Ajax login redirection

Users often encounter situations when they want to perform an action on a web site and get redirected to login page. Application’s task is to take care of performing the requested action right after user’s successful log in. It is easy job, unless the action is requested via ajax.

Below I present a simple solution to this problem. Let me stress the word ’simple’, because I’m not 100% satisfied with this. It works fine, however, and I didn’t have time to think about something prettier.

Here’s users_controller.php file which defines login and ajax_login actions. The former one is supposed to take care of logging the user in the system, the latter only redirects to login page via ajax response.

// users_controller.php
class UsersController extends AppController {
  var $name = 'Users';
 
  function login() {
    //… check login credentials
    // let's assume they were ok, then perform the action requested by the user before logging in
    if ($this->Session->check('loginRedirectUrl')) {
      if ($this->Session->check('loginRedirectParams')) {
        $params = $this->Session->read('loginRedirectParams');
        $params[] = 'return';
        $this->Session->del('loginRedirectParams');
        $this->requestAction($params['url']['url'], $params);
      }
      $url = $this->Session->read('loginRedirectUrl');
      $this->Session->del('loginRedirectUrl');
      $this->redirect($url);
    }
  }
 
  function ajax_login() {
    $this->render('ajax_login', 'ajax');
  }
 
  /**
   * action that is accessed through ajax request
   */
  function ajax_action() {
    $this->checkSession();
    // do something creative
  }
}

Now create view file: ajax_login.ctp. It will contain JavaScript code that will make the browser load login page. That is something I don’t feel fully comfortable with, because you must handle ajax response in your view files to place this code in page body from where the browser can read it and execute. Since most ajax requests handles their responses, this will work fine, but probably there are some that don’t. You should try something else on such occasions.

// ajax_login.ctp
<script type="text/javascript">
window.location = '<?php echo 'http://'.$_SERVER['HTTP_HOST'].$html->url('users/login').'"'; ?>';
</script>

The last piece of equation is app_controller.php file where we place a method that checks wheter the user is logged in and redirects him to login page if he’s not. Call this method at the beginning of every action/method that is restricted to registered users only.

// app_controller.php
class AppController extends Controller {
  var $components = array('Session', 'RequestHandler');
 
  function checkSession() {
    if (!$this->Session->check('User')) { // when the user is not logged in
      if ($this->RequestHandler->isAjax()) {
        $this->Session->write('loginRedirectUrl', $this->referer());
        $this->Session->write('loginRedirectParams', $this->params);
        $this->requestAction('/users/ajax_login');
      } else {
        $this->Session->write('loginRedirectUrl', $this->params['url']['url']);
        $this->redirect('/users/login');
      }
    }
  }
}

That’s it. It works both for ajax and usual requests, CakePHP 1.1 and 1.2. I just can’t figure out how to avoid this JS trick, if you have any ideas please let me know.

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