我正在按照以下文档尝试客户端 WebsocketwebSocket客户端流.
示例代码是:
import akka.actor.ActorSystem
import akka.Done
import akka.http.scaladsl.Http
import akka.stream.ActorMaterializer
import akka.stream.scaladsl._
import akka.http.scaladsl.model._
import akka.http.scaladsl.model.ws._
import scala.concurrent.Future
object WebSocketClientFlow {
def main(args: Array[String]) = {
implicit val system = ActorSystem()
implicit val materializer = ActorMaterializer()
import system.dispatcher
// Future[Done] is the materialized value of Sink.foreach,
// emitted when the stream completes
val incoming: Sink[Message, Future[Done]] =
Sink.foreach[Message] {
case message: TextMessage.Strict =>
println(message.text)
}
// send this as a message over the WebSocket
val outgoing = Source.single(TextMessage("hello world!"))
// flow to use (note: not re-usable!)
val webSocketFlow = Http().webSocketClientFlow(WebSocketRequest("ws://echo.websocket.org"))
// the materialized value is a tuple with
// upgradeResponse is a Future[WebSocketUpgradeResponse] that
// completes or fails when the connection succeeds or fails
// and closed is a Future[Done] with the stream completion from the incoming sink
val (upgradeResponse, closed) =
outgoing
.viaMat(webSocketFlow)(Keep.right) // keep the materialized Future[WebSocketUpgradeResponse]
.toMat(incoming)(Keep.both) // also keep the Future[Done]
.run()
// just like a regular http request we can access response status which is available via upgrade.response.status
// status code 101 (Switching Protocols) indicates that server support WebSockets
val connected = upgradeResponse.flatMap { upgrade =>
if (upgrade.response.status == StatusCodes.SwitchingProtocols) {
Future.successful(Done)
} else {
throw new RuntimeException(s"Connection failed: ${upgrade.response.status}")
}
}
// in a real application you would not side effect here
connected.onComplete(println)
closed.foreach(_ => println("closed"))
}
}
连接升级后,如何使用connection
向 websocket 服务器端发送消息?
我从文档中注意到:
此方法返回的 Flow 只能实现一次。对于每个请求,必须通过再次调用该方法来获取新的流。
仍然很困惑,既然升级后的连接已经准备好了,为什么我们需要多次构建流程。
您可以创建基于参与者的源并通过已建立的 Websocket 连接发送新消息。
val req = WebSocketRequest(uri = "ws://127.0.0.1/ws")
val webSocketFlow = Http().webSocketClientFlow(req)
val messageSource: Source[Message, ActorRef] =
Source.actorRef[TextMessage.Strict](bufferSize = 10, OverflowStrategy.fail)
val messageSink: Sink[Message, NotUsed] =
Flow[Message]
.map(message => println(s"Received text message: [$message]"))
.to(Sink.ignore)
val ((ws, upgradeResponse), closed) =
messageSource
.viaMat(webSocketFlow)(Keep.both)
.toMat(messageSink)(Keep.both)
.run()
val connected = upgradeResponse.flatMap { upgrade =>
if (upgrade.response.status == StatusCodes.SwitchingProtocols) {
Future.successful(Done)
} else {
throw new RuntimeException(s"Connection failed: ${upgrade.response.status}")
}
}
ws ! TextMessage.Strict("Hello World")
ws ! TextMessage.Strict("Hi")
ws ! TextMessage.Strict("Yay!")
`
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