How do I tell Spring cache not to cache null value in @Cacheable annotation

Is there a way to specify that if the method returns null value, then don't cache the result in @Cacheable annotation for a method like this?

@Cacheable(value="defaultCache", key="#pk")
public Person findPerson(int pk) {
return getSession.getPerson(pk);
}

Update:
here is the JIRA issue submitted regarding caching null value last November, which hasn't resolved yet:
[\[#SPR-8871\] @Cachable condition should allow referencing return value - Spring Projects Issue Tracker][1]


[1]:

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**update** this answer is outdated now, for Spring 3.2 and later see Tech Trip's [answer](

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), OP: feel free to mark it as accepted.

I don't think that it's possible(even though there's conditional Cache eviction in Spring that can be executed after the method invocation with `@CacheEvict` parameter *beforeInvocation* set to false, which is default value) examining the `CacheAspectSupport` class shows that the returned value is not stored anywhere before the `inspectAfterCacheEvicts(ops.get(EVICT));` call.


protected Object execute(Invoker 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) {
return invoker.invoke();
}

// get backing class
Class<?> targetClass = AopProxyUtils.ultimateTargetClass(target);
if (targetClass == null && target != null) {
targetClass = target.getClass();
}
final Collection<CacheOperation> cacheOp = getCacheOperationSource().getCacheOperations(method, targetClass);

// analyze caching information
if (!CollectionUtils.isEmpty(cacheOp)) {
Map<String, Collection<CacheOperationContext>> ops = createOperationContext(cacheOp, method, args, target, targetClass);

// start with evictions
inspectBeforeCacheEvicts(ops.get(EVICT));

// follow up with cacheable
CacheStatus status = inspectCacheables(ops.get(CACHEABLE));

Object retVal = null;
Map<CacheOperationContext, Object> updates = inspectCacheUpdates(ops.get(UPDATE));

if (status != null) {
if (status.updateRequired) {
updates.putAll(status.cUpdates);
}
// return cached object
else {
return status.retVal;
}
}

retVal = invoker.invoke();

inspectAfterCacheEvicts(ops.get(EVICT));

if (!updates.isEmpty()) {
update(updates, retVal);
}

return retVal;
}

return invoker.invoke();
}

If Spring annotation

@Cacheable(value="defaultCache", key="#pk",unless="#result!=null")

does not work ,you can try:

@CachePut(value="defaultCache", key="#pk",unless="#result==null")

It works for me.

Hooray, as of Spring 3.2 the framework allows for this using Spring SpEL and `unless`. Note from the java doc for [`Cacheable` element `unless`][1]:

> Spring Expression Language (SpEL) expression used to veto method caching. Veto caching the result if the condition evaluates to true.
>
> Unlike condition(), this expression is evaluated after the method has been called and can therefore refer to the result. Default is "", meaning that caching is never vetoed.

The important aspect is that `unless` is evaluated after the method has been called. This makes perfect sense because the method will never get executed if the key is already in the cache.

So in the above example you would simply annotate as follows (#result is available to test the return value of a method):

@Cacheable(value="defaultCache", key="#pk", unless="#result == null")
public Person findPerson(int pk) {
return getSession.getPerson(pk);
}

I would imagine this condition arises from the use of pluggable cache implementations such as Ehcache which allows caching of nulls. Depending on your use case scenario this may or may not be desirable.


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