spring AOP源码分析之拦截器

我们都知道在springAOP中产生代理对象的方式有jdk和cglib的方式生成，无论那种方式,AOP的拦截的处理都是通过ReflectiveMethodInvocation中的proceed方法

其方法的源码如下：

publicObjectproceed()

throwsThrowable

{

//如果拦截器迭代完毕，这里开始调用目标方法

if(currentInterceptorIndex==interceptorsAndDynamicMethodMatchers.size()-1)

returninvokeJoinpoint();

//从拦截器的集合中获取拦截器

ObjectinterceptorOrInterceptionAdvice=interceptorsAndDynamicMethodMatchers.get(++currentInterceptorIndex);

//判断如果是该类型的

if(interceptorOrInterceptionAdviceinstanceofInterceptorAndDynamicMethodMatcher)

{

InterceptorAndDynamicMethodMatcherdm=(InterceptorAndDynamicMethodMatcher)interceptorOrInterceptionAdvice;

//那么对方法进行匹配

if(dm.methodMatcher.matches(method,targetClass,arguments))

returndm.interceptor.invoke(this);

else

//否则进行递归调用

returnproceed();

}else

{

//如果是interceptor,直接调用这个interceptor对应的方法

return((MethodInterceptor)interceptorOrInterceptionAdvice).invoke(this);

}

}

那么这个拦截器链的集合是如何产生的呢？

由于AopFactoryBean是继承AdvisedSupport我们在看下AdvisedSupport中的getInterceptorsAndDynamicInterceptionAdvice方法

//获取拦截器

publicListgetInterceptorsAndDynamicInterceptionAdvice(Methodmethod,ClasstargetClass)

{

MethodCacheKeycacheKey=newMethodCacheKey(method);

Listcached=(List)methodCache.get(cacheKey);

if(cached==null)

{

//拦截器链工厂获取

cached=advisorChainFactory.getInterceptorsAndDynamicInterceptionAdvice(this,method,targetClass);

methodCache.put(cacheKey,cached);

}

returncached;

}

获取拦截器链的工作是由配置好的advisorChainFactory来完成的，在这里advisorChainFactory被配置成一个DefaultAdvisorChainFactory对象，在DefaultAdvisorChainFactory中getInterceptorsAndDynamicInterceptionAdvice方法来获取，源码如下：

publicListgetInterceptorsAndDynamicInterceptionAdvice(Advisedconfig,Methodmethod,ClasstargetClass)

{

//定义拦截器链数组的大小

ListinterceptorList=newArrayList(config.getAdvisors().length);

booleanhasIntroductions=hasMatchingIntroductions(config,targetClass);

//这里采用的简单工厂的方式产生AdvisorAdapterRegistry对象，而该接口的实现类为DefaultAdvisorAdapterRegistry

AdvisorAdapterRegistryregistry=GlobalAdvisorAdapterRegistry.getInstance();

org.springframework.aop.Advisoraadvisor[];

intj=(aadvisor=config.getAdvisors()).length;

for(inti=0;i<j;i++)

{

org.springframework.aop.Advisoradvisor=aadvisor[i];

if(advisorinstanceofPointcutAdvisor)

{

PointcutAdvisorpointcutAdvisor=(PointcutAdvisor)advisor;

if(config.isPreFiltered()||pointcutAdvisor.getPointcut().getClassFilter().matches(targetClass))

{

org.aopalliance.intercept.MethodInterceptorinterceptors[]=registry.getInterceptors(advisor);

MethodMatchermm=pointcutAdvisor.getPointcut().getMethodMatcher();

if(MethodMatchers.matches(mm,method,targetClass,hasIntroductions))

if(mm.isRuntime())

{

org.aopalliance.intercept.MethodInterceptoramethodinterceptor[];

intl=(amethodinterceptor=interceptors).length;

for(intk=0;k<l;k++)

{

org.aopalliance.intercept.MethodInterceptorinterceptor=amethodinterceptor[k];

interceptorList.add(newInterceptorAndDynamicMethodMatcher(interceptor,mm));

}

}else

{

interceptorList.addAll((Collection)Arrays.asList(interceptors));

}

}

}else

if(advisorinstanceofIntroductionAdvisor)

{

IntroductionAdvisoria=(IntroductionAdvisor)advisor;

if(config.isPreFiltered()||ia.getClassFilter().matches(targetClass))

{

org.aopalliance.intercept.Interceptorinterceptors[]=registry.getInterceptors(advisor);

interceptorList.addAll((Collection)Arrays.asList(interceptors));

}

}else

{

org.aopalliance.intercept.Interceptorinterceptors[]=registry.getInterceptors(advisor);

interceptorList.addAll((Collection)Arrays.asList(interceptors));

}

}

returninterceptorList;

}

从上述源码可知：DefaultAdvisorChainFactory会通过一个AdivesorAdatperRegistry来实现拦截器的注册，而这个AdivesorAdatperRegistry对象的advice通知的知入功能起了很大的作用。

Advice通知的实现

我们在看下DefaultAdvisorAdapterRegistry中的getInterceptors方法

//通知适配器集合

privatefinalListadapters=newArrayList(3);

publicMethodInterceptor[]getInterceptors(Advisoradvisor)

throwsUnknownAdviceTypeException

{

Listinterceptors=newArrayList(3);

//从通知器中获取通知

Adviceadvice=advisor.getAdvice();

if(adviceinstanceofMethodInterceptor)

interceptors.add((MethodInterceptor)advice);

for(Iteratoriterator=adapters.iterator();iterator.hasNext();)

{

//循环所有的适配器通知

AdvisorAdapteradapter=(AdvisorAdapter)iterator.next();

if(adapter.supportsAdvice(advice))

interceptors.add(adapter.getInterceptor(advisor));

}

if(interceptors.isEmpty())

thrownewUnknownAdviceTypeException(advisor.getAdvice());

else

return(MethodInterceptor[])interceptors.toArray(newMethodInterceptor[interceptors.size()]);

}

关于通知适配器集合的初始化,通过构造函数注册

//注册advice适配器

publicDefaultAdvisorAdapterRegistry()

{

registerAdvisorAdapter(newMethodBeforeAdviceAdapter());

registerAdvisorAdapter(newAfterReturningAdviceAdapter());

registerAdvisorAdapter(newThrowsAdviceAdapter());

}

//注册方法

publicvoidregisterAdvisorAdapter(AdvisorAdapteradapter)

{

adapters.add(adapter);

}

我们在看一个advice适配器具体实现例如MethodBeforeAdviceAdapter源码

classMethodBeforeAdviceAdapter

implementsAdvisorAdapter,Serializable

{

MethodBeforeAdviceAdapter()

{

}

publicbooleansupportsAdvice(Adviceadvice)

{

returnadviceinstanceofMethodBeforeAdvice;

}

publicMethodInterceptorgetInterceptor(Advisoradvisor)

{

//从中获取advice

MethodBeforeAdviceadvice=(MethodBeforeAdvice)advisor.getAdvice();

//返回拦截器

returnnewMethodBeforeAdviceInterceptor(advice);

}

}