Introduction
After searching for an easy and lightweight platform for object persistence and haven’t found what I wanted, I started my own platform that I called ‘lopf’ (lightweight object persistence platform).
Here is a brief project’s description, if you interested don’t hesitate to check source code (no binary release right now…) at orexio-lopf (SVN) or contact me.

Lightweight Object Persistence Platform
This platform is dedicated to that kind of application that doesn’t need RDMS but want an ‘on-demand’ access for data object.
Immediately we think about serialization but when you have a large number of objects, it’s take time to make an ‘on-demand’ access removing the need of loading the whole serialized object and all his child at the same time (whole in memory, ugly !).
The project simply includes a basic ‘Data’ object that you must extend in all objects that need to be persisted. After that you create what I call a ‘DataSource’ class (by extending corresponding lopf class) enabling you to define which data must be stored in this DataSource.
Then you can use the platform to read/write a set of objects from a ‘.jar’ file (or developer-defined extension).

I have too created a special Vector called ‘ContainerVector’ that enable you to store ‘Data’ object and then read it ‘on-demand’ without loading whole objects in memory.

Beta version planned for June. Don’t hesitate to join SourceForge project if interested.