Spring源码之ApplicationContext

时间:2021-03-18 09:57:00 来源:互联网 作者: 神秘的大神 字体:

​ 本文是针对Srping的ClassPathXMLApplicationContext来进行源码解析,在本篇博客中将不会讲述spring Xml解析注册代码,因为ApplicationContext是BeanFactory的扩展版本,ApplicationContext的GetBean和xml解析注册BeanDefinition都是用一套代码,如果您是第一次看请先看一下XMLBeanFactory解析和BeanFactory.GetBean源码解析:

  • XMLBeanFactory源码解析地址:https://www.cnblogs.com/technology-blog/p/14543685.html
  • BeanFactory.getBean源码解析地址:https://www.cnblogs.com/technology-blog/p/14543902.html

作者整理了spring-framework 5.x的源码注释,代码已经上传者作者的GitHub了,可以让读者更好的理解,地址:

  • 接下来直接上源码:
package lantao;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.lantao.UserBean;

public class ApplicationContextTest {

	public static void main(String[] args) {
		ApplicationContext applicationContext = new ClassPathXmlApplicationContext("spring-bean.xml");
		UserBean userBean = (UserBean) applicationContext.getBean("userBean");
		System.out.println(userBean.getName());
	}

}

在这里直接使用ClassPathXmlApplicationContext进行xml解析,在这里xml解析的代码和GetBean的代码就不过多的描述了,ApplicationContext是BeanFactory的扩展,所以想要看这两部分源码的请看作者的上两篇博客Sprin源码解析;

  • 接下来我们看一下ClassPathXmlApplicationContext的源码:
/**
 * Create a new ClassPathXmlApplicationContext with the given parent,
 * loading the definitions from the given XML files.
 * @param configLocations array of resource locations
 * @param refresh whether to automatically refresh the context,
 * loading all bean definitions and creating all singletons.
 * Alternatively, call refresh manually after further configuring the context.
 * @param parent the parent context
 * @throws BeansException if context creation failed
 * @see #refresh()
 */
public ClassPathXmlApplicationContext(
		String[] configLocations, boolean refresh, @Nullable ApplicationContext parent)
		throws BeansException {

	super(parent);
	// 支持解析多文件
	setConfigLocations(configLocations);
	if (refresh) {
		refresh();
	}
}

在setConfigLocations方法中将资源文件放入configLocations全局变量中,,并且支持多文件解析,接下来我们你看一下重点,refresh方法;

  • 源码refresh方法:
@Override
public void refresh() throws BeansException, IllegalStateException {
	synchronized (this.startupShutdownMonitor) {
		// Prepare this context for refreshing.
		// 准备刷新上下文
		prepareRefresh();

		// Tell the subclass to refresh the internal bean factory.
		// 对beanFactory的各种功能填充,加载beanFactory,经过这个方法 applicationContext就有了BeanFactory的所有功能
		ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

		// Prepare the bean factory for use in this context.
		// 对beanFactory进行各种功能填充
		prepareBeanFactory(beanFactory);

			try {
			// Allows post-processing of the bean factory in context subclasses.
			//  允许在context子类中对BeanFactory进行post-processing。
			// 允许在上下文子类中对Bean工厂进行后处理
			// 可以在这里进行 硬编码形式的 BeanFactoryPostProcessor 调用 addBeanFactoryPostProcessor
			postProcessBeanFactory(beanFactory);

			// Invoke factory processors registered as beans in the context.
			// 激活各种BeanFactory处理器 BeanFactoryPostProcessors是在实例化之前执行
			invokeBeanFactoryPostProcessors(beanFactory);

			// Register bean processors that intercept bean creation.
			// 注册 拦截Bean创建 的Bean处理器,这里只是注册,真正地调用在getBean的时候  BeanPostProcessors实在init方法前后执行 doCreateBean方法中的 实例化方法中执行
			// BeanPostProcessor执行位置:doCreateBean --> initializeBean --> applyBeanPostProcessorsBeforeInitialization 和 applyBeanPostProcessorsAfterInitialization
			registerBeanPostProcessors(beanFactory);

			// Initialize message source for this context.
			//为上下文初始化Message源,(比如国际化处理) 这里没有过多深入
			initMessageSource();

			// Initialize event multicaster for this context.
			//初始化应用消息广播,并放入 applicationEventMulticaster bean中
			initApplicationEventMulticaster();

			// Initialize other special beans in specific context subclasses.
			//留给子类来初始化其它的bean
			onRefresh();

			// Check for listener beans and register them.
			//在所有注册的bean中查找Listener bean,注册到消息广播器中
			registerListeners();

			// Instantiate all remaining (non-lazy-init) singletons.
			//初始化剩下的单实例
			finishBeanFactoryInitialization(beanFactory);

			// Last step: publish corresponding event.
			//完成刷新过程,通知生命周期护处理器lifecycleProcessor刷新过程,同时发出ContextRefreshEvent通知别人(LifecycleProcessor 用来与所有声明的bean的周期做状态更新)
			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();
		}
	}
}

