版本信息

Spring Boot 2.5.4

启动的两步

  1. 启动类上注解：@SpringBootApplication
  2. 启动类中的main方法：org.springframework.boot.SpringApplication#run(java.lang.Class<?>, java.lang.String…)

本篇只记录第二步，第一步见SpringBoot | SpringBoot中的注解-SpringBoot启动篇。

SpringBoot的启动流程图解

SpringBoot | SpringBoot的启动流程 - 图1

源码执行流程解析

  1. @SpringBootApplication
  2. @MapperScan(basePackages = {"com.ybqdren.mapper"} ) 
  3. @ComponentScan(basePackages = {"com.ybqdren","org.n3r.idworker"})
  4. public class Application {
  5.     public static void main(String[] args){
  6.         SpringApplication.run(Application.class,args);
  7.     }
  8. }

进入 EventPublishingRunListener#EventPublishingRunListener：
image.png
不过这里目前没有监听器。

进入 SpringApplication#run：

  1. public static ConfigurableApplicationContext run(Class<?> primarySource, String... args) {
  2.     return run(new Class<?>[] { primarySource }, args);
  3. }

调用另一个同名的重载方法 SpringApplication#run。

进入 SpringApplication#run，创建一个SpringApplication的实例对象：

  1. public static ConfigurableApplicationContext run(Class<?>[] primarySources, String[] args) {
  2.     return new SpringApplication(primarySources).run(args);
  3. }

进入其构造方法 SpringApplicaion#SpringApplication。

进入 SpringApplicaion#SpringApplication：

  1. @SuppressWarnings({ "unchecked", "rawtypes" })
  2. public SpringApplication(ResourceLoader resourceLoader, Class<?>... primarySources) {
  3.   this.resourceLoader = resourceLoader;
  4.   Assert.notNull(primarySources, "PrimarySources must not be null");
  5.   this.primarySources = new LinkedHashSet<>(Arrays.asList(primarySources));
  6.   // 初始化了webApplicationType ，比如此处是“SERVLET”  
  7.   this.webApplicationType = WebApplicationType.deduceFromClasspath();
  8.   setInitializers((Collection) getSpringFactoriesInstances(
  9.     ApplicationContextInitializer.class));
  10.   // 初始化了几个listener监听器，比如此处是 8 个   
  11.   setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));
  12.   this.mainApplicationClass = deduceMainApplicationClass();
  13. }

上面这个过程，主要是初始化成员变量.

比如应用类型（比如此处 webApplicationType 值为SERVLET）：
image.png

比如初始化监听器：
image.png

比如通过 SpringApplicaion#getBootstrapRegistryInitializersFromSpringFactories 初始化了：
SpringBoot | SpringBoot的启动流程 - 图5

比如通过 SpringApplicaion#getSpringFactoriesInstances(ApplicationContextInitializer.class) 初始化了：
SpringBoot | SpringBoot的启动流程 - 图6

进入 SpringApplication#run：

  1. public ConfigurableApplicationContext run(String... args) {
  2.     StopWatch stopWatch = new StopWatch();
  3.     stopWatch.start();
  4.     DefaultBootstrapContext bootstrapContext = createBootstrapContext();
  5.     ConfigurableApplicationContext context = null;
  6.     configureHeadlessProperty();
  7.     SpringApplicationRunListeners listeners = getRunListeners(args);
  8.     listeners.starting(bootstrapContext, this.mainApplicationClass);
  9.     try {
  10.         ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
  11.         ConfigurableEnvironment environment = prepareEnvironment(listeners, bootstrapContext, applicationArguments);
  12.         configureIgnoreBeanInfo(environment);
  13.         Banner printedBanner = printBanner(environment);
  14.         context = createApplicationContext();
  15.         context.setApplicationStartup(this.applicationStartup);
  16.         prepareContext(bootstrapContext, context, environment, listeners, applicationArguments, printedBanner);
  17.         refreshContext(context);
  18.         afterRefresh(context, applicationArguments);
  19.         stopWatch.stop();
  21.         // 如果 logStartupInfo 为 true 就输出类似下面这样的日志：
  22.         // INFO  Application:61 - Started Application in 93.379 seconds (JVM running for 112.224)
  23.         if (this.logStartupInfo) {
  24.             new StartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(), stopWatch);
  25.         }
  26.         listeners.started(context);
  27.         callRunners(context, applicationArguments);
  28.     }
  29.     catch (Throwable ex) {
  30.         handleRunFailure(context, ex, listeners);
  31.         throw new IllegalStateException(ex);
  32.     }
  34.     try {
  35.         listeners.running(context);
  36.     }
  37.     catch (Throwable ex) {
  38.         handleRunFailure(context, ex, null);
  39.         throw new IllegalStateException(ex);
  40.     }
  41.     return context;
  42. }

