Playframework 和 Twitter 流媒体 API

Question

如何从 Twitter Streaming API - POST statuses/filter 读取响应数据？我已建立连接并收到 200 状态码，但我不知道如何阅读推文。我只想在推文到来时打印出来。

ws.url(url)
.sign(OAuthCalculator(consumerKey, requestToken))
.withMethod("POST")
.stream()
.map { response =>
  if(response.headers.status == 200)
    println(response.body)
}

编辑：我找到了这个解决方案

ws.url(url)
.sign(OAuthCalculator(consumerKey, requestToken))
.withMethod("POST")
.stream()
.map { response => 
  if(response.headers.status == 200){
    response.body
      .scan("")((acc, curr) => if (acc.contains("\r\n")) curr.utf8String else acc + curr.utf8String)
      .filter(_.contains("\r\n"))
      .map(json => Try(parse(json).extract[Tweet]))
      .runForeach {
        case Success(tweet) =>
          println("-----")
          println(tweet.text)
        case Failure(e) =>
          println("-----")
          println(e.getStackTrace)
      }
  }
}

Answer 1

调用 stream() 会给你一个 Future[StreamedResponse]。然后你必须使用 akka 习语来转换其中的 ByteString 块。类似于：

val stream = ws.url(url)
  .sign(OAuthCalculator(consumerKey, requestToken))
  .withMethod("POST")
  .stream()

stream flatMap { res =>
  res.body.runWith(Sink.foreach[ByteString] { bytes =>
    println(bytes.utf8String)
  })
}

请注意，我没有测试上面的代码（但它基于 https://www.playframework.com/documentation/2.5.x/ScalaWS plus the sink description from http://doc.akka.io/docs/akka/2.4.2/scala/stream/stream-flows-and-basics.html 的流响应部分）

另请注意，这将在其自己的行上打印每个块，我不确定 twitter API 是否会返回每个块的完整 json blob。如果你想在打印之前积累块，你可能需要使用 Sink.fold。

Answer 2

流式 WS 请求的响应主体是 Akka Streams Source of bytes. Since Twitter Api responses are newline delimited (usually) you can use Framing.delimiter，将它们分成字节块，将块解析为 JSON，然后用它们做你想做的事。这样的事情应该有效：

import akka.stream.scaladsl.Framing
import scala.util.{Success, Try}
import akka.util.ByteString
import play.api.libs.json.{JsSuccess, Json, Reads}
import play.api.libs.oauth.{ConsumerKey, OAuthCalculator, RequestToken}

case class Tweet(id: Long, text: String)
object Tweet {
  implicit val reads: Reads[Tweet] = Json.reads[Tweet]
}

def twitter = Action.async { implicit request =>
  ws.url("https://stream.twitter.com/1.1/statuses/filter.json?track=Rio2016")
      .sign(OAuthCalculator(consumerKey, requestToken))
      .withMethod("POST")
      .stream().flatMap { response =>
    response.body
      // Split up the byte stream into delimited chunks. Note
      // that the chunks are quite big
      .via(Framing.delimiter(ByteString.fromString("\n"), 20000))
      // Parse the chunks into JSON, and then to a Tweet.
      // A better parsing strategy would be to account for all
      // the different possible responses, but here we just
      // collect those that match a Tweet.
      .map(bytes => Try(Json.parse(bytes.toArray).validate[Tweet]))
      .collect {
        case Success(JsSuccess(tweet, _)) => tweet.text
      }
      // Print out each chunk
      .runForeach(println).map { _ =>
        Ok("done")
    }
  }
}

注意：要具体化流，您需要将隐式 Materializer 注入控制器。

Playframework 和 Twitter 流媒体 API

Playframework and Twitter Streaming API

twitter

scala

playframework

twitter-streaming-api

playframework-2.5