对于ApplicationContext来说,refresh方法几乎涵盖了所有的基础和扩展功能,接下来看一下这个方法都做了什么;

  1. 刷新上下文,初始化前的准备工作;
  2. 加载beanFactory,经过这个方法 applicationContext就有了BeanFactory的所有功能
  3. 对beanFactory进行各种功能填充
  4. 允许在这里对BeanFactory的二次加工,例如:可以在这里进行硬编码方法的对BeanFactory进行BeanFactoryPostProcessor或BeanPostProcessor的操作;在这里简单说一下BeanFactoryPostProcessor是在bean实例化之前执行的,BeanPostProcessor是在初始化方法前后执行的,BeanFactoryPostProcessor操作的是BeanFactoryBeanPostProcessor操作的是Bean,其次这里还涉及了一个扩展BeanDefinitionRegistryPostProcessor它是继承了BeanFactoryPostProcessor,并且还有自己的定义方法 postProcessBeanDefinitionRegistry,这个方法可以操作BeanDefinitionRegistry,BeanDefinitionRegistry有个最主要的方法就是registerBeanDefinition,可以注册BeanDefinition,可以用这方法来处理一下不受spring管理的一下bean;
  5. 处理所有的BeanFactoryPostProcessor,也可以说是激活BeanFactory处理器,在这个方法里会先处理BeanDefinitionRegistryPostProcessor,在处理BeanFactoryPostProcessor,因为BeanDefinitionRegistryPostProcessor有自己的定义,所以先执行;
  6. 注册BeanPostProcessors ,这里只是注册,真正地调用在getBean的时候 BeanPostProcessors是在init方法前后执行 BeanPostProcessor执行位置:doCreateBean --> initializeBean --> applyBeanPostProcessorsBeforeInitialization 和 applyBeanPostProcessorsAfterInitialization方法中;
  7. 为上下文初始化Message源,(比如国际化处理) 这里没有过多深入;
  8. 初始化应用消息广播,初始化 applicationEventMulticaster ,判断使用自定义的还是默认的;
  9. 留给子类来初始化其它的bean;
  10. 在所有注册的bean中查找 ApplicationListener bean,注册到消息广播器中;
  11. 初始化剩下的单实例(非懒加载),这里会是涉及conversionService,LoadTimeWeaverAware,冻结BeanFactory,初始化Bean等操作;
  12. 完成刷新过程,包括 清除 下文级资源(例如扫描的元数据),通知生命周期处理器lifecycleProcessor并strat,同时publish Event发出ContextRefreshEvent通知别人;
  • 先来看prepareRefresh方法:
/**
 * 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.
	this.startupDate = System.currentTimeMillis();
    // 标志,指示是否已关闭此上下文
	this.closed.set(false);
    // 指示此上下文当前是否处于活动状态的标志
	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.
	// 对上下文环境中的任何属性源进行分类。
	initPropertySources();

	// Validate that all properties marked as required are resolvable:
	// see ConfigurablePropertyResolver#setRequiredProperties,

	//验证标示为必填的属性信息是否都有了 ConfigurablePropertyResolver#setRequiredProperties 方法
	getEnvironment().validateRequiredProperties();

	// Store pre-refresh ApplicationListeners...
	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...
	this.earlyApplicationEvents = new LinkedHashSet<>();
}

一眼望去,可能觉得这个方法没有做什么,其实这方法中除了Closed和Active,最重要的是initPropertySources和getEnvironment().validateRequiredProperties()方法;

  1. initPropertySources证符合Spring的开放式结构设计,给用户最大扩展Spring的能力。用户可以根据自身的需要重写initPropertySourece方法,并在方法中进行个性化的属性处理及设置。
  2. validateRequiredProperties则是对属性进行验证,那么如何验证呢?举个融合两句代码的小例子来理解。

例如现在有这样一个需求,工程在运行过程中用到的某个设置(例如VAR)是从系统环境变量中取得的,而如果用户没有在系统环境变量中配置这个参数,工程不会工作。这一要求也各种各样的解决办法,在Spring中可以这么做,可以直接修改Spring的源码,例如修改ClassPathXmlApplicationContext.当然,最好的办法是对源码进行扩展,可以自定义类:

public class MyClassPathXmlApplicationContext extends ClassPathXmlApplicationContext{
      public MyClassPathXmlApplicationContext(String.. configLocations){
            super(configLocations);
       }
       protected void initPropertySources(){
             //添加验证要求
             getEnvironment().setRequiredProterties("VAR");
       }
}

自定义了继承自ClassPathXmlApplicationContext的MyClassPathXmlApplicationContext,并重写了initPropertySources方法,在方法中添加了个性化需求,那么在验证的时候也就是程序走到getEnvironment().validateRequiredProperties()代码的时候,如果系统并没有检测到对应VAR的环境变量,将抛出异常。当然我们还需要在使用的时候替换掉原有的ClassPathXmlApplicationContext:

public static void main(Stirng[] args){
   ApplicationContext bf = new MyClassPathXmlApplicationContext("myTest.xml");
   User user = (User)bf.getBean("testBean");
   }

