package org.springframework.boot;
public ConfigurableApplicationContext run(String... args) {
   //1.計時器
   StopWatch stopWatch = new StopWatch();
   stopWatch.start();
   ConfigurableApplicationContext context = null;
   Collection<SpringBootExceptionReporter> exceptionReporters = new ArrayList<>();
   //2.headless配置
   configureHeadlessProperty();
   //3、獲取監(jiān)聽
   SpringApplicationRunListeners listeners = getRunListeners(args);
   listeners.starting();
   try {
   //應(yīng)用程序啟動的參數(shù)  
      ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
      //4、準(zhǔn)備環(huán)境
      ConfigurableEnvironment environment = prepareEnvironment(listeners, applicationArguments);
      //環(huán)境創(chuàng)建成功后，配置bean信息，決定是否跳過 BeanInfo 類的掃描，如果設(shè)置為 true,則跳過
      configureIgnoreBeanInfo(environment);
      //打印banner信息
      Banner printedBanner = printBanner(environment);
      context = createApplicationContext();
      exceptionReporters = getSpringFactoriesInstances(SpringBootExceptionReporter.class,
            new Class[] { ConfigurableApplicationContext.class }, context);
      prepareContext(context, environment, listeners, applicationArguments, printedBanner);
      refreshContext(context);
      afterRefresh(context, applicationArguments);
      //停止計時
      stopWatch.stop();
      //控制是否打印日志的,這里為true，即打印日志
      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;
}

StopWatch stopWatch = new StopWatch();
//開始計時
stopWatch.start();
//停止計時
stopWatch.stop();

//將當(dāng)前類傳入StartupInfoLogger創(chuàng)建了一個對象
//然后調(diào)用logStarted打印日志
new StartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(), stopWatch);
//創(chuàng)建一個Log類
protected Log getApplicationLog() {
   if (this.mainApplicationClass == null) {
      return logger;
   }
   return LogFactory.getLog(this.mainApplicationClass);
}
//調(diào)用log類的log.info()方法來打印日志
public void logStarted(Log log, StopWatch stopWatch) {
    if (log.isInfoEnabled()) {
            log.info(getStartedMessage(stopWatch));
    }
}
//打印詳細(xì)的日志
private StringBuilder getStartedMessage(StopWatch stopWatch) {
   StringBuilder message = new StringBuilder();
   message.append("Started ");
   message.append(getApplicationName());
   message.append(" in ");
   message.append(stopWatch.getTotalTimeSeconds());
   try {
      double uptime = ManagementFactory.getRuntimeMXBean().getUptime() / 1000.0;
      message.append(" seconds (JVM running for " + uptime + ")");
   }
   catch (Throwable ex) {
      // No JVM time available
   }
   return message;
}

private static final String SYSTEM_PROPERTY_JAVA_AWT_HEADLESS = "java.awt.headless";
private void configureHeadlessProperty() {
   System.setProperty(SYSTEM_PROPERTY_JAVA_AWT_HEADLESS,
         System.getProperty(SYSTEM_PROPERTY_JAVA_AWT_HEADLESS, Boolean.toString(this.headless)));
}

//獲取所有監(jiān)聽
SpringApplicationRunListeners listeners = getRunListeners(args);
//啟動監(jiān)聽
listeners.starting();

private SpringApplicationRunListeners getRunListeners(String[] args) {
   Class<?>[] types = new Class<?>[] { SpringApplication.class, String[].class };
   return new SpringApplicationRunListeners(logger,
         getSpringFactoriesInstances(SpringApplicationRunListener.class, types, this, args));
}
private <T> Collection<T> getSpringFactoriesInstances(Class<T> type, Class<?>[] parameterTypes, Object... args) {
  //3.1獲取類加載器
   ClassLoader classLoader = getClassLoader();
   // Use names and ensure unique to protect against duplicates
   //3.2 根據(jù)類型獲取spring.factories中符合的類名
   Set<String> names = new LinkedHashSet<>(SpringFactoriesLoader.loadFactoryNames(type, classLoader));
   //3.3 創(chuàng)建類實例
   List<T> instances = createSpringFactoriesInstances(type, parameterTypes, classLoader, args, names);
   //對實例進(jìn)行排序
   AnnotationAwareOrderComparator.sort(instances);
   return instances;
}

