MongodbSerializer unnecessarily calls getKeyForPath(…)

[odrotbohm]

As stated in a Spring Data forum post MongodbSerializer recursively calls visit(…) for any() path types passing an empty expression to the call. This results in getKeyForPath(…) being called with an empty expression which is actually not necessary as looking up a key for no expression hardly makes sense. Beyond that, potential subclasses have to deal with that case explicitly which complicates the implementation.

Long story short, the call to getKeyForPath(…) can be delayed into the else clause, avoiding that obsolete call.

[timowest]

released in 2.3.1