匪夷所思，spring aop這么寫竟然會失效??！

背景

  • spring 版本：3.2.8.RELEASE
  • JDK版本：1.8

  • 本地是正常，線上環(huán)境是有問題的
    應(yīng)用從云下遷移到云上的過程中出現(xiàn)了一個應(yīng)用部分aop 通知失效的問題，場景如下：


    image.png
  • node1 節(jié)點上的category 是失效的，element是正常的

  • node2 節(jié)點上aop都是正常
    從上面我們判斷是節(jié)點導(dǎo)致的，然后我們給節(jié)點添加親和性標簽；所有的pod都部署到這個節(jié)點上，pod全部部署到這個節(jié)點上后spring aop竟然都正常了。
    難道是節(jié)點的問題？
    spring 是Java層面的東西，中間還隔了一層JVM用來屏蔽不同操作系統(tǒng)的影響；我判斷肯定是應(yīng)用代碼中有什么配置影響了spring aop，畢竟是07年的老項目了。


    image.png

我們首先分析一下 spring aop的流程。

spring aop流程

spring xml配置

下面是spring aop的配置，依賴于org.springframework.aop.framework.autoproxy.BeanNameAutoProxyCreator對象來生產(chǎn)代理對象。

 
    <bean id="myAfterAdvisor" class="com.xbin.aop.MyAfterAdvisor" lazy-init="false" >
        <property name="category" ref="category"></property>
    </bean>



    <bean id="nameMatchMethodPointcutAdvisor" class="org.springframework.aop.support.NameMatchMethodPointcutAdvisor" >
        <property name="mappedNames">
            <list>
                <value>test</value>
                <value>insert</value>
                <value>update</value>
            </list>
        </property>

        <property name="order" value="99"></property>

        <property name="advice">
            <ref bean="myAfterAdvisor"></ref>
<!--            <ref ="myAfterAdvisor"></ref>-->
        </property>
    </bean>


    <bean id="beanNameAutoProxyCreator"
          class="org.springframework.aop.framework.autoproxy.BeanNameAutoProxyCreator">
        <property name="interceptorNames">
            <list>
                <value>nameMatchMethodPointcutAdvisor</value>

            </list>
        </property>
        <property name="order" value="99"></property>
        <property name="beanNames">
            <list>
                <value>element</value>
                <value>category</value>
            </list>
        </property>
    </bean>

spring 代理對象創(chuàng)建的流程

image.png

我們了解到spring aop功能的實現(xiàn)依賴于代理對象的創(chuàng)建，代理類實現(xiàn)了接口所以使用的是JDK的動態(tài)代理。
對應(yīng)JDK的動態(tài)代理來說最重要的是InvocationHandler接口。


image.png
  1. 創(chuàng)建代理對象
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);
    }
  1. InvocationHandler的實現(xiàn)

public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        MethodInvocation invocation;
        Object oldProxy = null;
        boolean setProxyContext = false;

        TargetSource targetSource = this.advised.targetSource;
        Class targetClass = null;
        Object target = null;

        try {
            if (!this.equalsDefined && AopUtils.isEqualsMethod(method)) {
                // The target does not implement the equals(Object) method itself.
                return equals(args[0]);
            }
            if (!this.hashCodeDefined && AopUtils.isHashCodeMethod(method)) {
                // The target does not implement the hashCode() method itself.
                return hashCode();
            }
            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;
            }

            // May be null. Get as late as possible to minimize the time we "own" the target,
            // in case it comes from a pool.
            target = targetSource.getTarget();
            if (target != null) {
                targetClass = target.getClass();
            }

            // 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.
                retVal = AopUtils.invokeJoinpointUsingReflection(target, method, args);
            }
            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.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);
            }
        }
    }

大體流程如上，至于 spring aop 中前置通知、后置通知、環(huán)繞通知等是如果調(diào)用的這邊就不進行分析了；我們回歸解決問題的本質(zhì)上。

問題分析

代理對象是否生成

我們都知道spring aop的能力都是通過代理對象來實現(xiàn)了，我們直接輸出日志查看對象信息。發(fā)現(xiàn)類名有Proxy說明是生成是由JDK的動態(tài)代理生成的對象。

