protected void autowireByType(
			String beanName, AbstractBeanDefinition mbd, BeanWrapper bw, MutablePropertyValues pvs) {

		TypeConverter converter = getCustomTypeConverter();
		if (converter == null) {
			converter = bw;
		}

		Set<String> autowiredBeanNames = new LinkedHashSet<>(4);
                // 过滤后的属性是在这里使用的
		String[] propertyNames = unsatisfiedNonSimpleProperties(mbd, bw);
		for (String propertyName : propertyNames) {
			try {
				PropertyDescriptor pd = bw.getPropertyDescriptor(propertyName);
				// Don't try autowiring by type for type Object: never makes sense,
				// even if it technically is a unsatisfied, non-simple property.
				if (Object.class != pd.getPropertyType()) {
					MethodParameter methodParam = BeanUtils.getWriteMethodParameter(pd);
					// Do not allow eager init for type matching in case of a prioritized post-processor.
					boolean eager = !(bw.getWrappedInstance() instanceof PriorityOrdered);
					DependencyDescriptor desc = new AutowireByTypeDependencyDescriptor(methodParam, eager);
					Object autowiredArgument = resolveDependency(desc, beanName, autowiredBeanNames, converter);
					if (autowiredArgument != null) {
						pvs.add(propertyName, autowiredArgument);
					}
					for (String autowiredBeanName : autowiredBeanNames) {
						registerDependentBean(autowiredBeanName, beanName);
						if (logger.isDebugEnabled()) {
							logger.debug("Autowiring by type from bean name '" + beanName + "' via property '" +
									propertyName + "' to bean named '" + autowiredBeanName + "'");
						}
					}
					autowiredBeanNames.clear();
				}
			}
			catch (BeansException ex) {
				throw new UnsatisfiedDependencyException(mbd.getResourceDescription(), beanName, propertyName, ex);
			}
		}
	}

protected void autowireByName(
			String beanName, AbstractBeanDefinition mbd, BeanWrapper bw, MutablePropertyValues pvs) {
                // 过滤后的属性是在这里使用的
		String[] propertyNames = unsatisfiedNonSimpleProperties(mbd, bw);
		for (String propertyName : propertyNames) {
			if (containsBean(propertyName)) {
				Object bean = getBean(propertyName);
				pvs.add(propertyName, bean);
				registerDependentBean(propertyName, beanName);
				if (logger.isDebugEnabled()) {
					logger.debug("Added autowiring by name from bean name '" + beanName +
							"' via property '" + propertyName + "' to bean named '" + propertyName + "'");
				}
			}
			else {
				if (logger.isTraceEnabled()) {
					logger.trace("Not autowiring property '" + propertyName + "' of bean '" + beanName +
							"' by name: no matching bean found");
				}
			}
		}
	}

第二步过滤后的属性是用来注入属性的无论是通过name还是通过type注入. 经过一系列的追踪我们证实了2.1.1节的功能实现.

2.2 XmlBeanDefinitionReader

构造方法解释完毕了,进入正题,xmlBeanFactory使用私有成员变量XmlBeanDefinitionReader去加载资源

 /**
	 * Create a new XmlBeanFactory with the given input stream,
	 * which must be parsable using DOM.
	 * @param resource XML resource to load bean definitions from
	 * @param parentBeanFactory parent bean factory
	 * @throws BeansException in case of loading or parsing errors
	 */
	public XmlBeanFactory(Resource resource, BeanFactory parentBeanFactory) throws BeansException {
		super(parentBeanFactory);
		this.reader.loadBeanDefinitions(resource);
	}

/**
	 * Load bean definitions from the specified XML file.
	 * @param resource the resource descriptor for the XML file
	 * @return the number of bean definitions found
	 * @throws BeanDefinitionStoreException in case of loading or parsing errors
	 */
	@Override
	public int loadBeanDefinitions(Resource resource) throws BeanDefinitionStoreException {
		return loadBeanDefinitions(new EncodedResource(resource));
	}

