spring源码学习系列1.2-spring事务代理深入分析2

提示:
BeanPostProcessor

AopUtils

代理模式

spring中<aop:config/>,<tx:annotation-driver/>,<aop:aspectJ>等配置看似复杂,其实本质就是PointCut，BeanPostProcessor,AbstractAutoProxyCreator一些接口直接的解耦

查找的Advisor用到了模板方法设计模式和委托模式,创建代理类用到了代理模式




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

spring中的该配置实际上就是注册了几个beanDefinition

InfrastructureAdvisorAutoProxyCreator - BeanPostProcess

AnnotationTransactionAttributeSource - 可以延伸为Pointcut

TransactionInterceptor - MethodInterceptor

TransactionAttributeSourceAdvisor - Advisor(其中持有TransactionAttributeSourcePointcut)



在bean实例化后,开始调用BeanPostProcess.postProcessAfterInitialization

1.首先查询所有的advisor

2.根据advisor中的pointcut校验bean是否符合该advisor,并返回methodInterceptor

3.将methodInterceptor通过适配器模式封装到advisors(这里的methodInterceptor是广义的概念，有可能是advice等)

4.将advisors封装到advisedSupport，委托ProxyFactory(AdvisedSupport)生成代理

ProxyFactory委托AopProxyFactory(InvocationHandler)生成代理





<aop:aspectj-autoproxy /> - AopNamespaceHandler

该配置就是定义了一个AnnotationAwareAspectJAutoProxyCreator（BeanPostProcessor）的bean







<aop:config/> - AopNamespaceHandler

spring中的该配置实际上就是注册了几个beanDefinition

AspectJAwareAdvisorAutoProxyCreator -BeanPostProcessor

AspectJExpressionPointcut - Pointcut

DefaultBeanFactoryPointcutAdvisor - Advisor




讨论:
这里注册的几个BeanPostProcessor都继承了AbastractAutoProxyCreator。AbastractAutoProxyCreator采用了模板方法设计模式,在模板方法中定义了生成代理的一系列步骤，由子类实现查找匹配的Advisor的过程


采用AopUtils查找合适的Advisor

public static List<Advisor> findAdvisorsThatCanApply(List<Advisor> candidateAdvisors, Class<?> clazz){
...
}

PointCut接口设计:

public interface Pointcut {

	/**
	 * Return the ClassFilter for this pointcut.
	 * @return the ClassFilter (never {@code null})
	 */
	ClassFilter getClassFilter();

	/**
	 * Return the MethodMatcher for this pointcut.
	 * @return the MethodMatcher (never {@code null})
	 */
	MethodMatcher getMethodMatcher();


	/**
	 * Canonical Pointcut instance that always matches.
	 */
	Pointcut TRUE = TruePointcut.INSTANCE;

}