DataNucleus "MongoDB" provides persistence of Java objects to MongoDB datastores. It builds on top of the DataNucleus "core" jar supporting specific features of MongoDN datastores. It provides querying capabilities using JDOQL/JPQL. The code can be utilised with either JDO or JPA persistence APIs.
Support for this persistence layer is provided by way of a Forum at http://www.datanucleus.org.