/**
 * A collection of {@link SpringApplicationRunListener}.
 *
 * @author Phillip Webb
 */
class SpringApplicationRunListeners {
   private final Log log;
   private final List<SpringApplicationRunListener> listeners;
   SpringApplicationRunListeners(Log log, Collection<? extends SpringApplicationRunListener> listeners) {
      this.log = log;
      this.listeners = new ArrayList<>(listeners);
   }

/**
 *//可以理解為Spring Boot應(yīng)用的運行時監(jiān)聽器
 * Listener for the {@link SpringApplication} {@code run} method.
 *//SpringApplicationRunListener的構(gòu)造器參數(shù)必須依次為SpringApplication和String[]類型
 * {@link SpringApplicationRunListener}s are loaded via the {@link SpringFactoriesLoader}
 * and should declare a public constructor that accepts a {@link SpringApplication}
 * instance and a {@code String[]} of arguments.
 *//每次運行的時候?qū)?chuàng)建一個 SpringApplicationRunListener
  A new
 * {@link SpringApplicationRunListener} instance will be created for each run.
 *
 */
public interface SpringApplicationRunListener {
   /**
    * Called immediately when the run method has first started. Can be used for very
    * early initialization.
    */
    //Spring應(yīng)用剛啟動
   void starting();
   /**
    * Called once the environment has been prepared, but before the
    * {@link ApplicationContext} has been created.
    * @param environment the environment
    */
    //ConfigurableEnvironment準(zhǔn)備妥當(dāng)，允許將其調(diào)整
   void environmentPrepared(ConfigurableEnvironment environment);
   /**
    * Called once the {@link ApplicationContext} has been created and prepared, but
    * before sources have been loaded.
    * @param context the application context
    */
    //ConfigurableApplicationContext準(zhǔn)備妥當(dāng)，允許將其調(diào)整
   void contextPrepared(ConfigurableApplicationContext context);
   /**
    * Called once the application context has been loaded but before it has been
    * refreshed.
    * @param context the application context
    */
    //ConfigurableApplicationContext已裝載，但是任未啟動
   void contextLoaded(ConfigurableApplicationContext context);
   /**
    * The context has been refreshed and the application has started but
    * {@link CommandLineRunner CommandLineRunners} and {@link ApplicationRunner
    * ApplicationRunners} have not been called.
    * @param context the application context.
    * @since 2.0.0
    */
    //ConfigurableApplicationContext已啟動，此時Spring Bean已初始化完成
   void started(ConfigurableApplicationContext context);
   /**
    * Called immediately before the run method finishes, when the application context has
    * been refreshed and all {@link CommandLineRunner CommandLineRunners} and
    * {@link ApplicationRunner ApplicationRunners} have been called.
    * @param context the application context.
    * @since 2.0.0
    */
    //Spring應(yīng)用正在運行
   void running(ConfigurableApplicationContext context);
   /**
    * Called when a failure occurs when running the application.
    * @param context the application context or {@code null} if a failure occurred before
    * the context was created
    * @param exception the failure
    * @since 2.0.0
    */
    //Spring應(yīng)用運行失敗
   void failed(ConfigurableApplicationContext context, Throwable exception);
}

public class EventPublishingRunListener implements SpringApplicationRunListener, Ordered {
   private final SpringApplication application;
   private final String[] args;
   private final SimpleApplicationEventMulticaster initialMulticaster;
   public EventPublishingRunListener(SpringApplication application, String[] args) {
      this.application = application;
      this.args = args;
      this.initialMulticaster = new SimpleApplicationEventMulticaster();
      for (ApplicationListener<?> listener : application.getListeners()) {
         this.initialMulticaster.addApplicationListener(listener);
      }
   }

ClassLoader classLoader = getClassLoader();
public ClassLoader getClassLoader() {
  if (this.resourceLoader != null) {
     return this.resourceLoader.getClassLoader();
  }
  return ClassUtils.getDefaultClassLoader();
}

