AOP實現中，可以看到三個主要的步驟，一個是代理對象的生成，然後是攔截器的作用，然後是Aspect編織的實現。
ProxyFactoryBean生成AopProxy
ProxyFactoryBean生成AOP proxy
<code> 1 /** 2 * Return a proxy. Invoked when clients obtain beans from this factory bean. 3 * Create an instance of the AOP proxy to be returned by this factory. 4 * The instance will be cached for a singleton, and create on each call to 5 * <code>getObject()/<code> for a proxy. 6 * @return a fresh AOP proxy reflecting the current state of this factory 7 */ 8 public Object getObject() throws BeansException { 9 initializeAdvisorChain();10 if (isSingleton()) {11 return getSingletonInstance();12 }13 else {14 if (this.targetName == null) {15 logger.warn("Using non-singleton proxies with singleton targets is often undesirable. " +16 "Enable prototype proxies by setting the 'targetName' property.");17 }18 return newPrototypeInstance();19 }20 }/<code>初始化Advisor chain
<code> 1 /** 2 * Create the advisor (interceptor) chain. Aadvisors that are sourced 3 * from a BeanFactory will be refreshed each time a new prototype instance 4 * is added. Interceptors added programmatically through the factory API 5 * are unaffected by such changes. 6 */ 7 private synchronized void initializeAdvisorChain() throws AopConfigException, BeansException { 8 if (this.advisorChainInitialized) { 9 return;10 }11 12 if (!ObjectUtils.isEmpty(this.interceptorNames)) {13 if (this.beanFactory == null) {14 throw new IllegalStateException("No BeanFactory available anymore (probably due to serialization) " +15 "- cannot resolve interceptor names " + Arrays.asList(this.interceptorNames));16 }17 18 // Globals can't be last unless we specified a targetSource using the property...19 if (this.interceptorNames[this.interceptorNames.length - 1].endsWith(GLOBAL_SUFFIX) &&20 this.targetName == null && this.targetSource == EMPTY_TARGET_SOURCE) {21 throw new AopConfigException("Target required after globals");22 }23 24 // Materialize interceptor chain from bean names.25 for (int i = 0; i < this.interceptorNames.length; i++) {26 String name = this.interceptorNames[i];27 if (logger.isTraceEnabled()) {28 logger.trace("Configuring advisor or advice '" + name + "'");29 }30 31 if (name.endsWith(GLOBAL_SUFFIX)) {32 if (!(this.beanFactory instanceof ListableBeanFactory)) {33 throw new AopConfigException(34 "Can only use global advisors or interceptors with a ListableBeanFactory");35 }36 addGlobalAdvisor((ListableBeanFactory) this.beanFactory,37 name.substring(0, name.length() - GLOBAL_SUFFIX.length()));38 }39 40 else {41 // If we get here, we need to add a named interceptor.42 // We must check if it's a singleton or prototype.43 Object advice = null;44 if (this.singleton || this.beanFactory.isSingleton(this.interceptorNames[i])) {45 // Add the real Advisor/Advice to the chain.46 advice = this.beanFactory.getBean(this.interceptorNames[i]);47 }48 else {49 // It's a prototype Advice or Advisor: replace with a prototype.50 // Avoid unnecessary creation of prototype bean just for advisor chain initialization.51 advice = new PrototypePlaceholderAdvisor(this.interceptorNames[i]);52 }53 addAdvisorOnChainCreation(advice, this.interceptorNames[i]);54 }55 }56 }57 58 this.advisorChainInitialized = true;59 }/<code>增加advisor chain（AdvisedSupport.java）
<code> 1 private void addAdvisorInternal(int pos, Advisor advisor) throws AopConfigException { 2 Assert.notNull(advisor, "Advisor must not be null"); 3 if (isFrozen()) { 4 throw new AopConfigException("Cannot add advisor: Configuration is frozen."); 5 } 6 if (pos > this.advisors.size()) { 7 throw new IllegalArgumentException( 8 "Illegal position " + pos + " in advisor list with size " + this.advisors.size()); 9 }10 this.advisors.add(pos, advisor);11 updateAdvisorArray();12 adviceChanged();13 }/<code>Spring AOP中攔截器鏈
1.開始步驟--獲取AopProxy主流程
