finagle 服务中未实现的特征

Question

我有一个简单的 finagle 服务如下：

import com.twitter.finagle.{Http,Service}
import com.twitter.util.{Await, Future}
import java.net.InetSocketAddress
import org.jboss.netty.handler.codec.http._
import org.jboss.netty.buffer.ChannelBuffers.copiedBuffer
import org.jboss.netty.util.CharsetUtil
import net.liftweb.json._
import com.twitter.finagle.http.{Request,Response,RichHttp}
import com.twitter.finagle.builder.ServerBuilder

case class Add(num1:Int, num2:Int)
case class Result(result:Int)  

trait Transformer[R1,T,U,R2] {
  def extractPayload(r:R1):T
  def responsePayload(u:U):R2
}

object Transformer{
  implicit object AddPayloadTransformer 
        extends Transformer[HttpRequest,Add,Result,HttpResponse]{
   implicit val formats = DefaultFormats

   def extractPayload(r:HttpRequest):Add = {
        val body = r.getContent
    val length = body.readableBytes()
    val bytes = new Array[Byte](length)
    body.getBytes(body.readerIndex(),bytes,0,length)
    val bodyStr = new String(bytes)
    parse(bodyStr).extract[Add]
    }

   def responsePayload(u:Result):HttpResponse = {   
    val result = u.result
    val response = Response(HttpVersion.HTTP_1_1,
                HttpResponseStatus.OK)
        response.setContentTypeJson()       
        response.setContentString(
          s"""
            {
            "result": $result
            }
           """)
        response.httpResponse
   }   
  }
}

object AdditionServer extends App with Transformer[HttpRequest,Add,Result,HttpResponse]{
 private def add(add:Add):Result = Result(add.num1 + add.num2) 

 private def additionHandler(req:HttpRequest): HttpResponse = {
     val addPayload = extractPayload(req)
     val result = add(addPayload)
     responsePayload(result)    
 }   

 val service = new Service[HttpRequest,HttpResponse] {
     def apply(req: HttpRequest): Future[HttpResponse] = 
    {
       Future.value(additionHandler(req))
    }
 }

  val server = Http.serve(":8080", service)
  Await.ready(server)
  println("Started service")                
}

当我尝试编译它时，出现以下异常：

AdditionService.scala:49: object creation impossible, since:
[error] it has 2 unimplemented members.
[error] /** As seen from object AdditionServer, the missing signatures are as follows.
[error]  *  For convenience, these are usable as stub implementations.
[error]  */
[error]   def extractPayload(r: org.jboss.netty.handler.codec.http.HttpRequest): Add = ???
[error]   def responsePayload(u: Result): org.jboss.netty.handler.codec.http.HttpResponse = ???
[error] object AdditionServer extends App with Transformer[HttpRequest,Add,Result,HttpResponse]{
[error]        ^
[error] one error found
[error] (compile:compileIncremental) Compilation failed

据我所知，我正在使用正确的签名实现特征。

谁能指出这里可能出了什么问题。

谢谢

Answer 1

AdditionServer 是扩展 Transformer 的对象。在你的代码中，这个对象既没有定义 extractPayload 也没有定义 responsePayload 因此你得到了编译错误。

您应该将您的方法定义从 trait 伴随对象移动到 AdditionServer

object AdditionServer extends App with
Transformer[HttpRequest,Add,Result,HttpResponse] {

import Transformer._

def extractPayload(r:HttpRequest):Add = {
        val body = r.getContent
    val length = body.readableBytes()
    val bytes = new Array[Byte](length)
    body.getBytes(body.readerIndex(),bytes,0,length)
    val bodyStr = new String(bytes)
    parse(bodyStr).extract[Add]
}

def responsePayload(u:Result):HttpResponse = {   
    val result = u.result
    val response = Response(HttpVersion.HTTP_1_1,
            HttpResponseStatus.OK)
        response.setContentTypeJson()       
        response.setContentString(
          s"""
            {
            "result": $result
            }
           """)
        response.httpResponse
   }   
}

如果您希望在伴随对象中定义您的方法，您可以从 AdditionServer:

中引用它们

object Transformer{
  implicit object AddPayloadTransformer 
  extends Transformer[HttpRequest,Add,Result,HttpResponse]{
   implicit val formats = DefaultFormats

   def extractPayload(r:HttpRequest):Add = {
        val body = r.getContent
        val length = body.readableBytes()
        val bytes = new Array[Byte](length)
        body.getBytes(body.readerIndex(),bytes,0,length)
        val bodyStr = new String(bytes)
        parse(bodyStr).extract[Add]
    }

   def responsePayload(u:Result):HttpResponse = {   
        val result = u.result
        val response = Response(HttpVersion.HTTP_1_1,
            HttpResponseStatus.OK)
        response.setContentTypeJson()       
        response.setContentString(
          s"""
            {
            "result": $result
            }
           """)
        response.httpResponse
   }   
  }
}

object AdditionServer extends App with
Transformer[HttpRequest,Add,Result,HttpResponse]{

   def extractPayload(r:HttpRequest):Add = Transformer.extractPayload(r)

   def responsePayload(u:Result):HttpResponse = Transformer.responsePayload(u)

  ...
  ...

finagle 服务中未实现的特征

Traits not implemented in finagle service

scala

traits

typeclass

finagle