此处是使用了观察者模式。

  1. 创建一个 StopWatch 实例，用来记录 Spring Boot 的启动时间

image.png

  1. 通过 SpringFactoriesLoader 加载 listeners

通过 SpringFactoriesLoader#loadFactoryNames 方法从核心配置文件中获取到了org.springframework.boot.SpringApplicationRunListener ：
image.png
而其只有一个实现类 EventPublishingRunListener：
image.png
所以此处会加载 EventPublishingRunListener 这个监听器。

  1. 发布 Sprint Boot 开始启动事件

进入 EventPublishingRunListener#starting 开启事件：

  1. @Override
  2. public void starting(ConfigurableBootstrapContext bootstrapContext) {
  3.     this.initialMulticaster
  4.         .multicastEvent(new ApplicationStartingEvent(bootstrapContext, this.application, this.args));
  5. }
  1. 创建和配置environment

进入 EventPublishingRunListener#environmentPrepared 配置各种配置参数：

  1. @Override
  2. public void environmentPrepared(ConfigurableBootstrapContext bootstrapContext,
  3.                                 ConfigurableEnvironment environment) {
  4.     this.initialMulticaster.multicastEvent(
  5.         new ApplicationEnvironmentPreparedEvent(bootstrapContext, this.application, this.args, environment));
  6. }

比如：
interface org.springframework.boot.env.EnvironmentPostProcessor
interface org.springframework.boot.context.config.ConfigDataLocationResolver
interface org.springframework.boot.env.PropertySourceLoader
interface org.springframework.boot.context.config.ConfigDataLoader

  1. 打印SpringBoot的banner和版本（可能还会打印一些环境的版本信息）

image.png
image.png

  1. 创建对应的ApplicationContext：Web类型

进入 ApplicationContextFactory：
image.png

返回 SERVLET 。

Reactive类型，普通的类型(非Web)

  1. prepareContext

进入 SpringApplication#prepareContext：

  1. private void prepareContext(DefaultBootstrapContext bootstrapContext, ConfigurableApplicationContext context,
  2.                             ConfigurableEnvironment environment, SpringApplicationRunListeners listeners,
  3.                             ApplicationArguments applicationArguments, Banner printedBanner) {
  4.     context.setEnvironment(environment);
  5.     postProcessApplicationContext(context);
  6.     applyInitializers(context);
  7.     listeners.contextPrepared(context);
  8.     bootstrapContext.close(context);
  9.     if (this.logStartupInfo) {
  10.         logStartupInfo(context.getParent() == null);
  11.         logStartupProfileInfo(context);
  12.     }
  13.     // Add boot specific singleton beans
  14.     ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();
  15.     beanFactory.registerSingleton("springApplicationArguments", applicationArguments);
  16.     if (printedBanner != null) {
  17.         beanFactory.registerSingleton("springBootBanner", printedBanner);
  18.     }
  19.     if (beanFactory instanceof DefaultListableBeanFactory) {
  20.         ((DefaultListableBeanFactory) beanFactory)
  21.         .setAllowBeanDefinitionOverriding(this.allowBeanDefinitionOverriding);
  22.     }
  23.     if (this.lazyInitialization) {
  24.         context.addBeanFactoryPostProcessor(new LazyInitializationBeanFactoryPostProcessor());
  25.     }
  26.     // Load the sources
  27.     Set<Object> sources = getAllSources();
  28.     Assert.notEmpty(sources, "Sources must not be empty");
  29.     load(context, sources.toArray(new Object[0]));
  30.     listeners.contextLoaded(context);
  31. }

