How do I parse a x-www-url-encoded string into a Map[String, String] using Lift?

Question

From Lift, I'm getting a string of the form

TOKEN=EC%2d454178600K772032D&TIMESTAMP=2011%2d06%2d29T13%3a10%3a58Z&CORRELATIONID=cbd56e97cad38&ACK=Success&VERSION=64&BUILD=1936884

from the response of an HTTP request.

Although it's probably ultra-trivial, I can't find the Lift function that parses this into a nice Map[String, String]. Any help?

Microminiaturization

Answer 1

From Lift's Req.scala:

// calculate the query parameters
lazy val queryStringParam:  (List[String], Map[String, List[String]]) = {
  val params: List[(String, String)] =
    for {
      queryString <- request.queryString.toList
      nameVal <- queryString.split("&").toList.map(_.trim).filter(_.length > 0)
      (name, value) <- nameVal.split("=").toList match {
        case Nil => Empty
        case n :: v :: _ => Full((urlDecode(n), urlDecode(v)))
        case n :: _ => Full((urlDecode(n), ""))
      }} yield (name, value)

        val names: List[String] = params.map(_._1).distinct
  val nvp: Map[String, List[String]] = params.foldLeft(Map[String, List[String]]()) {
    case (map, (name, value)) => map + (name -> (map.getOrElse(name, Nil) ::: List(value)))
  }

  (names, nvp)
}

Liquidambar

Thank you very much David. I will then copy from this snippet. – Microminiaturization

Answer 2

I haven't seen any Lift's implementation for that. You can achieve this with something like this:

val input = "TOKEN=EC%2d454178600K772032D&TIMESTAMP=2011%2d06%2d29T13%3a10%3a58Z&CORRELATIONID=cbd56e97cad38&ACK=Success&VERSION=64&BUILD=1936884"
val res = input.split('&') map { str =>
    val pair = str.split('=')
    (pair(0) -> pair(1))
} toMap

note: it assumes, that you have a well-formed string. In your code you should probably check if the string is ok.

Disseminule

Lift does it since it parses request parameters, which are encoded in the same way. Yes, writing your own parser for that looks easy, but I want one that is well tested and also works for the corner cases. For instance, your solution should call URLEncoder.encode(_, "UTF-8") on the broken-apart strings before putting them in the map. – Microminiaturization

You're probably looking for scala-tools.org/mvnsites/liftweb-2.0/framework/scaladocs/net/… – Disseminule

Thanks, but actually no, since the string to parse is returned to me as a response to a request I made from my back end server (to PayPal, actually). – Microminiaturization

Answer 3

I put together a small Scala library to help do this: https://github.com/theon/scala-uri

You can parse a uri and get the parameters into a Map[String,List[String]] like so:

val uri = parseUri("http://example.com?one=1&two=2").query.params

It also has a DSL for building URLs with query strings:

val uri = "http://example.com" ? ("one" -> 1) & ("two" -> 2)

Nighttime

Answer 4

scala> val queryParams = "a=4&b=5"
scala> queryParams.split("&").toList.map(_.trim).filter(_.length > 0).flatMap(x => {
    val s = x.split('=')
    Map[String, String](s(0) -> s(1))
}).toMap[String, String]

res0: scala.collection.immutable.Map[String,String] = Map(a -> 4, b -> 5)

Wherein