In addition to MongoDB's built in Java driver, Jongo, Morphia and Spring Data are all popular third-party solutions that make it easier to view and manipulate data in MongoDB. InsaneProgramming blogger Lieven Doclo offers a to-the-point MongoDB Java comparison using a REST-based service as a use case. From his notes:
MongoDB Java driver
The most low-level approach for accessing a MongoDB database from the JVM. The least user friendly but possibly the most versatile of the solutions; "there’s nothing you can’t do with the Java driver."
Handy for getting started with MongoDB if you are familiar with the shell commands and want to avoid manual mapping. Downsides: you need to know the exact syntax of the MongoDB shell API and there is no code completion queries or commands.
Fared worst due to its lack of support for the geoNear query and minimal built-in support for geo objects.