SpringAOP 多切面

本贴最后更新于 1294 天前,其中的信息可能已经时移世异

多切面执行时,采用了责任链设计模式。

切面的配置顺序决定了切面的执行顺序,多个切面执行的过程,类似于方法调用的过程,在环绕通知的 proceed()执行时,去执行下一个切面或如果没有下一个切面执行目标方法,从而达成了如下的执行过程:(目标方法只会执行一次)

执行的顺序和配置顺序等有关
目标方法执行前: 前置,环绕前(顺序可以变)
目标方法执行后: 最终,环绕后,最终(顺序可以变)

责任链设计模式:为解除请求的发送者和接收者之间的耦合,而使多个对象都有机会处理这个请求。将这些对象连成一条链,并沿着这条链传递该请求,直到有对象处理它

因为责任链设计模式 first 切面中调用 poceed 方法后,继续沿着责任链去调用 second 切面中的环绕前-----然后掉 poceed 方法 ----此时没有切面了---沿着责任链去调用 addUser()方法---调用结束 addUser(),在执行环绕 second 环绕后。。。。。

如果目标方法抛出异常

通知间的跳转顺序

多个切入点责任链模式如下图

Aspect1 和 Aspect2 两个切面类中所有通知类型的执行顺序,Method 是具体的切入点,order 代表优先级,它根据一个 int 值来判断优先级的高低,数字越小,优先级越高!所以,不同的切面,实际上是环绕于切入点的同心圆

jdk 代理的源码为(这里采用默认的 jdk 代理模式获取代理,cglib 原理类似):

/* * Copyright 2002-2018 the original author or authors. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.springframework.aop.framework; import java.io.Serializable; import java.lang.reflect.InvocationHandler; import java.lang.reflect.Method; import java.lang.reflect.Proxy; import java.util.List; import org.aopalliance.intercept.MethodInvocation; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.springframework.aop.AopInvocationException; import org.springframework.aop.RawTargetAccess; import org.springframework.aop.TargetSource; import org.springframework.aop.support.AopUtils; import org.springframework.core.DecoratingProxy; import org.springframework.lang.Nullable; import org.springframework.util.Assert; import org.springframework.util.ClassUtils; /** * JDK-based {@link AopProxy} implementation for the Spring AOP framework, * based on JDK {@link java.lang.reflect.Proxy dynamic proxies}. * * <p>Creates a dynamic proxy, implementing the interfaces exposed by * the AopProxy. Dynamic proxies <i>cannot</i> be used to proxy methods * defined in classes, rather than interfaces. * * <p>Objects of this type should be obtained through proxy factories, * configured by an {@link AdvisedSupport} class. This class is internal * to Spring's AOP framework and need not be used directly by client code. * * <p>Proxies created using this class will be thread-safe if the * underlying (target) class is thread-safe. * * <p>Proxies are serializable so long as all Advisors (including Advices * and Pointcuts) and the TargetSource are serializable. * * @author Rod Johnson * @author Juergen Hoeller * @author Rob Harrop * @author Dave Syer * @see java.lang.reflect.Proxy * @see AdvisedSupport * @see ProxyFactory */ final class JdkDynamicAopProxy implements AopProxy, InvocationHandler, Serializable { /** use serialVersionUID from Spring 1.2 for interoperability. */ private static final long serialVersionUID = 5531744639992436476L; /* * NOTE: We could avoid the code duplication between this class and the CGLIB * proxies by refactoring "invoke" into a template method. However, this approach * adds at least 10% performance overhead versus a copy-paste solution, so we sacrifice * elegance for performance. (We have a good test suite to ensure that the different * proxies behave the same :-) * This way, we can also more easily take advantage of minor optimizations in each class. */ /** We use a static Log to avoid serialization issues. */ private static final Log logger = LogFactory.getLog(JdkDynamicAopProxy.class); /** Config used to configure this proxy. */ private final AdvisedSupport advised; /** * Is the {@link #equals} method defined on the proxied interfaces? */ private boolean equalsDefined; /** * Is the {@link #hashCode} method defined on the proxied interfaces? */ private boolean hashCodeDefined; /** * Construct a new JdkDynamicAopProxy for the given AOP configuration. * @param config the AOP configuration as AdvisedSupport object * @throws AopConfigException if the config is invalid. We try to throw an informative * exception in this case, rather than let a mysterious failure happen later. */ public JdkDynamicAopProxy(AdvisedSupport config) throws AopConfigException { Assert.notNull(config, "AdvisedSupport must not be null"); if (config.getAdvisors().length == 0 && config.getTargetSource() == AdvisedSupport.EMPTY_TARGET_SOURCE) { throw new AopConfigException("No advisors and no TargetSource specified"); } this.advised = config; } @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()); } Class<?>[] proxiedInterfaces = AopProxyUtils.completeProxiedInterfaces(this.advised, true); findDefinedEqualsAndHashCodeMethods(proxiedInterfaces); return Proxy.newProxyInstance(classLoader, proxiedInterfaces, this); } /** * Finds any {@link #equals} or {@link #hashCode} method that may be defined * on the supplied set of interfaces. * @param proxiedInterfaces the interfaces to introspect */ private void findDefinedEqualsAndHashCodeMethods(Class<?>[] proxiedInterfaces) { for (Class<?> proxiedInterface : proxiedInterfaces) { Method[] methods = proxiedInterface.getDeclaredMethods(); for (Method method : methods) { if (AopUtils.isEqualsMethod(method)) { this.equalsDefined = true; } if (AopUtils.isHashCodeMethod(method)) { this.hashCodeDefined = true; } if (this.equalsDefined && this.hashCodeDefined) { return; } } } } /** * Implementation of {@code InvocationHandler.invoke}. * <p>Callers will see exactly the exception thrown by the target, * unless a hook method throws an exception. */ @Override @Nullable public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { MethodInvocation invocation; 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... 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); } } } /** * Equality means interfaces, advisors and TargetSource are equal. * <p>The compared object may be a JdkDynamicAopProxy instance itself * or a dynamic proxy wrapping a JdkDynamicAopProxy instance. */ @Override public boolean equals(@Nullable Object other) { if (other == this) { return true; } if (other == null) { return false; } JdkDynamicAopProxy otherProxy; if (other instanceof JdkDynamicAopProxy) { otherProxy = (JdkDynamicAopProxy) other; } else if (Proxy.isProxyClass(other.getClass())) { InvocationHandler ih = Proxy.getInvocationHandler(other); if (!(ih instanceof JdkDynamicAopProxy)) { return false; } otherProxy = (JdkDynamicAopProxy) ih; } else { // Not a valid comparison... return false; } // If we get here, otherProxy is the other AopProxy. return AopProxyUtils.equalsInProxy(this.advised, otherProxy.advised); } /** * Proxy uses the hash code of the TargetSource. */ @Override public int hashCode() { return JdkDynamicAopProxy.class.hashCode() * 13 + this.advised.getTargetSource().hashCode(); } }

