在理解Spring AOP的实现之前,先理解一些Spring AOP的相干概念
AOP的相干概念
在应用Spring进行AOP相干的编程时,咱们常常应用Advice (告诉), PointCut (切点), Advisor (告诉器)来实现咱们须要的性能。
Advice
Advice是AOP联盟定义的一个接口,定义了咱们能够在切点做些什么,即咱们心愿织入的加强逻辑,为切面加强提供织入的入口。在Spring中,Advice作为一个对立的接口,Spring在Advice的根底上定义了具体的告诉类型,比方,
- BeforeAdvice: 前置加强接口,在指标办法调用之前回调。
- AfterAdvice : 后置加强接口,在指标办法调用完结并胜利返回时回调。
- ThrowAdvice : 在抛出异样时回调。
- Interceptor: 示意一个通用的拦截器,能够在办法的调用前后进行加强。
- DynamicIntroductionAdvice: 与下面的Advice和Interceptor不同,DynamicIntroductionAdvice不对办法进行加强,而是动静的引入新的接口实现。咱们能够为指标类增加一个接口的实现(原来指标类未实现某个接口),那么通过DynamicIntroductionAdvice加强能够为指标类创立实现某接口的代理。
Pointcut
Pointcut 决定Advice能够作用于哪些连接点,即通过Pointcut咱们能够定义须要加强的办法的汇合。这些办法的汇合能够通过Pointcut中定义的规定来选取,当办法合乎Pointcut定义的规定时,返回true。这些规定可是正则表达式,也能够是字符串的匹配等。
Spring定义了Pointcut的接口,Pointcut接口中定义了用于获取类过滤器和办法匹配器的形象办法。
public interface Pointcut { /** * Return the ClassFilter for this pointcut. * @return the ClassFilter (never {@code null}) */ ClassFilter getClassFilter(); /** * Return the MethodMatcher for this pointcut. * @return the MethodMatcher (never {@code null}) */ MethodMatcher getMethodMatcher(); /** * Canonical Pointcut instance that always matches. */ Pointcut TRUE = TruePointcut.INSTANCE;}
然而有了类过滤器和办法匹配器,咱们还须要晓得如何应用类过滤器和办法匹配器,因而在实现Pointcut的同时也须要实现MethodMatcher。MethodMatcher定义了matches办法,即用于规定匹配的办法。
public interface MethodMatcher { /** * Perform static checking whether the given method matches. * <p>If this returns {@code false} or if the {@link #isRuntime()} * method returns {@code false}, no runtime check (i.e. no * {@link #matches(java.lang.reflect.Method, Class, Object[])} call) * will be made. * @param method the candidate method * @param targetClass the target class * @return whether or not this method matches statically */ boolean matches(Method method, Class<?> targetClass); /** * Is this MethodMatcher dynamic, that is, must a final call be made on the * {@link #matches(java.lang.reflect.Method, Class, Object[])} method at * runtime even if the 2-arg matches method returns {@code true}? * <p>Can be invoked when an AOP proxy is created, and need not be invoked * again before each method invocation, * @return whether or not a runtime match via the 3-arg * {@link #matches(java.lang.reflect.Method, Class, Object[])} method * is required if static matching passed */ boolean isRuntime(); /** * Check whether there a runtime (dynamic) match for this method, * which must have matched statically. * <p>This method is invoked only if the 2-arg matches method returns * {@code true} for the given method and target class, and if the * {@link #isRuntime()} method returns {@code true}. Invoked * immediately before potential running of the advice, after any * advice earlier in the advice chain has run. * @param method the candidate method * @param targetClass the target class * @param args arguments to the method * @return whether there's a runtime match * @see MethodMatcher#matches(Method, Class) */ boolean matches(Method method, Class<?> targetClass, Object... args); /** * Canonical instance that matches all methods. */ MethodMatcher TRUE = TrueMethodMatcher.INSTANCE;}
下图给出了Spring中一些Pointcut的继承关系,能够看到具体的实现都集成了Pointcut接口和MethodMatcher接口。
Advisor
后面介绍了Advice的加强逻辑,Pointcut定义了办法的汇合,然而哪些办法应用什么样的加强逻辑仍旧没有关联起来,Advisor就是将Advice和Pointcut联合起来,通过Advisor,能够定义在某个Pointcut连接点上应用哪个Advice。
Spring 提供了一个DefaultPointcutAdvisor, 在DefaultPointcutAdvisor中有两个属性,别离为advice和pointcut用来配置Advice 和Pointcut。 其实现如下所示。
