闲聊
在Spring Bean的生命周期中，处理aop的流程只有第一步处理通知和最后一步创建代理对象。
可以说只要去掉第一步和最后一步，也不会影响SpringBean的生命周期。可见在生命周期中处理aop 和aop的理念是完全符合解耦的思想。
切面的组成
一个简单的切面AspectJ 通常可以由多个切入点Pointcut 和多个通知Advice 组成。
切入点：切入点和切入点表达式相辅相成的存在，通常由切入点表达式决定切入点需要切入的位置
通知：在切面里面，通知通常分为五种。分别是前置通知，环绕通知，后置通知，异常通知和返回通知。
类图
类图分析
五种通知都继承了一个抽象的父类 AbstractAspectJAdvice，通知的顶级接口 Advice
AspectJMethodBeforeAdvice 实现了 MethodBeforeAdvice ，MethodBeforeAdvice又继承了 BeforeAdvice
AspectJAfterReturningAdvice 实现了 AfterReturningAdvice，AfterReturningAdvice又继承了 AfterAdvice
AspectJAfter......类型的通知实现了AfterAdvice 接口
而另外的三个通知 AspectJAroundAdvice， AspectJAfterAdvice ，AspectJAfterThrowingAdvice 有一个共同实现 MethodInterceptor 这是一个拦截器
调用通知的逻辑是一个Interceptor的递归调用链，但是AspectJMethodBeforeAdvice 和 AspectJAfterReturningAdvice并不是一个拦截器。
所以会有 AspectJMethodBeforeAdvice 通过 MethodBeforeAdviceAdapter 变成一个 MethodBeforeAdviceInterceptor
AspectJAfterReturningAdvice 通过 AfterReturningAdviceAdapter 变成一个 AfterReturningAdviceInterceptor
如何处理通知
Spring Bean 的生命周期中第一步是如何处理通知的呢。
一个切点 == Pointcut , 一个通知 == advice，而一个切面 == List<Advisor>
一个切面里面有几个通知最后都会封装成几个advisor，advisor里面的 pointcut可能一样。
生成 advisor 流程
1.Spring Bean 生命周期第一步
Object bean = resolveBeforeInstantiation(beanName, mbdToUse);2.获取所有被@Aspect 注解标记的beanName 循环生成List<Advisor>,在统一放入一个大的List<Advisor> 集合中。通过缓存控制避免重复解析。
3.通过beanName 和 beanFactory 封装该切面对应的通知工厂，通过通知工厂产生对应的通知，在封装到集合中去
4.生成不同类型的advisor 。InstantiationModelAwarePointcutAdvisorImpl 一个advisor接口的实现类。从工厂中获取到（创建）的advisor，都会放到InstantiationModelAwarePointcutAdvisorImpl 的 Advice instantiatedAdvice 属性中 。
public InstantiationModelAwarePointcutAdvisorImpl(AspectJExpressionPointcut declaredPointcut,
Method aspectJAdviceMethod, AspectJAdvisorFactory aspectJAdvisorFactory,
MetadataAwareAspectInstanceFactory aspectInstanceFactory, int declarationOrder, String aspectName) {
this.declaredPointcut = declaredPointcut;
this.declaringClass = aspectJAdviceMethod.getDeclaringClass();
this.methodName = aspectJAdviceMethod.getName();
this.parameterTypes = aspectJAdviceMethod.getParameterTypes();
this.aspectJAdviceMethod = aspectJAdviceMethod;
this.aspectJAdvisorFactory = aspectJAdvisorFactory;
this.aspectInstanceFactory = aspectInstanceFactory;
this.declarationOrder = declarationOrder;
this.aspectName = aspectName;
if (aspectInstanceFactory.getAspectMetadata().isLazilyInstantiated()) {
// Static part of the pointcut is a lazy type.
Pointcut preInstantiationPointcut = Pointcuts.union(
aspectInstanceFactory.getAspectMetadata().getPerClausePointcut(), this.declaredPointcut);
// Make it dynamic: must mutate from pre-instantiation to post-instantiation state.
