Convert query string to map in scala - scala

Question

I have a query string in this form:
val query = "key1=val1&key2=val2&key3=val3
I want to create a map with the above key/value pairs. So far I'm doing it like this:
//creating an iterator with 2 values in each group. Each index consists of a key/value pair
val pairs = query.split("&|=").grouped(2)
//inserting the key/value pairs into a map
val map = pairs.map { case Array(k, v) => k -> v }.toMap
Are there any problems with doing it like I do? If so, is there some library I could use to do it?

Answer 1

Here is an approach using the URLEncodedUtils:
import java.net.URI
import org.apache.http.client.utils.URLEncodedUtils
import org.apache.http.{NameValuePair => ApacheNameValuePair}
import scala.collection.JavaConverters._
import scala.collection.immutable.Seq
object GetEncodingTest extends App {
val url = "?one=1&two=2&three=3&three=3a"
val params = URLEncodedUtils.parse(new URI(url), "UTF_8")
val convertedParams: Seq[ApacheNameValuePair] = collection.immutable.Seq(params.asScala: _*)
val scalaParams: Seq[(String, String)] = convertedParams.map(pair => pair.getName -> pair.getValue)
val paramsMap: Map[String, String] = scalaParams.toMap
paramsMap.foreach(println)
}

Answer 2

Assuming the query string you are working with is as simple as you showed, the use of grouped(2) is a great insight and gives a pretty elegant looking solution.
The next step from where you're at is to use the under-documented Array::toMap method:
val qs = "key=value&foo=bar"
qs.split("&|=") // Array(key, value, foo, bar)
.grouped(2) // <iterator>
.map(a => (a(0), a(1))) // <iterator>
.toMap // Map(key -> value, foo -> bar)
grouped(2) returns an Iterator[Array[String]], that's a little harder to follow because iterators don't serialize nicely on the Scala console.
Here's the same result, but a bit more step-by-step:
val qs = "key=value&foo=bar"
qs.split("&") // Array(key=value, foo=bar)
.map(kv => (kv.split("=")(0), kv.split("=")(1))) // Array((key,value), (foo,bar))
.toMap // Map(key -> value, foo -> bar)
If you want a more general solution for HTTP query strings, consider using a library for URL parsing.