Custom Login Module Break COTS J2EE Application

Question

I'm using a custom login module to authenticate users of a COTS J2EE application. The authentication works like a charm, but the COTS app breaks because it uses request.getRemoteUser() to obtain the user name for database lookups.
When the custom login is in use, request.getRemoteUser() returns "[JAZNUserAdaptor: user=theuser]" instead of simply the user name (this differs from the standard XML provider, which returns only the user name).
I used the sample login module from the Oracle documentation almost verbatim, the method is included below.
Does anyone know why getRemoteUser() returns "[JAZNUserAdaptor: user=theuser]" and not just the user name? And how to make it stop doing that?
Thanks in advance... any input is is greatly appreciated, of course.
     public boolean login() throws LoginException {
               throw new LoginException("Error: no CallbackHandler available "
                         + "to garner authentication information from the user");
          // Setup default callback handlers.
          Callback[] callbacks = new Callback[] { new NameCallback("Username: "),
                    new PasswordCallback("Password: ", false) };
          try {
               _callbackHandler.handle(callbacks);
          } catch (Exception e) {
               _succeeded = false;
               throw new LoginException(e.getMessage());
          String username = ((NameCallback) callbacks[0]).getName();
          String password = new String(((PasswordCallback) callbacks[1]).getPassword());
          if (isValidUser(username, password)) {
               _succeeded = true;
               _password = password.toCharArray();
               _name = username;
     _authPrincipals = new CMPrincipal[2];
     authPrincipals[0] = new CMPrincipal(name);
     _authPrincipals[1] = new CMPrincipal("SecurityRole");
          ((PasswordCallback) callbacks[1]).clearPassword();
          callbacks[0] = null;
          callbacks[1] = null;
          if (!_succeeded) {
               System.out.println("login did not succeed... throwing LoginException...");
               throw new LoginException("Authentication failed: Password does not match");
          return true;
     }

Answer 1

I know getUserPrincipal().getName() works, but since the J2EE application is a COTS product, I can't change the source code. I'm trying to get the vendor to make that change and release a patch. I was looking for something I might be able to do on my end to get the code to work.
Thanks for the help.