Play 2 (Scala) i18n Patterns

かる@krrrr38
- 2015新卒（Java, Perl）で上京
- Slickドキュメント日本語訳

Agenda

i18n Basic Pattern

Play 2.3
Play 2.4

i18n Path Variable Pattern

Simple Pattern
- /en/page
- /ja/page
Optional Lang Path Variable Pattern
- /page
- /ja/page

i18n sbt 💪 Pattern

code generating

i18n Basic Pattern

Play 2.3
Play 2.4

i18n basic in Play 2.3

controller 側 : Lang を生成して view に渡す

def index = Action { implicit request =>
  ... // request2lang (trait Controller)
}

view

@()(implicit lang: Lang)

<h1>@Messages("my.message")</h1>

Messages.apply が implicit lang: Lang を取る

Play 2.3 つらいの話

Playframework の Lang でつらいところ
- Langを渡さなくてもコンパイルが通る
- (object Lang に implicit lazy val defaultLang: Lang が存在するため)
  - e.g. controller側で Lang を渡し忘れる (implicit req 忘れ)
    - 🙅渡し忘れた箇所全てがデフォルト言語で展開される
  - e.g. view側で Lang を渡し忘れる ↓
    - 🙅渡し忘れた箇所のみデフォルト言語で展開される

index.scala.html

@()(implicit lang: Lang)

<h1>@Messages("hello")</h1>
@partial()

partial.scala.html

@()

<h2>@Messages("world")</h2>

結果

<h1>こんにちは</h1>
<h2>World</h2>

対策案 in Play 2.3

controller (trait MyLangSupport or object MyImplicits)

case class MyLang(val lang: Lang)
implicit def request2lang(implicit req: RequestHeader): MyLang = ...

view 用ヘルパーオブジェクト

package my.views
object ViewHelpers {
  // （ここでrequestなどを使って優先する言語を変更したり等も簡単に出来る）
  def i18n(key: String, args: Any*)(implicit myLang: MyLang): String =
    messages(key, args: _*)(myLang.lang)
}

build.sbt

play.twirl.sbt.TwirlKeys.templateImports ++= Seq(
  "my.views.ViewHelpers"
)

view

@()(implicit lang: MyLang)

@ViewHelpers.i18n("my.message")

🙆 MyLang 渡し忘れは コンパイルエラー
🙅 Messages を必要とする箇所には別途対応が必要
- views.html.helper...
- play.api.data.validation.Constraints...

i18n basic in Play 2.4

controller 側 : Messages (not Lang) を生成してviewに渡す

class Application @Inject() (val messagesApi: MessagesApi) extends Controller with I18nSupport {
  def index = Action { implicit request =>
    ... // request2Messages (I18nSupport)
  }
}

view

@()(implicit messages: Messages)

<h1>@Messages("my.message")</h1>

I18nSupport

implicit def request2Messages(implicit request: RequestHeader): Messages =
  messagesApi.preferred(request)

controller に implicit request 忘れ
- 🙆 コンパイルエラー
view に implicit messages 忘れ
- 🙆 コンパイルエラー

[TIP] preferred(request) in `DefaultMessagesApi`

リクエスト側の候補順を基に、サーバ側にマッチするものを探す

サーバ側の候補

application.conf に書かれたもの全て

リクエスト側の候補

langCookieName に含まれる言語
Accept-Language ヘッダ (前に書かれたものが優先)

マッチしない場合…

application.conf に書かれた最初のもの
Lang.defaultLang
- java.util.Locale.getDefault

MessagesApi

def setLang(result: Result, lang: Lang): Result

DefaultMessagesApi

def setLang(result: Result, lang: Lang) =
  result.withCookies(Cookie(langCookieName, lang.code, path = Session.path, domain = Session.domain, secure = langCookieSecure, httpOnly = langCookieHttpOnly))

i18n in Play 2.4 with DI

独自の MessageApi をInjectさせると、先ほどの ViewHelper の代替も可能
- DefaultMessageApi を継承して、override させるのが簡単
- 🙆 リクエスト以外の設定値から Lang を決定する事も可能

package my.components

@Singleton
class MyMessagesApi @Inject() (
  environment: Environment,
  configuration: Configuration,
  langs: Langs
  ) extends DefaultMessagesApi(environment, configuration, langs)
       with MyRequestToUserSupport {

  override def preferred(request: RequestHeader) =
    getUser(request).fold(super.preferred(request))(user => new Messages(user.lang, this))

