Spring Bean生命周期-obtainFreshBeanFactory(三)-原创手记-慕课网

初始化ApplicationContext的时候，如果设置了自动刷新标志，会执行AbstractApplication的refresh方法，我们前篇文章提到了它的prepareRefresh方法，接下来执行的就是obtainFreshBeanFactory。

注释为：

告诉子类刷新内部的bean factory，返回新的BeanFactory实例

protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
		refreshBeanFactory();
		ConfigurableListableBeanFactory beanFactory = getBeanFactory();
		if (logger.isDebugEnabled()) {
			logger.debug("Bean factory for " + getDisplayName() + ": " + beanFactory);
		}
		return beanFactory;
	}

obtainFreshBeanFactory代码分析

刷新BeanFactory，关闭之前的bean factory，然后初始化新的bean factory

    
	protected final void refreshBeanFactory() throws BeansException {
	   // 锁beanFactoryMonitor，判断beanFactory是否为null 
		if (hasBeanFactory()) {
		   //如字面意思，销毁Bean，关闭BeanFactory
			destroyBeans();
			closeBeanFactory();
		}
		try {
		   // 创建BeanFactory，设置Id，自定义BeanFactory中设置了allowBeanDefinitionOverriding,allowCircularReferences
			DefaultListableBeanFactory beanFactory = createBeanFactory();
			beanFactory.setSerializationId(getId());
			customizeBeanFactory(beanFactory);
			
			//加载Bean的定义，比较重要的方法
			loadBeanDefinitions(beanFactory);
			
			// 赋值BeanFactory
			synchronized (this.beanFactoryMonitor) {
				this.beanFactory = beanFactory;
			}
		}
		catch (IOException ex) {
			throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
		}
	}

getBeanFactory主要是简单的返回 this.beanFactory 成员，没有做额外的处理

// 简单的返回beanFactory
public final ConfigurableListableBeanFactory getBeanFactory() {
		synchronized (this.beanFactoryMonitor) {
			if (this.beanFactory == null) {
				throw new IllegalStateException("BeanFactory not initialized or already closed - " +
						"call 'refresh' before accessing beans via the ApplicationContext");
			}
			return this.beanFactory;
		}
	}

loadBeanDefinitions分析

ApplicationContext中创建的beanFactory默认是DefaultListableBeanFactory。

protected DefaultListableBeanFactory createBeanFactory() {
		return new DefaultListableBeanFactory(getInternalParentBeanFactory());
	}

loadBeanDefinitions概览

// AbstractXMLApplicationContext.java

protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException {
		// Create a new XmlBeanDefinitionReader for the given BeanFactory.
		// 创建一个XmlBeanDefinitionReader，构造参数为BeanFactory
		XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);

		// Configure the bean definition reader with this context's
		// resource loading environment.
		// 配置beanDefinitionReader
		beanDefinitionReader.setEnvironment(this.getEnvironment());
		beanDefinitionReader.setResourceLoader(this);
		beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this));

		// Allow a subclass to provide custom initialization of the reader,
		// then proceed with actually loading the bean definitions.
		// 主要用来让子类覆盖此方法来实现对reader的自定义设置
		initBeanDefinitionReader(beanDefinitionReader);
		
		// 关键的方法，加载beanDefinitions
		loadBeanDefinitions(beanDefinitionReader);
	}

loadBeanDefinitions中，会根据我们实例化ApplicationContext传入的配置，来使用beanReader来加载。最终都是使用beanReader来从resource中加载bean

protected void loadBeanDefinitions(XmlBeanDefinitionReader reader) throws BeansException, IOException {
     // 获取配置的位置，然后加载 		// 第一次实例化时，一般加载的是configLocations
		Resource[] configResources = getConfigResources();
		if (configResources != null) {
			reader.loadBeanDefinitions(configResources);
		}

		String[] configLocations = getConfigLocations();
		if (configLocations != null) {
			reader.loadBeanDefinitions(configLocations);
		}
	}

beanReader加载配置的方法，看这之前可以先看下AbstractBeanDefinitionReader的构造方法，设置了resourceLoader与environment。

public int loadBeanDefinitions(String location, Set<Resource> actualResources) throws BeanDefinitionStoreException {
     // 获取资源加载器，ResourceLoader(PathMatchingResourcePatternResolver)
		ResourceLoader resourceLoader = getResourceLoader();
		if (resourceLoader == null) {
			throw new BeanDefinitionStoreException(
					"Cannot import bean definitions from location [" + location + "]: no ResourceLoader available");
		}

