Question

我想要一个接收一个item对象的服务，该对象包含;名称，描述，价格和图片。

其他属性是可以作为Json对象轻松发送的字符串，但包含图片的最佳解决方案是什么？
如果multipart formdata是如何在Lagom中处理它的最佳解决方案？

Answer 1

您可能要检查GitHub上lagom-recipes存储库中的file upload example。

基本上，这个想法是创建一个额外的Play路由器。之后，我们必须告诉Lagom按照reference documentation中的说明使用它（此功能自1.5.0起可用）。这是路由器的外观：

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，我们只是告诉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。这是Lightbend团队的James Roper提供的有关如何执行此操作的简单草图：

// 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()
    }
  }
}

通常来说，为此目的使用Lagom可能不是一个好主意。如PlayServiceCall文档的GitHub问题所述：

我们回退到PlayServiceCall的许多用例与表示或特定于HTTP的使用（I18N，文件上载...）有关，它们指示：将lagom服务耦合到表示层，或将lagom服务耦合到显示层。运输。

（几年前）再次引用James Roper：

因此，目前，Lagom不支持multipart / form-data，至少不是开箱即用的。您可以下拉至较低级别的Play API来处理它，但是在Web网关中处理它可能会更好，在Web网关中，处理的所有文件都直接上传到存储服务（例如S3），然后Lagom服务可以存储与之关联的元数据。

您还可以在此处查看discussion，以提供更多的见解。

Lagom中的多部分表格数据

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