squbs Validation provides a Akka HTTP directive for data validation by using Accord Validation Library. Currently this is Scala only feature, Java version will be added in future versions of squbs.


Add the following dependencies to your build.sbt or scala build file:

"org.squbs" %% "squbs-pattern" % squbsVersion,
"com.wix" %% "accord-core" % "0.7.1"


Given that an implicit Person validator is in the scope, validate directive can be used as other Akka HTTP Directives:

import ValidationDirectives._
validate(person) { 


Here is a sample Person class and corresponding validator (please see Accord Validation Library for more validator usage examples).

case class Person(firstName: String, lastName: String, middleName: Option[String] = None, age: Int)

object SampleValidators {

  import com.wix.accord.dsl._
  implicit val personValidator = com.wix.accord.dsl.validator[ Person ] { p =>
                p.firstName as "First Name" is notEmpty
                p.lastName as "Last Name" is notEmpty
                p.middleName.each is notEmpty // If exists, should not be empty.
                p.age should be >= 0

Now you can use the validate directive as follows:

def route =
 path("person") {
   post {
     entity(as[Person]) { person =>
       import ValidationDirectives._
       // importing the person validator
       import SampleValidators._
       validate(person) {
           complete {

If a validation rejection happens, a 400 Bad Request is returned with the response body containing the comma separated list of field(s) causing validation rejection. Using the above example, if the request body contains the following:

    "firstName" : "John",
    "lastName" : "",
    "age" : -1

then, the response body would contain:

Last Name, age