How to add extension attributes to Customer entity in Magento2?

Question

I am trying to add extension attributes to customer entity.

I set extension_attributes.xml as follows:

<?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\Customer\Api\Data\CustomerInterface">
        <attribute code="my_attribute" type="Text">
            <join reference_table="my_entity"
                  reference_field="customer_id"
                  join_on_field="entity_id">
                <field>my_entity_attribute</field>
            </join>
        </attribute>
    </extension_attributes>
</config>

The table my_entity exists and it has a column called customer_id and I want to join this field to the entity_id field in the customer_entity table, and add my_entity_attribute value as the ultimate extension attribute to customer.

What am I doing wrong?

To test this, I am doing a GET rest api call to endpoint customers/me and debugging $this->_getExtensionAttributes() inside \Magento\Customer\Model\Data\Customer::getExtensionAttributes(), but it gives null.

Answer 1

Type Text is not valid, use string instead. Then remember to clear var/generation, var/cache and var/di, to have changes applied.

Also see this answer to get understanding what actions are required to get extension attribute loaded during get and getList. Join directive will work for getList only.