Overview

Akkurate is a validation library taking advantage of the expressive power of Kotlin. No need
for 30+ annotations or complicated custom constraints; write your validation code in Kotlin with a beautiful declarative API.

Designed from scratch to handle complex business logic, its role is to help you write qualitative and maintainable validation code.

Showcase

Here's how you can constrain a book and its list of authors.

// Define your classes

@Validate
data class Book(
    val title: String,
    val releaseDate: LocalDateTime,
    val authors: List<Author>,
)

@Validate
data class Author(val firstName: String, val lastName: String)

// Write your validation rules

val validateBook = Validator<Book> {
    // First the property, then the constraint, finally the message.
    title.isNotEmpty() otherwise { "Missing title" }

    releaseDate.isInPast() otherwise { "Release date must be in past" }

    authors.hasSizeBetween(1..10) otherwise { "Wrong author count" }

    authors.each { // Apply constraints to each author
        (firstName and lastName) {
            // Apply the same constraint to both properties
            isNotEmpty() otherwise { "Missing name" }
        }
    }
}

// Validate your data

when (val result = validateBook(someBook)) {
    is Success -> println("Success: ${result.value}")
    is Failure -> {
        val list = result.violations
            .joinToString("\n") { "${it.path}: ${it.message}" }
        println("Failures:\n$list")
    }
}

Notice how each constraint applied to a property can be read like a sentence. This code:

title.isNotEmpty() otherwise { "Missing title" }

can be read:

Check if 'title' is not empty otherwise write "Missing title".

Features

Beautiful DSL and API. Write crystal clear validation code and keep it DRY. Use loops and conditions when needed; forget about annotation hell.
Bundled with all the essential constraints. Write custom constraints for your business logic and nothing more. The rest? It's on us!
Easily and highly extendable. No need to write verbose code to create custom constraints, within Akkurate they're as simple as a lambda with parameters.
Contextual and asynchronous. Query sync/async data sources whenever you need to, like a database, or a REST API. Everything can happen inside validation.
Integrated with your favorite tools. Validate your data within any popular framework, we take care of the integrations for you.
Code once, deploy everywhere. Take advantage of Kotlin Multiplatform; write your validation code once, use it both for front-end and back-end usages.
Testable out of the box. Finding how to test your validation code shouldn't be one of your tasks. You will find all the tools you need to write good tests.

Last modified: 27 February 2024