上面講到，sPRing在查找到資源以后，在BeanDefinitionReader的loadBeanDefinitions（String location）方法中，接著就調用了int loadCount = loadBeanDefinitions(resources);
這個方法間接的調用了子類xmlBeanDifinitionReader的loadBeanDefinitions(EncodedResource encodedResource)方法：
[java] view plain copy <span style="font-size:12px;">/** * 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.getResource()); } Set<EncodedResource> currentResources = this.resourcesCurrentlyBeingLoaded.get(); if (currentResources == null) { currentResources = new HashSet<EncodedResource>(4); this.resourcesCurrentlyBeingLoaded.set(currentResources); } //當前的資源正在加載--我猜的 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()); } <span style="color:#ff0000;">return doLoadBeanDefinitions(inputSource, encodedResource.getResource());</span> } 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(); } } }</span>上述方法調用了doLoadBeanDefinitions(InputSource inputSource, Resource resource)方法：
[java] view plain copy /** * 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 */ protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource) throws BeanDefinitionStoreException { try { int validationMode = getValidationModeForResource(resource); <span style="color:#ff0000;">Document doc = this.documentLoader.loadDocument( inputSource, getEntityResolver(), this.errorHandler, validationMode, isNamespaceAware()); return registerBeanDefinitions(doc, resource); </span> } 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); } }
在上面的方法中將xml人間解析成了document對象，然后調用了registerBeanDefinitions(Document doc, Resource resource)方法：
[java] view plain copy /** * Register the bean definitions contained in the given DOM document. * Called by <code>loadBeanDefinitions</code>. * <p>Creates a new instance of the parser class and invokes * <code>registerBeanDefinitions</code> 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 { BeanDefinitionDocumentReader documentReader = createBeanDefinitionDocumentReader(); documentReader.setEnvironment(this.getEnvironment()); int countBefore = getRegistry().getBeanDefinitionCount(); <span style="color:#ff0000;">documentReader.registerBeanDefinitions(doc, createReaderContext(resource)); </span> return getRegistry().getBeanDefinitionCount() - countBefore; }在上面的方法中先創建了一個DocumentReader對象，然后調用DefaultBeanDifinitionDocumentReader的registerBeanDefinitions(Document doc, XmlReaderContext readerContext)方法，此方法調用了下面的方法
[java] view plain copy /** * Register each bean definition within the given root {@code <beans/>} element. * @throws IllegalStateException if {@code <beans profile="..."} attribute is present * and Environment property has not been set * @see #setEnvironment */ protected void doRegisterBeanDefinitions(Element root) { String profileSpec = root.getAttribute(PROFILE_ATTRIBUTE); if (StringUtils.hasText(profileSpec)) { Assert.state(this.environment != null, "environment property must not be null"); String[] specifiedProfiles = StringUtils.tokenizeToStringArray(profileSpec, BeanDefinitionParserDelegate.MULTI_VALUE_ATTRIBUTE_DELIMITERS); if (!this.environment.acceptsProfiles(specifiedProfiles)) { return; } } // 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 = createHelper(readerContext, root, parent); preProcessXml(root); <span style="color:#ff0000;">parseBeanDefinitions(root, this.delegate); /span> postProcessXml(root); this.delegate = parent; }在這個方法中創建了解析beandefinition的委托對象，實際上所有的解析都是在這個委托對象中完成的。
再看上面的方法間接調用了下面的DefaultBeanDifinitionDocumentReader方法：
[java] view plain copy /** * Process the given bean element, parsing the bean definition * and registering it with the registry. */ protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) { <span style="color:#ff0000;">BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);</span> if (bdHolder != null) { bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder); try { // Register the final decorated instance. <span style="color:#ff0000;">BeanDefinitionReaderUtils.registerBeanDefinition(bdHolder, getReaderContext().getRegistry()); /span> } catch (BeanDefinitionStoreException ex) { getReaderContext().error("Failed to register bean definition with name '" + bdHolder.getBeanName() + "'", ele, ex); } // Send registration event. getReaderContext().fireComponentRegistered(new BeanComponentDefinition(bdHolder)); } }上面紅色的的兩個方法一個是解析得到BeanDefinitionHolder對象，此對象持有BeanDefinition對象和bean的別名，id等信息。一個方法是注冊解析得到的BeanDefinition。
