1 实例化SpringApplication
SpringApplication.run(BootifulApplication.class, args);
public static ConfigurableApplicationContext run(Class<?> primarySource,String... args) {return run(new Class<?>[] { primarySource }, args);}
public static ConfigurableApplicationContext run(Class<?>[] primarySources,String[] args) {return new SpringApplication(primarySources).run(args); //new SpringApplication}
public SpringApplication(Class<?>... primarySources) {this(null, primarySources);}
public SpringApplication(ResourceLoader resourceLoader, Class<?>... primarySources) {//设置资源加载器为nullthis.resourceLoader = resourceLoader;//断言加载资源类不能为nullAssert.notNull(primarySources, "PrimarySources must not be null");//将primarySources数组转换为List，最后放到LinkedHashSet集合中this.primarySources = new LinkedHashSet<>(Arrays.asList(primarySources));//【1.1 推断当前应用类型是否为WEB】this.webApplicationType = WebApplicationType.deduceFromClasspath();//【1.2 设置应用上下文初始化器】setInitializers((Collection) getSpringFactoriesInstances(ApplicationContextInitializer.class));//【1.3 设置监听器】setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));//【1.4 推断应用的入口类】this.mainApplicationClass = deduceMainApplicationClass();}
1.1 推断当前应用类型是否为WEB
根据classpath下的内容推断出应用的类型
this.webApplicationType = WebApplicationType.deduceFromClasspath();
static WebApplicationType deduceFromClasspath() {if (ClassUtils.isPresent(WEBFLUX_INDICATOR_CLASS, null)&& !ClassUtils.isPresent(WEBMVC_INDICATOR_CLASS, null)&& !ClassUtils.isPresent(JERSEY_INDICATOR_CLASS, null)) {return WebApplicationType.REACTIVE;}for (String className : SERVLET_INDICATOR_CLASSES) {if (!ClassUtils.isPresent(className, null)) {return WebApplicationType.NONE;}}return WebApplicationType.SERVLET;}
1.2 设置应用上下文初始化器
setInitializers((Collection)getSpringFactoriesInstances(ApplicationContextInitializer.class));
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ApplicationContextInitializer
public interface ApplicationContextInitializer<C extends ConfigurableApplicationContext> {/*** Initialize the given application context.* @param applicationContext the application to configure*/void initialize(C applicationContext);}
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getSpringFactoriesInstances(ApplicationContextInitializer.class)
private <T> Collection<T> getSpringFactoriesInstances(Class<T> type) {return getSpringFactoriesInstances(type, new Class<?>[] {});}
private <T> Collection<T> getSpringFactoriesInstances(Class<T> type,Class<?>[] parameterTypes, Object... args) {//获取当前上下文类加载器ClassLoader classLoader = getClassLoader();// Use names and ensure unique to protect against duplicates//获取ApplicationContextInitializer实例名称并且去重Set<String> names = new LinkedHashSet<>(//进入loadFactoryNames方法并且找到loadSpringFactories---spring.factoriesSpringFactoriesLoader.loadFactoryNames(type, classLoader));//创建初始化器实例列表List<T> instances = createSpringFactoriesInstances(type, parameterTypes,classLoader, args, names);//排序AnnotationAwareOrderComparator.sort(instances);return instances;}
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setInitializers(...)
初始化一个ApplicationContextInitializer
public void setInitializers(Collection<? extends ApplicationContextInitializer<?>> initializers) {this.initializers = new ArrayList<>();this.initializers.addAll(initializers);}
1.3 设置监听器
setListeners((Collection)getSpringFactoriesInstances(ApplicationListener.class));
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ApplicationListener
public interface ApplicationListener<E extends ApplicationEvent> extends EventListener {/*** Handle an application event.* @param event the event to respond to*/void onApplicationEvent(E event);}
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getSpringFactoriesInstances(ApplicationListener.class)
private <T> Collection<T> getSpringFactoriesInstances(Class<T> type) {return getSpringFactoriesInstances(type, new Class<?>[] {});}
private <T> Collection<T> getSpringFactoriesInstances(Class<T> type,Class<?>[] parameterTypes, Object... args) {//获取当前上下文类加载器ClassLoader classLoader = getClassLoader();// Use names and ensure unique to protect against duplicates//获取ApplicationContextInitializer实例名称并且去重Set<String> names = new LinkedHashSet<>(//进入loadFactoryNames方法并且找到loadSpringFactories---spring.factoriesSpringFactoriesLoader.loadFactoryNames(type, classLoader));List<T> instances = createSpringFactoriesInstances(type, parameterTypes,classLoader, args, names);//创建初始化器实例列表AnnotationAwareOrderComparator.sort(instances);//排序return instances;}
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setListeners(...)
