code: public Response handle(
              MultivaluedMap<String, String> parameters, String authorization,
              String[] clientCertificatePath) throws WebApplicationException
      {
          // Convert the value of Authorization header (credentials of
          // the client application), if any, into BasicCredentials.
          BasicCredentials credentials = BasicCredentials.parse(authorization);
  
          // The credentials of the client application extracted from
          // 'Authorization' header. These may be null.
          String clientId     = credentials == null ? null : credentials.getUserId();
          String clientSecret = credentials == null ? null : credentials.getPassword();
  
          try
          {
              // Process the given parameters.
              return process(parameters, clientId, clientSecret, clientCertificatePath);
          }
          catch (WebApplicationException e)
          {
              throw e;
          }
          catch (Throwable t)
          {
              // Unexpected error.
              throw unexpected("Unexpected error in BackchannelAuthenticationRequest", t);
          }
      }
docs: Handle a backchannel authentication request to a backchannel authentication
  endpoint of CIBA (Client Initiated Backchannel Authentication).
  
  @param parameters
  Request parameters of a backchannel authentication request.
  
  @param authorization
  The value of {@code Authorization} header in the backchannel authentication
  request. A client application may embed its pair of client ID and
  client secret in a backchannel authentication request using <a href=
  "https://tools.ietf.org/html/rfc2617#section-2">Basic
  Authentication</a>.
  
  @param clientCertificatePath
  The path of the client's certificate, each in PEM format. The first
  item in the array is the client's certificate itself. May be {@code null}
  if the client did not send a certificate or path.
  
  @return
  A response that should be returned from the endpoint to the
  client application.
  
  @throws WebApplicationException
  An error occurred.