If a property’s definition does not set the default value of a property, then its default value is null. For example, the following <property> tag defines a property named favoriteColor whose default value is null:
<property name="favoriteColor" data-type="string"/>
If you want to affirmatively set a default value to null, use this form:
<property name="favoriteColor" data-type="string" default="__NULL__"/>
This technique is useful if, for example, you are combining two or more repository definition files into a single template and need to override a non-null value and restore the default to null.
