As of Spring Framework 4.3.RC1, the `Cache` interface has a new `<T> T get(Object key, Callable<T> valueLoader);` method (see SPR-9254).
If no entry for the given key is found, the `Callable` is invoked to compute/load the value that is then put into redis and returned. Additionally concurrent calls get synchronized so that the `Callable` is only called once.
Using Spring Framework 4.3 failures result in `o.s.c.Cache$ValueRetrievalException` prior versions use `RedisSystemException`.
Original pull request: #162.
1f97623a7c