Spring上下文ApplicationContext接口，初始化实现在AbstractApplicationContext中
初始化流程：
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) { //线程安全
// Prepare this context for refreshing.
prepareRefresh();//初始化标记值和Environment
// Tell the subclass to refresh the internal bean factory.
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory(); //初始化BeanFactory并扫描BeanDefinitions
// Prepare the bean factory for use in this context.
prepareBeanFactory(beanFactory);//为BeanFactory初始化属性值，并且添加各种回调处理器，如ApplicationAware等
try {
// Allows post-processing of the bean factory in context subclasses.
postProcessBeanFactory(beanFactory);//初始化BeanFactory后ApplicationContext自定义操作
// Invoke factory processors registered as beans in the context.
invokeBeanFactoryPostProcessors(beanFactory);//调用BeanFactoryPostProcessor，先调用BeanDefinitionRegistryPostProcessor，按PriorityOrdered->Ordered->None顺序调用，而后调用BeanFactoryPostProcessor，顺序与前面相同
// Register bean processors that intercept bean creation.
registerBeanPostProcessors(beanFactory);//注册BeanPostProcessor，当BeanFactory.createBean被调用时，会依次调用BeanPostProcessor
// Initialize message source for this context.
initMessageSource();//若存在自定义MessageSource则用，否则取空
// Initialize event multicaster for this context.
initApplicationEventMulticaster();//初始化应用事件多点推送
// Initialize other special beans in specific context subclasses.
onRefresh();//自定义刷新上下文操作
// Check for listener beans and register them.
registerListeners();//注册应用事件
// Instantiate all remaining (non-lazy-init) singletons.
finishBeanFactoryInitialization(beanFactory);//初始化非lazy-init单例对象
// Last step: publish corresponding event.
finishRefresh();//发布刷新完成事件
}
}
}
具体逻辑:
1.prepareRefresh方法，主要作用:初始化各标记值，初始化Environment，从配置的propertySources读取配置
2.obtainFreshBeanFactory方法：获取新的BeanFactory，即初始化BeanFactory，refreshBeanFactory方法由具体类实现，在AbstractRefeshableApplicationContext中，将会扫描BeanDefinition
3.prepareBeanFactory方法，向BeanFactory中添加初始化必须的属性及Bean，如自动装配处理器、资源自动注入处理器、各种默认回调接口处理
4.自定义BeanFactory初始化后操作，添加BeanPostProcessor处理器ServletContextAwareProcessor
5.调用之前注册的BeanFactoryPostProcessor，实质上调用PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessor方法
(1)getBeanFactoryPostProcessor()方法获取默认上下文BeanFactoryProcessor列表
(2)invokeBeanFactoryPostProcessor方法调用，先调用所有BeanDefinitionRegistryPostProcessor对BeanDefinition操作，而后对所有由ApplicationContext.addPostProcessor方法添加的BeanFactoryPostProcessor执行postBeanFactory操作
a)BeanFactoryPostProcessor分类成常规和Registry
b)从BeanDefinitions中获取BeanDefinitionRegistryPostProcessor类型，如果实现PriorityOrdered接口表明属于优先级排序的PostProcessor，排序后加入到registryPostProcessors中，优先调用
c)调用实现自Ordered接口的BeanDefinitionRegistryPostProcessor实现
d) 调用所有BeanDefinitionRegistryPostProcessor实现，及BeanFactoryPostProcessor方法
e)获取所有实现BeanFactoryPostProcessor接口的BeanDefinition，与以上逻辑相同，先处理实现PriorityOrdered->Ordered->none顺序处理
6.注册BeanPostProcessor至BeanFactory中，当BeanFactory.createBean方法被调用时，会先按顺序调用所有BeanPostProcessor
a)扫描BeanDefinition中所有BeanPostProcessor接口实现类，先添加BeanPostProcessorChecker，用于打印日志
b)按照PriorityOrdered>Ordered>NonOrder顺序对BeanPostProcessor进行分类
c)排序后将其加入到BeanFactory中，最后添加ApplicationListenerDetecter用于发现ApplicationListener，将其添加到上下文ApplicationContext中
7.初始化MessageSource
a)若BeanDefinitions中包含MessageSource，则将其注入到ApplicationContext中
b)若无自定义MessageSource，则默认采用空MessageSource
8.初始化应用事件多点传送，若包含自定义Bean则取自定义Bean，否则取SimpleApplicationEventMulticaster，用于向应用监听器发送事件
9.刷新操作，由子类自定义实现
10.注册Listener到ApplicationEventMutilcaster
11.初始化非lazy-init的单例对象
12.发布完成刷新事件