public class DefaultPointcutAdvisor extends AbstractGenericPointcutAdvisor implements Serializable { private Pointcut pointcut = Pointcut.TRUE; /** * Create an empty DefaultPointcutAdvisor. * <p>Advice must be set before use using setter methods. * Pointcut will normally be set also, but defaults to {@code Pointcut.TRUE}. */ public DefaultPointcutAdvisor() { } /** * Create a DefaultPointcutAdvisor that matches all methods. * <p>{@code Pointcut.TRUE} will be used as Pointcut. * @param advice the Advice to use */ public DefaultPointcutAdvisor(Advice advice) { this(Pointcut.TRUE, advice); } /** * Create a DefaultPointcutAdvisor, specifying Pointcut and Advice. * @param pointcut the Pointcut targeting the Advice * @param advice the Advice to run when Pointcut matches */ public DefaultPointcutAdvisor(Pointcut pointcut, Advice advice) { this.pointcut = pointcut; setAdvice(advice); } /** * Specify the pointcut targeting the advice. * <p>Default is {@code Pointcut.TRUE}. * @see #setAdvice */ public void setPointcut(@Nullable Pointcut pointcut) { this.pointcut = (pointcut != null ? pointcut : Pointcut.TRUE); } @Override public Pointcut getPointcut() { return this.pointcut; } @Override public String toString() { return getClass().getName() + ": pointcut [" + getPointcut() + "]; advice [" + getAdvice() + "]"; }}
Spring AOP的实现
后面曾经介绍了Spring AOP的相干概念,然而Spring AOP是如何对办法的调用进行拦挡的呢?上面就Spring AOP的实现进行剖析。
同样以Spring中的单元测试开始Spring AOP的实现剖析。
通过以下代码开始Spring AOP的实现剖析。
@Testpublic void testProxyFactory() { TestBean target = new TestBean(); ProxyFactory pf = new ProxyFactory(target); NopInterceptor nop = new NopInterceptor(); CountingBeforeAdvice cba = new CountingBeforeAdvice(); Advisor advisor = new DefaultPointcutAdvisor(cba); pf.addAdvice(nop); pf.addAdvisor(advisor); ITestBean proxied = (ITestBean) pf.getProxy(); proxied.setAge(5); assertThat(cba.getCalls()).isEqualTo(1); assertThat(nop.getCount()).isEqualTo(1); assertThat(pf.removeAdvisor(advisor)).isTrue(); assertThat(proxied.getAge()).isEqualTo(5); assertThat(cba.getCalls()).isEqualTo(1); assertThat(nop.getCount()).isEqualTo(2);}
上述的代码中创立了一个TestBean,NopInterceptor, CountingBeforeAdvice对象,并应用TestBean初始化了ProxyFactory,CountingBeforeAdvice对象初始化DefaultPointcutAdvisor,同时将NopInterceptorDefaultPointcutAdvisor增加到ProxyFactory中。能够看到上述的代码中没有指明Pointcut, 也就意味着应用了默认的Pointcut.TRUE, 即对所有的办法都进行加强。
首先来看一下ProxyFactory的继承关系。
从上往下看,首先是TargetClassAware, 定义了一个getTargetClass()办法用来获取指标对象的Class,Advised继承了该接口,Advised接口定义了获取和设置AOP 代理工厂(Aop proxy factory)配置的办法,具体代码如下:
public interface Advised extends TargetClassAware { boolean isFrozen(); boolean isProxyTargetClass(); Class<?>[] getProxiedInterfaces(); boolean isInterfaceProxied(Class<?> intf); void setTargetSource(TargetSource targetSource); TargetSource getTargetSource(); void setExposeProxy(boolean exposeProxy); boolean isExposeProxy(); void setPreFiltered(boolean preFiltered); boolean isPreFiltered(); Advisor[] getAdvisors(); default int getAdvisorCount() { return getAdvisors().length; } void addAdvisor(Advisor advisor) throws AopConfigException; void addAdvisor(int pos, Advisor advisor) throws AopConfigException; boolean removeAdvisor(Advisor advisor); void removeAdvisor(int index) throws AopConfigException; int indexOf(Advisor advisor); boolean replaceAdvisor(Advisor a, Advisor b) throws AopConfigException; void addAdvice(Advice advice) throws AopConfigException; void addAdvice(int pos, Advice advice) throws AopConfigException; boolean removeAdvice(Advice advice); int indexOf(Advice advice); String toProxyConfigString();}
而ProxyConfig则保留了AOP 代理工厂的局部属性,能够看成是一个数据基类,如下:
