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springAop代理责任链模式源码解析

web 2025/7/1 19:26:14

两次匹配

Bean 后置处理器中的匹配

方法调用时的匹配

Bean后置处理器中Advisor匹配流程

方法调用时的匹配

Jdk

cglib

小小总结

Advisor 收集与排序

责任链执行过程

两次匹配

Bean 后置处理器中的匹配

在 Bean 初始化过程中，Spring 会通过 Bean 后置处理器（BeanPostProcessor）匹配出符合当前 Bean 类型的 Advisor。这一过程主要发生在 postProcessAfterInitialization 方法中。

目的：确定当前 Bean 是否需要代理，以及使用哪些 Advisor。
过程：
Spring 会调用 getAdvicesAndAdvisorsForBean 方法，查找所有候选的 Advisor。
过滤出可以应用到当前 Bean 的 Advisor，并将其存储在一个缓存中（如 advisedBeans）。

方法调用时的匹配

在方法调用时，Spring 会根据当前调用的方法和目标对象的类型，从已经匹配的 Advisor 中进一步匹配出符合当前方法的 Advisor。

目的：动态构建拦截器链，以便在方法执行时应用相应的拦截器。
过程：
Spring 会调用 getInterceptorsAndDynamicInterceptionAdvice 方法，获取与当前方法匹配的拦截器。
通过切点（Pointcut）进一步过滤出符合当前方法的 Advisor。

Bean后置处理器中Advisor匹配流程

这个流程主要是在spring容器的初始化阶段，下面详细解析一下postProcessAfterInitialization的源码，注释贴在代码上

@Override
public Object postProcessAfterInitialization(@Nullable Object bean, String beanName) {if (bean != null) {// 根据bean.getClass()和beanName构建缓存keyObject cacheKey = getCacheKey(bean.getClass(), beanName);// 检查bean是否已经被处理if (this.earlyProxyReferences.remove(cacheKey) != bean) {// 如果需要代理，就包装beanreturn wrapIfNecessary(bean, beanName, cacheKey);}}return bean;
}protected Object wrapIfNecessary(Object bean, String beanName, Object cacheKey) {// 已经处理过的bean直接返回if (StringUtils.hasLength(beanName) && this.targetSourcedBeans.contains(beanName)) {return bean;}if (Boolean.FALSE.equals(this.advisedBeans.get(cacheKey))) {return bean;}// 跳过特定bean的检查代码...// 为给定bean获取适用的Advisor - 关键步骤！Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(bean.getClass(), beanName, null);// 如果找到了合适的Advisor，创建代理if (specificInterceptors != DO_NOT_PROXY) {this.advisedBeans.put(cacheKey, Boolean.TRUE);// 创建代理的核心方法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;
}
@Override
protected Object[] getAdvicesAndAdvisorsForBean(Class<?> beanClass, String beanName, @Nullable TargetSource targetSource) {// 查找匹配当前bean的AdvisorsList<Advisor> advisors = findEligibleAdvisors(beanClass, beanName);if (advisors.isEmpty()) {return DO_NOT_PROXY;}return advisors.toArray();
}protected List<Advisor> findEligibleAdvisors(Class<?> beanClass, String beanName) {// 获取所有候选AdvisorList<Advisor> candidateAdvisors = findCandidateAdvisors();// 过滤出可以应用到当前bean的AdvisorList<Advisor> eligibleAdvisors = findAdvisorsThatCanApply(candidateAdvisors, beanClass, beanName);// 扩展点，子类可以添加自定义的AdvisorextendAdvisors(eligibleAdvisors);if (!eligibleAdvisors.isEmpty()) {// 排序eligibleAdvisors = sortAdvisors(eligibleAdvisors);}return eligibleAdvisors;
}

方法调用时的匹配

Jdk

@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {Object oldProxy = null;boolean setProxyContext = false;// 获取被代理的对象TargetSource targetSource = this.advised.getTargetSource();Object target = null;try {// ... 省略一些特殊方法处理逻辑 ...Object retVal;// 处理通用拦截器逻辑if (this.advised.exposeProxy) {// 设置代理到ThreadLocaloldProxy = AopContext.setCurrentProxy(proxy);setProxyContext = true;}// 获取目标对象target = targetSource.getTarget();Class<?> targetClass = (target != null ? target.getClass() : null);// 获取当前方法的拦截器链 - 这里构建责任链!List<Object> chain = this.advised.getInterceptorsAndDynamicInterceptionAdvice(method, targetClass);// 如果拦截器链为空，直接反射调用目标方法if (chain.isEmpty()) {Object[] argsToUse = AopProxyUtils.adaptArgumentsIfNecessary(method, args);retVal = AopUtils.invokeJoinpointUsingReflection(target, method, argsToUse);}else {// 创建方法调用对象，包含了拦截器链MethodInvocation invocation = new ReflectiveMethodInvocation(proxy, target, method, args, targetClass, chain);// 执行责任链retVal = invocation.proceed();}// 返回结果处理return retVal;}// ... 异常处理和清理代码 ...
}

