SpringApplication到底run了什麼（下）
- 2019 年 10 月 7 日
- 筆記
在上篇文章中SpringApplication到底run了什麼（上）中，我們分析了下面這個run方法的前半部分，本篇文章繼續開工
public ConfigurableApplicationContext run(String... args) { //。。。 //接上文繼續 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; }
- 獲取系統屬性
spring.beaninfo.ignore
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()); } }
但是這個屬性的作用還真不知道。。
- 列印banner
- 根據當前環境創建ApplicationContext
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); }
基於咱們的Servlet環境，所以創建的ApplicationContext為AnnotationConfigServletWebServerApplicationContext
- 載入
SpringBootExceptionReporter，這個類里包含了SpringBoot啟動失敗後異常處理相關的組件
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 這一塊還是比較長的
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，將context中相關的environment全部替換
public void setEnvironment(ConfigurableEnvironment environment) { super.setEnvironment(environment); // 設置context的environment this.reader.setEnvironment(environment); // 實例化context的reader屬性的conditionEvaluator屬性 this.scanner.setEnvironment(environment); // 設置context的scanner屬性的environment屬性 }
2. 上下文後處理
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()); } } }
這一塊默認beanNameGenerator和resourceLoader都是空的，只有當我們自定義這兩個對象時才會把容器內的bean替換 3. 執行所有的ApplicationContextInitializer的initialize方法
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)`這是個空方法，沒有實現，一個Spring的擴展點 5. 列印profile 6. 註冊bean：`springApplicationArguments` 7. 發布事件
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)); }
這裡不僅發布了ApplicationPreparedEvent事件，還往實現了ApplicationContextAware介面的監聽器中注入了context容器 8. load，其實就是創建了一個BeanDefinitionLoader對象
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(); }
- 容器的初始化
refreshContext這個方法最後還是調用的AbstractApplicationContext類的refresh方法，由於篇幅過長這裡就不展開了，感興趣的同學可以參考這篇文章：基於註解的SpringIOC源碼解析
public void refresh() throws BeansException, IllegalStateException { synchronized (this.startupShutdownMonitor) { // 記錄容器的啟動時間、標記「已啟動」狀態、檢查環境變數 prepareRefresh(); // 初始化BeanFactory容器、註冊BeanDefinition ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory(); // 設置 BeanFactory 的類載入器，添加幾個 BeanPostProcessor，手動註冊幾個特殊的 bean prepareBeanFactory(beanFactory); try { // 擴展點 postProcessBeanFactory(beanFactory); // 調用 BeanFactoryPostProcessor 各個實現類的 postProcessBeanFactory(factory) 方法 invokeBeanFactoryPostProcessors(beanFactory); // 註冊 BeanPostProcessor 的實現類 registerBeanPostProcessors(beanFactory); // 初始化MessageSource initMessageSource(); // 初始化事件廣播器 initApplicationEventMulticaster(); // 擴展點 onRefresh(); // 註冊事件監聽器 registerListeners(); // 初始化所有的 singleton beans finishBeanFactoryInitialization(beanFactory); // 廣播事件 finishRefresh(); } catch (BeansException ex) { if (logger.isWarnEnabled()) { logger.warn("Exception encountered during context initialization - " + "cancelling refresh attempt: " + ex); } // 銷毀已經初始化的的Bean destroyBeans(); // 設置 'active' 狀態 cancelRefresh(ex); throw ex; } finally { // 清除快取 resetCommonCaches(); } } }
afterRefresh這裡沒有任何實現，Spring留給我們的擴展點- 停止之前啟動的計時裝置，然後發送
ApplicationStartedEvent事件 - 調用系統中
ApplicationRunner以及CommandLineRunner介面的實現類，關於這兩個介面的使用可以參考我的這篇文章：Java項目啟動時執行指定方法的幾種方式
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); } } }
- 異常處理
- 發送
ApplicationReadyEvent事件
