struts2examples/form_xml_validation/src/main/resources/org/apache/struts/edit/action/EditAction-validation.xml

<!DOCTYPE validators PUBLIC "-//Apache Struts//XWork Validator 1.0.3//EN"
		"http://struts.apache.org/dtds/xwork-validator-1.0.3.dtd">
<validators>
 <validator type="requiredstring">
 	<param name="fieldname">personBean.firstName</param>
 	<message>First name is required.</message>
 </validator>
  <validator type="requiredstring">
 	<param name="fieldname">personBean.lastName</param>
 	<message>Last name is required.</message>
 </validator>
 <validator type="requiredstring">
 	<param name="fieldname">personBean.email</param>
 	<message>Email address is required.</message>
 </validator>
 <validator type="email">
 	<param name="fieldname">personBean.email</param>
 	<message>Email address not valid.</message>
 </validator>
 <validator type="requiredstring">
 	<param name="fieldname">personBean.phoneNumber</param>
 	<message>Phone number is required.</message>
 </validator>
<validator type="regex">
	<param name="fieldname">personBean.phoneNumber</param>
	<param name="regex"><![CDATA[\d{3}-\d{3}-\d{4}]]></param>
	<message>Phone number must be entered as 999-999-9999.</message>
</validator>
<validator type="fieldexpression">
	<param name="fieldname">personBean.carModels</param>
	<param name="expression"><![CDATA[personBean.carModels.length > 0]]></param>
	<message>You must select at least one car model.</message>
</validator>
</validators>