public class ProxyConfig implements Serializable { ... private boolean proxyTargetClass = false; private boolean optimize = false; boolean opaque = false; boolean exposeProxy = false; private boolean frozen = false; ...}
AdvisedSupport 继承了ProxyConfig同时实现了Advised接口,封装了AOP对Advice和Advisor的相干操作。
/** The AdvisorChainFactory to use. */AdvisorChainFactory advisorChainFactory = new DefaultAdvisorChainFactory();/** Cache with Method as key and advisor chain List as value. */private transient Map<MethodCacheKey, List<Object>> methodCache;/** * Interfaces to be implemented by the proxy. Held in List to keep the order * of registration, to create JDK proxy with specified order of interfaces. */private List<Class<?>> interfaces = new ArrayList<>();/** * List of Advisors. If an Advice is added, it will be wrapped * in an Advisor before being added to this List. */private List<Advisor> advisors = new ArrayList<>();
ProxyCreatorSupport 则提供了设置ProxyFactory和创立代理对象的办法,创立的具体的代理对象则交给具体的ProxyFactory实现。
最上面的则是三个具体的ProxyFactory的实现,别离为:
- ProxyFactory,能够在IOC容器中应用申明式配置AOP。
- ProxyFactoryBean,须要编程式的应用AOP
- AspectProxyFactory, 对于应用AspectJ的AOP利用,集成了Spring和AspectJ。
理解了ProxyFactory的继承关系后,持续往下看,咱们曾经晓得了具体的代理的对象的创立交给具体的ProxyFactory。
咱们次要关注上面用于获取代理对象的这行代码:
ITestBean proxied = (ITestBean) pf.getProxy();
ProxyFactory 的getProxy的实现如下:
public Object getProxy() { return createAopProxy().getProxy();}
getProxy()调用ProxyCreatorSupport的createAopProxy()用于创立AopProxy。
protected final synchronized AopProxy createAopProxy() { if (!this.active) { activate(); } return getAopProxyFactory().createAopProxy(this);}
createAopProxy()先通过getAopProxyFactory()获取AopProxyFactory。getAopProxyFactory()间接返回一个DefaultAopProxyFactory的对象,而后调用DefaultAopProxyFactory的createAopProxy()办法创立具体的AopProxy,并传入this指针,即ProxyFactory对象自身,因为ProxyFactory继承了AdvisedSupport。
public AopProxy createAopProxy(AdvisedSupport config) throws AopConfigException { if (!NativeDetector.inNativeImage() && (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); } else { return new JdkDynamicAopProxy(config); }}private boolean hasNoUserSuppliedProxyInterfaces(AdvisedSupport config) { Class<?>[] ifcs = config.getProxiedInterfaces(); return (ifcs.length == 0 || (ifcs.length == 1 && SpringProxy.class.isAssignableFrom(ifcs[0])));}
- config.isOptimize():示意是否应用了优化策略,配置的属性optimize值决定;
- config.isProxyTargetClass():示意是否是代理指标类,配置的属性proxy-target-class值决定;
- hasNoUserSuppliedProxyInterfaces():就是在判断代理的对象是否有实现接口
当代理的是接口时,则应用JdkDynamicAopProxy,否则应用ObjenesisCglibAopProxy()。
JdkDynamicAopProxy保留了config和须要代理的接口。
public JdkDynamicAopProxy(AdvisedSupport config) throws AopConfigException { Assert.notNull(config, "AdvisedSupport must not be null"); if (config.getAdvisorCount() == 0 && config.getTargetSource() == AdvisedSupport.EMPTY_TARGET_SOURCE) { throw new AopConfigException("No advisors and no TargetSource specified"); } this.advised = config; this.proxiedInterfaces = AopProxyUtils.completeProxiedInterfaces(this.advised, true); findDefinedEqualsAndHashCodeMethods(this.proxiedInterfaces);}
当advised没有实现SpringProxy,Advised, DecoratingProxy 接口AopProxyUtils.completeProxiedInterfaces()会别离增加这三个接口。
到这里AopProxyFactory就实例化实现了。持续看getProxy()做了什么。
public Object getProxy() { return getProxy(ClassUtils.getDefaultClassLoader());}public Object getProxy(@Nullable ClassLoader classLoader) { if (logger.isTraceEnabled()) { logger.trace("Creating JDK dynamic proxy: " + this.advised.getTargetSource()); } return Proxy.newProxyInstance(classLoader, this.proxiedInterfaces, this);}
