Generic Principal's getRoles returns empty array

Question

This is the code to create a Principal object.

List<String> roles = new ArrayList();
roles.add(userRole);
this.principal = new GenericPrincipal(username,"***********",roles);

When I printed the principal object, I got [username(userRole,)]

Getting the name from principal

GenericPrincipal principal = (GenericPrincipal)request.getUserPrincipal();
String name = principal.getName();

Getting the roles from principal

GenericPrincipal principal = (GenericPrincipal)request.getUserPrincipal();
String[] roles = principal.getRoles();

When I printed the principal object, I got [username()]

I'm able to get the name from Principal but not the roles. The length of roles[] is 0.

I even tried getPassword() method. It returns null. Only the getName() method works correctly.

Why is the roles array empty and How do I get the role correctly?