You need a validation.properties
file at /WEB-INF/messages
with an entry similar to this (for example):
NotEmpty.homeFormItem.one=The field {0} is empty
And don't forget to add a spring bean to resolve your validation messages:
<bean id="messageSource" class="org.springframework.context.support.ReloadableResourceBundleMessageSource">
<property name="basename" value="/WEB-INF/messages/validation" />
</bean>