	/**
	 * Load bean definitions from the specified XML file.
	 * @param encodedResource the resource descriptor for the XML file,
	 * allowing to specify an encoding to use for parsing the file
	 * @return the number of bean definitions found
	 * @throws BeanDefinitionStoreException in case of loading or parsing errors
	 */
	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);
		}

		// 获得当前正在加载的资源
		Set<EncodedResource> currentResources = this.resourcesCurrentlyBeingLoaded.get();
		if (currentResources == null) {
			currentResources = new HashSet<>(4);
			this.resourcesCurrentlyBeingLoaded.set(currentResources);
		}
		// 如果当前正在加载的资源已经拥有该元素,报循环加载的错误
		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());
				}
				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();
			}
		}
	}

/**
	 * Actually load bean definitions from the specified XML file.
	 * @param inputSource the SAX InputSource to read from
	 * @param resource the resource descriptor for the XML file
	 * @return the number of bean definitions found
	 * @throws BeanDefinitionStoreException in case of loading or parsing errors
	 * @see #doLoadDocument
	 * @see #registerBeanDefinitions
	 */
	protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource)
			throws BeanDefinitionStoreException {
		try {
                        // 通过inputSource, resource获得文档对象
			Document doc = doLoadDocument(inputSource, resource);
			// 获取到document后注册BeanDefinition
			return registerBeanDefinitions(doc, resource);
		}
		catch (BeanDefinitionStoreException ex) {
			throw ex;
		}
		catch (SAXParseException ex) {
			throw new XmlBeanDefinitionStoreException(resource.getDescription(),
					"Line " + ex.getLineNumber() + " in XML document from " + resource + " is invalid", ex);
		}
		catch (SAXException ex) {
			throw new XmlBeanDefinitionStoreException(resource.getDescription(),
					"XML document from " + resource + " is invalid", ex);
		}
		catch (ParserConfigurationException ex) {
			throw new BeanDefinitionStoreException(resource.getDescription(),
					"Parser configuration exception parsing XML from " + resource, ex);
		}
		catch (IOException ex) {
			throw new BeanDefinitionStoreException(resource.getDescription(),
					"IOException parsing XML document from " + resource, ex);
		}
		catch (Throwable ex) {
			throw new BeanDefinitionStoreException(resource.getDescription(),
					"Unexpected exception parsing XML document from " + resource, ex);
		}
	}

/**
	 * Register the bean definitions contained in the given DOM document.
	 * Called by {@code loadBeanDefinitions}.
	 * <p>Creates a new instance of the parser class and invokes
	 * {@code registerBeanDefinitions} on it.
	 * @param doc the DOM document
	 * @param resource the resource descriptor (for context information)
	 * @return the number of bean definitions found
	 * @throws BeanDefinitionStoreException in case of parsing errors
	 * @see #loadBeanDefinitions
	 * @see #setDocumentReaderClass
	 * @see BeanDefinitionDocumentReader#registerBeanDefinitions
	 */
	public int registerBeanDefinitions(Document doc, Resource resource) throws BeanDefinitionStoreException {
                //1. 生成BeanDefinitionDocumentReader
		BeanDefinitionDocumentReader documentReader = createBeanDefinitionDocumentReader();
		// 返回注册列表中注册的bean的数量
		int countBefore = getRegistry().getBeanDefinitionCount();
                //2. 通过生成的BeanDefinitionDocumentReader注册beanDefinition
		documentReader.registerBeanDefinitions(doc, createReaderContext(resource));
		// 这里返回的是新注册的bean的数量
                //3. 返回最新的注册的bean的数量
		return getRegistry().getBeanDefinitionCount() - countBefore;
	}

private Class<? extends BeanDefinitionDocumentReader> documentReaderClass =
			DefaultBeanDefinitionDocumentReader.class;


