custom validator call on button through ajax - ajax

Question

hi i wrote a custom a validator which gets the system name and compare it against the id in database, now i wanna apply a check if this value is exactly the same, user must be allowed to click the button and move on else some error message should be displayed. and i am really confused how to call the validator() on through ajax.
my view page code is
<h:commandButton action="sample?faces-redirect=true" value="submit">
<f:ajax execute="#{csample.UserValidator}" render="#form" >
<h:inputText name="idtext" value="#{csampleBean.id}" />
</f:ajax>
</h:commandButton>
and my custom validator
public void UserValidator(FacesContext context, UIComponent toValidate, Object value)
throws UnknownHostException, ValidatorException, SQLException, NamingException
{
java.net.InetAddress localMachine = java.net.InetAddress.getLocalHost();
String machine= localMachine.getHostName();
String query = "select * from USER_ where USER_ID = '"+machine+"'";
Context initContext = new InitialContext();
Context envContext = (Context)initContext.lookup("java:/comp/env");
DataSource ds = (DataSource)envContext.lookup("jdbc/myoracle");
Connection conn = ds.getConnection();
Statement stat = conn.createStatement();
//get customer data from database
ResultSet result = stat.executeQuery(query);
if (query==machine)
// what to do here
conn.close();
need some guidance

Answer 1

You need to create a class implementing the Validator interface. On validation fail, 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.
You can register the custom validator to JSF by annotating it with #FacesValidator with therein the validator ID. You can reference it in <h:inputXxx validator> or <f:validator validatorId>.
Here's a kickoff example:
#FacesValidator("userValidator")
public class UserValidator implements Validator {
#Override
public void validate(FacesContext context, UIComponent component, Object value) throws ValidatorException {
// ...
if (!valid) {
String message = "Sorry, validation has failed because [...]. Please try again.";
throw new ValidatorException(new FacesMessage(FacesMessage.SEVERITY_ERROR, message, null));
}
}
}
Which is been used as follows (note: <h:inputText> does not have name attribute! instead use id; also note that your initial code snippet has some nesting which isn't making any sense):
<h:inputText id="idtext" value="#{csampleBean.id}" validator="userValidator">
<f:ajax render="idtextMessage" />
</h:inputText>
<h:message id="idtextMessage" for="idtext" />
<h:commandButton action="sample?faces-redirect=true" value="submit" />
See also:
How to perform validation in JSF, how to create a custom validator in JSF
Unrelated to the concrete problem, your JDBC code is leaking DB resources. Please fix that as well.