上述案例来源于:Spring源码深度解析(第二版)141页;

  • 接下来看一下obtainFreshBeanFactory方法,在这里初始化DefaultListAbleBeanFactory并解析xml:
/**
 * Tell the subclass to refresh the internal bean factory.
 * @return the fresh BeanFactory instance
 * @see #refreshBeanFactory()
 * @see #getBeanFactory()
 */
protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
	refreshBeanFactory();
	return getBeanFactory();
}

点击并拖拽以移动

/**
 * This implementation performs an actual refresh of this context's underlying
 * bean factory, shutting down the previous bean factory (if any) and
 * initializing a fresh bean factory for the next phase of the context's lifecycle.
 */
@Override
protected final void refreshBeanFactory() throws BeansException {
	if (hasBeanFactory()) {
		destroyBeans();
		closeBeanFactory();
	}
	try {
		// createBeanFactory方法直接新建一个DefaultListableBeanFactory,内部使用的是DefaultListableBeanFactory实例
		DefaultListableBeanFactory beanFactory = createBeanFactory();
		// 设置序列化id
		beanFactory.setSerializationId(getId());
		// 定制beanFactory工厂
		customizeBeanFactory(beanFactory);
		// 加载BeanDefinition
		loadBeanDefinitions(beanFactory);
		synchronized (this.beanFactoryMonitor) {
			// 使用全局变量记录BeanFactory
			this.beanFactory = beanFactory;
		}
	}
	catch (IOException ex) {
		throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
	}
}

点击并拖拽以移动

看一下上述方法都做了什么:

  1. 判断BeanFactory是否存在,如果存在则销毁所有Bean,然后关闭BeanFactory;

  2. 使用createBeanFactory方法直接新建一个DefaultListableBeanFactory,内部使用的是DefaultListableBeanFactory实例;

  3. 设置BeanFactory的设置序列化id

  4. 定制beanFactory工厂,也就是给allowBeanDefinitionOverriding(是否允许覆盖同名称的Bean)和allowCircularReferences(是否允许bean存在循环依赖),可通过setAllowBeanDefinitionOverriding和setAllowCircularReferences赋值,这里就可通过商编初始化方法中的initPropertySources方法来进行赋值;

  package lantao;
  import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MyApplicationContext extends ClassPathXmlApplicationContext {

	public MyApplicationContext(String... configLocations){
		super(configLocations);
	}
	protected void initPropertySources(){
		//添加验证要求
		getEnvironment().setRequiredProperties("VAR");
	
	            // 在这里添加set
		super.setAllowBeanDefinitionOverriding(true);
		super.setAllowCircularReferences(true);
	}
}
  1. 加载BeanDefinition,就是解析xml,循环解析,这里就不看了,如果不了解看作者上篇博客;
  • 下面看一下prepareBeanFactory方法源码:
/**
 * 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.
	// 设置BeanFactory的classLoader为当前context的classloader
	beanFactory.setBeanClassLoader(getClassLoader());

	// Spel语言解析器
	// 设置BeanFactory的表达式语言处理器 Spring3中增加了表达式语言的支持
	// 默认可以使用#{bean.xxx}的形式来调用相关属性值
	// 在Bean实例化的时候回调用 属性填充的方法(doCreateBean 方法中的 populateBean 方法中的 applyPropertyValues 方法中的 evaluateBeanDefinitionString ) 就会判断beanExpressionResolver是否为null操作
		beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));

	// 为BeanFactory增加一个默认的 PropertyEditor 这个主要对bean的属性等设置管理的一个工具 增加属性注册编辑器  例如:bean property 类型 date 则需要这里
	// beanFactory会在初始化 BeanWrapper(initBeanWrapper)中调用 ResourceEditorRegistrar 的 registerCustomEditors 方法
	beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));

	// Configure the bean factory with context callbacks.
	// ApplicationContextAwareProcessor --> postProcessBeforeInitialization
	// 注册 BeanPostProcessor  BeanPostProcessor 实在实例化前后执行的
	beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));

	// 设置几个忽略自动装配的接口 在addBeanPostProcessor方法中已经对下面几个类做了处理,他们就不是普通的bean了,所以在这里spring做bean的依赖的时候忽略
	// doCreateBean 方法中的 populateBean 方法中的 autowireByName 或 autowireByType 中的 unsatisfiedNonSimpleProperties 中的  !isExcludedFromDependencyCheck(pd) 判断,
	// 在属性填充的时候回判断依赖,如果存在下属几个则不做处理 对于下面几个类可以做implements操作
	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.
	// 设置几个注册依赖 参考spring源码深度解析原文:当注册依赖解析后,例如但那个注册了对BeanFactory。class的解析依赖后,当bean的属性注入的时候,一旦检测到属性为BeanFactory的类型变回将beanFactory 实例注入进去
	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.
	// 寄存器早期处理器,用于检测作为ApplicationListener的内部bean。
	beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(this));

