Spring 事务源码解析

准备

• Spring版本：5.0.8

解析过程

标签解析分析

事务注解驱动标签 <tx:annotation-driven/> 解析，首先定位到 TxNamespaceHandler

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

// AnnotationDrivenBeanDefinitionParser
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;
}

// AnnotationDrivenBeanDefinitionParser
private static class AopAutoProxyConfigurer {
   

   public static void configureAutoProxyCreator(Element element, ParserContext parserContext) {
      // 注册了InfrastructureAdvisorAutoProxyCreator类 该类实现了BeanPostProcessor接口
      AopNamespaceUtils.registerAutoProxyCreatorIfNecessary(parserContext, element);

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

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

         // 创建TransactionInterceptor BeanDefinition
         RootBeanDefinition interceptorDef = new RootBeanDefinition(TransactionInterceptor.class);
         interceptorDef.setSource(eleSource);
         interceptorDef.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
         /**
          * 注册事务管理器
          *
          * 默认会寻找<tx:annotation-driven/>配置的transaction-manager属性作为事务管理器
          * 否则会寻找beanName为transactionManager的Bean作为事务管理器
          */
         registerTransactionManager(element, interceptorDef);
         // 为TransactionInterceptor添加TransactionAttributeSource引用
         interceptorDef.getPropertyValues().add("transactionAttributeSource", new RuntimeBeanReference(sourceName));
         String interceptorName = parserContext.getReaderContext().registerWithGeneratedName(interceptorDef);

         // 创建TransactionAttributeSourceAdvisor BeanDefinition
         RootBeanDefinition advisorDef = new RootBeanDefinition(BeanFactoryTransactionAttributeSourceAdvisor.class);
         advisorDef.setSource(eleSource);
         advisorDef.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
         // 为TransactionAttributeSourceAdvisor添加TransactionAttributeSource、TransactionInterceptor引用
         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);
      }
   }
}

注册 InfrastructureAdvisorAutoProxyCreator 类，查看该类继承图，发现该类实现了BeanPostProcessor 接口，在bean实例化时会调用其 postProcessAfterInitialization 方法，而其实现在父类 AbstractAutoProxyCreator 中

// AbstractAutoProxyCreator
public Object postProcessAfterInitialization(@Nullable Object bean, String beanName) throws BeansException {
   if (bean != null) {
      Object cacheKey = getCacheKey(bean.getClass(), beanName);
      if (!this.earlyProxyReferences.contains(cacheKey)) {
         return wrapIfNecessary(bean, beanName, cacheKey);
      }
   }
   return bean;
}

// AbstractAutoProxyCreator
protected Object wrapIfNecessary(Object bean, String beanName, Object cacheKey) {
   if (StringUtils.hasLength(beanName) && this.targetSourcedBeans.contains(beanName)) {
      return bean;
   }

   if (Boolean.FALSE.equals(this.advisedBeans.get(cacheKey))) {
      return bean;
   }
   // 如果是aop基础类或配置不需要代理 直接返回
   if (isInfrastructureClass(bean.getClass()) || shouldSkip(bean.getClass(), beanName)) {
      this.advisedBeans.put(cacheKey, Boolean.FALSE);
      return bean;
   }

   // 获取bean匹配的增强器
   Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(bean.getClass(), beanName, null);
   if (specificInterceptors != DO_NOT_PROXY) {
      this.advisedBeans.put(cacheKey, Boolean.TRUE);
      // 创建代理
      Object proxy = createProxy(
            bean.getClass(), beanName, specificInterceptors, new SingletonTargetSource(bean));
      this.proxyTypes.put(cacheKey, proxy.getClass());
      return proxy;
   }

   this.advisedBeans.put(cacheKey, Boolean.FALSE);
   return bean;
}

getAdvicesAndAdvisorsForBean 方法具体就是为了获取配置为增强器的bean，而在AopAutoProxyConfigurer.configureAutoProxyCreator方法注册的BeanFactoryTransactionAttributeSourceAdvisor 类实现了 Advisor，会被查找出来，另外被注入的两个也会被查找出来

