Spring AOP 处理流程

作者: 数齐 | 来源:发表于2018-05-29 20:47 被阅读125次

    我们今天来聊一下Spring的AOP,我们从AnnotationAwareAspectJAutoProxyCreator开始说起。他是一个InstantiationAwareBeanPostProcessor所以我们需要看一下他的生命周期方法postProcessBeforeInstantiationpostProcessAfterInitialization,这两个是有具体处理逻辑的。首先我们看一下postProcessBeforeInstantiation

    @Override
        public Object postProcessBeforeInstantiation(Class<?> beanClass, String beanName) throws BeansException {
            Object cacheKey = getCacheKey(beanClass, beanName);
    
            if (beanName == null || !this.targetSourcedBeans.contains(beanName)) {
                if (this.advisedBeans.containsKey(cacheKey)) {
                    return null;
                }
                if (isInfrastructureClass(beanClass) || shouldSkip(beanClass, beanName)) {
                    this.advisedBeans.put(cacheKey, Boolean.FALSE);
                    return null;
                }
            }
    
            // Create proxy here if we have a custom TargetSource.
            // Suppresses unnecessary default instantiation of the target bean:
            // The TargetSource will handle target instances in a custom fashion.
            if (beanName != null) {
                TargetSource targetSource = getCustomTargetSource(beanClass, beanName);
                if (targetSource != null) {
                    this.targetSourcedBeans.add(beanName);
                    Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(beanClass, beanName, targetSource);
                    Object proxy = createProxy(beanClass, beanName, specificInterceptors, targetSource);
                    this.proxyTypes.put(cacheKey, proxy.getClass());
                    return proxy;
                }
            }
    
            return null;
        }
    

    根据beanClassbeanName创建cacheKey.如果beanName为空,并且targetSourcedBeans里面不包含此beanName进入下面的流程,如果advisedBeans包含了这个cacheKey直接返回,另外就是判断他是否是一个基础设施类(isInfrastructureClass)和是否应该跳过(shouldSkip)。首先我们看下基础设施类的判断

    protected boolean isInfrastructureClass(Class<?> beanClass) {
            boolean retVal = Advice.class.isAssignableFrom(beanClass) ||
                    Advisor.class.isAssignableFrom(beanClass) ||
                    AopInfrastructureBean.class.isAssignableFrom(beanClass);
            if (retVal && logger.isTraceEnabled()) {
                logger.trace("Did not attempt to auto-proxy infrastructure class [" + beanClass.getName() + "]");
            }
            return retVal;
        }
    

    如果beanClass是AdviceAdvisorAopInfrastructureBean是他们的中的一种,那么就是基础设施类。我们再看下shouldSkip

    @Override
        protected boolean shouldSkip(Class<?> beanClass, String beanName) {
            // TODO: Consider optimization by caching the list of the aspect names
            List<Advisor> candidateAdvisors = findCandidateAdvisors(); //关注点1
            for (Advisor advisor : candidateAdvisors) {
                if (advisor instanceof AspectJPointcutAdvisor) {
                    if (((AbstractAspectJAdvice) advisor.getAdvice()).getAspectName().equals(beanName)) {
                        return true;
                    }
                }
            }
            return super.shouldSkip(beanClass, beanName);
        }
    

    里面有一个重要的方法,寻找候选的Advisors,这个方法的具体实现是org.springframework.aop.aspectj.annotation.AnnotationAwareAspectJAutoProxyCreator#findCandidateAdvisors

    @Override
        protected List<Advisor> findCandidateAdvisors() {
            // Add all the Spring advisors found according to superclass rules.
            List<Advisor> advisors = super.findCandidateAdvisors();
            // Build Advisors for all AspectJ aspects in the bean factory.
            advisors.addAll(this.aspectJAdvisorsBuilder.buildAspectJAdvisors());
            return advisors;
        }
    

    这个方法返回的数据分为两部分,第一部分是super.findCandidateAdvisors(),第二部分是this.aspectJAdvisorsBuilder.buildAspectJAdvisors()。我们一个个的说,第一部分是获取spring容器中的Advisor类型的Bean的实例。

    public List<Advisor> findAdvisorBeans() {
            // Determine list of advisor bean names, if not cached already.
            String[] advisorNames = null;
            synchronized (this) {
                advisorNames = this.cachedAdvisorBeanNames;
                if (advisorNames == null) {
                    // Do not initialize FactoryBeans here: We need to leave all regular beans
                    // uninitialized to let the auto-proxy creator apply to them!
                    advisorNames = BeanFactoryUtils.beanNamesForTypeIncludingAncestors(
                            this.beanFactory, Advisor.class, true, false);
                    this.cachedAdvisorBeanNames = advisorNames;
                }
            }
            if (advisorNames.length == 0) {
                return new LinkedList<Advisor>();
            }
    
