DATANUCLEUS

Transparent persistence. Powerful querying. Use the API your prefer, to a very wide range of datastores. The most standards-compliant Java persistence product. Open Source software, under the Apache 2 license. Persisting Java objects is now easy... Providing access to industry leading RDBMS, map stores such as Cassandra and HBase, the Neo4j graph store, spreadsheets in Excel or OpenDocument formats, JSON formatted Amazon and Google Storage options, the popular MongoDB JSON-like document store, as well as ubiquitous LDAP and others... Java standard since 2006, providing easy persistence to RDBMS datastores. Comes with its own "SQL-like" JPQL query language, so you query your data in a language similar to what your datastore understands.