SpringCache源码深度解析

缓存是我们常用的一种优化系统的方案。

    无论是前端缓存还是应用层缓存或者数据库缓存，其本质都是将查询过的数据缓存下来，下次再次查询该数据的时候如果数据没有过期，则直接返回缓存中该数据即可，不再执行查询操作。

    SpringCache是我们常用的一种应用层缓存方案，其一般应用在方法上，下面我们先来看下具体的使用方式，然后再从源码角度分析其实现方案

1.SpringCache的使用

    1）maven引入依赖

        cache功能相关代码都在spring-context中，一般使用Spring的项目中都有该包，所以不用再单独引入

    2）Service（业务处理类，代码参考网上文章，非原创，有改动）

// 接口类
package cache;
 
public interface IService {
    Account getAccountByName(String userName);
    void updateAccount(Account account);
}
 
// 实现类
public class AccountService implements IService{
    @Override
    @Cacheable(value = "accountCache") // 使用了一个缓存名叫 accountCache
    public Account getAccountByName(String userName) {
        // 方法内部实现不考虑缓存逻辑，直接实现业务
        System.out.println("real query account." + userName);
        return getFromDB(userName);
    }
 
    @Override
    @CacheEvict(value="accountCache",key="#account.getName()")
    public void updateAccount(Account account) {
        updateDB(account); 
    }
 
    @CacheEvict(value = "accountCache", allEntries = true)
    public void reload() {
    }
 
    private Account getFromDB(String acctName) {
        System.out.println("real querying db..." + acctName);
        return new Account(acctName);
    }
 
    private void updateDB(Account account) {
        System.out.println("real update db..." + account.getName());
    }
}

如上所示：在方法上加上@cacheable等注解即可

3）Spring-cache-anno.xml文件（用于定义bean）

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:cache="http://www.springframework.org/schema/cache"
    xmlns:p="http://www.springframework.org/schema/p"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans.xsd
    http://www.springframework.org/schema/cache
    http://www.springframework.org/schema/cache/spring-cache.xsd">
 
    <!-- 添加driven -->
    <cache:annotation-driven />
    
    <bean id="accountServiceBean" class="cache.AccountService" />
    <!-- generic cache manager -->
    <bean id="cacheManager" class="org.springframework.cache.support.SimpleCacheManager">
        <property name="caches">
            <set>
                <bean
                    class="org.springframework.cache.concurrent.ConcurrentMapCacheFactoryBean"
                    p:name="accountCache" />
            </set>
        </property>
    </bean>
</beans>

使用默认的SimpleCacheManager

    4）测试（测试缓存是否生效）

public class Test {
 
    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("spring-cache-anno.xml");
        IService s = context.getBean(IService.class);
        // 第一次查询，应该走数据库
        System.out.print("first query...");
        s.getAccountByName("somebody");
        // 第二次查询，应该不查数据库，直接返回缓存的值
        System.out.print("second query...");
        s.getAccountByName("somebody");
        System.out.println();
    }
}
 
//result：
first query...
real query account.somebody
real querying db...somebody
second query...

总结：根据结果可以看到，第二次查询的时候没有真正执行getFromDB()方法，而是从缓存中取的数据

2.写在源码分析之前

    如果是我们来做的话，如何实现该功能？

    基于我们对Spring的一贯理解，这应该是个代理，我们在获取IService的bean时候，应该获取的是个代理类，代理类执行业务方法，先去查询是否在缓存中有该数据，如果有则直接从缓存中获取，如果没有，则调用AccountService的方法

    

3.SpringCache源码结构分析

    根据我们的示例可知，真正的内容都放在配置文件里了

    配置文件中添加了一个driven（真正的功能应该在这里实现的）

<cache:annotation-driven />

下面是两个bean（accountServiceBean是我们需要的，需要将AccountService注入到容器中。

    至于SimpleCacheManager暂时不知道其作用，只知道其实现了CacheManage接口，我们先暂时放一下）

<bean id="accountServiceBean" class="cache.AccountService" />
    <!-- generic cache manager -->
    <bean id="cacheManager" class="org.springframework.cache.support.SimpleCacheManager">
        <property name="caches">
            <set>
                <bean
                    class="org.springframework.cache.concurrent.ConcurrentMapCacheFactoryBean"
                    p:name="accountCache" />
            </set>
        </property>
    </bean>

