Some time ago I wrote a post covering a combination of Spring Data and MongoDB in action. That post was demonstrating how incredibly convenient and deadly simple the data persistence can be implemented with the combination of MongoDB and Spring Data. Thinking on this matter for a while, I released that my post was somewhat unfair in regards to the other ORMs compatible with MongoDB. After all, the concept of mapping domain objects into DB structures and vice versa does not belong to Spring Data exclusively and is widely known as ORM paradigm. Furthermore, unlike with RDBMSes where usage of ORM in your application is somewhat controversial and should be applied with caution, MongoDB already stores data as documents so it’s not a crime to simplify life of developers allowing to make data persistence as easy and as smooth as possible.
Long story short, I would like to introduce a list of ORMs which I know can work with MongoDB. I’m also going to partially cover some pros and cons of using each and the stage on which each project happened to be at the moment of writing. (The most viable options from my point of view will appear in the top of the list).
1) Spring Data for MongoDB is a project under Spring umbrella which is meant to simplify the development of Java applications for Mongo. Key features are a seamless integration with Spring Framework, dynamic repository facility for rapid development, a complete ORM solution(unlike Spring JDBC Template), frequent releases and Spring community support.
2) Morphia is a very stable and feature-rich ORM designed explicitly for MongoDB. Has some nice documentation and google group filled with responses to a huge number of questions. Unfortunately the version on Google Code seems to be abandoned by the original author which means that the newest Mongo features are not going to appear in the ORM(like Aggregation Framework and some new query keywords).
There is fork of Morphia on GitHub – https://github.com/jmkgreen/morphia which has some activity around it. So hopefully this ORM can survive and evolve.
4) Here is also a number of JPA 2.0 providers which support MongoDB. EclipseLink, Kundera and DataNucleus to name a few. The major advantage in this case is that you can program to a familiar JPA interface/annotations, but on the other side you may not be able to do thing which require your code to be more “Mongo-specific”(e.g. specify WriteConcern etc.). For more details you should look in the documentation of each product. For people interested in examples I add a link with EclipseLink in action and a link about Kundera.
5) Hibernate OGM is the next framework in the list which is inspired by the popular Java ORM Hibernate. By the time of writing the latest version is 4.0.0.Beta2 and the development process seems to be somewhat stale(no activity for two months). A post showing it in action can be found by the following link. But until the version gets more stable I wouldn’t suggest using it seriously.
6) And there is also MJORM which lacks documentation(at least at Google Code) but can also be considered as an alternative. Its most interesting feature is a query language similar to SQL.
As far as you can see there is a number of alternatives you can choose between, but the best option should always be chosen depending on your business requirements, available time and familiarity with certain technologies. Good luck!