public String getPrincipalName() {
    return principalName;
  }
AmbariProxyUserKerberosDetailsImpl is a {@link AmbariProxyUserDetailsImpl} implementation that
adds allows for the proxy user's principal name to be retrieved if the proxy user authenticated
using Kerberos.
ambari-server/src/main/java/org/apache/ambari/server/security/authentication/kerberos/AmbariProxyUserKerberosDetailsImpl.java