// If it's not a dynamic pointcut, it may be optimized out
// by the Spring AOP infrastructure after the first evaluation.
this.pointcut = new PerTargetInstantiationModelPointcut(
this.declaredPointcut, preInstantiationPointcut, aspectInstanceFactory);
this.lazy = true;
}
else {
// A singleton aspect.
this.pointcut = this.declaredPointcut;
this.lazy = false;
this.instantiatedAdvice = instantiateAdvice(this.declaredPointcut);
}
}构造方法里面包含了一整个切面的信息。再看 instantiateAdvice(this.declaredPointcut) 里面的getAdvisor 方法
public Advice getAdvice(Method candidateAdviceMethod, AspectJExpressionPointcut expressionPointcut,
MetadataAwareAspectInstanceFactory aspectInstanceFactory, int declarationOrder, String aspectName) {
Class<?> candidateAspectClass = aspectInstanceFactory.getAspectMetadata().getAspectClass();
validate(candidateAspectClass);
AspectJAnnotation<?> aspectJAnnotation =
AbstractAspectJAdvisorFactory.findAspectJAnnotationOnMethod(candidateAdviceMethod);
if (aspectJAnnotation == null) {
return null;
}
// If we get here, we know we have an AspectJ method.
// Check that it's an AspectJ-annotated class
if (!isAspect(candidateAspectClass)) {
throw new AopConfigException("Advice must be declared inside an aspect type: " +
"Offending method '" + candidateAdviceMethod + "' in class [" +
candidateAspectClass.getName() + "]");
}
if (logger.isDebugEnabled()) {
logger.debug("Found AspectJ method: " + candidateAdviceMethod);
}
AbstractAspectJAdvice springAdvice;
switch (aspectJAnnotation.getAnnotationType()) {
case AtPointcut:
if (logger.isDebugEnabled()) {
logger.debug("Processing pointcut '" + candidateAdviceMethod.getName() + "'");
}
return null;
case AtAround:
springAdvice = new AspectJAroundAdvice(
candidateAdviceMethod, expressionPointcut, aspectInstanceFactory);
break;
case AtBefore:
springAdvice = new AspectJMethodBeforeAdvice(
candidateAdviceMethod, expressionPointcut, aspectInstanceFactory);
break;
case AtAfter:
springAdvice = new AspectJAfterAdvice(
candidateAdviceMethod, expressionPointcut, aspectInstanceFactory);
break;
case AtAfterReturning:
springAdvice = new AspectJAfterReturningAdvice(
candidateAdviceMethod, expressionPointcut, aspectInstanceFactory);
AfterReturning afterReturningAnnotation = (AfterReturning) aspectJAnnotation.getAnnotation();
if (StringUtils.hasText(afterReturningAnnotation.returning())) {
springAdvice.setReturningName(afterReturningAnnotation.returning());
}
break;
case AtAfterThrowing:
springAdvice = new AspectJAfterThrowingAdvice(
candidateAdviceMethod, expressionPointcut, aspectInstanceFactory);
AfterThrowing afterThrowingAnnotation = (AfterThrowing) aspectJAnnotation.getAnnotation();
if (StringUtils.hasText(afterThrowingAnnotation.throwing())) {
springAdvice.setThrowingName(afterThrowingAnnotation.throwing());
}
break;
default:
throw new UnsupportedOperationException(
"Unsupported advice type on method: " + candidateAdviceMethod);
}
// Now to configure the advice...