	// Detect a LoadTimeWeaver and prepare for weaving, if found.
	// 增加了对AxpectJ的支持
	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.
	// 添加默认的系统环境bean
	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());
	}
}

不说废话,直接看这个方法都做了什么:

  1. 设置BeanFactory的classLoader为当前context的classloader;

  2. 设置BeanFactory的表达式语言处理器 Spring3中增加了Spel表达式语言的支持, 默认可以使用#{bean.xxx}的形式来调用相关属性值,

    在Bean实例化的时候回调用 属性填充的方法(doCreateBean 方法中的 populateBean 方法中的 applyPropertyValues 方法中的 evaluateBeanDefinitionString ) 就会判断beanExpressionResolver是否为null操作,如果不是则会使用Spel表达式规则解析

    <?xml version="1.0" encoding="UTF-8" ?>
    <beans
           xmlns="http://www.springframework.org/schema/beans"
           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
           xsi:schemaLocation="http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">
    
    	<bean id="testOneBean" class="lantao.bean.TestOneBean">
    		<property name="testTwoBean" value="#{testTWoBean}"/>
    	</bean>
    	
    	<bean id="testTWoBean" class="lantao.bean.TestTwoBean"/>
    
    	<!-- 上面 相当于 下边 -->
    
    	<bean id="testOneBean1" class="lantao.bean.TestOneBean">
    		<property name="testTwoBean" ref="testTWoBean1"/>
    	</bean>
    
    	<bean id="testTWoBean1" class="lantao.bean.TestTwoBean"/>
    
    </beans>
    
    1. 为BeanFactory增加一个默认的 PropertyEditor 这个主要对bean的属性等设置管理的一个工具 增加属性注册编辑器 例如:User类中 startDate 类型 date 但是xml property的value是2019-10-10,在启动的时候就会报错,类型转换不成功,这里可以使用继承PropertyEditorSupport这个类机型重写并注入即可使用;beanFactory会在初始化BeanWrapper (initBeanWrapper)中调用 ResourceEditorRegistrar 的 registerCustomEditors 方法进行初始化;
  3. 配置BeanPostProcessor,这里配置的是ApplicationContextAwareProcessor,上边我们说了,BeanPostProcessor是在初始化方法Init前后执行,看一下ApplicationContextAwareProcessor的Before和After方法:

@Override
   @Nullable
   public Object postProcessBeforeInitialization(final Object bean, String beanName) throws BeansException {
   	AccessControlContext acc = null;
   
   	// 该方法也会在 BeanFactory 实例化bean 中调用  doCreateBean --> initializeBean --> applyBeanPostProcessorsBeforeInitialization --> postProcessBeforeInitialization
   	// 如果实例化的类实现了 invokeAwareInterfaces 方法中的判断类 则会调用初始方法赋值
   	if (System.getSecurityManager() != null &&
   			(bean instanceof EnvironmentAware || bean instanceof EmbeddedValueResolverAware ||
   					bean instanceof ResourceLoaderAware || bean instanceof ApplicationEventPublisherAware ||
   					bean instanceof MessageSourceAware || bean instanceof ApplicationContextAware)) {
   		acc = this.applicationContext.getBeanFactory().getAccessControlContext();
   	}
   
   	if (acc != null) {
   		AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
   			invokeAwareInterfaces(bean);
   			return null;
   		}, acc);
   	}
   	else {
   		invokeAwareInterfaces(bean);
   	}
   		return bean;
   }
   private void invokeAwareInterfaces(Object bean) {
   	if (bean instanceof Aware) {
   		if (bean instanceof EnvironmentAware) {
   			((EnvironmentAware) bean).setEnvironment(this.applicationContext.getEnvironment());
   		}
   		if (bean instanceof EmbeddedValueResolverAware) {
   			((EmbeddedValueResolverAware) bean).setEmbeddedValueResolver(this.embeddedValueResolver);
   		}
   		if (bean instanceof ResourceLoaderAware) {
   			((ResourceLoaderAware) bean).setResourceLoader(this.applicationContext);
   		}
   		if (bean instanceof ApplicationEventPublisherAware) {
   			((ApplicationEventPublisherAware) bean).setApplicationEventPublisher(this.applicationContext);
   		}
   		if (bean instanceof MessageSourceAware) {
   			((MessageSourceAware) bean).setMessageSource(this.applicationContext);
   		}
   		if (bean instanceof ApplicationContextAware) {
   			((ApplicationContextAware) bean).setApplicationContext(this.applicationContext);
   		}
   	}
   }
   
   @Override
   public Object postProcessAfterInitialization(Object bean, String beanName) {
   	return bean;
   }

在Before方法中调用了invokeAwareInterfaces方法,在invokeAwareInterfaces方法中做了类型 instanceof 的判断,意思就是如果这个Bean实现了上述的Aware,则会初始会一下资源,比如实现了ApplicationContextAware,就会setApplicationContext,这里相信大家都用过,就不多说了;