ProxyCreatorSupport.java
<code> /** * Subclasses should call this to get a new AOP proxy. They should not * create an AOP proxy with <code>this/<code> as an argument. */ protected final synchronized AopProxy createAopProxy() { if (!this.active) { activate(); } return getAopProxyFactory().createAopProxy(this); }/<code>2.獲取AopProxy實現 --DefaultAopProxyFactory.java
ProxyFactoryBean類繼承了AdvisedSupport類，後者繼承了ProxyConfig類並定義了操作advisor 和interceptor的接口，以支持AOP。當BeanFactory實例化ProxyFactoryBean時，根據配置文件的定義將關於 advice，pointcut，advisor，所代理的接口和接口實現類的所有信息傳給ProxyFactoryBean。
當客戶程序調用BeanFactory的getBean方法時，ProxyFactory使用JdkDynamicAopProxy實例化 BeanImpl類，並用JdkDynamicAopProxy的invoke方法執行advice。至於執行advice的時機，由 ProxyFactoryBean調用RegexpMethodPointcutAdvisor進行判斷。
<code> 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()) { return new JdkDynamicAopProxy(config); } if (!cglibAvailable) { throw new AopConfigException( "Cannot proxy target class because CGLIB2 is not available. " + "Add CGLIB to the class path or specify proxy interfaces."); } return CglibProxyFactory.createCglibProxy(config); } else { return new JdkDynamicAopProxy(config); } }/<code>3.獲取AopProxy的執行路徑
<code> public Object getProxy(ClassLoader classLoader) { if (logger.isDebugEnabled()) { logger.debug("Creating JDK dynamic proxy: target source is " + this.advised.getTargetSource()); } Class[] proxiedInterfaces = AopProxyUtils.completeProxiedInterfaces(this.advised); findDefinedEqualsAndHashCodeMethods(proxiedInterfaces); return Proxy.newProxyInstance(classLoader, proxiedInterfaces, this); }/<code>4.激發攔截器鏈主過程
<code> 1 /** 2 * Implementation of <code>InvocationHandler.invoke/<code>. 3 *Callers will see exactly the exception thrown by the target, 4 * unless a hook method throws an exception. 5 */ 6 public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { 7 MethodInvocation invocation = null; 8 Object oldProxy = null; 9 boolean setProxyContext = false;10 11 TargetSource targetSource = this.advised.targetSource;12 Class targetClass = null;13 Object target = null;14 15 try {16 if (!this.equalsDefined && AopUtils.isEqualsMethod(method)) {17 // The target does not implement the equals(Object) method itself.18 return (equals(args[0]) ? Boolean.TRUE : Boolean.FALSE);19 }20 if (!this.hashCodeDefined && AopUtils.isHashCodeMethod(method)) {21 // The target does not implement the hashCode() method itself.22 return new Integer(hashCode());23 }24 if (!this.advised.opaque && method.getDeclaringClass().isInterface() &&25 method.getDeclaringClass().isAssignableFrom(Advised.class)) {26 // Service invocations on ProxyConfig with the proxy config...27 return AopUtils.invokeJoinpointUsingReflection(this.advised, method, args);28 }29 30 Object retVal = null;31 32 if (this.advised.exposeProxy) {33 // Make invocation available if necessary.34 oldProxy = AopContext.setCurrentProxy(proxy);35 setProxyContext = true;36 }37 38 // May be <code>null/<code>. Get as late as possible to minimize the time we "own" the target,39 // in case it comes from a pool.40 target = targetSource.getTarget();41 if (target != null) {42 targetClass = target.getClass();43 }44 45 // Get the interception chain for this method.46 List chain = this.advised.getInterceptorsAndDynamicInterceptionAdvice(method, targetClass);47 48 // Check whether we have any advice. If we don't, we can fallback on direct49 // reflective invocation of the target, and avoid creating a MethodInvocation.50 if (chain.isEmpty()) {51 // We can skip creating a MethodInvocation: just invoke the target directly52 // Note that the final invoker must be an InvokerInterceptor so we know it does53 // nothing but a reflective operation on the target, and no hot swapping or fancy proxying.54 retVal = AopUtils.invokeJoinpointUsingReflection(target, method, args);55 }56 else {57 // We need