AOP Proxy 物件建立過程

阿新 • • 發佈：2019-01-24

由《Spring的IOC的原始碼解析（三）》繼續分析！首先介紹一下容器名稱空間控制代碼 ContextNamespaceHandler位置：spring-context-*.jar的META-INF/spring-handlersContextNamespaceHandler的init方法實現如下，registerBeanDefinitionParser("property-placeholder", new PropertyPlaceholderBeanDefinitionParser()); registerBeanDefinitionParser("property-override", new PropertyOverrideBeanDefinitionParser());

registerBeanDefinitionParser("annotation-config", new AnnotationConfigBeanDefinitionParser()); registerBeanDefinitionParser("component-scan", new ComponentScanBeanDefinitionParser()); registerBeanDefinitionParser("load-time-weaver", new LoadTimeWeaverBeanDefinitionParser()); registerBeanDefinitionParser("spring-configured", new SpringConfiguredBeanDefinitionParser());

registerBeanDefinitionParser("mbean-export", new MBeanExportBeanDefinitionParser()); registerBeanDefinitionParser("mbean-server", new MBeanServerBeanDefinitionParser());當ContextNamespaceHandler在解析標籤的時候，會呼叫每種標籤的解析器，解析過程就會呼叫AopNamespaceUtils為當前型別的標籤嘗試註冊相應的BPP；下邊給出一些示例，格式為：{標籤-標籤解析器-註冊的BPP} config/

ConfigBeanDefinitionParser/AspectJAwareAdvisorAutoProxyCreator aspectj-autoproxy/AspectJAutoProxyBeanDefinitionParser/AnnotationAwareAspectJAutoProxyCreator load-time-weaver/LoadTimeWeaverBeanDefinitionParser/沒有 component-scan/ComponentScanBeanDefinitionParser/沒有繼續分析AOP Proxy物件的生成過程！（1）獲取能夠處理目標類的advisor首先是呼叫AbstractAdvisorAutoProxyCreator.getAdvicesAndAdvisorsForBean()方法，然後呼叫：protected List<Advisor> findEligibleAdvisors(Class<?> beanClass, String beanName) { List<Advisor> candidateAdvisors = findCandidateAdvisors();//這個方法就是去beanFactory中查詢全部Advisor型別的bean，然後初始化；參見(a) List<Advisor> eligibleAdvisors = findAdvisorsThatCanApply(candidateAdvisors, beanClass, beanName);//參看(b) extendAdvisors(eligibleAdvisors); if (!eligibleAdvisors.isEmpty()) { eligibleAdvisors = sortAdvisors(eligibleAdvisors);//排序 } return eligibleAdvisors;}(a) 獲取並初始化Advisor，實現邏輯在BeanFactoryAdvisorRetrievalHelper.findAdvisorBeans()，其核心程式碼是：advisorNames = BeanFactoryUtils.beanNamesForTypeIncludingAncestors(this.beanFactory, Advisor.class, true, false);//查詢所有註冊在工廠中的Advisor的bean name or idList<Advisor> advisors = new LinkedList<>(); advisors.add(this.beanFactory.getBean(name, Advisor.class));//初始化Advisor，同時也會初始化Advisor中的advice，生成一個advice例項；(b) 往後又呼叫AopUtils.findAdvisorsThatCanApply()方法；findAdvisorsThatCanApply呼叫的核心函式就是：public static boolean canApply(Advisor advisor, Class<?> targetClass, boolean hasIntroductions) { if (advisor instanceof IntroductionAdvisor) { return ((IntroductionAdvisor) advisor).getClassFilter().matches(targetClass);//advisor是IntroductionAdvisor的匹配過程 } else if (advisor instanceof PointcutAdvisor) {//正常使用AOP，都是這種advisor PointcutAdvisor pca = (PointcutAdvisor) advisor; return canApply(pca.getPointcut(), targetClass, hasIntroductions);//advisor是PointcutAdvisor的匹配過程 } else { // It doesn't have a pointcut so we assume it applies. return true; //其他的advisor預設要處理 }}pointcut的匹配過程如下：public static boolean canApply(Pointcut pc, Class<?