@SpringBootApplication
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

public SpringApplication(ResourceLoader resourceLoader, Class<?>... primarySources) {
		this.resourceLoader = resourceLoader;
		Assert.notNull(primarySources, "PrimarySources must not be null");
		this.primarySources = new LinkedHashSet<>(Arrays.asList(primarySources));
		//此處推斷web容器類型是servlet 還是REACTIVE還是啥也不是即當(dāng)前非web容器
		this.webApplicationType = WebApplicationType.deduceFromClasspath();
		//此處進(jìn)入springFacories的加載 即SpringFactoriesLoader,不過(guò)此處是過(guò)濾處所有ApplicationContextInitializer的子類
		setInitializers((Collection) getSpringFactoriesInstances(
				ApplicationContextInitializer.class));
		//從springFactories的緩存中再過(guò)濾處	ApplicationListener 的子類	
		setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));
		this.mainApplicationClass = deduceMainApplicationClass();
	}

private static Map<String, List<String>> loadSpringFactories(@Nullable ClassLoader classLoader) {
		MultiValueMap<String, String> result = cache.get(classLoader);
		if (result != null) {
			return result;
		}
		try {
			//classLoader 上一步傳進(jìn)來(lái)的為AppClassLoader,如果對(duì)classLoader不了解需要去看看java的類加載機(jī)制，以及雙親委托機(jī)制，此處的資源加載也是個(gè)雙親委托機(jī)制。
			//此處如果appclassLoader不為null，那么遍歷遍歷這個(gè)classLoader所加載的包，中是否存在META-INF/spring.factories這個(gè)文件
			//如果存在最終生成一個(gè)集合，然后遍歷集合
			Enumeration<URL> urls = (classLoader != null ?
					classLoader.getResources(FACTORIES_RESOURCE_LOCATION) :
					ClassLoader.getSystemResources(FACTORIES_RESOURCE_LOCATION));
			result = new LinkedMultiValueMap<>();
			while (urls.hasMoreElements()) {
				URL url = urls.nextElement();
				//從集合中取出一個(gè)spring.factories文件
				UrlResource resource = new UrlResource(url);
				//讀取對(duì)應(yīng)文件內(nèi)容，作為一個(gè)properties對(duì)象
				Properties properties = PropertiesLoaderUtils.loadProperties(resource);
				//解析文件內(nèi)容，并將之放入一個(gè)LinkedMultiValueMap中，key就是spring.factories中等號(hào)前面的部分，值是后面部分根據(jù)都好組成的list。并放入緩存?zhèn)溆?，緩存的key為對(duì)應(yīng)的classLoader
				for (Map.Entry<?, ?> entry : properties.entrySet()) {
					String factoryClassName = ((String) entry.getKey()).trim();
					for (String factoryName : StringUtils.commaDelimitedListToStringArray((String) entry.getValue())) {
						result.add(factoryClassName, factoryName.trim());
					}
				}
			}
			cache.put(classLoader, result);
			return result;
		}
		catch (IOException ex) {
			throw new IllegalArgumentException("Unable to load factories from location [" +
					FACTORIES_RESOURCE_LOCATION + "]", ex);
		}
	}

result = new LinkedMultiValueMap<>();
list=new LinkList();
list.add("com.baomidou.mybatisplus.autoconfigure.MybatisPlusAutoConfiguration");
list.add("org.springframework.boot.autoconfigure.amqp.RabbitAutoConfiguration")
result.put("org.springframework.boot.autoconfigure.EnableAutoConfiguration",list);

public static List<String> loadFactoryNames(Class<?> factoryClass, @Nullable ClassLoader classLoader) {
		String factoryClassName = factoryClass.getName();
		return loadSpringFactories(classLoader).getOrDefault(factoryClassName, Collections.emptyList());
	}

private Class<?> deduceMainApplicationClass() {
		try {
			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;
	}

