Magento2.3.3 :Get Value of Custom Product Attribute on Magento2 Rest API V1/orders/

Question

I am trying to get the Custom Product Attribute (uom). I want to get the Attribute value to display on the rest/V1/orders API call. m using this https://magento.stackexchange.com/a/303780/68018

app/code/{Vendorname}/{ModuleName}/etc

 <?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="uom" type="string" />
    </extension_attributes>
</config>

namespace {VendorName}{ModuleName}\Plugin\ProductOption.php

<?php


namespace {VendorName}\{ModuleName}\Plugin;

use Magento\Sales\Api\Data\OrderItemInterface;

    class ProductOption
    {
    
    
        /**
         * @var \Magento\Sales\Api\Data\OrderItemExtensionFactory
         */
        private $orderItemExtensionFactory;
    
        public function __construct(
            \Magento\Sales\Api\Data\OrderItemExtensionFactory $orderItemExtensionFactory
        ) {
    
            $this->orderItemExtensionFactory = $orderItemExtensionFactory;
        }
        public function beforeAdd(
            \Magento\Sales\Model\Order\ProductOption $subject,
            OrderItemInterface $orderItem
        ) {
            $extensionAttributes = $orderItem->getExtensionAttributes();
            if(null=== $extensionAttributes){
                $extensionAttributes= $this->orderItemExtensionFactory->create();
    
            }
            $extensionAttributes->setCustomField($order->getCustomField());
            $orderItem->setExtensionAttributes($extensionAttributes);
        }
    }

app/code/{Vendorname}/{ModuleName}/etc/di.xml

<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="/lib/internal/Magento/Framework/ObjectManager/etc/config.xsd">
    <type name="Magento\Sales\Api\Data\OrderItemInterface">
            <plugin name="custom_attribute_uom" type="Devcrew\CustomAttribute\Plugin\ProductOption"/>
        </type>
    </config>

Answer 1

You should use the afterGet and/or afterGetList function. Tell me if you need any more help

<?php


namespace {VendorName}\{ModuleName}\Plugin;

use Magento\Sales\Api\Data\OrderItemInterface;

    class ProductOption
    {
    
    
        /**
         * @var \Magento\Sales\Api\Data\OrderItemExtensionFactory
         */
        private $orderItemExtensionFactory;
    
        public function __construct(
            \Magento\Sales\Api\Data\OrderItemExtensionFactory $orderItemExtensionFactory
        ) {
    
            $this->orderItemExtensionFactory = $orderItemExtensionFactory;
        }


        public function afterGet(
            \Magento\Sales\Model\Order\ProductOption $subject,
            OrderItemInterface $orderItem
        ) {
            $extensionAttributes = $orderItem->getExtensionAttributes();
            if(null=== $extensionAttributes){
                $extensionAttributes= $this->orderItemExtensionFactory->create();
    
            }
            $extensionAttributes->setCustomField($order->getCustomField());
            $orderItem->setExtensionAttributes($extensionAttributes);
        }
    }

Answer 2

namespace {VendorName}{ModuleName}\Plugin\ProductOption.php

<?php
namespace {VendorName}{ModuleName}\Plugin;

use Magento\Sales\Api\OrderRepositoryInterface;

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

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

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

        public function afterGet(
            \Magento\Sales\Api\OrderRepositoryInterface $subject,
            \Magento\Sales\Api\Data\OrderInterface $resultOrder
        ) {
            $resultOrder = $this->getExtensionAttributesItem($resultOrder);
            return $resultOrder;
        }


          protected function getExtensionAttributesItem(\Magento\Sales\Api\Data\OrderInterface $order)
          {
              $orderItems = $order->getItems();
              if (null !== $orderItems) {
                  /** @var \Magento\Sales\Api\Data\OrderItemInterface $orderItem */
                  foreach ($orderItems as $orderItem) {
                      $extensionAttributes = $orderItem->getExtensionAttributes();
                      if ($extensionAttributes && $extensionAttributes->getUom()) {
                          continue;
                      }
                      $uom = $orderItem->getProduct()->getData('uom');
                      /** @var \Magento\Sales\Api\Data\OrderItemExtension $orderItemExtension */
                      $orderItemExtension = $extensionAttributes
                          ? $extensionAttributes
                          : $this->orderItemExtensionFactory->create();
                      if($uom) {
                          $orderItemExtension->setUom($uom);
                      }

                      $orderItem->setExtensionAttributes($orderItemExtension);
                }
              }
              return $order;
          }



            public function afterGetList(
                \Magento\Sales\Api\OrderRepositoryInterface $subject,
                \Magento\Sales\Model\ResourceModel\Order\Collection $resultOrder
            ) {
                foreach ($resultOrder->getItems() as $order) {
                    $this->afterGet($subject, $order);
                }

                return $resultOrder;
            }
}