Exception when one key has no value in Cache.getAll

Cache interface was designed to throw an exception in the case of null or empty values. While this seems a reasonable behavior for Cache.get, I didn’t figured out how to deal when calling Cache.getAll.

I/O is expensive, so I collect all data I need at once using Cache.getAll. In the case that at least one key has no value, it throws an exception, which does not allow me to access the other valid values.

I found to options: first, using Cache.get instead of Cache.getAll; second, including null values as Optional. Both options are terrible considering performance. Is there a recommended solution to deal with this scenario? Otherwise, if possible, how could I help to improve the Cache API in this issue?

[ben-manes]

@Maaartinus That could have a race due to an eviction, for whatever reason. It tiny improvement would be to throw a custom exception with the results and then use cache.putAll to insert them. Then the results would be cached and the found set returned.

[lowasser]

I’m not sure why you consider Optional “terrible considering performance.” Relative to almost any I/O operation, I’d expect the boxing incurred by Optional is going to be relatively minor. I’d expect that to be the appropriate solution in most cases.

Do you have performance data – perhaps from CacheStats – suggesting otherwise?