Spring上下文ApplicationContext接口，初始化實現在AbstractApplicationContext中
初始化流程：
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) { //線程安全
// Prepare this context for refreshing.
prepareRefresh();//初始化標記值和Environment
// Tell the subclass to refresh the internal bean factory.
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory(); //初始化BeanFactory並掃描BeanDefinitions
// Prepare the bean factory for use in this context.
prepareBeanFactory(beanFactory);//為BeanFactory初始化屬性值，並且添加各種回調處理器，如ApplicationAware等
try {
// Allows post-processing of the bean factory in context subclasses.
postProcessBeanFactory(beanFactory);//初始化BeanFactory后ApplicationContext自定義操作
// Invoke factory processors registered as beans in the context.
invokeBeanFactoryPostProcessors(beanFactory);//調用BeanFactoryPostProcessor，先調用BeanDefinitionRegistryPostProcessor，按PriorityOrdered->Ordered->None順序調用，而后調用BeanFactoryPostProcessor，順序與前面相同
// Register bean processors that intercept bean creation.
registerBeanPostProcessors(beanFactory);//注冊BeanPostProcessor，當BeanFactory.createBean被調用時，會依次調用BeanPostProcessor
// Initialize message source for this context.
initMessageSource();//若存在自定義MessageSource則用，否則取空
// Initialize event multicaster for this context.
initApplicationEventMulticaster();//初始化應用事件多點推送
// Initialize other special beans in specific context subclasses.
onRefresh();//自定義刷新上下文操作
// Check for listener beans and register them.
registerListeners();//注冊應用事件
// Instantiate all remaining (non-lazy-init) singletons.
finishBeanFactoryInitialization(beanFactory);//初始化非lazy-init單例對象
// Last step: publish corresponding event.
finishRefresh();//發布刷新完成事件
}
}
}
具體邏輯:
1.prepareRefresh方法，主要作用:初始化各標記值，初始化Environment，從配置的propertySources讀取配置
2.obtainFreshBeanFactory方法：獲取新的BeanFactory，即初始化BeanFactory，refreshBeanFactory方法由具體類實現，在AbstractRefeshableApplicationContext中，將會掃描BeanDefinition
3.prepareBeanFactory方法，向BeanFactory中添加初始化必須的屬性及Bean，如自動裝配處理器、資源自動注入處理器、各種默認回調接口處理
4.自定義BeanFactory初始化后操作，添加BeanPostProcessor處理器ServletContextAwareProcessor
5.調用之前注冊的BeanFactoryPostProcessor，實質上調用PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessor方法
(1)getBeanFactoryPostProcessor()方法獲取默認上下文BeanFactoryProcessor列表
(2)invokeBeanFactoryPostProcessor方法調用，先調用所有BeanDefinitionRegistryPostProcessor對BeanDefinition操作，而后對所有由ApplicationContext.addPostProcessor方法添加的BeanFactoryPostProcessor執行postBeanFactory操作
a)BeanFactoryPostProcessor分類成常規和Registry
b)從BeanDefinitions中獲取BeanDefinitionRegistryPostProcessor類型，如果實現PriorityOrdered接口表明屬於優先級排序的PostProcessor，排序后加入到registryPostProcessors中，優先調用
c)調用實現自Ordered接口的BeanDefinitionRegistryPostProcessor實現
d) 調用所有BeanDefinitionRegistryPostProcessor實現，及BeanFactoryPostProcessor方法
e)獲取所有實現BeanFactoryPostProcessor接口的BeanDefinition，與以上邏輯相同，先處理實現PriorityOrdered->Ordered->none順序處理
6.注冊BeanPostProcessor至BeanFactory中，當BeanFactory.createBean方法被調用時，會先按順序調用所有BeanPostProcessor
a)掃描BeanDefinition中所有BeanPostProcessor接口實現類，先添加BeanPostProcessorChecker，用於打印日志
b)按照PriorityOrdered>Ordered>NonOrder順序對BeanPostProcessor進行分類
c)排序后將其加入到BeanFactory中，最后添加ApplicationListenerDetecter用於發現ApplicationListener，將其添加到上下文ApplicationContext中
7.初始化MessageSource
a)若BeanDefinitions中包含MessageSource，則將其注入到ApplicationContext中
b)若無自定義MessageSource，則默認采用空MessageSource
8.初始化應用事件多點傳送，若包含自定義Bean則取自定義Bean，否則取SimpleApplicationEventMulticaster，用於向應用監聽器發送事件
9.刷新操作，由子類自定義實現
10.注冊Listener到ApplicationEventMutilcaster
11.初始化非lazy-init的單例對象
12.發布完成刷新事件
