我想要一个接收项目对象的服务,该对象包含;名称、描述、价格和图片。
- 其他属性是可以很容易地作为 Json 对象发送的字符串,但是对于包含图片的最佳解决方案是什么?
- 如果 multipart formdata 是最好的解决方案,它是如何在 Lagom 中处理的?
我想要一个接收项目对象的服务,该对象包含;名称、描述、价格和图片。
您可能需要查看GitHub 上 lagom-recipes 存储库中的文件上传示例。
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 按照参考文档中的说明使用它(此功能从 1.5.0 开始可用)。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
该类。这是 Lightbend 团队的 James Roper 提供的关于如何做到这一点的简单草图:
// 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,为此目的使用 Lagom 可能不是一个好主意。正如关于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、文件上传等)有关,这表明:lagom 服务与表示层的耦合或 lagom 服务与传输层的耦合。
再次引用 James Roper(几年前):
所以目前,Lagom 不支持 multipart/form-data,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,但也许最好在 Web 网关中处理它,其中处理的任何文件都直接上传到 S3 等存储服务,然后 Lagom 服务可能会存储与之关联的元数据。
您还可以在此处查看讨论,它提供了更多见解。