下面看看在BeanDefinitionParserDeleget類中的解析方法，
[html] view plain copy /** * Parses the supplied <code><bean></code> element. May return <code>null</code> * if there were errors during parse. Errors are reported to the * {@link org.springframework.beans.factory.parsing.ProblemReporter}. */ public BeanDefinitionHolder parseBeanDefinitionElement(Element ele) { return parseBeanDefinitionElement(ele, null); } /** * Parses the supplied <code><bean></code> element. May return <code>null</code> * if there were errors during parse. Errors are reported to the * {@link org.springframework.beans.factory.parsing.ProblemReporter}. */ public BeanDefinitionHolder parseBeanDefinitionElement(Element ele, BeanDefinition containingBean) { //這里取得<bean>中定義的 id name和 aliase的值 [html] view plain copy String id = ele.getAttribute(ID_ATTRIBUTE); = ele.getAttribute(NAME_ATTRIBUTE); [html] view plain copy List<String> aliases = new ArrayList<String>(); if (StringUtils.hasLength(nameAttr)) { String[] nameArr = StringUtils.tokenizeToStringArray(nameAttr, MULTI_VALUE_ATTRIBUTE_DELIMITERS); aliases.addAll(Arrays.asList(nameArr)); } String beanName = id; if (!StringUtils.hasText(beanName) && !aliases.isEmpty()) { beanName = aliases.remove(0); if (logger.isDebugEnabled()) { logger.debug("No XML 'id' specified - using '" + beanName + "' as bean name and " + aliases + " as aliases"); } } if (containingBean == null) { checkNameUniqueness(beanName, aliases, ele); } //這個方法是對bean元素的詳細解析 <span style="color:#ff0000;">AbstractBeanDefinition beanDefinition = parseBeanDefinitionElement(ele, beanName, containingBean); </span> if (beanDefinition != null) { if (!StringUtils.hasText(beanName)) { try { if (containingBean != null) { beanName = BeanDefinitionReaderUtils.generateBeanName( beanDefinition, this.readerContext.getRegistry(), true); } else { beanName = this.readerContext.generateBeanName(beanDefinition); // Register an alias for the plain bean class name, if still possible, // if the generator returned the class name plus a suffix. // This is expected for Spring 1.2/2.0 backwards compatibility. String beanClassName = beanDefinition.getBeanClassName(); if (beanClassName != null && beanName.startsWith(beanClassName) && beanName.length() > beanClassName.length() && !this.readerContext.getRegistry().isBeanNameInUse(beanClassName)) { aliases.add(beanClassName); } } if (logger.isDebugEnabled()) { logger.debug("Neither XML 'id' nor 'name' specified - " + "using generated bean name [" + beanName + "]"); } } catch (Exception ex) { error(ex.getMessage(), ele); return null; } } String[] aliasesArray = StringUtils.toStringArray(aliases); return new BeanDefinitionHolder(beanDefinition, beanName, aliasesArray); } return null; } 看看詳細的解析方法： parseBeanDefinitionElement( Element ele, String beanName, BeanDefinition containingBean)[html] view plain copy /** * Parse the bean definition itself, without regard to name or aliases. May return * <code>null</code> if problems occurred during the parsing of the bean definition. */ public AbstractBeanDefinition parseBeanDefinitionElement( Element ele, String beanName, BeanDefinition containingBean) { this.parseState.push(new BeanEntry(beanName)); //取得class name的定義，這里指讀取<bean>中設置的class的名字，記錄到BeanDefinition中，并不涉及對象的實例化過程，實例化實際上是在以來注入的時候完成的 String className = null; if (ele.hasAttribute(CLASS_ATTRIBUTE)) { className = ele.getAttribute(CLASS_ATTRIBUTE).trim(); } try { String parent = null; if (ele.hasAttribute(PARENT_ATTRIBUTE)) { parent = ele.getAttribute(PARENT_ATTRIBUTE); } <span style="color:#ff0000;">AbstractBeanDefinition bd = createBeanDefinition(className, parent); //對當前的Bean元素進行屬性解析，并設置description的信息 /span> parseBeanDefinitionAttributes(ele, beanName, containingBean, bd); bd.setDescription(DomUtils.getChildElementValueByTagName(ele, DESCRIPTION_ELEMENT)); //從名字可以看出。這里是對各種<bean>元素的信息進行解析的地方 parseMetaElements(ele, bd); parseLookupOverrideSubElements(ele, bd.getMethodOverrides()); parseReplacedMethodSubElements(ele, bd.getMethodOverrides()); //解析<bean>的構造函數 parseConstructorArgElements(ele, bd); //解析bean的property設置 [html] view plain copy <span style="color:#ff0000;">parsePropertyElements(ele, bd); span> parseQualifierElements(ele, bd); bd.setResource(this.readerContext.getResource()); bd.setSource(extractSource(ele)); return bd; } catch (ClassNotFoundException ex) { error("Bean class [" + className + "] not found", ele, ex); } catch (NoClassDefFoundError err) { error("Class that bean class [" + className + "] depends on not found", ele, err); } catch (Throwable ex) { error("Unexpected failure during bean definition parsing", ele, ex); } finally { this.parseState.pop(); } return null;上面主要關注紅色的兩個方法，一個是創建了BeanDefinition，一個是解析詳細的bean的屬性設置。