)

（注: I18nSupport を独自のものに変えた方が楽な事もある）

2 DI patterns in Play 2.4

1. DIの差し替え (recommended)

MyI18nModule

package modules
class MyI18nModule extends Module {
  def bindings(environment: Environment, configuration: Configuration) = {
    Seq(
      bind[Langs].to[DefaultLangs],
      bind[MessagesApi].to[MyMessagesApi] // instead of DefaultMyMessagesApi
    )
  }
}

application.conf

play.modules.enabled += "modules.MyI18nModule"
play.modules.disabled += "play.api.i18n.I18nModule"

🙆 DefaultMessagesApiが誤って呼ばれる事は無い, コントローラ側の変更が無い
🙅 誤った名前のモジュール名を指定しても、コンパイルエラーにはならない

2. controller で直接指定 (not recommended)

class Application @Inject() (val messagesApi: MyMessagesApi) extends Controller with I18nSupport ...

🙅 MesagesApiと書いたらDefaultMessagesApiが呼ばれる
- 絶対間違えるので、やめた方が良い

[TIP] MessageApi Tips in Play 2.4

e.g. jodatime を利用する際に、MessageFormat の date を利用する

messages.en (java.text.MessageFormat)

my.time=Time is {0,date}

MessagesApi

package my.components

@Singleton
class MyMessagesApi ... {
  override def preferred(request: RequestHeader) = ...

  override def apply(key: String, args: Any*)(implicit lang: Lang): String = {
    super.apply(key, args.map {
      case localdate: org.joda.time.LocalDate => localdate.toDate
      case arg => arg
    }: _*)(lang)
  }
)

i18n Path Variable Pattern

/en/page
/ja/page

Simple path variable way

routes : Lang を利用

GET  /$lang<[a-zA-Z]{2,3}>/page  controllers.NoI18nSupportController.page(lang: Lang)

Lang 用の PathBindable
- （e.g. Langs を Inject して langs.availables のみ通す）

package components
object MyImplicits {
  implicit def langPathBindable = new PathBindable[Lang] {
    override def bind(key: String, value: String) = Lang.get(value) match {
      case Some(lang) => Right(lang)
      case None       => Left("Invalid lang path value.")
    }

    override def unbind(key: String, value: Lang) = value.language
  }
}

build.sbt

routesImport ++= Seq("components.MyImplicits._", "play.api.i18n.Lang")

i18n Optional Path Variable Pattern

/page ⇔ /ja/page

routes : 😇 ２行書く 😇

GET  /page                controllers.NoI18nSupportController.page(lang: Option[Lang] = None)
GET  /$lang<[a-zA-Z]{2,3}>/page  controllers.NoI18nSupportController.page(lang: Option[Lang])

PathBindable for Option

package components
object MyImplicits {
  implicit def langPathBindable = new PathBindable[Lang] {...}

  // =====>> New!! <<=====
  implicit def optionPathBindable[A: PathBindable] = new PathBindable[Option[A]] {
    def bind(key: String, value: String): Either[String, Option[A]] =
      implicitly[PathBindable[A]].bind(key, value).fold(
        left  => Left(left),
        right => Right(Some(right))
      )

    def unbind(key: String, value: Option[A]): String =
      value.map(_.toString).getOrElse("")
  }
  ...
}

Another solution with Play 2.4 custom router

/contents/ja/... ⇔ /contents/en/...

routes (Splitting the route file in Play 2.3.x)

# GET  /contents/:lang/       controllers...
->   /contents   routers.MyContentsRouter

routers.MyContentsRouter

package routers

class MyContentsRouter @Inject()(controller: ContentsController) extends SimpleRouter {
  override def routes = Function.unlift {
    case p"/$lang<[a-zA-Z]{2,3}>" =>
      Lang.get(lang).map(controller.index)
    case _ => None
  }
}

Another solution with Play 2.4 custom router

ReverseRouter???
- example definition
- example usage

🙌 こころをこめて 🙌

package routers

// call like `@routers.ContentsReverseRouter.index` in views and so on
object ContentsReverseRouter {
  private def instance: ReverseRouter = play.api.Play.current.injector.instanceOf[ReverseRouter]
  def index(maybeLang: Option[Lang]) = instance.index(maybeLang)
}

