上篇给大家介绍了Spring Boot启动过程完全解析(一)，大家可以点击参考下
该说refreshContext(context)了，首先是判断context是否是AbstractApplicationContext派生类的实例，之后调用了强转为AbstractApplicationContext类型并调用它的refresh方法。由于AnnotationConfigEmbeddedWebApplicationContext继承自EmbeddedWebApplicationContext，所以会执行EmbeddedWebApplicationContext的refresh方法，继而执行其中的super.refresh。这个refresh也就是AbstractApplicationContext的refresh方法了，它内部是一个synchronized锁全局的代码块，同样的加锁方法还有这个类里的close和registerShutdownHook方法。
同步代码块中第一个方法prepareRefresh，首先会执行AnnotationConfigEmbeddedWebApplicationContext的prepareRefresh方法：
protected void prepareRefresh() {
this.scanner.clearCache();
super.prepareRefresh();
}
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这个super也就是AbstractApplicationContext，它的prepareRefresh方法逻辑是：生成启动时间；设置closed状态为false；active状态为true；initPropertySources方法主要是调用了AbstractEnvironment的getPropertySources方法获取了之前SpringApplication的prepareEnvironment方法中getOrCreateEnvironment方法准备的各种环境变量及配置并用于初始化ServletPropertySources。具体的servletContextInitParams这些是在环境对象初始化时由各集成级别Environment的customizePropertySources方法中初始化的。
接着的getEnvironment().validateRequiredProperties()方法实际执行了AbstractEnvironment中的this.propertyResolver.validateRequiredProperties()，主要是验证了被占位的key如果是required的值不能为null。prepareRefresh的最后是初始化this.earlyApplicationEvents = new LinkedHashSet<ApplicationEvent>()。*****
只够是获取BeanFactory实例的方法obtainFreshBeanFactory()，首先在refreshBeanFactory方法中用原子布尔类型判断是否刷新过，BeanFactory实例是在createApplicationContext创建Context实例时被创建的，如果没有刷新则设置一个用于序列化的id，id是ContextIdApplicationContextInitializer初始化设置的（如未配置该初始化器，是有一个默认ObjectUtils.identityToString(this)生成的），这个id的生成规则是spring.config.name截取的+":"+server.port的占位截取。设置序列化id时，同时保存了一个id和弱引用DefaultListableBeanFactory实例映射。
得到了beanFactory后就是prepareBeanFactory(beanFactory)了，逻辑是注册了BeanClassLoader用于注入的bean实例的创建；StandardBeanExpressionResolver用于EL表达式，比如配置文件或者@Value("#{...}")等使用；用ResourceEditorRegistrar注册属性转换器，比如xml配置的bean属性都是用的字符串配置的要转成真正的属性类型；addBeanPostProcessor(new ApplicationContextAwareProcessor(this))注册ApplicationContextAwareProcessor，它的invokeAwareInterfaces方法会对实现指定接口的bean调用指定的set方法；ignoreDependencyInterface忽略对这些接口的自动装配，比如Aware这些是要做独立处理的，不适合通用的方法；然后是有几个类型直接手动注册，比如BeanFactory，这个很好理解；接着注册一个后置处理器ApplicationListenerDetector的实例，addBeanPostProcessor注册的会按照注册先后顺序执行；这个方法的最后判断了特定的4个bean名字，如果存在会做相应注册，包括loadTimeWeaver、environment、systemProperties和systemEnvironment。补充一点，在最开始创建实例的时候还执行过ignoreDependencyInterface(BeanNameAware.class);ignoreDependencyInterface(BeanFactoryAware.class);ignoreDependencyInterface(BeanClassLoaderAware.class)。
protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
// Tell the internal bean factory to use the context's class loader etc.
beanFactory.setBeanClassLoader(getClassLoader());
beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));
// 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);
// 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);
// 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()));
}
// Register default environment beans.
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());
}
}
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之后到了refresh的postProcessBeanFactory方法，首先是会走到AnnotationConfigEmbeddedWebApplicationContext的Override，需要注意的一点是，这是web环境，如果不是是不会加载这个上下文的，也就不会这么走。它重写的第一步是先走super也就是EmbeddedWebApplicationContext的postProcessBeanFactory，这里又注册了个后置处理器WebApplicationContextServletContextAwareProcessor的实例，构造参数是this，也就是当前上下文，同时忽略ServletContextAware接口，这个接口是用于获取ServletContext的，为什么要忽略呢，我猜应该是因为我们既然有了web应用并且内嵌servlet的上下文实例，还要ServletContext的实现就没什么用了，还有可能出现冲突的问题，有空我再确认下。然后是配置的basePackages和annotatedClasses：
@Override
protected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {
super.postProcessBeanFactory(beanFactory);
if (this.basePackages != null && this.basePackages.length > 0) {
this.scanner.scan(this.basePackages);
}
if (this.annotatedClasses != null && this.annotatedClasses.length > 0) {
this.reader.register(this.annotatedClasses);
}
}
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到了invokeBeanFactoryPostProcessors方法，这个方法就是执行之前注册的BeanFactory后置处理器的地方。代码一目了然，PostProcessorRegistrationDelegate的invokeBeanFactoryPostProcessors中只是有些排序的逻辑，我就不说了：
/**
* Instantiate and invoke all registered BeanFactoryPostProcessor beans,
* respecting explicit order if given.
* <p>Must be called before singleton instantiation.
*/
protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors());
// Detect a LoadTimeWeaver and prepare for weaving, if found in the meantime
// (