1) 准备ApplicationContext，通过 EventPublishingRunListener#contextPrepared 初始化；
image.png

2) 打印启动日志，打印profile信息(如dev, test, prod)
调用 SpringApplication#logStartupInfo方法，在控制台打印：
image.png
调用 SpringApplication#logStartupProfileInfo方法，在控制台打印：
image.png

3) 最终会调用到AbstractApplicationContext#refresh方法，实际上就是Spring IOC容器的创建过程，并且会进行自动装配的操作，以及发布ApplicationContext已经refresh事件，标志着ApplicationContext初始化完成(contextLoaded())
此处的日志输出：

  1. INFO  TomcatWebServer:108 - Tomcat initialized with port(s): 8088 (http)
  2. 12月 11, 2021 6:19:01 下午 org.apache.catalina.core.StandardService startInternal
  3. 信息: Starting service [Tomcat]
  4. 12月 11, 2021 6:19:01 下午 org.apache.catalina.core.StandardEngine startInternal
  5. 信息: Starting Servlet engine: [Apache Tomcat/9.0.52]
  6. 12月 11, 2021 6:19:01 下午 org.apache.catalina.core.ApplicationContext log
  7. 信息: Initializing Spring embedded WebApplicationContext
  8. INFO  ServletWebServerApplicationContext:290 - Root WebApplicationContext: initialization completed in 1603 ms
  9. Logging initialized using 'class org.apache.ibatis.logging.stdout.StdOutImpl' adapter.
  10. Parsed mapper file: 'file [D:\Zhao\Code\CourseCode\Java技术专家\code\architectural-evolution-of-Java-applications-learn\foodie-dev\foodie-dev-mapper\target\classes\mapper\CarouselMapper.xml]'
  11. Parsed mapper file: 'file [D:\Zhao\Code\CourseCode\Java技术专家\code\architectural-evolution-of-Java-applications-learn\foodie-dev\foodie-dev-mapper\target\classes\mapper\CategoryMapper.xml]'
  12. Parsed mapper file: 'file [D:\Zhao\Code\CourseCode\Java技术专家\code\architectural-evolution-of-Java-applications-learn\foodie-dev\foodie-dev-mapper\target\classes\mapper\CategoryMapperCustom.xml]'
  13. Parsed mapper file: 'file [D:\Zhao\Code\CourseCode\Java技术专家\code\architectural-evolution-of-Java-applications-learn\foodie-dev\foodie-dev-mapper\target\classes\mapper\ItemsCommentsMapper.xml]'
  14. Parsed mapper file: 'file [D:\Zhao\Code\CourseCode\Java技术专家\code\architectural-evolution-of-Java-applications-learn\foodie-dev\foodie-dev-mapper\target\classes\mapper\ItemsImgMapper.xml]'
  15. Parsed mapper file: 'file [D:\Zhao\Code\CourseCode\Java技术专家\code\architectural-evolution-of-Java-applications-learn\foodie-dev\foodie-dev-mapper\target\classes\mapper\ItemsMapper.xml]'
  16. Parsed mapper file: 'file [D:\Zhao\Code\CourseCode\Java技术专家\code\architectural-evolution-of-Java-applications-learn\foodie-dev\foodie-dev-mapper\target\classes\mapper\ItemsMapperCustom.xml]'
  17. Parsed mapper file: 'file [D:\Zhao\Code\CourseCode\Java技术专家\code\architectural-evolution-of-Java-applications-learn\foodie-dev\foodie-dev-mapper\target\classes\mapper\ItemsParamMapper.xml]'