SpringFactoriesLoader.loadFactoryNames(type, classLoader)
public static List<String> loadFactoryNames(Class<?> factoryClass, @Nullable ClassLoader classLoader) {
//獲取類型名稱：org.springframework.context.ApplicationContextInitializer
   String factoryClassName = factoryClass.getName();
   return (List)loadSpringFactories(classLoader).getOrDefault(factoryClassName, Collections.emptyList());
}

private static Map<String, List<String>> loadSpringFactories(@Nullable ClassLoader classLoader) {
    //從緩存里面獲取
    MultiValueMap<String, String> result = (MultiValueMap)cache.get(classLoader);
    if (result != null) {
        return result;
    } else {
        try {
        //執(zhí)行classLoader.getResources("META-INF/spring.factories")，表示通過加載器獲取META-INF/spring.factories下的資源
            Enumeration<URL> urls = classLoader != null ? classLoader.getResources("META-INF/spring.factories") : ClassLoader.getSystemResources("META-INF/spring.factories");
            LinkedMultiValueMap result = new LinkedMultiValueMap();
            while(urls.hasMoreElements()) {
               //文件地址
                URL url = (URL)urls.nextElement();
                //從指定位置加載UrlResource
                UrlResource resource = new UrlResource(url);
                //加載里面的屬性，屬性見下圖
                Properties properties = PropertiesLoaderUtils.loadProperties(resource);
                Iterator var6 = properties.entrySet().iterator();
                while(var6.hasNext()) {
                    Entry<?, ?> entry = (Entry)var6.next();
                    //獲取key值
                    String factoryClassName = ((String)entry.getKey()).trim();
                    //獲取value值
                    String[] var9 = StringUtils.commaDelimitedListToStringArray((String)entry.getValue());
                    int var10 = var9.length;
//這里是將查詢出來的key作為result的key,value轉(zhuǎn)換成字符數(shù)組存放到result的value中
                    for(int var11 = 0; var11 < var10; ++var11) {
                        String factoryName = var9[var11];
                        result.add(factoryClassName, factoryName.trim());
                    }
                }
            }
            //將結(jié)果集存入緩存中
            cache.put(classLoader, result);
            return result;
        } catch (IOException var13) {
            throw new IllegalArgumentException("Unable to load factories from location [META-INF/spring.factories]", var13);
        }
    }
}

default V getOrDefault(Object key, V defaultValue) {
    V v;
    return (((v = get(key)) != null) || containsKey(key))
        ? v
        : defaultValue;
}

private <T> List<T> createSpringFactoriesInstances()(Class<T> type, Class<?>[] parameterTypes,
      ClassLoader classLoader, Object[] args, Set<String> names) {
   List<T> instances = new ArrayList<>(names.size());
   for (String name : names) {
      try {
      //根據(jù)類加載器獲取指定類
         Class<?> instanceClass = ClassUtils.forName(name, classLoader);
         Assert.isAssignable(type, instanceClass);
         //根據(jù)參數(shù)獲取構(gòu)造器
         Constructor<?> constructor = instanceClass.getDeclaredConstructor(parameterTypes);
         //根據(jù)傳入的構(gòu)造器對象以及構(gòu)造器所需的參數(shù)創(chuàng)建一個實例
         T instance = (T) BeanUtils.instantiateClass(constructor, args);
         //添加實例到集合中
         instances.add(instance);
      }
      catch (Throwable ex) {
         throw new IllegalArgumentException("Cannot instantiate " + type + " : " + name, ex);
      }
   }
   return instances;
}

prepareEnvironment(listeners, applicationArguments)

