Current Situation

The predefined ReadPreferences in TaggableReadPreference (NearestReadPreference, SecondaryPreferredReadPreference, SecondaryReadPreference) are package protected.

A developer wanting to create a new ReadPreference cannot easily extend from one of the already available ones, and it has to, either duplicate code, or to create the new ReadPreference in a com.mongodb package.

Desired Behaviour

If the predefined ReadPreferences would be public, we could easily create new ones by extending them.

Real Example

In our case, we would like to create a ReadPreference that chooses one secondary node that does not have a special tag defined. This is currently not possible with the current predefined ReadPreferences, but would be very easy by extending the SecondaryPreferredReadPreference one.