How to validate number string as digit with hibernate?

Question

Which annotations would I have to use for Hibernate Validation to validate a String to apply to the following:

//should always have trimmed length = 6, only digits, only positive number
@NotEmpty
@Size(min = 6, max = 6)
public String getNumber { 
   return number.trim();
}

How can I apply digit validation? Would I just use @Digits(fraction = 0, integer = 6) here?

Answer 1

You could replace all your constraints with a single @Pattern(regexp="[\\d]{6}"). This would imply a string of length six where each character is a digit.

Answer 2

You can also create your own hibernate validation annotation.
In the example below I created a validation annotation with name EnsureNumber. Fields with this annotation will validate with the isValid method of the EnsureNumberValidator class.

@Constraint(validatedBy = EnsureNumberValidator.class)
@Target({ ElementType.FIELD })
@Retention(RetentionPolicy.RUNTIME)
public @interface EnsureNumber {

    String message() default "{PasswordMatch}";

    Class<?>[] groups() default {};

    Class<? extends Payload>[] payload() default {};

    boolean decimal() default false;

}

public class EnsureNumberValidator implements ConstraintValidator<EnsureNumber, Object> {
    private EnsureNumber ensureNumber;

    @Override
    public void initialize(EnsureNumber constraintAnnotation) {
        this.ensureNumber = constraintAnnotation;
    }

    @Override
    public boolean isValid(Object value, ConstraintValidatorContext context) {
        // Check the state of the Adminstrator.
        if (value == null) {
            return false;
        }

        // Initialize it.
        String regex = ensureNumber.decimal() ? "-?[0-9][0-9\\.\\,]*" : "-?[0-9]+";
        String data = String.valueOf(value);
        return data.matches(regex);
    }

}

You can use it like this,

@NotEmpty
@Size(min = 6, max = 6)
@EnsureNumber
private String number1;

@NotEmpty
@Size(min = 6, max = 6)
@EnsureNumber(message = "Field number2 is not valid.")
private String number2;

@NotEmpty
@Size(min = 6, max = 6)
@EnsureNumber(decimal = true, message = "Field number is not valid.")
private String number3;

Answer 3

The @Digits annotation can be used to enforce that a string is a number in a given range:

@NotEmpty
@Digits(integer = 6, fraction = 0)
public String getNumber { 
   return number.trim();
}

Per the @Digits Javadocs:

The annotated element must be a number within accepted range.

Supported types are:

• BigDecimal
• BigInteger
• CharSequence
• byte, short, int, long, and their respective wrapper types

null elements are considered valid.