code: @Nonnull
    private static ClientCertificateValidationResult _checkClientCertificate (@Nonnull final HttpServletRequest aHttpServletRequest,
                                                                              @Nonnull final String sLogPrefix)
    {
      try
      {
        return ClientCertificateValidator.verifyClientCertificate (aHttpServletRequest, sLogPrefix);
      }
      catch (final RuntimeException ex)
      {
        if (LOGGER.isWarnEnabled ())
          LOGGER.warn (sLogPrefix + "Error validating client certificate", ex);
      }
      return ClientCertificateValidationResult.createFailure ();
    }
docs: Check if the current request contains a client certificate and whether it
  is valid.
  
  @param aHttpServletRequest
  The current servlet request. May not be <code>null</code>.
  @param sLogPrefix
  The context - for logging only. May not be <code>null</code>.
  @return The validation result