<validators>
<validator type="requiredstring">
<param name="fieldName">username</param>
<param name="trim">true</param>
<message>username is required</message>
</validator>
<field name="username">
<field-validator type="requiredstring">
<param name="trim">true</param>
<message>username is required</message>
</field-validator>
</field>
</validators>