Spring cacheable - filter out empty collections using SpEL

Question

I wanted to know is there a way to use SpEL in order to filter out values like empty collections.

My cache currently filters out null values:

  @Cacheable(value = "groupIdToGroupNames",unless = "#result == null")
   public Map<Long, Collection<String>> findAllBySearchCustomerKey(final long groupId) {
    return idToNameClient.findAllGroupMembersById(groupId);
   } 

I'm trying to find a way to filter out the groups that are of size 0 but not null. Is there a way of doing that by using params for @Cacheable?

Any help would be much appreciated.

Solution 1

Something like this

unless = "#result==null or #result.size()==0"

Solution 2

unless = "#result==null or #result.isEmpty()" works for me.

Comments

[user2512231]

I just added it. Newbe to SpEL:) Thanks!

[nvoigt]

This does not seem to add anything new over the accepted 5 year old answer. It will probably be deleted by reviewers. If you think your answer makes a significant difference, you may want to add an explanation on how this is better than the existing answers.

[SUMIT]

probably this was more readable to me instead of #result.size()==0. Also agree with @nvoigt that we should add explanation over any answer.

[Brad Parks]

adds plenty! a method isEmpty may end up doing something more than a simple check, and is worth it for readability as well