新闻动态

首页  >  新闻动态  >  技术教程

Spring aspect 解析

2024-01-05 15:58:03 eye118

 介绍

  • Spring AOP的实现逻辑在AnnotationAwareAspectJAutoProxyCreator类,AOP的核心在于Bean对象初始化过程中如何查找关联的advice并通过创建动态代理。

  • 针对每个Bean在初始化过程中会遍历spring的context上下文查找所有的aop的切面对象,并针对切面对象的每个方法生成一个advisor对象用以匹配每个目标方法。

  • 关于动态代理包括JdkDynamicAopProxy和ObjenesisCglibAopProxy,后者依赖于cglib的enhancer用法。


AnnotationAwareAspectJAutoProxyCreator

AnnotationAwareAspectJAutoProxyCreator


public abstract class AbstractAutoProxyCreator extends ProxyProcessorSupport
        implements SmartInstantiationAwareBeanPostProcessor, BeanFactoryAware {

    protected Object wrapIfNecessary(Object bean, String beanName, Object cacheKey) {
        // 过滤无关不需要的类
        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;
        }

        // 查找该Bean是否有关联的增强类,如果有则创建增强代理
        Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(bean.getClass(), beanName, null);
        if (specificInterceptors != DO_NOT_PROXY) {
            this.advisedBeans.put(cacheKey, Boolean.TRUE);

            // 创建切面的代理对象
            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;
    }
}

  • wrapIfNecessary方法核心获取bean是否有相关的增强对象,如果存在增强对象就创建动态代理。

  • 第一个核心逻辑是查找bean的相关的增强Advisor对象。

  • 第二个核心逻辑是针对bean和增强对象创建代理对象proxy。


查找增强Advisor


public abstract class AbstractAutoProxyCreator extends ProxyProcessorSupport
        implements SmartInstantiationAwareBeanPostProcessor, BeanFactoryAware {

    @Override
    protected Object[] getAdvicesAndAdvisorsForBean(Class<?> beanClass, String beanName, TargetSource targetSource) {
        // 找到符合要求的Advisors
        List<Advisor> advisors = findEligibleAdvisors(beanClass, beanName);
        if (advisors.isEmpty()) {
            return DO_NOT_PROXY;
        }
        return advisors.toArray();
    }


    protected List<Advisor> findEligibleAdvisors(Class<?> beanClass, String beanName) {
        // 查找候选的candidateAdvisors
        List<Advisor> candidateAdvisors = findCandidateAdvisors();
        // 在候选的candidateAdvisors中查找能够应用到beanClass的Advisors
        List<Advisor> eligibleAdvisors = findAdvisorsThatCanApply(candidateAdvisors, beanClass, beanName);
        extendAdvisors(eligibleAdvisors);
        if (!eligibleAdvisors.isEmpty()) {
            eligibleAdvisors = sortAdvisors(eligibleAdvisors);
        }
        return eligibleAdvisors;
    }
}


public class AnnotationAwareAspectJAutoProxyCreator extends AspectJAwareAdvisorAutoProxyCreator {

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

public class BeanFactoryAspectJAdvisorsBuilder {

    private final ListableBeanFactory beanFactory;
    private final AspectJAdvisorFactory advisorFactory;
    private volatile List<String> aspectBeanNames;
    private final Map<String, List<Advisor>> advisorsCache = new ConcurrentHashMap<String, List<Advisor>>();
    private final Map<String, MetadataAwareAspectInstanceFactory> aspectFactoryCache =
            new ConcurrentHashMap<String, MetadataAwareAspectInstanceFactory>();

    public List<Advisor> buildAspectJAdvisors() {
        List<String> aspectNames = this.aspectBeanNames;

        if (aspectNames == null) {
            synchronized (this) {
                aspectNames = this.aspectBeanNames;
                if (aspectNames == null) {
                    List<Advisor> advisors = new LinkedList<Advisor>();
                    aspectNames = new LinkedList<String>();

                    // 查找所有的bean的名称 
                    String[] beanNames = BeanFactoryUtils.beanNamesForTypeIncludingAncestors(
                            this.beanFactory, Object.class, true, false);
                    // 遍历所有的bean,判断是否是aspect的类
                    for (String beanName : beanNames) {

                        // 如果是aspect类,需要构建aspect的元数据AspectMetadata
                        Class<?> beanType = this.beanFactory.getType(beanName);
                        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);

