playのErrorHandleでreqest.bodyを参照する。

import akka.actor.ActorSystem
import akka.stream.ActorMaterializer
import javax.inject._
import play.api._
import play.api.http.DefaultHttpErrorHandler
import play.api.mvc.Results._
import play.api.mvc._
import play.api.routing.Router
import play.core.server.akkahttp.AkkaHeadersWrapper

import scala.concurrent._
import scala.util.Success

class ErrorHandler @Inject()(
                              env: Environment,
                              config: Configuration,
                              sourceMapper: OptionalSourceMapper,
                              router: Provider[Router]
                            ) extends DefaultHttpErrorHandler(env, config, sourceMapper, router)
  with play.api.Logging {

  implicit val system = ActorSystem()

  implicit val materializer = ActorMaterializer()

  override protected def onDevServerError(request: RequestHeader, exception: UsefulException): Future[Result] = {
    val postData = request.headers.asInstanceOf[AkkaHeadersWrapper].request.entity.dataBytes.runFold(akka.util.ByteString.empty)(_ ++ _).map(_.utf8String)(system.dispatcher)
    postData.onComplete {
      case Success(post) => logger.error(s"POST DATA:" + post)
    }(system.dispatcher)

    Future.successful {
      Forbidden("You're not allowed to access this resource.")
    }
  }
}