  1. 设置几个忽略自动装配的接口 在addBeanPostProcessor方法中已经对下面几个类做了处理,他们就不是普通的bean了,所以在这里spring做bean的依赖的时候忽略,在doCreateBean 方法中的 populateBean 方法中的 autowireByName 或 autowireByType 中的 unsatisfiedNonSimpleProperties 中的 !isExcludedFromDependencyCheck(pd) 判断,如果存在则不做依赖注入了;

  2. 设置几个注册依赖 参考spring源码深度解析原文:当注册依赖解析后,例如当注册了对BeanFactory的解析依赖后,当bean的属性注入的时候,一旦检测到属性为BeanFactory的类型便会将beanFactory 实例注入进去;

  3. 添加BeanPostProcessor,这里是添加ApplicationListener,是寄存器早期处理器;这里可以看作者的源码测试,在spring-context的test测试类下有;

  4. 增加了对AxpectJ的支持

  5. 注册默认的系统环境bean,environment ,systemProperties,systemEnvironment;

  • 上述就是对BeanFactory的功能填充,下面看postProcessBeanFactory:

postProcessBeanFactory方法是个空方法,允许在上下文子类中对Bean工厂进行后处理,例如:可以在这里进行 硬编码形式的 BeanFactoryPostProcessor 调用 addBeanFactoryPostProcessor,进行addBeanFactoryPostProcessor或者是BeanPostProcessor;

  • 接下来看一下invokeBeanFactoryPostProcessors方法:
public static void invokeBeanFactoryPostProcessors(
		ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {

	// Invoke BeanDefinitionRegistryPostProcessors first, if any.
	Set<String> processedBeans = new HashSet<>();

	// 对 BeanDefinitionRegistry  类型处理
	if (beanFactory instanceof BeanDefinitionRegistry) {
		// 强转
		BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;

		// 普通的处理器
		List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>();

		//注册处理器
		List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>();


		// 这里就是硬编码处理 因为这里是从 getBeanFactoryPostProcessors()方法获取的 可以硬编码从addBeanFactoryPostProcessor()方法添加
		for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {

			if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {

				// 对于 BeanDefinitionRegistryPostProcessor 类型 在 BeanFactoryPostProcessor 的基础上还有自己的定义,需要先调用
				BeanDefinitionRegistryPostProcessor registryProcessor = (BeanDefinitionRegistryPostProcessor) postProcessor;

				// 执行 继承 BeanDefinitionRegistryPostProcessor 类的  postProcessBeanDefinitionRegistry 方法
				registryProcessor.postProcessBeanDefinitionRegistry(registry);

				registryProcessors.add(registryProcessor);
			}
			else {
				regularPostProcessors.add(postProcessor);
			}
		}
		//上边的For循环只是调用了硬编码的 BeanDefinitionRegistryPostProcessor 中的 postProcessBeanDefinitionRegistry 方法,
		// 但是 BeanFactoryPostProcessor 中的 postProcessBeanFactory 方法还没有调用,是在方法的最后一行
		// invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
		// invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory); 这两个方法中执行的,


		// 下面是自动处理器 获取类型是BeanDefinitionRegistryPostProcessor  beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false); 获取的


		// 当前注册处理器
		List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>();

		// First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.
		// 首先调用实现了 PriorityOrdered 的 BeanDefinitionRegistryPostProcessors
		String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);

		for (String ppName : postProcessorNames) {
			if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
				currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
				processedBeans.add(ppName);
			}
		}
		sortPostProcessors(currentRegistryProcessors, beanFactory);
		registryProcessors.addAll(currentRegistryProcessors);
		// 执行 BeanDefinitionRegistryPostProcessor类的postProcessBeanDefinitionRegistry方法
		invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
		currentRegistryProcessors.clear();

		// Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.
		// 下一个 ,调用实现 Ordered 的 BeanDefinitionRegistryPostProcessors
		postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
		for (String ppName : postProcessorNames) {
			if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {
				currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
				processedBeans.add(ppName);
			}
		}
		sortPostProcessors(currentRegistryProcessors, beanFactory);
		registryProcessors.addAll(currentRegistryProcessors);
		// 执行 BeanDefinitionRegistryPostProcessor类的postProcessBeanDefinitionRegistry方法
		invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
		currentRegistryProcessors.clear();

		// Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear.
		// 最后,调用所有其他BeanDefinitionRegistryPostProcessors,直到不再显示其他BeanDefinitionRegistryPostProcessors 无序的
		boolean reiterate = true;
		while (reiterate) {
			reiterate = false;
			postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
			for (String ppName : postProcessorNames) {
				if (!processedBeans.contains(ppName)) {
					currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
					processedBeans.add(ppName);
					reiterate = true;
				}
			}
			sortPostProcessors(currentRegistryProcessors, beanFactory);
			registryProcessors.addAll(currentRegistryProcessors);
			// 执行 BeanDefinitionRegistryPostProcessor类的postProcessBeanDefinitionRegistry方法
				invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
				currentRegistryProcessors.clear();
		}

