Spring提取@Transactional事务注解的源码解析

声明：本文是自己在学习spring注解事务处理源代码时所留下的笔记； 难免有错误，敬请读者谅解！！！

1、事务注解标签

<tx:annotation-driven />

2、tx 命名空间解析器 
事务tx命名空间解析器TxNamespaceHandler 
org.springframework.transaction.config.TxNamespaceHandler#init

3、AnnotationDrivenBeanDefinitionParser#parse 解析事务标签

（1）、以下方法的核心逻辑主要是选择是否使用 Aspect 方式实现代理，默认方式为 JDK 的动态代理。 
org.springframework.transaction.config.AnnotationDrivenBeanDefinitionParser#parse

public BeanDefinition parse(Element element, ParserContext parserContext) {
    String mode = element.getAttribute("mode");
    if ("aspectj".equals(mode)) {
        // mode="aspectj"
        registerTransactionAspect(element, parserContext);
    }
    else {
        // mode="proxy"   注意 AopAutoProxyConfigurer 为当前内的内部类
        AopAutoProxyConfigurer.configureAutoProxyCreator(element, parserContext);
    }
    return null;
}

（2）、进入如下方法，该方法的核心逻辑通过硬编码的方式配置 Aop 动态代理的解析器 
AopAutoProxyConfigurer#configureAutoProxyCreator 
通过硬编码，Spring 为我们定义了如下的 Spring BeanDefinition 对象 
(a)、AnnotationTransactionAttributeSource.class 事务注解属性解析器BeanDefinition 对象。 
AnnotationTransactionAttributeSource 构造方法会初始化：

public AnnotationTransactionAttributeSource() {
        this(true);
}

public AnnotationTransactionAttributeSource(boolean publicMethodsOnly) {
    this.publicMethodsOnly = publicMethodsOnly;
    this.annotationParsers = new LinkedHashSet<TransactionAnnotationParser>(2);
    this.annotationParsers.add(new SpringTransactionAnnotationParser());// @Transactional 注解解析器
    if (ejb3Present) {
        this.annotationParsers.add(new Ejb3TransactionAnnotationParser());// Ejb 解析器
    }

(b)、TransactionInterceptor.class 事务拦截器BeanDefinition 对象 

(c)、BeanFactoryTransactionAttributeSourceAdvisor.class 事务切面解析器 

(d)、TransactionInterceptor.class 事务拦截器BeanDefinition 对象 

(e)、容易忽略的第一行代码：AopNamespaceUtils.registerAutoProxyCreatorIfNecessary(parserContext, element); 在这个方法内部 Spring 为我们的注入了：InfrastructureAdvisorAutoProxyCreator.class 

private static class AopAutoProxyConfigurer {

    public static void configureAutoProxyCreator(Element element, ParserContext parserContext) {

        // 非常重要的一行代码，在这个里面注册了：InfrastructureAdvisorAutoProxyCreator.class 该类实现了Spring BeanProcessor 的扩展接口
        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(AnnotationTransactionAttributeSource.class);// 事务注解解析器
            sourceDef.setSource(eleSource);
            sourceDef.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
            String sourceName = parserContext.getReaderContext().registerWithGeneratedName(sourceDef);

            // Create the TransactionInterceptor definition.
            RootBeanDefinition interceptorDef = new RootBeanDefinition(TransactionInterceptor.class);//事务拦截器
            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);//事务切面解析器
            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);
        }
    }
}

4、Spring Bean 实例化创建代理对象 
（a）、AbstractAutowireCapableBeanFactory#initializeBean(Java.lang.String, java.lang.Object, org.springframework.beans.factory.support.RootBeanDefinition)

（b）、AbstractAutoProxyCreator#postProcessAfterInitialization 

还记得上面我们提到的 InfrastructureAdvisorAutoProxyCreator 的类图吧，最后我们的 @Transactional 注解的类会执行该类中的 postProcessAfterInitialization 方法

（c）、Bean 的初始化后置处理，通过注释可以了解到，当前方法处理后会返回一个 bean 的代理对象

/**
 * Create a proxy with the configured interceptors if the bean is
 * identified as one to proxy by the subclass.
 * @see #getAdvicesAndAdvisorsForBean
 */
public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
    if (bean != null) {
        Object cacheKey = getCacheKey(bean.getClass(), beanName);
        if (!this.earlyProxyReferences.containsKey(cacheKey)) {
            return wrapIfNecessary(bean, beanName, cacheKey);// 创建代理类的核心方法
        }
    }
    return bean;
}

