Configuration

A configuration of Validity has two things: the messages of the violations, and the clock that says what “now” is. Every validation uses one.

Once, at startup

Validity.configure { } replaces the default configuration, the one every validation uses unless it is given another:

fun main() {
    Validity.configure {
        messages {
            required = "é obrigatório"
            minLength = "deve ter pelo menos {min} caracteres"
            brazil { cpf = "CPF inválido" }
        }
        clock = Clock.system(ZoneId.of("America/Sao_Paulo"))
    }

    // ... start the application
}

Each call starts from the built-in defaults, so a second call undoes the first. Call it once, before the first validation.

For one call

Validity { } creates a configuration that starts from the default one and changes only what its block says. Pass it to validate: the default configuration does not change, so other requests keep theirs.

val portuguese = Validity {
    messages {
        minLength = "deve ter pelo menos {min} caracteres"
        email = "deve ser um e-mail válido"
    }
}

User(name = "A", email = "ana@", age = null).validate(portuguese).violations

Path	Message	Code
`name`	deve ter pelo menos 2 caracteres	`minLength`
`email`	deve ser um e-mail válido	`email`

The codes stay the same in every language, which is what lets programs ignore the messages. Every entry takes one: validate(validity), validateBlocking(validity), the OrThrow versions, and, for a ContextualValidatable, validate(context, validity). The configuration reaches the nested objects and elements too.

Common uses

One language per request

Build one Validity per language at startup, and pick it from the Accept-Language of the request:

val byLanguage = mapOf("pt" to portuguese, "es" to spanish)

order.validate(byLanguage[language] ?: Validity { })

A fixed clock in tests

Rules about time read the clock of the configuration, so a test can fix “now” for one call without touching the default:

val validity = Validity { clock = Clock.fixed(Instant.parse("2026-11-02T12:00:00Z"), ZoneOffset.UTC) }

subscription.validate(validity)

The time zone of a user

“Today” depends on the zone. Give the call the clock of the user’s zone:

booking.validate(Validity { clock = Clock.system(user.zone) })

Validity { } builds its configuration when it is created, on top of the default of that moment. Create the ones you reuse, such as one per language, after Validity.configure, and keep them in a value.

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Writing rules

Beyond the object

Reading the result

For AI agents

Configuration

Once, at startup

For one call

Common uses

​Once, at startup

​For one call

​Common uses

Once, at startup

For one call

Common uses