you can try this library: https://code.google.com/p/qood/
Here are some reasons to use it:
- lightweight: only 9 public interface/class to learn.
- query like SQL: support group-by, order-by, left join,
formula,...etc.
- for big data: use File(QFS) instead of Heap Memory.
- try to solve Object-relational impedance mismatch.