初始化一个ApplicationListener
public void setListeners(Collection<? extends ApplicationListener<?>> listeners) {this.listeners = new ArrayList<>();this.listeners.addAll(listeners);}
1.4 推断应用的入口类
this.mainApplicationClass = deduceMainApplicationClass();private Class<?> deduceMainApplicationClass() {try {//构造一个运行时异常，遍历异常栈中的方法名，获取方法名为main的栈帧，得到入口类的名字再返回该类StackTraceElement[] stackTrace = new RuntimeException().getStackTrace();for (StackTraceElement stackTraceElement : stackTrace) {if ("main".equals(stackTraceElement.getMethodName())) {return Class.forName(stackTraceElement.getClassName());}}}catch (ClassNotFoundException ex) {// Swallow and continue}return null;}
2 调用run方法
/*** Run the Spring application, creating and refreshing a new* {@link ApplicationContext}.* @param args the application arguments (usually passed from a Java main method)* @return a running {@link ApplicationContext}*/public ConfigurableApplicationContext run(String... args) {//创建计时类StopWatch stopWatch = new StopWatch();stopWatch.start();//初始化应用上下文和异常报告集合ConfigurableApplicationContext context = null;Collection<SpringBootExceptionReporter> exceptionReporters = new ArrayList<>();//设置headless属性configureHeadlessProperty();//【2.1 创建运行监听器】SpringApplicationRunListeners listeners = getRunListeners(args);//发布应用启动事件listeners.starting();try {//初始化默认应用参数类ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);//【2.2 根据监听器和应用参数类准备Spring环境】ConfigurableEnvironment environment = prepareEnvironment(listeners,applicationArguments);configureIgnoreBeanInfo(environment);//创建Banner打印类Banner printedBanner = printBanner(environment);//【2.3 创建应用上下文】context = createApplicationContext();//准备异常报告exceptionReporters = getSpringFactoriesInstances(SpringBootExceptionReporter.class,new Class[] { ConfigurableApplicationContext.class }, context);//【2.4 准备应用上下文】prepareContext(context, environment, listeners, applicationArguments,printedBanner);//【2.5 刷新应用上下文】refreshContext(context);//应用上下文后置处理刷新afterRefresh(context, applicationArguments);//停止计时类stopWatch.stop();//输出日志记录执行主类名、时间信息if (this.logStartupInfo) {new StartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(), stopWatch);}//发布应用上下文启动完成事件listeners.started(context);//【2.6 执行Runner运行器】callRunners(context, applicationArguments);}catch (Throwable ex) {handleRunFailure(context, ex, exceptionReporters, listeners);throw new IllegalStateException(ex);}try {//发布应用上下文就绪事件listeners.running(context);}catch (Throwable ex) {handleRunFailure(context, ex, exceptionReporters, null);throw new IllegalStateException(ex);}//返回应用上下文return context;}
2.1 创建运行监听器
SpringApplicationRunListeners listeners = getRunListeners(args);
private SpringApplicationRunListeners getRunListeners(String[] args) {Class<?>[] types = new Class<?>[] { SpringApplication.class, String[].class };return new SpringApplicationRunListeners(logger, getSpringFactoriesInstances(SpringApplicationRunListener.class, types, this, args));}
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SpringApplicationRunListener
org.springframework.boot:spring-boot/META-INF/spring.factories
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getSpringFactoriesInstances(...)
private <T> Collection<T> getSpringFactoriesInstances(Class<T> type,Class<?>[] parameterTypes, Object... args) {ClassLoader classLoader = getClassLoader();// Use names and ensure unique to protect against duplicatesSet<String> names = new LinkedHashSet<>(SpringFactoriesLoader.loadFactoryNames(type, classLoader));List<T> instances = createSpringFactoriesInstances(type, parameterTypes,classLoader, args, names);AnnotationAwareOrderComparator.sort(instances);return instances;}
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new SpringApplicationRunListeners(...)
