private Map<String, Map<Class<?>, Collection<Permission>>> permissionData = Maps.newHashMap();
@Override
public void createUser(String username) throws UserExistsException {
if (credentialsData.containsKey(username)) {
throw new UserExistsException("user exists");
}
credentialsData.put(username, new HashMap<String, String>());
permissionData.put(username, new HashMap<Class<?>, Collection<Permission>>());
}