  1）<cache:annotation-driven/>的分析

        但凡这种注解，都有对应的解析器，从之前分析AOP功能的源码可知，解析器都实现了NamespaceHandlerSupport类，我们来获取下NamespaceHandlerSupport的实现类都有哪些

 里面有一个叫做CacheNamespaceHandler的类，看名字就像这个，我们来看下这个类

2）CacheNamespaceHandler

public class CacheNamespaceHandler extends NamespaceHandlerSupport {
 
    static final String CACHE_MANAGER_ATTRIBUTE = "cache-manager";
 
    static final String DEFAULT_CACHE_MANAGER_BEAN_NAME = "cacheManager";
    ...
    @Override
    public void init() {
        // 主要是这句代码
        registerBeanDefinitionParser("annotation-driven", new AnnotationDrivenCacheBeanDefinitionParser());
        registerBeanDefinitionParser("advice", new CacheAdviceParser());
    }
}

Spring会默认调用其init()方法，annotation-driven对应的是AnnotationDrivenCacheBeanDefinitionParser解析器，我们来看下这个解析器的作用

    3）AnnotationDrivenCacheBeanDefinitionParser

@Override
    public BeanDefinition parse(Element element, ParserContext parserContext) {
        String mode = element.getAttribute("mode");// mode默认为proxy
        if ("aspectj".equals(mode)) {
            // mode="aspectj"
            registerCacheAspect(element, parserContext);
        }
        else {
            // 直接调用该方法
            registerCacheAdvisor(element, parserContext);
        }
 
        return null;
    }
 
// registerCacheAdvisor()
    private void registerCacheAdvisor(Element element, ParserContext parserContext) {
        // 1.注册ProxyCreator类 在4）中详细分析
        AopNamespaceUtils.registerAutoProxyCreatorIfNecessary(parserContext, element);
        // 2.注册CacheAdvisor 在5）中详细分析
        SpringCachingConfigurer.registerCacheAdvisor(element, parserContext);
        if (jsr107Present && jcacheImplPresent) {
            // 默认不会调用
            JCacheCachingConfigurer.registerCacheAdvisor(element, parserContext);
        }
    }

4）AopNamespaceUtils.registerAutoProxyCreatorIfNecessary(parserContext, element)

public static void registerAutoProxyCreatorIfNecessary(
            ParserContext parserContext, Element sourceElement) {
        // 重点在这里
        BeanDefinition beanDefinition = AopConfigUtils.registerAutoProxyCreatorIfNecessary(
                parserContext.getRegistry(), parserContext.extractSource(sourceElement));
        useClassProxyingIfNecessary(parserContext.getRegistry(), sourceElement);
        registerComponentIfNecessary(beanDefinition, parserContext);
    }
 
// AopConfigUtils.registerAutoProxyCreatorIfNecessary()
    public static BeanDefinition registerAutoProxyCreatorIfNecessary(BeanDefinitionRegistry registry, Object source) {
        // 重点在这里
        return registerOrEscalateApcAsRequired(InfrastructureAdvisorAutoProxyCreator.class, registry, source);
    }

可以看到，主要是为了将InfrastructureAdvisorAutoProxyCreator注册到容器中

5）SpringCachingConfigurer.registerCacheAdvisor(element, parserContext)

private static void registerCacheAdvisor(Element element, ParserContext parserContext) {
            if (!parserContext.getRegistry().containsBeanDefinition(CacheManagementConfigUtils.CACHE_ADVISOR_BEAN_NAME)) {
                Object eleSource = parserContext.extractSource(element);
 
                // 1.注册AnnotationCacheOperationSource类到容器中
                RootBeanDefinition sourceDef = new RootBeanDefinition("org.springframework.cache.annotation.AnnotationCacheOperationSource");
                sourceDef.setSource(eleSource);
                sourceDef.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
                String sourceName = parserContext.getReaderContext().registerWithGeneratedName(sourceDef);
 
