Adding an Extension Attribute to Sales Order Items - Magento 2

Question

I have created some custom attributes for products and using these attributes in order view in customer account orders section. I have deleted few products. When I view the customer orders, it gives exception because the custom attributes data does not save in sales_order_items table. For this I decided to create extension attributes to save the custom attributes data in sales_order_items entity. I have done the below steps so far but could not able to fetch the custom attributes data in orders view section in customer account.

Step-1 Vendor\Module\registration.php

<?php
\Magento\Framework\Component\ComponentRegistrar::register(
    \Magento\Framework\Component\ComponentRegistrar::MODULE,
    'Vendor_Module',
    __DIR__
);

Step-2 Vendor/Module/etc/module.xml

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:noNamespaceSchemaLocation="urn:magento:framework:Module/etc/module.xsd">
    <module name="Vendor_Module" setup_version="0.0.1">
    </module>
</config>

Step-3 Vendor/Module/etc/di.xml

<?xml version="1.0" ?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
    <type name="Magento\Sales\Api\OrderManagementInterface">
        <plugin name="extension_attribute_plugin" type="Vendor\Module\Plugin\AddExtensionAttributePlugin"/>
    </type>
</config>

Step-4 Vendor/Module/etc/extension_attributes.xml

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Api/etc/extension_attributes.xsd">
    <extension_attributes for="Magento\Sales\Api\Data\OrderItemInterface">
        <attribute code="order_items_extension_attributes" type="string" />
    </extension_attributes>
</config>

Step-5 Vendor/Module/Plugin/AddExtensionAttributePlugin.php

<?php

namespace Vendor\Module\Plugin;

use Magento\Catalog\Model\ProductFactory;

class AddExtensionAttributePlugin
{
    /** @var \Magento\Sales\Api\Data\OrderExtensionFactory */
    protected $orderExtensionFactory;

    /** @var \Magento\Sales\Api\Data\OrderItemExtensionFactory */
    protected $orderItemExtensionFactory;

    /**
     * @param \Magento\Sales\Api\Data\OrderExtensionFactory $orderExtensionFactory
     * @param \Magento\Sales\Api\Data\OrderItemExtensionFactory $orderItemExtensionFactory
     */
    public function __construct(
        \Magento\Sales\Api\Data\OrderExtensionFactory $orderExtensionFactory,
        \Magento\Sales\Api\Data\OrderItemExtensionFactory $orderItemExtensionFactory
    ) {
        $this->orderExtensionFactory = $orderExtensionFactory;
        $this->orderItemExtensionFactory = $orderItemExtensionFactory;
    }


    /**
     * @param \Magento\Sales\Api\OrderManagementInterface $subject
     * @param $resultOrder
     * @return mixed
     */
    public function afterPlace( \Magento\Sales\Api\OrderManagementInterface $subject, $resultOrder) {
        foreach ($resultOrder->getItems() as $orderItem) {
            $extensionAttributes = $orderItem->getExtensionAttributes();
            if (!($extensionAttributes && $extensionAttributes->getOrderItemsExtensionAttributes())) {
                /** @var \Magento\Sales\Api\Data\OrderItemExtension $orderItemExtension */
                $orderItemExtension = $extensionAttributes
                    ? $extensionAttributes
                    : $this->orderItemExtensionFactory->create();
                if ($orderItem->getProduct()->getOrderItemsExtensionAttributes()) {
                    $orderItemExtension->setOrderItemsExtensionAttributes($orderItem->getProduct()->getOrderItemsExtensionAttributes());
                }
                $orderItem->setExtensionAttributes($orderItemExtension);
            }
        }
        $resultOrder->save();
        return $resultOrder;
    }
}

Step-6 Getting the extension attributes in orders view section

$items = $order->getItems();
foreach ($items as $item){
    $extension_attribute_value = $item->getExtensionAttributes()->getOrderItemsExtensionAttributes();
}

Please any one can suggest if I am missing something?

Answer 1

Try below.

$items = $order->getItems();
foreach ($items as $item){
    $extension_attribute_value = $item->getProduct()->getOrderItemsExtensionAttributes();
}

But I dont think this is the fucntionality you wanted because if the product changes the value of this attribute it gonna change on the order. I believe you want to add the attribute value of this specific day of the purchase.

You can do that by creating a column on the sales_order_item and saving there the value of the product attribute with the use of plugin.

I think you didnt understand correctly the use of extention attribute. Here is how you create an extention attribute on the sales order item. Magento 2 how add extension attribute to order item

Here is another good resource to understand the consept https://fooman.com/blog/an-introduction-to-extension-attributes.html