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6、根据运行监听器和应用参数来准备 Spring 环境
private ConfigurableEnvironment prepareEnvironment(SpringApplicationRunListeners listeners,ApplicationArguments applicationArguments) {// Create and configure the environmentConfigurableEnvironment environment = getOrCreateEnvironment();configureEnvironment(environment, applicationArguments.getSourceArgs());listeners.environmentPrepared(environment);bindToSpringApplication(environment);if (!this.isCustomEnvironment) {environment = new EnvironmentConverter(getClassLoader()).convertEnvironmentIfNecessary(environment, deduceEnvironmentClass());}ConfigurationPropertySources.attach(environment);return environment;}getOrCreateEnvironment初始化运行环境 this.webApplicationType=SERVLET 在前面讲过会在SpringApplication初始化赋值，所以运行环境是StandardServletEnvironment
private ConfigurableEnvironment getOrCreateEnvironment() {if (this.environment != null) {return this.environment;}switch (this.webApplicationType) {case SERVLET:return new StandardServletEnvironment();case REACTIVE:return new StandardReactiveWebEnvironment();default:return new StandardEnvironment();}}listeners.environmentPrepared(environment);发布org.springframework.boot.context.event.ApplicationEnvironmentPreparedEvent事件 见（ApplicationStartingEvent）事件 不在赘述
ConfigFileApplicationListener该类赋值读取文件
private void onApplicationEnvironmentPreparedEvent(ApplicationEnvironmentPreparedEvent event) {List<EnvironmentPostProcessor> postProcessors = loadPostProcessors();postProcessors.add(this);AnnotationAwareOrderComparator.sort(postProcessors);for (EnvironmentPostProcessor postProcessor : postProcessors) {postProcessor.postProcessEnvironment(event.getEnvironment(),event.getSpringApplication());}}postProcessors.add(this);将自己也加入list中，循环调用postProcessEnvironment方法，先只看ConfigFileApplicationListener类的
Loader内部类将this.propertySourceLoaders 赋值
org.springframework.boot.env.PropertySourceLoader=\
org.springframework.boot.env.PropertiesPropertySourceLoader,\
org.springframework.boot.env.YamlPropertySourceLoader
循环加载器获取文件，注意在加载EnvironmentPostProcessor实现类是有顺序的，也就是说后面的属性会覆盖前面文件的属性，还记得postProcessors.add(this)么，也就是说最后才会加载ConfigFileApplicationListener，将本项目中的配置文件替换前面配置文件的属性，然后在看下本项目的加载依次的顺序如下：
1.PropertiesPropertySourceLoader "properties", "xml" 2.YamlPropertySourceLoader "yml", "yaml"
private void load(String location, String name, Profile profile,DocumentFilterFactory filterFactory, DocumentConsumer consumer) {if (!StringUtils.hasText(name)) {for (PropertySourceLoader loader : this.propertySourceLoaders) {if (canLoadFileExtension(loader, location)) {load(loader, location, profile,filterFactory.getDocumentFilter(profile), consumer);return;}}}Set<String> processed = new HashSet<>();for (PropertySourceLoader loader : this.propertySourceLoaders) {for (String fileExtension : loader.getFileExtensions()) {if (processed.add(fileExtension)) {loadForFileExtension(loader, location + name, "." + fileExtension,profile, filterFactory, consumer);}}}}获取文件内容load方法 并赋值addActiveProfiles、addIncludedProfiles
private void load(PropertySourceLoader loader, String location, Profile profile,DocumentFilter filter, DocumentConsumer consumer) {try {Resource resource = this.resourceLoader.getResource(location);if (resource == null || !resource.exists()) {if (this.logger.isTraceEnabled()) {StringBuilder description = getDescription("Skipped missing config ", location, resource, profile);this.logger.trace(description);}return;}if (!StringUtils.hasText(StringUtils.getFilenameExtension(resource.getFilename()))) {if (this.logger.isTraceEnabled()) {StringBuilder description = getDescription("Skipped empty config extension ", location, resource,profile);this.logger.trace(description);}return;}String name = "applicationConfig: [" + location + "]";List<Document> documents = loadDocuments(loader, name, resource);if (CollectionUtils.isEmpty(documents)) {if (this.logger.isTraceEnabled()) {StringBuilder description = getDescription("Skipped unloaded config ", location, resource, profile);this.logger.trace(description);}return;}List<Document> loaded = new ArrayList<>();for (Document document : documents) {if (filter.match(document)) {addActiveProfiles(document.getActiveProfiles());addIncludedProfiles(document.getIncludeProfiles());loaded.add(document);}}Collections.reverse(loaded);if (!loaded.isEmpty()) {loaded.forEach((document) -> consumer.accept(profile, document));if (this.logger.isDebugEnabled()) {StringBuilder description = getDescription("Loaded config file ",location, resource, profile);this.logger.debug(description);}}}catch (Exception ex) {throw new IllegalStateException("Failed to load property "+ "source from location '" + location + "'", ex);}}loadDocuments(loader, name, resource);会将文件的属性加载项目中来