to create a method invocation...58 invocation = new ReflectiveMethodInvocation(proxy, target, method, args, targetClass, chain);59 // Proceed to the joinpoint through the interceptor chain.60 retVal = invocation.proceed();61 }62 63 // Massage return value if necessary.64 if (retVal != null && retVal == target && method.getReturnType().isInstance(proxy) &&65 !RawTargetAccess.class.isAssignableFrom(method.getDeclaringClass())) {66 // Special case: it returned "this" and the return type of the method67 // is type-compatible. Note that we can't help if the target sets68 // a reference to itself in another returned object.69 retVal = proxy;70 }71 return retVal;72 }73 finally {74 if (target != null && !targetSource.isStatic()) {75 // Must have come from TargetSource.76 targetSource.releaseTarget(target);77 }78 if (setProxyContext) {79 // Restore old proxy.80 AopContext.setCurrentProxy(oldProxy);81 }82 }83 }
/<code>
5.獲取攔截器鏈DefaultAdvisorChainFactory.java
<code> public List getInterceptorsAndDynamicInterceptionAdvice(Advised config, Method method, Class targetClass) { // This is somewhat tricky... we have to process introductions first, // but we need to preserve order in the ultimate list. List interceptorList = new ArrayList(config.getAdvisors().length); boolean hasIntroductions = hasMatchingIntroductions(config, targetClass); AdvisorAdapterRegistry registry = GlobalAdvisorAdapterRegistry.getInstance(); Advisor[] advisors = config.getAdvisors(); for (int i = 0; i < advisors.length; i++) { Advisor advisor = advisors[i]; if (advisor instanceof PointcutAdvisor) { // Add it conditionally. PointcutAdvisor pointcutAdvisor = (PointcutAdvisor) advisor; if (config.isPreFiltered() || pointcutAdvisor.getPointcut().getClassFilter().matches(targetClass)) { MethodInterceptor[] interceptors = registry.getInterceptors(advisor); MethodMatcher mm = pointcutAdvisor.getPointcut().getMethodMatcher(); if (MethodMatchers.matches(mm, method, targetClass, hasIntroductions)) { if (mm.isRuntime()) { // Creating a new object instance in the getInterceptors() method // isn't a problem as we normally cache created chains. for (int j = 0; j < interceptors.length; j++) { interceptorList.add(new InterceptorAndDynamicMethodMatcher(interceptors[j], mm)); } } else { interceptorList.addAll(Arrays.asList(interceptors)); } } } } else if (advisor instanceof IntroductionAdvisor) { IntroductionAdvisor ia = (IntroductionAdvisor) advisor; if (config.isPreFiltered() || ia.getClassFilter().matches(targetClass)) { Interceptor[] interceptors = registry.getInterceptors(advisor); interceptorList.addAll(Arrays.asList(interceptors)); } } else { Interceptor[] interceptors = registry.getInterceptors(advisor); interceptorList.addAll(Arrays.asList(interceptors)); } } return interceptorList; }/<code>6.激發攔截鏈工作實現 ---ReflectiveMethodInvocation.java
<code> 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; if (dm.methodMatcher.matches(this.method, this.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); } }/<code>Spring AOP中Aspect編織的實現
1.前面我們談到攔截器起作用時，實現代碼（ReflectiveMethodInvocation.java）如下：
<code> 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; if (dm.methodMatcher.matches(this.method, this.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); } }/<code>2.前置Advice MethodBeforeAdviceInterceptor.java
<code> public Object invoke(MethodInvocation mi) throws Throwable { this.advice.before(mi.getMethod(), mi.getArguments(), mi.getThis() ); return mi.proceed(); }/<code>3.後置Advice AfterReturningAdviceInterceptor.java
<code> public Object invoke(MethodInvocation mi) throws Throwable { Object retVal = mi.proceed(); this.advice.afterReturning(retVal, mi.getMethod(), mi.getArguments(), mi.getThis()); return retVal; }/<code>總結
沒圖沒真相
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