Regular Expressions in Play2 route using UUID

[Jon Brule]

Using Play2, I am trying to map a URI that has a java.util.UUID path variable using the following code, but only received a 404. Note that the second route "tag by name" works well. I am using a custom formatter in the model (see below). Can the regular expression mapping be used with the customer formatter or readers / writers?

Thoughts?

Thanks,

Jon

Routes in question:

GET  /api/tag/$id<\d{8}-\d{4}-\d{4}-\d{4}-\d{12}>    controllers.Tags.showById(id: java.util.UUID)

GET  /api/tag/:name    controllers.Tags.showByName(name: String)

Corresponding controller:

package controllers

import play.api.mvc.{ Action, Controller }

import models.Tag

import play.api.libs.json.Json

import java.util.UUID

import play.api.libs.json.JsError

object Tags extends Controller {

  def showById(id: UUID) = Action { implicit request =>

    Tag.findById(id).map { tag =>

      Ok(Json.toJson(tag))

    }.getOrElse(NotFound)

  }

  def showByName(name: String) = Action { implicit request =>

    Tag.findByName(name).map { tag =>

      Ok(Json.toJson(tag))

    }.getOrElse(NotFound)

  }

}

And the model as such:

package models

import play.api.libs.json._

import play.api.libs.json.util._

import play.api.libs.json.Reads._

import play.api.libs.functional.syntax._

import java.util.UUID

case class Tag(

  id: Option[UUID] = None,

  name: String,

  description: String)

object Tag {

  implicit object UUIDFormat extends Format[UUID] {

    def writes(uuid: UUID): JsValue = JsString(uuid.toString())

    def reads(json: JsValue): JsResult[UUID] = json match {

      case JsString(x) => JsSuccess(UUID.fromString(x))

      case _ => JsError("Expected UUID as JsString")

    }

  }

  implicit val tagRead = (

    (__ \ 'id).readNullable[UUID] and

    (__ \ 'name).read[String] and

    (__ \ 'description).read[String])(Tag.apply _)

  implicit val tagWrite = (

    (__ \ 'id).writeNullable[UUID] and

    (__ \ 'name).write[String] and

    (__ \ 'description).write[String])(unlift(Tag.unapply))

  var tags = Set(

    Tag(Some(UUID.randomUUID()), "Tag1", "First Tag"),

    Tag(Some(UUID.randomUUID()), "Tag2", "Second Tag"))

  def add(tag: Tag) {

    val newTag = Tag(Some(UUID.randomUUID()), tag.name, tag.description)

    this.tags = this.tags + newTag

  }

  def findAll = this.tags.toList.sortBy(_.name)

  def findById(id: UUID): Option[Tag] = this.tags.find(_.id == Option[UUID](id))

  def findByName(name: String): Option[Tag] = this.tags.find(_.name == name)

}

[Jon Brule]

Using Play 2.1.1

[Manuel Bernhardt]

Hi Jon,

for this purpose, I would recommend implementing a PathBindable:

http://www.playframework.com/documentation/api/2.1.1/scala/index.html#play.api.mvc.PathBindable

If you define the PathBindable in an object, you then need to add it
to the imports of the Router, like so:

routesImport += "my.Binders._",

Hth,

Manuel

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[Jon Brule]

Manuel,

Thanks for your quick response!

Within a new application, I have implemented the following PathBinder and placed it under a util package

package util

import java.util.UUID

import play.api.mvc.PathBindable

object Binders {

  

  implicit def uuidPathBinder = new PathBindable[UUID] {

    override def bind(key: String, value: String): Either[String, UUID] = {

      Right(UUID.fromString(value))

    }

    override def unbind(key: String, id: UUID): String = {

      id.toString

    }

  }

  

}

I have added the following highlighted line to my project/Build.scala:

import sbt._

import Keys._

import play.Project._

object ApplicationBuild extends Build {

  val appName         = "things"

  val appVersion      = "1.0-SNAPSHOT"

  val appDependencies = Seq(

    // Add your project dependencies here,

    jdbc,

    anorm

  )

  val main = play.Project(appName, appVersion, appDependencies).settings(

    routesImport += "util.Binders._"      

  )

}

I have the following Model:

package models

import java.util.UUID

import play.api.libs.json.Json

import play.api.libs.json.JsSuccess

import play.api.libs.json.JsError

import play.api.libs.json.JsResult

import play.api.libs.json.JsString

import play.api.libs.json.JsValue

import play.api.libs.json.Format

case class Thing(id: Option[UUID] = None, name: String)

object Thing {

  implicit object UUIDFormat extends Format[UUID] {

    def writes(uuid: UUID): JsValue = JsString(uuid.toString())

    def reads(json: JsValue): JsResult[UUID] = json match {

      case JsString(x) => JsSuccess(UUID.fromString(x))

      case _ => JsError("Expected UUID as JsString")