                                // 创建Advisor的列表信息,advisorFactory是ReflectiveAspectJAdvisorFactory
                                // 获取切面类的增强方法advisor
                                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 {                              
                                MetadataAwareAspectInstanceFactory factory =
                                        new PrototypeAspectInstanceFactory(this.beanFactory, beanName);
                                this.aspectFactoryCache.put(beanName, factory);
                                advisors.addAll(this.advisorFactory.getAdvisors(factory));
                            }
                        }
                    }
                    this.aspectBeanNames = aspectNames;
                    return advisors;
                }
            }
        }
      // 省略相关代码
    }
}

  • getAdvicesAndAdvisorsForBean调用findEligibleAdvisors查找beanClass对应的增强对象Advisor列表。

  • 查找增强类的核心逻辑是遍历spring容器内的所有bean对象,如果是aspect切面类则获取Advisor对象。

  • findCandidateAdvisors负责查找所有Advisor对象,内部通过buildAspectJAdvisors查找Advisor对象。

  • buildAspectJAdvisors方法内部的advisorFactory是ReflectiveAspectJAdvisorFactory对象,通过advisorFactory的isAspect判断是否切面类,通过advisorFactory的getAdvisors获取Advisor对象。

  • findAdvisorsThatCanApply负责过滤Advisor对象,过滤和beanClass相关的Advisor列表。

  • Advisor对象是切面类的方法维度的对象,切面类的包含增强注解的方法都会对应一个Advisor对象。

ReflectiveAspectJAdvisorFactory


  • ReflectiveAspectJAdvisorFactory的类继承关系如图所示,核心关注判断切面类的逻辑。


查找增强Advisor之查找切面类


public abstract class AbstractAspectJAdvisorFactory implements AspectJAdvisorFactory {

    private static final String AJC_MAGIC = "ajc$";
    private static final Class<?>[] ASPECTJ_ANNOTATION_CLASSES = new Class<?>[] {
            Pointcut.class, Around.class, Before.class, After.class, AfterReturning.class, AfterThrowing.class};
    protected final ParameterNameDiscoverer parameterNameDiscoverer = new AspectJAnnotationParameterNameDiscoverer();

    @Override
    public boolean isAspect(Class<?> clazz) {
        return (hasAspectAnnotation(clazz) && !compiledByAjc(clazz));
    }

    private boolean hasAspectAnnotation(Class<?> clazz) {
        return (AnnotationUtils.findAnnotation(clazz, Aspect.class) != null);
    }
}


public abstract class AnnotationUtils {

    public static <A extends Annotation> A findAnnotation(Class<?> clazz, Class<A> annotationType) {
        return findAnnotation(clazz, annotationType, true);
    }

    private static <A extends Annotation> A findAnnotation(Class<?> clazz, Class<A> annotationType, boolean synthesize) {
        if (annotationType == null) {
            return null;
        }

        AnnotationCacheKey cacheKey = new AnnotationCacheKey(clazz, annotationType);
        A result = (A) findAnnotationCache.get(cacheKey);
        if (result == null) {
            result = findAnnotation(clazz, annotationType, new HashSet<Annotation>());
            if (result != null && synthesize) {
                result = synthesizeAnnotation(result, clazz);
                findAnnotationCache.put(cacheKey, result);
            }
        }
        return result;
    }

    private static <A extends Annotation> A findAnnotation(Class<?> clazz, Class<A> annotationType, Set<Annotation> visited) {
        try {
            Annotation[] anns = clazz.getDeclaredAnnotations();
            // 包含指定的注解
            for (Annotation ann : anns) {
                if (ann.annotationType() == annotationType) {
                    return (A) ann;
                }
            }
            for (Annotation ann : anns) {
                if (!isInJavaLangAnnotationPackage(ann) && visited.add(ann)) {
                    A annotation = findAnnotation(ann.annotationType(), annotationType, visited);
                    if (annotation != null) {
                        return annotation;
                    }
                }
            }
        }
        catch (Throwable ex) {
            handleIntrospectionFailure(clazz, ex);
            return null;
        }

        // 省略相关的代码
    }
}

  • AnnotationUtils的findAnnotation查找是否存在aspect的注解。


查找增强Advisor之获取Advisor


public class ReflectiveAspectJAdvisorFactory extends AbstractAspectJAdvisorFactory implements Serializable {

    @Override
    public List<Advisor> getAdvisors(MetadataAwareAspectInstanceFactory aspectInstanceFactory) {

        Class<?> aspectClass = aspectInstanceFactory.getAspectMetadata().getAspectClass();
        String aspectName = aspectInstanceFactory.getAspectMetadata().getAspectName();
        validate(aspectClass);