  18. Parsed mapper file: 'file [D:\Zhao\Code\CourseCode\Java技术专家\code\architectural-evolution-of-Java-applications-learn\foodie-dev\foodie-dev-mapper\target\classes\mapper\ItemsSpecMapper.xml]'
  19. Parsed mapper file: 'file [D:\Zhao\Code\CourseCode\Java技术专家\code\architectural-evolution-of-Java-applications-learn\foodie-dev\foodie-dev-mapper\target\classes\mapper\OrderItemsMapper.xml]'
  20. Parsed mapper file: 'file [D:\Zhao\Code\CourseCode\Java技术专家\code\architectural-evolution-of-Java-applications-learn\foodie-dev\foodie-dev-mapper\target\classes\mapper\OrderStatusMapper.xml]'
  21. Parsed mapper file: 'file [D:\Zhao\Code\CourseCode\Java技术专家\code\architectural-evolution-of-Java-applications-learn\foodie-dev\foodie-dev-mapper\target\classes\mapper\OrdersMapper.xml]'
  22. Parsed mapper file: 'file [D:\Zhao\Code\CourseCode\Java技术专家\code\architectural-evolution-of-Java-applications-learn\foodie-dev\foodie-dev-mapper\target\classes\mapper\StuMapper.xml]'
  23. Parsed mapper file: 'file [D:\Zhao\Code\CourseCode\Java技术专家\code\architectural-evolution-of-Java-applications-learn\foodie-dev\foodie-dev-mapper\target\classes\mapper\UserAddressMapper.xml]'
  24. Parsed mapper file: 'file [D:\Zhao\Code\CourseCode\Java技术专家\code\architectural-evolution-of-Java-applications-learn\foodie-dev\foodie-dev-mapper\target\classes\mapper\UsersMapper.xml]'
  25. INFO  MapperCacheDisabler:60 - Clear tk.mybatis.mapper.util.MsUtil CLASS_CACHE cache.
  26. INFO  MapperCacheDisabler:60 - Clear tk.mybatis.mapper.genid.GenIdUtil CACHE cache.
  27. INFO  MapperCacheDisabler:60 - Clear tk.mybatis.mapper.version.VersionUtil CACHE cache.
  28. INFO  MapperCacheDisabler:83 - Clear EntityHelper entityTableMap cache.
  29. Logging initialized using 'class org.apache.ibatis.logging.stdout.StdOutImpl' adapter.
  30. INFO  TomcatWebServer:220 - Tomcat started on port(s): 8088 (http) with context path ''
  31. INFO  DocumentationPluginsBootstrapper:84 - Context refreshed
  32. INFO  DocumentationPluginsBootstrapper:87 - Found 1 custom documentation plugin(s)
  33. INFO  ApiListingReferenceScanner:44 - Scanning for api listing references
  34. INFO  CachingOperationNameGenerator:40 - Generating unique operation named: updateUsingPOST_1
  35. INFO  CachingOperationNameGenerator:40 - Generating unique operation named: userinfoUsingGET_1
  36. INFO  CachingOperationNameGenerator:40 - Generating unique operation named: setSessionUsingGET_1
  37. INFO  CachingOperationNameGenerator:40 - Generating unique operation named: searchUsingGET_1
  38. INFO  CachingOperationNameGenerator:40 - Generating unique operation named: sixNewItemsUsingGET_1
  39. INFO  CachingOperationNameGenerator:40 - Generating unique operation named: addUsingPOST_1
  1. afterRefresh hook方法

