404找不到页面代码点火器url

我是一个使用codeigniter的初学者。我正在使用以下url"http://localhost/ci/index.php/shopcart"访问控制器，我得到错误404页面未找到

控制器代码

     <?php
    class Cart extends CI_Controller { // Our Cart class extends the Controller class
        function Cart()
        {
            parent::CI_Controller(); // We define the the Controller class is the parent. 
        }

    }
        function index()
        {
            $this->load->model('cart_model'); // Load our cart model for our entire class 
            $data['products'] = $this->cart_model->retrieve_products(); // Retrieve an array with all products
            $data['content'] = 'cart/products'; // Select our view file that will display our products
            $this->load->view('index', $data); // Display the page with the above defined content
        }
?>

型号代码

<?php 
class Cart_model extends Model { // Our Cart_model class extends the Model class
// Function to retrieve an array with all product information
    function retrieve_products(){
        $query = $this->db->get('products'); // Select the table products
        return $query->result_array(); // Return the results in a array.
    }  
}

路线

$route['default_controller'] = "shopcart";

自动加载

$autoload['libraries'] = array('cart' , 'database');
$autoload['helper'] = array('form');