前言

由于最近个人工作不太繁忙，之前想看SpringBoot 源码， 今天终于能研究研究了。个人简单过了一边SpringApplication.run（） 方法的流程 这里记录一下。

这里将run方法中一些比较复杂的方法 在代码中加了注释

有错误希望指正！

SpringApplication.run() 方法 看注释

public ConfigurableApplicationContext run(String... args) {//创建时间记录类&启动时间记录StopWatch stopWatch = new StopWatch();stopWatch.start();//变量ConfigurableApplicationContext context = null;Collection<SpringBootExceptionReporter> exceptionReporters = new ArrayList<>();//设置系统属性configureHeadlessProperty();//创建所有 Spring 运行监听器并发布应用启动事件SpringApplicationRunListeners listeners = getRunListeners(args);listeners.starting();try {//初始化对象ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);//加载服务&系统资源ConfigurableEnvironment environment = prepareEnvironment(listeners, applicationArguments);configureIgnoreBeanInfo(environment);//打印SpringBoot 启动日志   就那个图形化日志//Banner的日志Banner printedBanner = printBanner(environment);//创建ConfigurableApplicationContextcontext = createApplicationContext();// springboot 自动装配 方法 获取  META-INF/spring.factories 文件下的所有exceptionReporters = getSpringFactoriesInstances(SpringBootExceptionReporter.class, new Class[] { ConfigurableApplicationContext.class }, context);prepareContext(context, environment, listeners, applicationArguments, printedBanner);//获取 context 封装//spring  核心方法 内部调用 ((AbstractApplicationContext) applicationContext).refresh()refreshContext(context);////空方法 afterRefresh(context, applicationArguments);//停止时间记录stopWatch.stop();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;
}

configureHeadlessProperty()

//在System系统中设置 属性
private void configureHeadlessProperty() {System.setProperty("java.awt.headless", System.getProperty("java.awt.headless", Boolean.toString(this.headless)));}

getRunListeners()

//创建所有 Spring 运行监听器并发布应用启动事件private SpringApplicationRunListeners getRunListeners(String[] args) {Class<?>[] types = new Class[]{SpringApplication.class, String[].class};return new SpringApplicationRunListeners(logger, this.getSpringFactoriesInstances(SpringApplicationRunListener.class, types, this, args));}

prepareEnvironment() & configureIgnoreBeanInfo()

prepareEnvironment()

    private ConfigurableEnvironment prepareEnvironment(SpringApplicationRunListeners listeners, ApplicationArguments applicationArguments) {ConfigurableEnvironment environment = this.getOrCreateEnvironment();this.configureEnvironment((ConfigurableEnvironment)environment, applicationArguments.getSourceArgs());ConfigurationPropertySources.attach((Environment)environment);listeners.environmentPrepared((ConfigurableEnvironment)environment);this.bindToSpringApplication((ConfigurableEnvironment)environment);if (!this.isCustomEnvironment) {environment = (new EnvironmentConverter(this.getClassLoader())).convertEnvironmentIfNecessary((ConfigurableEnvironment)environment, this.deduceEnvironmentClass());}ConfigurationPropertySources.attach((Environment)environment);return (ConfigurableEnvironment)environment;}

configureIgnoreBeanInfo()

private void configureIgnoreBeanInfo(ConfigurableEnvironment environment) {if (System.getProperty("spring.beaninfo.ignore") == null) {Boolean ignore = (Boolean)environment.getProperty("spring.beaninfo.ignore", Boolean.class, Boolean.TRUE);System.setProperty("spring.beaninfo.ignore", ignore.toString());}}

//加载服务&系统资源
ConfigurableEnvironment environment = prepareEnvironment(listeners, applicationArguments);
configureIgnoreBeanInfo(environment);
这一步 会获取到上图的 environment 对象 会获取到配置等信息

printBanner()

//打印SpringBoot 启动日志   就那个图形化日志private Banner printBanner(ConfigurableEnvironment environment) {if (this.bannerMode == Mode.OFF) {return null;} else {ResourceLoader resourceLoader = this.resourceLoader != null ? this.resourceLoader : new DefaultResourceLoader(this.getClassLoader());SpringApplicationBannerPrinter bannerPrinter = new SpringApplicationBannerPrinter((ResourceLoader)resourceLoader, this.banner);return this.bannerMode == Mode.LOG ? bannerPrinter.print(environment, this.mainApplicationClass, logger) : bannerPrinter.print(environment, this.mainApplicationClass, System.out);}}

服务启动 打印图形化日志 那个方法

createApplicationContext();

//创建 ConfigurableApplicationContext 对象protected ConfigurableApplicationContext createApplicationContext() {Class<?> contextClass = this.applicationContextClass;if (contextClass == null) {try {switch(this.webApplicationType) {case SERVLET:contextClass = Class.forName("org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext");break;case REACTIVE:contextClass = Class.forName("org.springframework.boot.web.reactive.context.AnnotationConfigReactiveWebServerApplicationContext");break;default:contextClass = Class.forName("org.springframework.context.annotation.AnnotationConfigApplicationContext");}} catch (ClassNotFoundException var3) {throw new IllegalStateException("Unable create a default ApplicationContext, please specify an ApplicationContextClass", var3);}}return (ConfigurableApplicationContext)BeanUtils.instantiateClass(contextClass);}

getSpringFactoriesInstances()

// springboot 自动装配 方法 获取  META-INF/spring.factories 文件下的所有
private <T> Collection<T> getSpringFactoriesInstances(Class<T> type, Class<?>[] parameterTypes, Object... args) {ClassLoader classLoader = this.getClassLoader();//loadFactoryNames()这个方法中 调用 loadSpringFactories(@Nullable ClassLoader classLoader) 方法 这个方法是加载 META-INF/spring.factories 文件中的内容Set<String> names = new LinkedHashSet(SpringFactoriesLoader.loadFactoryNames(type, classLoader));List<T> instances = this.createSpringFactoriesInstances(type, parameterTypes, classLoader, args, names);AnnotationAwareOrderComparator.sort(instances);return instances;}

prepareContext()

//对进行 context 封装   将BeanFactory 赋值private void prepareContext(ConfigurableApplicationContext context, ConfigurableEnvironment environment, SpringApplicationRunListeners listeners, ApplicationArguments applicationArguments, Banner printedBanner) {context.setEnvironment(environment);this.postProcessApplicationContext(context);this.applyInitializers(context);listeners.contextPrepared(context);if (this.logStartupInfo) {this.logStartupInfo(context.getParent() == null);this.logStartupProfileInfo(context);}ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();beanFactory.registerSingleton("springApplicationArguments", applicationArguments);if (printedBanner != null) {beanFactory.registerSingleton("springBootBanner", printedBanner);}if (beanFactory instanceof DefaultListableBeanFactory) {((DefaultListableBeanFactory)beanFactory).setAllowBeanDefinitionOverriding(this.allowBeanDefinitionOverriding);}Set<Object> sources = this.getAllSources();Assert.notEmpty(sources, "Sources must not be empty");this.load(context, sources.toArray(new Object[0]));listeners.contextLoaded(context);}

refreshContext()

refreshContext( ) 方法 调用是 refresh( )方法 Spring 的入口
//spring 核心方法 内部调用 ((AbstractApplicationContext) applicationContext).refresh()
这里就需要对Spring的源码需要了解了

//Spring   核心方法 内部调用 ((AbstractApplicationContext) applicationContext).refresh()protected void refresh(ApplicationContext applicationContext) {Assert.isInstanceOf(AbstractApplicationContext.class, applicationContext);((AbstractApplicationContext)applicationContext).refresh();}