                // 2.注册CacheInterceptor类到容器中
                RootBeanDefinition interceptorDef = new RootBeanDefinition(CacheInterceptor.class);
                interceptorDef.setSource(eleSource);
                interceptorDef.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
                parseCacheResolution(element, interceptorDef, false);
                parseErrorHandler(element, interceptorDef);
                CacheNamespaceHandler.parseKeyGenerator(element, interceptorDef);
                interceptorDef.getPropertyValues().add("cacheOperationSources", new RuntimeBeanReference(sourceName));
                String interceptorName = parserContext.getReaderContext().registerWithGeneratedName(interceptorDef);
 
                // 3.注册BeanFactoryCacheOperationSourceAdvisor类到容器中，
                RootBeanDefinition advisorDef = new RootBeanDefinition(BeanFactoryCacheOperationSourceAdvisor.class);
                advisorDef.setSource(eleSource);
                advisorDef.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
                // 注意这里，将AnnotationCacheOperationSource和CacheInterceptor作为其属性注入进来
                advisorDef.getPropertyValues().add("cacheOperationSource", new RuntimeBeanReference(sourceName));
                advisorDef.getPropertyValues().add("adviceBeanName", interceptorName);
                if (element.hasAttribute("order")) {
                    advisorDef.getPropertyValues().add("order", element.getAttribute("order"));
                }
                // 注意这句，将BeanFactoryCacheOperationSourceAdvisor类的注册名称设置为
                // org.springframework.cache.config.internalCacheAdvisor
                // 在下面会用到这个名称
                parserContext.getRegistry().registerBeanDefinition(CacheManagementConfigUtils.CACHE_ADVISOR_BEAN_NAME, advisorDef);
 
                ...
            }
        }

总结：由以上分析可知，我们添加<cache:annotation-driven />注解，主要是将以下类注入进Spring容器

    * InfrastructureAdvisorAutoProxyCreator

    * AnnotationCacheOperationSource

    * CacheInterceptor（主要的拦截功能都实现在这里）

    * BeanFactoryCacheOperationSourceAdvisor（重点关注这个，这个类在创建代理的时候被使用）

    我们暂时只知道加载driven注解的时候，只是将这四个类注入到Spring容器中，而这些类具体在做什么，我们也不知道，更不知道与我们的AccountService类有什么关联。这些我们先暂时放一下，先看下CacheInterceptor和InfrastructureAdvisorAutoProxyCreator的功能简介

4.CacheInterceptor功能简单分析

其代码结构如下

可知：

    * 其实现了InitializingBean接口，则CacheInterceptor创建的时候会默认调用afterPropertiesSet()方法；

    * 其实现了SmartInitializingSingleton接口，则CacheInterceptor创建的时候会默认调用afterSingletonsInstantiated()方法

    * 其实现了MethodInterceptor接口，则在被其拦截的方法上，默认会调用其invoke()方法

    有关于这些接口的作用，不太明白的同学可以先看下对应的文章了解其大致作用

    1）初始化afterPropertiesSet()方法

// 只是做了校验，没有其他功能    
    public void afterPropertiesSet() {
        Assert.state(getCacheOperationSource() != null, "The 'cacheOperationSources' property is required: " +
                "If there are no cacheable methods, then don't use a cache aspect.");
        Assert.state(getErrorHandler() != null, "The 'errorHandler' property is required");
    }

2）初始化afterSingletonsInstantiated()方法

public void afterSingletonsInstantiated() {
        if (getCacheResolver() == null) {
            // Lazily initialize cache resolver via default cache manager...
            try {
                // 重点在这里
                // 从工厂类中获取CacheManager的实现类
                // 这里就与我们的Spring-cache-anno.xml配置文件中的创建的cacheManager 
                // bean关联起来了，在配置文件中创建的bean实现了接口CacheManager
                // 则会在这里被使用
                setCacheManager(this.beanFactory.getBean(CacheManager.class));
            }
            ...
        }
        this.initialized = true;
    }
        
// setCacheManager()
    public void setCacheManager(CacheManager cacheManager) {
        //     private CacheResolver cacheResolver;
        this.cacheResolver = new SimpleCacheResolver(cacheManager);
    }

