springboot源码剖析(四) 上下文启动
概念
springboot在启动流程中最重要的事情便是加载启动spring组件，比如加载IOC容器，启动springMVC等。
实现原理
使用AnnotationConfigServletWebServerApplicationContext（下面简称为上下文）加载和启动spring组件。其中注册的bean都会存储在defalutListableBeanFactory中。
uml类图
上下文启动流程
源码剖析
上下文启动
/** SpringApplication.class */ // 启动流程 public ConfigurableApplicationContext run(String... args) { // 根据应用类型实例化AnnotationConfigServletWebServerApplicationContext类 context = this.createApplicationContext(); // 异常报告类 exceptionReporters = this.getSpringFactoriesInstances(SpringBootExceptionReporter.class, new Class[]{ConfigurableApplicationContext.class}, context); // ★1.启动准备 this.prepareContext(context, environment, listeners, applicationArguments, printedBanner); // ★2.刷新上下文 this.refreshContext(context); // 空操作 this.afterRefresh(context, applicationArguments); } // 1.启动准备 private void prepareContext(ConfigurableApplicationContext context, ConfigurableEnvironment environment, SpringApplicationRunListeners listeners, ApplicationArguments applicationArguments, Banner printedBanner) { // ★ 1.1上下文设置环境配置 context.setEnvironment(environment); // 上下文的bean工厂列表设置转换服务 this.postProcessApplicationContext(context); // ★ 1.2 initializers初始化(调用对应的initialize方法,其中加载了beanFactoryPostProcessors) this.applyInitializers(context); // 1.3 事件发布器：通知监听器web服务初始化好了 listeners.contextPrepared(context); // 启动日志，默认为true if (this.logStartupInfo) { // 启动日志(第一条springboot日志) this.logStartupInfo(context.getParent() == null); // 开发环境日志 this.logStartupProfileInfo(context); } // 1.4 获取bean工厂列表提前注册实例一些单例bean ConfigurableListableBeanFactory beanFactory = context.getBeanFactory(); beanFactory.registerSingleton("springApplicationArguments", applicationArguments); if (printedBanner != null) { beanFactory.registerSingleton("springBootBanner", printedBanner); } // springboot默认不允许bean定义覆盖 if (beanFactory instanceof DefaultListableBeanFactory) { ((DefaultListableBeanFactory)beanFactory).setAllowBeanDefinitionOverriding(this.allowBeanDefinitionOverriding); } // springboot默认不是懒初始化 if (this.lazyInitialization) { context.addBeanFactoryPostProcessor(new LazyInitializationBeanFactoryPostProcessor()); } // 获取启动类 Set<Object> sources = this.getAllSources(); Assert.notEmpty(sources, "Sources must not be empty"); // 1.5 启动类注册进beanDefinitionMap当中 this.load(context, sources.toArray(new Object[0])); // 1.6 事件发布器：通知监听器上下文准备好了 listeners.contextLoaded(context); } // 2.刷新上下文 private void refreshContext(ConfigurableApplicationContext context) { // 2.1 调用上下文基类refresh方法 this.refresh((ApplicationContext)context); if (this.registerShutdownHook) { try { context.registerShutdownHook(); } catch (AccessControlException var3) { } } } /** AnnotationConfigServletWebServerApplicationContext.class 上下文 */ // 2.1 refresh核心逻辑 public void refresh() throws BeansException, IllegalStateException { synchronized(this.startupShutdownMonitor) { // 准备工作，初始化context的一些属性 this.prepareRefresh(); // 获取bean工厂列表 ConfigurableListableBeanFactory beanFactory = this.obtainFreshBeanFactory(); // 2.1.1 初始化bean工厂列表，如忽略依赖的接口，添加特定的beanPostProcessor，注册并实例化环境相关的bean this.prepareBeanFactory(beanFactory); try { // 2.1.2 同样还是给beanFactory添加beanPostProcessor以及registerResolvableDependency this.postProcessBeanFactory(beanFactory); // ★ 2.1.3 对BeanDefinitionRegistryPostProcessor，BeanFactoryPostProcessor类型的类按照优先级进行解析（spring扩展点，读取修改bean定义） this.invokeBeanFactoryPostProcessors(beanFactory); // ★ 2.1.4 同上，将BeanPostProcessors类型注册到bean工厂列表的BeanPostProcessors中。其中AutoWiredAnnotationBeanPostProcessor也在此注册。（穿插到实例化bean的前后） this.registerBeanPostProcessors(beanFactory); // 初始化MessageSource this.initMessageSource(); // 初始化ApplicationEventMulticaster（广播器） this.initApplicationEventMulticaster(); // ★ 2.1.5 创建web容器（启动tomcat，加载mvc，开启一个非守护线程保证springboot不会运行完终止） this.onRefresh(); // 注册监听者 this.registerListeners(); // ★ 2.1.6 实例化所有剩余的非懒加载单例 bean this.finishBeanFactoryInitialization(beanFactory); // 2.1.7 context发布上下文已刷新事件 this.finishRefresh(); } catch (BeansException var9) { if (this.logger.isWarnEnabled()) { this.logger.warn("Exception encountered during context initialization - cancelling refresh attempt: " + var9); } this.destroyBeans(); this.cancelRefresh(var9); throw var9; } finally { this.resetCommonCaches(); } } }
bean定义注册解析
/** PostProcessorRegistrationDelegate.class */ // 2.1.3 对BeanDefinitionRegistryPostProcessor，BeanFactoryPostProcessor类型的类进行解析（有优先级顺序）。 public static void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) { Set<String> processedBeans = new HashSet(); ArrayList regularPostProcessors; ArrayList registryProcessors; int var9; ArrayList currentRegistryProcessors; String[] postProcessorNames; if (beanFactory instanceof BeanDefinitionRegistry) { BeanDefinitionRegistry registry = (BeanDefinitionRegistry)beanFactory; regularPostProcessors = new ArrayList(); registryProcessors = new ArrayList(); Iterator var6 = beanFactoryPostProcessors.iterator(); // 2.1.3.1 对context里beanFactoryPostProcessors的BeanDefinitionRegistryPostProcessor类解析 （环境准备阶段，initializers/事件发布 加载beanPostProcessors到context中）监听器/初始化器的优先级还是很高的 while(var6.hasNext()) { BeanFactoryPostProcessor postProcessor = (BeanFactoryPostProcessor)var6.next(); if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) { BeanDefinitionRegistryPostProcessor registryProcessor = (BeanDefinitionRegistryPostProcessor)postProcessor; // 注册bean定义后置处理器 registryProcessor.postProcessBeanDefinitionRegistry(registry); // 加到已注册处理器数组 registryProcessors.add(registryProcessor); } else { // 常规处理 regularPostProcessors.add(postProcessor); } } // 2.1.3.2 查找beanDefinitionNames中BeanDefinitionRegistryPostProcessor类（context构造reader成员变量时生成） currentRegistryProcessors = new ArrayList(); postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false); String[] var16 = postProcessorNames; var9 = postProcessorNames.length; int var10; String ppName; for(var10 = 0; var10 < var9; ++var10) { ppName = var16[var10]; // 类型需要为PriorityOrdered.class if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) { // 得到的ConfigurationClassPostProcessor配置类后置处理器 currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class)); // 加入到已处理bean processedBeans.add(ppName); } } sortPostProcessors(currentRegistryProcessors, beanFactory); // 加入到已注册处理器数组 registryProcessors.addAll(currentRegistryProcessors); // ★ 2.1.3.3调用对应的注册方法，实现了各种spring核心注解的解析。从主类入口按照次序对@componentscan @import @bean等各种注解开始循环递归解析并生成beanDefination invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry); currentRegistryProcessors.clear(); // 2.1.3.4 再次查找beanDefinitionNames中BeanDefinitionRegistryPostProcessor类 postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false); var16 = postProcessorNames; var9 = postProcessorNames.length; for(var10 = 0; var10 < var9; ++var10) { ppName = var16[var10]; // 剔除掉上次已处理bean && 类型需要为PriorityOrdered.class if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) { currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class)); processedBeans.add(ppName); } } sortPostProcessors(currentRegistryProcessors, beanFactory); // 加入到已注册处理器数组 registryProcessors.addAll(currentRegistryProcessors); // 2.1.3.5 注册bean定义 invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry); currentRegistryProcessors.clear(); boolean reiterate = true; while(reiterate) { reiterate = false; // 2.1.3.6 再次查找beanDefinitionNames中BeanDefinitionRegistryPostProcessor类 postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false); String[] var19 = postProcessorNames; var10 = postProcessorNames.length; // 类型不再需要为PriorityOrdered.class for(int var26 = 0; var26 < var10; ++var26) { String ppName = var19[var26]; if (!processedBeans.contains(ppName)) { currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class)); processedBeans.add(ppName); reiterate = true; } } // 2.1.3.7 注册bean定义 sortPostProcessors(currentRegistryProcessors, beanFactory); registryProcessors.addAll(currentRegistryProcessors); invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry); currentRegistryProcessors.clear(); } // 2.1.3.8 调用已注册的BeanDefinitionRegistryPostProcessor父类的BeanFactoryPostProcessor的postProcessBeanFactory方法 invokeBeanFactoryPostProcessors((Collection)registryProcessors, (ConfigurableListableBeanFactory)beanFactory); invokeBeanFactoryPostProcessors((Collection)regularPostProcessors, (ConfigurableListableBeanFactory)beanFactory); } else { invokeBeanFactoryPostProcessors((Collection)beanFactoryPostProcessors, (ConfigurableListableBeanFactory)beanFactory); } // 2.1.3.9 同上，只是变成查找BeanFactoryPostProcessor类型 String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false); regularPostProcessors = new ArrayList(); registryProcessors = new ArrayList(); currentRegistryProcessors = new ArrayList(); postProcessorNames = postProcessorNames; int var20 = postProcessorNames.length; // 2.1.3.10 排列BeanFactoryPostProcessor的优先级：实现了PriorityOrdered > 实现了Ordered > 普通 String ppName; for(var9 = 0; var9 < var20; ++var9) { ppName = postProcessorNames[var9]; if (!processedBeans.contains(ppName)) { if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) { regularPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class)); } else if (beanFactory.isTypeMatch(ppName, Ordered.class)) { registryProcessors.add(ppName); } else { currentRegistryProcessors.add(ppName); } } } // 2.1.3.11 下面就是按优先级执行postProcessBeanFactory方法 sortPostProcessors(regularPostProcessors, beanFactory); invokeBeanFactoryPostProcessors((Collection)regularPostProcessors, (ConfigurableListableBeanFactory)beanFactory); List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList(registryProcessors.size()); Iterator var21 = registryProcessors.iterator(); while(var21.hasNext()) { String postProcessorName = (String)var21.next(); orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class)); } sortPostProcessors(orderedPostProcessors, beanFactory); invokeBeanFactoryPostProcessors((Collection)orderedPostProcessors, (ConfigurableListableBeanFactory)beanFactory); List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList(currentRegistryProcessors.size()); Iterator var24 = currentRegistryProcessors.iterator(); while(var24.hasNext()) { ppName = (String)var24.next(); nonOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class)); } invokeBeanFactoryPostProcessors((Collection)nonOrderedPostProcessors, (ConfigurableListableBeanFactory)beanFactory); beanFactory.clearMetadataCache(); }