代理對象中通知是否可以獲取到

代理對象已經(jīng)生成，接下來看看調(diào)用代理對象時候相關(guān)的通知是否可以獲取到。


image.png

JdkDynamicAopProxy的invoke方法里面需要獲取到通知處理的 chain。
線上環(huán)境這里我們借助阿里的arthas線上調(diào)試工具進行排查。
arthas地址：https://arthas.aliyun.com/doc/
我們來監(jiān)控：org.springframework.aop.framework.AdvisedSupport#getInterceptorsAndDynamicInterceptionAdvice 這個方法。

watch org.springframework.aop.framework.JdkDynamicAopProxy invoke -x 2

  • 正常的bean


    image.png

  • 異常的bean


    image.png

通過上述分析可以發(fā)現(xiàn)異常bean沒有獲取通知相關(guān)的攔截器。

源碼分析

getInterceptorsAndDynamicInterceptionAdvice

    public List<Object> getInterceptorsAndDynamicInterceptionAdvice(Method method, 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;
    }

getInterceptorsAndDynamicInterceptionAdvice


public List<Object> 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<Object> interceptorList = new ArrayList<Object>(config.getAdvisors().length);
        boolean hasIntroductions = hasMatchingIntroductions(config, targetClass);
        AdvisorAdapterRegistry registry = GlobalAdvisorAdapterRegistry.getInstance();
        // 如果config.getAdvisors獲取的對象是空的，那么獲取的 list也是空的
        for (Advisor advisor : config.getAdvisors()) {
            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 (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(targetClass)) {
                    Interceptor[] interceptors = registry.getInterceptors(advisor);
                    interceptorList.addAll(Arrays.asList(interceptors));
                }
            }
            else {
                Interceptor[] interceptors = registry.getInterceptors(advisor);
                interceptorList.addAll(Arrays.asList(interceptors));
            }
        }
        return interceptorList;
    }
image.png
image.png

結(jié)合上面2中圖，可以分析得出 advisorArray中的內(nèi)容是空的，那么接下來我們需要分析這個數(shù)組為啥是空。

這個對象是在spring aop 生成代理對象的時候進行賦值的。

org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator#postProcessAfterInitialization

    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        if (bean != null) {
            Object cacheKey = getCacheKey(bean.getClass(), beanName);
            if (!this.earlyProxyReferences.containsKey(cacheKey)) {
                return wrapIfNecessary(bean, beanName, cacheKey);
            }
        }
        return bean;
    }

org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator#wrapIfNecessary

    protected Object wrapIfNecessary(Object bean, String beanName, Object cacheKey) {
        if (beanName != null && this.targetSourcedBeans.containsKey(beanName)) {
            return bean;
        }
        if (Boolean.FALSE.equals(this.advisedBeans.get(cacheKey))) {
            return bean;
        }
        if (isInfrastructureClass(bean.getClass()) || shouldSkip(bean.getClass(), beanName)) {
            this.advisedBeans.put(cacheKey, Boolean.FALSE);
            return bean;
        }

        // Create proxy if we have advice.
        Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(bean.getClass(), beanName, null);
        if (specificInterceptors != DO_NOT_PROXY) {
            this.advisedBeans.put(cacheKey, Boolean.TRUE);
            Object proxy = createProxy(bean.getClass(), beanName, specificInterceptors, new SingletonTargetSource(bean));
            this.proxyTypes.put(cacheKey, proxy.getClass());
            return proxy;
        }

        this.advisedBeans.put(cacheKey, Boolean.FALSE);
        return bean;
    }

org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator#createProxy

protected Object createProxy(
            Class<?> beanClass, String beanName, Object[] specificInterceptors, TargetSource targetSource) {

        ProxyFactory proxyFactory = new ProxyFactory();
        // Copy our properties (proxyTargetClass etc) inherited from ProxyConfig.
        proxyFactory.copyFrom(this);

        if (!shouldProxyTargetClass(beanClass, beanName)) {
            // Must allow for introductions; can't just set interfaces to
            // the target's interfaces only.
            Class<?>[] targetInterfaces = ClassUtils.getAllInterfacesForClass(beanClass, this.proxyClassLoader);
            for (Class<?> targetInterface : targetInterfaces) {
                proxyFactory.addInterface(targetInterface);
            }
        }
       //  如果這里沒有獲取到 advisors ，那么advisorArray數(shù)組就是空的了
        Advisor[] advisors = buildAdvisors(beanName, specificInterceptors);
        for (Advisor advisor : advisors) {
            proxyFactory.addAdvisor(advisor);
        }

