Better way of using JSR303 annotations in Spring MVC to check whitespaces only

Question

Im using a custom validation on a textbox that checks if entered sentence contains only white spaces The code is as below

@Retention(value = RetentionPolicy.RUNTIME)
@javax.validation.Constraint(validatedBy = SmsMessageContent.SmsMessageContentValidator.class)
@Target({ METHOD, FIELD, ANNOTATION_TYPE })
@Documented
public @interface SmsMessageContent {


    public class SmsMessageContentValidator implements
            ConstraintValidator<SmsMessageContent, String> {



        @Override
        public void initialize(final SmsMessageContent constraintAnnotation) {

        }

        @Override
        public boolean isValid(final String value,
                final ConstraintValidatorContext context) {

            if (value == null)
                return true;

            try {
                   if (value.matches("^\\s*$")) {
context.buildConstraintViolationWithTemplate("{message.sms.content.not.empty}")
.addConstraintViolation();
                    context.disableDefaultConstraintViolation();
                    return false;
                }
            } catch (Exception e) {
                log.error(e.getMessage());
            }

                 }


    }

}

The above annotation im using in another class as

public class SmsMessageForm {

    @SmsMessageContent
    private String smsChannelContent = "";

Is there any annotation in JSR303 or JSR330 that can be used directly on

private String smsChannelContent = "";

instead of writing another annotation like what I have used to check for a whitespaces only?

Answer 1

I believe @Pattern does just that

@Pattern("^\\s*$")
private String smsChannelContent = "";

The javadoc states

The annotated String must match the following regular expression.

So use the pattern you need. I wasn't sure if you wanted to check against whitespace or for whitespace.