private ConfigurableEnvironment prepareEnvironment(SpringApplicationRunListeners listeners,
      ApplicationArguments applicationArguments) {
   // Create and configure the environment
   //4.1 創(chuàng)建一個環(huán)境
   ConfigurableEnvironment environment = getOrCreateEnvironment();
   //4.2 配置環(huán)境
   configureEnvironment(environment, applicationArguments.getSourceArgs());
   //4.3 ConfigurationPropertySourcesPropertySource對象存入到第一位
   ConfigurationPropertySources.attach(environment);
   //listeners環(huán)境準(zhǔn)備(就是廣播ApplicationEnvironmentPreparedEvent事件)
   listeners.environmentPrepared(environment);
   // 將環(huán)境綁定到SpringApplication
   bindToSpringApplication(environment);
     // 如果是非web環(huán)境，將環(huán)境轉(zhuǎn)換成StandardEnvironment
   if (!this.isCustomEnvironment) {
      environment = new EnvironmentConverter(getClassLoader()).convertEnvironmentIfNecessary(environment,
            deduceEnvironmentClass());
   }
    // 配置PropertySources對它自己的遞歸依賴
   ConfigurationPropertySources.attach(environment);
   return environment;
}

private ConfigurableEnvironment getOrCreateEnvironment() {
//有的話，直接返回
  if (this.environment != null) {
     return this.environment;
  }
  //這里我們在上面見到過，通過WebApplicationType.deduceFromClasspath()方法獲取的
  switch (this.webApplicationType) {
  case SERVLET:
     return new StandardServletEnvironment();
  case REACTIVE:
     return new StandardReactiveWebEnvironment();
  default:
     return new StandardEnvironment();
  }
}

protected void configureEnvironment(ConfigurableEnvironment environment, String[] args) {
   if (this.addConversionService) {
      ConversionService conversionService = ApplicationConversionService.getSharedInstance();
      environment.setConversionService((ConfigurableConversionService) conversionService);
   }
   configurePropertySources(environment, args);
   configureProfiles(environment, args);
}

protected void configurePropertySources(ConfigurableEnvironment environment, String[] args) {
//獲取所有的屬性源，就是獲取4.1的ConfigurableEnvironment上獲取到的屬性
  MutablePropertySources sources = environment.getPropertySources();
  if (this.defaultProperties != null && !this.defaultProperties.isEmpty()) {
     sources.addLast(new MapPropertySource("defaultProperties", this.defaultProperties));
  }
  //是否添加命令啟動參數(shù)，addCommandLineProperties為true，表示需要添加，但是前提是你得配置了參數(shù)
  if (this.addCommandLineProperties && args.length > 0) {
     String name = CommandLinePropertySource.COMMAND_LINE_PROPERTY_SOURCE_NAME;
     if (sources.contains(name)) {
        PropertySource<?> source = sources.get(name);
        CompositePropertySource composite = new CompositePropertySource(name);
        composite.addPropertySource(
              new SimpleCommandLinePropertySource("springApplicationCommandLineArgs", args));
        composite.addPropertySource(source);
        sources.replace(name, composite);
     }
     else {
        sources.addFirst(new SimpleCommandLinePropertySource(args));
     }
  }
}

protected void configureProfiles(ConfigurableEnvironment environment, String[] args) {
//獲取激活的環(huán)境
  environment.getActiveProfiles(); // ensure they are initialized
  // But these ones should go first (last wins in a property key clash)
  Set<String> profiles = new LinkedHashSet<>(this.additionalProfiles);
  profiles.addAll(Arrays.asList(environment.getActiveProfiles()));
  //設(shè)置當(dāng)前的環(huán)境
  environment.setActiveProfiles(StringUtils.toStringArray(profiles));
}

public static void attach(Environment environment) {
   Assert.isInstanceOf(ConfigurableEnvironment.class, environment);
   //獲取所有的屬性源，就是獲取4.1的ConfigurableEnvironment上獲取到的屬性
   MutablePropertySources sources = ((ConfigurableEnvironment) environment).getPropertySources();
   //判斷是否有 屬性 configurationProperties
   PropertySource<?> attached = sources.get(ATTACHED_PROPERTY_SOURCE_NAME);
   if (attached != null && attached.getSource() != sources) {
      sources.remove(ATTACHED_PROPERTY_SOURCE_NAME);
      attached = null;
   }
   if (attached == null) {
   // 將sources封裝成ConfigurationPropertySourcesPropertySource對象，并把這個對象放到sources的第一位置
      sources.addFirst(new ConfigurationPropertySourcesPropertySource(ATTACHED_PROPERTY_SOURCE_NAME,
            new SpringConfigurationPropertySources(sources)));
   }
}