code: @RequestMapping(value="/{providerId}", method=RequestMethod.GET, params="oauth_token")
  	public RedirectView oauth1Callback(@PathVariable String providerId, NativeWebRequest request) {
  		try {
  			OAuth1ConnectionFactory<?> connectionFactory = (OAuth1ConnectionFactory<?>) connectionFactoryLocator.getConnectionFactory(providerId);
  			Connection<?> connection = connectSupport.completeConnection(connectionFactory, request);
  			addConnection(connection, connectionFactory, request);
  		} catch (Exception e) {
  			sessionStrategy.setAttribute(request, PROVIDER_ERROR_ATTRIBUTE, e);
  			logger.warn("Exception while handling OAuth1 callback (" + e.getMessage() + "). Redirecting to " + providerId +" connection status page.");
  		}
  		return connectionStatusRedirect(providerId, request);
  	}
docs: Process the authorization callback from an OAuth 1 service provider.
  Called after the user authorizes the connection, generally done by having he or she click "Allow" in their web browser at the provider's site.
  On authorization verification, connects the user's local account to the account they hold at the service provider
  Removes the request token from the session since it is no longer valid after the connection is established.
  @param providerId the provider ID to connect to
  @param request the request
  @return a RedirectView to the connection status page