> targetClass, boolean hasIntroductions) { Assert.notNull(pc, "Pointcut must not be null"); if (!pc.getClassFilter().matches(targetClass)) {//獲取advisor中的pointcut物件，關於pointcut的使用，請參看《spring中的pointcut》；這裡相當於把所有的advisor中的pointcut都拿來匹配一遍，看看是否滿足 return false; } MethodMatcher methodMatcher = pc.getMethodMatcher(); if (methodMatcher == MethodMatcher.TRUE) { // No need to iterate the methods if we're matching any method anyway... return true; } IntroductionAwareMethodMatcher introductionAwareMethodMatcher = null; if (methodMatcher instanceof IntroductionAwareMethodMatcher) { introductionAwareMethodMatcher = (IntroductionAwareMethodMatcher) methodMatcher; } Set<Class<?>> classes = new LinkedHashSet<>(ClassUtils.getAllInterfacesForClassAsSet(targetClass)); classes.add(targetClass); for (Class<?> clazz : classes) { Method[] methods = ReflectionUtils.getAllDeclaredMethods(clazz); for (Method method : methods) { if ((introductionAwareMethodMatcher != null && introductionAwareMethodMatcher.matches(method, targetClass, hasIntroductions)) || methodMatcher.matches(method, targetClass)) { return true; } } } return false;}最終，返回所有適合代理類的advisor（2）建立AOP代理protected Object createProxy(Class<?> beanClass, @Nullable String beanName, @Nullable Object[] specificInterceptors, TargetSource targetSource) { if (this.beanFactory instanceof ConfigurableListableBeanFactory) { AutoProxyUtils.exposeTargetClass((ConfigurableListableBeanFactory) this.beanFactory, beanName, beanClass);//為bean設定屬性org.springframework.aop.framework.autoproxy.AutoProxyUtils.originalTargetClass，值是beanClass } ProxyFactory proxyFactory = new ProxyFactory();//代理工廠 proxyFactory.copyFrom(this);//為代理工廠設定proxyTargetClass，是否初始化等引數 if (!proxyFactory.isProxyTargetClass()) {//預設應該條件為true，進入if if (shouldProxyTargetClass(beanClass, beanName)) {//判斷是代理類，還是代理類的介面；判斷的邏輯就是看bean的定義中，屬性名為org.springframework.aop.framework.autoproxy.AutoProxyUtils.preserveTargetClass的屬性的值是否設定為了true。暫時只知道ConfigurationClassPostProcessor可以配置這個屬性為true；預設是false，即代理介面 proxyFactory.setProxyTargetClass(true);//代理目標類，標記proxyTargetClass=true } else { evaluateProxyInterfaces(beanClass, proxyFactory);//代理目標類的介面；如果是可以代理的介面，就把介面加入到ProxyFactory中，見(a) } } Advisor[] advisors = buildAdvisors(beanName, specificInterceptors);//合併共用和指定攔截器到advisor，可以把advisor叫做增強器；見(b) proxyFactory.addAdvisors(advisors);//這是增強器 proxyFactory.setTargetSource(targetSource);//設定例項物件，用於代理呼叫代理方法是使用 customizeProxyFactory(proxyFactory); proxyFactory.setFrozen(this.freezeProxy); if (advisorsPreFiltered()) { proxyFactory.setPreFiltered(true); } return proxyFactory.getProxy(getProxyClassLoader());//生成代理物件，見(c)}(a)可代理的介面的定義至少有一個方法的介面或者protected boolean isInternalLanguageInterface(Class<?> ifc) { return (ifc.getName().equals("groovy.lang.GroovyObject") || ifc.getName().endsWith(".cglib.proxy.Factory") || ifc.getName().endsWith(".bytebuddy.MockAccess"));}返回false的介面或者protected boolean isConfigurationCallbackInterface(Class<?