Extend your aspect to enforce an authenticated user when @Authenticated methods or constructors are executed.

To model the authentication, we will present the user with an input dialog where he/she can select the role. (This is of course a simplification: in production, we would of course have to prompt for login and password and verify these against a password database.)

The code to manage the current role for the user and to present the authentication dialog is shown here:

import javax.swing.JOptionPane;
import figures.annotations.Authenticated;
 
public aspect AccessControl {
  ...
  Authenticated.Role role;
 
  public void authenticate() {
    role = (Authenticated.Role)
      JOptionPane.showInputDialog(null,
        "Select role", "Input",
        JOptionPane.INFORMATION_MESSAGE, null,
        Authenticated.Role.values(), role);
  }
  ...
}

As long as the user is not authenticated, we keep presenting him the authentication dialog. In other words, the actual access control check can be as simple as:

while(role == null)
  authenticate();

After implementing the aspect, run the figure editor. You should be presented with the authentication dialog upon drawing the first point. Afterwards, new points can be added without interruption.

Continue with Exercise 3.