gitbucket / scalatra-forms   1.1.0


A library to validate and map request parameters for Scalatra.

Scala versions: 2.12


A library to validate and map request parameters for Scalatra.

Notice: This project is maintained no longer because it has been merged into Scalatra! See the Scalatra documentation to know details.

Getting Started

At first, add the following dependency into your build.sbt to use scalatra-forms.

libraryDependencies += "io.github.gitbucket" %% "scalatra-forms" % "1.1.0"

Next, add ValidationJavaScriptProvider to Bootstrap of your Scalatra application.

import io.github.gitbucket.scalatra.forms._

class ScalatraBootstrap extends LifeCycle {
  override def init(context: ServletContext) {
    context.mount(new ValidationJavaScriptProvider, "/assets/js/*")

scalatra-forms is now ready.

Define a form mapping. It's a similar to Play2, but scalatra-forms is more flexible.

import io.github.gitbucket.scalatra.forms._
case class RegisterForm(name: String, description: String)

val form = mapping(
  "name"        -> text(required, maxlength(40)), 
  "description" -> text()

Next, create a servlet (or filter) which extends ScalatraServlet (or ScalatraFilter). It also mixed in FormSupport or ClientSideValidationFormSupport. The object which is mapped request parameters is passed as an argument of action.

class RegisterServlet extends ScalatraServlet with ClientSideValidationFormSupport {
  post("/register", form) { form: RegisterForm =>

In the HTML, you have to do two things below.

  • Add <script> to import jQuery which is required by validation.js
  • Add <script> to import validation.js which helps client side validation provided by ValidationJavaScriptProvider
  • Add validation="true" to your <form>

scalatra-forms registers a submit event listener to validate form contents. This listener posts all the form contents to FORM_ACTION/validate. This action is registered by scalatra-forms automatically to validate form contents. It returns validation results as JSON.

In the client side, scalatra-forms puts error messages into span#error-FIELD_NAME.

<script src=""></script>
<script src="/assets/js/validation.js"></script>
<form method="POST" action="/register" validation="true">
  Name: <input type="name" type="text">
  <span class="error" id="error-name"></span>
  Description: <input type="description" type="text">
  <span class="error" id="error-description"></span>
  <input type="submit" value="Register"/>

Custom Validation

You can create custom Constraint.

def identifier: Constraint = new Constraint(){
  override def validate(name: String, value: String): Option[String] =
      Some(s"${name} contains invalid character.")
    } else {

val form = mapping(
  "name"        -> text(required, identifier), 
  "description" -> text()

You can also create multi field validator by overriding validate(String, String, Map[String, String]). It's possible to look up other field value via params.

Other way to create multi field validator is calling verifying for mapping. You can give the function yo validate the mapped case class. This function takes the mapped value and returns Seq[(String, String)] which contains errors or Nil.

val form = mapping(
  "reason"      -> number(required), 
  "description" -> optional(text)
)(ReasonForm.apply).verifying { value =>
  if(value.reason == 4 && value.descripsion){
    Seq("description" -> "If reason is 'Other' then description is required.")
  } else {


For the Ajax action, use ajaxGet or ajaxPost instead of get or post. Actions which defined by ajaxGet or ajaxPost return validation result as JSON response.

class RegisterServlet extends ScalatraServlet with ClientSideValidationFormSupport {
  ajaxPost("/register", form) { form: RegisterForm =>

In the client side, you can render error messages using displayErrors().

  $.ajax($(this).attr('action'), {
    type: 'POST',
    data: {
      name       : $('#name').val(),
      description: $('#description').val()
  .fail(function(data, status){

Release Notes

1.1.0 - 25 Nov 2016

  • Scalatra 2.5.0 and Scala 2.12 support

1.0.0 - 31 Dec 2015

  • Move to GitBucket organization.
  • Change group id and package name to io.github.gitbucket.
  • Add put(), delete(), ajaxPut() and ajaxDelete() to ClientSidevalidationFormSupport.

0.2.0 - 18 Nov 2015

  • Fix performance issue

0.1.0 - 9 Jul 2014

  • Support Scala 2.11 and Scalatra 2.3

0.0.14 - 19 Feb 2014

  • Bug fix about form state after after validation succeeded.

0.0.13 - 2 Feb 2014

  • Bug fix for long value type.

0.0.12 - 29 Dec 2013

  • Formatting (such as %s) is available in custom messages as same as default messages.

0.0.11 - 12 Dec 2013

  • Fix dummy() bug.

0.0.10 - 10 Dec 2013

  • Add long value type.
  • Fix list bug for un-nested properties.

0.0.9 - 6 Dec 2013

  • Add dummy value type.

0.0.8 - 14 Nov 2013

  • Fix nested property handling problem.
  • Fix verifying() for MappingValueType and remove MappingConstraint instead of it.
  • Add length constraint.

0.0.7 - 12 Nov 2013

  • Add MappingConstraint to validate converted object by MappingValueType.

0.0.6 - 8 Nov 2013

  • Add list() mapping for SingleValueType.
  • ValidationJavaScriptProvider adds Content-Type header for validation.js.
  • Fix to run parent validations before number checking.

0.0.5 - 3 Nov 2013

  • Add oneOf() constraint which checks whether the value is one of specified strings.
  • Fix to retrieve error message for number() and double() from ResourceBundle.

0.0.4 - 2 Nov 2013

  • Add double() and date() mapping.
  • Add I18N support for error messages.

0.0.3 - 18 Oct 2013

  • Add ValidationJavaScriptProvoider.
  • Add list() mapping for List property.

0.0.2 - 10 Aug 2013

  • Improved nested property support.
  • Add validate(String, String, Map[String, String]) to Constraint. It makes possible to access other parameter in single field validation.
  • Add verify() to MappingValueType which validates the mapped instance.

0.0.1 - 04 Aug 2013

  • This is the first public release.