spring声明式事务源码剖析（下）

对于spring声明式事务管理，我们已经剖析了一种，即应用spring配置xml文件，而这篇我们关注一下注解式事务管理。

对于注解式事务管理开启

<tx:annotation-driven transaction-manager="transactionManager"/>

它的解析(spring代码版本v.4.2.4.RELEASE):

1. TxNamespaceHandler.init

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

2. AnnotationDrivenBeanDefinitionParser.parse

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

   我们只看AopAutoProxyConfigurer.configureAutoProxyCreator(element, parserContext);

3. AnnotationDrivenBeanDefinitionParser$AopAutoProxyConfigurer.configureAutoProxyCreator(Element element, ParserContext parserContext)

   这个方法主要生成一个切面：
   注入org.springframework.transaction.annotation.AnnotationTransactionAttributeSource
   注入TransactionInterceptor 这个类我们已经很熟了；
   注入BeanFactoryTransactionAttributeSourceAdvisor生成切面,关于切面需要的pointcut则在该类里面直接实例化;
   

4. org.springframework.transaction.annotation.AnnotationTransactionAttributeSource

   public AnnotationTransactionAttributeSource() {
       this(true);
   }
   
   /**
    * Create a custom AnnotationTransactionAttributeSource, supporting
    * public methods that carry the {@code Transactional} annotation
    * or the EJB3 {@link javax.ejb.TransactionAttribute} annotation.
    * @param publicMethodsOnly whether to support public methods that carry
    * the {@code Transactional} annotation only (typically for use
    * with proxy-based AOP), or protected/private methods as well
    * (typically used with AspectJ class weaving)
    */
   public AnnotationTransactionAttributeSource(boolean publicMethodsOnly) {
       this.publicMethodsOnly = publicMethodsOnly;
       this.annotationParsers = new LinkedHashSet<TransactionAnnotationParser>(2);
       this.annotationParsers.add(new SpringTransactionAnnotationParser());
       if (jta12Present) {
           this.annotationParsers.add(new JtaTransactionAnnotationParser());
       }
       if (ejb3Present) {
           this.annotationParsers.add(new Ejb3TransactionAnnotationParser());
       }
   }
   

   对于 spring的Transactional的注解解析则由SpringTransactionAnnotationParser来解决，代码如下。

5. SpringTransactionAnnotationParser.parseTransactionAnnotation

   @Override
   public TransactionAttribute parseTransactionAnnotation(AnnotatedElement ae) {
       AnnotationAttributes attributes = AnnotatedElementUtils.getMergedAnnotationAttributes(ae, Transactional.class);
       if (attributes != null) {
           return parseTransactionAnnotation(attributes);
       }
       else {
           return null;
       }
   }
   

即所有注解了Transactional的方法或类或接口都被解析出来了，至此完.