通过将classLoader, proxiedInterfaces和this传入到newProxyInstance中去创立了指标对象的代理对象。JdkDynamicAopProxy实现了InvocationHandler接口,因而能够将this指针传进去创立代理对象。
代理对象创立实现之后,当咱们调用代理对象的办法时,就会回调JdkDynamicAopProxy的invoke()办法。到这里咱们只看见了代理对象的创立,仍旧没有看到怎么对办法进行加强的逻辑,因为对代码进行加强的实现就在invoke()办法外面。
接下来看一下invoke()办法。
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { Object oldProxy = null; boolean setProxyContext = false; TargetSource targetSource = this.advised.targetSource; Object target = null; try { if (!this.equalsDefined && AopUtils.isEqualsMethod(method)) { // The target does not implement the equals(Object) method itself. return equals(args[0]); } else if (!this.hashCodeDefined && AopUtils.isHashCodeMethod(method)) { // The target does not implement the hashCode() method itself. return hashCode(); } else if (method.getDeclaringClass() == DecoratingProxy.class) { // There is only getDecoratedClass() declared -> dispatch to proxy config. return AopProxyUtils.ultimateTargetClass(this.advised); } else if (!this.advised.opaque && method.getDeclaringClass().isInterface() && method.getDeclaringClass().isAssignableFrom(Advised.class)) { // Service invocations on ProxyConfig with the proxy config... return AopUtils.invokeJoinpointUsingReflection(this.advised, method, args); } Object retVal; if (this.advised.exposeProxy) { // Make invocation available if necessary. oldProxy = AopContext.setCurrentProxy(proxy); setProxyContext = true; } // Get as late as possible to minimize the time we "own" the target, // in case it comes from a pool. target = targetSource.getTarget(); Class<?> targetClass = (target != null ? target.getClass() : null); // Get the interception chain for this method. List<Object> chain = this.advised.getInterceptorsAndDynamicInterceptionAdvice(method, targetClass); // Check whether we have any advice. If we don't, we can fallback on direct // reflective invocation of the target, and avoid creating a MethodInvocation. if (chain.isEmpty()) { // We can skip creating a MethodInvocation: just invoke the target directly // Note that the final invoker must be an InvokerInterceptor so we know it does // nothing but a reflective operation on the target, and no hot swapping or fancy proxying. Object[] argsToUse = AopProxyUtils.adaptArgumentsIfNecessary(method, args); retVal = AopUtils.invokeJoinpointUsingReflection(target, method, argsToUse); } else { // We need to create a method invocation... MethodInvocation invocation = new ReflectiveMethodInvocation(proxy, target, method, args, targetClass, chain); // Proceed to the joinpoint through the interceptor chain. retVal = invocation.proceed(); } // Massage return value if necessary. Class<?> returnType = method.getReturnType(); if (retVal != null && retVal == target && returnType != Object.class && returnType.isInstance(proxy) && !RawTargetAccess.class.isAssignableFrom(method.getDeclaringClass())) { // Special case: it returned "this" and the return type of the method // is type-compatible. Note that we can't help if the target sets // a reference to itself in another returned object. retVal = proxy; } else if (retVal == null && returnType != Void.TYPE && returnType.isPrimitive()) { throw new AopInvocationException( "Null return value from advice does not match primitive return type for: " + method); } return retVal; } finally { if (target != null && !targetSource.isStatic()) { // Must have come from TargetSource. targetSource.releaseTarget(target); } if (setProxyContext) { // Restore old proxy. AopContext.setCurrentProxy(oldProxy); } }}
