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
public ConfigurableApplicationContext run(String… args) {//。。。// 接上文继续 configureIgnoreBeanInfo(environment); Banner printedBanner = printBanner(environment); context= createApplicationContext(); exceptionReporters = getSpringFactoriesInstances( SpringBootExceptionReporter.class, newClass[] {ConfigurableApplicationContext.class},context); prepareContext(context, environment, listeners, applicationArguments, printedBanner); refreshContext(context); afterRefresh(context, applicationArguments); stopWatch.stop(); if(this.logStartupInfo) {newStartupInfoLogger(this.mainApplicationClass) .logStarted(getApplicationLog(), stopWatch); } listeners.started(context); callRunners(context, applicationArguments); } catch (Throwable ex) {handleRunFailure(context, listeners, exceptionReporters, ex); thrownewIllegalStateException(ex); } listeners.running(context); returncontext; }
- 获取系统属性 spring.beaninfo.ignore
privatevoidconfigureIgnoreBeanInfo(ConfigurableEnvironment environment) {if(System.getProperty( CachedIntrospectionResults.”spring.beaninfo.ignore”) ==null) {Booleanignore = 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。。
- 打印 banner
- 根据当前环境创建 ApplicationContext
protected ConfigurableApplicationContext createApplicationContext() { Class<?> contextClass =this.applicationContextClass; if(contextClass ==null) {try{ switch(this.webApplicationType) {caseSERVLET: contextClass = Class.forName(DEFAULT_WEB_CONTEXT_CLASS); break; caseREACTIVE: contextClass = Class.forName(DEFAULT_REACTIVE_WEB_CONTEXT_CLASS); break; default: contextClass = Class.forName(DEFAULT_CONTEXT_CLASS); } } catch(ClassNotFoundException ex) {thrownewIllegalStateException( “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
- 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
private<T>Collection<T> getSpringFactoriesInstances(Class<T> type, Class<?>[] parameterTypes,Object… args) {ClassLoaderclassLoader =Thread.currentThread().getContextClassLoader(); Set<String> names =newLinkedHashSet<>( SpringFactoriesLoader.loadFactoryNames(type, classLoader)); List<T> instances = createSpringFactoriesInstances(type, parameterTypes, classLoader, args, names); AnnotationAwareOrderComparator.sort(instances); returninstances; }
10 prepareContext 这一块还是比较长的
privatevoidprepareContext(ConfigurableApplicationContextcontext, 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(newObject[0])); listeners.contextLoaded(context);}1. 第一行，将 context 中相关的 environment 全部替换 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 protectedvoidpostProcessApplicationContext(ConfigurableApplicationContextcontext) {if(this.beanNameGenerator!=null) {context.getBeanFactory().registerSingleton(AnnotationConfigUtils.CONFIGURATION_BEAN_NAME_GENERATOR, this.beanNameGenerator); } if(this.resourceLoader!=null) {if(contextinstanceof GenericApplicationContext) {((GenericApplicationContext)context) .setResourceLoader(this.resourceLoader); } if(contextinstanceof 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
protectedvoidapplyInitializers(ConfigurableApplicationContextcontext) {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 profile6. 注册 bean：`springApplicationArguments`7. 发布事件 publicvoidcontextLoaded(ConfigurableApplicationContextcontext) {for(ApplicationListener<?> listener :this.application.getListeners()) {if(listener instanceof ApplicationContextAware) {((ApplicationContextAware) listener).setApplicationContext(context); } context.addApplicationListener(listener); } this.initialMulticaster.multicastEvent(newApplicationPreparedEvent(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
protectedvoidload(ApplicationContextcontext, 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();}
- 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：基于注解的 SpringIOC 源码解析
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); throwex; } finally{// 清除缓存 resetCommonCaches(); } }}
- afterRefresh
这里没有任何实现，Spring 留给我们的扩展点 - 停止之前启动的计时装置，然后发送 ApplicationStartedEvent 事件
- 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：Java 项目启动时执行指定方法的几种方式
privatevoidcallRunners(ApplicationContext context, ApplicationArguments args) {List<Object> runners =newArrayList<>(); runners.addAll(context.getBeansOfType(ApplicationRunner.class).values()); runners.addAll(context.getBeansOfType(CommandLineRunner.class).values()); AnnotationAwareOrderComparator.sort(runners); for(Objectrunner :newLinkedHashSet<>(runners)) {if(runnerinstanceofApplicationRunner) {callRunner((ApplicationRunner) runner, args); } if(runnerinstanceofCommandLineRunner) {callRunner((CommandLineRunner) runner, args); } } }
- 异常处理
- 发送 ApplicationReadyEvent 事件