一、程序入口
1.1、静态方法
//直接调用run方法ConfigurableApplicationContext context = SpringApplication.run(App.class, args);
内部实现：
public static ConfigurableApplicationContext run(Object source, String... args) { return run(new Object[] { source }, args); } 查看run
public static ConfigurableApplicationContext run(Object[] sources, String[] args) { return new SpringApplication(sources).run(args); } 故等效于实例化，后调用。同1.2
1.2、实例化SpringApplication，调用run方法
//实例化SpringApplication然后调用run方法 SpringApplication application = new SpringApplication(App.class); ConfigurableApplicationContext context = application.run(args);
查看实现
public SpringApplication(Object... sources) { initialize(sources); } 查看initialize
@SuppressWarnings({ "unchecked", "rawtypes" }) private void initialize(Object[] sources) { if (sources != null && sources.length > 0) { this.sources.addAll(Arrays.asList(sources)); } this.webEnvironment = deduceWebEnvironment(); setInitializers((Collection) getSpringFactoriesInstances( ApplicationContextInitializer.class)); setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class)); this.mainApplicationClass = deduceMainApplicationClass(); } 二、运行流程分析
2.1、【new SpringApplication(App.class);初始化】
1、将source添加到set：中：this.sources.addAll(Arrays.asList(sources));
2、判断是不是web环境this.webEnvironment = deduceWebEnvironment();
private boolean deduceWebEnvironment() { for (String className : WEB_ENVIRONMENT_CLASSES) { if (!ClassUtils.isPresent(className, null)) { return false; } } return true; } 内部
private static final String[] WEB_ENVIRONMENT_CLASSES = { "javax.servlet.Servlet","org.springframework.web.context.ConfigurableWebApplicationContext" }; 3、加载所有classpath下面的META-INF/spring.factoriesd的ApplicationContextInitializer, getSpringFactoriesInstances(ApplicationContextInitializer.class)
将所有的ApplicationContextInitializer放置到：private List<ApplicationContextInitializer<?>> initializers;中：
setInitializers((Collection) getSpringFactoriesInstances(ApplicationContextInitializer.class));
4、listener同3一致
加载所有classpath下面的META-INF/spring.factories的ApplicationListener, getSpringFactoriesInstances(ApplicationListener.class)
将所有的ApplicationListener放置到：private List<ApplicationListener<?>> listeners;中：setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));
5、推断main方法所在的类
是this.mainApplicationClass = deduceMainApplicationClass();
2.2、【run方法】
6、开始执行run方法
public ConfigurableApplicationContext run(String... args) { StopWatch stopWatch = new StopWatch(); stopWatch.start(); ConfigurableApplicationContext context = null; FailureAnalyzers analyzers = null; configureHeadlessProperty(); SpringApplicationRunListeners listeners = getRunListeners(args); listeners.starting(); try { ApplicationArguments applicationArguments = new DefaultApplicationArguments( args); ConfigurableEnvironment environment = prepareEnvironment(listeners, applicationArguments); Banner printedBanner = printBanner(environment); context = createApplicationContext(); analyzers = new FailureAnalyzers(context); prepareContext(context, environment, listeners, applicationArguments, printedBanner); refreshContext(context); afterRefresh(context, applicationArguments); listeners.finished(context, null); stopWatch.stop(); if (this.logStartupInfo) { new StartupInfoLogger(this.mainApplicationClass) .logStarted(getApplicationLog(), stopWatch); } return context; } catch (Throwable ex) { handleRunFailure(context, listeners, analyzers, ex); throw new IllegalStateException(ex); } } 时间监视器
StopWatch stopWatch = new StopWatch();stopWatch.start();stopWatch.stop();
7、设置java.awt.headless系统变量
ConfigurableApplicationContext context = null;configureHeadlessProperty();
注意：新增FailureAnalyzers analyzers = null;
是为了失败分析调试时使用
FailureAnalyzers analyzers = null;analyzers = new FailureAnalyzers(context);
8、加载所有classpath下面的META-INF/spring.factories，SpringApplicationRunListeners
执行所有SpringApplicationRunListeners的所有started方法
SpringApplicationRunListeners listeners = getRunListeners(args); listeners.starting();
作用：SpringApplicationRunListeners是Springboot扩展点。
用来在执行过程中，不同的时间点来进行发送事件通知的。
9、实例化ApplicationArguments参数
ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
10、创建ConfigurableEnvironment
ConfigurableEnvironment environment = prepareEnvironment(listeners,applicationArguments);
内部