        MetadataAwareAspectInstanceFactory lazySingletonAspectInstanceFactory =
                new LazySingletonAspectInstanceFactoryDecorator(aspectInstanceFactory);

        List<Advisor> advisors = new ArrayList<Advisor>();
        // getAdvisorMethods负责获取AdvisorMethods
        for (Method method : getAdvisorMethods(aspectClass)) {
             // 获取Advisor
            Advisor advisor = getAdvisor(method, lazySingletonAspectInstanceFactory, advisors.size(), aspectName);
            if (advisor != null) {
                advisors.add(advisor);
            }
        }

        if (!advisors.isEmpty() && lazySingletonAspectInstanceFactory.getAspectMetadata().isLazilyInstantiated()) {
            Advisor instantiationAdvisor = new SyntheticInstantiationAdvisor(lazySingletonAspectInstanceFactory);
            advisors.add(0, instantiationAdvisor);
        }

        for (Field field : aspectClass.getDeclaredFields()) {
            Advisor advisor = getDeclareParentsAdvisor(field);
            if (advisor != null) {
                advisors.add(advisor);
            }
        }

        return advisors;
    }

    private List<Method> getAdvisorMethods(Class<?> aspectClass) {
        final List<Method> methods = new ArrayList<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;
    }

    @Override
    public Advisor getAdvisor(Method candidateAdviceMethod, MetadataAwareAspectInstanceFactory aspectInstanceFactory,
            int declarationOrderInAspect, String aspectName) {

        validate(aspectInstanceFactory.getAspectMetadata().getAspectClass());
        // 获取 AspectJExpressionPointcut
        AspectJExpressionPointcut expressionPointcut = getPointcut(
                candidateAdviceMethod, aspectInstanceFactory.getAspectMetadata().getAspectClass());
        if (expressionPointcut == null) {
            return null;
        }
        // 创建Advisor对象InstantiationModelAwarePointcutAdvisorImpl
        return new InstantiationModelAwarePointcutAdvisorImpl(expressionPointcut, candidateAdviceMethod,
                this, aspectInstanceFactory, declarationOrderInAspect, aspectName);
    }

    private AspectJExpressionPointcut getPointcut(Method candidateAdviceMethod, Class<?> candidateAspectClass) {

        // 查询对应的方法candidateAdviceMethod是否包含指定的aspect相关的注解
        AspectJAnnotation<?> aspectJAnnotation =
                AbstractAspectJAdvisorFactory.findAspectJAnnotationOnMethod(candidateAdviceMethod);
        if (aspectJAnnotation == null) {
            return null;
        }
        // 创建AspectJExpressionPointcut对象
        AspectJExpressionPointcut ajexp =
                new AspectJExpressionPointcut(candidateAspectClass, new String[0], new Class<?>[0]);
        ajexp.setExpression(aspectJAnnotation.getPointcutExpression());
        ajexp.setBeanFactory(this.beanFactory);
        return ajexp;
    }
}

public abstract class AbstractAspectJAdvisorFactory implements AspectJAdvisorFactory {

    private static final String AJC_MAGIC = "ajc$";

    private static final Class<?>[] ASPECTJ_ANNOTATION_CLASSES = new Class<?>[] {
            Pointcut.class, Around.class, Before.class, After.class, AfterReturning.class, AfterThrowing.class};

    @SuppressWarnings("unchecked")
    protected static AspectJAnnotation<?> findAspectJAnnotationOnMethod(Method method) {
        for (Class<?> clazz : ASPECTJ_ANNOTATION_CLASSES) {
            AspectJAnnotation<?> foundAnnotation = findAnnotation(method, (Class<Annotation>) clazz);
            if (foundAnnotation != null) {
                return foundAnnotation;
            }
        }
        return null;
    }
}

  • getAdvisorMethods负责从切面类aspectClass获取相关的Method。

  • getAdvisor负责将包含aspct注解的Method转换成Advisor对象。

  • findAspectJAnnotationOnMethod判断方法是否包含aspect注解如Around.class等

  • 切面类aspectClass的每个包含aspect的注解method会生成AspectJExpressionPointcut对象,进而生成InstantiationModelAwarePointcutAdvisorImpl对象。

  • 切面类包含aspect注解的method会生成Advisor对象,即InstantiationModelAwarePointcutAdvisorImpl对象


 编辑

InstantiationModelAwarePointcutAdvisorImpl


  • Advisor对象是InstantiationModelAwarePointcutAdvisorImpl对象。


查找增强Advisor之过滤Advisor


public abstract class AbstractAdvisorAutoProxyCreator extends AbstractAutoProxyCreator {

    private BeanFactoryAdvisorRetrievalHelper advisorRetrievalHelper;

