如何在Scala中将参数注入类/特征方法 [英] How to inject parameters into a class/trait method in Scala

问题描述

我在我的Play Scala(2.5x，2.11.11)应用程序中有一个代码，到目前为止该代码一直运行良好(它基于以下链接:

I have a code in my Play Scala (2.5x, 2.11.11) app which has been running just fine so far (it is based on the following link: https://fizzylogic.nl/2016/11/27/authorize-access-to-your-play-application-using-action-builders-and-action-functions/). But now I need to pass another class instance to ApplicationAuthorizationHandler class (NOTE: throughout my code I am using Guice DI for injecting parameters into class constructors).

当前代码:

class ApplicationAuthorizationHandler
   extends AuthorizationHandler {
...
}

trait AuthorizationHandler {
...
}

trait AuthorizationCheck {
   def authorizationHandler: AuthorizationHandler = new ApplicationAuthorizationHandler

   object AuthenticatedAction extends ActionBuilder[RequestWithPrincipal] {
      override def invokeBlock[A](request: Request[A], block: (RequestWithPrincipal[A]) => Future[Result]): Future[Result] = {
         def unauthorizedAction = authorizationHandler.unauthorized(RequestWithOptionalPrincipal(None, request))
         def authorizedAction(principal: Principal) = block(RequestWithPrincipal(principal, request))

         authorizationHandler.principal(request).fold(unauthorizedAction)(authorizedAction)
      }
  }
}

//Example controller using this trait AuthorizationCheck
class MyController @Inject() extends Controller with AuthorizationCheck {
    def myAction = AuthenticatedAction { implicit request =>
...
}

所需代码:

class ApplicationAuthorizationHandler @Inject() (userService: UserService)
   extends AuthorizationHandler {
   ...
   // userService is used here
}

但是由于ApplicationAuthorizationHandler的实例是在特征AuthorizationCheck中实例化的，所以无法将UserService实例注入其中.我与所有控制器都具有Mixin这个特质，因此除非有更好的方法(并且必须存在)，否则我希望保持相同的方式. 首先，有没有一种方法可以直接注入类/特征方法? 或者，有没有一种方法，我不实例化特性AuthorizationCheck中的ApplicationAuthorizationHandler并在运行时在控制器内部传递它? 还是其他方式?

But since the instance of ApplicationAuthorizationHandler is instantiated inside trait AuthorizationCheck I can't inject UserService instance into it. I am Mixin this trait with all controllers so would like to keep the same way unless there is a better way (and there must be). First, is there a way to inject directly into class/trait method ? Alternatively, is there a way where I don't instantiate ApplicationAuthorizationHandler in trait AuthorizationCheck and pass it during run-time inside the controller ? Or any other way ?

推荐答案

特质不需要提供实现，因此您可以使用以下内容:

A trait does not need to provide an implementation, so you can have something like:

trait AuthorizationHandler {
  ...
}

class ApplicationAuthorizationHandler extends AuthorizationHandler {
  ...
}

trait AuthorizationCheck {

  // just declaring that implementations needs to provide a 
  def authorizationHandler: AuthorizationHandler 

  object AuthenticatedAction extends ActionBuilder[RequestWithPrincipal] {
    override def invokeBlock[A](request: Request[A], block: (RequestWithPrincipal[A]) => Future[Result]): Future[Result] = {
      def unauthorizedAction = authorizationHandler.unauthorized(RequestWithOptionalPrincipal(None, request))
      def authorizedAction(principal: Principal) = block(RequestWithPrincipal(principal, request))

      authorizationHandler.principal(request).fold(unauthorizedAction)(authorizedAction)
    }
  }
}

// So, now this controller needs to provide a concrete implementation 
// of "authorizationHandler" as declared by "AuthorizationCheck".
// You can do it by injecting a "AuthorizationHandler" as a val with
// name authorizationHandler.
class MyController @Inject()(val authorizationHandler: AuthorizationHandler) extends Controller with AuthorizationCheck {

   def myAction = AuthenticatedAction { implicit request =>
     ...
   }
}

当然，您需要提供一个模块来将AuthorizationHandler绑定到ApplicationAuthorizationHandler:

And of course, you need to provide a module to bind AuthorizationHandler to ApplicationAuthorizationHandler:

import play.api.inject._

class AuthorizationHandlerModule extends SimpleModule(
  bind[AuthorizationHandler].to[ApplicationAuthorizationHandler]
)

当然，ApplicationAuthorizationHandler可以注入自己的依赖项.您可以在我们的文档中查看更多详细信息.

Of course, ApplicationAuthorizationHandler can have its own dependencies injected. You can see more details at our docs.

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