/**
	 * Create the {@link BeanDefinitionDocumentReader} to use for actually
	 * reading bean definitions from an XML document.
	 * <p>The default implementation instantiates the specified "documentReaderClass".
	 * @see #setDocumentReaderClass
	 */
	protected BeanDefinitionDocumentReader createBeanDefinitionDocumentReader() {
		return BeanUtils.instantiateClass(this.documentReaderClass);
	}

documentReader.registerBeanDefinitions(doc, createReaderContext(resource));

/**
	 * Create the {@link XmlReaderContext} to pass over to the document reader.
	 */
	public XmlReaderContext createReaderContext(Resource resource) {
		return new XmlReaderContext(resource, this.problemReporter, this.eventListener,
				this.sourceExtractor, this, getNamespaceHandlerResolver());
	}

return getRegistry().getBeanDefinitionCount() - countBefore;

public class XmlBeanFactory extends DefaultListableBeanFactory {
        // 看XmlBeanDefinitionReader构造方法的参数this
	private final XmlBeanDefinitionReader reader = new XmlBeanDefinitionReader(this);


	/**
	 * Create a new XmlBeanFactory with the given resource,
	 * which must be parsable using DOM.
	 * @param resource XML resource to load bean definitions from
	 * @throws BeansException in case of loading or parsing errors
	 */
	public XmlBeanFactory(Resource resource) throws BeansException {
		this(resource, null);
	}

	/**
	 * Create a new XmlBeanFactory with the given input stream,
	 * which must be parsable using DOM.
	 * @param resource XML resource to load bean definitions from
	 * @param parentBeanFactory parent bean factory
	 * @throws BeansException in case of loading or parsing errors
	 */
	public XmlBeanFactory(Resource resource, BeanFactory parentBeanFactory) throws BeansException {
		super(parentBeanFactory);
		this.reader.loadBeanDefinitions(resource);
	}

}

	/**
	 * Create new XmlBeanDefinitionReader for the given bean factory.
	 * @param registry the BeanFactory to load bean definitions into,
	 * in the form of a BeanDefinitionRegistry
	 */
	public XmlBeanDefinitionReader(BeanDefinitionRegistry registry) {
		super(registry);
	}

/**
	 * This implementation parses bean definitions according to the "spring-beans" XSD
	 * (or DTD, historically).
	 * <p>Opens a DOM Document; then initializes the default settings
	 * specified at the {@code <beans/>} level; then parses the contained bean definitions.
	 */
	@Override
	public void registerBeanDefinitions(Document doc, XmlReaderContext readerContext) {
		this.readerContext = readerContext;
		logger.debug("Loading bean definitions");
		Element root = doc.getDocumentElement();
		doRegisterBeanDefinitions(root);
	}

/**
	 * Register each bean definition within the given root {@code <beans/>} element.
	 */
	protected void doRegisterBeanDefinitions(Element root) {
		// Any nested <beans> elements will cause recursion in this method. In
		// order to propagate and preserve <beans> default-* attributes correctly,
		// keep track of the current (parent) delegate, which may be null. Create
		// the new (child) delegate with a reference to the parent for fallback purposes,
		// then ultimately reset this.delegate back to its original (parent) reference.
		// this behavior emulates a stack of delegates without actually necessitating one.
		BeanDefinitionParserDelegate parent = this.delegate;
		this.delegate = createDelegate(getReaderContext(), root, parent);

		// 对配置文件进行处理
		if (this.delegate.isDefaultNamespace(root)) {
			String profileSpec = root.getAttribute(PROFILE_ATTRIBUTE);
			if (StringUtils.hasText(profileSpec)) {
				String[] specifiedProfiles = StringUtils.tokenizeToStringArray(
						profileSpec, BeanDefinitionParserDelegate.MULTI_VALUE_ATTRIBUTE_DELIMITERS);
                        // 主要逻辑就是判断这个配置文件是否是允许存在,不存在则 return,不再浪费时间解析了
				if (!getReaderContext().getEnvironment().acceptsProfiles(specifiedProfiles)) {
					if (logger.isInfoEnabled()) {
						logger.info("Skipped XML bean definition file due to specified profiles [" + profileSpec +
								"] not matching: " + getReaderContext().getResource());
					}
					return;
				}
			}
		}
		/*解析前处理,该方法为空实现*/
		preProcessXml(root);
		/*解析bean的定义*/
		parseBeanDefinitions(root, this.delegate);
		/*解析后处理,该方法为空实现*/
		postProcessXml(root);

