what do you mean by "changes in the old world" ?
If the database layout stays the same, just create your mapping that
matches the current database and develop in parallel.
If not, you have to work closely together with the other developers,
so they don't interfere with your
work.
as you use a web-ui and a swing ui, I suggest going with this approach
UI-Frontends (MVC)
Service Layer
DB-Layer
Databse