApplicationContext實例。
注意: 在普通BeanFactory中沒有注冊這樣的默認類型，甚至對于BeanFactory接口本身也沒有。
Spring源碼筆記之beanFactory.registerResolvableDependency(）方法，這個文章里解釋的很清楚，還有使用示例。
-
void registerSingleton(String beanName, Object singletonObject);這個方法：在給定的bean名稱下，在bean注冊表中將給定的現(xiàn)有對象注冊為singleton。
給定的實例應該是完全初始化的; 注冊表不會執(zhí)行任何初始化回調(diào) (特別是，它不會調(diào)用InitializingBean的afterPropertiesSet方法)。給定的實例也不會收到任何破壞回調(diào) (如dispoablebean的destroy方法)。
在full BeanFactory中運行時: 如果您的bean應該接收初始化和/或銷毀回調(diào)，請注冊bean定義而不是現(xiàn)有實例。
通常在注冊表配置期間調(diào)用，但也可以用于單例的運行時注冊。因此，注冊表實現(xiàn)應該同步單例訪問; 如果它支持BeanFactory的單例延遲初始化，則無論如何都必須這樣做
根據(jù)上面的鋪墊，看下面就很順暢。分為3部分
- 設(shè)置表達式解析器
- 添加應用上下文Aware的BeanPostProcessor和忽略EnvironmentAware、EmbeddedValueResolverAware、ResourceLoaderAware、ApplicationEventPublisherAware、MessageSourceAware、ApplicationStartupAware
- 設(shè)置特殊的類型對應的bean。BeanFactory對應剛剛獲取的BeanFactory；ResourceLoader、ApplicationEventPublisher、ApplicationContext這3個接口對應的bean都設(shè)置為當前的Spring容器
- 注入一些其它信息的bean，比如environment、systemProperties等
protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
// Tell the internal bean factory to use the context's class loader etc.
// 將內(nèi)部bean工廠使用上下文的類加載器等
beanFactory.setBeanClassLoader(getClassLoader());
// 忽略表達式
if (!shouldIgnoreSpel) {
// 設(shè)置Bean表達式解析器
beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
}
// 添加屬性編輯器注冊器
beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));
// Configure the bean factory with context callbacks.
// 添加上下文感知處理器
beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
// 忽略環(huán)境感知
beanFactory.ignoreDependencyInterface(EnvironmentAware.class);
// 忽略內(nèi)含價值解析器感知
beanFactory.ignoreDependencyInterface(EmbeddedValueResolverAware.class);
// 忽略資源加載感知
beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class);
// 忽略應用程序事件發(fā)布者感知
beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class);
// 忽略消息資源感知
beanFactory.ignoreDependencyInterface(MessageSourceAware.class);
// 忽略應用上下文感知
beanFactory.ignoreDependencyInterface(ApplicationContextAware.class);
// 忽略應用啟動步驟感知
beanFactory.ignoreDependencyInterface(ApplicationStartupAware.class);
// BeanFactory interface not registered as resolvable type in a plain factory.
// MessageSource registered (and found for autowiring) as a bean.
// 其他類想要用BeanFactory.class，就注入beanFactory。下面幾個同理
beanFactory.registerResolvableDependency(BeanFactory.class, beanFactory);
beanFactory.registerResolvableDependency(ResourceLoader.class, this);
beanFactory.registerResolvableDependency(ApplicationEventPublisher.class, this);
beanFactory.registerResolvableDependency(ApplicationContext.class, this);
// Register early post-processor for detecting inner beans as ApplicationListeners.
// 注冊早期的后處理器，用于檢測內(nèi)部bean作為應用程序偵聽器。
beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(this));
// Detect a LoadTimeWeaver and prepare for weaving, if found.
if (!NativeDetector.inNativeImage() && beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
// Set a temporary ClassLoader for type matching.
beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
}
// Register default environment beans.
