Simple key generator. Returns the parameter itself if a single non-null value is given, otherwise returns a {@link SimpleKey} of the parameters.
Unlike {@link DefaultKeyGenerator}, no collisions will occur with the keys generated by this class. The returned {@link SimpleKey} object can be safelyused with a {@link org.springframework.cache.concurrent.ConcurrentMapCache}, however, might not be suitable for all {@link org.springframework.cache.Cache}implementations.
@author Phillip Webb
@author Juergen Hoeller
@since 4.0
@see SimpleKey
@see DefaultKeyGenerator
@see org.springframework.cache.annotation.CachingConfigurer