Getting HAL style links for HATEOAS to map correctly to JSON in Scala. Assumes you're using json4s and Jackson. I'm using the below code with Scalatra -- my servlets have the 'JacksonJsonSupport' trait mixed in

Hateoas.scala

//package object full o' utility functions for creating some HAL-style HATEOAS links
package object Hateoas{
  //could add an additional field specifying MIME-type, for example
  case class Link(href: String, method: String)
  type HateoasLinks = Map[String, Link]
  //case class for a response containing a Collection of items
  case class ListResponse(_links: HateoasLinks, _embedded: Map[String, List[Any]])
  
  object HateoasLinkFactory{
    //could (should) add a function for generating a "custom" action link
    def createSelfLink(uri: String) = {
      ("self" -> new Link(uri, "GET"))
    }
    //create Create!
    def createCreateLink(uri: String) = {
      ("create" -> new Link(uri, "POST"))
    }

    def createUpdateLink(uri: String) = {
      ("update" -> new Link(uri, "PUT"))
    }

    def createDeleteLink(uri: String) = {
      ("delete" -> new Link(uri, "DELETE"))
    }
  }
}

usage.scala

//feed the output of this function into your Json serializer
def addLinks(myData: MyData, accessLevel: String, serviceUri: String) = {
    val elementUri: String = serviceUri + "/" + myData.id.toString
    //Assume MyData has a field called _links of type HateoasLinks initialized to an empty Map
    //Always add a self link
    myData._links += HateoasLinkFactory.createSelfLink(elementUri)
    accessLevel match {
      case "admin" =>
        //so let's say only an admin has access to Update or Delete a 'MyData' resource
        myData._links += HateoasLinkFactory.createUpdateLink(elementUri)
        myData._links += HateoasLinkFactory.createDeleteLink(elementUri)
      }
    myData
 }