// 注入一些其它信息的bean，比如environment、systemProperties等
if (!beanFactory.containsLocalBean(ENVIRONMENT_BEAN_NAME)) {
beanFactory.registerSingleton(ENVIRONMENT_BEAN_NAME, getEnvironment());
}
if (!beanFactory.containsLocalBean(SYSTEM_PROPERTIES_BEAN_NAME)) {
beanFactory.registerSingleton(SYSTEM_PROPERTIES_BEAN_NAME, getEnvironment().getSystemProperties());
}
if (!beanFactory.containsLocalBean(SYSTEM_ENVIRONMENT_BEAN_NAME)) {
beanFactory.registerSingleton(SYSTEM_ENVIRONMENT_BEAN_NAME, getEnvironment().getSystemEnvironment());
}
if (!beanFactory.containsLocalBean(APPLICATION_STARTUP_BEAN_NAME)) {
beanFactory.registerSingleton(APPLICATION_STARTUP_BEAN_NAME, getApplicationStartup());
}
}
詳看4——postProcessBeanFactory(beanFactory);
這步處理所有的Bean
protected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {
super.postProcessBeanFactory(beanFactory);
if (this.basePackages != null && this.basePackages.length > 0) {
this.scanner.scan(this.basePackages);
}
if (!this.annotatedClasses.isEmpty()) {
this.reader.register(ClassUtils.toClassArray(this.annotatedClasses));
}
}
代碼super.postProcessBeanFactory(beanFactory)詳情
protected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {
// 添加一個BeanPostProcessor,
// 用于初始化ServletContextAware、ServletConfigAware時使用，即在初始化ServletContext或ServletConfig之前使用
beanFactory.addBeanPostProcessor(new WebApplicationContextServletContextAwareProcessor(this));
// 忽略給定的ServletContextAware依賴接口進行自動查詢。
// 默認僅忽略BeanFactoryAware接口。對于要忽略的其他類型，請為每種類型調(diào)用此方法
beanFactory.ignoreDependencyInterface(ServletContextAware.class);
// 注冊Web應用程序范圍，request范圍和session范圍
registerWebApplicationScopes();
}
代碼registerWebApplicationScopes();詳情
private void registerWebApplicationScopes() {
// 這個是內(nèi)部類，里面處理從beanFactory里取request、session對應的話就把域包裝到set里封裝成這個對象
ExistingWebApplicationScopes existingScopes = new ExistingWebApplicationScopes(getBeanFactory());
// 使用指定的beanFactory注冊web具體request、session、globalSession范圍
WebApplicationContextUtils.registerWebApplicationScopes(getBeanFactory());
// 把上面的域恢復注冊到beanFactory里，以確保后面對域的正確使用。
// 上面方法內(nèi)注冊了一個新的request、session、application，這里如果之前有那么就恢復之前的
existingScopes.restore();
}
代碼WebApplicationContextUtils.registerWebApplicationScopes(getBeanFactory());詳情
public static void registerWebApplicationScopes(ConfigurableListableBeanFactory beanFactory) {
registerWebApplicationScopes(beanFactory, null);
}
public static void registerWebApplicationScopes(ConfigurableListableBeanFactory beanFactory,
@Nullable ServletContext sc) {
// 注冊一個新的request域
beanFactory.registerScope(WebApplicationContext.SCOPE_REQUEST, new RequestScope());
// 注冊一個新的session域
beanFactory.registerScope(WebApplicationContext.SCOPE_SESSION, new SessionScope());
// 如果服務上下文不為空，
if (sc != null) {
ServletContextScope appScope = new ServletContextScope(sc);
// 注冊一個application域
beanFactory.registerScope(WebApplicationContext.SCOPE_APPLICATION, appScope);
// 并注冊為ServletContext屬性，以供ContextCleanupListener檢測。
sc.setAttribute(ServletContextScope.class.getName(), appScope);
}
// 為request、response、session、webRequest注冊解析依賴
beanFactory.registerResolvableDependency(ServletRequest.class, new RequestObjectFactory());
beanFactory.registerResolvableDependency(ServletResponse.class, new ResponseObjectFactory());
beanFactory.registerResolvableDependency(HttpSession.class, new SessionObjectFactory());
beanFactory.registerResolvableDependency(WebRequest.class, new WebRequestObjectFactory());
if (jsfPresent) {
FacesDependencyRegistrar.registerFacesDependencies(beanFactory);
}
}
詳看5——invokeBeanFactoryPostProcessors(beanFactory);
調(diào)用BeanFactory后置處理，把所有的Bean注冊到beanFactory。
invokeBeanFactoryPostProcessors是一個方法。用于調(diào)用 BeanFactoryPostProcessor 接口實現(xiàn)類的方法。它的作用是在 Spring 容器初始化過程中，在 BeanDefinition 加載完成、實例化之前，給予開發(fā)者一個機會去修改或者擴展已注冊的 BeanDefinition。
需要了解接口BeanPostProcessor，看這篇文章
【細讀Spring Boot源碼】Spring擴展點接口BeanPostProcessor-儲備
protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
// 調(diào)用一個靜態(tài)處理方法