            List<Advisor> advisors = new LinkedList<Advisor>();
            for (String name : advisorNames) {
                if (isEligibleBean(name)) {
                    if (this.beanFactory.isCurrentlyInCreation(name)) {
                        if (logger.isDebugEnabled()) {
                            logger.debug("Skipping currently created advisor '" + name + "'");
                        }
                    }
                    else {
                        try {
                            advisors.add(this.beanFactory.getBean(name, Advisor.class));
                        }
                        catch (BeanCreationException ex) {
                            Throwable rootCause = ex.getMostSpecificCause();
                            if (rootCause instanceof BeanCurrentlyInCreationException) {
                                BeanCreationException bce = (BeanCreationException) rootCause;
                                if (this.beanFactory.isCurrentlyInCreation(bce.getBeanName())) {
                                    if (logger.isDebugEnabled()) {
                                        logger.debug("Skipping advisor '" + name +
                                                "' with dependency on currently created bean: " + ex.getMessage());
                                    }
                                    // Ignore: indicates a reference back to the bean we're trying to advise.
                                    // We want to find advisors other than the currently created bean itself.
                                    continue;
                                }
                            }
                            throw ex;
                        }
                    }
                }
            }
            return advisors;
        }
    

    整体的流程是通过BeanFactoryUtils.beanNamesForTypeIncludingAncestors(this.beanFactory, Advisor.class, true, false)获取到所有的Advisor类型的Bean的名称,如果名称的列表为空,返回空的列表,如果不为空,遍历名称,得到对应的Bean,添加到列表中,返回列表,第一部分到此结束,我们说下第二部分,也是我们应该格外关注的this.aspectJAdvisorsBuilder.buildAspectJAdvisors()

    public List<Advisor> buildAspectJAdvisors() {
            List<String> aspectNames = null;
    
            synchronized (this) {
                aspectNames = this.aspectBeanNames;
                if (aspectNames == null) {
                    List<Advisor> advisors = new LinkedList<Advisor>();
                    aspectNames = new LinkedList<String>();
                    String[] beanNames =
                            BeanFactoryUtils.beanNamesForTypeIncludingAncestors(this.beanFactory, Object.class, true, false);
                    for (String beanName : beanNames) {
                        if (!isEligibleBean(beanName)) {
                            continue;
                        }
                        // We must be careful not to instantiate beans eagerly as in this
                        // case they would be cached by the Spring container but would not
                        // have been weaved
                        Class<?> beanType = this.beanFactory.getType(beanName);
                        if (beanType == null) {
                            continue;
                        }
                        if (this.advisorFactory.isAspect(beanType)) {
                            aspectNames.add(beanName);
                            AspectMetadata amd = new AspectMetadata(beanType, beanName);
                            if (amd.getAjType().getPerClause().getKind() == PerClauseKind.SINGLETON) {
                                MetadataAwareAspectInstanceFactory factory =
                                        new BeanFactoryAspectInstanceFactory(this.beanFactory, beanName);
                                List<Advisor> classAdvisors = this.advisorFactory.getAdvisors(factory);
                                if (this.beanFactory.isSingleton(beanName)) {
                                    this.advisorsCache.put(beanName, classAdvisors);
                                }
                                else {
                                    this.aspectFactoryCache.put(beanName, factory);
                                }
                                advisors.addAll(classAdvisors);
                            }
                            else {
                                // Per target or per this.
                                if (this.beanFactory.isSingleton(beanName)) {
                                    throw new IllegalArgumentException("Bean with name '" + beanName +
                                            "' is a singleton, but aspect instantiation model is not singleton");
                                }
                                MetadataAwareAspectInstanceFactory factory =
                                        new PrototypeAspectInstanceFactory(this.beanFactory, beanName);
                                this.aspectFactoryCache.put(beanName, factory);
                                advisors.addAll(this.advisorFactory.getAdvisors(factory));
                            }
                        }
                    }
                    this.aspectBeanNames = aspectNames;
                    return advisors;
                }
            }
    
            if (aspectNames.isEmpty()) {
                return Collections.emptyList();
            }
            List<Advisor> advisors = new LinkedList<Advisor>();
            for (String aspectName : aspectNames) {
                List<Advisor> cachedAdvisors = this.advisorsCache.get(aspectName);
                if (cachedAdvisors != null) {
                    advisors.addAll(cachedAdvisors);
                }
                else {
                    MetadataAwareAspectInstanceFactory factory = this.aspectFactoryCache.get(aspectName);
                    advisors.addAll(this.advisorFactory.getAdvisors(factory));
                }
            }
            return advisors;
        }
    
