JarCasting
Kaval
This is a Kotlin multi-platform library to validate your model.
Why
The goal is to find the right balance between conciseness, expressiveness, and composability to validate POJO.
Or you can see it as a validation DSL.
Example
We want to validate this model
data class User(
val firstName: String,
val lastName: String,
val address: Address?
)
data class Address(
val line1: String,
val line2: String,
val zipCode: Int,
val city: String
)
We can validate the Address with these constraints:
- line1: not blank, and length <= 255
- line2: length <= 255
- zipCode: > 0
- city: not blank
val addressValidator: Validator<Address> =
reflectValidator {
Address::line1 { notBlank and maxLength(255) }
Address::line2 { maxLength(255) }
Address::zipCode { greaterThan(0) }
Address::city { notBlank }
}
And the User with these constraints:
- firstName: not blank, and length <= 128
- lastName: length <= 255
- address: see above
val userValidator: Validator<User> =
reflectValidator {
User::firstName { notBlank and maxLength(128) }
User::lastName { maxLength(255) }
User::address { nullOr { Address.validator } }
}
Now we can use the validators:
val user = User(
firstName = "",
lastName = "x".repeat(500),
address = Address(
line1 = "",
line2 = "",
zipCode = -1,
city = ""
)
)
val result: ValidationResult = userValidator.validate(user)
println(result)
// Invalid:
// - [firstName] requires to be not blank
// - [lastName.length] requires to be lower or equals to 255, got 500
// - [address.line1] requires to be not blank
// - [address.zipCode] requires to be greater than 0, got -1
// - [address.city] requires to be not blank should be Valid
Modules
- kaval-core: the core, start here
- kaval-reflect: add a validator using Kotlin reflection
- kaval-kotest: add custom matchers for kotest
- kaval-arrow: integration with the awesome Arrow library
- some samples