SpringApplicationRunListeners(Log log,Collection<? extends SpringApplicationRunListener> listeners) {this.log = log;this.listeners = new ArrayList<>(listeners);}
2.2 根据监听器和应用参数类准备Spring环境
ConfigurableEnvironment environment = prepareEnvironment(listeners, applicationArguments);
private ConfigurableEnvironment prepareEnvironment(SpringApplicationRunListeners listeners,ApplicationArguments applicationArguments) {// Create and configure the environment//获取应用环境(3种情况)ConfigurableEnvironment environment = getOrCreateEnvironment();//配置应用环境configureEnvironment(environment, applicationArguments.getSourceArgs());listeners.environmentPrepared(environment);bindToSpringApplication(environment);if (!this.isCustomEnvironment) {environment = new EnvironmentConverter(getClassLoader()).convertEnvironmentIfNecessary(environment, deduceEnvironmentClass());}ConfigurationPropertySources.attach(environment);return environment;}
2.3 创建应用上下文
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);}
2.4 准备应用上下文
prepareContext(context, environment, listeners, applicationArguments, printedBanner);
private void prepareContext(ConfigurableApplicationContext context,ConfigurableEnvironment environment, SpringApplicationRunListeners listeners,ApplicationArguments applicationArguments, Banner printedBanner) {//绑定环境到上下文context.setEnvironment(environment);//配置上下文的bean生成器和资源加载器postProcessApplicationContext(context);//为上下文采用所有初始化器applyInitializers(context);//触发监听器的contextPrepared事件listeners.contextPrepared(context);//记录启动日志if (this.logStartupInfo) {logStartupInfo(context.getParent() == null);logStartupProfileInfo(context);}// Add boot specific singleton beans//注册两个特殊的单例BeanConfigurableListableBeanFactory beanFactory = context.getBeanFactory();beanFactory.registerSingleton("springApplicationArguments", applicationArguments);if (printedBanner != null) {beanFactory.registerSingleton("springBootBanner", printedBanner);}if (beanFactory instanceof DefaultListableBeanFactory) {((DefaultListableBeanFactory) beanFactory).setAllowBeanDefinitionOverriding(this.allowBeanDefinitionOverriding);}// Load the sources//加载所有资源Set<Object> sources = getAllSources();Assert.notEmpty(sources, "Sources must not be empty");load(context, sources.toArray(new Object[0]));//触发监听器的contextLoaded事件listeners.contextLoaded(context);}
2.5 刷新应用上下文
refreshContext(context);
private void refreshContext(ConfigurableApplicationContext context) {refresh(context); //--->进入该方法if (this.registerShutdownHook) {try {context.registerShutdownHook();}catch (AccessControlException ex) {// Not allowed in some environments.}}}
protected void refresh(ApplicationContext applicationContext) {Assert.isInstanceOf(AbstractApplicationContext.class, applicationContext);((AbstractApplicationContext) applicationContext).refresh(); //--->进入该方法}
public void refresh() throws BeansException, IllegalStateException {synchronized (this.startupShutdownMonitor) {// Prepare this context for refreshing.//context：启动日期|设置context当前状态|初始化环境|验证必须prepareRefresh();// Tell the subclass to refresh the internal bean factory.//刷新内部bean工厂，即创建一个bean工厂(对BeanDefinition的定义、解析、处理和注册)ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();// Prepare the bean factory for use in this context.//上面创建好了之后，还需要配置一些东西才能使用prepareBeanFactory(beanFactory);try {// Allows post-processing of the bean factory in context subclasses.//注册WEB特性的scope(如request，session等)postProcessBeanFactory(beanFactory);// Invoke factory processors registered as beans in the context.//调用所有的bean工厂处理器对bean进行一些处理invokeBeanFactoryPostProcessors(beanFactory);// Register bean processors that intercept bean creation.//注册用来拦截beanregisterBeanPostProcessors(beanFactory);// Initialize message source for this context.//主要用于国际化initMessageSource();// Initialize event multicaster for this context.//为context初始化一个事件广播器initApplicationEventMulticaster();// Initialize other special beans in specific context subclasses./*在AbstractApplicationContext的子类中初始化其他特殊的bean。其实就是初始化ThemeSource接口的实例。这个方法需要在所有单例bean初始化之前调用。*/onRefresh();// Check for listener beans and register them.//注册应用监听器registerListeners();// Instantiate all remaining (non-lazy-init) singletons.//完成对bean工厂初始化工作finishBeanFactoryInitialization(beanFactory);// Last step: publish corresponding event.//调用LifecycleProcessor的onRefresh()方法并且发布事件finishRefresh();}catch (BeansException ex) {if (logger.isWarnEnabled()) {logger.warn("Exception encountered during context initialization - " +"cancelling refresh attempt: " + ex);}// Destroy already created singletons to avoid dangling resources.destroyBeans();// Reset 'active' flag.cancelRefresh(ex);// Propagate exception to caller.throw ex;}finally {// Reset common introspection caches in Spring's core, since we// might not ever need metadata for singleton beans anymore...resetCommonCaches();}}}
2.6 执行Runner运行器
callRunners(context, applicationArguments);
执行所有ApplicationRunner和CommandLineRunner两种运行器private void callRunners(ApplicationContext context, ApplicationArguments args) {
List<Object> runners = new ArrayList<>();runners.addAll(context.getBeansOfType(ApplicationRunner.class).values());runners.addAll(context.getBeansOfType(CommandLineRunner.class).values());AnnotationAwareOrderComparator.sort(runners);for (Object runner : new LinkedHashSet<>(runners)) {if (runner instanceof ApplicationRunner) {callRunner((ApplicationRunner) runner, args);}if (runner instanceof CommandLineRunner) {callRunner((CommandLineRunner) runner, args);}}}