-- 以下内容均基于2.1.8.RELEASE版本

紧接着上一篇[(四)SpringBoot启动过程的分析-预处理ApplicationContext] (https://www.cnblogs.com/lukama/p/14583241.html), 本文将分析上下文容器准备完成之后开始执行刷新流程

// SpringApplication.java

private void refreshContext(ConfigurableApplicationContext context) {
refresh(context);
if (this.registerShutdownHook) {
try {
context.registerShutdownHook();
}
catch (AccessControlException ex) {
// Not allowed in some environments.
}
}
} // 真正的refresh方法在AbstractApplicationContext类中
protected void refresh(ApplicationContext applicationContext) {
Assert.isInstanceOf(AbstractApplicationContext.class, applicationContext);
((AbstractApplicationContext) applicationContext).refresh();
} // AbstractApplicationContext.java
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
// Prepare this context for refreshing.
prepareRefresh(); // Tell the subclass to refresh the internal bean factory.
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory(); // Prepare the bean factory for use in this context.
prepareBeanFactory(beanFactory); try {
// Allows post-processing of the bean factory in context subclasses.
postProcessBeanFactory(beanFactory); // Invoke factory processors registered as beans in the context.
invokeBeanFactoryPostProcessors(beanFactory); // Register bean processors that intercept bean creation.
registerBeanPostProcessors(beanFactory); // Initialize message source for this context.
initMessageSource(); // Initialize event multicaster for this context.
initApplicationEventMulticaster(); // Initialize other special beans in specific context subclasses.
onRefresh(); // Check for listener beans and register them.
registerListeners(); // Instantiate all remaining (non-lazy-init) singletons.
finishBeanFactoryInitialization(beanFactory); // Last step: publish corresponding event.
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...
resetCommonCaches();
}
}
}

在refresh方法中清晰的划分了刷新容器的步骤。

prepareRefresh()

主要用于清除元数据Reader的缓存,设置应用程序启动的时间,设置应用程序的活动标记,初始化属性源。

// AnnotationConfigServletWebServerApplicationContext.java

protected void prepareRefresh() {
this.scanner.clearCache();
super.prepareRefresh();
} // AbstractApplicationContext.java protected void prepareRefresh() {
// 设置开始执行的时间和活动标记
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());
}
} // ①
initPropertySources(); // ②
// Validate that all properties marked as required are resolvable:
// see ConfigurablePropertyResolver#setRequiredProperties
getEnvironment().validateRequiredProperties(); // ③
// Store pre-refresh ApplicationListeners...
if (this.earlyApplicationListeners == null) {
this.earlyApplicationListeners = new LinkedHashSet<>(this.applicationListeners);
}
else {
// Reset local application listeners to pre-refresh state.
this.applicationListeners.clear();
this.applicationListeners.addAll(this.earlyApplicationListeners);
} // Allow for the collection of early ApplicationEvents,
// to be published once the multicaster is available...
this.earlyApplicationEvents = new LinkedHashSet<>();
}

① - 初始化属性资源

// StandardServletEnvironment.java

public void initPropertySources(@Nullable ServletContext servletContext, @Nullable ServletConfig servletConfig) {
WebApplicationContextUtils.initServletPropertySources(getPropertySources(), servletContext, servletConfig);
} // WebApplicationContextUtils.java public static void initServletPropertySources(MutablePropertySources sources,
@Nullable ServletContext servletContext, @Nullable ServletConfig servletConfig) { Assert.notNull(sources, "'propertySources' must not be null");
String name = StandardServletEnvironment.SERVLET_CONTEXT_PROPERTY_SOURCE_NAME;
// servletContext不为空且有相关配置的情况
if (servletContext != null && sources.contains(name) && sources.get(name) instanceof StubPropertySource) {
sources.replace(name, new ServletContextPropertySource(name, servletContext));
}
// servletConfig不为空且有相关配置的情况
name = StandardServletEnvironment.SERVLET_CONFIG_PROPERTY_SOURCE_NAME;
if (servletConfig != null && sources.contains(name) && sources.get(name) instanceof StubPropertySource) {
sources.replace(name, new ServletConfigPropertySource(name, servletConfig));
}
}

在内部调用了WebApplicationContextUtils.initServletPropertySources方法,由名称可得知,它用于初始化Servlet的属性资源,在实际执行过程中分别根据ServletContext和ServletConfig的值来判定是否要将指定的配置包装为ServletContextPropertySource。在实际调试过程中他们的值都为空,也就是没有进行任何操作。

