标签：初始化 beanFactory Spring --- SpringContext bean BeanDefinitionRegistryPostProcesso

一、概述

1.Spring Context概念

创建上下文并将BeanPostProcessor加载到spring

2.Spring Application Context概念

Spring通过应用上下文（Application Context）装载bean的定义并把它们组装起来。Spring应用上下文全权负责对象的创建和组装。

3. 关系

（1）Spring Context 模块核心是Spring Context

（2）Spring Context 核心是Spring Application Context

（3）Spring Application Context 的核心方法是 AbstractApplicationContext

二、AbstractApplicationContext之刷新源码分析

1. 基础源码

高效记忆：Spring应用文刷新 --- 刷机

（1）手机系统太卡了于是自己刷机。首先 准备刷机环境 （准备刷新上下文环境），准备好后老系统 初始化并加载 定义信息（初始化BeanFactory，并加载bean definitions信息）

（2）然后进行系统配置并（对beanFacotry进行配置）开始系统激活并提交过程（激活BeanFactoryPostProcessors）

（3）再进行验证码注册并提交过程（注册BeanPostProcessors），注册后新系统 初始化信息资源、广播 且注册监听器（初始化MessageSource、初始化事件广播器、注册事件监听器）

（4）最后系统 热加载弹粒 并（构造热加载单例bean）完成刷机 （完成刷新过程,通知生命周期处理器），如果刷机错误就 销户并修改 激活标识（销毁bean、修改active标识）

	@Override
	public void refresh() throws BeansException, IllegalStateException {
		synchronized (this.startupShutdownMonitor) {
			// Prepare this context for refreshing.
			prepareRefresh();   // #1 准备刷新上下文环境

			// Tell the subclass to refresh the internal bean factory.
			ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory(); // #2 初始化BeanFactory，并加载bean definitions信息

			// Prepare the bean factory for use in this context.
			prepareBeanFactory(beanFactory);    // #3 对beanFacotry进行配置

			try {
				// Allows post-processing of the bean factory in context subclasses.
				postProcessBeanFactory(beanFactory);    // #4  提供给子类扩展的预留方法

				// Invoke factory processors registered as beans in the context.
				invokeBeanFactoryPostProcessors(beanFactory);   // #5 激活BeanFactoryPostProcessors

				// Register bean processors that intercept bean creation.
				registerBeanPostProcessors(beanFactory);    // #6 注册BeanPostProcessors

				// Initialize message source for this context.
				initMessageSource();    // #7 初始化MessageSource

				// Initialize event multicaster for this context.
				initApplicationEventMulticaster();  // #8 初始化事件广播器

				// Initialize other special beans in specific context subclasses.
				onRefresh();    // #9 提供给子类初始化其他的Bean

				// Check for listener beans and register them.
				registerListeners();    // #10 注册事件监听器

				// Instantiate all remaining (non-lazy-init) singletons.
				finishBeanFactoryInitialization(beanFactory);   // #11 构造热加载单例bean

				// Last step: publish corresponding event.
				finishRefresh();    // #12 完成刷新过程,通知生命周期处理器
			}

			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(); // #13 出错了，销毁bean

				// Reset 'active' flag.
				cancelRefresh(ex);  // #14 出错了，修改active标识

				// 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();
			}
		}
	}

2.初始化并加载 obtainFreshBeanFactory

AbstractApplicationContext---obtainFreshBeanFactory ----> AbstractRefreshableApplicationContext---refreshBeanFactory

protected final void refreshBeanFactory() throws BeansException {
    if (hasBeanFactory()) { // #1 如果已存在BeanFactory，销毁原来的BeanFactory
        destroyBeans();
        closeBeanFactory();
    }
    try {
        DefaultListableBeanFactory beanFactory = createBeanFactory();   // #2 创建DefaultListableBeanFactory
        beanFactory.setSerializationId(getId());
        customizeBeanFactory(beanFactory);
        // #3 加载bean definitions信息，loadBeanDefinitions是抽象方法，不同实现类会从不同的配置中获取bean definitions信息，
        // 如AnnotationConfigWebApplicationContext，XmlWebApplicationContext。
        loadBeanDefinitions(beanFactory);   
        synchronized (this.beanFactoryMonitor) {
            this.beanFactory = beanFactory;
        }
    }
    catch (IOException ex) {
        throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
    }
}

