SpringBoot应用启动过程分析

 @Configuration public 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  Collection getSpringFactoriesInstances(Class type) { return getSpringFactoriesInstances(type, new Class[] {}); } private  Collection getSpringFactoriesInstances(Class 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 names = new LinkedHashSet( SpringFactoriesLoader.loadFactoryNames(type, classLoader)); List instances = createSpringFactoriesInstances(type, parameterTypes, classLoader, args, names); AnnotationAwareOrderComparator.sort(instances); return instances; } @SuppressWarnings("unchecked") private  List createSpringFactoriesInstances(Class type, Class[] parameterTypes, ClassLoader classLoader, Object[] args, Set names) { List instances = new ArrayList(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 loadFactoryNames(Class factoryClass, ClassLoader classLoader) { String factoryClassName = factoryClass.getName(); try { Enumeration urls = (classLoader != null ? classLoader.getResources(FACTORIES_RESOURCE_LOCATION) : ClassLoader.getSystemResources(FACTORIES_RESOURCE_LOCATION)); List result = new ArrayList(); 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 Loaders org.springframework.boot.env.PropertySourceLoader=\ org.springframework.boot.env.PropertiesPropertySourceLoader,\ org.springframework.boot.env.YamlPropertySourceLoader # Run Listeners org.springframework.boot.SpringApplicationRunListener=\ org.springframework.boot.context.event.EventPublishingRunListener # Application Context Initializers org.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 Listeners org.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 Processors org.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