private ConfigurableEnvironment prepareEnvironment( SpringApplicationRunListeners listeners, ApplicationArguments applicationArguments) { // Create and configure the environment ConfigurableEnvironment environment = getOrCreateEnvironment(); configureEnvironment(environment, applicationArguments.getSourceArgs()); listeners.environmentPrepared(environment); if (!this.webEnvironment) { environment = new EnvironmentConverter(getClassLoader()) .convertToStandardEnvironmentIfNecessary(environment); } return environment; } 创建：ConfigurableEnvironment environment = getOrCreateEnvironment();
配置：configureEnvironment(environment, applicationArguments.getSourceArgs());
主要是把run方法的参数配置到environment
监听：listeners.environmentPrepared(environment);
执行所有SpringApplicationRunListeners的所有environmentPrepared方法
非web环境转换
if (!this.webEnvironment) { environment = new EnvironmentConverter(getClassLoader()) .convertToStandardEnvironmentIfNecessary(environment); } 11、打印Banner：Banner printedBanner = printBanner(environment);
12、创建ConfigurableApplicationContext：context = createApplicationContext();
protected ConfigurableApplicationContext createApplicationContext() { Class contextClass = this.applicationContextClass; if (contextClass == null) { try { contextClass = Class.forName(this.webEnvironment ? DEFAULT_WEB_CONTEXT_CLASS : DEFAULT_CONTEXT_CLASS); } catch (ClassNotFoundException ex) { throw new IllegalStateException( "Unable create a default ApplicationContext, " + "please specify an ApplicationContextClass", ex); } } return (ConfigurableApplicationContext) BeanUtils.instantiate(contextClass); } 如果是WEB环境，实例化：org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext
否则实例化：org.springframework.context.annotation.AnnotationConfigApplicationContext
13、准备context：prepareContext(context, environment, listeners, applicationArguments,printedBanner);
内部
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 context.getBeanFactory().registerSingleton("springApplicationArguments", applicationArguments); if (printedBanner != null) { context.getBeanFactory().registerSingleton("springBootBanner", printedBanner); } // Load the sources Set a、设置setEnvironment
b、后置调用：postProcessApplicationContext(context);
protected void postProcessApplicationContext(ConfigurableApplicationContext context) { if (this.beanNameGenerator != null) { context.getBeanFactory().registerSingleton( AnnotationConfigUtils.CONFIGURATION_BEAN_NAME_GENERATOR, this.beanNameGenerator); } if (this.resourceLoader != null) { if (context instanceof GenericApplicationContext) { ((GenericApplicationContext) context) .setResourceLoader(this.resourceLoader); } if (context instanceof DefaultResourceLoader) { ((DefaultResourceLoader) context) .setClassLoader(this.resourceLoader.getClassLoader()); } } } 如果beanNameGenerator不为空，就把beanNameGenerator对象注入到context里面去，、
同样如果resourceLoader不为空，就设置：setResourceLoader、setClassLoader
c、回调所有的ApplicationContextInitializer：applyInitializers
@SuppressWarnings({ "rawtypes", "unchecked" }) protected void applyInitializers(ConfigurableApplicationContext context) { for (ApplicationContextInitializer initializer : getInitializers()) { Class requiredType = GenericTypeResolver.resolveTypeArgument( initializer.getClass(), ApplicationContextInitializer.class); Assert.isInstanceOf(requiredType, context, "Unable to call initializer."); initializer.initialize(context); } } d、执行所有SpringApplicationRunListeners的contextPrepared方法：listeners.contextPrepared(context);
e、日志输出
f、依次向Spring容器中注入springApplicationArguments、Banners对象
context.getBeanFactory().registerSingleton("springApplicationArguments", applicationArguments); if (printedBanner != null) { context.getBeanFactory().registerSingleton("springBootBanner", printedBanner); } g、将所有的source加载到context中，类似于初始化一个AnnotationConfigApplicationContext然后将所有的容器注入
Set
h、执行所有SpringApplicationRunListeners的contextLoaded方法：listeners.contextLoaded(context);
14、执行refreshContext(context);方法，并且判断调用registerShutdownHook
private void refreshContext(ConfigurableApplicationContext context) { refresh(context); if (this.registerShutdownHook) { try { context.registerShutdownHook(); } catch (AccessControlException ex) { // Not allowed in some environments. } } } 15、afterRefresh(context, applicationArguments);回调，获取容器中所有的ApplicationRunner、CommandLineRunner接口，然后排序，依次调用
protected void afterRefresh(ConfigurableApplicationContext context, ApplicationArguments args) { callRunners(context, args); } private void callRunners(ApplicationContext context, ApplicationArguments args) { List 16、执行所有SpringApplicationRunListeners的finished方法：listeners.finished(context, null);;
17、结束，如果出现问题将使用日志handleRunFailure