Пример парсера URL на parboiled2 (из доклада "No more regular expressions", см. https://skillsmatter.com/skillscasts/5847-no-more-regular-expressions)

url-parsers.scala

import org.parboiled2._
import org.parboiled2.CharPredicate._

class URLParser(val input: ParserInput) extends Parser {

  def URL = rule { URLPattern ~> UrlParts }

  def URLPattern = rule { Scheme ~ "://" ~ Host ~ Port ~ Path ~ QueryParams }

  def QueryParams = rule { '?' ~ oneOrMore(QPPair).separatedBy('&') ~> (kvs => Map(kvs: _*)) }

  def QPPair = rule { capture(oneOrMore(Alpha)) ~ '=' ~ capture(oneOrMore(Alpha)) ~> ((k: String, v: String) => (k, v)) }

  def Path = rule { '/' ~ capture(oneOrMore(oneOrMore(Alpha)).separatedBy('/')) }

  def Port = rule { optional(':' ~ capture(oneOrMore(Digit)) ~> (_.toInt)) }

  def Host = rule { capture(oneOrMore(Alpha ++ ".-_")) }

  def Scheme = rule { capture(oneOrMore(Alpha)) }
}

case class UrlParts(scheme: String, host: String, port: Option[Int], path: String, queryParams: Map[String,String])

// For test:
// new URLParser("https://url.spec.whatwg.org:80/foo?foo=bar").URL.run() --> scala.util.Try[UrlParts] = Success(UrlParts(https,url.spec.whatwg.org,Some(80),foo,Map(foo -> bar)))