cglib

@Override
public Object intercept(Object proxy, Method method, Object[] args, MethodProxy methodProxy) throws Throwable {// ... 开头代码省略 ...// 获取目标对象target = targetSource.getTarget();Class<?> targetClass = (target != null ? target.getClass() : null);// 获取当前方法的拦截器链 - 责任链构建发生在这里!List<Object> chain = this.advised.getInterceptorsAndDynamicInterceptionAdvice(method, targetClass);Object retVal;// 如果没有拦截器，直接调用目标方法if (chain.isEmpty() && Modifier.isPublic(method.getModifiers())) {// ... 直接调用目标方法代码 ...}else {// 创建方法调用对象，包含拦截器链MethodInvocation invocation = new CglibMethodInvocation(proxy, target, method, args, targetClass, chain, methodProxy);// 执行拦截器链retVal = invocation.proceed();}// ... 返回处理代码 ...return retVal;
}

public List<Object> getInterceptorsAndDynamicInterceptionAdvice(Method method, @Nullable Class<?> targetClass) {MethodCacheKey cacheKey = new MethodCacheKey(method);// 尝试从缓存获取拦截器链List<Object> cached = this.methodCache.get(cacheKey);if (cached == null) {// 缓存未命中，创建拦截器链cached = this.advisorChainFactory.getInterceptorsAndDynamicInterceptionAdvice(this, method, targetClass);// 缓存结果this.methodCache.put(cacheKey, cached);}return cached;
}

小小总结

责任链不是在代理创建时构建的，而是在方法调用时动态构建，只为当前调用的方法构建相关的拦截器链，而不是为所有方法预先构建，通过 methodCache 缓存已构建的拦截器链，避免重复构建，根据方法和目标类在运行时判断哪些 Advisor 适用，形成调用链

Advisor 收集与排序

public List<Object> getInterceptorsAndDynamicInterceptionAdvice(Advised config, Method method, @Nullable Class<?> targetClass) {// 创建拦截器列表List<Object> interceptorList = new ArrayList<>(config.getAdvisors().length);// 获取目标类Class<?> actualClass = (targetClass != null ? targetClass : method.getDeclaringClass());// 判断是否存在引介增强boolean hasIntroductions = hasMatchingIntroductions(config, actualClass);// 注册表，用于缓存结果AdvisorAdapterRegistry registry = GlobalAdvisorAdapterRegistry.getInstance();// 遍历所有Advisorfor (Advisor advisor : config.getAdvisors()) {if (advisor instanceof PointcutAdvisor) {// 处理PointcutAdvisor类型的AdvisorPointcutAdvisor pointcutAdvisor = (PointcutAdvisor) advisor;if (config.isPreFiltered() || pointcutAdvisor.getPointcut().getClassFilter().matches(actualClass)) {// 将Advisor转换为拦截器MethodMatcher mm = pointcutAdvisor.getPointcut().getMethodMatcher();boolean match;// 检查方法是否匹配if (mm instanceof IntroductionAwareMethodMatcher) {match = ((IntroductionAwareMethodMatcher) mm).matches(method, actualClass, hasIntroductions);}else {match = mm.matches(method, actualClass);}if (match) {// 将Advisor转换成拦截器并添加到列表中MethodInterceptor[] interceptors = registry.getInterceptors(advisor);if (mm.isRuntime()) {// 运行时匹配的处理for (MethodInterceptor interceptor : interceptors) {interceptorList.add(new InterceptorAndDynamicMethodMatcher(interceptor, mm));}}else {// 直接添加到拦截器链interceptorList.addAll(Arrays.asList(interceptors));}}}}else if (advisor instanceof IntroductionAdvisor) {// 处理IntroductionAdvisor// ... existing code ...}else {// 处理其他类型的AdvisorInterceptor[] interceptors = registry.getInterceptors(advisor);interceptorList.addAll(Arrays.asList(interceptors));}}return interceptorList;
}

责任链执行过程

@Override
@Nullable
public Object proceed() throws Throwable {// 到达链末尾，调用目标方法if (this.currentInterceptorIndex == this.interceptorsAndDynamicMethodMatchers.size() - 1) {return invokeJoinpoint();}// 获取下一个拦截器Object interceptorOrInterceptionAdvice =this.interceptorsAndDynamicMethodMatchers.get(++this.currentInterceptorIndex);if (interceptorOrInterceptionAdvice instanceof InterceptorAndDynamicMethodMatcher) {// 动态匹配的拦截器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 {// 不匹配，跳过当前拦截器，继续下一个return proceed();}}else {// 执行普通拦截器return ((MethodInterceptor) interceptorOrInterceptionAdvice).invoke(this);}
}

AdvisorAdapter 将不同类型的 Advisor 统一适配为 MethodInterceptor

每个 Advisor 被转换为 MethodInterceptor 后，按顺序组成一个拦截器链，每个拦截器决定是执行自己的逻辑还是传递给下一个拦截器，会通过递增 currentInterceptorIndex 实现链的遍历，递归调用 proceed() 方法，实现责任传递

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