问题
I want to store data into the Cache using EhCache, but if I try to access the data before data has been populated into the Cache, I get NULL POINTER exception. How can I make sure that Data is not read from the cache until and unless data has been stored into the Cache?
回答1:
What you are requesting will make cache usage very problematic.
If you always block on a missing entry, any eviction or expiry will put you in the same situation as having an empty cache / missing mapping.
However, using cache-through might be a better way to look at the problem. It would leave the loading of the mapping to the cache itself making sure you never get a null result (unless that key does not exist in the backing store).
See documentation for more information on that option.
来源：https://stackoverflow.com/questions/45490306/how-to-make-sure-that-no-one-reads-from-ehcache-object-while-data-is-being-writ