1.设计原理
通过JDK的Proxy方式或者CGLIB方式生成代理对象的时候，相关的拦截器已经配置到代理对象中去了；
通过拦截器回调
JDK动态代理：代理类和目标类实现了共同的接口，用到InvocationHandler接口。(见下面代码)
CGLIB动态代理：代理类是目标类的子类，用到MethodInterceptor接口。(见下面代码)
jdk动态代理是由Java内部的反射机制来实现的；
cglib动态代理底层则是借助asm来实现的。
jdk （Proxy）
使用了Proxy类的
newProxyInstance()方法来创建代理对象
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final UserService target=new UserServiceImpl();Class<UserService> clazz = UserService.class;ClassLoader loader = clazz.getClassLoader();Object proxyInstance = Proxy.newProxyInstance(loader, new Class[]{clazz}, new InvocationHandler() { @Override public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { System.out.println("Before..."); Object result = method.invoke(target, args); System.out.println("After..."); return result; }});UserService service = (UserService) proxyInstance;service.getUserInfo(); |
cglib
动态类对象
Enhancer，它是CGLIB的核心类；Enhancer类的setSuperclass()方法来确定目标对象；setCallback()方法添加回调函数。最后通过return 语句将创建的代理类对象返回。intercept()方法会在程序执行目标方法时被调用，方法运行时会执行切面类中的增强方法（前和后）。
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Enhancer enhancer=new Enhancer();enhancer.setSuperclass(UserInfo.class);enhancer.setCallbacks(new Callback[]{new MethodInterceptor() { @Override public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable { System.out.println("Before..."); Object result = methodProxy.invokeSuper(o, objects); System.out.println("After..."); return result; }}});UserInfo userInfo = (UserInfo) enhancer.create();userInfo.test(); |
2.ProxyFactory (Spring-Core)
ProxyFactory在生成代理对象之前需要决定到底是使用JDK动态代理还是CGLIB技术；
getProxy()返回CglibAopProxy或者JdkDynamicAopProxy
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UserService target=new UserServiceImpl(); ProxyFactory proxyFactory=new ProxyFactory(); proxyFactory.setTarget(target); //addAdvice() 添加多个，自动形成责任链 proxyFactory.addAdvice(new AopMethodAroundAdvice()); proxyFactory.addAdvice(new AopMethodBeforeAdvice()); proxyFactory.addAdvice(new AopMethodAfterAdvice()); proxyFactory.addAdvice(new AopMethodThrowsAdvice()); //Advisor 设置具体 pointCut和 advice// proxyFactory.addAdvisor(new AopPointcutAdvisor()); UserService userService = (UserService) proxyFactory.getProxy(); userService.getUserInfo(); userService.test(); |
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public Object getProxy() { return createAopProxy().getProxy(); } |
2.1 JdkDynamicAopProxy
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final class JdkDynamicAopProxy implements AopProxy, InvocationHandler, Serializable { @Override public Object getProxy() { return getProxy(ClassUtils.getDefaultClassLoader()); } @Override 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); } @Override @Nullable public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { ...省略... 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); //重点：获取此方法的拦截链 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); } } } |
2.2 CglibAopProxy
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class CglibAopProxy implements AopProxy, Serializable { @Override public Object getProxy() { return getProxy(null); } @Override public Object getProxy(@Nullable ClassLoader classLoader) { if (logger.isTraceEnabled()) { logger.trace("Creating CGLIB proxy: " + this.advised.getTargetSource()); } try { Class<?> rootClass = this.advised.getTargetClass(); Assert.state(rootClass != null, "Target class must be available for creating a CGLIB proxy"); Class<?> proxySuperClass = rootClass; if (rootClass.getName().contains(ClassUtils.CGLIB_CLASS_SEPARATOR)) { proxySuperClass = rootClass.getSuperclass(); Class<?>[] additionalInterfaces = rootClass.getInterfaces(); for (Class<?> additionalInterface : additionalInterfaces) { this.advised.addInterface(additionalInterface); } } // Validate the class, writing log messages as necessary. validateClassIfNecessary(proxySuperClass, classLoader); // Configure CGLIB Enhancer... Enhancer enhancer = createEnhancer(); if (classLoader != null) { enhancer.setClassLoader(classLoader); if (classLoader instanceof SmartClassLoader && ((SmartClassLoader) classLoader).isClassReloadable(proxySuperClass)) { enhancer.setUseCache(false); } } enhancer.setSuperclass(proxySuperClass); enhancer.setInterfaces(AopProxyUtils.completeProxiedInterfaces(this.advised)); enhancer.setNamingPolicy(SpringNamingPolicy.INSTANCE); enhancer.setStrategy(new ClassLoaderAwareGeneratorStrategy(classLoader)); //重点：设置Callbacks[] Callback[] callbacks = getCallbacks(rootClass); Class<?>[] types = new Class<?>[callbacks.length]; for (int x = 0; x < types.length; x++) { types[x] = callbacks[x].getClass(); } // fixedInterceptorMap only populated at this point, after getCallbacks call above enhancer.setCallbackFilter(new ProxyCallbackFilter( this.advised.getConfigurationOnlyCopy(), this.fixedInterceptorMap, this.fixedInterceptorOffset)); enhancer.setCallbackTypes(types); // Generate the proxy class and create a proxy instance. return createProxyClassAndInstance(enhancer, callbacks); } catch (CodeGenerationException | IllegalArgumentException ex) { throw new AopConfigException("Could not generate CGLIB subclass of " + this.advised.getTargetClass() + ": Common causes of this problem include using a final class or a non-visible class", ex); } catch (Throwable ex) { // TargetSource.getTarget() failed throw new AopConfigException("Unexpected AOP exception", ex); } } //获取Callbacks[] private Callback[] getCallbacks(Class<?