Spring【版本5.2.2】容器初始化过程（二）refresh（一）

￡神魔★判官ぃ 2023-06-15 13:28 16阅读 0赞

下面来说说AnnotationConfigApplicationContext的第三个方法 **refresh**

/** * 准备好bean工厂，实例化对象 * @throws BeansException * @throws IllegalStateException */
    	@Override
    	public void refresh() throws BeansException, IllegalStateException { 
    
    		synchronized (this.startupShutdownMonitor) { 
    			// Prepare this context for refreshing.
    			// 调用容器准备初始化方法，获取容器的当前时间，同时给容器设置同步标识,是否激活标示位，
    			// 初始化属性源（property source）配置,还有各种Map，比如earlyApplicationListeners、
    			// earlyApplicationEvents、applicationListeners
    			prepareRefresh();
    
    			// Tell the subclass to refresh the internal bean factory[告诉子类，刷新内部工厂].
    			// 告诉子类启动refreshBeanFactory()方法，Bean定义资源文件的载入从子类的refreshBeanFactory()方法启动
    			ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
    
    			// Prepare the bean factory for use in this context.
    			// 为beanFactory配置容器特性，例如类加载器、时间处理器、环境变量等等
    			prepareBeanFactory(beanFactory);
    
    			try { 
    				// Allows post-processing of the bean factory in context subclasses.
    				// 为容器的某些子类指定特殊的BeanPost事件处理器,空方法,可能会在web等等其他模块用到，
    				postProcessBeanFactory(beanFactory);
    
    				// Invoke factory processors registered as beans in the context.
    				// 调用所有注册的BeanFactoryPostProcessor的Bean
    				// 在spring的环境中取执行被注册的factory processors，
    				// 设置执行自定义的ProcessBeanFactory和spring内部定义的
    				// 例如：ConfigurationClassPostProcessor（6大BD其中之一，其他五个不是）
    				// 偷偷的笑了，这个方法，网上应该有一大坨的文章，我们也当成一个独立的文章来吧，东西实在是太多了
    				// 本着实战注意，还是要自己断点走一遍，具体见后面的Spring容器初始化过程（三）
    				invokeBeanFactoryPostProcessors(beanFactory);
    
    				// Register bean processors that intercept bean creation.
    				// 2、得到spring内部自己维护的BeanDefinitionRegistryPostProcessor
    				// 为BeanFactory注册BeanPost事件处理器.
    				// BeanPostProcessor是Bean后置处理器，用于监听容器触发的事件
    				registerBeanPostProcessors(beanFactory);
    
    				// Initialize message source for this context.
    				initMessageSource();
    
    				// Initialize event multicaster for this context.
    				initApplicationEventMulticaster();
    
    				// Initialize other special beans in specific context subclasses.
    				onRefresh();
    
    				// Check for listener beans and register them.
    				registerListeners();
    
    				// Instantiate all remaining (non-lazy-init) singletons.
    				finishBeanFactoryInitialization(beanFactory);
    
    				// Last step: publish corresponding event.
    				finishRefresh();
    			}
    
    			catch (BeansException ex) { 
    				if (logger.isWarnEnabled()) { 
    					logger.warn("Exception encountered during context initialization - " +
    							"cancelling refresh attempt: " + ex);
    				}
    
    				// Destroy already created singletons to avoid dangling resources.
    				destroyBeans();
    
    				// Reset 'active' flag.
    				cancelRefresh(ex);
    
    				// Propagate exception to caller.
    				throw ex;
    			}
    
    			finally { 
    				// Reset common introspection caches in Spring's core, since we
    				// might not ever need metadata for singleton beans anymore...
    				resetCommonCaches();
    			}
    		}
    	}

#### 1. prepareRefresh ####

调用容器准备初始化方法，获取容器的当前时间，同时给容器设置同步标识,是否激活标示位，初始化属性源（property source）配置,还有各种Map，比如earlyApplicationListeners、  
earlyApplicationEvents、applicationListeners