		// 现在,调用到目前为止处理的所有处理器的  执行BeanFactoryPostProcessor 类的 postProcessBeanFactory 方法
		// 这里执行的是 硬编码 和 非硬编码(自动)的 BeanFactoryPostProcessor 类的 postProcessBeanFactory 方法 分为硬编码处理器 和 普通处理器
		invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
		invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
	}

	else {
		// 调用在上下文实例中注册的工厂处理器的postProcessBeanFactory方法。 就是硬编码 通过 addBeanFactoryPostProcessor 方法添加的BeanFactoryPostProcessor
			invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
	}




	// 自动处理 非硬编码 获取类型为是BeanFactoryPostProcessor    beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);

	// Do not initialize FactoryBeans here: We need to leave all regular beans
	// uninitialized to let the bean factory post-processors apply to them!
	String[] postProcessorNames =
			beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);

	// Separate between BeanFactoryPostProcessors that implement PriorityOrdered,
	// Ordered, and the rest.

	//  实现 priorityOrdered 的
	List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();

	// 实现 Ordered 的
	List<String> orderedPostProcessorNames = new ArrayList<>();

	// 无序的
	List<String> nonOrderedPostProcessorNames = new ArrayList<>();

	for (String ppName : postProcessorNames) {
		if (processedBeans.contains(ppName)) {
			// skip - already processed in first phase above
		}
		else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
			priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
		}
		else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
			orderedPostProcessorNames.add(ppName);
		}
		else {
			nonOrderedPostProcessorNames.add(ppName);
		}
	}

	// First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.
	sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
	invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);

	// Next, invoke the BeanFactoryPostProcessors that implement Ordered.
	List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<>();
	for (String postProcessorName : orderedPostProcessorNames) {
		orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
	}
	sortPostProcessors(orderedPostProcessors, beanFactory);
	invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);

	// Finally, invoke all other BeanFactoryPostProcessors.
	List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<>();
	for (String postProcessorName : nonOrderedPostProcessorNames) {
		nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
	}
	invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory);

	// Clear cached merged bean definitions since the post-processors might have
	// modified the original metadata, e.g. replacing placeholders in values...
	beanFactory.clearMetadataCache();
}

上述代码看起来很多,但是总计起来就三件事:

  1. 执行硬编码的和主动注入的BeanDefinitionRegistryPostProcessor,调用postProcessBeanDefinitionRegistry方法;
  2. 执行硬编码的和主动注入的BeanFactoryPostProcessor,调用postProcessBeanFactory方法;
  3. 自动注入的可继承Ordered排序,priorityOrdered排序或无序;

上述测试在作者的spring源码congtext中lantao包下有测试用例;

  • registerBeanPostProcessors方法源码:
public static void registerBeanPostProcessors(
		ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {

	String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);

	// Register BeanPostProcessorChecker that logs an info message when
	// a bean is created during BeanPostProcessor instantiation, i.e. when
	// a bean is not eligible for getting processed by all BeanPostProcessors.
	int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
	beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));

	// Separate between BeanPostProcessors that implement PriorityOrdered,
	// Ordered, and the rest.
	// 使用 priorityOrdered保证顺序
	List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();

	// MergedBeanDefinitionPostProcessor
	List<BeanPostProcessor> internalPostProcessors = new ArrayList<>();

	// 使用order保证顺序
	List<String> orderedPostProcessorNames = new ArrayList<>();

	// 无序的
	List<String> nonOrderedPostProcessorNames = new ArrayList<>();

	// 进行add操作
	for (String ppName : postProcessorNames) {
		if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
			BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
			priorityOrderedPostProcessors.add(pp);
			if (pp instanceof MergedBeanDefinitionPostProcessor) {
				internalPostProcessors.add(pp);
			}
		}
		else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
			orderedPostProcessorNames.add(ppName);
		}
		else {
			nonOrderedPostProcessorNames.add(ppName);
		}
	}

	// First, register the BeanPostProcessors that implement PriorityOrdered.
	// 首先 注册实现PriorityOrdered的 BeanPostProcessors 先排序PostProcessors
	sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
	registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);

	// Next, register the BeanPostProcessors that implement Ordered.
	// 下一个,注册实现Ordered的BeanPostProcessors
	List<BeanPostProcessor> orderedPostProcessors = new ArrayList<>();
	for (String ppName : orderedPostProcessorNames) {
		BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
		orderedPostProcessors.add(pp);
		if (pp instanceof MergedBeanDefinitionPostProcessor) {
			internalPostProcessors.add(pp);
		}
	}
	sortPostProcessors(orderedPostProcessors, beanFactory);
	registerBeanPostProcessors(beanFactory, orderedPostProcessors);

