With all the changes, we're finally ready, so let's take a look at the final mapping file. The most interesting detail is to check how the id gets mapped with our defined custom type for OrderId:

<?xml version="1.0" encoding="UTF-8"?>
<doctrine-mapping
    xmlns="http://doctrine-project.org/schemas/orm/doctrine-mapping"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="
        http://doctrine-project.org/schemas/orm/doctrine-mapping
    https://raw.github.com/doctrine/doctrine2/master/doctrine-mapping.xsd">

    <entity
        name="DddBillingDomainModelOrder"
        table="orders">

        <id name="id" column="id" type="OrderId" />

        <field
            name="amount"
            type="decimal"
            nullable="false"
            scale="10"
            precision="5"
        />
        <field
            name="firstName"
            type="string"
            nullable="false"
        />
        <field
            name="lastName"
            type="string"
            nullable="false"
        />
    </entity>
</doctrine-mapping>