validation - Allowing only digits in aui:form, with Liferay portlet-model-hints.xml -

my portlet-model-hints.xml below stipulates quantity required, works fine.
want stipulate quantity must made of digits:

<model-hints>     <model name="com.example.model.myentity">         [...]         <field name="order" type="long">             <validator name="required" />             <validator name="digits" />       <----- not work         </field>         [...]     </model> </model-hints> 

problem: adding <validator name="digits" /> makes text field disappear.

is there problem in syntax? should validation in jsp instead? way here jsp form add/edit entity:

<aui:form action="<%= editmyentityurl %>" method="post" name="fm">     <aui:fieldset>         [...]         <aui:input name="quantity" />         [...]     </aui:fieldset>     [....] </aui:form> 

[workaround, still looking better solution]

not elegant @ all, moving digits validation jsp works:

<aui:form action="<%= editmyentityurl %>" method="post" name="fm">     <aui:fieldset>         [...]         <aui:input name="quantity">             <aui:validator name="digits"/>         </aui:input>         [...]     </aui:fieldset>     [....] </aui:form> 

it must done in jsp forms use entity.