3.激活 BeanFactoryPostProcessors

（1）BeanFactoryPostProcessor是spring提供的扩展接口，可以通过BeanFactoryPostProcessor对beanFactory进行自定义处理，如修改其他BeanDefinition的配置。

（2）BeanFactoryPostProcessor可以调整beanFactory，甚至修改BeanDefinition，如CustomEditorConfigurer，将用户定义的PropertyEditor注册到beanFactory中，以便后续使用。

（3）BeanDefinitionRegistryPostProcessor可以注册新的BeanDefinition，如ConfigurationClassPostProcessor，是实现springboot很关键的类

AbstractApplicationContext---invokeBeanFactoryPostProcessors ----> PostProcessorRegistrationDelegate---invokeBeanFactoryPostProcessors

public static void invokeBeanFactoryPostProcessors(
        ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {

    Set<String> processedBeans = new HashSet<String>();
	// #1 如果beanFactory是BeanDefinitionRegistry，需要处理BeanFactoryPostProcessors，
	// BeanDefinitionRegistryPostProcessor，否则只处理BeanFactoryPostProcessors
    if (beanFactory instanceof BeanDefinitionRegistry) {    
        BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
        List<BeanFactoryPostProcessor> regularPostProcessors = new LinkedList<BeanFactoryPostProcessor>();
        List<BeanDefinitionRegistryPostProcessor> registryPostProcessors =
                new LinkedList<BeanDefinitionRegistryPostProcessor>();
		// #2 方法参数beanFactoryPostProcessors是AbstractApplicationContext---beanFactoryPostProcessors属性，
		// 用户可以通过AbstractApplicationContext---addBeanFactoryPostProcessor方法添加BeanFactoryPostProcessor。这里对beanFactoryPostProcessors参数进行分类
        for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {              if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
                BeanDefinitionRegistryPostProcessor registryPostProcessor =
                        (BeanDefinitionRegistryPostProcessor) postProcessor;
                registryPostProcessor.postProcessBeanDefinitionRegistry(registry);
                registryPostProcessors.add(registryPostProcessor);
            }
            else {
                regularPostProcessors.add(postProcessor);
            }
        }

		// #3 获取beanFactory已经存在的BeanDefinitionRegistryPostProcessor，这里并没有直接构建BeanDefinitionRegistryPostProcessor，而且通过beanName获取
        String[] postProcessorNames =
                beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);    

        // First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.
        List<BeanDefinitionRegistryPostProcessor> priorityOrderedPostProcessors = new ArrayList<BeanDefinitionRegistryPostProcessor>();
        for (String ppName : postProcessorNames) {
            if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
                priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class)); 
                // #4 获取实现了PriorityOrdered接口的BeanDefinitionRegistryPostProcessor，添加到priorityOrderedPostProcessors     
                processedBeans.add(ppName);
            }
        }
        // #5 对priorityOrderedPostProcessors排序
        sortPostProcessors(beanFactory, priorityOrderedPostProcessors);     
        // #6 排序结果添加到registryPostProcessors
        registryPostProcessors.addAll(priorityOrderedPostProcessors);   
         // #7 调用BeanDefinitionRegistryPostProcessor#postProcessBeanDefinitionRegistry
        invokeBeanDefinitionRegistryPostProcessors(priorityOrderedPostProcessors, registry);   

        // Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.
        postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
        List<BeanDefinitionRegistryPostProcessor> orderedPostProcessors = new ArrayList<BeanDefinitionRegistryPostProcessor>();
        for (String ppName : postProcessorNames) {
        	// #8 处理实现了Ordered的BeanDefinitionRegistryPostProcessor
            if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {   
                orderedPostProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
                processedBeans.add(ppName);
            }
        }
        sortPostProcessors(beanFactory, orderedPostProcessors); 
        registryPostProcessors.addAll(orderedPostProcessors);
        invokeBeanDefinitionRegistryPostProcessors(orderedPostProcessors, registry);    

        // Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear.
        boolean reiterate = true;
        while (reiterate) {
            reiterate = false;
            postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
            for (String ppName : postProcessorNames) {
            	// #9 处理剩余的BeanDefinitionRegistryPostProcessor
                if (!processedBeans.contains(ppName)) { 
                    BeanDefinitionRegistryPostProcessor pp = beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class);
                    registryPostProcessors.add(pp);
                    processedBeans.add(ppName);
                    pp.postProcessBeanDefinitionRegistry(registry);
                    reiterate = true;
                }
            }
        }

        // Now, invoke the postProcessBeanFactory callback of all processors handled so far.
        invokeBeanFactoryPostProcessors(registryPostProcessors, beanFactory);   
        invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);    
    }

    ...
}

4.初始化事件广播 initApplicationEventMulticaster

4.1 Spring事件体系包括三个组件：

ApplicationEvent事件，ApplicationListener事件监听器，ApplicationEventMulticaster事件广播器。

4.2 事件广播器负责管理事件监听器，并将事件广播给监听器。

AbstractApplicationContext --- initApplicationEventMulticaster

rotected void initApplicationEventMulticaster() {
    ConfigurableListableBeanFactory beanFactory = getBeanFactory();
    if (beanFactory.containsLocalBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME)) {
        this.applicationEventMulticaster =
                beanFactory.getBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, ApplicationEventMulticaster.class);    //#1 使用用户定义的事件广播器
        if (logger.isDebugEnabled()) {
            logger.debug("Using ApplicationEventMulticaster [" + this.applicationEventMulticaster + "]");
        }
    }
    else {
        this.applicationEventMulticaster = new SimpleApplicationEventMulticaster(beanFactory);
        beanFactory.registerSingleton(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, this.applicationEventMulticaster);   //#2 使用默认的事件广播器
        if (logger.isDebugEnabled()) {
            logger.debug("Unable to locate ApplicationEventMulticaster with name '" +
                    APPLICATION_EVENT_MULTICASTER_BEAN_NAME +
                    "': using default [" + this.applicationEventMulticaster + "]");
        }
    }
}

4.3 spring事件

（1）spring提供了context start，stop，close，refresh等事件，ApplicationListener --- onApplicationEvent负责处理spring中的事件。

（2）我们可以通过实现ApplicationListener接口自行处理事件，也可以通过PublishListener自定义事件监听器。

使用默认的事件广播器 AbstractApplicationContexton --- publishEvent ----> SimpleApplicationEventMulticaster --- multicastEvent

public void multicastEvent(final ApplicationEvent event, ResolvableType eventType) {
    ResolvableType type = (eventType != null ? eventType : resolveDefaultEventType(event));
    for (final ApplicationListener<?> listener : getApplicationListeners(event, type)) {
        Executor executor = getTaskExecutor();  // #1 如果配置了Executor，使用Executor多线程处理
        if (executor != null) {
            executor.execute(new Runnable() {
                public void run() {
                    invokeListener(listener, event);
                }
            });
        }
        else {
            invokeListener(listener, event);    // #2 否则单线程处理
        }
    }
}

5.注册事件监听器

AbstractApplicationContext --- registerListeners将初始化事件监听器ApplicationListener，并绑定到事件广播器上。

protected void registerListeners() {
    for (ApplicationListener<?> listener : getApplicationListeners()) { // #1 getApplicationListeners()获取的是AbstractApplicationContext --- applicationListeners，用户可以通过AbstractApplicationContext --- addApplicationListener添加事件监听器
将AbstractApplicationContext#applicationListeners注册到applicationEventMulticaster
        getApplicationEventMulticaster().addApplicationListener(listener);
    }

    String[] listenerBeanNames = getBeanNamesForType(ApplicationListener.class, true, false);   // #2 将上下文中的ApplicationListener注册到applicationEventMulticaster
    for (String listenerBeanName : listenerBeanNames) {
        getApplicationEventMulticaster().addApplicationListenerBean(listenerBeanName);
    }