    }

  }

  implicit val thingWrite = Json.writes[Thing]

  implicit val thingRead = Json.reads[Thing]

  var things = Set(

    Thing(Some(UUID.randomUUID()), "Thing1"),

    Thing(Some(UUID.randomUUID()), "Thing2"))

  def findAll = this.things.toList.sortBy(_.name)

  def findById(id: UUID): Option[Thing] = this.things.find(_.id == Option[UUID](id))

  def findByName(name: String): Option[Thing] = this.things.find(_.name == name)

}

And the following controller:

package controllers

import play.api._

import play.api.mvc._

import models.Thing

import play.api.libs.json.Json

import java.util.UUID

object Things extends Controller {

  

  def list = Action { implicit request =>

    val things = Thing.findAll

    Ok(Json.toJson(things))

  }

  

  def showById(id: UUID) = Action { implicit request =>

    Thing.findById(id).map { thing =>

      Ok(Json.toJson(thing))

    }.getOrElse(NotFound)

  }

  def showByName(name: String) = Action { implicit request =>

    Thing.findByName(name).map { thing =>

      Ok(Json.toJson(thing))

    }.getOrElse(NotFound)

  }

}

And the following routes:

# Routes

# This file defines all application routes (Higher priority routes first)

# ~~~~

# Home page

GET / controllers.Application.index

# Things

GET /api/things controllers.Things.list

GET /api/thing/$id<\d{8}-\d{4}-\d{4}-\d{4}-\d{12}> controllers.Things.showById(id: java.util.UUID)

GET /api/thing/:name controllers.Things.showByName(name: String)

# Map static resources from the /public folder to the /assets URL path

GET /assets/*file controllers.Assets.at(path="/public", file)

Unfortunately, I am still not able to resolve the fist /api/thing URI. Both the second, name-based fetch URI and the thing collection URI work fine. Can you think of something else that I have missed (I am very new to Play / Scala yet a seasoned Java developer).

In my searches, I came across bindableUUID within play.api.mvc.PathBindable under Play 2.1.1. Could I be spinning on this conversion for no reason when it might already exist? After all, I am already running 2.1.1...

Thanks so much,

Jon

[Marius Soutier]

I think you need to define the type explicitly in your Binder, e.g. type UUID = java.util.UUID.

And it helps to know what "doesn't work" mean. Do you get a compile error?

[Jon Brule]

Thanks for the reply, Marius.

I apologize for my lack of clarity. I mean to say that a URI of the form http://localhost:9000/api/thing/77de82f1-691a-4e97-880d-d662823b875e generates a 404, when a Thing record is defined as follows (used http://localhost:9000/api/thing/Thing1 to retrieve):

{

    "id": "77de82f1-691a-4e97-880d-d662823b875e",

    "name": "Thing1"

}

The routes are defined as follows:

GET / controllers.Application.index

# Things

GET /api/things controllers.Things.list

GET /api/thing/$id<\d{8}-\d{4}-\d{4}-\d{4}-\d{12}> controllers.Things.showById(id: java.util.UUID)

GET /api/thing/:name controllers.Things.showByName(name: String)

# Map static resources from the /public folder to the /assets URL path

GET /assets/*file controllers.Assets.at(path="/public", file)

I did try to update the binder as follows, but to no avail:

package util

import play.api.mvc.PathBindable

object Binders {

  

  implicit def uuidPathBinder = new PathBindable[java.util.UUID] {

    override def bind(key: String, value: String): Either[String, java.util.UUID] = {

      Right(java.util.UUID.fromString(value))

    }

    override def unbind(key: String, id: java.util.UUID): String = {

      id.toString

    }

  }

  

}

Any thoughts? I thought I read that URI overloading is possible and evaluated in the order defined in the routes file. Is this possible with 2.1.1?

Thanks,

Jon

[Manuel Bernhardt]

Hi Jon,

have you tried binding without the regular expression, just by using a
route of the kind

/api/thing/:id

?

Also I'm afraid your regular expression won't match because it limits
things to decimals, whereas UUIDs mix characters and decimals.

Manuel

[Jon Brule]

Well OK then (obvious revelation here)... A UUID is hexadecimal not decimal... 

When I change the route to the following, the UUID URI works fine:

GET /api/thing/$id<[0-9a-z]{8}-[0-9a-z]{4}-[0-9a-z]{4}-[0-9a-z]{4}-[0-9a-z]{12}> controllers.Things.showById(id: java.util.UUID)

Sometimes a swift boot to the head helps see the light... Or, a Clue x 4 as I like to call it..

Thanks so much to both Manuel and Marius,

Jon

[Pablo Fernandez]

| Well OK then (obvious revelation here)... A UUID is hexadecimal not decimal...

I guess you mean alphanumeric and not numeric :)