Only way i see is, storing the data from your project in a database
(MS-Project can do that with various databases but preferrably with
MS SQL Server) and access that database via
jdbc.
The table structure is fairly good understandable and i remember that
there was even documentation by Microsoft (gasp!).
Only thing i remember is (it's been some years) that the Unique IDs
this MS-Project Program of theirs produces, are a bit UnUnique
(read dupes) in some cases.
As for accessing the mpp file directly. Forget it. Unless you're not
too concerned about you mental wellbeing that is
J.