I think using jpct for drawing 2d raster map and some vector data over it (if I understand correctly your needs) is overkill. Basicly, at any moment, you have position, rotation and scale of the map, right? So, assuming you stick to the standard Java MVC pattern you need to design and implement:
1. MODEL - a way to load and represent vector data (doesn't matter if it comes from AutoCad or from some other source) over raster data
2. VIEW - a way to display data in it's current state (position, rotation, scale)
3. CONTROLLER - a way to interact with the user and let him change position, scale, rotation
A site with many java GIS projects with source for inspiration:
http://opensourcegis.org/
On the other hand jpct can display textured planes (scaled and rotated raster data) and wireframe meshes (scaled and rotated vector data)... out of ideas here, but hope I helped a little
1. MODEL - a way to load and represent vector data (doesn't matter if it comes from AutoCad or from some other source) over raster data
2. VIEW - a way to display data in it's current state (position, rotation, scale)
3. CONTROLLER - a way to interact with the user and let him change position, scale, rotation
A site with many java GIS projects with source for inspiration:
http://opensourcegis.org/
On the other hand jpct can display textured planes (scaled and rotated raster data) and wireframe meshes (scaled and rotated vector data)... out of ideas here, but hope I helped a little