Accord: A sane validation library for Scala

Build Status Gitter Maven Central Scala.js



Accord is a validation library written in and for Scala. Compared to JSR 303 and Scalaz validation it aims to provide the following:

  • Composable: Because JSR 303 is annotation based, validation rules cannot be composed (annotations cannot receive other annotations as parameters). This is a real problem with some Scala features, for example Options or collections. Accord's validation rules are trivially composable.
  • Simple: Accord provides a dead-simple story for validation rule definition by leveraging macros, as well as the validation call site (see example below).
  • Self-contained: Accord is macro-based but completely self-contained, and consequently only relies on the Scala runtime and reflection libraries.
  • Integrated: Other than providing its own DSL and matcher library, Accord is designed to easily integrate with the larger Scala ecosystem, and provides out-of-the-box support for Scala.js, as well as integration modules for Spring Validation, Specs2 and ScalaTest.

For proper user guide and additional documentation please refer to project website.

Accord is developed and used at and distributed under the Apache License, Version 2.0, which basically means you can use and modify it freely. Feedback, bug reports and improvements are welcome!


Accord is still fairly rudimentary, and there's plenty of improvements to be made:

  • The 0.8 milestone lists the planned improvements for the next release.
  • Some future plans/ideas:
    • Performance benchmarks
    • Elide DSL implicit invocations from resulting tree for better performance and smaller code
    • Add syntax for custom violation message overrides (e.g. p.firstName is notEmpty as "no first name!")
    • Support custom violation types (e.g. p.firstName is notEmpty as MyServerError( code = -3 ))
    • Full-blown i18n support (need feedback on this)

Ideas and feature requests welcome! You can join the fun on our Gitter channel, report an issue or contact the maintainer directly.