② - 检查必备属性,此处是用于检查哪些属性是必不可少的,例如可以设置"example.address"这个属性必须不为空。

③ - 重新对监听器排序

prepareBeanFactory(beanFactory)

// AbstractApplicationContext.java

protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {

	// 设置类加载器
// Tell the internal bean factory to use the context's class loader etc.
beanFactory.setBeanClassLoader(getClassLoader());
// 设置SpringEL表达式解析器
beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
// 设置属性编辑器注册
beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment())); // ① 忽略指定的接口注入
// Configure the bean factory with context callbacks.
beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
beanFactory.ignoreDependencyInterface(EnvironmentAware.class);
beanFactory.ignoreDependencyInterface(EmbeddedValueResolverAware.class);
beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class);
beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class);
beanFactory.ignoreDependencyInterface(MessageSourceAware.class);
beanFactory.ignoreDependencyInterface(ApplicationContextAware.class); // 指定对特定接口注入时实际的注入对象,例如有某对象想要注入BeanFactory,则实际将会指定它注入的是当前设置的BeanFactory
// BeanFactory interface not registered as resolvable type in a plain factory.
// MessageSource registered (and found for autowiring) as a bean.
beanFactory.registerResolvableDependency(BeanFactory.class, beanFactory);
beanFactory.registerResolvableDependency(ResourceLoader.class, this);
beanFactory.registerResolvableDependency(ApplicationEventPublisher.class, this);
beanFactory.registerResolvableDependency(ApplicationContext.class, this); // 添加和移除ApplicationListener
// Register early post-processor for detecting inner beans as ApplicationListeners.
beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(this)); //
// Detect a LoadTimeWeaver and prepare for weaving, if found.
if (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()));
} // 注册默认环境对象
// Register default environment beans.
if (!beanFactory.containsLocalBean(ENVIRONMENT_BEAN_NAME)) {
beanFactory.registerSingleton(ENVIRONMENT_BEAN_NAME, getEnvironment());
} // 注册系统配置对象
if (!beanFactory.containsLocalBean(SYSTEM_PROPERTIES_BEAN_NAME)) {
beanFactory.registerSingleton(SYSTEM_PROPERTIES_BEAN_NAME, getEnvironment().getSystemProperties());
} // 注册系统环境对象
if (!beanFactory.containsLocalBean(SYSTEM_ENVIRONMENT_BEAN_NAME)) {
beanFactory.registerSingleton(SYSTEM_ENVIRONMENT_BEAN_NAME, getEnvironment().getSystemEnvironment());
}
}

① - 这里的忽略依赖接口,是指这些Aware接口的实现类在Spring中将会自动忽略接口实现类中和setter方法入参相同的类型,举例说明

public interface EnvironmentAware extends Aware {
void setEnvironment(Environment environment);
} public class MyEnvironmentAware implements Environment { private Environment environment; @Overwired
public void setEnvironment(Environment environment) {
this.environment = environment;
} }

示例中展示了如何使用EnvironmentAware接口来实现在自定义代码中获取Environment,上面所说的忽略,是指在Spring自动装配MyEnvironment这个类的时候,会自动忽略到setEnvironment方法中的Environment对象注入。

在忽略接口的第一行代码添加了一个ApplicationContextAwareProcessor,而它则是Spring框架统一来设置这些Aware接口实现类的处理器。

postProcessBeanFactory(beanFactory)

在当前AbstractApplicationContext类中的postProcessBeanFactory方法并未实现,由其子类实现。

// AnnotationConfigServletWebServerApplicationContext.java
// 实现一
protected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {
// ①
super.postProcessBeanFactory(beanFactory);
// ②
if (this.basePackages != null && this.basePackages.length > 0) {
this.scanner.scan(this.basePackages);
}
// ③
if (!this.annotatedClasses.isEmpty()) {
this.reader.register(ClassUtils.toClassArray(this.annotatedClasses));
}
}

