1毕荐、創(chuàng)建SpringApplication對象

initialize(sources);
private void initialize(Object[] sources) {
    //保存主配置類
    if (sources != null && sources.length > 0) {
        this.sources.addAll(Arrays.asList(sources));
    }
    //判斷當(dāng)前是否一個web應(yīng)用
    this.webEnvironment = deduceWebEnvironment();
    //從類路徑下找到META-INF/spring.factories配置的所有ApplicationContextInitializer水评；然后保存起來
    setInitializers((Collection) getSpringFactoriesInstances(
        ApplicationContextInitializer.class));
    //從類路徑下找到ETA-INF/spring.factories配置的所有ApplicationListener
    setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));
    //從多個配置類中找到有main方法的主配置類
    this.mainApplicationClass = deduceMainApplicationClass();
}

2浑玛、運(yùn)行run()方法

public ConfigurableApplicationContext run(String... args) {
   StopWatch stopWatch = new StopWatch();
   stopWatch.start();
   ConfigurableApplicationContext context = null;
   FailureAnalyzers analyzers = null;
   configureHeadlessProperty();
    
   //獲取SpringApplicationRunListeners；從類路徑下META-INF/spring.factories
   SpringApplicationRunListeners listeners = getRunListeners(args);
    //回調(diào)所有的獲取SpringApplicationRunListener.starting()方法
   listeners.starting();
   try {
       //封裝命令行參數(shù)
      ApplicationArguments applicationArguments = new DefaultApplicationArguments(
            args);
      //準(zhǔn)備環(huán)境
      ConfigurableEnvironment environment = prepareEnvironment(listeners,
            applicationArguments);
            //創(chuàng)建環(huán)境完成后回調(diào)SpringApplicationRunListener.environmentPrepared()拒名；表示環(huán)境準(zhǔn)備完成
       
      Banner printedBanner = printBanner(environment);
       
       //創(chuàng)建ApplicationContext吩愧；決定創(chuàng)建web的ioc還是普通的ioc
      context = createApplicationContext();
       
      analyzers = new FailureAnalyzers(context);
       //準(zhǔn)備上下文環(huán)境;將environment保存到ioc中；而且applyInitializers()增显；
       //applyInitializers()：回調(diào)之前保存的所有的ApplicationContextInitializer的initialize方法
       //回調(diào)所有的SpringApplicationRunListener的contextPrepared()雁佳；
       //
      prepareContext(context, environment, listeners, applicationArguments,
            printedBanner);
       //prepareContext運(yùn)行完成以后回調(diào)所有的SpringApplicationRunListener的contextLoaded（）；
       
       //s刷新容器同云；ioc容器初始化（如果是web應(yīng)用還會創(chuàng)建嵌入式的Tomcat）糖权；Spring注解版
       //掃描，創(chuàng)建梢杭，加載所有組件的地方温兼；（配置類，組件武契，自動配置）
      refreshContext(context);
       //從ioc容器中獲取所有的ApplicationRunner和CommandLineRunner進(jìn)行回調(diào)
       //ApplicationRunner先回調(diào)募判，CommandLineRunner再回調(diào)
      afterRefresh(context, applicationArguments);
       //所有的SpringApplicationRunListener回調(diào)finished方法
      listeners.finished(context, null);
      stopWatch.stop();
      if (this.logStartupInfo) {
         new StartupInfoLogger(this.mainApplicationClass)
               .logStarted(getApplicationLog(), stopWatch);
      }
       //整個SpringBoot應(yīng)用啟動完成以后返回啟動的ioc容器；
      return context;
   }
   catch (Throwable ex) {
      handleRunFailure(context, listeners, analyzers, ex);
      throw new IllegalStateException(ex);
   }
}

3咒唆、事件監(jiān)聽機(jī)制

public class HelloSpringApplicationRunListener implements SpringApplicationRunListener {

    //必須有的構(gòu)造器
    public HelloSpringApplicationRunListener(SpringApplication application, String[] args){

    }

    @Override
    public void starting() {
        System.out.println("SpringApplicationRunListener...starting...");
    }

    @Override
    public void environmentPrepared(ConfigurableEnvironment environment) {
        Object o = environment.getSystemProperties().get("os.name");
        System.out.println("SpringApplicationRunListener...environmentPrepared.."+o);
    }

    @Override
    public void contextPrepared(ConfigurableApplicationContext context) {
        System.out.println("SpringApplicationRunListener...contextPrepared...");
    }

    @Override
    public void contextLoaded(ConfigurableApplicationContext context) {
        System.out.println("SpringApplicationRunListener...contextLoaded...");
    }

    @Override
    public void finished(ConfigurableApplicationContext context, Throwable exception) {
        System.out.println("SpringApplicationRunListener...finished...");
    }
}