在scala中使用akka-http流式傳輸CSV

Question

我對akka-http非常陌生，我想用任意數量的行傳輸csv。

舉例來說，我想回：

a,1 
b,2 
c,3 

用下面的代碼

implicit val actorSystem = ActorSystem("system") 
implicit val actorMaterializer = ActorMaterializer() 

val map = new mutable.HashMap[String, Int]() 
map.put("a", 1) 
map.put("b", 2) 
map.put("c", 3) 
val `text/csv` = ContentType(MediaTypes.`text/csv`, `UTF-8`) 
val route = 
    path("test") { 
    complete { 
     HttpEntity(`text/csv`, ??? using map) 
    } 
    } 
Http().bindAndHandle(route,"localhost",8080) 

感謝您的幫助

編輯：多虧了拉蒙Ĵ羅梅羅ÿ守夜

package test 


import akka.actor.ActorSystem 
import akka.http.scaladsl.Http 
import akka.http.scaladsl.model.HttpCharsets.`UTF-8` 
import akka.http.scaladsl.model._ 
import akka.http.scaladsl.server.Directives._ 
import akka.stream._ 
import akka.util.ByteString 

import scala.collection.mutable 

object Test{ 

    def main(args: Array[String]) { 

    implicit val actorSystem = ActorSystem("system") 
    implicit val actorMaterializer = ActorMaterializer() 

    val map = new mutable.HashMap[String, Int]() 
    map.put("a", 1) 
    map.put("b", 2) 
    map.put("c", 3) 

    val mapStream = Stream.fromIterator(() => map.toIterator) 
     .map((k: String, v: Int) => s"$k,$v") 
     .map(ByteString.apply) 
    val `text/csv` = ContentType(MediaTypes.`text/csv`, `UTF-8`) 
    val route = 
     path("test") { 
     complete { 
      HttpEntity(`text/csv`, mapStream) 
     } 
     } 
    Http().bindAndHandle(route, "localhost", 8080) 

    } 
} 

有了這個代碼，我有兩個編譯錯誤：

Error:(29, 28) value fromIterator is not a member of object scala.collection.immutable.Stream 
val mapStream = Stream.fromIterator(() => map.toIterator) 

Error:(38, 11) overloaded method value apply with alternatives: 
    (contentType: akka.http.scaladsl.model.ContentType,file: java.io.File,chunkSize: Int)akka.http.scaladsl.model.UniversalEntity <and> 
    (contentType: akka.http.scaladsl.model.ContentType,data: akka.stream.scaladsl.Source[akka.util.ByteString,Any])akka.http.scaladsl.model.HttpEntity.Chunked <and> 
    (contentType: akka.http.scaladsl.model.ContentType,data: akka.util.ByteString)akka.http.scaladsl.model.HttpEntity.Strict <and> 
    (contentType: akka.http.scaladsl.model.ContentType,bytes: Array[Byte])akka.http.scaladsl.model.HttpEntity.Strict <and> 
    (contentType: akka.http.scaladsl.model.ContentType.NonBinary,string: String)akka.http.scaladsl.model.HttpEntity.Strict 
cannot be applied to (akka.http.scaladsl.model.ContentType.WithCharset, List[akka.util.ByteString]) 
      HttpEntity(`text/csv`, mapStream) 

我用一個元組列表，以獲得約於第一個問題（豪爾我不知道該怎麼流在斯卡拉地圖） 不知道的第二個 感謝您的幫助。

（我使用Scala的2.11.8）

Answer 1

使用apply功能HttpEntity這需要在Source[ByteString,Any]。申請創建一個Chunked實體。您可以使用基於documentation代碼使用阿卡流Source流文件IO讀取文件：

import akka.stream.scaladsl._ 

val file = Paths.get("yourFile.csv") 

val entity = HttpEntity(`txt/csv`, FileIO.fromPath(file)) 

流將文件分解成塊大小，default is currently set to 8192。

要流，你已經創造了你可以使用類似伎倆地圖：

val mapStream = Source.fromIterator(() => map.toIterator) 
         .map((k : String, v : Int) => s"$k,$v") 
         .map(ByteString.apply) 

val mapEntity = HttpEntity(`test/csv`, mapStream)