① - 调用父类的实现

// ServletWebServerApplicationContext.java

protected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {
// 添加用于处理WebApplicationContextServletContextAware接口的processor
beanFactory.addBeanPostProcessor(new WebApplicationContextServletContextAwareProcessor(this));
// 忽略ServletContextAware接口的注入
beanFactory.ignoreDependencyInterface(ServletContextAware.class);
registerWebApplicationScopes();
} // 注册web应用的作用域
public static void registerWebApplicationScopes(ConfigurableListableBeanFactory beanFactory,
@Nullable ServletContext sc) { beanFactory.registerScope(WebApplicationContext.SCOPE_REQUEST, new RequestScope());
beanFactory.registerScope(WebApplicationContext.SCOPE_SESSION, new SessionScope());
if (sc != null) {
ServletContextScope appScope = new ServletContextScope(sc);
beanFactory.registerScope(WebApplicationContext.SCOPE_APPLICATION, appScope);
// Register as ServletContext attribute, for ContextCleanupListener to detect it.
sc.setAttribute(ServletContextScope.class.getName(), appScope);
} 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);
}
}

② - 根据basePackage指定的位置进行扫描bean

③ - 根据注解来扫描指定的bean

invokeBeanFactoryPostProcessors()

主要用于调用BeanFactoryPostProcessors的实现

protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
// 调用BeanFactoryPostProcessor
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()));
}
}

在调用BeanFactoryPostProcessor时,会首先调用BeanDefinitionRegistryPostProcessor, 因为后者是对前者的扩展,并且有可能在后者中又重新注册了前者的其他实例。由于PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors()方法过长,这里直接写行内注释能够比较

直观的分析前后关系。

public static void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {

	// Invoke BeanDefinitionRegistryPostProcessors first, if any.
// 已处理的Bean
Set<String> processedBeans = new HashSet<>(); // 判断当前的BeanFactory是否为一个Bean注册器,实际上就是代表同时实现了BeanDefinitionRegistryPostProcessor和BeanFactoryPostProcessor接口的实现
// 对于同时实现两个接口的类,将先调用BeanDefinitionRegistryPostProcessor里面的方法,再调用BeanFactoryPostProcessor里面的方法
// 在调用的时候又要区分是实现了PriorityOrdered还是Ordered接口。
if (beanFactory instanceof BeanDefinitionRegistry) { // 转换为注册器
BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
// 用于存放常规的BeanFactoryPostProcessor
List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>();
// 用于存放BeanFactoryPostProcessor的扩展BeanDefinitionRegistryPostProcessor,这里是一个汇总的列表
List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>(); // 遍历传入的BeanFactoryPostProcessor
for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
// 优先执行BeanFactoryPostProcessor的扩展类BeanDefinitionRegistryPostProcessor,它的优先级最高
if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
// 类型转换
BeanDefinitionRegistryPostProcessor registryProcessor = (BeanDefinitionRegistryPostProcessor) postProcessor;
// 调用postProcessBeanDefinitionRegistry()方法,内部可能注册了Bean,也可能重新定义了一些普通的BeanFactoryPostProcessor
registryProcessor.postProcessBeanDefinitionRegistry(registry);
// 添加到已处理列表
registryProcessors.add(registryProcessor);
}
else {
// 对比上面if代码块会发现,这里没有作调用,直接先保存在常规列表内部,因为常规的Processor在调用的时候还有其他考虑,接着往下看便是
regularPostProcessors.add(postProcessor);
}
} // 不要在这里初始化FactoryBean(请看清是FactoryBean,工厂类,不是类工厂(BeanFactory),他们有巨大的差异),需要保留所有的常规类未初始化,以便使用BeanFactoryPostProcessor对其处理
// Do not initialize FactoryBeans here: We need to leave all regular beans