@Singleton
class ReverseRouter @Inject() (routerProvider: Provider[Router]) {
  private def router: Router = routerProvider.get
  def index(maybeLang: Option[Lang]) = {
    maybeLang.fold("/contents/")(lang => s"/contents/${lang.code}")
  }
}

🙇 redundant definitions 🙇

GET  /                             controllers.MyController.index(lang: Option[Lang] = None)
GET  /$lang<[a-zA-Z]{2,3}>/        controllers.MyController.index(lang: Option[Lang])
GET  /profile                      controllers.MyController.profile(lang: Option[Lang] = None)
GET  /$lang<[a-zA-Z]{2,3}>/profile controllers.MyController.profile(lang: Option[Lang])
GET  /access                       controllers.MyController.access(lang: Option[Lang] = None)
GET  /$lang<[a-zA-Z]{2,3}>/access  controllers.MyController.access(lang: Option[Lang])

package routers

class MyContentsRouter ... {
  override def routes = Function.unlift {
    case p"/$lang<[a-zA-Z]{2,3}>"         => controller.index
    case p"/$lang<[a-zA-Z]{2,3}>/profile" => controller.profile
    case p"/$lang<[a-zA-Z]{2,3}>/access"  => controller.access
    case _ => None
  }
}
object ContentsReverseRouter {
  def index(maybeLang: Option[Lang])   = instance.index(maybeLang)
  def profile(maybeLang: Option[Lang]) = instance.profile(maybeLang)
  def access(maybeLang: Option[Lang])  = instance.access(maybeLang)
}
class ReverseRouter ... {
  def index(maybeLang: Option[Lang])   = ...
  def profile(maybeLang: Option[Lang]) = ...
  def access(maybeLang: Option[Lang])  = ...
}

i18n sbt 💪 Pattern

🙏 Let’s generate Router/routes by sbt 🙏

sbt を用いて、routes 関連のコードの重複を無くす

方針: sbt でコード生成

言語別に出し分けする設定ファイル（routes）を用意 (or something else)
コンパイル前に言語別に出し分けする用の Router or routes を作成

Play 2.4 で routes をパースする方法
- play.routes.compiler.RoutesFileParser.parse
- routes の場所: baseDirectory / "conf" / "routes" (or another solution?)
Play 2.3 で routes をパースする方法
- private[router] play.router.RouteFileParser.parse
- play.router パッケージに置いて誤魔化す or 自作パーサー
- routes の場所: confDirectory / "routes"

e.g. i18n 用 Router の自動生成 in Play 2.4

/contents/, /contents/ja/, /contents/profile, /contents/ja/profile, /contents/access, /contents/ja/access, …

routes

->   /contents   routers.MyGeneratedRouter

routes.i18n (it’s ok to write with any format)

GET  /         controllers.ContentsController.index(lang: Option[play.api.i18n.Lang])
GET  /profile  controllers.ContentsController.profile(lang: Option[play.api.i18n.Lang])
GET  /access   controllers.ContentsController.access(lang: Option[play.api.i18n.Lang])

build.sbt

sourceGenerators in Compile <+= (baseDirectory, sourceManaged) map { case (base, source) =>
  val countries = Seq("en", "ja") // it should be taken from play.i18n.langs in application.conf
  val langRoutesFile = base / "conf" / "routes.i18n"
  MyI18NContentsRouterGenerator.generate(langRoutesFile, countries, source).toSeq
}

e.g. i18n 用 Router の自動生成 in Play 2.4 続き

conf/MyRouterGenerator.scala

import play.routes.compiler.{RoutesFileParser, Route, Rule}
import sbt.File
import sbt.Path._

object MyI18NContentsRouterGenerator {
  val LANG_ROUTER_CLASS = "MyGeneratedRouter"
  val LANG_ROUTER_FILE = LANG_ROUTER_CLASS + ".scala"
  def generate(langRoutes: File, countries: Seq[String], sourceManaged: File): Option[File] = {
    RoutesFileParser.parse(langRoutes) match {
      case Right(rules: List[Rule]) =>
        val outputFile = sourceManaged / LANG_ROUTER_FILE
        sbt.IO.write(outputFile, _generate(rules))
        Some(outputFile)
      case Left(_) => None
    }
  }

