一次排查@CacheEvict注解失效的经历及解决
目录
- 排查@CacheEvict注解失效
- 下面是我通过源码跟踪排查问题的过程
- 小结一下
- 说说spring全家桶中@CacheEvict无效情况
- 举个例子
排查@CacheEvict注解失效
我简单看了一下《Spring实战》中的demo,然后就应用到业务代码中了,本以为如此简单的事情,竟然在代码提交后的1个周,被同事发现。selectByTaskId()方法查出来的数据总是过时的。
代码如下:
@Cacheable("taskParamsCache") List<TaskParams> selectByTaskId(Long taskId); // ... // ... @CacheEvict("taskParamsCache") int deleteByTaskId(Long taskId);
想要的效果是当程序调用selectByTaskId()方法时,把结果缓存下来,然后在调用deleteByTaskId()方法时,将缓存清空。
经过数据库数据对比之后,把问题排查的方向定位在@CacheEvict注解失效了。
下面是我通过源码跟踪排查问题的过程
在deleteByTaskId()方法的调用出打断点,跟进代码到spring生成的代理层。
@Override @Nullable public Object intercept(Object proxy, Method method, Object[] args, MethodProxy methodProxy) throws Throwable { Object oldProxy = null; boolean setProxyContext = false; Object target = null; TargetSource targetSource = this.advised.getTargetSource(); try { if (this.advised.exposeProxy) { // Make invocation available if necessary. oldProxy = AopContext.setCurrentProxy(proxy); setProxyContext = true; } // Get as late as possible to minimize the time we "own" the target, in case it comes from a pool... target = targetSource.getTarget(); Class<?> targetClass = (target != null ? target.getClass() : null); List<Object> chain = this.advised.getInterceptorsAndDynamicInterceptionAdvice(method, targetClass); Object retVal; // Check whether we only have one InvokerInterceptor: that is, // no real advice, but just reflective invocation of the target. if (chain.isEmpty() && Modifier.isPublic(method.getModifiers())) { // 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. Object[] argsToUse = AopProxyUtils.adaptArgumentsIfNecessary(method, args); retVal = methodProxy.invoke(target, argsToUse); } else { // We need to create a method invocation... retVal = new CglibMethodInvocation(proxy, target, method, args, targetClass, chain, methodProxy).proceed(); } retVal = processReturnType(proxy, target, method, retVal); return retVal; } finally { if (target != null && !targetSource.isStatic()) { targetSource.releaseTarget(target); } if (setProxyContext) { // Restore old proxy. AopContext.setCurrentProxy(oldProxy); } } }
通过getInterceptorsAndDynamicInterceptionAdvice获取到当前方法的拦截器,里面包含了CacheIneterceptor,说明注解被spring检测到了。
进入CglibMethodInvocation(proxy, target, method, args, targetClass, chain, methodProxy).proceed()方法内部
org.springframework.aop.framework.ReflectiveMethodInvocation#proceed
@Override @Nullable public Object proceed() throws Throwable { // We start with an index of -1 and increment early. if (this.currentInterceptorIndex == this.interceptorsAndDynamicMethodMatchers.size() - 1) { return invokeJoinpoint(); } Object interceptorOrInterceptionAdvice = this.interceptorsAndDynamicMethodMatchers.get(++this.currentInterceptorIndex); if (interceptorOrInterceptionAdvice instanceof InterceptorAndDynamicMethodMatcher) { // Evaluate dynamic method matcher here: static part will already have // been evaluated and found to match. InterceptorAndDynamicMethodMatcher dm = (InterceptorAndDynamicMethodMatcher) interceptorOrInterceptionAdvice; if (dm.methodMatcher.matches(this.method, this.targetClass, this.arguments)) { return dm.interceptor.invoke(this); } else { // Dynamic matching failed. // Skip this interceptor and invoke the next in the chain. return proceed(); } } else { // It's an interceptor, so we just invoke it: The pointcut will have // been evaluated statically before this object was constructed. return ((MethodInterceptor) interceptorOrInterceptionAdvice).invoke(this); } }
this.interceptorsAndDynamicMethodMatchers.get(++this.currentInterceptorIndex)方法取第一个拦截器,正是我们要关注的CacheIneterceptor,然后调用((MethodInterceptor) interceptorOrInterceptionAdvice).invoke(this)方法,继续跟进
