Validate a string type against a list of dynamic values

dkarr · **Joined:** Mon Aug 07, 2006 6:22 pm **Posts:** 67

I've had Hibernate Validator working in my API framework for a while now, and it works well enough for comparing an instance value against "static" constraints.

Someone on my team has an instance variable whose legal values are defined by a list of values obtained from a properties file. This doesn't fit with what's available here. For now, I've told him to just do the manual validation at the point where we do the "simple" validation, and just cause it to manually construct a "ConstraintViolation" object (and subclass, being that it's an interface) and add it to any list that the simple validation produces.

I'd like to know what other people have done in this situation, as I can't imagine this is a rare thing to do.

Gunnar · **Joined:** Sat Jan 24, 2009 12:46 pm **Posts:** 388

Hi, you could have a string constraint whose validator implementation reads a whitelist with allowed values from a text file. E.g. like so:

Code:

@Target({ FIELD, METHOD, PARAMETER, ANNOTATION_TYPE, TYPE_USE })
@Retention(RUNTIME)
@Constraint(validatedBy = InWhitelistValidator.class)
@Documented
@Repeatable(List.class)
public @interface InWhitelist {

    String message() default "{com.example.InWhitelist.message}";
    Class<?>[] groups() default { };
    Class<? extends Payload>[] payload() default { };

    String whitelistFile();

    @Target({ FIELD, METHOD, PARAMETER, ANNOTATION_TYPE })
    @Retention(RUNTIME)
    @Documented
    @interface List {
        InWhitelist[] value();
    }
}

Code:

public class InWhitelistValidator implements ConstraintValidator<InWhitelist, String> {

    private Set<String> whitelist;

    @Override
    public void initialize(InWhitelist constraintAnnotation) {
        this.whitelist = readFile( constraintAnnotation.whitelistFile() ).toSet(); // read contents of given whitelist file
    }

    @Override
    public boolean isValid(String object, ConstraintValidatorContext constraintContext) {
        if ( object == null ) {
            return true;
        }

        return whitelist.contains( object );
    }
}

You then can create constraints for specific "enums" via constraint composition (http://docs.jboss.org/hibernate/stable/ ... omposition):

Code:

@Target({ FIELD, METHOD, PARAMETER, ANNOTATION_TYPE, TYPE_USE })
@Retention(RUNTIME)
@Constraint(validatedBy = {})
@Documented
@InWhitelist(whitelistFile="currency-codes.txt")
@Repeatable(List.class)
public @interface ValidCurrencyCode {

    String message() default "{com.example.ValidCurrencyCode.message}";
    Class<?>[] groups() default { };
    Class<? extends Payload>[] payload() default { };

    @Target({ FIELD, METHOD, PARAMETER, ANNOTATION_TYPE })
    @Retention(RUNTIME)
    @Documented
    @interface List {
        ValidCurrencyCode[] value();
    }
}

Hth,

--Gunnar