invoke()的入参为代理对象,调用的办法,以及调用办法的参数。invoke()方首先查看method是不是equal,hashCode办法,以及declaringClass是不是DecoratingProxy,是不是须要将proxy设置到AopContext外面。做完这一系列的查看之后,通过getInterceptorsAndDynamicInterceptionAdvice()获取Interceptor和Advice保留到chain中,如果chain为空,示意没有interceptor和Advice,则间接通过反射的办法调用指标办法,invokeJoinpointUsingReflection()办法封装反射调用的逻辑。如果非空,则结构一个ReflectiveMethodInvocation对象,ReflectiveMethodInvocation对象的proceed办法封装了Advice办法的加强逻辑。
先来看一下getInterceptorsAndDynamicInterceptionAdvice()的实现:
public List<Object> getInterceptorsAndDynamicInterceptionAdvice(Method method, @Nullable Class<?> targetClass) { MethodCacheKey cacheKey = new MethodCacheKey(method); List<Object> cached = this.methodCache.get(cacheKey); if (cached == null) { cached = this.advisorChainFactory.getInterceptorsAndDynamicInterceptionAdvice( this, method, targetClass); this.methodCache.put(cacheKey, cached); } return cached;}
先将method封装成MethodCacheKey,而后尝试从缓存中获取这个key对应的缓存,如果没有,则通过advisorChainFactory.getInterceptorsAndDynamicInterceptionAdvice()去获取,这里的advisorChainFactory的默认实现是DefaultAdvisorChainFactory,看一下getInterceptorsAndDynamicInterceptionAdvice()的实现。
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;}
上述的代码首先通过GlobalAdvisorAdapterRegistry.getInstance()获取了DefaultAdvisorAdapterRegistry的实例,DefaultAdvisorAdapterRegistry注册了三种Adviced的适配器,用于将Advice适配成Interceptor。
public DefaultAdvisorAdapterRegistry() { registerAdvisorAdapter(new MethodBeforeAdviceAdapter()); registerAdvisorAdapter(new AfterReturningAdviceAdapter()); registerAdvisorAdapter(new ThrowsAdviceAdapter());}
而后对咱们增加的Advisor一一遍历,首先判断是不是PointcutAdvisor,而后判断是不是IntroductionAdvisor,如果都不是则认为是Interceptor。如果以后的advisor是PointcutAdvisor,则先判断是不是提前过滤过了,或者class是否合乎ClassFilter中定义的规定,如果进一步判断MethodMatcher的类型以及method是否匹配。无论是PointcutAdvisor,IntroductionAdvisor还是Interceptor, 最初都通过 registry.getInterceptors()办法对advisor进行适配,将advisor对象通过响应的适配器适配成MethodInterceptor的一个实例。具体的实现如下所示:
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]);}
看一下其中一个adapter的实现。
class MethodBeforeAdviceAdapter implements AdvisorAdapter, Serializable { @Override public boolean supportsAdvice(Advice advice) { return (advice instanceof MethodBeforeAdvice); } @Override public MethodInterceptor getInterceptor(Advisor advisor) { MethodBeforeAdvice advice = (MethodBeforeAdvice) advisor.getAdvice(); return new MethodBeforeAdviceInterceptor(advice); }}public class MethodBeforeAdviceInterceptor implements MethodInterceptor, BeforeAdvice, Serializable { private final MethodBeforeAdvice advice; public MethodBeforeAdviceInterceptor(MethodBeforeAdvice advice) { Assert.notNull(advice, "Advice must not be null"); this.advice = advice; } @Override @Nullable public Object invoke(MethodInvocation mi) throws Throwable { this.advice.before(mi.getMethod(), mi.getArguments(), mi.getThis()); return mi.proceed(); }}
能够看到对于BeforeAdvice最终被是配成了MethodBeforeAdviceInterceptor,实现了MethodInterceptor接口,其中invoke办法就是前面拦截器链的入口。
持续看proceed的实现。
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); }}
从索引为-1开始递增,如果所有的Interceptor或者Advice都调用结束,则通过反射调用指标函数。如果以后的interceptorOrInterceptionAdvice是InterceptorAndDynamicMethodMatcher的实例,则先通matches办法进行匹配,如果匹配胜利,则调用interceptor的invoke办法,否则跳过,如果不是InterceptorAndDynamicMethodMatcher的实例则时示意是一个interceptor,也间接调用invoke办法。
联合上述的MethodInterceptor的invoke办法,能够看到所有的Advice和interceptor串成了一条拦截器链,从头开始,通过matches办法进行匹配,匹配胜利则进行加强,否则持续往下查找,直到尾部,调用指标办法,整个过程就是对指标办法的加强过程,也是AOP的实现原理。
总结
本文以ProxyFactory为例剖析了Spring AOP的实现,其实现原理大抵能够分为三个局部:
- Advice, Pointcut,Advisor的实现
- 指标对象代理对象的生成。
- 对Advice进行适配,并组装成一条拦截器链,通过拦截器链对指标办法进行加强。