// uninitialized to let the bean factory post-processors apply to them! // 根据BeanDefinitionRegistryPostProcessors 实现的接口划分为三类:实现了PriorityOrdered的、实现了Ordered的以及前面两者都没实现的
// Separate between BeanDefinitionRegistryPostProcessors that implement
// PriorityOrdered, Ordered, and the rest. // 保存当前将要处理的BeanDefinitionRegistryPostProcessor列表,每处理完一种分类的就清空
List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>(); // 首先调用实现了PriorityOrdered接口的BeanDefinitionRegistryPostProcessors
// First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered. // 获取当前Bean工厂内部所有的,类型为BeanDefinitionRegistryPostProcessor.class的后处理器名称
String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false); for (String ppName : postProcessorNames) {
if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
// 筛选出实现了PriorityOrdered接口的后处理器,放入当前处理列表
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
// 同时放入已处理列表
processedBeans.add(ppName);
}
} // 按照优先级排序
sortPostProcessors(currentRegistryProcessors, beanFactory);
// 添加实现了PriorityOrder接口的BeanDefinitionRegistryPostProcessor到它的汇总列表里面
registryProcessors.addAll(currentRegistryProcessors);
// 调用所有的BeanDefinitionRegistryPostProcessor实例的postProcessBeanDefinitionRegistry()方法
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
// 清除内部的实现了PriorityOrder的BeanDefinitionRegistryPostProcessor
currentRegistryProcessors.clear(); // 上面是处理实现了PriorityOrdered接口的,这里处理实现了Ordered接口的, 为何这里又获取了一次postProcessorNames,前面不是才获取么?
// 这里获取一次是因为前面处理的时候有可能又加入了新的BeanDefinitionRegistryPostProcessor
// Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.
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);
// 清空上一步已经执行过的
currentRegistryProcessors.clear(); // 继续调用普通的BeanDefinitionRegistryPostProcessors
// Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear.
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);
currentRegistryProcessors.clear();
} // 最后调用普通的 BeanFactoryPostProcessor,
// Now, invoke the postProcessBeanFactory callback of all processors handled so far.
invokeBeanFactoryPostProcessors(registryProcessors, beanFactory); //因为BeanDefinitionRegistryPostProcessor也是继承了BeanFactoryPostProcessor,,也具有postProcessBeanFactory()方法的,所以也需要执行
invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
} else {
// 若不是BeanDefinitionRegistry,那就是直接实现了BeanFactoryPostProcessor
// Invoke factory processors registered with the context instance.
invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
} // 下面这部分逻辑就和上面套路一样,无非处理的是BeanFactoryPostProcessor罢了
// 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); // Separate between BeanFactoryPostProcessors that implement PriorityOrdered,
// Ordered, and the rest.
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);
}
} // First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.
sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory); // Next, invoke the BeanFactoryPostProcessors that implement Ordered.
List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<>();
for (String postProcessorName : orderedPostProcessorNames) {
orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
}
sortPostProcessors(orderedPostProcessors, beanFactory);
invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory); // Finally, invoke all other BeanFactoryPostProcessors.
List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<>();
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();
}

