Play frameworkのカスタムエラーページにmessagesファイルに定義されている文字列を読み込んで表示するためのコードを組み込んだエラーハンドラ。

SampleWebErrorHandler.scala

// Sample Implementation to display a message from the message file.
// See https://pandanote.info/?p=5370 for details.
import org.slf4j.LoggerFactory
import javax.inject.Inject
import play.api.http.HttpErrorHandler
import play.api.mvc.Results._
import play.api.mvc.RequestHeader
import play.api.i18n.{ Langs, Lang, MessagesApi, MessagesImpl }

import scala.concurrent.Future

class SampleWebErrorHandler @Inject()(langs: Langs, messagesApi: MessagesApi) extends HttpErrorHandler {

  private lazy val logger = LoggerFactory.getLogger(classOf[SampleWebErrorHandler])

  val lang = langs.availables.head

  override def onClientError(request: RequestHeader, statusCode: Int, message: String) = {
    logger.warn("ClientError: statusCode="+statusCode,message)
    Future.successful(
      Status(statusCode)(views.html.error.render(Option(statusCode), new MessagesImpl(lang, messagesApi)))
    )
  }

  override def onServerError(request: RequestHeader, exception: Throwable) = {
    logger.error("ServerError:"+exception.toString,exception)
    Future.successful(
      InternalServerError(views.html.error.render(None, new MessagesImpl(lang, messagesApi)))
    )
  }

}