How to save a file using MongoDB's GridFS in Lithium

BooksController.php

<?php

namespace app\controllers;

use \app\models\Book;
use \app\models\Job;
use \app\models\File;

class BooksController extends \lithium\action\Controller {

    public function index() 
    {
        $pageId = 'books';
        $books = Book::all();
        
        return compact('books', 'pageId');
    }

    public function details() {
        $pageId = 'details';
        $book = Book::first(array(
            'conditions' => array('key' => $this->request->key)
        ));
        $job = Job::create();
        
        if (!$book) {
            $this->redirect('Books::index');
        }
        
        if ($this->request->data) {
            if ($job->save($this->request->data)) {
                $file = File::create();
                $fileData = array(
                    'file' => $this->request->data['file'],
                    'job_id' => (string) $job->_id
                );
                if ($file->save($fileData)) {
                    $this->redirect('Books::index');
                }
            }
        }
        
        return compact('pageId', 'book', 'job');
    }

}

File.php

<?php 

namespace app\models;

class File extends \lithium\data\Model {
    
    protected $_meta = array('source' => 'fs.files');

	public $validates = array(
        // 'job_id' => array('notEmpty', 'message' => 'There was a problem selecting your book. Please try again.'),
    );
	
}

Job.php

<?php 

namespace app\models;

class Job extends \lithium\data\Model {
    
    public $validates = array(
        'file'  => array('notEmpty', 'message' => 'You must supply a photo.'),
        'first' => array('notEmpty', 'message' => 'Please tell us your first name.'),
        'last'  => array('notEmpty', 'message' => 'Please tell us your last name.'),
        'email' => array('notEmpty', 'message' => 'Please tell us your email.'),
        'key'   => array('notEmpty', 'message' => 'There was a problem selecting your book. Please try again.'),
    );
	
}

As far as I know, that's the only way (unless you specify the opening form tag manually).