小结

BeanFactoryPostProcessors是Spring框架中的一个很重要的扩展入口,通过它可以在Bean实例化之前进行一些修改,从类型上分为BeanDefinitionRegistryPostProcessor和BeanFactoryPostProcessor,在内部处理过程中,前者的优先级高于后者。与此同时,他们分别还会按照PriorityOrdered > Ordered > 默认

的优先级顺序来进行处理。了解他们执行顺序这点很重要,后续如有扩展需求就可以精准植入自己的逻辑。需要注意的是,这些处理器本身就是用于注册Bean,因此他们也可以注册和自己类型一样的扩展类。在使用的时候尤其要注意这点。例如在实现了PriorityOrdered的BeanDefinitionRegistryPostProcessor中

再注册一个实现了Ordered的BeanDefinitionRegistryPostProcessor,虽然这样没问题,但笔者认为这样代码隐藏过深。不利于后期维护。建议使用SPI机制来配置,简洁明了。

registerBeanPostProcessors()

主要用于调用BeanPostProcessors的实现,区别于上一个章节,本章节处理的是实例化过后的Bean。

// AbstractApplicationContext.java

protected void registerBeanPostProcessors(ConfigurableListableBeanFactory beanFactory) {
// 调用BeanPostProcessor
PostProcessorRegistrationDelegate.registerBeanPostProcessors(beanFactory, this);
} // PostProcessorRegistrationDelegate.java public static void registerBeanPostProcessors(
ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) { // 获取所有的BeanPostProcessor名称
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. // 注册一个BeanPostProcessorChecker,当一个BeanPostProcessor在实例化期间创建一个Bean的时候,打印日志
int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount)); // 按照优先级整理 // 实现了PriorityOrdered接口的BeanPostProcessor集合
List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
// 内部定义的BeanPostProcessor集合
List<BeanPostProcessor> internalPostProcessors = new ArrayList<>();
// 实现了Ordered接口的BeanPostProcessor名称集合
List<String> orderedPostProcessorNames = new ArrayList<>();
// 未实现排序优先级接口的BeanPostProcessor名称集合
List<String> nonOrderedPostProcessorNames = new ArrayList<>(); // 分别放入不同集合内
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);
}
} // 注册实现了PriorityOrdered接口的BeanPostProcessor
// First, register the BeanPostProcessors that implement PriorityOrdered.
sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors); // 注册实现了PriorityOrdered接口的BeanPostProcessor
// Next, register the BeanPostProcessors that implement Ordered.
List<BeanPostProcessor> orderedPostProcessors = new ArrayList<>();
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); // 注册常规的BeanPostProcessor
// Now, register all regular BeanPostProcessors.
List<BeanPostProcessor> nonOrderedPostProcessors = new ArrayList<>();
for (String ppName : nonOrderedPostProcessorNames) {
BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
nonOrderedPostProcessors.add(pp);
if (pp instanceof MergedBeanDefinitionPostProcessor) {
internalPostProcessors.add(pp);
}
}
registerBeanPostProcessors(beanFactory, nonOrderedPostProcessors); // 重新注册所有的内部BeanPostProcessor
// Finally, re-register all internal BeanPostProcessors.
sortPostProcessors(internalPostProcessors, beanFactory);
registerBeanPostProcessors(beanFactory, internalPostProcessors); // 注册ApplicationListenerDetector,它将在bean初始化完成之后检测是否为ApplicationListener,如果是则加入applicationListeners中
// 在Bean销毁之前,提前从ApplicationEventMulticaster中删除
// Re-register post-processor for detecting inner beans as ApplicationListeners,
// moving it to the end of the processor chain (for picking up proxies etc).
beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
}

initMessageSource()

初始化MessageSource,若当前上下文中未定义,则使用父类中的定义

// AbstractApplicationContext.java

protected void initMessageSource() {
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
if (beanFactory.containsLocalBean(MESSAGE_SOURCE_BEAN_NAME)) {
this.messageSource = beanFactory.getBean(MESSAGE_SOURCE_BEAN_NAME, MessageSource.class);
// Make MessageSource aware of parent MessageSource.
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.
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 + "]");
}
}
}

initApplicationEventMulticaster()

主要用于设置事件发布器,若当前上下文没有定义ApplicationEventMulticaster 则使用 SimpleApplicationEventMulticaster

// AbstractApplicationContext.java

protected void initApplicationEventMulticaster() {
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
if (beanFactory.containsLocalBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME)) {
this.applicationEventMulticaster =
beanFactory.getBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, ApplicationEventMulticaster.class);
if (logger.isTraceEnabled()) {
logger.trace("Using ApplicationEventMulticaster [" + this.applicationEventMulticaster + "]");
}
}
else {
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() + "]");
}
}
}

onRefresh()

当前类中没有实现,只是作为一个模板,将由子类来实现

// AbstractApplicationContext.java

protected void onRefresh() throws BeansException {
// For subclasses: do nothing by default.
} // ServletWebServerApplicationContext.java
protected void onRefresh() {
// 父类中仅仅设置了一下主题,无关紧要
super.onRefresh();
try {
// 创建Web服务器
createWebServer();
}
catch (Throwable ex) {
throw new ApplicationContextException("Unable to start web server", ex);
}
}

创建Web服务器

这里只简单介绍一下它启动了内置的Web容器,Web容器的初始化后续会有单独篇章分析。

private void createWebServer() {
// ①
WebServer webServer = this.webServer;
// ②
ServletContext servletContext = getServletContext();
// ③
if (webServer == null && servletContext == null) {
ServletWebServerFactory factory = getWebServerFactory();
this.webServer = factory.getWebServer(getSelfInitializer());
}
// ④
else if (servletContext != null) {
try {
getSelfInitializer().onStartup(servletContext);
}
catch (ServletException ex) {
throw new ApplicationContextException("Cannot initialize servlet context", ex);
}
}
// ⑤
initPropertySources();
}

① - 当前应用的WEB服务器,也就是Servlet容器。

② - 当前应用的上下文,一个应用使用一个ServletContext来表示。

③ - 使用ServletWebServerFactory创建一个Servlet容器

④ - 手动配置上下文的接口。

⑤ - 初始化配置信息,实际上就是将环境信息中的'servletContextInitParams':StubPropertySource 转换为'servletContextInitParams': ServletContextPropertySource; 将 'servletConfigInitParams': StubPropertySource转换为'servletConfigInitParams':ServletConfigPropertySource

registerListeners()

