Spring源码深度解析（八）——Spring环境的准备化工作

本是古典何须时尚 2023-07-15 13:09 14阅读 0赞

准备就包括了prepareRefresh()，obtainFreshBeanFactory()和prepareBeanFactory(beanFactory)。下面就逐个向下分析

## prepareRefresh() ##

主要是对容器的激活标记的设置，启动时间，验证环境还有初始化一个用于对消息事件的提前发布的Set，代码及其注释如下

/**
    	 * Prepare this context for refreshing, setting its startup date and
    	 * active flag as well as performing any initialization of property sources.
    	 */
    	protected void prepareRefresh() {
    		// Switch to active.
    		//激活容器，并设置当前时间为启动时间
    		this.startupDate = System.currentTimeMillis();
    		this.closed.set(false);
    		this.active.set(true);
    
    		if (logger.isDebugEnabled()) {
    			if (logger.isTraceEnabled()) {
    				logger.trace("Refreshing " + this);
    			} else {
    				logger.debug("Refreshing " + getDisplayName());
    			}
    		}
    
    		// Initialize any placeholder property sources in the context environment.
    		//空方法，不做任何事情
    		initPropertySources();
    
    		// Validate that all properties marked as required are resolvable:
    		// see ConfigurablePropertyResolver#setRequiredProperties
    		//获取当前环境并验证被标记的都是可以解析的
    		getEnvironment().validateRequiredProperties();
    
    		// Store pre-refresh ApplicationListeners...
    		// 初始化监听器，准备阶段是空，不是空就清空
    		if (this.earlyApplicationListeners == null) {
    			this.earlyApplicationListeners = new LinkedHashSet<>(this.applicationListeners);
    		} else {
    			// Reset local application listeners to pre-refresh state.
    			this.applicationListeners.clear();
    			this.applicationListeners.addAll(this.earlyApplicationListeners);
    		}
    
    		// Allow for the collection of early ApplicationEvents,
    		// to be published once the multicaster is available...
    		// 用于对消息事件的提前发布，为空
    		this.earlyApplicationEvents = new LinkedHashSet<>();
    	}

这个方法相对还是比较简单了，下面就来简单的代码调试一下  
可以看到在环境这里不改变的话是采用默认环境  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQyNjA1OTY4_size_16_color_FFFFFF_t_70]  
可以看到初始的提前事件监听器为空  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQyNjA1OTY4_size_16_color_FFFFFF_t_70 1]

## obtainFreshBeanFactory() ##

这个是获取在AnnotationContextApplicationContext中传入的BeanFactory，默认是DefaultListableBeanFactory。  
可以从调试信息看到结果  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQyNjA1OTY4_size_16_color_FFFFFF_t_70 2]

## prepareBeanFactory(beanFactory) ##

在上面得到BeanFactory后，现在就要对BeanFactory进行一些必要的设置以保证BeanFactory能正常运行,比如类加载器，Bean表达式解析器，Property资源编辑器，ApplicationContext的Bean后置处理器（可以对ApplicationContext进行扩展的），还有对一些内部接口类型的忽略，还有对一些的替换和对系统默认环境的注册。  
代码如下

/**
    	 * 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.
    		//告诉内部bean工厂使用上下文类加载器
    		beanFactory.setBeanClassLoader(getClassLoader());
    		//添加bean的表达式解析器，使beanFactory可以识别bean表达式
    		beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
    		//添加property资源编辑器注册器
    		beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));
    		// Configure the bean factory with context callbacks.
    		//添加Spring  bean的后置处理器   ApplicationContext的后置处理器
    		beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
    
    
    		//一个类实现下面这些接口的时候不会被自动注入
    		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.
    		//如beanFactory这些类没有在工厂中，在此进行注册    依赖替换，如果需要BeanFactory就把beanFactory作为替换
    		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.
    		// 注册事件监听器    如果这个Bean是ApplicationListener的子类，将它添加到listener列表
    		beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(this));
    
    		// Detect a LoadTimeWeaver and prepare for weaving, if found.
    		//加载时织入（不同于AOP这是静态的）
    		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.
    		//如果自定义的Bean中没有名字为“systemProperties”和“systemEnvironment”的Bean
    		//key为“systemProperties”和“systemEnvironment”  value为存系统信息和系统环境配置的Map
    		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());
    		}
    	}

可以看到准备完成的BeanFactory  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQyNjA1OTY4_size_16_color_FFFFFF_t_70 3]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQyNjA1OTY4_size_16_color_FFFFFF_t_70 4]

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