I saw an advertisement while perusing a technical magazine. It was for an object database created by InterSystems. The product was called Cache. What caught my eye was the claim that it had technology to persist Java objects with a relational mapper.
The object model for Cache is based on the Object Database Management Group (ODMG) standards. It works with C++ and .NET as well as Java. The marketing boasts 5x the speed of normal relational databases.
Cache is meant for Rich Internet Application development. It uses an application server. However there are multiple ways to make use of the object database. You can use templated classes. There are also lightweight API calls for direct database access. Finally there is the Jalapeno technology.
Jalapeno stands for JAva LAnguage PErsistence with NO mapping. You create your Plain Old Java Objects (POJO) first. Then you use Cache to generate a schema to work with those objects. Cache has a library class to deal with the database. You can apparently just focus on your POJOs, and Cache will do the rest like magic.