struts2 validator expression - struts2

Question

Is possible to make this conditional expression validation?:
(invitation.id==null and (newText==null or newText.isEmpty()))
I've tried several ways, several times, but don't achieve it.
This version is working, but on server-side, and ignore if invitation.id is null or empty... any ideas???:
<field name="newText">
<field-validator type="fieldexpression">
<param name="expression">!(invitation.id eq null and (newText eq null or newText.empty))</param>
<message>${getText("validation.required")}</message>
</field-validator>
</field>
http://struts.apache.org/release/2.2.x/docs/fieldexpression-validator.html
what is wrong with the expression?? Thanks!

Answer 1

Your problem is that you are trying to validate another field (invitation.id) into the newText Field Validator (i don't think it's possible, but I'm not sure).
However, you could split it into two validators, raising the message corrispondent to the failure case, that is more correct imho;
<field name="invitation.id">
<field-validator type="required">
<message>${getText("validation.invitation.id.required")}</message>
</field-validator>
</field>
<field name="newText">
<field-validator type="fieldexpression">
<param name="expression">
<![CDATA[
newText != null && !newText.trim().empty())
]]>
</param>
<message>${getText("validation.newText.required")}</message>
</field-validator>
</field>
, if you need to trim it, otherwise it could become simply
<field name="invitation.id">
<field-validator type="required">
<message>${getText("validation.invitation.id.required")}</message>
</field-validator>
</field>
<field name="newText">
<field-validator type="requiredString">
<message>${getText("validation.newText.required")}</message>
</field-validator>
</field>
Note that required is for every non-text fields, while requiredString is for text fields only.
Expression Validator is very powerful, but it should be used for more complex purposes:
for example, if you want to validate a Date against another one dynamically read (through a Getter) from your Action; lets say you've previously chosen a User, and you need to validate a date from the page against the user Start and End Validity interval; but you want to pass the validation too if the date is not inserted, because it is already handled by the required validator (so you won't raise two messages):
<field name="inputDate">
<field-validator type="required">
<message><![CDATA[ Input Date is mandatory ]]></message>
</field-validator>
<field-validator type="fieldexpression">
<param name="expression">
<![CDATA[
inputDate==null ||
(inputDate >= chosenUser.startValidity
&&
inputDate <= chosenUser.EndValidity
)
]]>
</param>
<message>
<![CDATA[Input Date must be included in the User Validity interval
(from ${chosenUser.startValidity} to ${chosenUser.endValidity} )
]]>
</message>
</field-validator>
</field>
where chosenUser is an User object from your Action (public User getChosenUser())
and startValidity and endValidity are properties of the User object (public Date getEndValidity()).
And as you can see, the dynamic read can be performed in messages too... this is how powerful expression validator is ;)

Answer 2

First of all expression is not a valid parameter. If you really want to validate on client side, try to use java-script or jquery for validation. But you have to validate inputs on server - side also because sometimes user could disable the javascript .So in that case you can use struts2 - validation.
for detailed explanation refer http://viralpatel.net/blogs/struts2-validation-framework-tutorial-example/

Answer 3

Ok, finally I used client-side validation width jquery emulating struts2.
I don't like this for compatibility reasons, please if there is a way to do it in a standard way, I'll apreciate any help.
Removing struts validation:
<!--<field name="newText">
<field-validator type="fieldexpression">
<param name="expression">!((invitation.id==null or invitation.id.empty) and (newText==null or newText.empty))</param>
<message>${getText("validation.required")}</message>
</field-validator>
</field>-->
Adding js/jquery code:
function mySubmit() {
if ((invitationId==null || invitationId<0) && $("#text").val().trim()=='') {
var trStrutsFieldError='<tr errorfor="text">'+
'<td colspan="2" align="center" valign="top"><span class="errorMessage">'+strValidationRequired+'</span></td>'+
'</tr>';
$(trStrutsFieldError).insertBefore($("#text").parent().parent());
return false;
}
return true;
}
$(document).ready(function(){
$("form").submit(function(event) {
$.each($("form").find("span.errorMessage"), function() { /* <tr errorfor="title"><td colspan="2" align="center"><span classname="errorMessage" class="errorMessage">Campo requerido */
return false;
});
if ($(mySubmit).exists()) {
if (!mySubmit())
return false;
}
return true;
});
});