（d）、AbstractAutoProxyCreator#wrapIfNecessary

protected Object wrapIfNecessary(Object bean, String beanName, Object cacheKey) {
    if (beanName != null && this.targetSourcedBeans.containsKey(beanName)) {
        return bean;
    }
    if (Boolean.FALSE.equals(this.advisedBeans.get(cacheKey))) {
        return bean;
    }
    if (isInfrastructureClass(bean.getClass()) || shouldSkip(bean.getClass(), beanName)) {
        this.advisedBeans.put(cacheKey, Boolean.FALSE);
        return bean;
    }

    // Create proxy if we have advice.   获取切面   获取的过程是一个非常复杂的过程
    Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(bean.getClass(), beanName, null);
    if (specificInterceptors != DO_NOT_PROXY) {
        this.advisedBeans.put(cacheKey, Boolean.TRUE);

        // 创建代理对象，默认的情况下会使用 JDK 的动态代理接口创建代理对象
        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;
}

（c）、获取到的事务切面 

(d)、事务切面获取逻辑 

(e)、委托 ProxyFactory 创建代理对象

protected Object createProxy(
        Class<?> beanClass, String beanName, Object[] specificInterceptors, TargetSource targetSource) {

    ProxyFactory proxyFactory = new ProxyFactory();
    // Copy our properties (proxyTargetClass etc) inherited from ProxyConfig.
    proxyFactory.copyFrom(this);

    if (!shouldProxyTargetClass(beanClass, beanName)) {
        // Must allow for introductions; can't just set interfaces to
        // the target's interfaces only.
        Class<?>[] targetInterfaces = ClassUtils.getAllInterfacesForClass(beanClass, this.proxyClassLoader);
        for (Class<?> targetInterface : targetInterfaces) {
            proxyFactory.addInterface(targetInterface);
        }
    }

    Advisor[] advisors = buildAdvisors(beanName, specificInterceptors);
    for (Advisor advisor : advisors) {
        proxyFactory.addAdvisor(advisor);
    }

    proxyFactory.setTargetSource(targetSource);
    customizeProxyFactory(proxyFactory);

    proxyFactory.setFrozen(this.freezeProxy);
    if (advisorsPreFiltered()) {
        proxyFactory.setPreFiltered(true);
    }

    // 最终会使用：JdkDynamicAopProxy  创建事务的Aop 代理对象
    return proxyFactory.getProxy(this.proxyClassLoader);
}

(f)、最终生成代理对象 

5、代理类执行 
JdkDynamicAopProxy#invoke

public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
    MethodInvocation invocation;
    Object oldProxy = null;
    boolean setProxyContext = false;

    TargetSource targetSource = this.advised.targetSource;
    Class<?> targetClass = null;
    Object target = null;

    try {
        // 如果目标方法没有实现equals
        if (!this.equalsDefined && AopUtils.isEqualsMethod(method)) {
            // The target does not implement the equals(Object) method itself.
            return equals(args[0]);
        }
        // 如果目标方法没有实现hashcode
        if (!this.hashCodeDefined && AopUtils.isHashCodeMethod(method)) {
            // The target does not implement the hashCode() method itself.
            return hashCode();
        }
        // 根据代理对象的配置来调用服务
        if (!this.advised.opaque && method.getDeclaringClass().isInterface() &&
                method.getDeclaringClass().isAssignableFrom(Advised.class)) {
            // Service invocations on ProxyConfig with the proxy config...
            return AopUtils.invokeJoinpointUsingReflection(this.advised, method, args);
        }

        Object retVal;

        if (this.advised.exposeProxy) {
            // Make invocation available if necessary.
            oldProxy = AopContext.setCurrentProxy(proxy);
            setProxyContext = true;
        }

        // May be null. Get as late as possible to minimize the time we "own" the target,
        // in case it comes from a pool.
        // 获取目标对象
        target = targetSource.getTarget();
        if (target != null) {
            targetClass = target.getClass();
        }

        // 获取定义好的拦截器链
        // Get the interception chain for this method.
        List<Object> chain = this.advised.getInterceptorsAndDynamicInterceptionAdvice(method, targetClass);

        // Check whether we have any advice. If we don't, we can fallback on direct
        // reflective invocation of the target, and avoid creating a MethodInvocation.
        if (chain.isEmpty()) {
            // We can skip creating a MethodInvocation: just invoke the target directly
            // Note that the final invoker must be an InvokerInterceptor so we know it does
            // nothing but a reflective operation on the target, and no hot swapping or fancy proxying.
            // 没有拦截链则直接调用target方法
            retVal = AopUtils.invokeJoinpointUsingReflection(target, method, args);
        }
        else {
            // We need to create a method invocation...
            //对拦截链进行封装  得到对象ReflectiveMethodInvocation 调用 proceed 方法
            invocation = new ReflectiveMethodInvocation(proxy, target, method, args, targetClass, chain);
            // Proceed to the joinpoint through the interceptor chain.
            retVal = invocation.proceed();// 方法内部将执行拦截器的切面直到目标方法被执行
        }

