SpringApplication到底run了什么（下）

Posted 2021-04-28 Java学习录

在上篇文章中中，我们分析了下面这个run方法的前半部分，本篇文章继续开工

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public ConfigurableApplicationContext run(String... args) { //。。。 //接上文继续 configureIgnoreBeanInfo(environment); 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); stopWatch.stop(); if (this.logStartupInfo) { new StartupInfoLogger(this.mainApplicationClass) .logStarted(getApplicationLog(), stopWatch); } listeners.started(context); callRunners(context, applicationArguments); } catch (Throwable ex) { handleRunFailure(context, listeners, exceptionReporters, ex); throw new IllegalStateException(ex); } listeners.running(context); return context; }

6. 获取系统属性spring.beaninfo.ignore

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

但是这个属性的作用还真不知道。。

7. 打印banner

8. 根据当前环境创建ApplicationContext

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

基于咱们的Servlet环境，所以创建的ApplicationContext为AnnotationConfigServletWebServerApplicationContext

9. 加载SpringBootExceptionReporter，这个类里包含了SpringBoot启动失败后异常处理相关的组件

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private <T> Collection<T> getSpringFactoriesInstances(Class<T> type, Class<?>[] parameterTypes, Object... args) { ClassLoader classLoader = Thread.currentThread().getContextClassLoader(); Set<String> names = new LinkedHashSet<>( SpringFactoriesLoader.loadFactoryNames(type, classLoader)); List<T> instances = createSpringFactoriesInstances(type, parameterTypes, classLoader, args, names); AnnotationAwareOrderComparator.sort(instances); return instances; }

10 prepareContext 这一块还是比较长的

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

1. 第一行，将context中相关的environment全部替换

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public void setEnvironment(ConfigurableEnvironment environment) { super.setEnvironment(environment); // 设置context的environment this.reader.setEnvironment(environment); // 实例化context的reader属性的conditionEvaluator属性 this.scanner.setEnvironment(environment); // 设置context的scanner属性的environment属性 }

2. 上下文后处理

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protected void postProcessApplicationContext(ConfigurableApplicationContext context) { if (this.beanNameGenerator != null) { context.getBeanFactory().registerSingleton( AnnotationConfigUtils.CONFIGURATION_BEAN_NAME_GENERATOR, this.beanNameGenerator); } if (this.resourceLoader != null) { if (context instanceof GenericApplicationContext) { ((GenericApplicationContext) context) .setResourceLoader(this.resourceLoader); } if (context instanceof DefaultResourceLoader) { ((DefaultResourceLoader) context) .setClassLoader(this.resourceLoader.getClassLoader()); } } }

这一块默认beanNameGenerator和resourceLoader都是空的，只有当我们自定义这两个对象时才会把容器内的bean替换
3. 执行所有的ApplicationContextInitializer的initialize方法

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protected void applyInitializers(ConfigurableApplicationContext context) { for (ApplicationContextInitializer initializer : getInitializers()) { Class<?> requiredType = GenericTypeResolver.resolveTypeArgument( initializer.getClass(), ApplicationContextInitializer.class); Assert.isInstanceOf(requiredType, context, "Unable to call initializer."); initializer.initialize(context); } }

4. `listeners.contextPrepared(context)`这是个空方法，没有实现，一个Spring的扩展点
5. 打印profile
6. 注册bean：`springApplicationArguments`
7. 发布事件

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public void contextLoaded(ConfigurableApplicationContext context) { for (ApplicationListener<?> listener : this.application.getListeners()) { if (listener instanceof ApplicationContextAware) { ((ApplicationContextAware) listener).setApplicationContext(context); } context.addApplicationListener(listener); } this.initialMulticaster.multicastEvent( new ApplicationPreparedEvent(this.application, this.args, context)); }

这里不仅发布了ApplicationPreparedEvent事件，还往实现了ApplicationContextAware接口的监听器中注入了context容器
8. load，其实就是创建了一个BeanDefinitionLoader对象

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protected void load(ApplicationContext context, Object[] sources) { if (logger.isDebugEnabled()) { logger.debug( "Loading source " + StringUtils.arrayToCommaDelimitedString(sources)); } BeanDefinitionLoader loader = createBeanDefinitionLoader( getBeanDefinitionRegistry(context), sources); if (this.beanNameGenerator != null) { loader.setBeanNameGenerator(this.beanNameGenerator); } if (this.resourceLoader != null) { loader.setResourceLoader(this.resourceLoader); } if (this.environment != null) { loader.setEnvironment(this.environment); } loader.load(); }

11. 容器的初始化refreshContext
    这个方法最后还是调用的AbstractApplicationContext类的refresh方法，由于篇幅过长这里就不展开了，感兴趣的同学可以参考这篇文章：

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public void refresh() throws BeansException, IllegalStateException { synchronized (this.startupShutdownMonitor) { // 记录容器的启动时间、标记“已启动”状态、检查环境变量 prepareRefresh(); // 初始化BeanFactory容器、注册BeanDefinition ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory(); // 设置 BeanFactory 的类加载器，添加几个 BeanPostProcessor，手动注册几个特殊的 bean prepareBeanFactory(beanFactory); try { // 扩展点 postProcessBeanFactory(beanFactory); // 调用 BeanFactoryPostProcessor 各个实现类的 postProcessBeanFactory(factory) 方法 invokeBeanFactoryPostProcessors(beanFactory); // 注册 BeanPostProcessor 的实现类 registerBeanPostProcessors(beanFactory); // 初始化MessageSource initMessageSource(); // 初始化事件广播器 initApplicationEventMulticaster(); // 扩展点 onRefresh(); // 注册事件监听器 registerListeners(); // 初始化所有的 singleton beans finishBeanFactoryInitialization(beanFactory); // 广播事件 finishRefresh(); } catch (BeansException ex) { if (logger.isWarnEnabled()) { logger.warn("Exception encountered during context initialization - " + "cancelling refresh attempt: " + ex); } // 销毁已经初始化的的Bean destroyBeans(); // 设置 'active' 状态 cancelRefresh(ex); throw ex; } finally { // 清除缓存 resetCommonCaches(); } } }

12. afterRefresh
    这里没有任何实现，Spring留给我们的扩展点

13. 停止之前启动的计时装置，然后发送ApplicationStartedEvent事件

14. 调用系统中ApplicationRunner以及CommandLineRunner接口的实现类，关于这两个接口的使用可以参考我的这篇文章：

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private void callRunners(ApplicationContext context, ApplicationArguments args) { List<Object> runners = new ArrayList<>(); runners.addAll(context.getBeansOfType(ApplicationRunner.class).values()); runners.addAll(context.getBeansOfType(CommandLineRunner.class).values()); AnnotationAwareOrderComparator.sort(runners); for (Object runner : new LinkedHashSet<>(runners)) { if (runner instanceof ApplicationRunner) { callRunner((ApplicationRunner) runner, args); } if (runner instanceof CommandLineRunner) { callRunner((CommandLineRunner) runner, args); } } }

15. 异常处理

16. 发送ApplicationReadyEvent事件

往期好文

 

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