		this.delegate = parent;
	}

<!-- 开发环境配置文件 -->
  <beans profile="development">
    <context:property-placeholder location="/WEB-INF/test-orm.properties" />
  </beans>
 
  <!-- 本地环境配置文件 -->
  <beans profile="test">
    <context:property-placeholder location="/WEB-INF/local-orm.properties" />
  </beans>


<!--在web.xml中添加-->
<context-param>
   <param-name>spring.profiles.default</param-name>
   <param-value>development</param-value>
</context-param>

/**
	 * Parse the elements at the root level in the document:
	 * "import", "alias", "bean".
	 *
	 * @param root the DOM root element of the document
	 */
	protected void parseBeanDefinitions(Element root, BeanDefinitionParserDelegate delegate) {
		if (delegate.isDefaultNamespace(root)) {
			NodeList nl = root.getChildNodes();
			for (int i = 0; i < nl.getLength(); i++) {
				Node node = nl.item(i);
				if (node instanceof Element) {
					Element ele = (Element) node;
					if (delegate.isDefaultNamespace(ele)) {
						// 解析默认标签
						parseDefaultElement(ele, delegate);
					} else {
						// 解析自定义标签
						delegate.parseCustomElement(ele);
					}
				}
			}
		} else {
			delegate.parseCustomElement(root);
		}
	}

<bean  >

<tx:annotation-driven>

	private void parseDefaultElement(Element ele, BeanDefinitionParserDelegate delegate) {
                 // import 标签
		if (delegate.nodeNameEquals(ele, IMPORT_ELEMENT)) {
			importBeanDefinitionResource(ele);
		} 
                  // alias标签
                  else if (delegate.nodeNameEquals(ele, ALIAS_ELEMENT)) {
			processAliasRegistration(ele);
		} 
                  //bean标签
                  else if (delegate.nodeNameEquals(ele, BEAN_ELEMENT)) {
			processBeanDefinition(ele, delegate);
		} 
                  //beans标签
                  else if (delegate.nodeNameEquals(ele, NESTED_BEANS_ELEMENT)) {
			// recurse
			doRegisterBeanDefinitions(ele);
		}
	}

/**
	 * Process the given bean element, parsing the bean definition
	 * and registering it with the registry.
	 */
	protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {
		/*
		* 首先委托BeanDefinitionDelegate 类的parseBeanDefinitionElement 方法进行元素解析，
			返回BeanDefinitionHolder 类型的实例bdHolder ，经过这个方法后，bdHolder 实例已经包含我
			们配置文件中配置的各种属性了，例如class 、name、id 、alias 之类的属性
		* */
		BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);
		if (bdHolder != null) {
			/*
			* 当返回的bdHolder 不为空的情况下若存在默认标签的子节点下再有自定义属性，还需要
				再次对自定义标签进行解析
			* */
			bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder);
			try {
				// Register the final decorated instance.
				/*
				* 解析完成后，需要对解析后的bdHolder 进行注册，同样，注册操作委托给了
				* BeanDefinitionReaderUtils的registerBeanDefinition方法
				* */
				BeanDefinitionReaderUtils.registerBeanDefinition(bdHolder, getReaderContext().getRegistry());
			} catch (BeanDefinitionStoreException ex) {
				getReaderContext().error("Failed to register bean definition with name '" +
						bdHolder.getBeanName() + "'", ele, ex);
			}
			// Send registration event.
			getReaderContext().fireComponentRegistered(new BeanComponentDefinition(bdHolder));
		}
	}