struts-sandbox/mailreader-course/struts2/localize/src/java/Login-validation.xml

<!DOCTYPE validators PUBLIC "-//OpenSymphony Group//XWork Validator 1.0.2//EN" "http://www.opensymphony.com/xwork/xwork-validator-1.0.2.dtd">

<validators>
    <field name="username">
        <field-validator type="requiredstring">
            <message key="error.username.required"/>
        </field-validator>
    </field>
    <field name="password">
        <field-validator type="requiredstring">
            <message key="error.password.required"/>
        </field-validator>
    </field>
</validators>