作用是刷新上下文后调用，在当前版本中，此方法没有实现？？
image.png

  1. stopWatch停止计时，日志打印总共启动的时间

image.png

  1. 发布SpringBoot程序已启动事件

进入 EventPublishingRunListener#started 方法：

  1. @Override
  2. public void started(ConfigurableApplicationContext context) {
  3.     context.publishEvent(new ApplicationStartedEvent(this.application, this.args, context));
  4.     AvailabilityChangeEvent.publish(context, LivenessState.CORRECT);
  5. }

image.png

  1. 调用ApplicationRunner和CommandLineRunner

SpringApplication#callRunners

  1. private void callRunners(ApplicationContext context, ApplicationArguments args) {
  2.     List<Object> runners = new ArrayList<>();
  3.     runners.addAll(context.getBeansOfType(ApplicationRunner.class).values());
  4.     runners.addAll(context.getBeansOfType(CommandLineRunner.class).values());
  5.     AnnotationAwareOrderComparator.sort(runners);
  6.     for (Object runner : new LinkedHashSet<>(runners)) {
  7.         if (runner instanceof ApplicationRunner) {
  8.             callRunner((ApplicationRunner) runner, args);
  9.         }
  10.         if (runner instanceof CommandLineRunner) {
  11.             callRunner((CommandLineRunner) runner, args);
  12.         }
  13.     }
  14. }
  1. 最后发布就绪事件ApplicationReadyEvent，标志着SpringBoot可以处理就收的请求了

进入 EventPublishingRunListener#running 方法：

  1. @Override
  2. public void running(ConfigurableApplicationContext context) {
  3.     context.publishEvent(new ApplicationReadyEvent(this.application, this.args, context));
  4.     AvailabilityChangeEvent.publish(context, ReadinessState.ACCEPTING_TRAFFIC);
  5. }

相关方法与作用解析

SpringApplicaion::SpringApplication

SpringApplicaion#getSpringFactoriesInstances

  1. private <T> Collection<T> getSpringFactoriesInstances(Class<T> type, Class<?>[] parameterTypes, Object... args) {
  2.   ClassLoader classLoader = getClassLoader();
  3.   // Use names and ensure unique to protect against duplicates
  4.   Set<String> names = new LinkedHashSet<>(SpringFactoriesLoader.loadFactoryNames(type, classLoader));
  5.   List<T> instances = createSpringFactoriesInstances(type, parameterTypes, classLoader, args, names);
  6.   AnnotationAwareOrderComparator.sort(instances);
  7.   return instances;
  8. }

  • SpringFactoriesLoader#loadFactoryNames

    1. public static List<String> loadFactoryNames(Class<?> factoryType, @Nullable ClassLoader classLoader) {
    2. ClassLoader classLoaderToUse = classLoader;
    3. if (classLoader == null) {
    4.   classLoaderToUse = SpringFactoriesLoader.class.getClassLoader();
    5. }
    7. String factoryTypeName = factoryType.getName();
    8. return (List)loadSpringFactories(classLoaderToUse).getOrDefault(factoryTypeName, Collections.emptyList());
    9. }

    到 SpringFactoriesLoader#loadSpringFactories中获取，此方法使用classloader的双亲委派机制：
    image.png

从spring.factories中获取type对应的配置类名称列表：
image.png
此文件位于对应包的META-INF文件夹下：
image.png
image.png

  • SpringFactoriesLoader#createSpringFactoriesInstances
    1. @SuppressWarnings("unchecked")
    2. private <T> List<T> createSpringFactoriesInstances(Class<T> type, Class<?>[] parameterTypes,
    3.                                                  ClassLoader classLoader, Object[] args, Set<String> names) {
    4.   List<T> instances = new ArrayList<>(names.size());
    5.   for (String name : names) {
    6.       try {
    7.           Class<?> instanceClass = ClassUtils.forName(name, classLoader);
    8.           Assert.isAssignable(type, instanceClass);
    9.           Constructor<?> constructor = instanceClass.getDeclaredConstructor(parameterTypes);
    10.           T instance = (T) BeanUtils.instantiateClass(constructor, args);
    11.           instances.add(instance);
    12.       }
    13.       catch (Throwable ex) {
    14.           throw new IllegalArgumentException("Cannot instantiate " + type + " : " + name, ex);
    15.       }
    16.   }
    17.   return instances;
    18. }
    校验获取到的类是否是parameterTypes类的子类，并将获取到的类通过反射机制实例化。

