How to check decimal places

[theseeker58]

I need to generate a json schema starting from a java class that have a property like this

    @XmlValue
    @DecimalMin(value = "0.01", inclusive = true)
    @Digits(integer = 18, fraction = 2)
    protected BigDecimal value;

the tool generates this

        "value" : {
          "type" : "number",
          "minimum" : 0.01
        }

Please who knows how can the fraction be checked?
TIA

[CarstenWickner]

Hi @theseeker58,

The fraction could be enforced via the multipleOf keyword (if you don't mind possible trailing zeros), which you can set like this (refer to documentation):

configBuilder.forFields().withNumberMultipleOfResolver(field -> Optional
            .ofNullable(field.getAnnotationConsideringFieldAndGetterIfSupported(Digits.class))
            .map(annotation -> BigDecimal.ONE.divide(BigDecimal.TEN.pow(annotation.fraction()), annotation.fraction(), RoundingMode.FLOOR)).orElse(null));

The maximum number of digits before the decimal separator could similarly be enforced as an exclusiveMaximum (refer to documentation) like this:

configBuilder.forFields().withNumberExclusiveMaximumResolver(field -> Optional
            .ofNullable(field.getAnnotationConsideringFieldAndGetterIfSupported(Digits.class))
            .map(annotation -> BigDecimal.TEN.pow(1 + annotation.integer())).orElse(null));

That should produce output like the following:

        "value" : {
          "type" : "number",
          "minimum" : 0.01,
          "exclusiveMaximum": 1000000000000000000,
          "multipleOf": 0.01
        }

Beyond these, I don't think the JSON Schema Specification has particular keywords for the allowed number of digits before and after the decimal separator.

[theseeker58]

Thank you @CarstenWickner for your quick reply,
Since I use the library as maven plugin, I guess I have to implement the Module interface, right?
Another question please. Is it possible to apply the restriction only for specific field/fields? This one contains Euros. Another field can contain other currencies up to 5 decimal digits.
TIA

[theseeker58]

Thank you @CarstenWickner
I have implemented the Module interface and everything works right. The only change I made is the use of the overloaded pow method that accepts a MathContext, otherwise I was getting an ArithmeticException, Invalid operation, due to a negative exponent.
Please, let me know if the fraction can be enforced only for a specific field.
Cheers

[CarstenWickner]

I've adjusted my proposal above to avoid the negative input to the pow() method.
That should hopefully do it.

[theseeker58]

Sorry, my fault,
actually I realised that through Digits.class the fraction is dinamically read from the bean balidation, therefore it's perfect in that way.
Cheers