code: public Response handle(String accessToken) throws WebApplicationException
      {
          // If an access token is not available.
          if (accessToken == null)
          {
              // Return "400 Bad Request".
              return ResponseUtil.bearerError(
                      Status.BAD_REQUEST, CHALLENGE_ON_MISSING_ACCESS_TOKEN);
          }
  
          try
          {
              // Process the userinfo request with the access token.
              return process(accessToken);
          }
          catch (WebApplicationException e)
          {
              throw e;
          }
          catch (Throwable t)
          {
              // Unexpected error.
              throw unexpected("Unexpected error in UserInfoRequestHandler", t);
          }
      }
docs: Handle a userinfo request to a <a href=
  "http://openid.net/specs/openid-connect-core-1_0.html#UserInfo"
  >UserInfo Endpoint</a> defined in <a href=
  "http://openid.net/specs/openid-connect-core-1_0.html">OpenID Connect
  Core 1&#x002E;0</a>.
  
  @param accessToken
  An access token.
  
  @return
  A response that should be returned from the endpoint to the
  client application.
  
  @throws WebApplicationException
  An error occurred.