springAdvice.setAspectName(aspectName);
springAdvice.setDeclarationOrder(declarationOrder);
String[] argNames = this.parameterNameDiscoverer.getParameterNames(candidateAdviceMethod);
if (argNames != null) {
springAdvice.setArgumentNamesFromStringArray(argNames);
}
springAdvice.calculateArgumentBindings();
return springAdvice;
}最终通过不同通知的类型生成不同的advisor 并返回。
绑定通知并生成代理对象
Spring Bean生命周期中的最后一步将切面对象与通知进行绑定。
绑定通知
Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(bean.getClass(), beanName, null);进行到这一步的时候这个bean已经被实例化出来了。
绑定通知流程其实在上篇解析表达式的时候就已经出来了。
循环每一个advisor 。通过表达式 和 bean.getClass() 去两次匹配
protected Object[] getAdvicesAndAdvisorsForBean(
Class<?> beanClass, String beanName, @Nullable TargetSource targetSource) {
List<Advisor> advisors = findEligibleAdvisors(beanClass, beanName);
if (advisors.isEmpty()) {
return DO_NOT_PROXY;
}
return advisors.toArray();
}protected List<Advisor> findEligibleAdvisors(Class<?> beanClass, String beanName) {
List<Advisor> candidateAdvisors = findCandidateAdvisors();
List<Advisor> eligibleAdvisors = findAdvisorsThatCanApply(candidateAdvisors, beanClass, beanName);
extendAdvisors(eligibleAdvisors);
if (!eligibleAdvisors.isEmpty()) {
eligibleAdvisors = sortAdvisors(eligibleAdvisors);
}
return eligibleAdvisors;
}protected List<Advisor> findAdvisorsThatCanApply(
List<Advisor> candidateAdvisors, Class<?> beanClass, String beanName) {
ProxyCreationContext.setCurrentProxiedBeanName(beanName);
try {
return AopUtils.findAdvisorsThatCanApply(candidateAdvisors, beanClass);
}
finally {
ProxyCreationContext.setCurrentProxiedBeanName(null);
}
}public static List<Advisor> findAdvisorsThatCanApply(List<Advisor> candidateAdvisors, Class<?> clazz) {
if (candidateAdvisors.isEmpty()) {
return candidateAdvisors;
}
List<Advisor> eligibleAdvisors = new ArrayList<>();
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) {
// already processed
continue;
}
if (canApply(candidate, clazz, hasIntroductions)) {
eligibleAdvisors.add(candidate);
}
}
return eligibleAdvisors;
}第一次 canApply(candidate, clazz) 匹配 进去 hasIntroductions == false，也会两次匹配，第一次匹配类型，在循环方法 再次匹配，第一次基本就可以实现命中目标方法，当在每个通知里面循环完该对象的方法时，就已经完成绑定了。
第二次 canApply(candidate, clazz, hasIntroductions) hasIntroductions == true 再次匹配，能进入到再次匹配，是直接返回true 的，代表命中了。
创建代理对象
绑定完通知后会根据对象类型去生成不同的代理对象。比如 jdk动态代理或者cglib动态代理。
但是这一步里面会将advisor 转化成 interceptor
Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(bean.getClass(), beanName, null);
if (specificInterceptors != DO_NOT_PROXY) {
this.advisedBeans.put(cacheKey, Boolean.TRUE);
Object proxy = createProxy(
bean.getClass(), beanName, specificInterceptors, new SingletonTargetSource(bean));
this.proxyTypes.put(cacheKey, proxy.getClass());
return proxy;
}createProxy里面
Advisor[] advisors = buildAdvisors(beanName, specificInterceptors);
循环绑定的所有通知
for (int i = 0; i < allInterceptors.size(); i++) {
advisors[i] = this.advisorAdapterRegistry.wrap(allInterceptors.get(i));
}public class DefaultAdvisorAdapterRegistry implements AdvisorAdapterRegistry, Serializable {
private final List<AdvisorAdapter> adapters = new ArrayList<>(3);
/**
* Create a new DefaultAdvisorAdapterRegistry, registering well-known adapters.
*/
public DefaultAdvisorAdapterRegistry() {
registerAdvisorAdapter(new MethodBeforeAdviceAdapter());
registerAdvisorAdapter(new AfterReturningAdviceAdapter());
registerAdvisorAdapter(new ThrowsAdviceAdapter());
}
@Override
public Advisor wrap(Object adviceObject) throws UnknownAdviceTypeException {
if (adviceObject instanceof Advisor) {
return (Advisor) adviceObject;
}
if (!(adviceObject instanceof Advice)) {
throw new UnknownAdviceTypeException(adviceObject);
}
Advice advice = (Advice) adviceObject;
if (advice instanceof MethodInterceptor) {
// So well-known it doesn't even need an adapter.
return new DefaultPointcutAdvisor(advice);
}
for (AdvisorAdapter adapter : this.adapters) {
// Check that it is supported.