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 (!NativeDetector.inNativeImage() && beanFactory.getTempClassLoader() == null && beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
}
}
源碼中有一段WARNING，譯文如下：
盡管看起來這個方法的主體很容易被重構(gòu)，以避免使用多個循環(huán)和多個列表，但使用多個列表和多次傳遞處理器的名稱是有意的。我們必須確保我們遵守 PriorityOrdered 和 Ordered 處理器的契約。具體來說，我們不能導致處理器被實例化（通過getBean()調(diào)用）或以錯誤的順序在 ApplicationContext 中注冊。在提交改變此方法的拉動請求（PR）之前，請查看所有涉及改變PostProcessorRegistrationDelegate的被拒絕的PR列表，以確保你的建議不會導致破壞性的改變：https://github.com/spring-projects/spring-framework/issues?q=PostProcessorRegistrationDelegate+is%3Aclosed+label%3A%22status%3A+declined%22
梳理一下下面大段代碼的邏輯，整體分為2部分。
第一部分：這里把早期添加到context里的BeanFactoryPostProcessor執(zhí)行分類、排序、invoke
這里是處理Bean定義注冊的邏輯
if (beanFactory instanceof BeanDefinitionRegistry) {
...
} else {
...
}
第二部分：這里是后半部分，從中取出BeanDefinitionRegistryPostProcessor類的所有實現(xiàn)，然后分類、排序、invoke
public static void invokeBeanFactoryPostProcessors(
ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {
// 翻譯在上面
// WARNING: Although it may appear that the body of this method can be easily
// refactored to avoid the use of multiple loops and multiple lists, the use
// of multiple lists and multiple passes over the names of processors is
// intentional. We must ensure that we honor the contracts for PriorityOrdered
// and Ordered processors. Specifically, we must NOT cause processors to be
// instantiated (via getBean() invocations) or registered in the ApplicationContext
// in the wrong order.
//
// Before submitting a pull request (PR) to change this method, please review the
// list of all declined PRs involving changes to PostProcessorRegistrationDelegate
// to ensure that your proposal does not result in a breaking change:
// https://github.com/spring-projects/spring-framework/issues?q=PostProcessorRegistrationDelegate+is%3Aclosed+label%3A%22status%3A+declined%22
// Invoke BeanDefinitionRegistryPostProcessors first, if any.
// 首先調(diào)用BeanDefinitionRegistryPostProcessors，如果存在
Set<String> processedBeans = new HashSet<>();
if (beanFactory instanceof BeanDefinitionRegistry) {
BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>();
List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>();
// 循環(huán)處理出入的beanFactoryPostProcessors
for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
BeanDefinitionRegistryPostProcessor registryProcessor =
(BeanDefinitionRegistryPostProcessor) postProcessor;
// 如果是BeanDefinitionRegistryPostProcessor調(diào)用這個擴展鉤子
registryProcessor.postProcessBeanDefinitionRegistry(registry);
// 處理完添加到常規(guī)的PostProcessors
registryProcessors.add(registryProcessor);
}
else {
// 添加到常規(guī)的PostProcessors
regularPostProcessors.add(postProcessor);
}
}
// Do not initialize FactoryBeans here: We need to leave all regular beans
// uninitialized to let the bean factory post-processors apply to them!
// Separate between BeanDefinitionRegistryPostProcessors that implement
// PriorityOrdered, Ordered, and the rest.
List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>();
// First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.
// 得到所有BeanDefinitionRegistryPostProcessor類型的Bean名稱
String[] postProcessorNames =
beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
// 按類型分類，處理PriorityOrdered類型
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);
// 添加需要注冊的列表
registryProcessors.addAll(currentRegistryProcessors);
// 注冊，調(diào)用Bean定義注冊表后處理器
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup());
currentRegistryProcessors.clear();
// Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.
postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
// 按類型分類，處理Ordered類型
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);
// 注冊
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup());
currentRegistryProcessors.clear();
// Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear.
// 最后注冊處理其他類型BeanDefinitionRegistryPostProcessor
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, beanFactory.getApplicationStartup());
currentRegistryProcessors.clear();
}
// Now, invoke the postProcessBeanFactory callback of all processors handled so far.
