Scala Lagom中的多部分表单数据

我想有一个服务，它接收一个item对象，该对象包含；名称、描述、价格和图片

其他属性是字符串，可以很容易地作为Json对象发送，但是对于包含图片，最好的解决方案是什么

如果多部分formdata是最佳解决方案，那么在Lagom中如何处理它

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您可能希望在GitHub上的lagom recipes存储库中检查

基本上，这个想法是创建一个额外的播放路由器。之后，我们必须告诉Lagom按照中的说明使用它（此功能从1.5.0开始提供）。以下是路由器的外观：

class FileUploadRouter(action: DefaultActionBuilder,
                       parser: PlayBodyParsers,
                       implicit val exCtx: ExecutionContext) {
  private def fileHandler: FilePartHandler[File] = {
    case FileInfo(partName, filename, contentType, _) =>
      val tempFile = {
        val f = new java.io.File("./target/file-upload-data/uploads", UUID.randomUUID().toString).getAbsoluteFile
        f.getParentFile.mkdirs()
        f
      }
      val sink: Sink[ByteString, Future[IOResult]] = FileIO.toPath(tempFile.toPath)
      val acc: Accumulator[ByteString, IOResult] = Accumulator(sink)
      acc.map {
        case akka.stream.IOResult(_, _) =>
          FilePart(partName, filename, contentType, tempFile)
      }

  }
  val router = Router.from {
    case POST(p"/api/files") =>
      action(parser.multipartFormData(fileHandler)) { request =>
        val files = request.body.files.map(_.ref.getAbsolutePath)
        Results.Ok(files.mkString("Uploaded[", ", ", "]"))
      }
  }
}

然后，我们简单地告诉Lagom使用它

  override lazy val lagomServer =
    serverFor[FileUploadService](wire[FileUploadServiceImpl])
      .additionalRouter(wire[FileUploadRouter].router)

或者，我们可以使用

PlayServiceCall

类。以下是Lightbend团队的James Roper提供的关于如何实现这一点的简单草图：

// The type of the service call is NotUsed because we are handling it out of band
def myServiceCall: ServiceCall[NotUsed, Result] = PlayServiceCall { wrapCall =>
  // Create a Play action to handle the request
  EssentialAction { requestHeader =>

    // Now we create the sink for where we want to stream the request to - eg it could
    // go to a file, a database, some other service. The way Play gives you a request
    // body is that you need to return a sink from EssentialAction, and when it gets
    // that sink, it stream the request body into that sink.
    val sink: Sink[ByteString, Future[Done]] = ...

    // Play wraps sinks in an abstraction called accumulator, which makes it easy to
    // work with the result of handling the sink. An accumulator is like a future, but
    // but rather than just being a value that will be available in future, it is a
    // value that will be available once you have passed a stream of data into it.
    // We wrap the sink in an accumulator here.
    val accumulator: Accumulator[ByteString, Done] = Accumulator.forSink(sink)

    // Now we have an accumulator, but we need the accumulator to, when it's done,
    // produce an HTTP response.  Right now, it's just producing akka.Done (or whatever
    // your sink materialized to).  So we flatMap it, to handle the result.
    accumulator.flatMap { done =>

      // At this point we create the ServiceCall, the reason we do that here is it means
      // we can access the result of the accumulator (in this example, it's just Done so
      // not very interesting, but it could be something else).
      val wrappedAction = wrapCall(ServiceCall { notUsed =>

        // Here is where we can do any of the actual business logic, and generate the
        // result that can be returned to Lagom to be serialized like normal

        ...
      })

      // Now we invoke the wrapped action, and run it with no body (since we've already
      // handled the request body with our sink/accumulator.
      wrappedAction(request).run()
    }
  }
}

一般来说，使用Lagom来达到这个目的可能不是一个好主意。正如GitHub发行的

PlayServiceCall

文档中所述：

我们回退到PlayServiceCall的许多用例都与表示或HTTP特定使用（I18N，文件上载，…）有关，这表明：lagom服务与表示层的耦合或lagom服务与传输的耦合

再次引用詹姆斯·罗珀（几年前）的话：

因此，目前Lagom中不支持多部分/表单数据，至少不支持开箱即用。您可以下拉到较低级别的Play API来处理它，但可能最好在web网关中处理它，在web网关中处理的任何文件都直接上载到存储服务（如S3），然后Lagom服务可能会存储与之相关的元数据

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您还可以查看此处，它提供了更多的见解。

虽然此链接可以回答问题，但最好在此处包含答案的基本部分，并提供链接以供参考。如果链接页面发生更改，仅链接的答案可能无效。-@KrzysztofAtłasik，对不起，我不知道。试着用更多的解释来给他指出正确的方向。请用你提供的资料加上一个例子，你肯定会得到公认的答案+从meDone，我只是希望帮助更多和我有同样问题的人，不管是否被接受都无关紧要。干杯。当然，我只是想解释一下为什么有些人投了反对票。不管怎样，干得好！