The Java examples rely on an auth file created via the Authorization example. Which in turn requires building this code, and running a web browser...
String authorizeUrl = webAuth.authorize(webAuthRequest);
System.out.println("1. Go to " + authorizeUrl);
System.out.println("2. Click \"Allow\" (you might have to log in first).");
System.out.println("3. Copy the authorization code.");
System.out.print("Enter the authorization code here: ");
Now, I can get an auth code for me from DropBox directly, but the DbxAuthInfo structure also requires a non-NULL host. And has no documentation about that. This example doesn't have it either; the user and secret are submitted and the auth code retrieved.
Re: Authorization requires web browser even for dev?
Well that was challenging. That worked but it took a while to realize it. Even though I'd removed the old Dropbox and Jackson (?) JARs from my libraries list, the Jackson one was still in the /lib folder and therefore was apparently being found before the newer Jackson-core (which was also there), resulting in java.lang.NoSuchFieldError: DEFAULT java.lang.reflect.InvocationTargetException and so on.