// 現(xiàn)在，調(diào)用到目前為止處理的所有處理器的postProcessBeanFactory回調(diào)。
invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
}
else {
// Invoke factory processors registered with the context instance.
// 直接調(diào)用處理的所有處理器的postProcessBeanFactory回調(diào)。
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!、
// 獲取所有BeanFactoryPostProcessor
String[] postProcessorNames =
beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);
// Separate between BeanFactoryPostProcessors that implement PriorityOrdered,
// Ordered, and the rest.
// 分類
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);
}
}
// 先處理priorityOrdered的PostProcessor
// First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.
sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);
// Next, invoke the BeanFactoryPostProcessors that implement Ordered.
// 處理調(diào)用Ordered的PostProcessor
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.
// 最后調(diào)用剩余的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();
}
BeanFactoryPostProcessor 是在 Spring 容器實例化 Bean 之前調(diào)用的接口。
它允許您對應用程序上下文的 BeanFactory 進行自定義修改。BeanFactoryPostProcessor 的實現(xiàn)類可以修改 Bean 的定義，添加額外的屬性或修改屬性值。
它通常用于在應用程序上下文準備就緒之前對 Bean 定義進行修改，例如更改 Bean 的作用域、添加屬性占位符解析器等。BeanFactoryPostProcessor 在容器啟動時執(zhí)行，只對配置的 BeanFactory 生效。
詳看6——registerBeanPostProcessors(beanFactory);
發(fā)現(xiàn)注冊BeanPostProcessor
protected void registerBeanPostProcessors(ConfigurableListableBeanFactory beanFactory) {
// 這里使用了一個靜態(tài)方法
PostProcessorRegistrationDelegate.registerBeanPostProcessors(beanFactory, this);
}
看下registerBeanPostProcessors
源碼中有一段WARNING，譯文如下：
盡管看起來這個方法的主體很容易被重構(gòu)，以避免使用多個循環(huán)和多個列表，但使用多個列表和多次傳遞處理器的名稱是有意的。我們必須確保我們遵守 PriorityOrdered 和 Ordered 處理器的契約。具體來說，我們不能導致處理器被實例化（通過getBean()調(diào)用）或以錯誤的順序在 ApplicationContext 中注冊。在提交改變此方法的拉動請求（PR）之前，請查看所有涉及改變PostProcessorRegistrationDelegate的被拒絕的PR列表，以確保你的建議不會導致破壞性的改變：https://github.com/spring-projects/spring-framework/issues?q=PostProcessorRegistrationDelegate+is%3Aclosed+label%3A%22status%3A+declined%22
public static void registerBeanPostProcessors(
ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {
// 這段翻譯看上面
// WARNING: Although it may appear that the body of this method can be easily
// refactored to avoid the use of multiple loops and multiple lists, the use
// of multiple lists and multiple passes over the names of processors is
// intentional. We must ensure that we honor the contracts for PriorityOrdered
// and Ordered processors. Specifically, we must NOT cause processors to be
// instantiated (via getBean() invocations) or registered in the ApplicationContext
// in the wrong order.
//
// Before submitting a pull request (PR) to change this method, please review the
// list of all declined PRs involving changes to PostProcessorRegistrationDelegate
// to ensure that your proposal does not result in a breaking change:
// https://github.com/spring-projects/spring-framework/issues?q=PostProcessorRegistrationDelegate+is%3Aclosed+label%3A%22status%3A+declined%22
// 取到所有BeanPostProcessor類型的Bean名稱
String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);
// Register BeanPostProcessorChecker that logs an info message when
// a bean is created during BeanPostProcessor instantiation, i.e. when
// a bean is not eligible for getting processed by all BeanPostProcessors.
// 重新計算BeanPostProcessor的數(shù)量
int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
// 添加
beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));
// Separate between BeanPostProcessors that implement PriorityOrdered,
// Ordered, and the rest.
// 根據(jù)不同的排序方式進行分類
List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
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);
}
}
// First, register the BeanPostProcessors that implement PriorityOrdered.
// 注冊PriorityOrdered類型的BeanPostProcessors
sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);
// Next, register the BeanPostProcessors that implement Ordered.
// 注冊O(shè)rdered類型的BeanPostProcessors
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);
// Now, register all regular BeanPostProcessors.
// 注冊所有常規(guī)的BeanPostProcessors
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);
// Finally, re-register all internal BeanPostProcessors.
