@Override
  public void init(FilterConfig filterConfig) throws ServletException {
    realm = getParameterValue(filterConfig, REALM_PARAM, DEFAULT_REALM);
  }
Constructor.

@param entryPoint       the authentication entrypoint
@param configuration    the Ambari configuration
@param users            Ambari user access
@param auditLogger      the Audit logger
@param permissionHelper the permission helper
ambari-server/src/main/java/org/apache/ambari/server/security/authorization/AmbariAuthorizationFilter.java