    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 abstract class AopUtils {

    public static List<Advisor> findAdvisorsThatCanApply(List<Advisor> candidateAdvisors, Class<?> clazz) {
        if (candidateAdvisors.isEmpty()) {
            return candidateAdvisors;
        }
        List<Advisor> eligibleAdvisors = new LinkedList<Advisor>();
        // 遍历所有的Advisor进行匹配返回符合的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;
    }

    public static boolean canApply(Advisor advisor, Class<?> targetClass) {
        return canApply(advisor, targetClass, false);
    }

    public static boolean canApply(Advisor advisor, Class<?> targetClass, boolean hasIntroductions) {
        if (advisor instanceof IntroductionAdvisor) {
            return ((IntroductionAdvisor) advisor).getClassFilter().matches(targetClass);
        }
        else if (advisor instanceof PointcutAdvisor) {
            PointcutAdvisor pca = (PointcutAdvisor) advisor;
            return canApply(pca.getPointcut(), targetClass, hasIntroductions);
        }
        else {
            return true;
        }
    }

    public static boolean canApply(Pointcut pc, Class<?> targetClass, boolean hasIntroductions) {
        if (!pc.getClassFilter().matches(targetClass)) {
            return false;
        }

        MethodMatcher methodMatcher = pc.getMethodMatcher();
        if (methodMatcher == MethodMatcher.TRUE) {
            return true;
        }

        IntroductionAwareMethodMatcher introductionAwareMethodMatcher = null;
        if (methodMatcher instanceof IntroductionAwareMethodMatcher) {
            introductionAwareMethodMatcher = (IntroductionAwareMethodMatcher) methodMatcher;
        }

        Set<Class<?>> classes = new LinkedHashSet<Class<?>>(ClassUtils.getAllInterfacesForClassAsSet(targetClass));
        classes.add(targetClass);
        for (Class<?> clazz : classes) {
            // 获取类下面的所有Method对象
            Method[] methods = ReflectionUtils.getAllDeclaredMethods(clazz);
            for (Method method : methods) {
                if ((introductionAwareMethodMatcher != null &&
                        introductionAwareMethodMatcher.matches(method, targetClass, hasIntroductions)) ||
                      // methodMatcher包含AspectJExpressionPointcut
                        methodMatcher.matches(method, targetClass)) {
                    return true;
                }
            }
        }

        return false;
    }
}

  • findAdvisorsThatCanApply查找匹配的Advisors。

  • findAdvisorsThatCanApply的条件是目标类的某个方法和Advisor匹配,只要目标类的某个方法和Advisor匹配上就表明该Advisor符合条件。


创建代理流程

AbstractAutoProxyCreator


public abstract class AbstractAutoProxyCreator extends ProxyProcessorSupport
        implements SmartInstantiationAwareBeanPostProcessor, BeanFactoryAware {

    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);
            }
        }
                // 将拦截器Interceptors封装成增强器advisors
        Advisor[] advisors = buildAdvisors(beanName, specificInterceptors);
                // 加入增强器
        proxyFactory.addAdvisors(advisors);
        proxyFactory.setTargetSource(targetSource);
                // 定制代理
        customizeProxyFactory(proxyFactory);
        proxyFactory.setFrozen(this.freezeProxy);
        if (advisorsPreFiltered()) {
            proxyFactory.setPreFiltered(true);
        }

                // 封装出proxyFactory并由它完成后续的工作
        return proxyFactory.getProxy(getProxyClassLoader());
    }
}

  • ProxyFactory负责生成动态代理的Proxy对象。

  • ProxyFactory设置了代理对象targetSource和拦截器对象advisors。

  • ProxyFactory通过getProxy来生成动态代理的Proxy对象。


ProxyFactory


public class ProxyFactory extends ProxyCreatorSupport {

    public Object getProxy(ClassLoader classLoader) {
        // createAopProxy创建动态代理实现对象
        // getProxy负责创建动态代理
        return createAopProxy().getProxy(classLoader);
    }
}

public class ProxyCreatorSupport extends AdvisedSupport {

    protected final synchronized AopProxy createAopProxy() {
        if (!this.active) {
            activate();
        }
        // 这里我们需要注意的是 ,这里 createAopProxy 传入的是 this。也就是说这里参数传递实际上是ProxyFactroy
        return getAopProxyFactory().createAopProxy(this);
    }
}

public class DefaultAopProxyFactory implements AopProxyFactory, Serializable {

    @Override
    public AopProxy createAopProxy(AdvisedSupport config) throws AopConfigException {
        if (config.isOptimize() || config.isProxyTargetClass() || hasNoUserSuppliedProxyInterfaces(config)) {
            Class<?> targetClass = config.getTargetClass();

            if (targetClass.isInterface() || Proxy.isProxyClass(targetClass)) {
                return new JdkDynamicAopProxy(config);
            }
            return new ObjenesisCglibAopProxy(config);
        }
        else {
            return new JdkDynamicAopProxy(config);
        }
    }
}