// 最后，再注冊所有的內(nèi)部BeanPostProcessors
sortPostProcessors(internalPostProcessors, beanFactory);
registerBeanPostProcessors(beanFactory, internalPostProcessors);
// Re-register post-processor for detecting inner beans as ApplicationListeners,
// moving it to the end of the processor chain (for picking up proxies etc).
// 重新注冊后處理器，以檢測內(nèi)部bean作為應用程序偵聽器，將其移動到處理器鏈的末端 (用于拾取代理等)
beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
}
看下實際的注冊邏輯，實際上還是調(diào)用了factory.addBeanPostProcessor()方法跟上面Spring的原理一樣。
private static void registerBeanPostProcessors(
ConfigurableListableBeanFactory beanFactory, List<BeanPostProcessor> postProcessors) {
if (beanFactory instanceof AbstractBeanFactory) {
// Bulk addition is more efficient against our CopyOnWriteArrayList there
((AbstractBeanFactory) beanFactory).addBeanPostProcessors(postProcessors);
}
else {
for (BeanPostProcessor postProcessor : postProcessors) {
beanFactory.addBeanPostProcessor(postProcessor);
}
}
}
從原來的位置移除，在重新添加this.beanPostProcessors是BeanPostProcessorCacheAwareList的實例。
BeanPostProcessorCacheAwareList繼承了CopyOnWriteArrayList
public void addBeanPostProcessor(BeanPostProcessor beanPostProcessor) {
Assert.notNull(beanPostProcessor, "BeanPostProcessor must not be null");
// Remove from old position, if any
this.beanPostProcessors.remove(beanPostProcessor);
// Add to end of list
this.beanPostProcessors.add(beanPostProcessor);
}
詳看7——initMessageSource();
初始化消息源（MessageSource），以支持國際化和本地化的消息處理
protected void initMessageSource() {
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
// beanFactory中包好messageSource的Bean
if (beanFactory.containsLocalBean(MESSAGE_SOURCE_BEAN_NAME)) {
// 取到
this.messageSource = beanFactory.getBean(MESSAGE_SOURCE_BEAN_NAME, MessageSource.class);
// 讓消息來源知道父消息來源
if (this.parent != null && this.messageSource instanceof HierarchicalMessageSource) {
HierarchicalMessageSource hms = (HierarchicalMessageSource) this.messageSource;
if (hms.getParentMessageSource() == null) {
// Only set parent context as parent MessageSource if no parent MessageSource
// registered already.
hms.setParentMessageSource(getInternalParentMessageSource());
}
}
if (logger.isTraceEnabled()) {
logger.trace("Using MessageSource [" + this.messageSource + "]");
}
}
else {
// Use empty MessageSource to be able to accept getMessage calls.
// 使用空MessageSource能夠接受getMessage調(diào)用
DelegatingMessageSource dms = new DelegatingMessageSource();
dms.setParentMessageSource(getInternalParentMessageSource());
this.messageSource = dms;
beanFactory.registerSingleton(MESSAGE_SOURCE_BEAN_NAME, this.messageSource);
if (logger.isTraceEnabled()) {
logger.trace("No '" + MESSAGE_SOURCE_BEAN_NAME + "' bean, using [" + this.messageSource + "]");
}
}
}
詳看8——initApplicationEventMulticaster();
protected void initApplicationEventMulticaster() {
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
// beanFactory中包含applicationEventMulticaster
if (beanFactory.containsLocalBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME)) {
// 取出來賦值
this.applicationEventMulticaster =
beanFactory.getBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, ApplicationEventMulticaster.class);
if (logger.isTraceEnabled()) {
logger.trace("Using ApplicationEventMulticaster [" + this.applicationEventMulticaster + "]");
}
}
else {
// 沒有初始化一個簡單的事件多播器
this.applicationEventMulticaster = new SimpleApplicationEventMulticaster(beanFactory);
// 注冊單例到beanFactory里
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() + "]");
}
}
}
看下簡單事件多播器初始化做了什么
public SimpleApplicationEventMulticaster(BeanFactory beanFactory) {
// 設(shè)置beanFactory
setBeanFactory(beanFactory);
}
詳看9——onRefresh()
在ServletWebServerApplicationContext中，onRefresh是創(chuàng)建webServer
protected void onRefresh() {
super.onRefresh();
try {
createWebServer();
}
catch (Throwable ex) {
throw new ApplicationContextException("Unable to start web server", ex);
}
}
創(chuàng)建webServer詳情
private void createWebServer() {
WebServer webServer = this.webServer;
