Magento-将属性添加到发票项目

我想将“eEngine\u download”属性添加到发票项目中。我创建了一个观察者，用于侦听销售、订单、发票和付款事件。其想法是，观察者将使用特定于客户的url（实际上将通过调用外部Web服务获得）填充该属性“eEngine_download”

我已通过以下代码创建了该属性：

    $setup = new Mage_Eav_Model_Entity_Setup('core_setup');
$setup->addAttribute('invoice_item', 'epagine_download', array(
    'label'                       => 'Download',
    'type'                        => 'varchar',
    'input'                       => 'text'  ,
    'visible'                     => false,
    'required'                    => false  
))

这是我对观察者的配置：

<?xml version="1.0"?>
<config>
    <global>
        <models>
            <eboeksales>
                <class>Eboek_Sales_Model</class>
            </eboeksales>
        </models>
        <events>
            <sales_order_invoice_pay>
                <observers>
                    <eboek_sales_pay_observer>
                        <type>singleton</type>
                        <class>Eboek_Sales_Model_Pay_Observer</class>
                        <method>handle_sales_invoice_paid</method>
                    </eboek_sales_pay_observer>

                </observers>
            </sales_order_invoice_pay>    
        </events>
    </global>

</config>

（Magento版本为1.4） 谢谢你的反馈

class Eboek_Sales_Model_Pay_Observer {
    public function __construct()
    {

    }
    /**
     *
     * @param Varien_Event_Observer $observer
     * @return Eboek_Sales_Model_Pay_Observer
     */
    public function handle_sales_invoice_paid($observer)
    {

        $event = $observer->getEvent();
        Mage::log("Hello8812");
        $inv=$event->getInvoice();

        #Mage::log($inv);
        $a= $inv->getAllItems();

        Mage::log("=========================================================================");
        Mage::log($a[0]->getOrderItem()->getData());
        Mage::log("=========================================================================");
        Mage::log($a[0]->getData());
        Mage::log("=========================================================================");
        $event->GetBlahBlah();

        return $this;
    }
}