AbstractApplicationContext#refresh

  1. /**
  2.      * Refresh the underlying {@link ApplicationContext}.
  3.      * @param applicationContext the application context to refresh
  4.      */
  5. protected void refresh(ConfigurableApplicationContext applicationContext) {
  6.     applicationContext.refresh();
  7. }

进入 ServletWebServerApplicationContext#refresh ：

  1. @Override
  2. public final void refresh() throws BeansException, IllegalStateException {
  3.     try {
  4.         super.refresh();
  5.     }
  6.     catch (RuntimeException ex) {
  7.         WebServer webServer = this.webServer;
  8.         if (webServer != null) {
  9.             webServer.stop();
  10.         }
  11.         throw ex;
  12.     }
  13. }

创建的过程（AnnotationConfigApplicationContext的构造方法），由于debug过这个源码，我个人把它分为两大步（暂时我先写出我的总结，后续看是否有时间能写一篇关于debug的过程）：

  1. 给我们的Bean，创建与之对应的BeanDefinition，然后把他们放入ConcurrentHashMap（key:beanName和value:beanDefinition）中；BeanDefinition实际上包括一些Bean的信息，比如BeanName, Scope, 是否被@Primary注解修饰，是否是@Lazy，以及@Description等注解
  2. refresh()方法： 创建IOC需要的资源
  • 初始化BeanFactory, set一些属性，如BeanClassLoader，systemEnvironment
  • 如果是SpringBoot程序，会调用方法进行自动装配：AutoConfigurationImportSelector.AutoConfigurationGroup#process，见：@EnableAutoConfiguration的总结
  • 注册MessageSource，国际化相关的资源，到ApplicationContext
  • 注册ApplicationListener到ApplicationContext
  • 实例化化lazy-init的Bean
  • 最后，publish相关的事件，ApplicationContext 就初始化完成，整个IOC容器初始化完成(IOC容器的本质就是初始化BeanFactory和ApplicationContext)，就可以从IOC容器中获取Bean自动注入了

