I didn't know any Java client that supported generators (fetching properties from articles listed by list query in a single request). JWBF [only recently] (https://github.com/eldur/jwbf/issues/21) got the ability to query more than 1 page at a time.
When Wikipedia sites are real Big Data it is just a show stopper. Fetching information about Wiki Loves Monuments uploads in such ineffective way will take almost a day even for one country, when could be done in several minutes otherwise in batches.
This library uses Scala Futures for easy job parallelization.