code: public DecoratedUserContext getUserContext(String authProviderIdentifier)
              throws GuacamoleException {
  
          // Locate and return the UserContext associated with the
          // AuthenticationProvider having the given identifier, if any
          for (DecoratedUserContext userContext : getUserContexts()) {
  
              // Get AuthenticationProvider associated with current UserContext
              AuthenticationProvider authProvider = userContext.getAuthenticationProvider();
  
              // If AuthenticationProvider identifier matches, done
              if (authProvider.getIdentifier().equals(authProviderIdentifier))
                  return userContext;
  
          }
  
          throw new GuacamoleResourceNotFoundException("Session not associated "
                  + "with authentication provider \"" + authProviderIdentifier + "\".");
  
  
      }
docs: Returns the UserContext associated with this session that originated
  from the AuthenticationProvider with the given identifier. If no such
  UserContext exists, an exception is thrown.
  
  @param authProviderIdentifier
  The unique identifier of the AuthenticationProvider that created the
  UserContext being retrieved.
  
  @return
  The UserContext that was created by the AuthenticationProvider
  having the given identifier.
  
  @throws GuacamoleException
  If no such UserContext exists.