if (adapter.supportsAdvice(advice)) {
return new DefaultPointcutAdvisor(advice);
}
}
throw new UnknownAdviceTypeException(advice);
}
@Override
public MethodInterceptor[] getInterceptors(Advisor advisor) throws UnknownAdviceTypeException {
List<MethodInterceptor> interceptors = new ArrayList<>(3);
Advice advice = advisor.getAdvice();
if (advice instanceof MethodInterceptor) {
interceptors.add((MethodInterceptor) advice);
}
for (AdvisorAdapter adapter : this.adapters) {
if (adapter.supportsAdvice(advice)) {
interceptors.add(adapter.getInterceptor(advisor));
}
}
if (interceptors.isEmpty()) {
throw new UnknownAdviceTypeException(advisor.getAdvice());
}
return interceptors.toArray(new MethodInterceptor[0]);
}
@Override
public void registerAdvisorAdapter(AdvisorAdapter adapter) {
this.adapters.add(adapter);
}
}wrap 方法里面
advice instanceof MethodInterceptor 处理AspectJAroundAdvice， AspectJAfterAdvice ，AspectJAfterThrowingAdvice 三种类型。
AdvisorAdapter adapter : this.adapters 通过策略处理AspectJMethodBeforeAdvice 和 AspectJAfterReturningAdvice 这两种类型。
执行方法，调用责任链
执行方法
当我们执行目标方法的时候，会进入到代理类的invoke方法里面去，在这个方法里面对根据方法去匹配生成好的责任链通知。
1.被执行的这个目标方法是否被通知织入了需要增强的方法。
即使目标对象里面的某一个方法被增强的，这个目标对象还是依然会被生成代理对象，不管执行该目标对象的哪一个方法，都会进入代理对象的invoke方法。如果是jdk动态代理生成的代理对象，进入invoke里面的目标方法是一个抽象的方法，需要转化，而cglib动态代理生成的代理对象进入intercepter 的不是抽象的。
2.匹配责任链通知 还会进行 上文类似的canApply(candidate, clazz) 匹配，具体看jdk 和cglib执行的逻辑大致相同。
List<Object> chain = this.advised.getInterceptorsAndDynamicInterceptionAdvice(method, targetClass);
@Override
public List<Object> getInterceptorsAndDynamicInterceptionAdvice(
Advised config, Method method, @Nullable Class<?> targetClass) {
// This is somewhat tricky... We have to process introductions first,
// but we need to preserve order in the ultimate list.
AdvisorAdapterRegistry registry = GlobalAdvisorAdapterRegistry.getInstance();
Advisor[] advisors = config.getAdvisors();
List<Object> interceptorList = new ArrayList<>(advisors.length);
Class<?> actualClass = (targetClass != null ? targetClass : method.getDeclaringClass());
Boolean hasIntroductions = null;
for (Advisor advisor : advisors) {
if (advisor instanceof PointcutAdvisor) {
// Add it conditionally.
PointcutAdvisor pointcutAdvisor = (PointcutAdvisor) advisor;
if (config.isPreFiltered() || pointcutAdvisor.getPointcut().getClassFilter().matches(actualClass)) {
MethodMatcher mm = pointcutAdvisor.getPointcut().getMethodMatcher();
boolean match;
if (mm instanceof IntroductionAwareMethodMatcher) {
if (hasIntroductions == null) {
hasIntroductions = hasMatchingIntroductions(advisors, actualClass);
}
match = ((IntroductionAwareMethodMatcher) mm).matches(method, actualClass, hasIntroductions);
}
else {
match = mm.matches(method, actualClass);
}
if (match) {
MethodInterceptor[] interceptors = registry.getInterceptors(advisor);
if (mm.isRuntime()) {
// Creating a new object instance in the getInterceptors() method
// isn't a problem as we normally cache created chains.
