Query parameter as List - scala

Question

I want to have a way access certain query parameters for all of my requests. An example query would be something like:
http://api.mysite.com/accounts/123?include=friends,photos
Where I want to get access to the comma separated list of include relationships.
As far as I could tell, the following doesn't work and will look at the include list as a single string:
// routes.txt
GET /accounts/:id controllers.AccountsController.get(id: Int, include: Seq[String])
This is how I am currently doing it, but I was hoping there was a cleaner way.
// routes.txt
GET /accounts/:id controllers.AccountsController.get(id: Int, include: Option[String])
// AccountsController.scala
def get(id: Int, include: Option[String]) = Action {
// Convert the option to a set
val set = if (include.isDefined) include.get.split(",").toSet else Set()
}

Answer 1

The proper way to do it (already supported by Play) would be to use repeated key-values in the query string, i.e.:
http://api.mysite.com/accounts/123?include=friends&include=photos
That would automatically bind Seq("friends", "photos") to include in that route. This has the advantage of being able to use commas within keys, and is consistent with the common usage of query string parameters.
Alternatively, you can create a custom QueryStringBindable[List[String]] that can handle a comma-separated list. Something like:
object QueryStringBinders {
implicit def listBinder(key: String)(implicit stringBinder: QueryStringBindable[String]) = {
new QueryStringBindable[List[String]] {
override def bind(key: String, params: Map[String, Seq[String]]): Option[Either[String, List[String]]] =
stringBinder.bind(key, params).map(_.right.map(_.split(",").toList))
override def unbind(key: String, strings: List[String]): String =
s"""$key=${strings.mkString(",")}"""
}
}
}
Then you would use PlayKeys.routesImport += "QueryStringBinders._" within build.sbt to use it (or whatever the fully qualified package name is). Using a QueryStringBindable would make the split logic reusable, with minimal boilerplate.

Answer 2

As, #m-z said the proper way to use is repeated key-values in query string like: http://api.mysite.com/accounts/123?include=friends&include=photos
and in you action you can access query string with queryString method as well i.e
your route will look like this:
GET /accounts/:id controllers.AccountsController.get(id: Int)
and in your controller:
// AccountsController.scala
def get(id: Int) = Action { request =>
// the `request.queryString` will give you Map[String, Seq[String]] i.e all they keys and their values
val includes = request.queryString.getOrElse("include", Nil)
}