        // Massage return value if necessary.
        Class<?> returnType = method.getReturnType();
        if (retVal != null && retVal == target && returnType.isInstance(proxy) &&
                !RawTargetAccess.class.isAssignableFrom(method.getDeclaringClass())) {
            // Special case: it returned "this" and the return type of the method
            // is type-compatible. Note that we can't help if the target sets
            // a reference to itself in another returned object.
            retVal = proxy;
        }
        else if (retVal == null && returnType != Void.TYPE && returnType.isPrimitive()) {
            throw new AopInvocationException(
                    "Null return value from advice does not match primitive return type for: " + method);
        }
        return retVal;
    }
    finally {
        if (target != null && !targetSource.isStatic()) {
            // Must have come from TargetSource.
            targetSource.releaseTarget(target);
        }
        if (setProxyContext) {
            // Restore old proxy.
            AopContext.setCurrentProxy(oldProxy);
        }
    }
}

7、代理会执行到： ReflectiveMethodInvocation#proceed 方法

8、最终会执行到：TransactionInterceptor#invoke 方法

9、执行 TransactionAspectSupport 事务方法 
TransactionInterceptor#invoke 方法会调用到父类的 TransactionAspectSupport#invokeWithinTransaction 方法

10、业务方法执行 

11、Spring 事务处理的流程 

（a）、开启事务 

（b）、事务回滚 

（c）、事务提交 

声明：本编文章是自己在查看spring提取@Transactional注解的源码过程中随手记下的笔记，只做了大概流程的记录，未做详细分析，如有错误还请谅解。

1、事务切面匹配处理类

AopUtils#canApply(Pointcut, Class , boolean) 
方法中会调用到 TransactionAttributeSourcePointcut#matches 方法

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;
    }

    MethodMatcher methodMatcher = pc.getMethodMatcher();
    IntroductionAwareMethodMatcher introductionAwareMethodMatcher = null;
    if (methodMatcher instanceof IntroductionAwareMethodMatcher) {
        introductionAwareMethodMatcher = (IntroductionAwareMethodMatcher) methodMatcher;
    }

    Set<Class> classes = new HashSet<Class>(ClassUtils.getAllInterfacesForClassAsSet(targetClass));
    classes.add(targetClass);
    for (Class<?> clazz : classes) {
        Method[] methods = clazz.getMethods();
        for (Method method : methods) {
            //methodMatcher.matches(method, targetClass) 方法会匹配对应的处理类，在Transaction提取的过程中会匹配到：TransactionAttributeSourcePointcut 
            if ((introductionAwareMethodMatcher != null &&
                    introductionAwareMethodMatcher.matches(method, targetClass, hasIntroductions)) ||
                    methodMatcher.matches(method, targetClass)) {
                return true;
            }
        }
    }

    return false;
}

2、事务切点匹配

TransactionAttributeSourcePointcut#matches

在阅读TransactionAttributeSourcePointcut内的源代码的时候，我们发现该类是一个抽象，但是他确没有实现的子类！！！那么这个类到底在哪被引用了呢？

abstract class TransactionAttributeSourcePointcut extends StaticMethodMatcherPointcut implements Serializable {

    public boolean matches(Method method, Class targetClass) {

        // 该处调用了 getTransactionAttributeSource() 的抽象方法，但是却没有子类实现这个方法，这是怎么一回事呢？
        TransactionAttributeSource tas = getTransactionAttributeSource();
        return (tas == null || tas.getTransactionAttribute(method, targetClass) != null);
    }

    @Override
    public boolean equals(Object other) {
        if (this == other) {
            return true;
        }
        if (!(other instanceof TransactionAttributeSourcePointcut)) {
            return false;
        }
        TransactionAttributeSourcePointcut otherPc = (TransactionAttributeSourcePointcut) other;
        return ObjectUtils.nullSafeEquals(getTransactionAttributeSource(), otherPc.getTransactionAttributeSource());
    }

    @Override
    public int hashCode() {
        return TransactionAttributeSourcePointcut.class.hashCode();
    }

    @Override
    public String toString() {
        return getClass().getName() + ": " + getTransactionAttributeSource();
    }


    /**
     * Obtain the underlying TransactionAttributeSource (may be {@code null}).
     * To be implemented by subclasses.
     */
    protected abstract TransactionAttributeSource getTransactionAttributeSource();