for (MethodInterceptor interceptor : interceptors) {
interceptorList.add(new InterceptorAndDynamicMethodMatcher(interceptor, mm));
}
}
else {
interceptorList.addAll(Arrays.asList(interceptors));
}
}
}
}
else if (advisor instanceof IntroductionAdvisor) {
IntroductionAdvisor ia = (IntroductionAdvisor) advisor;
if (config.isPreFiltered() || ia.getClassFilter().matches(actualClass)) {
Interceptor[] interceptors = registry.getInterceptors(advisor);
interceptorList.addAll(Arrays.asList(interceptors));
}
}
else {
Interceptor[] interceptors = registry.getInterceptors(advisor);
interceptorList.addAll(Arrays.asList(interceptors));
}
}
return interceptorList;
}简化一下代码，自己写的。匹配规则是一样的，先匹配class，再匹配method，然后返回一个结果集 List<Object> chain
private List<Object> getInterceptorsAndDynamicInterceptionAdvice(Method method) {
List<XxAdvisor> advisors = this.advisors;
for (XxAdvisor advisor : advisors) {
if(advisor instanceof XxPointcutAdvisor){
XxPointcutAdvisor pointcutAdvisor = (XxPointcutAdvisor) advisor;
if(pointcutAdvisor.getXxPointcut().getXxClassFilter().matches(this.target.getClass())){
XxMethodMatcher xxMethodMatcher = pointcutAdvisor.getXxPointcut().getXxMethodMatcher();
boolean match = false;
if(xxMethodMatcher instanceof XxIntroductionAwareMethodMatcher){
match = (xxMethodMatcher).matches(method, this.target.getClass());
}
if(match){
interceptorList.addAll(Arrays.asList(getInterceptors(advisor)));
}
}
}
}
return interceptorList;
}递归调用责任链
jdk动态代理的invoke 责任链调用
invocation = new ReflectiveMethodInvocation(proxy, target, method, args, targetClass, chain);
retVal = invocation.proceed();cglib动态代理的interceptor责任链调用
retVal = new CglibMethodInvocation(proxy, target, method, args, targetClass, chain, methodProxy).proceed();new 出来的对象都是一个MethodInvocation类型的方法调用对象
重点看 proceed 方法，两种类型创建出来的对象执行 proceed方法是同一段代码块
public Object proceed() throws Throwable {
// We start with an index of -1 and increment early.
if (this.currentInterceptorIndex == this.interceptorsAndDynamicMethodMatchers.size() - 1) {
return invokeJoinpoint();
}
Object interceptorOrInterceptionAdvice =
this.interceptorsAndDynamicMethodMatchers.get(++this.currentInterceptorIndex);
if (interceptorOrInterceptionAdvice instanceof InterceptorAndDynamicMethodMatcher) {
// Evaluate dynamic method matcher here: static part will already have
// been evaluated and found to match.
InterceptorAndDynamicMethodMatcher dm =
(InterceptorAndDynamicMethodMatcher) interceptorOrInterceptionAdvice;
Class<?> targetClass = (this.targetClass != null ? this.targetClass : this.method.getDeclaringClass());
if (dm.methodMatcher.matches(this.method, targetClass, this.arguments)) {
return dm.interceptor.invoke(this);
}
else {
// Dynamic matching failed.
// Skip this interceptor and invoke the next in the chain.
return proceed();
}
}
else {
// It's an interceptor, so we just invoke it: The pointcut will have
// been evaluated statically before this object was constructed.
return ((MethodInterceptor) interceptorOrInterceptionAdvice).invoke(this);
}
}简化一下就是这样的，自己写的
public Object proceed() throws Throwable {
if(this.currentInterceptorIndex == this.interceptorsAndDynamicMethodMatchers.size()-1){
return this.method.invoke(this.target,this.arguments);
}
Object interceptorOrInterceptionAdvice =
this.interceptorsAndDynamicMethodMatchers.get(++this.currentInterceptorIndex);
return ((XxMethodInterceptor) interceptorOrInterceptionAdvice).invoke(this);
}每次进来都只会执行最后一个return里面的逻辑。当执行到最后一个interceptor 的时候，就执行第一个return里面的逻辑。
每次执行最后的return逻辑的时候，对应的都是不同通知的拦截器，每个拦截器会匹配进入不同类型的通知（因为每个通知已经是一个拦截器了）里面的逻辑，当执行完不同通知的逻辑会再次调用父类里面的方法，而父类里面的方法最终返回的是当前目标方法的invoke方法，所以又递归回来了。
又回到了该方法的起点。
自己仿Spring Aop 写的这个责任链的递归调用也没整明白这种调用模式..........
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