  • createAopProxy会根据是否实现Interface来选用cglib还是jdk的动态代理。

  • ObjenesisCglibAopProxy是cglib形式的动态代理。

  • JdkDynamicAopProxy是jdk形式的动态代理。


CglibAopProxy


class CglibAopProxy implements AopProxy, Serializable {

    @Override
    public Object getProxy(ClassLoader classLoader) {

        try {
                        // 获取代理类,rootClass表示的是被代理类
            Class<?> rootClass = this.advised.getTargetClass();
            Class<?> proxySuperClass = rootClass;
            if (ClassUtils.isCglibProxyClass(rootClass)) {
                proxySuperClass = rootClass.getSuperclass();
                Class<?>[] additionalInterfaces = rootClass.getInterfaces();
                for (Class<?> additionalInterface : additionalInterfaces) {
                    this.advised.addInterface(additionalInterface);
                }
            }

            validateClassIfNecessary(proxySuperClass, classLoader);
            // 配置 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));
            // 获取代理的回调方法
            Callback[] callbacks = getCallbacks(rootClass);
            Class<?>[] types = new Class<?>[callbacks.length];
            for (int x = 0; x < types.length; x++) {
                types[x] = callbacks[x].getClass();
            }
            enhancer.setCallbackFilter(new ProxyCallbackFilter(
                    this.advised.getConfigurationOnlyCopy(), this.fixedInterceptorMap, this.fixedInterceptorOffset));
            enhancer.setCallbackTypes(types);
            // 创建代理对象
            return createProxyClassAndInstance(enhancer, callbacks);
        }
        catch (CodeGenerationException ex) {
        }
        catch (IllegalArgumentException ex) {
        }
        catch (Throwable ex) {
        }
    }

    protected Object createProxyClassAndInstance(Enhancer enhancer, Callback[] callbacks) {
        enhancer.setInterceptDuringConstruction(false);
        enhancer.setCallbacks(callbacks);
        return (this.constructorArgs != null ?
                enhancer.create(this.constructorArgTypes, this.constructorArgs) :
                enhancer.create());
    }
}

  • CglibAopProxy的核心通过Enhancer实现动态代理的创建。

  • Enhancer的核心变量superclass代表被代理对象类,callbacks代表拦截器,callbackFilter代表callback的匹配过滤器。


Callback


class CglibAopProxy implements AopProxy, Serializable {

    private Callback[] getCallbacks(Class<?> rootClass) throws Exception {
        boolean exposeProxy = this.advised.isExposeProxy();
        boolean isFrozen = this.advised.isFrozen();
        boolean isStatic = this.advised.getTargetSource().isStatic();

        Callback aopInterceptor = new DynamicAdvisedInterceptor(this.advised);

        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()));
        }

        Callback targetDispatcher = (isStatic ?
                new StaticDispatcher(this.advised.getTargetSource().getTarget()) : new SerializableNoOp());
        // 回调集合。其中包含aopInterceptor 中包含了 Aspect 的增强
        //  advisedDispatcher 用于判断如果method是Advised.class声明的,则使用AdvisedDispatcher进行分发
        Callback[] mainCallbacks = new Callback[] {
                aopInterceptor,  
                targetInterceptor,  
                new SerializableNoOp(),  
                targetDispatcher, this.advisedDispatcher,
                new EqualsInterceptor(this.advised),
                new HashCodeInterceptor(this.advised)
        };

        Callback[] callbacks;

        if (isStatic && isFrozen) {
                // 省略相关的代码
        }
        else {
            callbacks = mainCallbacks;
        }
        return callbacks;
    }
}

  • mainCallbacks包含了所有的拦截器,期中aopInterceptor是核心的aspect相关的拦截器对象。

  • aopInterceptor是DynamicAdvisedInterceptor对象,是执行aop拦截的核心。


DynamicAdvisedInterceptor


class CglibAopProxy implements AopProxy, Serializable {

    private static class DynamicAdv