}

3、TransactionAttributeSourcePointcut 抽象类的应用

我们怀着上面的疑问全局搜索 TransactionAttributeSourcePointcut 可以在 BeanFactoryTransactionAttributeSourceAdvisor 里面找到如下的代码：

public class BeanFactoryTransactionAttributeSourceAdvisor extends AbstractBeanFactoryPointcutAdvisor {

    private TransactionAttributeSource transactionAttributeSource;

    // 此处利用了匿名内部类的方式实例化了 TransactionAttributeSourcePointcut 对象，在此我们找到了上面问题的答案。
    private final TransactionAttributeSourcePointcut pointcut = new TransactionAttributeSourcePointcut() {
        @Override
        protected TransactionAttributeSource getTransactionAttributeSource() {
            return transactionAttributeSource;
        }
    };


    /**
     * Set the transaction attribute source which is used to find transaction
     * attributes. This should usually be identical to the source reference
     * set on the transaction interceptor itself.
     * @see TransactionInterceptor#setTransactionAttributeSource
     */
    public void setTransactionAttributeSource(TransactionAttributeSource transactionAttributeSource) {
        this.transactionAttributeSource = transactionAttributeSource;
    }

    /**
     * Set the {@link ClassFilter} to use for this pointcut.
     * Default is {@link ClassFilter#TRUE}.
     */
    public void setClassFilter(ClassFilter classFilter) {
        this.pointcut.setClassFilter(classFilter);
    }

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

}

4、TransactionAttributeSource 属性的 Bean 定义过程

其实，在实例化 BeanFactoryTransactionAttributeSourceAdvisor 时，Spring 已经为我们的 BeanFactoryTransactionAttributeSourceAdvisor 设置了 TransactionAttributeSource 属性，可以进入 AnnotationDrivenBeanDefinitionParser.AopAutoProxyConfigurer#configureAutoProxyCreator 方法中看源代码：

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);

            // 注解事务 transactionAttributeSource Spring 定义的Bean为： AnnotationTransactionAttributeSource 实例
            // Create the TransactionAttributeSource definition.
            RootBeanDefinition sourceDef = new RootBeanDefinition(AnnotationTransactionAttributeSource.class);
            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 BeanFactoryTransactionAttributeSourceAdvisor Bean 的定义
            // Create the TransactionAttributeSourceAdvisor definition.
            RootBeanDefinition advisorDef = new RootBeanDefinition(BeanFactoryTransactionAttributeSourceAdvisor.class);
            advisorDef.setSource(eleSource);
            advisorDef.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
            // 设置 transactionAttributeSource 属性
            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);
        }
    }
}

5、TransactionAttributeSource#getTransactionAttribute 方法的调用过程

通过以上的分析，我们可以确定 
TransactionAttributeSourcePointcut#getTransactionAttributeSource 返回的是：AnnotationTransactionAttributeSource 实例，AnnotationTransactionAttributeSource继承自：AbstractFallbackTransactionAttributeSource, 故此TransactionAttributeSourcePointcut#matches 最终会调用到 AbstractFallbackTransactionAttributeSource#getTransactionAttribute 方法

abstract class TransactionAttributeSourcePointcut extends StaticMethodMatcherPointcut implements Serializable {

    public boolean matches(Method method, Class targetClass) {
        TransactionAttributeSource tas = getTransactionAttributeSource();

        // 最终会调用到 AbstractFallbackTransactionAttributeSource#getTransactionAttribute 方法
        return (tas == null || tas.getTransactionAttribute(method, targetClass) != null);
    }

    // 省略其他代码 ……………………
}

再看 AbstractFallbackTransactionAttributeSource#getTransactionAttribute 方法

// 获取事务属性
public TransactionAttribute getTransactionAttribute(Method method, Class<?> targetClass) {
    // First, see if we have a cached value.
    Object cacheKey = getCacheKey(method, targetClass);
    Object cached = this.attributeCache.get(cacheKey);
    if (cached != null) {
        // Value will either be canonical value indicating there is no transaction attribute,
        // or an actual transaction attribute.
        if (cached == NULL_TRANSACTION_ATTRIBUTE) {
            return null;
        }
        else {
            return (TransactionAttribute) cached;
        }
    }
    else {
        // We need to work it out.  根据 method、targetClass 推算事务属性，TransactionAttribute 
        TransactionAttribute txAtt = computeTransactionAttribute(method, targetClass);
        // Put it in the cache.
        if (txAtt == null) {
            this.attributeCache.put(cacheKey, NULL_TRANSACTION_ATTRIBUTE);
        }
        else {
            if (logger.isDebugEnabled()) {
                logger.debug("Adding transactional method '" + method.getName() + "' with attribute: " + txAtt);
            }
            this.attributeCache.put(cacheKey, txAtt);
        }
        return txAtt;
    }
}

