SLING-12642 cache privileges and principals in the context of the invoking Jackrabbit Session

[joerghoh]

In the AclUtil there are many occassions where privileges and principals are resolved over and over again (probably many times the same).

In order to remove the redundant retrieval I added CachingSesssionWrapper which is passed instead of the session; by default the wrapped session is used, but the following 2 functionalities are executed in an optimized way by the CachingSessionWrapper:

• privilegesFromNames (convert the privilege names into privilege objects)
• expandPrivilege ( to expand aggregated privileges into the contained privileges)
• getPrincipal ( to retrieve a principal for a given principal name)

All these results are cached within the CachingSessionWrapper. As this object shares the same lifetime as the session object itself, and as the results are immutable, it's safe to do so.

Note: getPrincipal is safe here, as no principals are removed here.

For review I advise to review commit by commit.

[anchela]

hi @joerghoh , i worked a bit on the patch replacing the manual privilege handling with privilegecollection.
the patch looks good to me otherwise.