Hi Julien,
You should have a look at the Moose platform: http://moosetechnology.org http://moosetechnology.org/ Moose is made exactly to analyze software, and has more then 15 years of engineering. Roassal is a component of Moose.
To analyze some Java, you need a tool to translate your .java files into a big .mse file. MSE is a meta-model that is accepted by Moose. As far as I know, two tools are available for this: VerveineJ and inFamoos(? I cannot remember the exact name).
VerveineJ is unfortunately not free. Ask directly in the Moose mailing list for this. However, I have a copy of it. I can generate the .MSE file if you give me access to the Java code.
Cheers, Alexandre