Real time validation for input box using Primefaces/JSF [duplicate] - jsf

Question

This question already has an answer here:
How to validate availability of username in database?
(1 answer)
Closed 5 years ago.
I need to know if there is a way to do real-time validation using Primefaces/JSF?
My requirement looks simple:
I've an input box which would take only unique name. For eg.., if an user is looking to input an name which already exists in database, it
should throw error message like "User Name already exists." This
should happen as soon as the user has moved out of the input box
Reference can be inferred from Google registration page
I've spent a lot of time researching on internet but haven't arrived at any concrete solution.
I'm primarily looking for a solution in Primefaces/JSF. Is it possible?

Answer 1

You can do that with plain JSF. You just have to use a validator and add ajax behavior to your input field, e.g.
facelet
<h:form id="form">
<h:messages id="messages" />
<h:inputText value="#{anyBean.username}" validator="userValidator">
<f:ajax render="#this messages" />
</h:inputText>
</h:form>
validator
#FacesConverter("userValidator")
public class UserValidator implements Validator {
#Override
public void validate(FacesContext fc, UIComponent component, Object value) throws ValidatorException {
String username = (String) value;
if (usernameExists(username)) {
throw new ValidatorException(new FacesMessage("User Name already exists."));
}
}
private boolean usernameExists(String username) {
// check if username exists here
}
}
Of course you can also use the equivalent PrimeFaces components p:messages, p:inputText and p:ajax.