Returns a single Subject's principals retrieved from all configured Realms as a Set, or an empty Set if there
are not any principals.
<p/>
Note that this will return an empty Set if the 'owning' subject has not yet logged in.
@return a single Subject's principals retrieved from all configured Realms as a Set.
Returns a single Subject's principals retrieved from all configured Realms as a Set, or an empty Set if there are not any principals. <p/> Note that this will return an empty Set if the 'owning' subject has not yet logged in.
@return a single Subject's principals retrieved from all configured Realms as a Set.