7、创建 Banner 打印类
默认打印SpringBootBanner类 看下这个图片是不是很熟悉呢
class SpringBootBanner implements Banner {private static final String[] BANNER = { ""," . ____ _ __ _ _"," /\\\\ / ___'_ __ _ _(_)_ __ __ _ \\ \\ \\ \\","( ( )\\___ | '_ | '_| | '_ \\/ _` | \\ \\ \\ \\"," \\\\/ ___)| |_)| | | | | || (_| | ) ) ) )"," ' |____| .__|_| |_|_| |_\\__, | / / / /"," =========|_|==============|___/=/_/_/_/" };
8、创建应用上下文
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);}容器实际上就是AnnotationConfigServletWebServerApplicationContext类，后面的操作都会基于此类
AnnotationConfigServletWebServerApplicationContext在实例化时还会加载许多类，构造方法
public AnnotationConfigServletWebServerApplicationContext() {this.reader = new AnnotatedBeanDefinitionReader(this);this.scanner = new ClassPathBeanDefinitionScanner(this);}进行跟进AnnotatedBeanDefinitionReader构造方法，加载
internalConfigurationAnnotationProcessor，internalConfigurationBeanNameGenerator、internalAutowiredAnnotationProcessor等类，这也是为什么类名与实际类名称不同，前面多个internal的原因
public static Set<BeanDefinitionHolder> registerAnnotationConfigProcessors(BeanDefinitionRegistry registry, @Nullable Object source) {DefaultListableBeanFactory beanFactory = unwrapDefaultListableBeanFactory(registry);if (beanFactory != null) {if (!(beanFactory.getDependencyComparator() instanceof AnnotationAwareOrderComparator)) {beanFactory.setDependencyComparator(AnnotationAwareOrderComparator.INSTANCE);}if (!(beanFactory.getAutowireCandidateResolver() instanceof ContextAnnotationAutowireCandidateResolver)) {beanFactory.setAutowireCandidateResolver(new ContextAnnotationAutowireCandidateResolver());}}Set<BeanDefinitionHolder> beanDefs = new LinkedHashSet<>(8);if (!registry.containsBeanDefinition(CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME)) {RootBeanDefinition def = new RootBeanDefinition(ConfigurationClassPostProcessor.class);def.setSource(source);beanDefs.add(registerPostProcessor(registry, def, CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME));}if (!registry.containsBeanDefinition(AUTOWIRED_ANNOTATION_PROCESSOR_BEAN_NAME)) {RootBeanDefinition def = new RootBeanDefinition(AutowiredAnnotationBeanPostProcessor.class);def.setSource(source);beanDefs.add(registerPostProcessor(registry, def, AUTOWIRED_ANNOTATION_PROCESSOR_BEAN_NAME));}// Check for JSR-250 support, and if present add the CommonAnnotationBeanPostProcessor.if (jsr250Present && !registry.containsBeanDefinition(COMMON_ANNOTATION_PROCESSOR_BEAN_NAME)) {RootBeanDefinition def = new RootBeanDefinition(CommonAnnotationBeanPostProcessor.class);def.setSource(source);beanDefs.add(registerPostProcessor(registry, def, COMMON_ANNOTATION_PROCESSOR_BEAN_NAME));}// Check for JPA support, and if present add the PersistenceAnnotationBeanPostProcessor.if (jpaPresent && !registry.containsBeanDefinition(PERSISTENCE_ANNOTATION_PROCESSOR_BEAN_NAME)) {RootBeanDefinition def = new RootBeanDefinition();try {def.setBeanClass(ClassUtils.forName(PERSISTENCE_ANNOTATION_PROCESSOR_CLASS_NAME,AnnotationConfigUtils.class.getClassLoader()));}catch (ClassNotFoundException ex) {throw new IllegalStateException("Cannot load optional framework class: " + PERSISTENCE_ANNOTATION_PROCESSOR_CLASS_NAME, ex);}def.setSource(source);beanDefs.add(registerPostProcessor(registry, def, PERSISTENCE_ANNOTATION_PROCESSOR_BEAN_NAME));}if (!registry.containsBeanDefinition(EVENT_LISTENER_PROCESSOR_BEAN_NAME)) {RootBeanDefinition def = new RootBeanDefinition(EventListenerMethodProcessor.class);def.setSource(source);beanDefs.add(registerPostProcessor(registry, def, EVENT_LISTENER_PROCESSOR_BEAN_NAME));}if (!registry.containsBeanDefinition(EVENT_LISTENER_FACTORY_BEAN_NAME)) {RootBeanDefinition def = new RootBeanDefinition(DefaultEventListenerFactory.class);def.setSource(source);beanDefs.add(registerPostProcessor(registry, def, EVENT_LISTENER_FACTORY_BEAN_NAME));}return beanDefs;}
9、准备异常报告器
exceptionReporters 还是一样读取spring.factory文件赋值实例化
org.springframework.boot.SpringBootExceptionReporter=\
org.springframework.boot.diagnostics.FailureAnalyzers
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