JSF Primefaces ajax rendered not updating - ajax

Question

I am trying to write a simple create user page. I want the user to be able to type a desired username and if the username is already taken, then an output text shows up and says "Username already in use".
Here is my xhtml page
<tr>
<td>Username: </td>
<td>
<p:inputText id="username" value="#{createUserManagedBean.username}" required="true" requiredMessage="Username is required.">
<p:ajax event="keyup" update="uniqueUsernameMessage"/>
</p:inputText>
</td>
<td>
<h:outputText id="uniqueUsernameMessage" value="Username already in use" rendered="#{!createUserManagedBean.checkUniqueUsername()}" />
</td>
</tr>
Here is my managed bean
public boolean checkUniqueUsername()
{
if(!StringUtils.isBlank(getUsername()))
{
UserDTO userDTO = new UserDTO();
userDTO.setUsername(username);
boolean result = getUserService().validateUniqueUsername(userDTO);
return result;
}
else
return false;
}
My issue is that the message is not updating for each keyup event. The service was being called, but the element was not changing whether or not it would display or not depending on the method result.

Answer 1

Using the rendered attribute is absolutely not the right way to validate an input component. You should be using a real Validator implementation. Therein you can in case of invalidation just throw a ValidatorException with a FacesMessage. JSF will then take care that the FacesMessage ends up in the right <h:message> associated with the input component.
All in all, this should do:
<p:inputText id="username" value="#{createUserManagedBean.username}" ...>
<f:validator binding="#{uniqueUsernameValidator}" />
<p:ajax event="keyup" update="usernameMessage" />
</p:inputText>
<h:message id="usernameMessage" for="username" />
With
#ManagedBean
#RequestScoped
public class UniqueUsernameValidator implements Validator {
#EJB
private UserService userService;
#Override
public void validate(FacesContext context, UIComponent component, Object value) throws ValidatorException {
if (value == null || value.isEmpty()) {
return; // Let required="true" handle.
}
String username = (String) value;
if (userService.findByUsername(username) != null) {
throw new ValidatorException(new FacesMessage(
FacesMessage.SEVERITY_ERROR, "Username already in use. Please choose another", null));
}
}
}
See also:
How to perform validation in JSF, how to create a custom validator in JSF
Please note that the validator is a #ManagedBean instead of a #FacesValidator because the #EJB could otherwise not be injected. But if you're not using EJBs and are manually creating service classes and fiddling with transactions yourself, then you could probably just keep it a real #FacesValidator:
#FacesValidator("uniqueUsernameValidator")
public class UniqueUsernameValidator implements Validator {
Which is then instead to be referenced as follows:
<f:validator validatorId="uniqueUsernameValidator" />
See also:
How to inject in #FacesValidator with #EJB, #PersistenceContext, #Inject, #Autowired