      //PathMatchingResourcePatternResolver实现了ResourcePatternResolver接口
		if (resourceLoader instanceof ResourcePatternResolver) {
			// Resource pattern matching available.
			// 可用资源样式匹配
			try {
				Resource[] resources = ((ResourcePatternResolver) resourceLoader).getResources(location);
				// 加载BeanDefinitions
				int loadCount = loadBeanDefinitions(resources);
				if (actualResources != null) {
					for (Resource resource : resources) {
						actualResources.add(resource);
					}
				}
				if (logger.isDebugEnabled()) {
					logger.debug("Loaded " + loadCount + " bean definitions from location pattern [" + location + "]");
				}
				return loadCount;
			}
			catch (IOException ex) {
				throw new BeanDefinitionStoreException(
						"Could not resolve bean definition resource pattern [" + location + "]", ex);
			}
		}
		
		else {
			// Can only load single resources by absolute URL.
			Resource resource = resourceLoader.getResource(location);
			int loadCount = loadBeanDefinitions(resource);
			if (actualResources != null) {
				actualResources.add(resource);
			}
			if (logger.isDebugEnabled()) {
				logger.debug("Loaded " + loadCount + " bean definitions from location [" + location + "]");
			}
			return loadCount;
		}
	}

XMLBeanDefinitionReader.loadBeanDefinitions(Resource resource)，从指定的XML文件中加载beanDefinitins。

public int loadBeanDefinitions(EncodedResource encodedResource) throws BeanDefinitionStoreException {
		Assert.notNull(encodedResource, "EncodedResource must not be null");
		if (logger.isInfoEnabled()) {
			logger.info("Loading XML bean definitions from " + encodedResource.getResource());
		}

      // 使用ThreadLocal保证线程安全
		Set<EncodedResource> currentResources = this.resourcesCurrentlyBeingLoaded.get();
		if (currentResources == null) {
			currentResources = new HashSet<EncodedResource>(4);
			this.resourcesCurrentlyBeingLoaded.set(currentResources);
		}
		
		// currentResources添加资源
		if (!currentResources.add(encodedResource)) {
			throw new BeanDefinitionStoreException(
					"Detected cyclic loading of " + encodedResource + " - check your import definitions!");
		}
		try {
			InputStream inputStream = encodedResource.getResource().getInputStream();
			try {
				InputSource inputSource = new InputSource(inputStream);
				if (encodedResource.getEncoding() != null) {
					inputSource.setEncoding(encodedResource.getEncoding());
				}
				
				// doLoadBeanDefinitions，
				return doLoadBeanDefinitions(inputSource, encodedResource.getResource());
			}
			finally {
				inputStream.close();
			}
		}
		catch (IOException ex) {
			throw new BeanDefinitionStoreException(
					"IOException parsing XML document from " + encodedResource.getResource(), ex);
		}
		finally {
			currentResources.remove(encodedResource);
			if (currentResources.isEmpty()) {
				this.resourcesCurrentlyBeingLoaded.remove();
			}
		}
	}

doLoadBeanDefinitions，实际上从XML文件中加载beanDefinition的类

protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource)
			throws BeanDefinitionStoreException {
		try {
			Document doc = doLoadDocument(inputSource, resource);
			return registerBeanDefinitions(doc, resource);
		}
		...
		// 捕捉异常
}

registerBeanDefinitions，从文档中(DOM对象)注册bean

// 返回值为本次总共加载了多少了bean
public int registerBeanDefinitions(Document doc, Resource resource) throws BeanDefinitionStoreException {
		BeanDefinitionDocumentReader documentReader = createBeanDefinitionDocumentReader();
		int countBefore = getRegistry().getBeanDefinitionCount();
		documentReader.registerBeanDefinitions(doc, createReaderContext(resource));
		return getRegistry().getBeanDefinitionCount() - countBefore;
	}

   //beanDefinition对象存储在beanDefinitionMap中
	public int getBeanDefinitionCount() {
		return this.beanDefinitionMap.size();
	}

真正的从XML文件中加载Bean过程比较重要，是Bean生命周期的关键部分，我们留在下次再讲。

TODO

ResourceEntityResolver
PathMatchingResourcePatternResolver
PathMatchingResourcePatternResolver.getResources方法，内部有查找资源的方法

总结

这里讲解了obtainBeanFactory方法，内部会先刷新BeanFactory，刷新的同时会进行初次的加载beanDfinition，内部涉及流程较多，下次一起看doRegisterBeanDefinitions方法。

Spring Bean生命周期-obtainFreshBeanFactory(三)原创

obtainFreshBeanFactory代码分析

loadBeanDefinitions分析

TODO

总结