> ifc) { return (InitializingBean.class == ifc || DisposableBean.class == ifc || Closeable.class == ifc || AutoCloseable.class == ifc || ObjectUtils.containsElement(ifc.getInterfaces(), Aware.class));}返回false的介面(b)合併共用和指定攔截器到advisor，預設沒有共用攔截器protected Advisor[] buildAdvisors(@Nullable String beanName, @Nullable Object[] specificInterceptors) { Advisor[] commonInterceptors = resolveInterceptorNames();//把定義的攔截器包裝成advisor，返回 List<Object> allInterceptors = new ArrayList<>(); if (specificInterceptors != null) { allInterceptors.addAll(Arrays.asList(specificInterceptors)); if (commonInterceptors.length > 0) { if (this.applyCommonInterceptorsFirst) {//預設把攔截器的執行放在最前邊執行 allInterceptors.addAll(0, Arrays.asList(commonInterceptors)); } else { allInterceptors.addAll(Arrays.asList(commonInterceptors)); } } } Advisor[] advisors = new Advisor[allInterceptors.size()]; for (int i = 0; i < allInterceptors.size(); i++) { advisors[i] = this.advisorAdapterRegistry.wrap(allInterceptors.get(i));//包裝advisor，適配方法是DefaultAdvisorAdapterRegistry.wrap() } return advisors;}適配過程：public Advisor wrap(Object adviceObject) throws UnknownAdviceTypeException { if (adviceObject instanceof Advisor) { return (Advisor) adviceObject;//如果是advisor物件，不用處理 } if (!(adviceObject instanceof Advice)) {//只能是advicor or advice throw new UnknownAdviceTypeException(adviceObject); } Advice advice = (Advice) adviceObject;//advice物件都包裝成DefaultPointcutAdvisor物件 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);}(c)代理工廠生成代理物件這裡一直沒有讀懂aopProxyFactory物件的例項話，這裡假定aopProxyFactory就是一個DefaultAopProxyFactory物件；DefaultAopProxyFactory中生成代理物件的方法：public AopProxy createAopProxy(AdvisedSupport config) throws AopConfigException { if (config.isOptimize() || config.isProxyTargetClass() || hasNoUserSuppliedProxyInterfaces(config)) { Class<?> targetClass = config.getTargetClass(); if (targetClass == null) { throw new AopConfigException("TargetSource cannot determine target class: " + "Either an interface or a target is required for proxy creation."); } if (targetClass.isInterface() || Proxy.isProxyClass(targetClass)) { return new JdkDynamicAopProxy(config); } return new ObjenesisCglibAopProxy(config);//類代理，分析過程見【1】 } else { return new JdkDynamicAopProxy(config);//介面代理,分析過程見【2】 }}如果不是代理介面，就使用CGLIB位元組碼動態代理；否則使用JDK的動態代理。【1】jdk動態代理JdkDynamicAopProxy.getProxy()方法：public Object getProxy(@Nullable ClassLoader classLoader) { findDefinedEqualsAndHashCodeMethods(proxiedInterfaces); return Proxy.newProxyInstance(classLoader, proxiedInterfaces, this);}所以，返回的代理物件就是JDK的Proxy.newProxyInstance方法生成的，而且引數需要的InvocationHandler物件就是當前的JdkDynamicAopProxy物件；我們知道，JDK動態代理的實現原理就是代理物件在執行目標方法的時候，會檢查當前方法是否被代理？如果被代理，那麼就執行InvocationHandler的invoke方法代替；下邊看看JDK動態代理模式下的，代理物件真正執行方法時，切面織入方法的功能是怎樣實現的。