#### 2. obtainFreshBeanFactory 方法 ####

告诉子类刷新内部bean工厂。其实他啥都不在做，就是先判断是否已经refreshed然后设置他，然后赋值serializationId

protected ConfigurableListableBeanFactory obtainFreshBeanFactory() { 
    	 	// 先判断是否已经refreshed，然后赋值serializationId
    	 	// 当前beanFactory的id和displayName：org.springframework.context.annotation.AnnotationConfigApplicationContext@4563e9ab
    		refreshBeanFactory();
    		return getBeanFactory();
    	}

#### 3. prepareBeanFactory 说明 ####

配置其标准的特性，比如上下文加载器ClassLoader和post-processors回调

/** * 配置其标准的特性，比如上下文加载器ClassLoader和post-processors回调 * Configure the factory's standard context characteristics, * such as the context's ClassLoader and post-processors. * @param beanFactory the BeanFactory to configure */
    	protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) { 
    		// Tell the internal bean factory to use the context's class loader etc.
    		// 添加一个类加载器
    		beanFactory.setBeanClassLoader(getClassLoader());
    		// 添加bean表达式解释器，为了能够让我们的beanFactory去解析bean表达式
    		beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
    
    		// 对象与String相互转换 比如 <property red="dao">
    		beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));
    
    		// Configure the bean factory with context callbacks.
    		// 添加一个后置处理器ApplicationContextAwareProcessor
    		// 能够在bean中获得各种Aware（*Aware都有其作用）
    		beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
    
    		// 忽略接口不自动注入
    		beanFactory.ignoreDependencyInterface(EnvironmentAware.class);
    		beanFactory.ignoreDependencyInterface(EmbeddedValueResolverAware.class);
    		beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class);
    		beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class);
    		beanFactory.ignoreDependencyInterface(MessageSourceAware.class);
    		beanFactory.ignoreDependencyInterface(ApplicationContextAware.class);
    
    		// BeanFactory interface not registered as resolvable type in a plain factory.
    		// MessageSource registered (and found for autowiring) as a bean.
    		// 依赖的替换
    		beanFactory.registerResolvableDependency(BeanFactory.class, beanFactory);
    		beanFactory.registerResolvableDependency(ResourceLoader.class, this);
    		beanFactory.registerResolvableDependency(ApplicationEventPublisher.class, this);
    		beanFactory.registerResolvableDependency(ApplicationContext.class, this);
    
    		// Register early post-processor for detecting inner beans as ApplicationListeners.
    		// 添加了一个ApplicationListenerDetector后置处理器
    		// 该BeanPostProcessor检测那些实现了接口ApplicationListener的bean，在它们创建时初始化之后，
    		// 将它们添加到应用上下文的事件多播器上；并在这些ApplicationListener bean销毁之前，将它们从应用上下文的事件多播器上移除。
    		beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(this));
    
    		// Detect a LoadTimeWeaver and prepare for weaving, if found.
    		if (beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) { 
    			beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
    			// Set a temporary ClassLoader for type matching.
    			beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
    		}
    
    		// Register default environment beans[注册默认环境bean].
    		/* 如果自定义Bean中没有"environment"、"systemProperties"和"systemEnvironment"的bean，则注册这两个Bean * Key为"environment"、"systemProperties"和"systemEnvironment"，Value为Map。 * 这两个Bean就是一些系统配置和系统环境信息 */
    		if (!beanFactory.containsLocalBean(ENVIRONMENT_BEAN_NAME)) { 
    			beanFactory.registerSingleton(ENVIRONMENT_BEAN_NAME, getEnvironment());
    		}
    		if (!beanFactory.containsLocalBean(SYSTEM_PROPERTIES_BEAN_NAME)) { 
    			beanFactory.registerSingleton(SYSTEM_PROPERTIES_BEAN_NAME, getEnvironment().getSystemProperties());
    		}
    		if (!beanFactory.containsLocalBean(SYSTEM_ENVIRONMENT_BEAN_NAME)) { 
    			beanFactory.registerSingleton(SYSTEM_ENVIRONMENT_BEAN_NAME, getEnvironment().getSystemEnvironment());
    		}
    	}

继续感谢子路老师，未完待续。。。