scala - Play : How to implement action composition

Question

给定以下 ActionBuilder 实现:

class SignedRequest[A](request: Request[A]) extends WrappedRequest[A](request) {}

object SignedAction extends ActionBuilder[SignedRequest] {

  def invokeBlock[A](request: Request[A], block: SignedRequest[A] => Future[SimpleResult]) = {
    block(new SignedRequest(request))
  }   
}     

class SecuredRequest[A](request: Request[A]) extends WrappedRequest[A](request) {}

object SecuredRequest extends ActionBuilder[SecuredRequest] {

  def invokeBlock[A](request: Request[A], block: SecuredRequest[A] => Future[SimpleResult]) = {
    block(new SecuredRequest(request))
  }   
}

如何组合它们？我尝试了以下...

object MyController extends Controller {

  def doSomething = SignedAction.async(parse.json) {
    SecuredAction.async(parse.json) { implicit request =>
      Future.successful(Ok)
  }}
}

...但我总是收到以下错误消息:

/home/j3d/test/controllers/MyController.scala:37: type mismatch;
[error]  found   : play.api.mvc.Action[play.api.libs.json.JsValue]
[error]  required: scala.concurrent.Future[play.api.mvc.SimpleResult]
[error]       SecuredAction.async(parse.json) {
                                              ^

我错过了什么吗？发送。

Answer 1

函数 async 需要一个 Future[SimpleResult]，但是嵌套的 SecuredAction.async 返回一个 Action 到顶部 SignedAction.async(请注意，在您的示例代码中，您省略了将请求声明为 class 并且 SignedAction 声明了两次)。

您可以将嵌套的 SecuredAction 的结果应用于 SignedAction 并将其应用于已签名的请求。

package controllers

import scala.concurrent.Future

import play.api._
import play.api.mvc._

case class SignedRequest[A](request: Request[A]) 
    extends WrappedRequest[A](request) {}

object SignedAction extends ActionBuilder[SignedRequest] {

  def invokeBlock[A](request: Request[A], 
    block: SignedRequest[A] => Future[Result]) = 
    block(new SignedRequest(request))

}     

case class SecuredRequest[A](request: Request[A]) 
    extends WrappedRequest[A](request) {}

object SecuredAction extends ActionBuilder[SecuredRequest] {

  def invokeBlock[A](request: Request[A], 
    block: SecuredRequest[A] => Future[Result]) = 
    block(new SecuredRequest(request))

}

object MyController extends Controller {
  def doSomething = SignedAction.async(parse.json) { signedReq =>
    SecuredAction.async(parse.json) { implicit securedReq =>
      Future.successful(Ok)
    } apply signedReq
  }
}

这样的 Action 组合也可以在没有 ActionBuilder 的情况下完成(这可能会导致一些额外的复杂性)。

package controllers

import scala.concurrent.Future

import play.api._
import play.api.mvc._

case class SignedRequest[A](request: Request[A])
case class SecuredRequest[A](request: Request[A]) 

object MyController extends Controller {
  def Signed[A](bodyParser: BodyParser[A])(signedBlock: SignedRequest[A] => Future[Result]): Action[A] = Action.async(bodyParser) { req => 
    signedBlock(SignedRequest(req)) 
  }

  def Secured[A](bodyParser: BodyParser[A])(securedBlock: SecuredRequest[A] => Future[Result]): Action[A] = Action.async(bodyParser) { req => 
    securedBlock(SecuredRequest(req)) 
  }

  def doSomething = Signed(parse.json) { signedReq =>
    Secured(parse.json) { implicit securedReq =>
      Future.successful(Ok)
    } apply signedReq.request
  }
}

也可以围绕Future[Result]进行组合:

package controllers

import scala.concurrent.Future

import play.api._
import play.api.mvc._
import play.api.libs.json.JsValue

case class SignedRequest[A](request: Request[A])
case class SecuredRequest[A](request: Request[A]) 

object MyController extends Controller {
  def Signed[A](signedBlock: SignedRequest[A] => Future[Result])(implicit req: Request[A]): Future[Result] = signedBlock(SignedRequest(req))

  def Secured[A](signedBlock: SecuredRequest[A] => Future[Result])(implicit req: Request[A]): Future[Result] = signedBlock(SecuredRequest(req))

  def doSomething = Action.async(parse.json) { implicit req =>
    Signed[JsValue] { signedReq =>
      Secured[JsValue] { securedReq => Future.successful(Ok) } 
    }
  }
}