使用spring cache让我的接口性能瞬间提升了100倍( 三 ) _spring

哈哈哈，这个类里面定义了AOP的三大要素：advisor、interceptor和Pointcut，只是Pointcut是在BeanFactoryCacheOperationSourceAdvisor内部定义的。

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另外定义了CacheOperationSource类，该类封装了cache方法签名注解的解析工作，形成CacheOperation的集合。它的构造方法会实例化SpringCacheAnnotationParser，现在看看这个类的parseCacheAnnotations方法。

private Collection<CacheOperation> parseCacheAnnotations(DefaultCacheConfig cachingConfig, AnnotatedElement ae, boolean localOnly) {Collection<CacheOperation> ops = null;//找@cacheable注解方法Collection<Cacheable> cacheables = (localOnly ? AnnotatedElementUtils.getAllMergedAnnotations(ae, Cacheable.class) :AnnotatedElementUtils.findAllMergedAnnotations(ae, Cacheable.class));if (!cacheables.isEmpty()) {ops = lazyInit(null);for (Cacheable cacheable : cacheables) {ops.add(parseCacheableAnnotation(ae, cachingConfig, cacheable));}}//找@cacheEvict注解的方法Collection<CacheEvict> evicts = (localOnly ? AnnotatedElementUtils.getAllMergedAnnotations(ae, CacheEvict.class) :AnnotatedElementUtils.findAllMergedAnnotations(ae, CacheEvict.class));if (!evicts.isEmpty()) {ops = lazyInit(ops);for (CacheEvict evict : evicts) {ops.add(parseEvictAnnotation(ae, cachingConfig, evict));}}//找@cachePut注解的方法Collection<CachePut> puts = (localOnly ? AnnotatedElementUtils.getAllMergedAnnotations(ae, CachePut.class) :AnnotatedElementUtils.findAllMergedAnnotations(ae, CachePut.class));if (!puts.isEmpty()) {ops = lazyInit(ops);for (CachePut put : puts) {ops.add(parsePutAnnotation(ae, cachingConfig, put));}} //找@Caching注解的方法Collection<Caching> cachings = (localOnly ? AnnotatedElementUtils.getAllMergedAnnotations(ae, Caching.class) :AnnotatedElementUtils.findAllMergedAnnotations(ae, Caching.class));if (!cachings.isEmpty()) {ops = lazyInit(ops);for (Caching caching : cachings) {Collection<CacheOperation> cachingOps = parseCachingAnnotation(ae, cachingConfig, caching);if (cachingOps != null) {ops.addAll(cachingOps);}}}return ops;}

我们看到这个类会解析@cacheable、@cacheEvict、@cachePut 和 @Caching注解的参数，封装到CacheOperation集合中。

此外，spring cache 功能的关键就是上面的拦截器：CacheInterceptor，它最终会调到这个方法：

@Nullableprivate Object execute(final CacheOperationInvoker invoker, Method method, CacheOperationContexts contexts) {// Special handling of synchronized invocationif (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, () -> 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 methodreturn invokeOperation(invoker);}}// 执行@CacheEvict的逻辑，这里是当beforeInvocation为true时清缓存processCacheEvicts(contexts.get(CacheEvictOperation.class), true,CacheOperationExpressionEvaluator.NO_RESULT);// 获取命中的缓存对象Cache.ValueWrapper cacheHit = findCachedItem(contexts.get(CacheableOperation.class));//如果没有命中，则生成一个put的请求List<CachePutRequest> cachePutRequests = new LinkedList<>();if (cacheHit == null) {collectPutRequests(contexts.get(CacheableOperation.class),CacheOperationExpressionEvaluator.NO_RESULT, cachePutRequests);}Object cacheValue;Object returnValue;if (cacheHit != null && !hasCachePut(contexts)) {// If there are no put requests, just use the cache hitcacheValue = https://www.isolves.com/it/cxkf/kj/2020-09-27/cacheHit.get();returnValue = wrapCacheValue(method, cacheValue);}else {// 如果没有获得缓存对象，则调用业务方法获得返回对象，这是关键代码returnValue = invokeOperation(invoker);cacheValue = unwrapReturnValue(returnValue);}// 收集@CachePuts数据collectPutRequests(contexts.get(CachePutOperation.class), cacheValue, cachePutRequests);// 执行cachePut或没有命中的Cacheable请求，将返回对象放到缓存中for (CachePutRequest cachePutRequest : cachePutRequests) {cachePutRequest.apply(cacheValue);}// 执行@CacheEvict的逻辑，这里是当beforeInvocation为false时清缓存processCacheEvicts(contexts.get(CacheEvictOperation.class), false, cacheValue);return returnValue;}

也行有些朋友看到这里会有一个疑问：

既然spring cache的增删改查都有了，为啥还要 @Caching 注解呢？