主要用于将获取到的所有监听器委托给applicationEventMulticaster。

protected void registerListeners() {

	// ①
// Register statically specified listeners first.
for (ApplicationListener<?> listener : getApplicationListeners()) {
getApplicationEventMulticaster().addApplicationListener(listener);
} // ②
// Do not initialize FactoryBeans here: We need to leave all regular beans
// uninitialized to let post-processors apply to them!
String[] listenerBeanNames = getBeanNamesForType(ApplicationListener.class, true, false);
for (String listenerBeanName : listenerBeanNames) {
getApplicationEventMulticaster().addApplicationListenerBean(listenerBeanName);
} // ③
// Publish early application events now that we finally have a multicaster...
Set<ApplicationEvent> earlyEventsToProcess = this.earlyApplicationEvents;
this.earlyApplicationEvents = null;
if (earlyEventsToProcess != null) {
for (ApplicationEvent earlyEvent : earlyEventsToProcess) {
getApplicationEventMulticaster().multicastEvent(earlyEvent);
}
}
}

① - 将内部注册的监听器委托给广播器applicationEventMulticaster。

② - 检测BeanFactory内部的监听器

③ - 发布早期事件

finishBeanFactoryInitialization()

实例化剩下的所有单例Bean(非延迟加载的)

// AbstractApplicationContext.java

protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {

	// ①
// Initialize conversion service for this context.
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));
} // ②
// Register a default embedded value resolver if no bean post-processor
// (such as a PropertyPlaceholderConfigurer bean) registered any before:
// at this point, primarily for resolution in annotation attribute values.
if (!beanFactory.hasEmbeddedValueResolver()) {
beanFactory.addEmbeddedValueResolver(strVal -> getEnvironment().resolvePlaceholders(strVal));
} // ③
// Initialize LoadTimeWeaverAware beans early to allow for registering their transformers early.
String[] weaverAwareNames = beanFactory.getBeanNamesForType(LoadTimeWeaverAware.class, false, false);
for (String weaverAwareName : weaverAwareNames) {
getBean(weaverAwareName);
} // ④
// Stop using the temporary ClassLoader for type matching.
beanFactory.setTempClassLoader(null); // ⑤
// Allow for caching all bean definition metadata, not expecting further changes.
beanFactory.freezeConfiguration(); // ⑤
// Instantiate all remaining (non-lazy-init) singletons.
beanFactory.preInstantiateSingletons();
}

① - 判断是否有转换服务

② - 判断是否有占位符解析器

③ - 注册LoadTimeWeaverAware

④ - 停止使用临时的ClassLoader进行类型匹配,实际上它就是空值

⑤ - 冻结所有的BeanDefinition,通过configurationFrozen = true 和 frozenBeanDefinitionNames(包含所有的BeanDefinition)配合锁定

⑥ - 实例化剩下的所有单例Bean(非延迟加载的),其实就是从注册器缓存里面取出(DefaultSingletonBeanRegistry)

finishRefresh()

// ServletWebServerApplicationContext.java
@Override
protected void finishRefresh() {
// 父类执行finishRefresh
super.finishRefresh();
// 启动web容器
WebServer webServer = startWebServer();
if (webServer != null) {
// 发布web容器启动完成事件
publishEvent(new ServletWebServerInitializedEvent(webServer, this));
}
} // AbstractApplicationContext.java protected void finishRefresh() { // ① Clear context-level resource caches (such as ASM metadata from scanning).
clearResourceCaches(); // ② Initialize lifecycle processor for this context.
initLifecycleProcessor(); // ③ Propagate refresh to lifecycle processor first.
getLifecycleProcessor().onRefresh(); // ④ Publish the final event.
publishEvent(new ContextRefreshedEvent(this)); // ⑤ Participate in LiveBeansView MBean, if active.
LiveBeansView.registerApplicationContext(this);
}

① - 清除资源缓存

② - 初始化上下文生命周期

③ - 传播刷新动作至生命周期

④ - 发布上下文刷新完毕事件

⑤ - 构建当前Bean及其依赖关系的快照,设计用于Spring Tool Suite

resetCommonCaches()

主要用于清除Spring内部的缓存

// AbstractApplicationContext.java

protected void resetCommonCaches() {
ReflectionUtils.clearCache();
AnnotationUtils.clearCache();
ResolvableType.clearCache();
CachedIntrospectionResults.clearClassLoader(getClassLoader());
}

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