How to determine user Locale within CostraintValidator implementation in order to choose validation routine?

Question

How to internationalize Bean Validations? i.e to test ex. ZipCode using @ZipCode constraint that detects that current user is using given language (or has given country address) and adjust validation formula (regex like below) to that user context.

One property:

@ZipCode 
private String zipCode; 

and it will validate zip code depending on whether user is from USA, China or Germany, etc.

Below I found such regex patterns:

 "GB", "GIR[ ]?0AA|((AB|AL|B|BA|BB|BD|BH|BL|BN|BR|BS|BT|CA|CB|CF|CH|CM|CO|CR|CT|CV|CW|DA|DD|DE|DG|DH|DL|DN|DT|DY|E|EC|EH|EN|EX|FK|FY|G|GL|GY|GU|HA|HD|HG|HP|HR|HS|HU|HX|IG|IM|IP|IV|JE|KA|KT|KW|KY|L|LA|LD|LE|LL|LN|LS|LU|M|ME|MK|ML|N|NE|NG|NN|NP|NR|NW|OL|OX|PA|PE|PH|PL|PO|PR|RG|RH|RM|S|SA|SE|SG|SK|SL|SM|SN|SO|SP|SR|SS|ST|SW|SY|TA|TD|TF|TN|TQ|TR|TS|TW|UB|W|WA|WC|WD|WF|WN|WR|WS|WV|YO|ZE)(\d[\dA-Z]?[ ]?\d[ABD-HJLN-UW-Z]{2}))|BFPO[ ]?\d{1,4}"
"JE", "JE\d[\dA-Z]?[ ]?\d[ABD-HJLN-UW-Z]{2}"
"GG", "GY\d[\dA-Z]?[ ]?\d[ABD-HJLN-UW-Z]{2}"
"IM", "IM\d[\dA-Z]?[ ]?\d[ABD-HJLN-UW-Z]{2}"
"US", "\d{5}([ \-]\d{4})?"
"CA", "[ABCEGHJKLMNPRSTVXY]\d[ABCEGHJ-NPRSTV-Z][ ]?\d[ABCEGHJ-NPRSTV-Z]\d"
"DE", "\d{5}"
"JP", "\d{3}-\d{4}"
"FR", "\d{2}[ ]?\d{3}"
"AU", "\d{4}"
"IT", "\d{5}"
"CH", "\d{4}"
"AT", "\d{4}"
"ES", "\d{5}"
"NL", "\d{4}[ ]?[A-Z]{2}"
"BE", "\d{4}"
"DK", "\d{4}"
"SE", "\d{3}[ ]?\d{2}"
"NO", "\d{4}"
"BR", "\d{5}[\-]?\d{3}"
"PT", "\d{4}([\-]\d{3})?"
"FI", "\d{5}"
"AX", "22\d{3}"
"KR", "\d{3}[\-]\d{3}"
"CN", "\d{6}"
"TW", "\d{3}(\d{2})?"
"SG", "\d{6}"
"DZ", "\d{5}"
"AD", "AD\d{3}"
"AR", "([A-HJ-NP-Z])?\d{4}([A-Z]{3})?"
"AM", "(37)?\d{4}"
"AZ", "\d{4}"
"BH", "((1[0-2]|[2-9])\d{2})?"
"BD", "\d{4}"
"BB", "(BB\d{5})?"
"BY", "\d{6}"
"BM", "[A-Z]{2}[ ]?[A-Z0-9]{2}"
"BA", "\d{5}"
"IO", "BBND 1ZZ"
"BN", "[A-Z]{2}[ ]?\d{4}"
"BG", "\d{4}"
"KH", "\d{5}"
"CV", "\d{4}"
"CL", "\d{7}"
"CR", "\d{4,5}|\d{3}-\d{4}"
"HR", "\d{5}"
"CY", "\d{4}"
"CZ", "\d{3}[ ]?\d{2}"
"DO", "\d{5}"
"EC", "([A-Z]\d{4}[A-Z]|(?:[A-Z]{2})?\d{6})?"
"EG", "\d{5}"
"EE", "\d{5}"
"FO", "\d{3}"
"GE", "\d{4}"
"GR", "\d{3}[ ]?\d{2}"
"GL", "39\d{2}"
"GT", "\d{5}"
"HT", "\d{4}"
"HN", "(?:\d{5})?"
"HU", "\d{4}"
"IS", "\d{3}"
"IN", "\d{6}"
"ID", "\d{5}"
"IL", "\d{5}"
"JO", "\d{5}"
"KZ", "\d{6}"
"KE", "\d{5}"
"KW", "\d{5}"
"LA", "\d{5}"
"LV", "\d{4}"
"LB", "(\d{4}([ ]?\d{4})?)?"
"LI", "(948[5-9])|(949[0-7])"
"LT", "\d{5}"
"LU", "\d{4}"
"MK", "\d{4}"
"MY", "\d{5}"
"MV", "\d{5}"
"MT", "[A-Z]{3}[ ]?\d{2,4}"
"MU", "(\d{3}[A-Z]{2}\d{3})?"
"MX", "\d{5}"
"MD", "\d{4}"
"MC", "980\d{2}"
"MA", "\d{5}"
"NP", "\d{5}"
"NZ", "\d{4}"
"NI", "((\d{4}-)?\d{3}-\d{3}(-\d{1})?)?"
"NG", "(\d{6})?"
"OM", "(PC )?\d{3}"
"PK", "\d{5}"
"PY", "\d{4}"
"PH", "\d{4}"
"PL", "\d{2}-\d{3}"
"PR", "00[679]\d{2}([ \-]\d{4})?"
"RO", "\d{6}"
"RU", "\d{6}"
"SM", "4789\d"
"SA", "\d{5}"
"SN", "\d{5}"
"SK", "\d{3}[ ]?\d{2}"
"SI", "\d{4}"
"ZA", "\d{4}"
"LK", "\d{5}"
"TJ", "\d{6}"
"TH", "\d{5}"
"TN", "\d{4}"
"TR", "\d{5}"
"TM", "\d{6}"
"UA", "\d{5}"
"UY", "\d{5}"
"UZ", "\d{6}"
"VA", "00120"
"VE", "\d{4}"
"ZM", "\d{5}"
"AS", "96799"
"CC", "6799"
"CK", "\d{4}"
"RS", "\d{6}"
"ME", "8\d{4}"
"CS", "\d{5}"
"YU", "\d{5}"
"CX", "6798"
"ET", "\d{4}"
"FK", "FIQQ 1ZZ"
"NF", "2899"
"FM", "(9694[1-4])([ \-]\d{4})?"
"GF", "9[78]3\d{2}"
"GN", "\d{3}"
"GP", "9[78][01]\d{2}"
"GS", "SIQQ 1ZZ"
"GU", "969[123]\d([ \-]\d{4})?"
"GW", "\d{4}"
"HM", "\d{4}"
"IQ", "\d{5}"
"KG", "\d{6}"
"LR", "\d{4}"
"LS", "\d{3}"
"MG", "\d{3}"
"MH", "969[67]\d([ \-]\d{4})?"
"MN", "\d{6}"
"MP", "9695[012]([ \-]\d{4})?"
"MQ", "9[78]2\d{2}"
"NC", "988\d{2}"
"NE", "\d{4}"
"VI", "008(([0-4]\d)|(5[01]))([ \-]\d{4})?"
"PF", "987\d{2}"
"PG", "\d{3}"
"PM", "9[78]5\d{2}"
"PN", "PCRN 1ZZ"
"PW", "96940"
"RE", "9[78]4\d{2}"
"SH", "(ASCN|STHL) 1ZZ"
"SJ", "\d{4}"
"SO", "\d{5}"
"SZ", "[HLMS]\d{3}"
"TC", "TKCA 1ZZ"
"WF", "986\d{2}"
"XK", "\d{5}"
"YT", "976\d{2}"