org.springframework.cache.interceptor.CacheInterceptor#invoke
@Override @Nullable public Object invoke(final MethodInvocation invocation) throws Throwable { Method method = invocation.getMethod(); CacheOperationInvoker aopAllianceInvoker = () -> { try { return invocation.proceed(); } catch (Throwable ex) { throw new CacheOperationInvoker.ThrowableWrapper(ex); } }; try { return execute(aopAllianceInvoker, invocation.getThis(), method, invocation.getArguments()); } catch (CacheOperationInvoker.ThrowableWrapper th) { throw th.getOriginal(); } }
进入execute方法
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); CacheOperationSource cacheOperationSource = getCacheOperationSource(); if (cacheOperationSource != null) { Collection<CacheOperation> operations = cacheOperationSource.getCacheOperations(method, targetClass); if (!CollectionUtils.isEmpty(operations)) { return execute(invoker, method, new CacheOperationContexts(operations, method, args, target, targetClass)); } } } return invoker.invoke(); }
cacheOperationSource记录系统中所有使用了缓存的方法,cacheOperationSource.getCacheOperations(method, targetClass)能获取deleteByTaskId()方法缓存元数据,然后执行execute()方法
@Nullable 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, () -> 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<>(); 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; }
这里大致过程是:
先执行beforInvokeEvict ---- 执行数据库delete操作 --- 执行CachePut操作 ---- 执行afterInvokeEvict
我们的注解是方法调用后再使缓存失效,直接所以有效的操作应在倒数第2行
private void performCacheEvict( CacheOperationContext context, CacheEvictOperation operation, @Nullable Object result) { Object key = null; for (Cache cache : context.getCaches()) { if (operation.isCacheWide()) { logInvalidating(context, operation, null); doClear(cache); } else { if (key == null) { key = generateKey(context, result); } logInvalidating(context, operation, key); doEvict(cache, key); } } }
这里通过context.getCaches()获取到name为taskParamsCache的缓存
然后generateKey生成key,注意这里,发现生成的key是com.xxx.xxx.atomic.impl.xxxxdeleteByTaskId982,但是缓存中的key却是com.xxx.xxx.atomic.impl.xxxxselectByTaskId982,下面调用的doEvict(cache, key)方法不再跟进了,就是从cache中移除key对应值。明显这里key对应不上的,这也是导致@CacheEvict没有生效的原因。
小结一下
我还是太大意了,当时看了注解@CacheEvict的对key的注释:
大意就是如果没有指定key,那就会使用方法所有参数生成一个key,明显com.xxx.xxx.atomic.impl.xxxxselectByTaskId982是方法名 + 参数,可是你没说把方法名还加上了啊,说好的只用参数呢,哈哈,这个bug是我使用不当引出的,很多人不会犯这种低级错误。
解决办法就是使用SpEL明确定义key
@Cacheable(value = "taskParamsCache", key = "#taskId") List<TaskParams> selectByTaskId(Long taskId); // ... // ... @CacheEvict(value = "taskParamsCache", key = "#taskId") int deleteByTaskId(Long taskId);
说说spring全家桶中@CacheEvict无效情况
@CacheEvict(value =“test”, allEntries = true)
1、使用@CacheEvict注解的方法必须是controller层直接调用,service里间接调用不生效。
2、原因是因为key值跟你查询方法的key值不统一,所以导致缓存并没有清除
3、把@CacheEvict的方法和@Cache的方法放到一个java文件中写,他俩在两个java文件的话,会导致@CacheEvict失效。
4、返回值必须设置为void
It is important to note that void methods can be used with @CacheEvict
5、@CacheEvict必须作用在走代理的方法上
在使用Spring @CacheEvict注解的时候,要注意,如果类A的方法f1()被标注了 @CacheEvict注解,那么当类A的其他方法,例如:f2(),去直接调用f1()的时候, @CacheEvict是不起作用的,原因是 @CacheEvict是基于Spring AOP代理类,f2()属于内部方法,直接调用f1()时,是不走代理的。
举个例子
不生效:
@Override public void saveEntity(Menu menu) { try { mapper.insert(menu); //Cacheable 不生效 this.test(); }catch(Exception e){ e.printStackTrace(); } } @CacheEvict(value = "test" , allEntries = true) public void test() { }
正确使用:
@Override @CacheEvict(value = "test" , allEntries = true) public void saveEntity(Menu menu) { try { mapper.insert(menu); }catch(Exception e){ e.printStackTrace(); } }
以上为个人经验,希望能给大家一个参考,也希望大家多多支持我们。