先看获取代理的方法

@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()); } Class<?>[] proxiedInterfaces = AopProxyUtils.completeProxiedInterfaces(this.advised, true); findDefinedEqualsAndHashCodeMethods(proxiedInterfaces); return Proxy.newProxyInstance(classLoader, proxiedInterfaces, this); }

最终调用了 jdk 生成代理的方法,并且该类实现类 InvocationHandler 接口,那么继续看 invoke 方法

/** * Implementation of {@code InvocationHandler.invoke}. * <p>Callers will see exactly the exception thrown by the target, * unless a hook method throws an exception. */ @Override @Nullable public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { MethodInvocation invocation; 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... 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); } } }

忽略了几种特殊情况,然后判断是否报漏代理,即业务代码能不能通过

AopContext.currentProxy()
方法获得,之后真正的进行多个切面的执行

1.先获取拦截器链 2.遍历该拦截器链 3.通过 ReflectiveMethodInvocation 方法的 proceed()方法执行

获取拦截器链,应该是加载的时候每个方法对应的一个缓存

/** * Determine a list of {@link org.aopalliance.intercept.MethodInterceptor} objects * for the given method, based on this configuration. * @param method the proxied method * @param targetClass the target class * @return a List of MethodInterceptors (may also include InterceptorAndDynamicMethodMatchers) */ 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; }

ReflectiveMethodInvocation 的 procceed()执行逻辑

@Override @Nullable 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); } }

可以看出该方法是一个递归,默认 currentInterceptorIndex 为 0,如果不是链最后一个则执行,之后通过递归实现链中下一个拦截器执行,如果是最后一个则执行实际被代理的方法,这样递归实现,能有效的解决环绕通知中前后的执行顺序的正确性

版权声明:本文为博主原创文章,遵循 CC 4.0 BY-SA 版权协议,转载请附上原文出处链接和本声明。

本文链接:https://blog.csdn.net/qq_32224047/article/details/107146328
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