Spring IOC registerBeanDefinition
IOC 是Spring的核心,我们以编程方式使用DefaultListableBeanFactory,尽管在现实的编码过程中几乎不会这种原始的方式,但是作为了解Spring IOC 实现还是很有必要的。
//创建IOC配置的抽象资源 ClassPathResource resource=new ClassPathResource("client.xml"); //创建一个BeanFactory DefaultListableBeanFactory beanFactory=new DefaultListableBeanFactory(); //创建一个BeanDefinition读区器 XmlBeanDefinitionReader reader=new XmlBeanDefinitionReader(beanFactory); //从定义好的资源位置读区配置信息 reader.loadBeanDefinitions(resource);
通过上述步骤我们就创建好了一个beanFactory.在XmlBeanDefinitionReader中实际加载BeanDefinition的方法是doLoadBeanDefinitions,在该方法中首先是将资源文件转换为Document对象,然后注册BeanDefinition
/** * 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 { Document doc = doLoadDocument(inputSource, resource); return registerBeanDefinitions(doc, resource); } catch (BeanDefinitionStoreException ex) { throw 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 { //创建一个BeanDefinitionDocumentReader 实例 BeanDefinitionDocumentReader documentReader = createBeanDefinitionDocumentReader(); //获取当前BeanFactory中的beans数量 int countBefore = getRegistry().getBeanDefinitionCount(); //注册beanDefinition documentReader.registerBeanDefinitions(doc, createReaderContext(resource)); //返回本次注册bean的数量 return getRegistry().getBeanDefinitionCount() - countBefore; }
在DefaultBeanDefinitionDocumentReader中注册bean的代码如下:
/** * Register each bean definition within the given root {@code <beans/>} element. */ protected void doRegisterBeanDefinitions(Element root) { BeanDefinitionParserDelegate parent = this.delegate; this.delegate = createDelegate(getReaderContext(), root, parent); 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); if (!getReaderContext().getEnvironment().acceptsProfiles(specifiedProfiles)) { return; } } } //前置处理 preProcessXml(root); //解析BeanDefinition parseBeanDefinitions(root, this.delegate); //后置处理 postProcessXml(root); this.delegate = parent; }
/** * 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)) { parseDefaultElement(ele, delegate); } else { delegate.parseCustomElement(ele); } } } } else { delegate.parseCustomElement(root); } } private void parseDefaultElement(Element ele, BeanDefinitionParserDelegate delegate) { if (delegate.nodeNameEquals(ele, IMPORT_ELEMENT)) { importBeanDefinitionResource(ele); } else if (delegate.nodeNameEquals(ele, ALIAS_ELEMENT)) { processAliasRegistration(ele); } else if (delegate.nodeNameEquals(ele, BEAN_ELEMENT)) { processBeanDefinition(ele, delegate); } else if (delegate.nodeNameEquals(ele, NESTED_BEANS_ELEMENT)) { // recurse doRegisterBeanDefinitions(ele); } }
对于默认空间的bean的解析处理如下:
protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) { BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele); if (bdHolder != null) { bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder); try { // Register the final decorated instance. 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)); } }
通过BeanDefinitionReaderUtils.registerBeanDefinition注册beanDefinition
/** * Register the given bean definition with the given bean factory. * @param definitionHolder the bean definition including name and aliases * @param registry the bean factory to register with * @throws BeanDefinitionStoreException if registration failed */ public static void registerBeanDefinition( BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry) throws BeanDefinitionStoreException { // Register bean definition under primary name. String beanName = definitionHolder.getBeanName(); registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition()); // Register aliases for bean name, if any. String[] aliases = definitionHolder.getAliases(); if (aliases != null) { for (String alias : aliases) { registry.registerAlias(beanName, alias); } } }
@Override 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); } } BeanDefinition oldBeanDefinition; oldBeanDefinition = this.beanDefinitionMap.get(beanName); if (oldBeanDefinition != null) { if (!isAllowBeanDefinitionOverriding()) { throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName, "Cannot register bean definition [" + beanDefinition + "] for bean '" + beanName + "': There is already [" + oldBeanDefinition + "] bound."); } else if (oldBeanDefinition.getRole() < beanDefinition.getRole()) { // e.g. was ROLE_APPLICATION, now overriding with ROLE_SUPPORT or ROLE_INFRASTRUCTURE if (this.logger.isWarnEnabled()) { this.logger.warn("Overriding user-defined bean definition for bean '" + beanName + "' with a framework-generated bean definition: replacing [" + oldBeanDefinition + "] with [" + beanDefinition + "]"); } } else if (!beanDefinition.equals(oldBeanDefinition)) { if (this.logger.isInfoEnabled()) { this.logger.info("Overriding bean definition for bean '" + beanName + "' with a different definition: replacing [" + oldBeanDefinition + "] with [" + beanDefinition + "]"); } } else { if (this.logger.isDebugEnabled()) { this.logger.debug("Overriding bean definition for bean '" + beanName + "' with an equivalent definition: replacing [" + oldBeanDefinition + "] with [" + beanDefinition + "]"); } } } else { //向beanDefinitionNames list中添加beanName this.beanDefinitionNames.add(beanName); this.manualSingletonNames.remove(beanName); this.frozenBeanDefinitionNames = null; } //向beanDefinitionMap中添加beanDefiniton this.beanDefinitionMap.put(beanName, beanDefinition); if (oldBeanDefinition != null || containsSingleton(beanName)) { resetBeanDefinition(beanName); } }