    Set<ApplicationEvent> earlyEventsToProcess = this.earlyApplicationEvents;   // #3 发布在此之前已发生的事件
    this.earlyApplicationEvents = null;
    if (earlyEventsToProcess != null) {
        for (ApplicationEvent earlyEvent : earlyEventsToProcess) {
            getApplicationEventMulticaster().multicastEvent(earlyEvent);
        }
    }
}

6.构造热加载单例bean

AbstractApplicationContext --- finishBeanFactoryInitialization

protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
    // Initialize conversion service for this context.
    if (beanFactory.containsBean(CONVERSION_SERVICE_BEAN_NAME) &&
            beanFactory.isTypeMatch(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class)) {
        beanFactory.setConversionService(
                beanFactory.getBean(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class));    //#1 初始化ConversionService，后面注入属性要使用
    }

    if (!beanFactory.hasEmbeddedValueResolver()) {
        beanFactory.addEmbeddedValueResolver(new StringValueResolver() {    //#2 初始化StringValueResolver，用于解析bean属性引用的properties配置
            @Override
            public String resolveStringValue(String strVal) {
                return getEnvironment().resolvePlaceholders(strVal);
            }
        });
    }

    String[] weaverAwareNames = beanFactory.getBeanNamesForType(LoadTimeWeaverAware.class, false, false);   //#3 初始化LoadTimeWeaverAware
    for (String weaverAwareName : weaverAwareNames) {
        getBean(weaverAwareName);
    }

    beanFactory.setTempClassLoader(null);

    beanFactory.freezeConfiguration();

    // Instantiate all remaining (non-lazy-init) singletons.
    beanFactory.preInstantiateSingletons(); //#4 构造热加载单例bean
}

AbstractApplicationContext --- preInstantiateSingletons

public void preInstantiateSingletons() throws BeansException {
    ...

    List<String> beanNames = new ArrayList<String>(this.beanDefinitionNames);

    for (String beanName : beanNames) {
        RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
        if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) { // #1 判断是否为非抽象类的热加载单例bean
            if (isFactoryBean(beanName)) {
                final FactoryBean<?> factory = (FactoryBean<?>) getBean(FACTORY_BEAN_PREFIX + beanName);
                    boolean isEagerInit;
                    if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) {
                        isEagerInit = AccessController.doPrivileged(new PrivilegedAction<Boolean>() {
                            @Override
                            public Boolean run() {
                                return ((SmartFactoryBean<?>) factory).isEagerInit();
                            }
                        }, getAccessControlContext());
                    }
                    else {
                        isEagerInit = (factory instanceof SmartFactoryBean &&
                                ((SmartFactoryBean<?>) factory).isEagerInit());
                    }
                    if (isEagerInit) {
                        getBean(beanName);
                    }
            }
            else {
                getBean(beanName);  // #2 构造bean：如果非FactoryBean，构造bean。如果FactoryBean并且FactoryBean.isEagerInit为true，构造bean。
            }
        }
    }
    ...
}

7. 完成刷新 finishRefresh

LifecycleProcessor也是spring提供的扩展点，通过它可以在spring content start，stop，onRefresh等时刻自定义一些额外操作

protected void finishRefresh() {
    // Initialize lifecycle processor for this context.
    initLifecycleProcessor();   // #1 初始化LifecycleProcessor

    // Propagate refresh to lifecycle processor first.
    getLifecycleProcessor().onRefresh();    // #2 调用LifecycleProcessor#onRefresh()方法

    // Publish the final event.
    publishEvent(new ContextRefreshedEvent(this));  // #3 发布事件

    // Participate in LiveBeansView MBean, if active.
    LiveBeansView.registerApplicationContext(this);
}

参考链接1

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标签：初始化,beanFactory,Spring,---,SpringContext,bean,BeanDefinitionRegistryPostProcesso
From： https://www.cnblogs.com/folyh/p/16933868.html

Spring之SpringContext