EmailValidator.java

package com.sakadream.jsf.validator;

import javax.faces.application.FacesMessage;
import javax.faces.component.UIComponent;
import javax.faces.context.FacesContext;
import javax.faces.validator.FacesValidator;
import javax.faces.validator.Validator;
import javax.faces.validator.ValidatorException;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * Created by Phan Ba Hai on 21/07/2017.
 */

@FacesValidator("com.sakadream.jsf.validator.EmailValidator")
public class EmailValidator implements Validator {
    private static final String EMAIL_PATTERN = "^[_A-Za-z0-9-]+(\\." +
            "[_A-Za-z0-9-]+)*@[A-Za-z0-9]+(\\.[A-Za-z0-9]+)*" +
            "(\\.[A-Za-z]{2,})$";

    private Pattern pattern;
    private Matcher matcher;

    public EmailValidator(){
        pattern = Pattern.compile(EMAIL_PATTERN);
    }

    @Override
    public void validate(FacesContext facesContext, UIComponent uiComponent, Object o) throws ValidatorException {
        matcher = pattern.matcher(o.toString());
        if(!matcher.matches()) {
            FacesMessage msg =
                    new FacesMessage("E-mail validation failed:",
                            "Invalid E-mail format.");
            msg.setSeverity(FacesMessage.SEVERITY_ERROR);
            throw new ValidatorException(msg);
        }
    }
}