    

    思路差不多,通过BeanFactoryUtils.beanNamesForTypeIncludingAncestors(this.beanFactory, Object.class, true, false)获取到容器中的所有的Bean的名称,是个列表,遍历列表,根据每个Bean的名称,获取对应的Bean的类型,根据beanType判断是否是切面this.advisorFactory.isAspect(beanType)

    @Override
        public boolean isAspect(Class<?> clazz) {
            return (hasAspectAnnotation(clazz) && !compiledByAjc(clazz));
        }
    
        private boolean hasAspectAnnotation(Class<?> clazz) {
            return (AnnotationUtils.findAnnotation(clazz, Aspect.class) != null);
        }
    
        /**
         * We need to detect this as "code-style" AspectJ aspects should not be
         * interpreted by Spring AOP.
         */
        private boolean compiledByAjc(Class<?> clazz) {
            // The AJTypeSystem goes to great lengths to provide a uniform appearance between code-style and
            // annotation-style aspects. Therefore there is no 'clean' way to tell them apart. Here we rely on
            // an implementation detail of the AspectJ compiler.
            for (Field field : clazz.getDeclaredFields()) {
                if (field.getName().startsWith(AJC_MAGIC)) {
                    return true;
                }
            }
            return false;
        }
    

    判断的条件很简单,这个类必须有@Aspect这个注解,并且没有被AspectJ编译过,判断的条件就是这个类中所有的属性,不能是“ajc$”开头。通过这两个判断我们找到了切面类,将这个beanName放入到了aspectNames中缓存。随后根据beanType和beanName创建了AspectMetadata的实例,一般我们不是使用@Aspectj注解的value,所以amd.getAjType().getPerClause().getKind()一般是PerClauseKind.SINGLETON这段代码和本讲无关,所有没有深入讲解,有兴趣的同学可以自己查看。然后进入下面的流程,根据beanFactory和beanName创建了一个MetadataAwareAspectInstanceFactory的实例factory,通过List<Advisor> classAdvisors = this.advisorFactory.getAdvisors(factory)获取Advisor列表。可以看一下org.springframework.aop.aspectj.annotation.ReflectiveAspectJAdvisorFactory#getAdvisors的源码

    @Override
        public List<Advisor> getAdvisors(MetadataAwareAspectInstanceFactory aspectInstanceFactory) {
            Class<?> aspectClass = aspectInstanceFactory.getAspectMetadata().getAspectClass();
            String aspectName = aspectInstanceFactory.getAspectMetadata().getAspectName();
            validate(aspectClass);
    
            // We need to wrap the MetadataAwareAspectInstanceFactory with a decorator
            // so that it will only instantiate once.
            MetadataAwareAspectInstanceFactory lazySingletonAspectInstanceFactory =
                    new LazySingletonAspectInstanceFactoryDecorator(aspectInstanceFactory);
    
            List<Advisor> advisors = new LinkedList<Advisor>();
            //关注点2
            for (Method method : getAdvisorMethods(aspectClass)) {
                Advisor advisor = getAdvisor(method, lazySingletonAspectInstanceFactory, advisors.size(), aspectName);
                if (advisor != null) {
                    advisors.add(advisor);
                }
            }
    
            // If it's a per target aspect, emit the dummy instantiating aspect.
            if (!advisors.isEmpty() && lazySingletonAspectInstanceFactory.getAspectMetadata().isLazilyInstantiated()) {
                Advisor instantiationAdvisor = new SyntheticInstantiationAdvisor(lazySingletonAspectInstanceFactory);
                advisors.add(0, instantiationAdvisor);
            }
    
            // Find introduction fields.
            for (Field field : aspectClass.getDeclaredFields()) {
                Advisor advisor = getDeclareParentsAdvisor(field);
                if (advisor != null) {
                    advisors.add(advisor);
                }
            }
    
            return advisors;
        }
    

    看一下关注点2,根据aspectClass获取这个类中的AdvisorMethod

    private List<Method> getAdvisorMethods(Class<?> aspectClass) {
            final List<Method> methods = new LinkedList<Method>();
            ReflectionUtils.doWithMethods(aspectClass, new ReflectionUtils.MethodCallback() {
                @Override
                public void doWith(Method method) throws IllegalArgumentException {
                    // Exclude pointcuts
                    if (AnnotationUtils.getAnnotation(method, Pointcut.class) == null) {
                        methods.add(method);
                    }
                }
            });
            Collections.sort(methods, METHOD_COMPARATOR);
            return methods;
        }
    

