SpringBoot启动过程图解 - Java天堂

实例化SpringApplication

public SpringApplication(ResourceLoader resourceLoader, Class<?>... primarySources) {
   this.resourceLoader = resourceLoader;
   Assert.notNull(primarySources, "PrimarySources must not be null");
   this.primarySources = new LinkedHashSet<>(Arrays.asList(primarySources));
   this.webApplicationType = deduceWebApplicationType();
    // 使用SpringFactoriesLoader.loadFactoryNames（SPI）来获取设置ApplicationContextInitializer类名
    // 使用BeanUtils.instantiateClass 来构造设置ApplicationContextInitializer对象
    // 设置ApplicationContextInitializer 到 SpringApplication.initializers 属性中
   setInitializers((Collection) getSpringFactoriesInstances(
         ApplicationContextInitializer.class));
    //用同样的方式加载 ApplicationListener
   setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));
    // 设置main方法所在的类。
   this.mainApplicationClass = deduceMainApplicationClass();
}

加载ApplicationContextInitializer

• SPI获取ApplicationContextInitializer
  • 

• 设置ApplicationContextInitializer到SpringApplication

  加载ApplicationListener

• 用同样的方式加载 ApplicationListener

  • 

    执行run方法

• SpringApplicationRunListeners

  • 

    public ConfigurableApplicationContext run(String… args) { StopWatch stopWatch = new StopWatch(); stopWatch.start(); ConfigurableApplicationContext context = null; Collection exceptionReporters = new ArrayList<>(); configureHeadlessProperty();

    //获取 SpringApplicationRunListener ，扩展点，用得少

    SpringApplicationRunListeners listeners = getRunListeners(args); listeners.starting(); try {

      ApplicationArguments applicationArguments = new DefaultApplicationArguments(
            args);
       //创建Environment，web和app创建类型不一样
      ConfigurableEnvironment environment = prepareEnvironment(listeners,
            applicationArguments);
      configureIgnoreBeanInfo(environment);
      Banner printedBanner = printBanner(environment);
       //创建ApplicationContext，
       //web=AnnotationConfigEmbeddedWebApplicationContext
       //app=AnnotationConfigApplicationContext
      context = createApplicationContext();
      exceptionReporters = getSpringFactoriesInstances(
            SpringBootExceptionReporter.class,
            new Class[] { ConfigurableApplicationContext.class }, context);
       //执行ApplicationContextInitializer initialize() 方法
       //执行SpringApplicationRunListener.contextPrepared()
       //注入ApplicationArguments对象
       //加载source到context中
      prepareContext(context, environment, listeners, applicationArguments,
            printedBanner);
       //调用context.refresh()，这就转到spring内部管理实例化bean等操作  
      refreshContext(context);
       //回调ApplicationRunner、ConmmandLineRunner（开机自启动）
      afterRefresh(context, applicationArguments);
      stopWatch.stop();
      if (this.logStartupInfo) {
         new StartupInfoLogger(this.mainApplicationClass)
               .logStarted(getApplicationLog(), stopWatch);
      }
      listeners.started(context);
      callRunners(context, applicationArguments);

    } catch (Throwable ex) {

      handleRunFailure(context, ex, exceptionReporters, listeners);
      throw new IllegalStateException(ex);

    }

    try {

      listeners.running(context);

    } catch (Throwable ex) {

      handleRunFailure(context, ex, exceptionReporters, null);
      throw new IllegalStateException(ex);

    } return context; }

getRunListeners(args);

【事件】listeners.starting();

prepareEnvironment

创建Environment

【事件】listeners.environmentPrepared(bootstrapContext, environment);

ConfigFileApplicationListener监听

ConfigFileApplicationListener#onApplicationEnvironmentPreparedEvent
执行EnvironmentPostProcessor#postProcessEnvironment

获取placeholdersResolver、resourceLoader、propertySourceLoaders

解析配置文件

默认配置文件位置：

spring cloud加载配置文件：BootstrapApplicationListener

SpringCloud

绑定spring.main到SpringApplication

createApplicationContext();

prepareContext(bootstrapContext, context, environment, listeners, applicationArguments, printedBanner);

applyInitializers(context);

DelegatingApplicationContextInitializer

• ConfigDataEnvironmentPostProcessor负责读取application.properties，加载到Environment。

  【事件】listeners.contextPrepared(context);

  加载BeanDefinition

  

  【事件】listeners.contextLoaded(context);

【applicationContext.refresh()】refreshContext(context);

【事件】listeners.started(context);

【ApplicationRunner】callRunners(context, applicationArguments);

【事件】listeners.running(context);