Play Framework：如何在不阻塞的情况下修改响应体？

Question

我正在使用这本书 Reactive Web Applications: Covers Play, Akka, and Reactive Streams 在 Play 上磨牙。第 4 章，除其他外，教授如何编写过滤器，但书中显示的代码无法编译，因为在 Play 2.4.x 中，Result.body 曾经是 Enumerator[Array[Byte]]，而在 2.5.x 中是 @ 987654327@.

我的过滤器版本如下：

class ScoreFilter @Inject()(implicit val mat: Materializer, ec: ExecutionContext) extends Filter {
  override def apply(nextFilter: (RequestHeader) => Future[Result])(rh: RequestHeader) =
    nextFilter(rh).map { result =>
      if (result.header.status == OK || result.header.status == NOT_ACCEPTABLE) {
        val correct = result.session(rh).get("correct").getOrElse(0)
        val wrong = result.session(rh).get("wrong").getOrElse(0)

        val score = s"\nYour current score is: $correct correct " +
          s"answers and $wrong wrong answers"

        val contentType = result.body.contentType
        val scoreByteString = ByteString(score.getBytes(UTF_8))
        val maybeNewBody = result.body.consumeData.map(_.concat(scoreByteString))

        import scala.concurrent.duration._
        val newBody = Await.result(maybeNewBody, 10 seconds)

        result.copy(body = Strict(newBody, contentType))
      } else {
        result
      }
    }
}

在书中：

// result.body returns a play.api.http.HttpEntity which doesn't have an andThen method
val newBody = result.body andThen Enumerator(score.getBytes(UTF_8))
result.copy(body = newBody)

如您所见，我的过滤器版本有效，但它会阻止未来。我想知道是否有更好的方法可以在不阻塞的情况下做到这一点？

P.S.：在将我的问题视为重复问题之前，请注意我已经阅读了以下所有主题，它们将响应正文转换为字符串，这不是我想要的。

Scala play http filters: how to find the request body

Play framework filter that modifies json request and response

Play 2.4: intercept and modify response body

Answer 1

如果你想避开Await.result，你可以这样做：

nextFilter(rh).flatMap { result =>
  ...
  maybeNewBody map { newBody =>
    result.copy(body = Strict(newBody, contentType))
  }
} else Future.successful(result)

（注意map更改为flatMap）