JdkDynamicAopProxy實現InvocationHandler介面，invoke方法的核心邏輯是：List<Object> chain = this.advised.getInterceptorsAndDynamicInterceptionAdvice(method, targetClass);//chain是InterceptorAndDynamicMethodMatcher連結串列；參見{1}if (chain.isEmpty()) {//跳過熱交換，只是執行目標類的方法，method.invoke Object[] argsToUse = AopProxyUtils.adaptArgumentsIfNecessary(method, args); retVal = AopUtils.invokeJoinpointUsingReflection(target, method, argsToUse);}else {//建立 method invocation invocation = new ReflectiveMethodInvocation(proxy, target, method, args, targetClass, chain);//反射方法處理過程，target引數就是被代理類的例項//執行攔截器鏈和方法，參看{4} retVal = invocation.proceed();}{1}把增強器advisors包裝成mathodMatcher鏈的過程呼叫DefaultAdvisorChainFactory.getInterceptorsAndDynamicInterceptionAdvice()方法，核心程式碼如下：MethodInterceptor[] interceptors = registry.getInterceptors(advisor);//registry是DefaultAdvisorAdapterRegistry例項，這裡就是把advisor中的advice包裝成MethodInterceptor，見{2}MethodMatcher mm = pointcutAdvisor.getPointcut().getMethodMatcher();//獲得匹配方法；參見{3}if (MethodMatchers.matches(mm, method, actualClass, hasIntroductions)) { if (mm.isRuntime()) { for (MethodInterceptor interceptor : interceptors) { interceptorList.add(new InterceptorAndDynamicMethodMatcher(interceptor, mm));//採用組合模式，將攔截器物件和匹配方法物件放在InterceptorAndDynamicMethodMatcher物件中，得到返回值物件； } } else { interceptorList.addAll(Arrays.asList(interceptors)); }}{2}例如：下邊是預設包裝關係MethodBeforeAdvice MethodBeforeAdviceInterceptorAfterReturningAdvice AfterReturningAdviceInterceptorThrowsAdvice ThrowsAdviceInterceptor根據advice的解析過程可知，before 型別的advice的目標類就是MethodBeforeAdvice類的子類；advice的pointcut依賴指定的目標類是AspectJExpressionPointcut{3}由{2}的說明可知，MethodMatcher方法物件的獲取過程就是獲取AspectJExpressionPointcut物件；在pointcut例項化時會解析expression表示式，邏輯如下：private PointcutExpression buildPointcutExpression(@Nullable ClassLoader classLoader) { PointcutParser parser = initializePointcutParser(classLoader); PointcutParameter[] pointcutParameters = new PointcutParameter[this.pointcutParameterNames.length]; for (int i = 0; i < pointcutParameters.length; i++) { pointcutParameters[i] = parser.createPointcutParameter( this.pointcutParameterNames[i], this.pointcutParameterTypes[i]); } return parser.parsePointcutExpression(replaceBooleanOperators(resolveExpression()), this.pointcutDeclarationScope, pointcutParameters);//expression的物件類是PointcutExpressionImpl}需要說明的是，AspectJExpressionPointcut類實現IntroductionAwareMethodMatcher、MethodMatcher介面；{4}迴圈處理攔截器鏈，使用matcher匹配，然後呼叫攔截器的invoke方法if (this.currentInterceptorIndex == this.interceptorsAndDynamicMethodMatchers.size() - 1) {//所有 advice都呼叫完之後，呼叫這裡，但是after advice是逆向呼叫的，所有代理方法會在after adviec之前之前執行 return invokeJoinpoint();}//other codeif (dm.methodMatcher.matches(this.method, this.targetClass, this.arguments)) {//匹配；見{5}分析 return dm.interceptor.invoke(this);//呼叫；參見{6}}else { // Dynamic matching failed. // Skip this interceptor and invoke the next in the chain. return proceed();//如果匹配失敗，跳過當前advisor，繼續下一個}{5}可知匹配過程就是AspectJExpressionPointcut的matches方法邏輯過程；{6}看看典型advice的處理過程before advice的MethodBeforeAdviceInterceptor呼叫過程如下：public