springboot Optimize SystemEnvironmentPropertyMapper

Hi,

I just noticed a couple of minor performance tweaks in SystemEnvironmentPropertyMapper. The biggest one is probably to avoid creating ConfigurationPropertyName instances twice for every isAncestorOf check (once for the normal of() call and once for the isValid() check).

Cheers, Christoph

Comment From: philwebb

Thanks once again @dreis2211! I split this up into a few smaller commits and also added a new method to ConfigurationPropertyName to save needing to throw/catch the exception.