Validating double and float values using Hibernate Validator - bean validation

I have avoided the double and the float types and implemented a custom validator that could validate a BigDecimal value based on the precision and the scale.

The constraint descriptor.

package constraintdescriptor;

import constraintvalidator.BigDecimalRangeValidator;
import java.lang.annotation.Documented;
import static java.lang.annotation.ElementType.ANNOTATION_TYPE;
import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.ElementType.METHOD;
import java.lang.annotation.Retention;
import static java.lang.annotation.RetentionPolicy.RUNTIME;
import java.lang.annotation.Target;
import javax.validation.Constraint;
import javax.validation.Payload;

@Target({METHOD, FIELD, ANNOTATION_TYPE})
@Retention(RUNTIME)
@Constraint(validatedBy = BigDecimalRangeValidator.class)
@Documented
public @interface BigDecimalRange {
    public String message() default "{java.math.BigDecimal.range.error}";
    public Class<?>[] groups() default {};
    public Class<? extends Payload>[] payload() default {};

    long minPrecision() default Long.MIN_VALUE;
    long maxPrecision() default Long.MAX_VALUE;
    int scale() default 0;
}

---

The constraint validator.

package constraintvalidator;

import constraintdescriptor.BigDecimalRange;
import java.math.BigDecimal;
import javax.validation.ConstraintValidator;
import javax.validation.ConstraintValidatorContext;

public final class BigDecimalRangeValidator implements ConstraintValidator<BigDecimalRange, Object> {

    private long maxPrecision;
    private long minPrecision;
    private int scale;

    @Override
    public void initialize(final BigDecimalRange bigDecimalRange) {
        maxPrecision = bigDecimalRange.maxPrecision();
        minPrecision = bigDecimalRange.minPrecision();
        scale = bigDecimalRange.scale();
    }

    @Override
    public boolean isValid(final Object object, final ConstraintValidatorContext cvc) {
        boolean isValid = false;

        if (object == null) { // This should be validated by the not null validator (@NotNull).
            isValid = true;
        } else if (object instanceof BigDecimal) {
            BigDecimal bigDecimal = new BigDecimal(object.toString());
            int actualPrecision = bigDecimal.precision();
            int actualScale = bigDecimal.scale();
            isValid = actualPrecision >= minPrecision && actualPrecision <= maxPrecision && actualScale <= scale;

            if (!isValid) {
                cvc.disableDefaultConstraintViolation();
                cvc.buildConstraintViolationWithTemplate("Precision expected (minimun : " + minPrecision + ", maximum : " + maxPrecision + "). Maximum scale expected : " + scale + ". Found precision : " + actualPrecision + ", scale : " + actualScale).addConstraintViolation();
            }
        }

        return isValid;
    }
}

This could be extended for other types as well, as and when required.

---

And finally in the bean, the property of the type BigDecimal could be annotated by the @BigDecimalRange annotation as follows.

package validatorbeans;

public final class WeightBean {

    @BigDecimalRange(minPrecision = 1, maxPrecision = 33, scale = 2, groups = {ValidationGroup.class}, message = "The precision and the scale should be less than or equal to 35 and 2 respectively.")
    private BigDecimal txtWeight; // Getter and setter.

    public interface ValidationGroup {}
}

You can use the annotation, but you might get false results depending. This is a general problem with doubles and imo in many cases _Double_s should be avoided. Maybe switching to a different type is the best solution? BigDecimal for example?

You can also use @Digits from the hibernate validator API as well

@Digits(integer = 10 /*precision*/, fraction = 2 /*scale*/)

If you have switched to BigDecimal (or BigInteger), you could use @DecimalMin or @DecimalMax. But this is still no solution for float or double.