How to handle extension attributes?

[marvincaspar]

I want to extend the payment object with 2 new attributes.

etc/extension_attributes.xml

    <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\OrderPaymentInterface">
            <attribute code="payment_token" type="string"/>
            <attribute code="transaction_token" type="string"/>
        </extension_attributes>
    </config>

I created an update script to add both new attributes to the sales_order_payment table. If I now set the extension attributes, they are not stored in the database.

    $orderPayment = $order->getPayment();

    // Set payment/transaction token to extension attributes
    $paymentExtensionAttributes = $orderPayment->getExtensionAttributes();
    if (is_null($paymentExtensionAttributes)) {
        $paymentExtensionAttributes = $this->extensionAttributesFactory->create('Magento\Sales\Model\Order\Payment');
    }

    $paymentExtensionAttributes->setPaymentToken("some-payment-token");
    $paymentExtensionAttributes->setTransactionToken("some-transaction-token");
    $orderPayment->setExtensionAttributes($paymentExtensionAttributes);
    $order->setPayment($orderPayment);
    $order->save();

I would expect that both attributes are automatically stored in the database table.

For testing I set the fields in the database and run $orderPayment->getExtensionAttributes() and got null as response. I thought that they are automatocally loaded.

Is my understanding from the extension attributes wrong? If yes, how I have to handle extension attributes?

[maksek]

Please ask questions in Forum. GitHub only for issue reporting with steps to reproduce.