        proxyFactory.setTargetSource(targetSource);
        customizeProxyFactory(proxyFactory);

        proxyFactory.setFrozen(this.freezeProxy);
        if (advisorsPreFiltered()) {
            proxyFactory.setPreFiltered(true);
        }

        return proxyFactory.getProxy(this.proxyClassLoader);
    }

org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator#buildAdvisors

protected Advisor[] buildAdvisors(String beanName, Object[] specificInterceptors) {
        // Handle prototypes correctly...
         // resolveInterceptorNames 方法非常關(guān)鍵
        Advisor[] commonInterceptors = resolveInterceptorNames();

        List<Object> allInterceptors = new ArrayList<Object>();
        if (specificInterceptors != null) {
            allInterceptors.addAll(Arrays.asList(specificInterceptors));
            if (commonInterceptors != null) {
                if (this.applyCommonInterceptorsFirst) {
                    allInterceptors.addAll(0, Arrays.asList(commonInterceptors));
                }
                else {
                    allInterceptors.addAll(Arrays.asList(commonInterceptors));
                }
            }
        }
        if (logger.isDebugEnabled()) {
            int nrOfCommonInterceptors = (commonInterceptors != null ? commonInterceptors.length : 0);
            int nrOfSpecificInterceptors = (specificInterceptors != null ? specificInterceptors.length : 0);
            logger.debug("Creating implicit proxy for bean '" + beanName + "' with " + nrOfCommonInterceptors +
                    " common interceptors and " + nrOfSpecificInterceptors + " specific interceptors");
        }

        Advisor[] advisors = new Advisor[allInterceptors.size()];
        for (int i = 0; i < allInterceptors.size(); i++) {
            advisors[i] = this.advisorAdapterRegistry.wrap(allInterceptors.get(i));
        }
        return advisors;
    }

org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator#resolveInterceptorNames

    private Advisor[] resolveInterceptorNames() {
        ConfigurableBeanFactory cbf = (this.beanFactory instanceof ConfigurableBeanFactory) ?
                (ConfigurableBeanFactory) this.beanFactory : null;
        List<Advisor> advisors = new ArrayList<Advisor>();
        for (String beanName : this.interceptorNames) {
           // 這里有一個邏輯非常關(guān)鍵， interceptorName如果正在創(chuàng)建中是不會添加到 advisors里面的，
         //  spring認為這不是一個完整的對象，直接對外使用會出現(xiàn)問題。
            if (cbf == null || !cbf.isCurrentlyInCreation(beanName)) {
                Object next = this.beanFactory.getBean(beanName);
                advisors.add(this.advisorAdapterRegistry.wrap(next));
            }
        }
        return advisors.toArray(new Advisor[advisors.size()]);
    }

總結(jié)

原因總結(jié)

通過分析上述源碼，那么什么場景下會出現(xiàn)這種問題？


image.png
image.png

spring 沒有添加特殊配置的前提，存在上述依賴是會報

信息: Destroying singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@3796751b: defining beans [category,element,myAfterAdvisor,nameMatchMethodPointcutAdvisor,beanNameAutoProxyCreator]; root of factory hierarchy
Exception in thread "main" org.springframework.beans.factory.BeanCurrentlyInCreationException: Error creating bean with name 'category': Bean with name 'category' has been injected into other beans [myAfterAdvisor] in its raw version as part of a circular reference, but has eventually been wrapped. This means that said other beans do not use the final version of the bean. This is often the result of over-eager type matching - consider using 'getBeanNamesOfType' with the 'allowEagerInit' flag turned off, for example.
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:548)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:458)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:296)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:223)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:293)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:628)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:932)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:479)
    at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:139)
    at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:83)
    at com.xbin.TestAopMain.main(TestAopMain.java:15)

Process finished with exit code 1

需要添加 lazy-init來解決多個代理對象之間的循環(huán)依賴。


image.png

  • aop 生效場景下的輸出。


    image.png
  • aop 失效場景下的輸出：
image.png
image.png

就只改了myAfterAdvisor延遲初始化的就會導(dǎo)致 aop失效。

image.png

解決方案

  • 通過配置延遲初始化bean來打斷依賴創(chuàng)建對象。
  • 修改應(yīng)用代碼不應(yīng)該存在這種依賴關(guān)系。（推薦方案）
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