一次排查@CacheEvict注解失效的经历
笔者简单看了一下《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。
下面是笔者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。
总结：
笔者还是太大意了，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是笔者使用不当引出的，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);