3）invoke(）执行拦截方法（这个我们暂时先不分析，读者只需要知道这个拦截方法的存在即可）

public Object invoke(final MethodInvocation invocation) throws Throwable {
        Method method = invocation.getMethod();
 
        CacheOperationInvoker aopAllianceInvoker = new CacheOperationInvoker() {
            @Override
            public Object invoke() {
                try {
                    return invocation.proceed();
                }
                catch (Throwable ex) {
                    throw new ThrowableWrapper(ex);
                }
            }
        };
 
        try {
            return execute(aopAllianceInvoker, invocation.getThis(), method, invocation.getArguments());
        }
        catch (CacheOperationInvoker.ThrowableWrapper th) {
            throw th.getOriginal();
        }
    }

总结4：

    CacheInterceptor主要是一个方法拦截器，在初始化的时候将CacheManager的实现类（由用户自定义实现）添加进来；

    invoke()方法，真正执行拦截的方法

5.InfrastructureAdvisorAutoProxyCreator功能分析

    其代码结构如下：

可以看到，其实现了BeanPostProcessor接口，则Spring在创建bean的时候，会默认调用InfrastructureAdvisorAutoProxyCreator的postProcessAfterInitialization()方法，就是在这个方法中创建代理类的，下面我们来看下这个方法

 1）AbstractAutoProxyCreator.postProcessAfterInitialization()

public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        if (bean != null) {
            Object cacheKey = getCacheKey(bean.getClass(), beanName);
            if (!this.earlyProxyReferences.contains(cacheKey)) {
                // 重要方法
                return wrapIfNecessary(bean, beanName, cacheKey);
            }
        }
        return bean;
    }
 
// wrapIfNecessary()
    protected Object wrapIfNecessary(Object bean, String beanName, Object cacheKey) {
        ...
 
        // 1.获取当前类的所有切面拦截类，在2）中详细分析
        Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(bean.getClass(), beanName, null);
        // 2.如果拦截类不为空，则需要创建当前类的代理类
        if (specificInterceptors != DO_NOT_PROXY) {
            this.advisedBeans.put(cacheKey, Boolean.TRUE);
            // 3.创建代理类，在3）中详细分析
            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;
    }

以上逻辑类似于之前分析的AOP源码，读者也可以先看下 https://blog.csdn.net/qq_26323323/article/details/81012855  

    2）getAdvicesAndAdvisorsForBean()获取当前类的所有切面拦截器

    本方法为抽象方法，实现由子类AbstractAdvisorAutoProxyCreator实现

protected Object[] getAdvicesAndAdvisorsForBean(Class<?> beanClass, String beanName, TargetSource targetSource) {
        List<Advisor> advisors = findEligibleAdvisors(beanClass, beanName);//重点在这里
        if (advisors.isEmpty()) {
            return DO_NOT_PROXY;
        }
        return advisors.toArray();
    }
 
// findEligibleAdvisors()
    protected List<Advisor> findEligibleAdvisors(Class<?> beanClass, String beanName) {
        // 1.获取所有的Advisor
        List<Advisor> candidateAdvisors = findCandidateAdvisors();
        // 2.获取适合当前类的Advisor
        List<Advisor> eligibleAdvisors = findAdvisorsThatCanApply(candidateAdvisors, beanClass, beanName);
        extendAdvisors(eligibleAdvisors);
        if (!eligibleAdvisors.isEmpty()) {
            eligibleAdvisors = sortAdvisors(eligibleAdvisors);
        }
        return eligibleAdvisors;
    }

* findCandidateAdvisors()获取所有的Advisor

//     findCandidateAdvisors()
    protected List<Advisor> findCandidateAdvisors() {
        return this.advisorRetrievalHelper.findAdvisorBeans();
    }
 
 
//findAdvisorBeans()
    public List<Advisor> findAdvisorBeans() {
        // Determine list of advisor bean names, if not cached already.
        String[] advisorNames = null;
        synchronized (this) {
            // 1.cachedAdvisorBeanNames=org.springframework.cache.config.internalCacheAdvisor
            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 {
                        // 2.从工厂中获取CacheInterceptor对应的bean
                        // 在上述代码 3节5）中，可知，
                        // org.springframework.cache.config.internalCacheAdvisor这个名称对应bean为
                        // BeanFactoryCacheOperationSourceAdvisor类，
                        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;
    }