Object invoke(MethodInvocation mi) throws Throwable { this.advice.before(mi.getMethod(), mi.getArguments(), mi.getThis() );//AspectJMethodBeforeAdvice.before方法，這裡就是呼叫before通知在切面裡定義的執行方法 return mi.proceed();//跳轉到ReflectiveMethodInvocation.proceed()方法，實現呼叫多個advice的功能}AspectJMethodBeforeAdvice.before(){ invokeAdviceMethod(getJoinPointMatch(), null, null);}after-returning的AfterReturningAdviceInterceptor呼叫過程如下：public Object invoke(MethodInvocation mi) throws Throwable { Object retVal = mi.proceed();//跳轉到ReflectiveMethodInvocation.proceed()方法，實現呼叫多個advice的功能 this.advice.afterReturning(retVal, mi.getMethod(), mi.getArguments(), mi.getThis());//呼叫後處理方法 return retVal;}AspectJAfterReturningAdvice.afterReturning(){ if (shouldInvokeOnReturnValueOf(method, returnValue)) { invokeAdviceMethod(getJoinPointMatch(), returnValue, null); }}可見，所有的advice都是先執行before advice 再執行after-returning advice ；所有的advice都執行完之後，執行被代理的方法；因為after advice是逆向呼叫的，所以被代理的方法會在after advice之前呼叫。around advice通知是怎麼實現的呢？看到DefaultAdvisorAdapterRegistry類的wrap方法：if (adviceObject instanceof Advisor) {//advice 不是advisor，跳過 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);//advice 都在這裡處理，被適配成DefaultPointcutAdvisor物件}再看攔截器方法鏈——也就是advice的方法封裝，也是DefaultAdvisorAdapterRegistry的方法：public MethodInterceptor[] getInterceptors(Advisor advisor) throws UnknownAdviceTypeException { List<MethodInterceptor> interceptors = new ArrayList<>(3); Advice advice = advisor.getAdvice(); if (advice instanceof MethodInterceptor) {//around advice的處理類AspectJAroundAdvice實現了MethodInterceptor介面，所以就是around advice的方法攔截器就是AspectJAroundAdvice物件 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[interceptors.size()]);}下邊看方法攔截器的呼叫過程：public Object invoke(MethodInvocation mi) throws Throwable { if (!(mi instanceof ProxyMethodInvocation)) { throw new IllegalStateException("MethodInvocation is not a Spring ProxyMethodInvocation: " + mi); } ProxyMethodInvocation pmi = (ProxyMethodInvocation) mi; ProceedingJoinPoint pjp = lazyGetProceedingJoinPoint(pmi);//返回一個MethodInvocationProceedingJoinPoint物件，這個物件就是在切面中定義的around方法的實參 JoinPointMatch jpm = getJoinPointMatch(pmi); return invokeAdviceMethod(pjp, jpm, null, null);//呼叫父類的方法；參見{7}}{7}advice方法的呼叫，核心就是下邊這一句this.aspectJAdviceMethod.invoke(this.aspectInstanceFactory.getAspectInstance(), actualArgs);解釋：this.aspectJAdviceMethod獲取advice指定方法的Method物件；this.aspectInstanceFactory.getAspectInstance()獲取一個advice所屬切面aspect的例項；actualArgs是方法引數；也就是method.invoke(object,args)而已；before advice，after-returning advice在呼叫advice方法時，會呼叫下一個advice的方法，但是around advice沒有這樣做；事實上，around advice呼叫下一個advice方法的語句在，切面實現的方法中，從這一點上將，只有around advice的方法引數是必須要被使用的；而在around advice方法中，可以在point.proceed();語句前後加增強語句，正是“環繞”的意義所在；需要注意的是，如果有多個around advice被執行，那麼point.proceed();語句後面的增強語句的執行過程像堆疊呼叫，即先被呼叫的後被執行；到此，基於JDK的動態代理實現的AOP過程就分析完成了！【2】位元組碼代理ObjenesisCglibAopProxy.getProxy()方法，暫時不研究了！

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