/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.transaction.config;

import org.w3c.dom.Element;

import org.springframework.aop.config.AopNamespaceUtils;
import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.beans.factory.config.RuntimeBeanReference;
import org.springframework.beans.factory.parsing.BeanComponentDefinition;
import org.springframework.beans.factory.parsing.CompositeComponentDefinition;
import org.springframework.beans.factory.support.RootBeanDefinition;
import org.springframework.beans.factory.xml.BeanDefinitionParser;
import org.springframework.beans.factory.xml.ParserContext;
import org.springframework.lang.Nullable;
import org.springframework.transaction.event.TransactionalEventListenerFactory;
import org.springframework.transaction.interceptor.BeanFactoryTransactionAttributeSourceAdvisor;
import org.springframework.transaction.interceptor.TransactionInterceptor;
import org.springframework.util.ClassUtils;


BeanDefinitionParser implementation that allows users to easily configure all the infrastructure beans required to enable annotation-driven transaction demarcation. 
By default, all proxies are created as JDK proxies. This may cause some problems if you are injecting objects as concrete classes rather than interfaces. To overcome this restriction you can set the 'proxy-target-class' attribute to 'true', which will result in class-based proxies being created. 
Author:
Juergen Hoeller, Rob Harrop, Chris Beams, Stephane Nicoll
Since:
2.0/**
 * {@link org.springframework.beans.factory.xml.BeanDefinitionParser
 * BeanDefinitionParser} implementation that allows users to easily configure
 * all the infrastructure beans required to enable annotation-driven transaction
 * demarcation.
 *
 * <p>By default, all proxies are created as JDK proxies. This may cause some
 * problems if you are injecting objects as concrete classes rather than
 * interfaces. To overcome this restriction you can set the
 * '{@code proxy-target-class}' attribute to '{@code true}', which
 * will result in class-based proxies being created.
 *
 * @author Juergen Hoeller
 * @author Rob Harrop
 * @author Chris Beams
 * @author Stephane Nicoll
 * @since 2.0
 */
class AnnotationDrivenBeanDefinitionParser implements BeanDefinitionParser {

	
Parses the <tx:annotation-driven/> tag. Will register an AutoProxyCreator with the container as necessary. /**
	 * 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.
/**
	 * 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);
			}
		}
	}

}