总结2）：适合当前类的Advisor最终为BeanFactoryCacheOperationSourceAdvisor类，也就是我们之前在分析<cache:annotation-driven/>中注册的BeanFactoryCacheOperationSourceAdvisor bean

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

    创建代理类    

    这里笔者就不再继续分析了，具体读者可参考 https://blog.csdn.net/qq_26323323/article/details/81012855  博文中创建proxy过程分析一节

总结5：InfrastructureAdvisorAutoProxyCreator的主要作用就是实现了BeanPostProcessor接口，那么Spring的每个bean在创建的过程中，都需要调用其postProcessAfterInitialization()方法，在这个方法中查询出所有适合当前类的Advisor，然后创建当前类的代理类，并将Advisor封装进来，在以后调用当前类的方法时使用

6.代理类invoke()方法调用

    通过以上分析可知，Spring为我们创建的AccountService bean实际是一个关于AccountService的代理类，在调用AccountService的相关方法时，实际调用的是代理类的invoke()方法，下面我们就来分析下，invoke()方法被调用的过程，具体了解下我们的缓存是如何工作的

    由于本例是JDKProxy创建的方式，而非CGLIBProxy的创建方式，所以AccountService的代理类为JdkDynamicAopProxy，下面看下其invoke()方法

    1）JdkDynamicAopProxy.invoke()

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 {
            ...
            Object retVal;
 
            if (this.advised.exposeProxy) {
                // Make invocation available if necessary.
                oldProxy = AopContext.setCurrentProxy(proxy);
                setProxyContext = true;
            }
 
            target = targetSource.getTarget();
            if (target != null) {
                targetClass = target.getClass();
            }
 
            // 1.获取当前方法的拦截器链，也就是Advisor列表
            // 最终返回的是当前Advisor的拦截器MethodInterceptor列表
            // 在2）中详细分析
            List<Object> chain = this.advised.getInterceptorsAndDynamicInterceptionAdvice(method, targetClass);
 
            // 2.如果拦截器链为空，说明当前方法没有缓存注解，直接调用方法即可
            if (chain.isEmpty()) {
                Object[] argsToUse = AopProxyUtils.adaptArgumentsIfNecessary(method, args);
                retVal = AopUtils.invokeJoinpointUsingReflection(target, method, argsToUse);
            }
            // 3.说明当前方法有缓存注解，则需要先调用拦截器链的方法
            else {
                invocation = new ReflectiveMethodInvocation(proxy, target, method, args, targetClass, chain);
                // 真正的调用在这里
                // 在3）中详细分析
                retVal = invocation.proceed();
            }
 
            ...
            return retVal;
        }
        ...
    }

 2）AdvisedSupport.getInterceptorsAndDynamicInterceptionAdvice(method, targetClass);获取当前方法的拦截器链

public List<Object> getInterceptorsAndDynamicInterceptionAdvice(Method method, Class<?> targetClass) {
        MethodCacheKey cacheKey = new MethodCacheKey(method);
        List<Object> cached = this.methodCache.get(cacheKey);
        if (cached == null) {
            // 真正的实现在这里
            cached = this.advisorChainFactory.getInterceptorsAndDynamicInterceptionAdvice(
                    this, method, targetClass);
            this.methodCache.put(cacheKey, cached);
        }
        return cached;
    }
 
//DefaultAdvisorChainFactory.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);
        Class<?> actualClass = (targetClass != null ? targetClass : method.getDeclaringClass());
        boolean hasIntroductions = hasMatchingIntroductions(config, actualClass);
        AdvisorAdapterRegistry registry = GlobalAdvisorAdapterRegistry.getInstance();
 