Answer 1

Just group the zip code and the country code in a single entity and validate that entity as a whole with a custom constraint.

E.g. in a sane Address entity:

@YourCustomAddressConstraint
public class Address {

    @NotNull
    private String line;

    private String building;

    @NotNull
    private String locality;

    private String administrativeArea;

    @NotNull
    private String postalCode;

    @NotNull
    private String countryCode;

    // ...
}

with this custom constraint

@Constraint(validatedBy = YourCustomAddressValidator.class)
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.FIELD, ElementType.METHOD, ElementType.ANNOTATION_TYPE})
public @interface YourCustomAddressConstraint {
    String message() default "Invalid address";
    Class<?>[] groups() default {};
    Class<? extends Payload>[] payload() default {};
}

which is validated by this validator

public class YourCustomAddressValidator implements ConstraintValidator<YourCustomAddressConstraint, Address> {

    @Override
    public void initialize(YourCustomAddressConstraint constraintAnnotation) {
        // ...
    }

    @Override
    public boolean isValid(Address address, ConstraintValidatorContext context) {
        var postalCode = address.getPostalCode();
        var countryCode = address.getCountryCode();

        if (!matchesYourRegex(postalCode, countryCode)) {
            return false;
        }

        return true;
    }

    private static boolean matchesYourRegex(String postalCode, String countryCode) {
        // TODO: Your logic here.
    }

}

Answer 2

This will very much depend on your use case and data. For example, where does your application store the Locale of a given user? Is this part of the user meta data or is this send per request (in a client/server application). There is no generic solution to this, you will have to code the handling of the user Locale.

Once you know where your user Locale is stored, you need to somehow get it into your ConstraintValidator implementation for ZipCode in order to select the right regular expression for this. One way to do this could be to use a ThreadLocal to set the current user Locale