SpringApplicationRunListener << EventPublishingRunListener

  2. public class EventPublishingRunListener implements SpringApplicationRunListener, Ordered {
  4.     private final SpringApplication application;
  6.     private final String[] args;
  8.     private final SimpleApplicationEventMulticaster initialMulticaster;
  10.     public EventPublishingRunListener(SpringApplication application, String[] args) {
  11.         this.application = application;
  12.         this.args = args;
  13.         this.initialMulticaster = new SimpleApplicationEventMulticaster();
  14.         for (ApplicationListener<?> listener : application.getListeners()) {
  15.             this.initialMulticaster.addApplicationListener(listener);
  16.         }
  17.     }
  19.     @Override
  20.     public int getOrder() {
  21.         return 0;
  22.     }
  24.     // SpringBoot 启动事件
  25.     @Override
  26.     public void starting(ConfigurableBootstrapContext bootstrapContext) {
  27.         this.initialMulticaster
  28.             .multicastEvent(new ApplicationStartingEvent(bootstrapContext, this.application, this.args));
  29.     }
  31.     // 创建和配置环境
  32.     @Override
  33.     public void environmentPrepared(ConfigurableBootstrapContext bootstrapContext,
  34.                                     ConfigurableEnvironment environment) {
  35.         this.initialMulticaster.multicastEvent(
  36.             new ApplicationEnvironmentPreparedEvent(bootstrapContext, this.application, this.args, environment));
  37.     }
  39.     // 准备ApplicationContext
  40.     @Override
  41.     public void contextPrepared(ConfigurableApplicationContext context) {
  42.         this.initialMulticaster
  43.             .multicastEvent(new ApplicationContextInitializedEvent(this.application, this.args, context));
  44.     }
  46.     // 发布ApplicationContext以及refresh事件，标志着ApplicaitonContext初始化完成
  47.     @Override
  48.     public void contextLoaded(ConfigurableApplicationContext context) {
  49.         for (ApplicationListener<?> listener : this.application.getListeners()) {
  50.             if (listener instanceof ApplicationContextAware) {
  51.                 ((ApplicationContextAware) listener).setApplicationContext(context);
  52.             }
  53.             context.addApplicationListener(listener);
  54.         }
  55.         this.initialMulticaster.multicastEvent(new ApplicationPreparedEvent(this.application, this.args, context));
  56.     }
  58.     // SpringBoot 以启动事件
  59.     @Override
  60.     public void started(ConfigurableApplicationContext context) {
  61.         context.publishEvent(new ApplicationStartedEvent(this.application, this.args, context));
  62.         AvailabilityChangeEvent.publish(context, LivenessState.CORRECT);
  63.     }
  65.     // “SpringBoot现在可以处理接受的请求” 事件
  66.     @Override
  67.     public void running(ConfigurableApplicationContext context) {
  68.         context.publishEvent(new ApplicationReadyEvent(this.application, this.args, context));
  69.         AvailabilityChangeEvent.publish(context, ReadinessState.ACCEPTING_TRAFFIC);
  70.     }
  72.     @Override
  73.     public void failed(ConfigurableApplicationContext context, Throwable exception) {
  74.         ApplicationFailedEvent event = new ApplicationFailedEvent(this.application, this.args, context, exception);
  75.         if (context != null && context.isActive()) {
  76.             // Listeners have been registered to the application context so we should
  77.             // use it at this point if we can
  78.             context.publishEvent(event);
  79.         }
  80.         else {
  81.             // An inactive context may not have a multicaster so we use our multicaster to
  82.             // call all of the context's listeners instead
  83.             if (context instanceof AbstractApplicationContext) {
  84.                 for (ApplicationListener<?> listener : ((AbstractApplicationContext) context)
  85.                      .getApplicationListeners()) {
  86.                     this.initialMulticaster.addApplicationListener(listener);
  87.                 }
  88.             }
  89.             this.initialMulticaster.setErrorHandler(new LoggingErrorHandler());
  90.             this.initialMulticaster.multicastEvent(event);
  91.         }
  92.     }
  94.     private static class LoggingErrorHandler implements ErrorHandler {
  96.         private static final Log logger = LogFactory.getLog(EventPublishingRunListener.class);
  98.         @Override
  99.         public void handleError(Throwable throwable) {
  100.             logger.warn("Error calling ApplicationEventListener", throwable);
  101.         }
  103.     }
  105. }

SpringBoot启动流程总结

  • 初始化环境
  • 初始化默认配置
  • 初始化各类监听器、事件
  • 创建上下文
  • 在上下文中添加默认的bean
  • 扫描文件、注解等各种类型的bean添加在上下文中
  • 实例化各个bean
  • 启动完毕

参考资料

【从入门到放弃-SpringBoot】SpringBoot源码分析-启动

https://nc2era.com/97473183.html

SPRINGBOOT启动流程及其原理

https://www.cnblogs.com/theRhyme/p/11057233.html

SPRINGBOOT启动原理（基于2.3.9.RELEASE版本）

https://www.cnblogs.com/theRhyme/p/how-does-springboot-start.html

Spring Boot 2.5.4 API

https://docs.spring.io/spring-boot/docs/2.5.4/api/

spring boot profile配置和启动时no active profile set, falling back to default profiles: default的问题

https://blog.csdn.net/benbenniaono1/article/details/105632264