        // 1.遍历当前bean的所有Advisor
        // 就当前示例而言，只有一个Advisor，就是之前创建的BeanFactoryCacheOperationSourceAdvisor
        for (Advisor advisor : config.getAdvisors()) {
            if (advisor instanceof PointcutAdvisor) {
                // Add it conditionally.
                PointcutAdvisor pointcutAdvisor = (PointcutAdvisor) advisor;
                if (config.isPreFiltered() || pointcutAdvisor.getPointcut().getClassFilter().matches(actualClass)) {
                    // 2.获取Advisor的Interceptor，也就是在分析<cache:annotation-driven />时
                    // 被添加到BeanFactoryCacheOperationSourceAdvisor类的CacheInterceptor类
                    MethodInterceptor[] interceptors = registry.getInterceptors(advisor);
                    MethodMatcher mm = pointcutAdvisor.getPointcut().getMethodMatcher();
                    if (MethodMatchers.matches(mm, method, actualClass, 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(actualClass)) {
                    Interceptor[] interceptors = registry.getInterceptors(advisor);
                    interceptorList.addAll(Arrays.asList(interceptors));
                }
            }
            else {
                Interceptor[] interceptors = registry.getInterceptors(advisor);
                interceptorList.addAll(Arrays.asList(interceptors));
            }
        }
 
        return interceptorList;
    }

所以，拦截器链最终返回的是我们之前分析的CacheInterceptor类

    3）ReflectiveMethodInvocation.proceed()拦截器链的调用分析

// InterceptedMethodInvocation.proceed()    
    public Object proceed() throws Throwable {
      try {
        // 主要就是遍历调用Interceptor的invoke方法
        return index == interceptors.length
            ? methodProxy.invokeSuper(proxy, arguments)
            : interceptors[index].invoke(
                new InterceptedMethodInvocation(proxy, methodProxy, arguments, index + 1));
      } catch (Throwable t) {
        pruneStacktrace(t);
        throw t;
      }
    }

那我们看下CacheInterceptor.invoke()方法

public Object invoke(final MethodInvocation invocation) throws Throwable {
        Method method = invocation.getMethod();
 
        CacheOperationInvoker aopAllianceInvoker = new CacheOperationInvoker() {
            @Override
            public Object invoke() {
                try {
                    return invocation.proceed();
                }
                catch (Throwable ex) {
                    throw new ThrowableWrapper(ex);
                }
            }
        };
 
        try {
            // 重点方法
            return execute(aopAllianceInvoker, invocation.getThis(), method, invocation.getArguments());
        }
        catch (CacheOperationInvoker.ThrowableWrapper th) {
            throw th.getOriginal();
        }
    }
 
//CacheAspectSupport.execute()
    protected Object execute(CacheOperationInvoker invoker, Object target, Method method, Object[] args) {
        // Check whether aspect is enabled (to cope with cases where the AJ is pulled in automatically)
        if (this.initialized) {
            Class<?> targetClass = getTargetClass(target);
            // 1.获取当前方法的缓存操作
            Collection<CacheOperation> operations = getCacheOperationSource().getCacheOperations(method, targetClass);
            if (!CollectionUtils.isEmpty(operations)) {
                // 2.执行缓存操作
                return execute(invoker, method, new CacheOperationContexts(operations, method, args, target, targetClass));
            }
        }
 
        return invoker.invoke();
    }

* getCacheOperationSource().getCacheOperations(method, targetClass)获取当前方法的缓存操作

    默认实现类为AbstractFallbackCacheOperationSource

// AbstractFallbackCacheOperationSource.getCacheOperations(Method method, Class<?> targetClass)
    public Collection<CacheOperation> getCacheOperations(Method method, Class<?> targetClass) {
        if (method.getDeclaringClass() == Object.class) {
            return null;
        }
 
        Object cacheKey = getCacheKey(method, targetClass);
        Collection<CacheOperation> cached = this.attributeCache.get(cacheKey);
 
        if (cached != null) {
            return (cached != NULL_CACHING_ATTRIBUTE ? cached : null);
        }
        else {
            Collection<CacheOperation> cacheOps = computeCacheOperations(method, targetClass);
            if (cacheOps != null) {
                if (logger.isDebugEnabled()) {
                    logger.debug("Adding cacheable method '" + method.getName() + "' with attribute: " + cacheOps);
                }
                this.attributeCache.put(cacheKey, cacheOps);
            }
            else {
                this.attributeCache.put(cacheKey, NULL_CACHING_ATTRIBUTE);
            }
            return cacheOps;
        }
    }

