ExtremeB is an object database that is written and compiled using C and C++ and that is used as an embeded database for embeded applications. The most impressive thing about ExtremeDB is that it provides a Java Native Inteface JNI in which you can use 9 created annotations to create the schema of your embeded database at runtime using java reflection.
The biggest advantage is that there will be no discripancy between the java code and the database definition since the definition is drived from the code itself. In addition the database provided the power and performance of C and C++ which greatly overcome Java performance for such applications.
http://www.mcobject.com/extremedb-jni