ServletContext servletContext = getServletContext();
// 都沒獲取到
if (webServer == null && servletContext == null) {
StartupStep createWebServer = this.getApplicationStartup().start("spring.boot.webserver.create");
// 通過ServletWebServerFactory獲取Bean
ServletWebServerFactory factory = getWebServerFactory();
createWebServer.tag("factory", factory.getClass().toString());
// 通過工廠獲取webServer
this.webServer = factory.getWebServer(getSelfInitializer());
createWebServer.end();
// 注冊webServerGracefulShutdown
getBeanFactory().registerSingleton("webServerGracefulShutdown",
new WebServerGracefulShutdownLifecycle(this.webServer));
// 注冊webServerStartStop
getBeanFactory().registerSingleton("webServerStartStop",
new WebServerStartStopLifecycle(this, this.webServer));
}
else if (servletContext != null) {
try {
getSelfInitializer().onStartup(servletContext);
}
catch (ServletException ex) {
throw new ApplicationContextException("Cannot initialize servlet context", ex);
}
}
// 初始化屬性資源
initPropertySources();
}
protected void initPropertySources() {
ConfigurableEnvironment env = getEnvironment();
if (env instanceof ConfigurableWebEnvironment) {
((ConfigurableWebEnvironment) env).initPropertySources(this.servletContext, null);
}
}
public void initPropertySources(@Nullable ServletContext servletContext, @Nullable ServletConfig servletConfig) {
WebApplicationContextUtils.initServletPropertySources(getPropertySources(), servletContext, servletConfig);
}
設(shè)置servletContextInitParams、servletConfigInitParams屬性
public static void initServletPropertySources(MutablePropertySources sources,
@Nullable ServletContext servletContext, @Nullable ServletConfig servletConfig) {
Assert.notNull(sources, "'propertySources' must not be null");
// servletContextInitParams
String name = StandardServletEnvironment.SERVLET_CONTEXT_PROPERTY_SOURCE_NAME;
if (servletContext != null && sources.get(name) instanceof StubPropertySource) {
sources.replace(name, new ServletContextPropertySource(name, servletContext));
}
// servletConfigInitParams
name = StandardServletEnvironment.SERVLET_CONFIG_PROPERTY_SOURCE_NAME;
if (servletConfig != null && sources.get(name) instanceof StubPropertySource) {
sources.replace(name, new ServletConfigPropertySource(name, servletConfig));
}
}
詳看10——registerListeners();
protected void registerListeners() {
// Register statically specified listeners first.
// 首先注冊靜態(tài)指定的偵聽器。
for (ApplicationListener<?> listener : getApplicationListeners()) {
getApplicationEventMulticaster().addApplicationListener(listener);
}
// Do not initialize FactoryBeans here: We need to leave all regular beans
// uninitialized to let post-processors apply to them!
// 找打所有的ApplicationListener接口實現(xiàn)類，都添加給多播器
String[] listenerBeanNames = getBeanNamesForType(ApplicationListener.class, true, false);
for (String listenerBeanName : listenerBeanNames) {
getApplicationEventMulticaster().addApplicationListenerBean(listenerBeanName);
}
// Publish early application events now that we finally have a multicaster...
// 得到早期應用事件
Set<ApplicationEvent> earlyEventsToProcess = this.earlyApplicationEvents;
this.earlyApplicationEvents = null;
if (!CollectionUtils.isEmpty(earlyEventsToProcess)) {
for (ApplicationEvent earlyEvent : earlyEventsToProcess) {
// 執(zhí)行早期應用事件
getApplicationEventMulticaster().multicastEvent(earlyEvent);
}
}
}
詳看11——finishBeanFactoryInitialization(beanFactory);
protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
// Initialize conversion service for this context.
// 為此上下文初始化轉(zhuǎn)換服務。
if (beanFactory.containsBean(CONVERSION_SERVICE_BEAN_NAME) &&
beanFactory.isTypeMatch(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class)) {
beanFactory.setConversionService(
beanFactory.getBean(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class));
}
// Register a default embedded value resolver if no BeanFactoryPostProcessor
// (such as a PropertySourcesPlaceholderConfigurer bean) registered any before:
// at this point, primarily for resolution in annotation attribute values.