    获取这个类上带有@Pointcut注解的方法,并且排序。通过Advisor advisor = getAdvisor(method, lazySingletonAspectInstanceFactory, advisors.size(), aspectName)将带有@Pointcut注解的方法变成Advisor类型的实例,放入advisors这个集合中。方法可以变成Advisor类型的实例,属性也可以,如果属性上有@DeclareParents注解,根据此注解生成DeclareParentsAdvisor类型的实例,添加到advisors这个集合中返回。OK,this.advisorFactory.getAdvisors(factory)这个方法解释的差不多了,随后在将beanName和查到的这些List<Advisor>放入到advisorsCache这个Map中缓存。遍历结束后,将查到的所有的advisors返回,这是我们shouldSkip的关键流程--查询Advisors。再继续,如果beanName不为空,并且getCustomTargetSource(beanClass, beanName)得到的targetSource不为空,就会添加这个beanName到targetSourcedBeans这个Set中缓存,接下来有一个非常重要的方法getAdvicesAndAdvisorsForBean(beanClass, beanName, targetSource)根据指定的条件获取Advisors,也就是拦截器。我们看下他是怎么获取这些拦截器的。

        @Override
        protected Object[] getAdvicesAndAdvisorsForBean(Class<?> beanClass, String beanName, TargetSource targetSource) {
            List<Advisor> advisors = findEligibleAdvisors(beanClass, beanName);
            if (advisors.isEmpty()) {
                return DO_NOT_PROXY;
            }
            return advisors.toArray();
        }
    
        protected List<Advisor> findEligibleAdvisors(Class<?> beanClass, String beanName) {
            List<Advisor> candidateAdvisors = findCandidateAdvisors();
            List<Advisor> eligibleAdvisors = findAdvisorsThatCanApply(candidateAdvisors, beanClass, beanName);
            extendAdvisors(eligibleAdvisors);
            if (!eligibleAdvisors.isEmpty()) {
                eligibleAdvisors = sortAdvisors(eligibleAdvisors);
            }
            return eligibleAdvisors;
        }
    
    

    我们看到了一个熟悉的方法findCandidateAdvisors获取所有的Advisors,但是我们不知道这个BeanClass会用到哪些Advisors或者都用不到,就需要一个挑选的过程,这个挑选的过程就是findAdvisorsThatCanApply方法

        protected List<Advisor> findAdvisorsThatCanApply(
                List<Advisor> candidateAdvisors, Class<?> beanClass, String beanName) {
    
            ProxyCreationContext.setCurrentProxiedBeanName(beanName);
            try {
                return AopUtils.findAdvisorsThatCanApply(candidateAdvisors, beanClass);
            }
            finally {
                ProxyCreationContext.setCurrentProxiedBeanName(null);
            }
        }
        
        public static List<Advisor> findAdvisorsThatCanApply(List<Advisor> candidateAdvisors, Class<?> clazz) {
            if (candidateAdvisors.isEmpty()) {
                return candidateAdvisors;
            }
            List<Advisor> eligibleAdvisors = new LinkedList<Advisor>();
            for (Advisor candidate : candidateAdvisors) {
                if (candidate instanceof IntroductionAdvisor && canApply(candidate, clazz)) {
                    eligibleAdvisors.add(candidate);
                }
            }
            boolean hasIntroductions = !eligibleAdvisors.isEmpty();
            for (Advisor candidate : candidateAdvisors) {
                if (candidate instanceof IntroductionAdvisor) {
                    // already processed
                    continue;
                }
                if (canApply(candidate, clazz, hasIntroductions)) {
                    eligibleAdvisors.add(candidate);
                }
            }
            return eligibleAdvisors;
        }
    
    

    整体来说,挑选的方法集中在了canApply,所做的操作就是根据@Pointcut注解中value定义的格式,来匹配这个Bean,看能不能匹配上,能匹配上就是canApply.然后返回针对这个BeanClass能匹配上的Advisor。OK,那么Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(beanClass, beanName, targetSource)的结果就是找到了这个类对应应该执行的Advisor,最后就是将这个类和这些Advisor包装成一个动态代理对象返回,也就是Object proxy = createProxy(beanClass, beanName, specificInterceptors, targetSource)

    
        protected Object createProxy(
                Class<?> beanClass, String beanName, Object[] specificInterceptors, TargetSource targetSource) {
    
            if (this.beanFactory instanceof ConfigurableListableBeanFactory) {
                AutoProxyUtils.exposeTargetClass((ConfigurableListableBeanFactory) this.beanFactory, beanName, beanClass);
            }
    
