public class SampleRealmIdentity implements RealmIdentity {

    private final Principal principal;
    private final String password;
    private final Set<String> roles;

    public SampleRealmIdentity(Principal principal, String password, Set<String> roles) {
        this.principal = principal;
        this.password = password;
        this.roles = roles;
    }
 ... 
 
    @Override
    public <C extends Credential> C getCredential(Class<C> credentialType) throws RealmUnavailableException {
       // do not return credentials
       return null;
    }

    @Override
    public boolean verifyEvidence(Evidence evidence) throws RealmUnavailableException {
       if (evidence instanceof PasswordGuessEvidence) {
          PasswordGuessEvidence guess = (PasswordGuessEvidence) evidence;
          return Arrays.equals(password.toCharArray(), guess.getGuess());
       }
       return false;
    }
   ...
}

    @Override
    public AuthorizationIdentity getAuthorizationIdentity() throws RealmUnavailableException {
       return AuthorizationIdentity.basicIdentity(getAttributes());
    }
}