public ConfigurableApplicationContext run(String... args) {
		//計(jì)時(shí)器，不管它
		StopWatch stopWatch = new StopWatch();
		stopWatch.start();
		ConfigurableApplicationContext context = null;
		Collection<SpringBootExceptionReporter> exceptionReporters = new ArrayList<>();
		//告訴程序當(dāng)前為無(wú)頭模式，沒(méi)有外設(shè)，如果需要調(diào)用外設(shè)接口需要你自己模擬，這些內(nèi)容再awt包中做了，所以你只要告訴它有沒(méi)有外設(shè)就可以了
		configureHeadlessProperty();
		//繼續(xù)從spring.factories中獲取對(duì)應(yīng)的對(duì)象，此時(shí)listeners中有一個(gè)默認(rèn)實(shí)現(xiàn)EventPublishingRunListener，如有需要這里是可進(jìn)行擴(kuò)展
		SpringApplicationRunListeners listeners = getRunListeners(args);
		//遍歷所有的listeners并調(diào)用它的starting方法，廣播啟動(dòng)過(guò)程中的事件，注意這里是個(gè)廣播器不是監(jiān)聽(tīng)器，名字有點(diǎn)不好理解，實(shí)現(xiàn)了
		//ApplicationListener的接口就接收到對(duì)應(yīng)事件之后執(zhí)行對(duì)應(yīng)操作，而我們前面也有設(shè)置了個(gè)listeners集合，為ApplicationListener
		//此處名字起的讓人容易誤解，明明是個(gè)廣播器非要叫RunListener
		listeners.starting();
		try {
			//進(jìn)行控制臺(tái)參數(shù)解析，具體如何解析，此處不展開(kāi)，后續(xù)對(duì)配置文件解析的文章在詳細(xì)介紹
			ApplicationArguments applicationArguments = new DefaultApplicationArguments(
					args);
			ConfigurableEnvironment environment = prepareEnvironment(listeners,
					applicationArguments);
			//此處配置個(gè)內(nèi)省beanInfo時(shí)是否緩存的開(kāi)關(guān)，true就緩存，false，就不緩存		
			configureIgnoreBeanInfo(environment);
			//打印banner，這個(gè)不介紹了比較簡(jiǎn)單的東西
			Banner printedBanner = printBanner(environment);
			//此處開(kāi)始創(chuàng)建容器，根據(jù)給定的容器類型也就是上面獲取到的webApplicationType創(chuàng)建對(duì)應(yīng)的容器
			//servlet ：org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext
			//reactive：org.springframework.boot.web.reactive.context.AnnotationConfigReactiveWebServerApplicationContext
			//default:  org.springframework.context.annotation.AnnotationConfigApplicationContext 非web容器
			context = createApplicationContext();
			//異常解析器，如果出現(xiàn)異常了，會(huì)在被catch起來(lái)，然后通過(guò)解析器鏈進(jìn)行解析。這個(gè)也是從spring.factories中獲取的
			exceptionReporters = getSpringFactoriesInstances(
					SpringBootExceptionReporter.class,
					new Class[] { ConfigurableApplicationContext.class }, context);
			//上面創(chuàng)建了容器，這邊對(duì)容器做一些初始化操作
			//1、設(shè)置環(huán)境變量env
			//2、執(zhí)行postProcessApplicationContext 準(zhǔn)備beanNameGenerator,resourceLoader,ApplicationConversionService
			//3、調(diào)用前面獲取到的ApplicationContextInitializer
			//4、廣播容器準(zhǔn)備完成事件
			//5、添加了一個(gè)制定的單例就是banner打印用的
			//6、在加載前，設(shè)置是否允許bean被覆蓋屬性，默認(rèn)false
			//7、開(kāi)始加載，入口為main函數(shù)傳入的primarySources，先創(chuàng)建個(gè)BeanDefinitionLoader，并將第二步準(zhǔn)備的實(shí)例設(shè)置給他，
			//最后由BeanDefinitionLoader.load()承當(dāng)所有的加載動(dòng)作,加載過(guò)程也很長(zhǎng)，先按下不表。
			//8、廣播容器加載事件
			//到此容器準(zhǔn)備完成		
			prepareContext(context, environment, listeners, applicationArguments,
					printedBanner);
			//開(kāi)始執(zhí)行spring的refresh方法,此處不多介紹了
			refreshContext(context);
			//容器refresh完成后留了個(gè)擴(kuò)展，也不知道是不是擴(kuò)展，這個(gè)方法需要去自定義啟動(dòng)類，有點(diǎn)奇怪
			afterRefresh(context, applicationArguments);
			stopWatch.stop();
			if (this.logStartupInfo) {
				new StartupInfoLogger(this.mainApplicationClass)
						.logStarted(getApplicationLog(), stopWatch);
			}
			//然后廣播啟動(dòng)完成事件
			listeners.started(context);
			//最后執(zhí)行所有的runners，也就是實(shí)現(xiàn)了ApplicationRunner接口的類是最后執(zhí)行，所以此時(shí)你可以做一些其它的動(dòng)作，比如注冊(cè)到注冊(cè)中心，比如啟動(dòng)netty等等。
			callRunners(context, applicationArguments);
		}
		catch (Throwable ex) {
			handleRunFailure(context, ex, exceptionReporters, listeners);
			throw new IllegalStateException(ex);
		}
		//在廣播一個(gè)運(yùn)行中的事件
		try {
			listeners.running(context);
		}
		catch (Throwable ex) {
			handleRunFailure(context, ex, exceptionReporters, null);
			throw new IllegalStateException(ex);
		}
		return context;
	}

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@SpringBootConfiguration
@EnableAutoConfiguration
@ComponentScan(excludeFilters = {
		@Filter(type = FilterType.CUSTOM, classes = TypeExcludeFilter.class),
		@Filter(type = FilterType.CUSTOM, classes = AutoConfigurationExcludeFilter.class) })

  @Target(ElementType.TYPE)
  @Retention(RetentionPolicy.RUNTIME)
  @Documented
  @Inherited
  @AutoConfigurationPackage
  @Import(AutoConfigurationImportSelector.class)
  public @interface EnableAutoConfiguration {