SpringBoot启动分析4：准备并刷新环境

在前面的环境准备完毕后，后续就是创建上下文环境、准备上下文环境以及刷新上下文环境了。

创建上下文环境

上下文环境的创建，虽然源码是以父类来视人，实际它实例化的是AnnotationConfigServletWebServerApplicationContext对象：

context = createApplicationContext();
protected ConfigurableApplicationContext createApplicationContext() {
	Class<?> contextClass = this.applicationContextClass;
	if (contextClass == null) {
		try {
			switch (this.webApplicationType) {
			case SERVLET:
				contextClass = Class.forName(DEFAULT_SERVLET_WEB_CONTEXT_CLASS);
				break;
			case REACTIVE:
				contextClass = Class.forName(DEFAULT_REACTIVE_WEB_CONTEXT_CLASS);
				break;
			default:
				contextClass = Class.forName(DEFAULT_CONTEXT_CLASS);
			}
		}
		catch (ClassNotFoundException ex) {
			throw new IllegalStateException("Unable create a default ApplicationContext, please specify an ApplicationContextClass", ex);
		}
	}
	return (ConfigurableApplicationContext) BeanUtils.instantiateClass(contextClass);
}

还记得初始化SpringApplication时webApplicationType就是初始化为SERVLET，所以这里创建的是以下实例：

public static final String DEFAULT_SERVLET_WEB_CONTEXT_CLASS = "org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext";

最后通过工具类实例化该类，以下是上下文环境的类图：

准备上下文环境

创建完成上下文环境对象后，开始对这环境初始化，跟进源码：

// 参数：上下文环境对象、环境对象、发布时间的监听器、命令行参数、打印对象
prepareContext(context, environment, listeners, applicationArguments, printedBanner);
private void prepareContext(ConfigurableApplicationContext context, ConfigurableEnvironment environment,SpringApplicationRunListeners listeners, ApplicationArguments applicationArguments, Banner printedBanner) {
	context.setEnvironment(environment);
	postProcessApplicationContext(context);
	applyInitializers(context);
	listeners.contextPrepared(context);
	if (this.logStartupInfo) {
		logStartupInfo(context.getParent() == null);
		logStartupProfileInfo(context);
	}
	// Add boot specific singleton beans
	ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();
	beanFactory.registerSingleton("springApplicationArguments", applicationArguments);
	if (printedBanner != null) {
		beanFactory.registerSingleton("springBootBanner", printedBanner);
	}
	if (beanFactory instanceof DefaultListableBeanFactory) {
		((DefaultListableBeanFactory) beanFactory)
				.setAllowBeanDefinitionOverriding(this.allowBeanDefinitionOverriding);
	}
	if (this.lazyInitialization) {
		context.addBeanFactoryPostProcessor(new LazyInitializationBeanFactoryPostProcessor());
	}
	// Load the sources
	Set<Object> sources = getAllSources();
	Assert.notEmpty(sources, "Sources must not be empty");
	load(context, sources.toArray(new Object[0]));
	listeners.contextLoaded(context);
}

设置上下文的环境信息

context.setEnvironment(environment);
public class AnnotationConfigServletWebServerApplicationContext extends ServletWebServerApplicationContext implements AnnotationConfigRegistry {
	private final AnnotatedBeanDefinitionReader reader;
	private final ClassPathBeanDefinitionScanner scanner;
	
	@Override
	public void setEnvironment(ConfigurableEnvironment environment) {
		super.setEnvironment(environment);
		this.reader.setEnvironment(environment);
		this.scanner.setEnvironment(environment);
	}
}

设置转换格式器

protected void postProcessApplicationContext(ConfigurableApplicationContext context) {
	// beanNameGenerator尚未初始化,这里为null
	if (this.beanNameGenerator != null) {
		context.getBeanFactory().registerSingleton(AnnotationConfigUtils.CONFIGURATION_BEAN_NAME_GENERATOR,
				this.beanNameGenerator);
	}
	// resourceLoader尚未初始化,这里为null
	if (this.resourceLoader != null) {
		if (context instanceof GenericApplicationContext) {
			((GenericApplicationContext) context).setResourceLoader(this.resourceLoader);
		}
		if (context instanceof DefaultResourceLoader) {
			((DefaultResourceLoader) context).setClassLoader(this.resourceLoader.getClassLoader());
		}
	}
	// addConversionService默认为true,所以将格式转换器添加到BeanFactory中
	if (this.addConversionService) {
		context.getBeanFactory().setConversionService(ApplicationConversionService.getSharedInstance());
	}
}