6、事务属性的推算过程：

// 推算事务属性，TransactionAttribute 
private TransactionAttribute computeTransactionAttribute(Method method, Class<?> targetClass) {
    // Don't allow no-public methods as required.
    if (allowPublicMethodsOnly() && !Modifier.isPublic(method.getModifiers())) {
        return null;
    }

    // Ignore CGLIB subclasses - introspect the actual user class.
    Class<?> userClass = ClassUtils.getUserClass(targetClass);
    // The method may be on an interface, but we need attributes from the target class.
    // If the target class is null, the method will be unchanged.
    Method specificMethod = ClassUtils.getMostSpecificMethod(method, userClass);
    // If we are dealing with method with generic parameters, find the original method.
    specificMethod = BridgeMethodResolver.findBridgedMethod(specificMethod);

    // 通过上面的分析，findTransactionAttribute 该方法最终会调用到：AnnotationTransactionAttributeSource#findTransactionAttribute(java.lang.Class<?>) 

    // First try is the method in the target class. 方式1： 从目标类的方法上找 Transaction注解
    TransactionAttribute txAtt = findTransactionAttribute(specificMethod);
    if (txAtt != null) {
        return txAtt;
    }

    // Second try is the transaction attribute on the target class.  方式2： 从目标类上找 Transaction注解
    txAtt = findTransactionAttribute(specificMethod.getDeclaringClass());
    if (txAtt != null) {
        return txAtt;
    }

    if (specificMethod != method) {// 以上两种方式如果还没有找到 TransactionAttribute 属性，那就要从目标类的接口开始找
        // Fallback is to look at the original method.  方式3：接口的方法上找 Transaction注解
        txAtt = findTransactionAttribute(method);
        if (txAtt != null) {
            return txAtt;
        }
        // Last fallback is the class of the original method.  方式4：接口的类上找 Transaction注解
        return findTransactionAttribute(method.getDeclaringClass());
    }
    return null;
}

7、事务注解属性的解析

AnnotationTransactionAttributeSource#findTransactionAttribute(​​Java​​.lang.Class

8、获取事务注解

public class SpringTransactionAnnotationParser implements TransactionAnnotationParser, Serializable {

    public TransactionAttribute parseTransactionAnnotation(AnnotatedElement ae) {
        //获取 Transactional 注解
        Transactional ann = AnnotationUtils.getAnnotation(ae, Transactional.class);
        if (ann != null) {
            //从 @Transactional 注解上获取事务属性值，并包装成 TransactionAttribute 返回
            return parseTransactionAnnotation(ann);
        }
        else {
            return null;
        }
    }

    public TransactionAttribute parseTransactionAnnotation(Transactional ann) {
        RuleBasedTransactionAttribute rbta = new RuleBasedTransactionAttribute();
        rbta.setPropagationBehavior(ann.propagation().value());
        rbta.setIsolationLevel(ann.isolation().value());
        rbta.setTimeout(ann.timeout());
        rbta.setReadOnly(ann.readOnly());
        rbta.setQualifier(ann.value());
        ArrayList<RollbackRuleAttribute> rollBackRules = new ArrayList<RollbackRuleAttribute>();
        Class[] rbf = ann.rollbackFor();
        for (Class rbRule : rbf) {
            RollbackRuleAttribute rule = new RollbackRuleAttribute(rbRule);
            rollBackRules.add(rule);
        }
        String[] rbfc = ann.rollbackForClassName();
        for (String rbRule : rbfc) {
            RollbackRuleAttribute rule = new RollbackRuleAttribute(rbRule);
            rollBackRules.add(rule);
        }
        Class[] nrbf = ann.noRollbackFor();
        for (Class rbRule : nrbf) {
            NoRollbackRuleAttribute rule = new NoRollbackRuleAttribute(rbRule);
            rollBackRules.add(rule);
        }
        String[] nrbfc = ann.noRollbackForClassName();
        for (String rbRule : nrbfc) {
            NoRollbackRuleAttribute rule = new NoRollbackRuleAttribute(rbRule);
            rollBackRules.add(rule);
        }
        rbta.getRollbackRules().addAll(rollBackRules);
        return rbta;
    }

    @Override
    public boolean equals(Object other) {
        return (this == other || other instanceof SpringTransactionAnnotationParser);
    }

    @Override
    public int hashCode() {
        return SpringTransactionAnnotationParser.class.hashCode();
    }

}