// AbstractAdvisorAutoProxyCreator
protected Object[] getAdvicesAndAdvisorsForBean(
      Class<?> beanClass, String beanName, @Nullable TargetSource targetSource) {
   // 查找合适的增强器
   List<Advisor> advisors = findEligibleAdvisors(beanClass, beanName);
   if (advisors.isEmpty()) {
      return DO_NOT_PROXY;
   }
   return advisors.toArray();
}

// AbstractAdvisorAutoProxyCreator
protected List<Advisor> findEligibleAdvisors(Class<?> beanClass, String beanName) {
   // 寻找合适的增强器
   List<Advisor> candidateAdvisors = findCandidateAdvisors();
   // 确定增强器能否应用在bean上
   List<Advisor> eligibleAdvisors = findAdvisorsThatCanApply(candidateAdvisors, beanClass, beanName);
   extendAdvisors(eligibleAdvisors);
   if (!eligibleAdvisors.isEmpty()) {
      eligibleAdvisors = sortAdvisors(eligibleAdvisors);
   }
   return eligibleAdvisors;
}

// AbstractAdvisorAutoProxyCreator
protected List<Advisor> findAdvisorsThatCanApply(
      List<Advisor> candidateAdvisors, Class<?> beanClass, String beanName) {

   ProxyCreationContext.setCurrentProxiedBeanName(beanName);
   try {
      // 获取当前bean可用的增强器
      return AopUtils.findAdvisorsThatCanApply(candidateAdvisors, beanClass);
   }
   finally {
      ProxyCreationContext.setCurrentProxiedBeanName(null);
   }
}

// AopUtils
public static List<Advisor> findAdvisorsThatCanApply(List<Advisor> candidateAdvisors, Class<?> clazz) {
   if (candidateAdvisors.isEmpty()) {
      return candidateAdvisors;
   }
   List<Advisor> eligibleAdvisors = new LinkedList<>();
   // 首先处理引介增强是否可以应用在当前bean上
   for (Advisor candidate : candidateAdvisors) {
      if (candidate instanceof IntroductionAdvisor && canApply(candidate, clazz)) {
         eligibleAdvisors.add(candidate);
      }
   }
   boolean hasIntroductions = !eligibleAdvisors.isEmpty();
   for (Advisor candidate : candidateAdvisors) {
      if (candidate instanceof IntroductionAdvisor) {
         // 引介增强已处理
         continue;
      }
      // 判断当前增强是否可以应用在当前bean上
      if (canApply(candidate, clazz, hasIntroductions)) {
         eligibleAdvisors.add(candidate);
      }
   }
   return eligibleAdvisors;
}

// AopUtils
public static boolean canApply(Advisor advisor, Class<?> targetClass, boolean hasIntroductions) {
   // 判断引介增强是否匹配
   if (advisor instanceof IntroductionAdvisor) {
      return ((IntroductionAdvisor) advisor).getClassFilter().matches(targetClass);
   }
   else if (advisor instanceof PointcutAdvisor) {
      PointcutAdvisor pca = (PointcutAdvisor) advisor;
      // 判断是否可以应用在当前bean上
      return canApply(pca.getPointcut(), targetClass, hasIntroductions);
   }
   else {
      // It doesn't have a pointcut so we assume it applies.
      return true;
   }
}

// BeanFactoryTransactionAttributeSourceAdvisor
public Pointcut getPointcut() {
   return this.pointcut;
}

// AopUtils
public static boolean canApply(Pointcut pc, Class<?> targetClass, boolean hasIntroductions) {
   Assert.notNull(pc, "Pointcut must not be null");
   if (!pc.getClassFilter().matches(targetClass)) {
      return false;
   }

   /**
    * 获取方法匹配器
    * 
    * TransactionAttributeSourcePointcut的getMethodMatcher()方法