JSF проверить имя пользователя

ManagedBean
public class Login implements Serializable {
 
@EJB
private CustomerRepository customerRepository;
 
private String password;
private String login;
 
public String getPassword() {
return password;
}
 
public void setPassword(String password1) {
this.password = password1;
}
 
public void doLogin(ActionEvent actionEvent) {
Customer customer;
try {
customer = customerRepository.findUserByLoginAndPassword(login, password);
} catch (Exception e) {
e.printStackTrace();
return;
}
FacesUtils.putUserId(customer.getId());
redirectToOverview();
}
 
public void registerNewUser(ActionEvent actionEvent) {
Customer customer = customerRepository.createCustomer(login, password);
FacesUtils.putUserId(customer.getId());
redirectToOverview();
}
 
public String getLogin() {
return login;
}
 
public void setLogin(String login) {
this.login = login;
}
 
 
 
private void redirectToOverview() {
FacesUtils.redirect("overview.xhtml");
}
 
 
public boolean chechCustomer(ActionEvent actionEvent){
if (StringUtil.isEmpty(login) || StringUtil.isEmpty(password)){
return false;
}
Customer customer = customerRepository.findUserByLoginAndPassword(login,password);
if (customer!=null){
return false;
}
 
 
return true;
 
}
}

<h:head>
 
</h:head>
<h:body>
<h1>Login</h1>
<h:form>
<p:layout style="min-width:400px;min-height:200px;">
<p:layoutUnit position="center">
<h:panelGrid columns="2" cellpadding="5">
 
<h:outputText value="Login: "/>
<p:inputText value="#{login.login}"/>
 
<h:outputText value="Password: "/>
<p:password id="nonFeedback" value="#{login.password}"/>
 
<p:commandButton value="Login" id="login"
actionListener="#{login.doLogin}"
styleClass="ui-priority-primary"/>
 
<p:commandButton value="Register" id="register"
actionListener="#{login.registerNewUser}"
styleClass="ui-priority-primary"/>
</h:panelGrid>
</p:layoutUnit>
</p:layout>
<!-- <h:selectOneMenu>
<f:selectItem itemLabel="Bibliography"> </f:selectItem>
<f:selectItem itemLabel="History"> </f:selectItem>
</h:selectOneMenu>
 
<h:button outcome="Body.xhtml" value="some button"></h:button>
<h:link outcome="Body.xhtml"> some link</h:link>
 
<h:commandButton action="#{buttonAction.buttonAction}" value="some Button"> </h:commandButton>
<h:commandLink> some Link</h:commandLink>-->
 
 
 
</h:form>
</h:body>
</html>

public void validateUserName(FacesContext context, UIComponent comp, Object value) {
       String userName = (String) value;       
 
       if (repository.existsByUserName(userName)) {
              ((UIInput) comp).setValid(false);
 
              FacesMessage message = new FacesMessage("Username already in use");
              context.addMessage(comp.getClientId(context), message);
 
       }
}