SpringBoot应用启动过程分析

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

 public static ConfigurableApplicationContext run(Object source, String... args) {  return run(new Object[] { source }, args); } public static ConfigurableApplicationContext run(Object[] sources, String[] args) {  return new SpringApplication(sources).run(args); }

public SpringApplication(Object... sources) {  initialize(sources); } @SuppressWarnings({ "unchecked", "rawtypes" }) private void initialize(Object[] sources) {  if (sources != null && sources.length > 0) {   this.sources.addAll(Arrays.asList(sources));  }  // 判断是否为WEB环境  this.webEnvironment = deduceWebEnvironment();  // 找到META-INF/spring.factories中ApplicationContextInitializer所有实现类，并将其实例化  setInitializers((Collection) getSpringFactoriesInstances(    ApplicationContextInitializer.class));  // 找到META-INF/spring.factories中ApplicationListener所有实现类，并将其实例化  setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));  // 获取当前main方法类对象，即测试类中的App实例  this.mainApplicationClass = deduceMainApplicationClass(); }

 private <T> Collection<? extends T> getSpringFactoriesInstances(Class<T> type) {  return getSpringFactoriesInstances(type, new Class<?>[] {}); } private <T> Collection<? extends T> getSpringFactoriesInstances(Class<T> type,   Class<?>[] parameterTypes, Object... args) {  ClassLoader classLoader = Thread.currentThread().getContextClassLoader();  // Use names and ensure unique to protect against duplicates  // 读取META-INF/spring.factories指定接口的实现类  Set<String> names = new LinkedHashSet<String>(    SpringFactoriesLoader.loadFactoryNames(type, classLoader));  List<T> instances = createSpringFactoriesInstances(type, parameterTypes,    classLoader, args, names);  AnnotationAwareOrderComparator.sort(instances);  return instances; } @SuppressWarnings("unchecked") private <T> List<T> createSpringFactoriesInstances(Class<T> type,   Class<?>[] parameterTypes, ClassLoader classLoader, Object[] args,   Set<String> names) {  List<T> instances = new ArrayList<T>(names.size());  for (String name : names) {   try {    Class<?> instanceClass = ClassUtils.forName(name, classLoader);    Assert.isAssignable(type, instanceClass);    Constructor<?> constructor = instanceClass.getConstructor(parameterTypes);    T instance = (T) constructor.newInstance(args);    instances.add(instance);   }   catch (Throwable ex) {    throw new IllegalArgumentException(      "Cannot instantiate " + type + " : " + name, ex);   }  }  return instances; } // 读取META-INF/spring.factories文件 public static List<String> loadFactoryNames(Class<?> factoryClass, ClassLoader classLoader) {  String factoryClassName = factoryClass.getName();  try {   Enumeration<URL> urls = (classLoader != null ? classLoader.getResources(FACTORIES_RESOURCE_LOCATION) :     ClassLoader.getSystemResources(FACTORIES_RESOURCE_LOCATION));   List<String> result = new ArrayList<String>();   while (urls.hasMoreElements()) {    URL url = urls.nextElement();    Properties properties = PropertiesLoaderUtils.loadProperties(new UrlResource(url));    String factoryClassNames = properties.getProperty(factoryClassName);    result.addAll(Arrays.asList(StringUtils.commaDelimitedListToStringArray(factoryClassNames)));   }   return result;  }  catch (IOException ex) {   throw new IllegalArgumentException("Unable to load [" + factoryClass.getName() +     "] factories from location [" + FACTORIES_RESOURCE_LOCATION + "]", ex);  } }

META-INF/spring.factories文件内容，spring boot版本1.3.6.RELEASE# PropertySource Loadersorg.springframework.boot.env.PropertySourceLoader=/org.springframework.boot.env.PropertiesPropertySourceLoader,/org.springframework.boot.env.YamlPropertySourceLoader# Run Listenersorg.springframework.boot.SpringApplicationRunListener=/org.springframework.boot.context.event.EventPublishingRunListener# Application Context Initializersorg.springframework.context.ApplicationContextInitializer=/org.springframework.boot.context.ConfigurationWarningsApplicationContextInitializer,/org.springframework.boot.context.ContextIdApplicationContextInitializer,/org.springframework.boot.context.config.DelegatingApplicationContextInitializer,/org.springframework.boot.context.web.ServerPortInfoApplicationContextInitializer# Application Listenersorg.springframework.context.ApplicationListener=/org.springframework.boot.builder.ParentContextCloserApplicationListener,/org.springframework.boot.context.FileEncodingApplicationListener,/org.springframework.boot.context.config.AnsiOutputApplicationListener,/org.springframework.boot.context.config.ConfigFileApplicationListener,/org.springframework.boot.context.config.DelegatingApplicationListener,/org.springframework.boot.liquibase.LiquibaseServiceLocatorApplicationListener,/org.springframework.boot.logging.ClasspathLoggingApplicationListener,/org.springframework.boot.logging.LoggingApplicationListener# Environment Post Processorsorg.springframework.boot.env.EnvironmentPostProcessor=/org.springframework.boot.cloud.CloudFoundryVcapEnvironmentPostProcessor,/org.springframework.boot.env.SpringApplicationJsonEnvironmentPostProcessor

