Validate rich:dataTable value size's on form submit - jsf

Question

I have a "new item" form that requires a list of dates, with the following components:
A <rich:calendar> input;
A <a4j:commandButton> that adds the chosen date to a List<Date> chosenDates in the backing bean;
A <rich:dataTable> with it's value set to the List<Date> chosenDates attribute;
A <a4j:commandButton> per dataTable row that removes it's date from theList<Date> chosenDates;
How to validate (JSF's validation phase) the size of the chosenDates list on form submit (creation process)?
RichFaces 4, JSF 2.1 (Mojarra).

Answer 1

I'd advise a cleaner approach with a JSF PhaseListener. The JSF processing will stop skip ahead the other phases if validation fails. Create a PhaseListener that will inspect the size of your list during the validations phase as against during the model update/invoke action phase. Try something like this
Create a phase listener for the validations phase
public class TestPhaseListener implements PhaseListener {
#Override
public void afterPhase(PhaseEvent event) {
throw new UnsupportedOperationException("Not supported yet.");
}
#Override
public void beforePhase(PhaseEvent event) {
if(event.getPhaseId().equals(PhaseId.PROCESS_VALIDATIONS)){
FacesContext ctx = event.getFacesContext();
YourBeanClass theBeanClass = ctx.getApplication().evaluateExpressionGet(ctx, "#{someBean}", YourNeanClass.class); //obtain a reference to the backing bean containing the list
/*
inspect the size of the list here and based on that throw the exception below
*/
throw new ValidatorException(new FacesMessage("Too many dates","Too Many Dates"));
}
}
#Override
public PhaseId getPhaseId() {
throw new UnsupportedOperationException("Not supported yet.");
}
}
Register your new listener in the faces_config.xml file
<lifecycle>
<phase-listener>your.package.structure.TestPhaseListener</phase-listener>
</lifecycle>
EDIT: Based on your comment, as an alternative, you can hook into the component's lifecycle using the <f:event/> tag and the preValidate or postValidate events (depending on your preference)
A listener tag to your component
<rich:dataTable>
<f:event type="preValidate" listener="#{yourBean.listener}"/>
</rich:dataTable>
Define a listener method in your backing bean to run per your defined event. The method signature must take an argument of type ComponentSystemEvent
public void preCheck(ComponentSystemEvent evt){
//You're in your backing bean so you can do pretty much whatever you want. I'd advise you mark the request as validation failed and queue FacesMessages. Obtain a reference to FacesContext and:
facesContext.validationFailed();
}

Answer 2

Do something like:
#{yourBean.chosenDates.size()}
I suppose you have a getter called getChosenDates which returns the chosenDates list.

Answer 3

Regarding your "validation concerns":
You can create a Validate method in your bean and return list of ValidationMessages. A sample is below, one that i used in my code.
public List<ValidationMessage> validate() {
List<ValidationMessage> validations = new ArrayList<ValidationMessage>();
int curSampleSize = sampleTable.getDataModel().getRowCount();
if(getNumberOfSamples() != null) {
size += getNumberOfSamples();
} else {
validations.add(new ValidationMessage("Please enter the no of samples to continue."));
return validations;
}
return validations;
}
Then, on submit you can check if you have any ValidationMessages as follows:
List<ValidationMessage> errs = validate();
if(errs.size()>0) {
FacesValidationUtil.addFacesMessages(errs);
return null;
}
Hope this helps!