@NotZero Annotation for long type variable in Java Springboot

Question

I am trying to build a @NotZero annotation for long & float type variables. This should work like @NotBlank for strings with non-zero constraints.

I have tried @Min and @Numeric annotation but these do not suffice my requirement. Regex doesn't seem to be of any help in this case not being a string. How can I add a custom function which checks if the input number is not zero and use that as annotation.

My number can take values like 0.001, 25, 36.25 etc. any strictly positive long & float values.

Answer 1

If you're using hibernate, consider a custom validator: https://www.baeldung.com/spring-mvc-custom-validator

The annotation definition:

@Documented
@Constraint(validatedBy = NonZeroFloatValidator.class)
@Target( { ElementType.METHOD, ElementType.FIELD })
@Retention(RetentionPolicy.RUNTIME)
public @interface NonZeroFloatConstraint {
    String message() default "Float value is zero";
    Class<?>[] groups() default {};
    Class<? extends Payload>[] payload() default {};
}

The validator logic:

public class NonZeroFloatValidator implements ConstraintValidator<NonZeroFloatConstraint, Float>
{    
    @Override
    public void initialize(NonZeroFloatConstraint cons) {}

    @Override
    public boolean isValid(Float f, ConstraintValidatorContext cxt)
    {
        return Float.compare(f, 0.0f) != 0;
    }
}

You would need another constraint for doubles, but the pattern is the same.