seata源码分析之全局事务的开启跟xid的传递_transactionhookmanager.registerhook-优快云博客

概览

首先我们通过@GlobalTransactional这个注解开启一个全局事务，而GlobalTransactionScanner.wrapIfNecessary()会为所有方法上加了这个注解的bean注入一个包装了GlobalTransactionalInterceptor实例的advisor，然后返回一个代理对象。GlobalTransactionalInterceptor会在该bean的方法调用前进行拦截，判断是否开启全局事务

上源码，关键位置我打了注释

@Override
protected Object wrapIfNecessary(Object bean, String beanName, Object cacheKey) {
    //判断全局事务是否启用
    if (disableGlobalTransaction) {
        return bean;
    }
    try {
        synchronized (PROXYED_SET) {
            if (PROXYED_SET.contains(beanName)) {
                return bean;
            }
            interceptor = null;
            //check TCC proxy
            if (TCCBeanParserUtils.isTccAutoProxy(bean, beanName, applicationContext)) {
                //TCC interceptor, proxy bean of sofa:reference/dubbo:reference, and LocalTCC
                interceptor = new TccActionInterceptor(TCCBeanParserUtils.getRemotingDesc(beanName));
            } else {
                Class<?> serviceInterface = SpringProxyUtils.findTargetClass(bean);
                Class<?>[] interfacesIfJdk = SpringProxyUtils.findInterfaces(bean);

                //判断bean里的方法上有没有@GlobalTransactional注解
                if (!existsAnnotation(new Class[]{serviceInterface})
                    && !existsAnnotation(interfacesIfJdk)) {
                    return bean;
                }

                if (interceptor == null) {
                    //初始化Interceptor,后面会注入代理对象
                    interceptor = new GlobalTransactionalInterceptor(failureHandlerHook);
                    ConfigurationFactory.getInstance().addConfigListener(ConfigurationKeys.DISABLE_GLOBAL_TRANSACTION, (ConfigurationChangeListener) interceptor);
                }
            }
            
            //判断当前bean是否已被aop代理过，比如说方法上加了@Transactional就会被spring代理
            //如果没有被代理，调用父类的模板方法进行代理，advisor通过被重写的
            //getAdvicesAndAdvisorsForBean返回上面的interceptor进行包装
            if (!AopUtils.isAopProxy(bean)) {
                bean = super.wrapIfNecessary(bean, beanName, cacheKey);
            } else {
                AdvisedSupport advised = SpringProxyUtils.getAdvisedSupport(bean);

                //把GlobalTransactionalInterceptor包装成advisor
                Advisor[] advisor = buildAdvisors(beanName, getAdvicesAndAdvisorsForBean(null, null, null));
                for (Advisor avr : advisor) {
                    advised.addAdvisor(0, avr);
                }
            }
            PROXYED_SET.add(beanName);
            return bean;
        }
    } catch (Exception exx) {
        throw new RuntimeException(exx);
    }
}


@Override
protected Object[] getAdvicesAndAdvisorsForBean(Class beanClass, String beanName,          
  TargetSource customTargetSource) throws BeansException {

    //返回interceptor[]
    return new Object[]{interceptor};
}

@Override
    public void afterPropertiesSet() {
        if (disableGlobalTransaction) {
            if (LOGGER.isInfoEnabled(