how to add nested folders and files into the odt file structure ?

Hello everybody,
                I know the odt file is a kind of zip file. I would like to add folders and files in 
it programmatically, but I don't know how to proceed.
I tested manually with 7-zip, but at the end the odt file is corrupt. I tried with java ZipFile 
class, but it fails too. So I would like to know if a such API exists and where can I found example 
for it ?

The files I want to add won't be linked to the contents of the document, I just want use the odt 
file to store additional files like into a zip.

Regards,
--
Vincent LORENZO
01-69-08-17-24
CEA Saclay Nano-INNOV
Institut CARNOT CEA LIST
Point Courrier n° 174
91 191 Gif sur Yvette CEDEX