Validation in valueChangeListener

[Joerg Bredlau]

Hello,

I'm working on validation for my InputComponents. For each of the 
components I want individual messages if
the field is empty.
I know, thats impossible with the standard required-Validator.
I tried out OptionalValidatorFramwork, but it doesn't work for me.

Now I want to make the validation by hand in valueChangeListeners, added 
to the components. My Problem is:
The ValueChangeListener is executed before model_update,thats right? How 
can I get back to
ValidationPhase(?) when the field is empty, to display the input-page 
again and not update my model?


Here is the codefragment I'm working on:

public void lastnameChange(ValueChangeEvent event) {
    String lastname = ((String) event.getNewValue()).trim();
    String compId = event.getComponent().getId();

    if (( lastname== null) || (lastname.length() == 0)) {
        FacesUtils.addInfoMessage(compId, "Please enter your name.");
        // TODO go back to input page with old value
    }
}



Or is there another approach for validation with individual messages to
empty fields?


Thanks
Joerg