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Spring事务源码-TxNamespaceHandler

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作用

用于在启动的时候，初始化事务相关的parser，进而用于后面的aop

代码

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public class TxNamespaceHandler extends NamespaceHandlerSupport {

   static final String TRANSACTION_MANAGER_ATTRIBUTE = "transaction-manager";

   static final String DEFAULT_TRANSACTION_MANAGER_BEAN_NAME = "transactionManager";

   static String getTransactionManagerName(Element element) {
      return (element.hasAttribute(TRANSACTION_MANAGER_ATTRIBUTE) ?
            element.getAttribute(TRANSACTION_MANAGER_ATTRIBUTE) : DEFAULT_TRANSACTION_MANAGER_BEAN_NAME);
   }

   @Override
   public void init() {
      registerBeanDefinitionParser("advice", new TxAdviceBeanDefinitionParser());
      registerBeanDefinitionParser("annotation-driven", new AnnotationDrivenBeanDefinitionParser());
      registerBeanDefinitionParser("jta-transaction-manager", new JtaTransactionManagerBeanDefinitionParser());
   }

}

AnnotationDrivenBeanDefinitionParser

这个parser里面会将Transactional关键字进行解析，然后选择TransactionInterceptor

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class AnnotationDrivenBeanDefinitionParser implements BeanDefinitionParser {

	/**
	 * Parses the {@code <tx:annotation-driven/>} tag. Will
	 * {@link AopNamespaceUtils#registerAutoProxyCreatorIfNecessary register an AutoProxyCreator}
	 * with the container as necessary.
	 */
	@Override
	@Nullable
	public BeanDefinition parse(Element element, ParserContext parserContext) {
		registerTransactionalEventListenerFactory(parserContext);
		String mode = element.getAttribute("mode");
		if ("aspectj".equals(mode)) {
			// mode="aspectj"
			registerTransactionAspect(element, parserContext);
			if (ClassUtils.isPresent("javax.transaction.Transactional", getClass().getClassLoader())) {
				registerJtaTransactionAspect(element, parserContext);
			}
		}
		else {
			// mode="proxy"
			AopAutoProxyConfigurer.configureAutoProxyCreator(element, parserContext);
		}
		return null;
	}

	private void registerTransactionAspect(Element element, ParserContext parserContext) {
		String txAspectBeanName = TransactionManagementConfigUtils.TRANSACTION_ASPECT_BEAN_NAME;
		String txAspectClassName = TransactionManagementConfigUtils.TRANSACTION_ASPECT_CLASS_NAME;
		if (!parserContext.getRegistry().containsBeanDefinition(txAspectBeanName)) {
			RootBeanDefinition def = new RootBeanDefinition();
			def.setBeanClassName(txAspectClassName);
			def.setFactoryMethodName("aspectOf");
			registerTransactionManager(element, def);
			parserContext.registerBeanComponent(new BeanComponentDefinition(def, txAspectBeanName));
		}
	}

	private void registerJtaTransactionAspect(Element element, ParserContext parserContext) {
		String txAspectBeanName = TransactionManagementConfigUtils.JTA_TRANSACTION_ASPECT_BEAN_NAME;
		String txAspectClassName = TransactionManagementConfigUtils.JTA_TRANSACTION_ASPECT_CLASS_NAME;
		if (!parserContext.getRegistry().containsBeanDefinition(txAspectBeanName)) {
			RootBeanDefinition def = new RootBeanDefinition();
			def.setBeanClassName(txAspectClassName);
			def.setFactoryMethodName("aspectOf");
			registerTransactionManager(element, def);
			parserContext.registerBeanComponent(new BeanComponentDefinition(def, txAspectBeanName));
		}
	}

	private static void registerTransactionManager(Element element, BeanDefinition def) {
		def.getPropertyValues().add("transactionManagerBeanName",
				TxNamespaceHandler.getTransactionManagerName(element));
	}

	private void registerTransactionalEventListenerFactory(ParserContext parserContext) {
		RootBeanDefinition def = new RootBeanDefinition();
		def.setBeanClass(TransactionalEventListenerFactory.class);
		parserContext.registerBeanComponent(new BeanComponentDefinition(def,
				TransactionManagementConfigUtils.TRANSACTIONAL_EVENT_LISTENER_FACTORY_BEAN_NAME));
	}

	/**
	 * Inner class to just introduce an AOP framework dependency when actually in proxy mode.
	 */
	private static class AopAutoProxyConfigurer {

		public static void configureAutoProxyCreator(Element element, ParserContext parserContext) {
			AopNamespaceUtils.registerAutoProxyCreatorIfNecessary(parserContext, element);

			String txAdvisorBeanName = TransactionManagementConfigUtils.TRANSACTION_ADVISOR_BEAN_NAME;
			if (!parserContext.getRegistry().containsBeanDefinition(txAdvisorBeanName)) {
				Object eleSource = parserContext.extractSource(element);

				// Create the TransactionAttributeSource definition.
				RootBeanDefinition sourceDef = new RootBeanDefinition(
						"org.springframework.transaction.annotation.AnnotationTransactionAttributeSource");
				sourceDef.setSource(eleSource);
				sourceDef.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
				String sourceName = parserContext.getReaderContext().registerWithGeneratedName(sourceDef);

				// Create the TransactionInterceptor definition.
				RootBeanDefinition interceptorDef = new RootBeanDefinition(TransactionInterceptor.class);
				interceptorDef.setSource(eleSource);
				interceptorDef.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
				registerTransactionManager(element, interceptorDef);
				interceptorDef.getPropertyValues().add("transactionAttributeSource", new RuntimeBeanReference(sourceName));
				String interceptorName = parserContext.getReaderContext().registerWithGeneratedName(interceptorDef);

				// Create the TransactionAttributeSourceAdvisor definition.
				RootBeanDefinition advisorDef = new RootBeanDefinition(BeanFactoryTransactionAttributeSourceAdvisor.class);
				advisorDef.setSource(eleSource);
				advisorDef.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
				advisorDef.getPropertyValues().add("transactionAttributeSource", new RuntimeBeanReference(sourceName));
				advisorDef.getPropertyValues().add("adviceBeanName", interceptorName);
				if (element.hasAttribute("order")) {
					advisorDef.getPropertyValues().add("order", element.getAttribute("order"));
				}
				parserContext.getRegistry().registerBeanDefinition(txAdvisorBeanName, advisorDef);

				CompositeComponentDefinition compositeDef = new CompositeComponentDefinition(element.getTagName(), eleSource);
				compositeDef.addNestedComponent(new BeanComponentDefinition(sourceDef, sourceName));
				compositeDef.addNestedComponent(new BeanComponentDefinition(interceptorDef, interceptorName));
				compositeDef.addNestedComponent(new BeanComponentDefinition(advisorDef, txAdvisorBeanName));
				parserContext.registerComponent(compositeDef);
			}
		}
	}

}