	// Now, register all regular BeanPostProcessors.
	// 现在,注册所有常规注册。无序的
	List<BeanPostProcessor> nonOrderedPostProcessors = new ArrayList<>();
	for (String ppName : nonOrderedPostProcessorNames) {
		BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
		nonOrderedPostProcessors.add(pp);
		if (pp instanceof MergedBeanDefinitionPostProcessor) {
			internalPostProcessors.add(pp);
		}
	}
	registerBeanPostProcessors(beanFactory, nonOrderedPostProcessors);

	// Finally, re-register all internal BeanPostProcessors.
	// 最后,注册所有MergedBeanDefinitionPostProcessor类型的BeanPostProcessor,并非重复注册。
	sortPostProcessors(internalPostProcessors, beanFactory);
	registerBeanPostProcessors(beanFactory, internalPostProcessors);

	// Re-register post-processor for detecting inner beans as ApplicationListeners,
	// moving it to the end of the processor chain (for picking up proxies etc).
	// 添加 ApplicationListener探测器
	beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
}

registerBeanPostProcessors方法代码还是比较长的,它和invokeBeanFactoryPostProcessors方法最主要的区别就是registerBeanPostProcessors只在这里注册,但不在这里调用,做的事情和invokeBeanFactoryPostProcessors差不多:

  1. 使用priorityOrdered,Ordered或无序保证顺序;
  2. 通过beanFactory.addBeanPostProcessor(postProcessor)进行注册;

很简单,代码篇幅很长,但是很好理解,这里可以简单看一下;

  • 接下来是initMessageSource方法,这里作者没有过多的看源码,后续补上吧.......(抱歉)

  • initApplicationEventMulticaster源码:

/**
 * Initialize the ApplicationEventMulticaster.
 * Uses SimpleApplicationEventMulticaster if none defined in the context.
 * @see org.springframework.context.event.SimpleApplicationEventMulticaster
 */
protected void initApplicationEventMulticaster() {
	ConfigurableListableBeanFactory beanFactory = getBeanFactory();
	// 使用自定义的 广播
	if (beanFactory.containsLocalBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME)) {
		this.applicationEventMulticaster =
				beanFactory.getBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, ApplicationEventMulticaster.class);
		if (logger.isTraceEnabled()) {
			logger.trace("Using ApplicationEventMulticaster [" + this.applicationEventMulticaster + "]");
		}
	}
	else {
		// 使用spring 默认的广播
		this.applicationEventMulticaster = new SimpleApplicationEventMulticaster(beanFactory);
		beanFactory.registerSingleton(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, this.applicationEventMulticaster);
		if (logger.isTraceEnabled()) {
			logger.trace("No '" + APPLICATION_EVENT_MULTICASTER_BEAN_NAME + "' bean, using " +
					"[" + this.applicationEventMulticaster.getClass().getSimpleName() + "]");
		}
	}
}

initApplicationEventMulticaster方法中主要就是判断是使用自定义的ApplicationEventMulticaster(广播器)还是使用呢Spring默认的SimpleApplicationEventMulticaster广播器;

  • onRefresh 方法是留个子类重写的,内容是空;

  • registerListeners方法:

/**
 * Add beans that implement ApplicationListener as listeners.
 * Doesn't affect other listeners, which can be added without being beans.
 */
protected void registerListeners() {
	// Register statically specified listeners first.
	// 注册 添加 ApplicationListener  这里通过硬编码 addApplicationListener 方法添加的
	for (ApplicationListener<?> listener : getApplicationListeners()) {
		getApplicationEventMulticaster().addApplicationListener(listener);
	}

	// Do not initialize FactoryBeans here: We need to leave all regular beans
	// uninitialized to let post-processors apply to them!
	// 注册 添加 ApplicationListener 这里是自动注册添加的
	String[] listenerBeanNames = getBeanNamesForType(ApplicationListener.class, true, false);
	for (String listenerBeanName : listenerBeanNames) {
			getApplicationEventMulticaster().addApplicationListenerBean(listenerBeanName);
	}

	// Publish early application events now that we finally have a multicaster...
	// 发布早期的事件
	Set<ApplicationEvent> earlyEventsToProcess = this.earlyApplicationEvents;
	this.earlyApplicationEvents = null;
	if (earlyEventsToProcess != null) {
		for (ApplicationEvent earlyEvent : earlyEventsToProcess) {
			getApplicationEventMulticaster().multicastEvent(earlyEvent);
		}
	}
}

registerListeners方法做了三件事情:

  1. 添加 ApplicationListener 这里通过硬编码 addApplicationListener 方法添加的;
  2. 添加 ApplicationListener 是通过自动注册添加的
  3. 发布早起事件
  • finishBeanFactoryInitialization方法源码:
/**
 * Finish the initialization of this context's bean factory,
 * initializing all remaining singleton beans.
 */
protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
	// Initialize conversion service for this context.
	// conversionService 用于类型转换 ,比如 String 转Date
	//判断BeanFactory中是否存在名称为“conversionService”且类型为ConversionService的Bean,如果存在则将其注入到beanFactory
	// 判断有无自定义属性转换服务接口,并将其初始化,我们在分析bean的属性填充过程中,曾经用到过该服务接口。在TypeConverterDelegate类的convertIfNecessary方法中
	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));
	}