public interface SpringApplicationRunListener { /**  * 通知监听器，SpringBoot开始启动  */ void started(); /**  * 通知监听器，环境配置完成  */ void environmentPrepared(ConfigurableEnvironment environment); /**  * 通知监听器，ApplicationContext已创建并初始化完成  */ void contextPrepared(ConfigurableApplicationContext context); /**  * 通知监听器，ApplicationContext已完成IOC配置  */ void contextLoaded(ConfigurableApplicationContext context); /**  * 通知监听器，SpringBoot开始完毕  */ void finished(ConfigurableApplicationContext context, Throwable exception);}

/**  * Run the Spring application, creating and refreshing a new  * {@link ApplicationContext}.  * @param args the application arguments (usually passed from a Java main method)  * @return a running {@link ApplicationContext}  */ public ConfigurableApplicationContext run(String... args) {  // 任务执行时间监听，记录起止时间差  StopWatch stopWatch = new StopWatch();  stopWatch.start();  ConfigurableApplicationContext context = null;  configureHeadlessProperty();  // 启动SpringApplicationRunListener监听器  SpringApplicationRunListeners listeners = getRunListeners(args);  listeners.started();  try {   ApplicationArguments applicationArguments = new DefaultApplicationArguments(     args);   // 创建并刷新ApplicationContext   context = createAndRefreshContext(listeners, applicationArguments);   afterRefresh(context, applicationArguments);   // 通知监听器，应用启动完毕   listeners.finished(context, null);   stopWatch.stop();   if (this.logStartupInfo) {    new StartupInfoLogger(this.mainApplicationClass)      .logStarted(getApplicationLog(), stopWatch);   }   return context;  }  catch (Throwable ex) {   handleRunFailure(context, listeners, ex);   throw new IllegalStateException(ex);  } }

private ConfigurableApplicationContext createAndRefreshContext(   SpringApplicationRunListeners listeners,   ApplicationArguments applicationArguments) {  ConfigurableApplicationContext context;  // Create and configure the environment  // 创建并配置运行环境，WebEnvironment与StandardEnvironment选其一  ConfigurableEnvironment environment = getOrCreateEnvironment();  configureEnvironment(environment, applicationArguments.getSourceArgs());  listeners.environmentPrepared(environment);  if (isWebEnvironment(environment) && !this.webEnvironment) {   environment = convertToStandardEnvironment(environment);  }  // 是否打印Banner，就是启动程序时出现的图形  if (this.bannerMode != Banner.Mode.OFF) {   printBanner(environment);  }  // Create, load, refresh and run the ApplicationContext  // 创建、装置、刷新、运行ApplicationContext  context = createApplicationContext();  context.setEnvironment(environment);  postProcessApplicationContext(context);  applyInitializers(context);  // 通知监听器，ApplicationContext创建完毕  listeners.contextPrepared(context);  if (this.logStartupInfo) {   logStartupInfo(context.getParent() == null);   logStartupProfileInfo(context);  }  // Add boot specific singleton beans  context.getBeanFactory().registerSingleton("springApplicationArguments",    applicationArguments);  // Load the sources  // 将beans载入到ApplicationContext容器中  Set<Object> sources = getSources();  Assert.notEmpty(sources, "Sources must not be empty");  load(context, sources.toArray(new Object[sources.size()]));  // 通知监听器，beans载入ApplicationContext完毕  listeners.contextLoaded(context);  // Refresh the context  refresh(context);  if (this.registerShutdownHook) {   try {    context.registerShutdownHook();   }   catch (AccessControlException ex) {    // Not allowed in some environments.   }  }  return context; }

protected ConfigurableApplicationContext createApplicationContext() {  Class<?> contextClass = this.applicationContextClass;  if (contextClass == null) {   try {    contextClass = Class.forName(this.webEnvironment      ? DEFAULT_WEB_CONTEXT_CLASS : DEFAULT_CONTEXT_CLASS);   }   catch (ClassNotFoundException ex) {    throw new IllegalStateException(      "Unable create a default ApplicationContext, "        + "please specify an ApplicationContextClass",      ex);   }  }  return (ConfigurableApplicationContext) BeanUtils.instantiate(contextClass); }