   * 执行execute()方法（关于操作缓存细节笔者不再详细分析，读者可自行分析）

private Object execute(final CacheOperationInvoker invoker, Method method, CacheOperationContexts contexts) {
        // Special handling of synchronized invocation
        if (contexts.isSynchronized()) {
            CacheOperationContext context = contexts.get(CacheableOperation.class).iterator().next();
            if (isConditionPassing(context, CacheOperationExpressionEvaluator.NO_RESULT)) {
                Object key = generateKey(context, CacheOperationExpressionEvaluator.NO_RESULT);
                Cache cache = context.getCaches().iterator().next();
                try {
                    return wrapCacheValue(method, cache.get(key, new Callable<Object>() {
                        @Override
                        public Object call() throws Exception {
                            return unwrapReturnValue(invokeOperation(invoker));
                        }
                    }));
                }
                catch (Cache.ValueRetrievalException ex) {
                    // The invoker wraps any Throwable in a ThrowableWrapper instance so we
                    // can just make sure that one bubbles up the stack.
                    throw (CacheOperationInvoker.ThrowableWrapper) ex.getCause();
                }
            }
            else {
                // No caching required, only call the underlying method
                return invokeOperation(invoker);
            }
        }
 
 
        // Process any early evictions
        processCacheEvicts(contexts.get(CacheEvictOperation.class), true,
                CacheOperationExpressionEvaluator.NO_RESULT);
 
        // Check if we have a cached item matching the conditions
        Cache.ValueWrapper cacheHit = findCachedItem(contexts.get(CacheableOperation.class));
 
        // Collect puts from any @Cacheable miss, if no cached item is found
        List<CachePutRequest> cachePutRequests = new LinkedList<CachePutRequest>();
        if (cacheHit == null) {
            collectPutRequests(contexts.get(CacheableOperation.class),
                    CacheOperationExpressionEvaluator.NO_RESULT, cachePutRequests);
        }
 
        Object cacheValue;
        Object returnValue;
 
        if (cacheHit != null && cachePutRequests.isEmpty() && !hasCachePut(contexts)) {
            // If there are no put requests, just use the cache hit
            cacheValue = cacheHit.get();
            returnValue = wrapCacheValue(method, cacheValue);
        }
        else {
            // Invoke the method if we don't have a cache hit
            returnValue = invokeOperation(invoker);
            cacheValue = unwrapReturnValue(returnValue);
        }
 
        // Collect any explicit @CachePuts
        collectPutRequests(contexts.get(CachePutOperation.class), cacheValue, cachePutRequests);
 
        // Process any collected put requests, either from @CachePut or a @Cacheable miss
        for (CachePutRequest cachePutRequest : cachePutRequests) {
            cachePutRequest.apply(cacheValue);
        }
 
        // Process any late evictions
        processCacheEvicts(contexts.get(CacheEvictOperation.class), false, cacheValue);
 
        return returnValue;
    }

总结：

    缓存功能的实现实际也是通过Spring代理来实现的。生成当前类的代理类，调用代理类的invoke()方法，在invoke()方法中调用CacheInterceptor拦截器的execute()方法，拦截器会使用缓存器（本例中的SimpleCacheManager）来进行具体方法实现。

    重要操作流程如下：

    1）解析<cache:annotation-driven />，将InfrastructureAdvisorAutoProxyCreator注入到Spring容器中，该类的作用是在Spring创建bean实例的时候，会执行其postProcessAfterInitialization()方法，生成bean实例的代理类

    2）解析<cache:annotation-driven />，将BeanFactoryCacheOperationSourceAdvisor类注入到Spring容器中，该类的主要作用是作为一个Advisor添加到上述代理类中

    3）BeanFactoryCacheOperationSourceAdvisor类拥有对CacheInterceptor的依赖，CacheInterceptor作为一个方法拦截器，负责对缓存方法的拦截，

    4）当前类方法调用被拦截到CacheInterceptor后，CacheInterceptor会调用我们在配置文件中配置的CacheManager实现（也就是本例中的SimpleCacheManager），来真正实现缓存功能

原文链接：https://blog.csdn.net/qq_26323323/article/details/81700626