            ProxyFactory proxyFactory = new ProxyFactory();
            proxyFactory.copyFrom(this);
    
            if (!proxyFactory.isProxyTargetClass()) {
                if (shouldProxyTargetClass(beanClass, beanName)) {
                    proxyFactory.setProxyTargetClass(true);
                }
                else {
                    evaluateProxyInterfaces(beanClass, proxyFactory);
                }
            }
    
            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(getProxyClassLoader());
        }
    

    创建一个proxyFactory,往其中添加必要的属性,其中注意的是addAdvisor,添加完善后,开始调用proxyFactory.getProxy得到对应的动态代理对象

    #org.springframework.aop.framework.ProxyFactory#getProxy(java.lang.ClassLoader)
    public Object getProxy(ClassLoader classLoader) {
            return createAopProxy().getProxy(classLoader);
        }
    
    #org.springframework.aop.framework.ProxyCreatorSupport#createAopProxy
    protected final synchronized AopProxy createAopProxy() {
            if (!this.active) {
                activate();
            }
            return getAopProxyFactory().createAopProxy(this);
        }
        
    
    #org.springframework.aop.framework.DefaultAopProxyFactory#createAopProxy
        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() || Proxy.isProxyClass(targetClass)) {
                    return new JdkDynamicAopProxy(config);
                }
                return new ObjenesisCglibAopProxy(config);
            }
            else {
                return new JdkDynamicAopProxy(config);
            }
        }
    

    我们先看下JDK的动态代理的getProxy

    
    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(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);
        }
    

    再看下CGLIB动态代理的getProxy

        public CglibAopProxy(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;
            this.advisedDispatcher = new AdvisedDispatcher(this.advised);
        }
        
    @Override
        public Object getProxy() {
            return getProxy(null);
        }
    
        @Override
        public Object getProxy(ClassLoader classLoader) {
            if (logger.isDebugEnabled()) {
                logger.debug("Creating CGLIB proxy: target source is " + 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 (ClassUtils.isCglibProxyClass(rootClass)) {
                    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 ClassLoaderAwareUndeclaredThrowableStrategy(classLoader));
    
                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 ex) {
                throw new AopConfigException("Could not generate CGLIB subclass of class [" +
                        this.advised.getTargetClass() + "]: " +
                        "Common causes of this problem include using a final class or a non-visible class",
                        ex);
            }
            catch (IllegalArgumentException ex) {
                throw new AopConfigException("Could not generate CGLIB subclass of class [" +
                        this.advised.getTargetClass() + "]: " +
                        "Common causes of this problem include using a final class or a non-visible class",
                        ex);
            }
            catch (Exception ex) {
                // TargetSource.getTarget() failed
                throw new AopConfigException("Unexpected AOP exception", ex);
            }
        }
        
        
        @Override
        @SuppressWarnings("unchecked")
        protected Object createProxyClassAndInstance(Enhancer enhancer, Callback[] callbacks) {
            Class<?> proxyClass = enhancer.createClass();
            Object proxyInstance = null;
    
            if (objenesis.isWorthTrying()) {
                try {
                    proxyInstance = objenesis.newInstance(proxyClass, enhancer.getUseCache());
                }
                catch (Throwable ex) {
                    logger.debug("Unable to instantiate proxy using Objenesis, " +
                            "falling back to regular proxy construction", ex);
                }
            }
    
            if (proxyInstance == null) {
                // Regular instantiation via default constructor...
                try {
                    proxyInstance = (this.constructorArgs != null ?
                            proxyClass.getConstructor(this.constructorArgTypes).newInstance(this.constructorArgs) :
                            proxyClass.newInstance());
                }
                catch (Throwable ex) {
                    throw new AopConfigException("Unable to instantiate proxy using Objenesis, " +
                            "and regular proxy instantiation via default constructor fails as well", ex);
                }
            }
    
            ((Factory) proxyInstance).setCallbacks(callbacks);
            return proxyInstance;
        }
    
    

    到目前为止我们讲了第一个生命周期方法postProcessBeforeInstantiation下面我们再看下第二个postProcessAfterInitialization的关键方法

        protected Object wrapIfNecessary(Object bean, String beanName, Object cacheKey) {
            if (beanName != null && this.targetSourcedBeans.contains(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;
        }
    

    所做的事情基本上和我们上面讲解的声明周期方法是一致的,获取Advices(getAdvicesAndAdvisorsForBean),生成动态代理对象createProxy( bean.getClass(), beanName, specificInterceptors, new SingletonTargetSource(bean)),今天我们就讲到这里,大家自己消化一下吧。

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