	// Register a default embedded value resolver if no bean post-processor
	// (such as a PropertyPlaceholderConfigurer bean) registered any before:
	// at this point, primarily for resolution in annotation attribute values.
	if (!beanFactory.hasEmbeddedValueResolver()) {
		beanFactory.addEmbeddedValueResolver(strVal -> getEnvironment().resolvePlaceholders(strVal));
	}

	// Initialize LoadTimeWeaverAware beans early to allow for registering their transformers early.
	// 得到所有的实现了LoadTimeWeaverAware接口的子类名称,初始化它们
	// 如果有LoadTimeWeaverAware类型的bean则初始化,用来加载Spring Bean时织入第三方模块,如AspectJ,我们在后面详细讲解。
	String[] weaverAwareNames = beanFactory.getBeanNamesForType(LoadTimeWeaverAware.class, false, false);
	for (String weaverAwareName : weaverAwareNames) {
		getBean(weaverAwareName);
	}

	// Stop using the temporary ClassLoader for type matching.
	// 停止使用临时类加载器 就是在这里不让使用呢 ClassLoader 了
	beanFactory.setTempClassLoader(null);

	// Allow for caching all bean definition metadata, not expecting further changes.
	// 冻结所有bean定义,说明你注册的bean将不被修改或进行任何进一步的处理 就是不让改了 BeanDefinition
	beanFactory.freezeConfiguration();

	// Instantiate all remaining (non-lazy-init) singletons.
	// 初始化所有非懒加载的 单例 bean  调用你getBean方法
	beanFactory.preInstantiateSingletons();
}

finishBeanFactoryInitialization方法做了五件事情:

  1. 设置BeanFactory的conversionService,conversionService用于类型转换使用, 例如:User类中 startDate 类型 date 但是xml property的value是2019-10-10,在启动的时候就会报错,类型转换不成功,可以使用conversionService;书中170页有具体代码;
  2. 添加BeanFactory的addEmbeddedValueResolver,读取配置信息放到这里,可以通过EmbeddedValueResolverAware来获取,参考:https://www.cnblogs.com/winkey4986/p/7001173.html
  3. 得到所有的实现了LoadTimeWeaverAware接口的子类名称,初始化它们,用来加载Spring Bean时织入第三方模块,如AspectJ,我们在后面详细讲解。
  4. 停止使用临时类加载器 就是在这里不让使用呢 ClassLoader 了
  5. 冻结所有bean定义,说明你注册的bean将不被修改或进行任何进一步的处理 就是不让改了 BeanDefinition
  6. 初始化所有非懒加载的 单例 bean 调用你getBean方法,循环所有bean并实例化 条件是:单例,非Abstract 非懒加载
  • 最后的一个方法finishRefresh:
/**
 * Finish the refresh of this context, invoking the LifecycleProcessor's
 * onRefresh() method and publishing the
 * {@link org.springframework.context.event.ContextRefreshedEvent}.
 */
protected void finishRefresh() {
	// Clear context-level resource caches (such as ASM metadata from scanning).
	// 清除 下文级资源(例如扫描的元数据)。
	clearResourceCaches();
	
	// Initialize lifecycle processor for this context.
	// 在当前context中初始化 lifecycle
	// lifecycle 有自己的 start/ stop方法,实现此接口后spring保证在启动的时候调用start方法开始生命周期 关闭的时候调用 stop方法结束生命周期
	initLifecycleProcessor();

	// Propagate refresh to lifecycle processor first.
	// onRefresh 启动所有实现了 lifecycle 的方法
	getLifecycleProcessor().onRefresh();

	// Publish the final event.
	// 当ApplicationContext初始化完成发布后发布事件 处理后续事宜
	publishEvent(new ContextRefreshedEvent(this));

	// Participate in LiveBeansView MBean, if active.
	// 这里 没明白》。。
	LiveBeansView.registerApplicationContext(this);
}

finishRefresh方法是ApplicationContext初始化的最后一个方法了,他做了一些结尾的事情:

  1. 清除 下文级资源(例如扫描的元数据)。
  2. 在当前context中初始化 lifecycle,lifecycle 有自己的 start/ stop方法,实现此接口后spring保证在启动的时候调用start方法开始生命周期 关闭的时候调用 stop方法结束生命周期。
  3. onRefresh 启动所有实现了 lifecycle 的方法,调用了start方法。
  4. 当ApplicationContext初始化完成发布事件 处理后续事宜。
  5. LiveBeansView.registerApplicationContext(this)这个代码没有太明白,有大神可以留言;

至此ApplicationContext的源码就都已经分析完成了,其中有很多地方很难懂,大家可以对应着源码一起看,会好理解一些,如果其中有错误,欢迎大神指点,在下方留言。

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