  private def _generate(rules: List[Rule]): String = {
    val routesValues = StringBuilder.newBuilder
    val reverseRouterObjValues = StringBuilder.newBuilder
    val reverseRouterValues = StringBuilder.newBuilder
    rules.foreach {
      case route: Route =>
        routesValues.append(generateRoutesValue(route))
        reverseRouterObjValues.append(generateReverseRouterObjValue(route))
        reverseRouterValues.append(generateReverseRouterValue(route))
      case _ => // ignore
    }

    s"""
      |package routers
      |
      |import javax.inject.{Singleton, Provider, Inject}
      |
      |import controllers.ContentsController
      |import play.api.i18n.Lang
      |import play.api.routing.{Router, SimpleRouter}
      |import play.api.routing.sird._
      |
      |class ${LANG_ROUTER_CLASS} @Inject()(controller: ContentsController) extends SimpleRouter {
      |  val DEFAULT_LANG = Lang("en")
      |  override def routes = Function.unlift {
      |    ${routesValues}
      |    case _ => None
      |  }
      |}
      |
      |object LangReverseRouter {
      |  private def instance: ReverseRouter = play.api.Play.current.injector.instanceOf[ReverseRouter]
      |  ${reverseRouterObjValues}
      |}
      |
      |@Singleton
      |class ReverseRouter @Inject() (routerProvider: Provider[Router]) {
      |  private def router: Router = routerProvider.get
      |  ${reverseRouterValues}
      |}
    """.stripMargin
  }

  private def generateRoutesValue(route: Route): String = {
    s"""
      |    case p"/${route.call.method}" =>
      |      Some(controller.${route.call.method}(DEFAULT_LANG))
      |    case p"/$$lang<[a-zA-Z]{2,3}>/${route.call.method}" =>
      |      Lang.get(lang).map(controller.${route.call.method})
    """.stripMargin
  }

  private def generateReverseRouterObjValue(route: Route): String =
    s"""
       |  def ${route.call.method}(maybeLang: Option[Lang]) = instance.${route.call.method}(maybeLang)
    """.stripMargin

  private def generateReverseRouterValue(route: Route): String =
    s"""
       |  def ${route.call.method}(maybeLang: Option[Lang]) =
       |    maybeLang.fold("/${route.call.method}")(lang => "/" + lang.code + "/${route.call.method}")
     """.stripMargin
}

i18n sbt 💪 Pattern

It’s possible to see generated src easily.

routes.i18n をチェックして変更のあった時のみファイルを生成する
- sbtでプロジェクトファイルが変更されたらメッセージを表示する - scalaとか・・・

Play 2 (Scala) i18n Patterns

i18n Basic Pattern

Play 2.3
Play 2.4

i18n Path Variable Pattern

Simple Pattern
- /en/page
- /ja/page
Optional Lang Path Variable Pattern
- /page
- /ja/page

i18n sbt 💪 Pattern

code generating

Play 2 (Scala) i18n Patterns

Agenda

i18n Basic Pattern

i18n Path Variable Pattern

i18n sbt 💪 Pattern

i18n Basic Pattern

i18n basic in Play 2.3

Play 2.3 つらいの話

対策案 in Play 2.3

i18n basic in Play 2.4

I18nSupport

[TIP] preferred(request) in DefaultMessagesApi

サーバ側の候補

リクエスト側の候補

マッチしない場合…

[TIP] Cookie に Lang を保存 in Play 2.4

i18n in Play 2.4 with DI

2 DI patterns in Play 2.4

1. DIの差し替え (recommended)

2. controller で直接指定 (not recommended)

[TIP] MessageApi Tips in Play 2.4

i18n Path Variable Pattern

Simple path variable way

i18n Optional Path Variable Pattern

Another solution with Play 2.4 custom router

Another solution with Play 2.4 custom router

i18n sbt 💪 Pattern

方針: sbt でコード生成

e.g. i18n 用 Router の自動生成 in Play 2.4

e.g. i18n 用 Router の自動生成 in Play 2.4 続き

i18n sbt 💪 Pattern

Play 2 (Scala) i18n Patterns

i18n Basic Pattern

i18n Path Variable Pattern

i18n sbt 💪 Pattern

[TIP] preferred(request) in `DefaultMessagesApi`