創建BeanDefinition是在調用了類BeanDefinitionReaderUtils.createBeanDefinition(parentName, className, this.readerContext.getBeanClassLoader());方法
[java] view plain copy /** * Create a new GenericBeanDefinition for the given parent name and class name, * eagerly loading the bean class if a ClassLoader has been specified. * @param parentName the name of the parent bean, if any * @param className the name of the bean class, if any * @param classLoader the ClassLoader to use for loading bean classes * (can be <code>null</code> to just register bean classes by name) * @return the bean definition * @throws ClassNotFoundException if the bean class could not be loaded */ public static AbstractBeanDefinition createBeanDefinition( String parentName, String className, ClassLoader classLoader) throws ClassNotFoundException { GenericBeanDefinition bd = new GenericBeanDefinition(); bd.setParentName(parentName); if (className != null) { if (classLoader != null) { bd.setBeanClass(ClassUtils.forName(className, classLoader)); } else { bd.setBeanClassName(className); } } return bd; }再看詳細解析bean的屬性定義的方法：
[html] view plain copy /** * Parse property sub-elements of the given bean element. */ public void parsePropertyElements(Element beanEle, BeanDefinition bd) { NodeList nl = beanEle.getChildNodes(); for (int i = 0; i < nl.getLength(); i++) { Node node = nl.item(i); if (isCandidateElement(node) && nodeNameEquals(node, PROPERTY_ELEMENT)) { <span style="color:#ff0000;">parsePropertyElement((Element) node, bd); /span> } } }
[java] view plain copy /** * Parse a property element. */ public void parsePropertyElement(Element ele, BeanDefinition bd) { //取得property的名字 [java] view plain copy String propertyName = ele.getAttribute(NAME_ATTRIBUTE); if (!StringUtils.hasLength(propertyName)) { error("Tag 'property' must have a 'name' attribute", ele); return; } this.parseState.push(new PropertyEntry(propertyName)); try { //如果在同一個Bean中已經有同名的property存在，則不進行解析，直接返回，也就是說，在同一個bean中的相同property設置，只有第一個起作用 [java] view plain copy if (bd.getPropertyValues().contains(propertyName)) { error("Multiple 'property' definitions for property '" + propertyName + "'", ele); return; //這里是解析property的地方，返回的對象對應對bean定義的property屬性設置的解析結果，這個解析結果會被封裝到PropertyValue中 [java] view plain copy <span style="color:#ff0000;">Object val = parsePropertyValue(ele, bd, propertyName); span> <span style="color:#009900;">PropertyValue pv = new PropertyValue(propertyName, val); parseMetaElements(ele, pv); pv.setSource(extractSource(ele)); bd.getPropertyValues().addPropertyValue(pv); span> } finally { this.parseState.pop(); } [java] view plain copy [java] view plain copy 下面這個方法是去的Property元素的值，也許是MAP,LIST SET或者其他ref對象 [python] view plain copy /** * Get the value of a property element. May be a list etc. * Also used for constructor arguments, "propertyName" being null in this case. */ public Object parsePropertyValue(Element ele, BeanDefinition bd, String propertyName) { String elementName = (propertyName != null) ? "<property> element for property '" + propertyName + "'" : "<constructor-arg> element"; // Should only have one child element: ref, value, list, etc. NodeList nl = ele.getChildNodes(); Element subElement = null; for (int i = 0; i < nl.getLength(); i++) { Node node = nl.item(i); if (node instanceof Element && !nodeNameEquals(node, DESCRIPTION_ELEMENT) && !nodeNameEquals(node, META_ELEMENT)) { // Child element is what we're looking for. if (subElement != null) { error(elementName + " must not contain more than one sub-element", ele); } else { subElement = (Element) node; } } } //這里判斷property的屬性是ref還是value，不允許同時是ref和value boolean hasRefAttribute = ele.hasAttribute(REF_ATTRIBUTE); boolean