> rootClass) throws Exception { // Parameters used for optimization choices... boolean exposeProxy = this.advised.isExposeProxy(); boolean isFrozen = this.advised.isFrozen(); boolean isStatic = this.advised.getTargetSource().isStatic(); // Choose an "aop" interceptor (used for AOP calls). (重要类) Callback aopInterceptor = new DynamicAdvisedInterceptor(this.advised); // Choose a "straight to target" interceptor. (used for calls that are // unadvised but can return this). May be required to expose the proxy. Callback targetInterceptor; if (exposeProxy) { targetInterceptor = (isStatic ? new StaticUnadvisedExposedInterceptor(this.advised.getTargetSource().getTarget()) : new DynamicUnadvisedExposedInterceptor(this.advised.getTargetSource())); } else { targetInterceptor = (isStatic ? new StaticUnadvisedInterceptor(this.advised.getTargetSource().getTarget()) : new DynamicUnadvisedInterceptor(this.advised.getTargetSource())); } // Choose a "direct to target" dispatcher (used for // unadvised calls to static targets that cannot return this). Callback targetDispatcher = (isStatic ? new StaticDispatcher(this.advised.getTargetSource().getTarget()) : new SerializableNoOp()); Callback[] mainCallbacks = new Callback[] { aopInterceptor, // for normal advice targetInterceptor, // invoke target without considering advice, if optimized new SerializableNoOp(), // no override for methods mapped to this targetDispatcher, this.advisedDispatcher, new EqualsInterceptor(this.advised), new HashCodeInterceptor(this.advised) }; Callback[] callbacks; ...省略... return callbacks; } |
DynamicAdvisedInterceptor
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private static class DynamicAdvisedInterceptor implements MethodInterceptor, Serializable { private final AdvisedSupport advised; public DynamicAdvisedInterceptor(AdvisedSupport advised) { this.advised = advised; } @Override @Nullable public Object intercept(Object proxy, Method method, Object[] args, MethodProxy methodProxy) throws Throwable { Object oldProxy = null; boolean setProxyContext = false; Object target = null; TargetSource targetSource = this.advised.getTargetSource(); try { 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); //重点：获取此方法的拦截链 List<Object> chain = this.advised.getInterceptorsAndDynamicInterceptionAdvice(method, targetClass); Object retVal; // Check whether we only have one InvokerInterceptor: that is, // no real advice, but just reflective invocation of the target. if (chain.isEmpty() && Modifier.isPublic(method.getModifiers())) { // 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 = methodProxy.invoke(target, argsToUse); } else { // We need to create a method invocation... retVal = new CglibMethodInvocation(proxy, target, method, args, targetClass, chain, methodProxy).proceed(); } retVal = processReturnType(proxy, target, method, retVal); return retVal; } finally { if (target != null && !targetSource.isStatic()) { targetSource.releaseTarget(target); } if (setProxyContext) { // Restore old proxy. AopContext.setCurrentProxy(oldProxy); } } }} |
2.3 主要源码部分
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public class AdvisedSupport extends ProxyConfig implements Advised { 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; } |
DefaultAdvisorChainFactory
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public class DefaultAdvisorChainFactory implements AdvisorChainFactory, Serializable { @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) { //重点：将advisor中的advice转换为MethodInterceptor。 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; } |
DefaultAdvisorAdapterRegistry
构造方法注册了
MethodBeforeAdviceAdapter、AfterReturningAdviceAdapter、ThrowsAdviceAdapter3个Adapter模板
通过getInterceptors(Advisor advisor) 方法，将 Advisor 总的advice 转换成 MethodInterceptor
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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()); }...省略... @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); }} |
1.
AfterReturningAdviceAdapter通过getInterceptor方法 获取AfterReturningAdviceInterceptor过滤器
2.AfterReturningAdviceInterceptorinvoke()方法 先执行目标方法，后执行（后置）advice了方法
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class AfterReturningAdviceAdapter implements AdvisorAdapter, Serializable { @Override public boolean supportsAdvice(Advice advice) { return (advice instanceof AfterReturningAdvice); } @Override public MethodInterceptor getInterceptor(Advisor advisor) { AfterReturningAdvice advice = (AfterReturningAdvice) advisor.getAdvice(); return new AfterReturningAdviceInterceptor(advice); }}public class AfterReturningAdviceInterceptor implements MethodInterceptor, AfterAdvice, Serializable { private final AfterReturningAdvice advice; /** * Create a new AfterReturningAdviceInterceptor for the given advice. * @param advice the AfterReturningAdvice to wrap */ public AfterReturningAdviceInterceptor(AfterReturningAdvice advice) { Assert.notNull(advice, "Advice must not be null"); this.advice = advice; } @Override @Nullable public Object invoke(MethodInvocation mi) throws Throwable { Object retVal = mi.proceed(); this.advice.afterReturning(retVal, mi.getMethod(), mi.getArguments(), mi.getThis()); return retVal; }} |
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原文链接：https://blog.csdn.net/qq_18398239/article/details/120822558