// 有嵌入值解析器
if (!beanFactory.hasEmbeddedValueResolver()) {
beanFactory.addEmbeddedValueResolver(strVal -> getEnvironment().resolvePlaceholders(strVal));
}
// Initialize LoadTimeWeaverAware beans early to allow for registering their transformers early.
// 初始化LoadTimeWeaverAware
String[] weaverAwareNames = beanFactory.getBeanNamesForType(LoadTimeWeaverAware.class, false, false);
for (String weaverAwareName : weaverAwareNames) {
getBean(weaverAwareName);
}
// Stop using the temporary ClassLoader for type matching.
// 停止使用臨時類加載器進行類型匹配
beanFactory.setTempClassLoader(null);
// Allow for caching all bean definition metadata, not expecting further changes.
// 允許緩存所有bean定義元數(shù)據(jù)，不期望進一步更改。凍結(jié)bean定義名稱
beanFactory.freezeConfiguration();
// Instantiate all remaining (non-lazy-init) singletons.
// 實例化所有剩余的 (非惰性init) 單例
beanFactory.preInstantiateSingletons();
}
實例化所有剩余的 (非惰性init) 單例方法詳情：
public void preInstantiateSingletons() throws BeansException {
if (logger.isTraceEnabled()) {
logger.trace("Pre-instantiating singletons in " + this);
}
// Iterate over a copy to allow for init methods which in turn register new bean definitions.
// While this may not be part of the regular factory bootstrap, it does otherwise work fine.
List<String> beanNames = new ArrayList<>(this.beanDefinitionNames);
// Trigger initialization of all non-lazy singleton beans...
// 循環(huán)初始化所有非惰性Bean，通過BeanName
for (String beanName : beanNames) {
// 獲取合并的本地Bean定義
RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
// 不是抽象的、是單例、不是懶加載
if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
// 是工廠Bean，前綴有&符號為工廠Bean
if (isFactoryBean(beanName)) {
Object bean = getBean(FACTORY_BEAN_PREFIX + beanName);
if (bean instanceof FactoryBean) {
FactoryBean<?> factory = (FactoryBean<?>) bean;
boolean isEagerInit;
if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) {
isEagerInit = AccessController.doPrivileged(
(PrivilegedAction<Boolean>) ((SmartFactoryBean<?>) factory)::isEagerInit,
getAccessControlContext());
}
else {
isEagerInit = (factory instanceof SmartFactoryBean &&
((SmartFactoryBean<?>) factory).isEagerInit());
}
// 根據(jù)上面條件判斷需要初始化就初始化
if (isEagerInit) {
getBean(beanName);
}
}
}
else {
// 最重要的方法。BeanFactory接口的getBean(String name)。通過這個方法初始化以及實例化Bean
getBean(beanName);
}
}
}
// Trigger post-initialization callback for all applicable beans...
// 觸發(fā)所有適用bean的初始化后回調(diào)
for (String beanName : beanNames) {
Object singletonInstance = getSingleton(beanName);
if (singletonInstance instanceof SmartInitializingSingleton) {
StartupStep smartInitialize = this.getApplicationStartup().start("spring.beans.smart-initialize")
.tag("beanName", beanName);
SmartInitializingSingleton smartSingleton = (SmartInitializingSingleton) singletonInstance;
if (System.getSecurityManager() != null) {
AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
smartSingleton.afterSingletonsInstantiated();
return null;
}, getAccessControlContext());
}
else {
smartSingleton.afterSingletonsInstantiated();
}
smartInitialize.end();
}
}
}
詳看12——finishRefresh();
protected void finishRefresh() {
// Clear context-level resource caches (such as ASM metadata from scanning).
// 清除上下文級別的資源緩存 (例如來自掃描的ASM元數(shù)據(jù))
clearResourceCaches();
// Initialize lifecycle processor for this context.
// 為此上下文初始化生命周期處理器
initLifecycleProcessor();
// Propagate refresh to lifecycle processor first.
// 首先將刷新傳播到生命周期處理器。
getLifecycleProcessor().onRefresh();
// Publish the final event.
// 發(fā)布最終事件
publishEvent(new ContextRefreshedEvent(this));
// Participate in LiveBeansView MBean, if active.
// 如果活躍，則參與LiveBeansView MBean。
if (!NativeDetector.inNativeImage()) {
LiveBeansView.registerApplicationContext(this);
}
}
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