package com.corejsf;
import javax.validation.ConstraintValidator;
import javax.validation.ConstraintValidatorContext;
public class LuhnCheckValidator implements ConstraintValidator<LuhnCheck, String> {
public void initialize(LuhnCheck constraintAnnotation) {
}
public boolean isValid(String value, ConstraintValidatorContext context) {
return luhnCheck(value.replaceAll("\\D", ""));
}
private static boolean luhnCheck(String cardNumber) {
int sum = 0;
for(int i = cardNumber.length() - 1; i >= 0; i -= 2) {
sum += Integer.parseInt(cardNumber.substring(i, i + 1));
if(i > 0) {
int d = 2 * Integer.parseInt(cardNumber.substring(i - 1, i));
if(d > 9) d -= 9;
sum += d;
}
}
return sum % 10 == 0;
}
}