hasValueAttribute = ele.hasAttribute(VALUE_ATTRIBUTE); if ((hasRefAttribute && hasValueAttribute) || ((hasRefAttribute || hasValueAttribute) && subElement != null)) { error(elementName + " is only allowed to contain either 'ref' attribute OR 'value' attribute OR sub-element", ele); } //如果是ref，創建一個ref的數據對象RuntimeBeanReference 這個對象封裝 了ref的信息 if (hasRefAttribute) { String refName = ele.getAttribute(REF_ATTRIBUTE); if (!StringUtils.hasText(refName)) { error(elementName + " contains empty 'ref' attribute", ele); } RuntimeBeanReference ref = new RuntimeBeanReference(refName); ref.setSource(extractSource(ele)); return ref; } //如果是value，創建一個value的數據對象TypeStringValue，這個對象封裝了value信息 [python] view plain copy else if (hasValueAttribute) { TypedStringValue valueHolder = new TypedStringValue(ele.getAttribute(VALUE_ATTRIBUTE)); valueHolder.setSource(extractSource(ele)); return valueHolder; } //如果有子元素，對子元素解析，這里是對Map、List、Set、Property等元素解析 [python] view plain copy else if (subElement != null) { return parsePropertySubElement(subElement, bd); } else { // Neither child element nor "ref" or "value" attribute found. error(elementName + " must specify a ref or value", ele); return null; } }
上述解析過程可簡單的看成是
1、XmlBeanDefinitionReader讀取資源，
2、交給DefaultBeanDefinitionDocumentReader對象解析成Document對象，
3、然后DefaultBeanDefinitionDocumentReader對象委托給BeanDefinitionParserDelegate對象解析成BeanDefinitionHoler對象。
4、得到返回的BeanDefunitionHolder對象后調用BeanDefinitionReaderUtils.registerBeanDefinition(bdHolder, getReaderContext().getRegistry());方法進行注冊。
getReaderContext().getRegistry()這里得到的是DefaultListableBeanFactory。在AbstarctXmlapplicationContext的創建XmlBeandefinitionReader的地方可以看到：
[java] view plain copy XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);
DefaultListableBeanFactory中注冊的地方
[java] view plain copy public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition) throws BeanDefinitionStoreException { Assert.hasText(beanName, "Bean name must not be empty"); Assert.notNull(beanDefinition, "BeanDefinition must not be null"); if (beanDefinition instanceof AbstractBeanDefinition) { try { ((AbstractBeanDefinition) beanDefinition).validate(); } catch (BeanDefinitionValidationException ex) { throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName, "Validation of bean definition failed", ex); } } 注冊的地方需要同步，保持一致性 synchronized (this.beanDefinitionMap) { //這里檢查是不是有相同名字的BeanDefinition已經存在于IOC容器了，如果有相同的名字的BeanDefinition，但又不允許覆蓋，會拋出異常 [java] view plain copy Object oldBeanDefinition = this.beanDefinitionMap.get(beanName); if (oldBeanDefinition != null) { if (!this.allowBeanDefinitionOverriding) { throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName, "Cannot register bean definition [" + beanDefinition + "] for bean '" + beanName + "': There is already [" + oldBeanDefinition + "] bound."); } else { if (this.logger.isInfoEnabled()) { this.logger.info("Overriding bean definition for bean '" + beanName + "': replacing [" + oldBeanDefinition + "] with [" + beanDefinition + "]"); } } } else { //這是正常的注冊BeanDefinition的過程，把Bean的名字存入到BeanDefinitionNames的同時，beanName作為Map的Key，吧BeanDefinition作為value存入到IOC容器的BeanDefinitionMap中 [java] view plain copy this.beanDefinitionNames.add(beanName); this.frozenBeanDefinitionNames = null; } <span style="color:#ff0000;">this.beanDefinitionMap.put(beanName, beanDefinition); </span> } resetBeanDefinition(beanName); }
上面的代碼可以看出IOC容器是作為一個Map實現的。看看DefaultListableBeanFactory中有關容器定義
/** Map from dependency type to corresponding autowired value */ private final Map<Class<?>, Object> resolvableDependencies = new HashMap<Class<?>, Object>();
/** 這個就是存放BeanDefinition的容器MAP */ private final Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap<String, BeanDefinition>();
/** 存放單例的類的名字 */ private final Map<Class<?>, String[]> singletonBeanNamesByType = new ConcurrentHashMap<Class<?>, String[]>();
/** Map of non-singleton bean names keyed by bean class */ private final Map<Class<?>, String[]> nonSingletonBeanNamesByType = new ConcurrentHashMap<Class<?>, String[]>();
/** 容器中的beanName集合 */ private final List<String> beanDefinitionNames = new ArrayList<String>();
容器啟動時候完成的事情就已經全部分析完成了，類的實例化是在依賴注入或根據配置在容器啟動的時候完成的。容器啟動加載完成后，就可以再getBean方法調用的時候去使用了。
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